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Background: The translation and cultural adaptation of psychometrically tested tools is an essential component of effective evaluation of the intended purpose. The English questionnaire had been designed to measure current status of physiotherapy practice in cancer rehabilitation. Aim: The aim of this study was to culturally adapt, including translation and preliminary validation of the questionnaire for the cancer patients. Materials and Methods: A custom-made, validated version of the English self-administered questionnaire consisting of 30 items was translated into Tamil, Kannada and Malayalam languages. The process of translation included recommended methodology, mandating forward translation, backward translation, reconciliation and pretesting steps, was followed. Tool validation included assessing content accuracy and clarity. Process involved 13 jurors for the translation and content validation and 30 cancer patients for the face validity. All subjects were asked to complete the translated versions of the questionnaire, which was previously validated. Analysis and Results: The psychometric properties of the three regional language versions of the questionnaire for cancer patients employed during rehabilitation were good. Cognitive debriefing showed the regional language versions to be clear, relevant and comprehensive. Conclusion: The translated and adapted versions are comparable with the original English instrument in terms of content and accuracy and it is suitable to assess the current physiotherapy practice pattern in cancer rehabilitation settings.

AimTo calibrate Ir-192 high dose rate (HDR) brachytherapy source using different calibration methods and to determine the accuracy and suitability of each method for routine calibrations.BackgroundThe source calibration is an essential part of the quality assurance programme for dosimetry of brachytherapy sources. The clinical use of brachytherapy source requires an independent measurement of the air kerma strength according to the recommendations of medical physics societies.Materials and methodsThe Ir-192 HDR brachytherapy source from Gammamed plus machine (Varian Medical Systems, Palo Alto, CA) was calibrated using three different procedures, one using the well-type ionization chamber, second by the in-air calibration method and third using solid water phantoms. The reference air kerma rate (RAKR) of the source was determined using Deutsche Gesellschaft fur Medizinische Physik (DGMP) recommendations.ResultsThe RAKR determined using different calibration methods are in good agreement with the manufacturer stated value. The mean percentage variations of 0.21, −0.94, −0.62 and 0.58 in RAKR values with respect to the manufacturer quoted values were observed with the well-type chamber, in-air calibration, cylindrical phantom and slab phantom measurements, respectively.ConclusionMeasurements with a well-type chamber are relatively simple to perform. For in-air measurements, the indigenously designed calibration jig provides an accurate positioning of the source and chamber with minimum scatter contribution. The slab phantom system has an advantage that no additional phantom and chamber are required other than those used for external beam therapy dosimetry. All the methods of calibration discussed in this study are effective to be used for routine calibration purposes.

Dosimetric changes caused by the positional uncertainty of centering a small electron cutout to the machine central axis (CAX) of the linear accelerator (linac) were investigated. Six circular cutouts with 4 cm diameter were made with their centres shifted off by 0, 2, 4, 6, 8 and 10 mm from the machine CAX. The 6 × 6 cm2electron applicator was used for the measurement. The percentage depth doses (PDDs) were measured at the Machine CAX and also with respect to cutout centre for 6, 9, 12, 16 and 20 MeV electron beams. The in-line and cross-line profiles were measured at the depth of maximum dose (R100). The relative output factor (ROF) was measured at the reference depth. All the measurements were made at nominal source to surface distance (100 cm SSD) as well as at extended SSDs (100, 102, 106 and110 cm). When the cutout centre was shifted away from the machine CAX for low energy beams the depth of 100% dose (R100), the depth of 90% dose (R90) and the depth of 80% dose (R80) had no significant change. For higher energies (>9 MeV) there was a reduction in these dosimetric parameters. The isodose coverage of the in-line and cross-line profile was reduced when the cutout centre was shifted away from the machine CAX. At extended SSDs the dosimetric changes are only because of geometric divergence of the beam and not by the positional uncertainty of the cutout. It is important for the radiation oncologist, dosimetrist, therapist and physicist to note such dosimetric changes while using the electron beam to the patients.

Rehabilitation in relation to cancer can be preventative, restorative, supportive, and palliative. It is recognized that patients may have rehabilitation needs throughout their care pathway. The role of physiotherapy in the cancer rehabilitation is less understood and particularly in the head and neck cancer (HNC) patients. This results in various residual deformities and dysfunctions for the patients with HNC. The objective of this review is to provide detailed information regarding the problems faced after the cancer treatments and rehabilitation of patients who suffered with HNC. The fact that cancer patients are facing several months of chemotherapy and/or radiotherapy and usually major surgery, as well as the direct effect of immobility due to pain, means that muscle wasting, joint stiffness, as well as de-conditioning and fatigue are inevitable. The absence of physiotherapy intervention would be detrimental to patient care and the ability of the patient/family to cope with the effects of the disease or its treatment on their functional capacity and quality of life. Following any treatment for HNC, physical therapy may play an essential role in preventing various complications and helping patients to mitigate impairments, and restoring function of the shoulder joint, neck, and face.

For intensity‐modulated radiation therapy, evaluation of the measured dose against the treatment planning calculated dose is essential in the context of patient‐specific quality assurance. The complexity of volumetric arc radiotherapy delivery attributed to its dynamic and synchronization nature require new methods and potentially new tools for the quality assurance of such techniques. In the present study, we evaluated and compared the dosimetric performance of EDR2 film and three other commercially available quality assurance devices: IBA I'MatriXX array, PTW Seven29 array and the Delta 4 array. The evaluation of these dosimetric systems was performed for RapidArc and IMRT deliveries using a Varian NovalisTX linear accelerator. The plans were generated using the Varian Eclipse treatment planning system. Our results showed that all four QA techniques yield equivalent results. All patient QAs passed our institutional clinical criteria of gamma index based on a 3% dose difference and 3 mm distance to agreement. In addition, the Bland‐Altman analysis was performed which showed that all the calculated gamma values of all three QA devices were within 5% from those of the film. The results showed that the four QA systems used in this patient‐specific IMRT QA analysis are equivalent. We concluded that the dosimetric systems under investigation can be used interchangeably for routine patient specific QA. PACS numbers: 87.55.Qr, 87.56.Fc

Physical characteristics of photon beam from a CLINAC-DBX single energy accelerator Commissioning beam data are treated as a reference and ultimately used by treatment planning systems, therefore, it is vitally important that the collected data are of the highest quality, in order to avoid dosimetric and patient treatment errors that may subsequently lead to a poor radiation outcome. High-energy photon and electron beams from different accelerators of the same nominal energy may have different dosimetric characteristics due to differences in target and flattening filter materials, accelerator guide and collimator designs. In the present study, clinically pertinent data for the available photon energy were investigated. For making measurements in water, first time in India, a three dimensional radiation field analyzer RFA (CRS- Scan -O-Plan) was used. For absolute dosimetry and other measurements like relative output factors, wedge factors etc., a DOSE1 electrometer (Scanditronix Wellhofer) in a white polystyrene was employed. All the measured data were utilized as an input to the ECLIPSE treatment planning system for further clinical use.

The goal of the present study was to study the effects of low- and high-energy intensity-modulated photon beams on the planning of target volume and the critical organs in cases of localized prostate tumors in a cohort of 8 patients. To ensure that the difference between the plans is due to energy alone, all other parameters were kept constant. A mean dose volume histogram (DVH) for each value of energy and for each contoured structure was created and was considered as completely representative for all patients. To facilitate comparison between 6-MV and 15-MV beams, the DVH-s were normalized. The different parameters that were compared for 6-MV and 15-MV beams included mean DVH, different homogeneity indices, conformity index, etc. Analysis of several indices depicts more homogeneous dose for 15-MV beam and more conformity for 6-MV beam. Comparison of all these parameters showed that there was little difference between the 6-MV and 15-MV beams. For rectum, 2 to 4 % more volume received high dose with the 6-MV beam in comparison with the 15-MV beam, which was not clinically significant, since in practice much tighter constraints are maintained, such that Normal Tissue Complication Probability (NTCP) is kept within 5 %. Such tighter constraints might increase the dose to other regions and other critical organs but are unlikely to increase their complication probabilities. Hence the slight advantages of 15-MV beam in providing benefits of better normal-tissue sparing and better coverage cannot be considered to outweigh its well-known risk of non-negligible neutron production.

The complexity of VMAT delivery requires new methods and potentially new tools for the commissioning of these systems. It appears that great consideration is needed for quality assurance (QA) of these treatments since there are limited devices that are dedicated to the QA of rotational delivery. In this present study, we have evaluated the consistency and reproducibility of one prostate and one lung VMAT plans for 31 consecutive days using three different approaches: 1) MLC DynaLog files, 2) in vivo measurements using the multiwire ionization chamber DAVID, and 3) using PTWseven29 2D ARRAY with the OCTAVIUS phantom at our Varian Clinac linear accelerator. Overall, the three methods of testing the reproducibility and consistency of the VMAT delivery were in agreement with each other. All methods showed minimal daily deviations that contributed to clinically insignificant dose variations from day to day. Based on our results, we conclude that the VMAT delivery using a Varian 2100CD linear accelerator equipped with 120 MLC is highly reproducible. PACS numbers: 87.55.Qr and 87.56.Fc

Background Intensity modulated radiotherapy (IMRT) is being used to treat carcinoma of cervix (Ca Cx). Integral dose to normal tissue and increased leakage are the concern about IMRT. 6 MV photon beam is a good choice of energy for Ca Cx IMRT treatment. Aim The objective of this study was to compare intensity modulated radiotherapy (IMRT) plans generated by 6 MV and 15 MV photon energies for carcinoma of cervix (Ca Cx) with regards to dosimetric parameters of planning target volume (PTV) and organs at risk (OAR), homogeneity index (HI), conformity index at 98% level (CI 98%), integral dose to normal tissue (NTID) and total number of monitor units (MUs). Material and methods A cohort of 16 patients was selected for this study. All patients were to receive a dose of 50 Gy in 25 fractions. IMRT plans were generated for both energies using same dose–volume constraints. Results Our results show a comparable coverage of planning target volume (PTV) for both energies. Volume of PTV receiving a prescription dose is 97.8 ± 0.5% and 98.8 ± 0.4% for the 6 MV and the 15 MV plans. Volume of PTV receiving a dose of 107% is 4.4 ± 7.8% and 16.1 ± 22.2%. Bladder and rectum mean doses for the 6 MV and the 15 MV photon plans were 39.8 ± 3.0 Gy and 40.0 ± 3.2 Gy, and 35.8 ± 3.1 Gy and 36.0 ± 3.1 Gy, respectively. Homogeneity index (HI) for both energies was 1.04. The conformity indices at 98% isodose (CI 98%) were 1.3 ± 0.1 and 1.4 ± 0.1 for 6 MV and 15 MV photon plans, respectively. Conclusions We conclude that a 6 MV photon is a good choice for Ca Cx IMRT as it produces a highly conformal, homogeneous plan with superior target coverage and better OAR sparing.

HDR brachytherapy treatment planning often involves optimization methods to calculate the dwell times and dwell positions of the radioactive source along specified afterloading catheters. The purpose of this study is to compare the dose distribution obtained with geometric optimization (GO) and volume optimization (VO) combined with isodose reshaping. This is a retrospective study of 10 cervix HDR interstitial brachytherapy implants planned using geometric optimization and treated with a dose of 6 Gy per fraction. Four treatment optimization plans were compared: geometric optimization (GO), volume optimization (VO), geometric optimization followed by isodose reshape (GO_IsoR), and volume optimization followed by isodose reshape (VO_IsoR). Dose volume histogram (DVH) was analyzed and the four plans were evaluated based on the dosimetric parameters: target coverage (V100), conformal index (COIN), homogeneity index (HI), dose nonuniformity ratio (DNR) and natural dose ratio (NDR). Good target coverage by the prescription dose was achieved with GO_IsoR (mean V100 of 88.11%), with 150% and 200% of the target volume receiving 32.0% and 10.4% of prescription dose, respectively. Slightly lower target coverage was achieved with VO_IsoR plans (mean V100 of 86.11%) with a significant reduction in the tumor volume receiving high dose (mean V150 of 28.29% and mean V200 of 7.3%). Conformity and homogeneity were good with VO_IsoR (mean COIN=0.75 and mean HI=0.58) as compared to the other optimization techniques. VO_IsoR plans are superior in sparing the normal structures while also providing better conformity and homogeneity to the target. Clinically acceptable plans can be obtained by isodose reshaping provided the isodose lines are dragged carefully. PACS number: 87.53 Bn

Intensity‐modulated radiotherapy treatment demands stringent quality assurance and accurate dose determination for delivery of highly conformal dose to the patients. Generally 3D dose distributions obtained from a treatment planning system have to be verified by dosimetric methods. Mainly, a comparison of two‐dimensional calculated and measured data in several coplanar planes is performed. In principle, there are many possibilities to measure two‐dimensional dose distributions such as films, flat‐panel electronic portal imaging devices (EPID), ion chambers and ionization chamber arrays, and radiographic and radiochromic films. The flat‐panel EPIDs show a good resolution and offer a possibility for real‐time measurements: however to convert the signal into dose, a separate commercial algorithm is required. The 2D ion chamber array system offers the real‐time measurements. In this study, dosimetric characteristics of 2D ion chamber array matrix were analyzed for verification of radiotherapy treatments. The dose linearity and dose rate effect of the I'matriXX device was studied using 6 MV, 18 MV photons and 12 MeV electrons. The output factor was estimated using I'matriXX device and compared with ion chamber measurements. The ion chamber array system was found to be linear in the dose range of 2–500 cGy and the response of the detector was found to be independent of dose rate between 100 MU/min to 600 MU/min. The estimated relative output factor with I'matriXX was found to match very well with the ion chamber measurements. To check the final dose delivered during IMRT planning, dose distribution patterns such as field‐in‐field, pyramidal, and chair tests were generated with the treatment planning system (TPS) and the same was executed in the accelerator and measured with the I'matriXX device. The dose distribution pattern measured by the matrix device for field‐in‐field, pyramidal, and chair test were found to be in good agreement with the calculated dose distribution by TPS both for 6 and 18 MV photons (γ ≤ 1: 96%, criteria 3%, 3 mm). Two 7‐field IMRT plans (one prostate, one head and neck) dose distribution patterns were also measured with I'matriXX device and compared with film dosimetry. The measurements and evaluation proves that I'matriXX can be used for quantifying absolute dose. Moreover, using I'matriXX as absolute dosimeter in IMRT field verification, avoids the time‐consuming procedure of making ionometric measurement for absolute dose estimation and film for dose distribution verification. The I'matriXX can also used for routine quality assurance checks like flatness, symmetry, field width, and penumbra of the linear accelerator beam. PACS number: 87.55.ne and 87.56.Fc

BACKGROUND AND AIM: Cancer is a major cause of adult deaths in India and cancer incidence is projected to grow in the coming decades because of improved life expectancy. The importance of rehabilitation in cancer care received increasing recognition in medical settings; however, very little has been documented about the involvement of physiotherapists in cancer care and rehabilitation. This exploratory paper assesses the availability of physical therapy services for cancer patients and cancer survivors in South India. METHODOLOGY: In this explorative study, 1410 cancer patients from 15 cancer centers in three South Indian states were administered a valid questionnaire presented in their native languages. Descriptive statistics were used to analyze their responses. RESULTS: More than half of the cancer patients (54.1%) did not know that physiotherapy treatment is required in symptom management and only one-third (31%) were advised or referred to physiotherapy treatment. Two-thirds of the respondents (68.8%) were benefited by the recommended exercises. The recommended exercises were stretching (42.9%), breathing (28.6%), and strengthening (16.9%). The most commonly used evaluation method was visual analog scale for pain (29.9%). CONCLUSION: It is found that the number of qualified physiotherapists working in the cancer centers is not sufficient to meet the demand.

Background: The evaluation of the agreement between measured and calculated dose plays an essential role in the quality assurance (QA) procedures of intensity-modulated radiation therapy (IMRT). Aim: The purpose of this study is to compare performances of the two dosimetric systems (EDR2 and I′matriXX) in the verification of the dose distributions calculated by the TPS for brain and head and neck dynamic IMRT cases. Materials and Methods: The comparison of cumulative fluence by using Kodak extended dose rate (EDR2) and I′matriXX detectors has been done for the evaluation of 10 brain, 10 head and neck IMRT cases treated with 6 MV beams. The parameter used to assess the quality of dose calculation is the gamma-index (g -index) method. The acceptance limits for g calculation we have used are 3% and 3 mm respectively for dose agreement and distance to agreement parameters. Statistical analyses were performed by using the paired, two-tailed Student t-test, and P< 0.01 is kept as a threshold for the significance level. Results: The qualitative dose distribution comparison was performed using composite dose distribution in the measurement plane and profiles along various axes for TPS vs. EDR2 film and TPS Vs I′matriXX. The quantitative analysis between the calculated and measured dose distribution was evaluated using DTA and g-index. The percentage of pixels matching with the set DTA and g values are comparable for both with EDR2 film and I′matriXX array detectors. Statistically there was no significant variation observed between EDR2 film and I′matriXX in terms of the mean percentage of pixel passing g for brain cases (98.77 ± 1.03 vs 97.62 ± 1.66, P = 0.0218) and for head and neck cases (97.39 ± 2.13 vs 97.17 ± 1.52%, P = 0.7404). Conclusion: Due to simplicity and fast evaluation process of array detectors, it can be routinely used in busy departments without compromising the measurement accuracy.

A novel technique to evaluate the geometrical accuracy of CT-MR image fusion in Gamma Knife radiosurgery procedures In order to optimize the accuracy of imaging in Gamma Knife radiosurgery using the image fusion options available in the Leksell gamma plan. Phantom images from 1.5 Tesla MRI Scan (Magnetom vision - Siemens) and Computed Tomography images from Philips Brilliance 16 CT scanner were used for image fusion in Gammaplan treatment planning system. The images were fused using co-registration technique using multiview and imagemerge modules. Stereotactic coordinates were then calculated for known targets. Vector distances from the centre of the Leksell coordinate system to five known targets were measured in CT, MR and CT-MR fused images and compared with geometrical measurements. The mean values of maximum absolute errors were 0.34 mm, 0.41 mm.0.38 mm (along x-axis), 0.43 mm, 1.53 mm, 0.62 mm (along y-axis) and 0.75 mm 2.02 mm, 0.93 mm (along z-axis) for CT, MR and CT-MR fused image data respectively. The mean error in calculating the vector distances from the center of the Leksell coordinate system (100, 100, 100) to the known target volumes are 0.22 mm, 0.8 mm and 0.43 mm for CT, MR and CT-MR fused images, respectively. Image fusion functions available in gamma plan are useful for combining the features of CT and MR imaging modalities. These methods are highly useful in clinical situations where the error associated with Magnetic Resonance Imaging is beyond acceptable levels.

Mobile phones and sleep - A review The increasing use of mobile phones has raised concerns regarding the potential health effects of exposure to the radiofrequency electromagnetic fields. An increasing amount research related to mobile phone use has focussed on the possible effects of mobile phone exposure on human brain activity and function. In particular, the use of sleep research has become a more widely used technique for assessing the possible effects of mobile phones on human health and wellbeing especially in the investigation of potential changes in sleep architecture resulting from mobile phone use. Acute exposure to a mobile phone prior to sleep significantly enhances electroencephalogram spectral power in the sleep spindle frequency range. This mobile phone-induced enhancement in spectral power is largely transitory and does not linger throughout the night. Furthermore, a reduction in rapid eye movement sleep latency following mobile phone exposure was also found, although interestingly, neither this change in rapid eye movement sleep latency or the enhancement in spectral power following mobile phone exposure, led to changes in the overall quality of sleep. In conclusion, a short exposure to the radiofrequency electromagnetic fields emitted by a mobile phone handset immediately prior to sleep is sufficient to induce changes in brain activity in the initial part of sleep. The consequences or functional significance of this effect are currently unknown and it would be premature to draw conclusions about possible health consequences.

Electronic portal imaging devices (EPIDs) are extensively used for obtaining dosimetric information of pre-treatment field verification and in-vivo dosimetry for intensity-modulated radiotherapy (IMRT). In the present study, we have implemented the newly developed portal dosimetry software using independent dose prediction algorithm EPIDose TM and evaluated this new tool for the pre-treatment IMRT plan quality assurance of Whole Pelvis with Simultaneous Integrated Boost (WP-SIB-IMRT ) of prostate cases by comparing with routine two-dimensional (2D) array detector system (MapCHECK TM ). We have investigated 104 split fields using g-distributions in terms of predefined g frequency parameters. The mean γ values are found to be 0.42 (SD: 0.06) and 0.44 (SD: 0.06) for the EPIDose and MapCHECK TM , respectively. The average g∆ for EPIDose and MapCHECK TM are found as 0.51 (SD: 0.06) and 0.53 (SD: 0.07), respectively. Furthermore, the percentage of points with g < 1, γ < 1.5, and γ > 2 are 97.4%, 99.3%, and 0.56%, respectively for EPIDose and 96.4%, 99.0% and 0.62% for MapCHECK TM . Based on our results obtained with EPIDose and strong agreement with MapCHECK TM , we may conclude that the EPIDose portal dosimetry system has been successfully implemented and validated with our routine 2D array detector

Electron beam therapy is widely used in the management of cancers. The rapid dose fall-off and the short range of an electron beam enable the treatment of lesions close to the surface, while sparing the underlying tissues. In an extended source-to-surface (SSD) treatment with irregular field sizes defined by cerrobend cutouts, underdosage of the lateral tissue may occur due to reduced beam flatness and uniformity. To study the changes in the beam characteristics, the depth dose, beam profile, and isodose distributions were measured at different SSDs for regular 10 Χ 10 cm 2 and 15 Χ 15 cm 2 cone, and for irregular cutouts of field size 6.5 Χ 9 cm 2 and 11.5 Χ 15 cm 2 for beam energies ranging from 6 to 20 MeV. The PDD, beam flatness, symmetry and uniformity index were compared. For lower energy (6 MeV), there was no change in the depth of maximum dose (R100) as SSD increased, but for higher energy (20 MeV), the R100 depth increased from 2 cm to 3 cm as SSD increased. This shows that as SSD increases there is an increase in the depth of the maximum dose for higher energy beams. There is a +7 mm shift in the R100 depth when compared with regular and irregular field sizes. The symmetry was found to be within limits for all the field sizes as the treatment distance extended as per International Electro technical Commision (IEC) protocol. There was a loss of beam flatness for irregular fields and it was more pronounced for lower energies as compared with higher energies, so that the clinically useful isodose level (80% and 90%) width decreases with increase in SSD. This suggests that target coverage at extended SSD with irregular cut-outs may be inadequate unless relatively large fields are used.

The radiotherapy community has in the past few decades witnessed dramatic shift in the treatment modalities from conventional 2-D radiotherapy to the now widely practiced 3-DCRT, IMRT and evolving IGRT. IMRT has generated so much interest because of its unique dosimetric modulation to concentrate doses to the targets of interests while also being able to relatively spare neighboring normal tissue. However IMRT is not the all in one solution for radiotherapeutic management of solid malignancies. The current enthusiasm in IMRT most be tempered with an understanding of the complexities of IMRT planning, treatment delivery, quality assurance, monitoring and clinical limitations. The widespread implementation of this technological innovation may have been a bit premature considering that clinical information regarding the same is still being generated. This article tries to give an overview of the potential advantages/disadvantages of IMRT in the clinical set up and the few controversies (Grey Zone) that are still being resolved. There is evidence to indicate that indiscriminately used IMRT may even harm the patient or have an inferior therapeutic index to 3DCRT. This and other pertinent issues will be covered by the authors in this short review of IMRT in clinical practice.

Ir-192 source is widely used in high dose rate brachytherapy. The aim of this study was to derive the brachytherapy dosimetric functions described in AAPM TG-43 to characterize the dosimetric properties of commercially available microselectron HDR Ir-192 source. All the measurements were carried out with GAFCHROMIC EBT radiochromic film in water equivalent solid phantom and the grey values were analyzed using Omnipro IMRT film dosimetry software with Vidar VXR-16 scanner. Optical density of the film was converted to dose using calibration film established in this study. Measurements were carried out by measuring the dose at radial distances from 0.5 cm to 5.0 cm with interval of 0.5 cm and at polar angle 0°–180° in 10° intervals. Dosimetric functions such as dose rate constant, radial dose functions and anisotropy of the dose distribution were found to be in good agreement with Monte Carlo calculations. This study confirms the feasibility of radiochromic EBT film dosimetry in characterization of the TG-43 parameters for Ir-192 HDR source.

Endometrial carcinoma is the most common malignancy arising in the female genital tract. Intracavitary vaginal cuff irradiation may be given alone or with external beam irradiation in patients determined to be at risk for locoregional recurrence. Vaginal cylinders are often used to deliver a brachytherapy dose to the vaginal apex and upper vagina or the entire vaginal surface in the management of postoperative endometrial cancer or cervical cancer. The dose distributions of HDR vaginal cylinders must be evaluated carefully, so that clinical experiences with LDR techniques can be used in guiding optimal use of HDR techniques. The aim of this study was to optimize dose distribution for Gammamed plus vaginal cylinders. Placement of dose optimization points was evaluated for its effect on optimized dose distributions. Two different dose optimization point models were used in this study, namely non-apex (dose optimization points only on periphery of cylinder) and apex (dose optimization points on periphery and along the curvature including the apex points). Thirteen dwell positions were used for the HDR dosimetry to obtain a 6-cm active length. Thus 13 optimization points were available at the periphery of the cylinder. The coordinates of the points along the curvature depended on the cylinder diameters and were chosen for each cylinder so that four points were distributed evenly in the curvature portion of the cylinder. Diameter of vaginal cylinders varied from 2.0 to 4.0 cm. Iterative optimization routine was utilized for all optimizations. The effects of various optimization routines (iterative, geometric, equal times) was studied for the 3.0-cm diameter vaginal cylinder. The effect of source travel step size on the optimized dose distributions for vaginal cylinders was also evaluated. All optimizations in this study were carried for dose of 6 Gy at dose optimization points. For both non-apex and apex models of vaginal cylinders, doses for apex point and three dome points were higher for the apex model compared with the non-apex model. Mean doses to the optimization points for both the cylinder models and all the cylinder diameters were 6 Gy, matching with the prescription dose of 6 Gy. Iterative optimization routine resulted in the highest dose to apex point and dome points. The mean dose for optimization point was 6.01 Gy for iterative optimization and was much higher than 5.74 Gy for geometric and equal times routines. Step size of 1 cm gave the highest dose to the apex point. This step size was superior in terms of mean dose to optimization points. Selection of dose optimization points for the derivation of optimized dose distributions for vaginal cylinders affects the dose distributions.

Mobile phones and hearing - A review Mobile phones are being widely used throughout the world. Although there is no clear evidence of harmful effects of radiofrequency (RF) radiation at the levels used by these devices, there is widespread public concern that there may be potential for harm. Of all anatomical structures, the ear is closest to the mobile phone, which may lead to relatively high energy deposition in the ear compared to other parts of the body. Till the year 2000 only a few studies had addressed potential adverse effects of EMFs on the hearing system. The potential adverse effects of mobile phone exposure on the hearing system should be investigated, because mobile phones are usually held close to the ear. Until now, most studies have assessed the influence of RF radiation on the central or peripheral auditory system. However, clear conclusions cannot be drawn from these studies regarding the presence or absence of effects because of the limitations in the audiological and/or dosimetric approaches and limited sample sizes. results. Although the presence of possible effects on hearing threshold levels cannot be dismissed entirely, the evidence available is not sufficiently strong to conclude that there are adverse effects. A replication study with a shift in hearing threshold levels at high frequencies as the a priori hypothesis is desirable to resolve this issue.

Electron beam characteristics at extended source to surface distance for a Clinac-DHX linear accelerator A uniform dose to the target site is required with a knowledge of delivered dose, central axis depth dose and beam flatness for successful electron treatment at an extended source to surface distance (SSD). In an extended SSD treatment under dosage of the lateral tissue may occur due to reduced beam flatness. To study the changes in beam characteristics, the depth dose curves, beam flatness and isodose distributions were measured at different SSDs from 100 to 120 cm for clinically used field sizes from (4×4) to (25×25) cm2 and beam energies ranging from 6 MeV to 20 MeV. Our results suggest that the change in depth dose is minimal except in the buildup region for most energy. In general surface dose is decreased as the SSD increased moderately. It was observed that the loss in beam flatness is significant for smaller fields, higher isodose lines, and lower energies. The penumbra enlarged and the uniformity index reduced with increasing SSD.

Quality assurance and dosimetric analysis of intensity modulation radiotherapy using compensators for head and neck cancers In this study we describe our experience in implementing compensator based intensity modulated radiotherapy (cIMRT) for head and neck cancer with regard to pre treatment quality assurance (QA), dosimetric parameters and other technical detail. This study represents the analysis of initial 48 patients who underwent cIMRT for head and neck cancers. All patients were treated with pre treatment QA in terms of point dose with ion chamber and spatial dose comparison with film dosimetry. In our study for all 48 patients, compensators revealed a deviation in central axis dose of 2% ± 1.8% in terms of cumulative calculated versus measured dose. Target coverage for high dose volume (70 Gy) was adequate in terms of volume receiving 93% and 95% of the prescription dose, which was 98.5% and 97.5% respectively. Parotid and other critical organs were spared adequately. Contralateral parotid (CLP) was spared. V30 Gy and V35 Gy was 55.9% and 36.8% for CLP and average dose was 31.7 Gy. Median variation in cumulative measured dose versus cumulative calculated dose was 1.8% (SD + 1.8) and mean variation was 2.5% (95%CI 1.5, 2.6). Range was 0 to 7%. cIMRT is practically feasible. Our QA tests revealed high degree of concordance between cumulative measured doses versus cumulative calculated doses. All dosimetric parameters were within acceptable limits. The manufacturing of compensator is cumbersome but it is a one time job followed by easy treatment delivery and simple QA procedure, high monitor unit (MU) efficiency and less treatment time. cIMRT is easy to implement and now can be applied to larger number of patients with different type of tumor.

Summary Background Intensity-modulated radiation therapy (IMRT) has been widely used for prostate cancer treatments. 6MV photon beams were found to be an effective energy choice for most IMRT cases. The use of high-energy photons raise concerns about increased leakage and secondary neutron dose for the patients. Aim In this work, the effect of beam energy on the quality of IMRT plans for prostate radiotherapy was systematically studied for competing IMRT plans optimized for delivery with either 6 or 10MV beams. Materials and Methods A cohort of 20 prostate cases was selected for this study. All patients received full-course IMRT treatments to a dose of 79.2Gy to PTV in 44 fractions. For all of the cases we developed treatment plans using 6 MV and 10MV intensity-modulated beams with identical dose volume constraints. Results Percentage of doses received by the percentage volume of PTV was higher for 6MV photons compared to 10MV photons for 12 patients, less than or equal to 1% for 6 patients and 2.6%, 3.6% for the remaining 2 patients irrespective of the PTV volume. Percentage doses received by 15% of bladder volume were higher for 10 MV photons. Percentage doses received by 15% of rectum volume were also higher for 10 MV photons. Conclusions Since there is no greater advantage from 10MV photons as compared with 6MV photons in large volume pelvic IMRT dosimetry and also 10MV photons lie on the threshold energy border for the induction of photo neutrons from the accelerator components, we recommend the use of 6MV photons for IMRT of prostate cancer to achieve better results in tumour control and acceptable probability of complication rate.

External beam radiotherapy for palliation of painful bone metastases: pooled data bioeffect dose response analysis of dose fractionation Bone metastases develop in up to 70% of newly diagnosed cancer patients and result in immobility, anxiety, and depression, severely diminishing the patients quality of life. Radiotherapy is a frequently used modality for bone metastasis and has been shown to be effective in reducing metastatic bone pain and in some instances, causing tumor shrinkage or growth inhibition. There is controversy surrounding the optimal fractionation schedule and total dose of external beam radiotherapy, despite many randomized trials and overviews addressing the issue. This study was undertaken to apply BED to clinical fractionation data of radiotherapeutic management of bone metastases in order to arrive at optimum BED values for acceptable level of response rate. A computerised literature search was conducted to identify all prospective clinical studies that addressed the issue of fractionation for the treatment of bone metastasis. The results of these studies were pooled together to form the database for the analysis. A total of 4111 number of patients received radiation dose ranging from 4 to 40.5 Gy in 1 to 15 fractions with dose per fraction ranging from 2 to 10 Gy. Single fraction treatments were delivered in 2013 patients and the dose varied from 4 to 10 Gy. Multifraction treatments were delivered in 2098 patients and the dose varied from 15 to 40.5 Gy. The biological effective dose (BED) was evaluated for each fractionation schedule using the linear quadratic model and an α/β value of 10 Gy. Response rate increased significantly beyond a BED value of 14.4 Gy (p < 0.01). Based on our analysis and indications from the literature about higher retreatment and fracture rate of single fraction treatments, minimum BED value of 14.4 Gy is recommended.

SUMMARY Metastatic spinal cord compression, a term normally including compression of the spinal cord or nerve roots running within the spinal canal, is a common complication of systemic cancer, occurring in 5–10% of all patients with cancer. Recent published data on treatment of metastatic spinal cord compression (MSCC) have shown that radiotherapy (RT) alone is an effective approach for the majority of cases. Except for some protocols, the use of conventional RT (daily fractions of 2 Gy to a total dose of 30–40 Gy) has been abandoned in favour of radiation treatment regimens requiring a smaller number of fractions. In some published trials, 4–5 Gy daily for 8 days followed by 4 days rest, and then 5–16 daily doses of 2–3 Gy have been given with both good results and tolerance. Higher daily fractions ranging from 6 to 10 Gy have also been explored with similar results. We have summarized the studies comparing the treatments and clinical outcome. Most patients with MSCC have a life expectancy of only several months. In these patients one radiotherapeutic schedule with a short overall treatment time would be the best option, if its effect on the most relevant clinical symptoms, pain and motor dysfunction, is comparable to the effect of more protracted schedules. In patients with a reduced life expectancy, a radiotherapeutic effect on recalcifi cation, which can be expected only several months after RT, is of minor importance. In patients with a life expectancy of more than a few months, recalcifi cation becomes more of an issue and a more fractionated radiation schedule should be considered.

Dosimetric investigation of dual energy photon beams with assymmetric collimator jaws Many modern linear accelerators are equipped with asymmetric collimators or jaws that can be moved independently. Asymmetric jaws have got many clinical applications in radiation therapy. In the present study, the dosimetric characteristics of asymmetric collimators from our linear accelerator with 6 and 18 MV X-rays were carried out. The field size factors (FSF) and half value layer (HVL) were measured in a water phantom using 0.6 cc Farmer chamber for symmetric and asymmetric fields for both 6 and 18 MV X-rays. Measurements of beam penumbra, percentage depth dose (PDD), cross beam profiles and calculated isodose curves were measured by RFA 300 for both asymmetric and symmetric fields. The FSF were found to agree with in 3% for symmetric and asymmetric fields. The HVL in water was found to be 15.8 cm and 14.4 cm for 6 MV photons and 26 cm and 22.9 cm for 18 MV photons at the central axis and at 20 cm off the central axis. At 30 cm depth the percentage depth dose for symmetric and asymmetric fields were found to differ as high as 6% for 6 MV and 4% for 18 MV fields. No observable difference in penumbra was noticed for symmetric and asymmetric fields of same dimensions. The constrictions of isodose curves at the edge nearer to central axis were noticed for asymmetrically placed fields. The observed differences could be due to the passage of primary beam through differential thickness of the flattening filter which alters the beam quality.

Summary Aim The aim of this study is to evaluate the influence of high dose rate (HDR) brach-ytherapy source step size, source dwell position, dose prescription depth, dose specification points and optimization technique on dose distribution around Microselectron HDR brachytherapy vaginal cylinders and to evaluate the influence of distal dwell position and optimization technique on rectal and bladder dose of patients treated for vaginal cuff irradiation. Materials/Methods Orthogonal radiographs of vaginal cylinders of diameter 2.0, 2.5, 3.0 and 3.5cm form the basis of the study. Dose distribution using the PLATO brachytherapy treatment planning system (version 14.1) was generated. Two different HDR cylinder models, namely the non-curved dome model (NCDM) and curved dome model (CDM), were studied. To evaluate bladder and rectum dose in the patients NCDM was used. Results CDM gives more uniform dose distribution around the cylinder than NCDM. Dose prescription at 5mm depth from the surface results in very high dose to apex and dome as compared with the surface dose prescription. Dose prescription depth and dwell positions influence the length of prescription isodose. Optimization method and dwell positions affect the bladder and rectal dose of the studied patients. Conclusions Uniform dose distribution can be obtained for HDR vaginal cylinders by appropriately selecting dose specification points and optimization method. Dose distribution can be configured to provide a uniform dose on the surface, if the apex and curved surface of the cylinder are considered for dose specification and optimization. Appropriate HDR parameters are identified to minimize the dose to the apex of the vaginal cylinder, essential to reduce the dose to overlying small bowel and reduce the dose to rectum and bladder.

Comparision of beam data requirements for MLC commissioning on a TPS The treatment planning system (TPS) has become a key element in the radiotherapy process with the introduction of computer tomography (CT) based 3D conformal treatment planning. Commissioning of a MLC on a TPS either for conformal radiotherapy or intensity modulated radiation therapy (IMRT) requires beam data to be generated on a linear accelerator. Most of the TPS require these beam data to be generated with routine collimator jaws. However some TPS demand the data to be provided for MLC shaped fields. This prompted us to investigate whether beam data with jaws differ than that with MLC and whether the jaw based beam data would suffice for the commissioning of a MLC on a TPS. Beam data like percentage depth dose (PDD), cross beam profiles and output factors was acquired for jaws and MLC defined square fields for 6, 10 and 23 MV photon beams. Percentage depth dose and cross beam profiles were acquired with a radiation field analyzer RFA-200, CC13-S ion chambers with active volume of 0.13 cm3 and OmniPro-Accept software from Scanditronix-Wellhofer. A Medtec-TG51 water tank with Max-4000 electrometer and 0.6 cc PTW ionization chamber and a mini phantom from Standard Imaging was utilized for output measurements for millennium-120 MLC (Varian Medical Systems) and SRS diode detector (Scanditronix-Wellhofer) of 0.6 mm diameter of active area and 0.3 mm of active volume thickness for micro-MLC (BrainLab). The difference in PDD in the build-up region for millennium MLC was ±1.0% for 6 MV photons. For 10 MV photons the PDD difference was within ±4.0%. The difference in PDD for 23 MV photons ranged from 0% to 40.0%. PDD difference from build-up depth to about 28 cm was within ±1.0%. Difference in PDD crossed ±1.0% at 30 cm depth for 6 MV photons. The difference in PDD in the build-up region for mMLC was ±8.0% for 6 MV photons. For the smallest field size studied with micro-MLC i.e. 0.6 × 0.6 cm2 difference in PDD was more than ±1.0% in the build-up region and beyond a depth of 8.0 cm. The profiles for jaws and MLC agreed within the umbra region. However in the penumbra region small differences in doses were observed. The collimator scatter factor (Sc), phantom scatter factor (Sp) and output factor values for MLC were different that those for jaws. The differences in beam characteristics could have implication for intensity modulated radiation therapy and stereotactic radiosurgery in terms of dose in the build up region, exit dose, dose to the planning target volume (PTV) and organ at risk (OAR). Impact of these dosimetric differences between jaw and MLC needs to be further studied in terms of dose volume histograms for PTV and OAR and its further impact on tumor control probability (TCP) and normal tissue complication probability (NTCP).

X-ray computed tomography is one of the potential tool used to evaluate the polymer gel dosimeters in three dimensions. The purpose of this study is to investigate the factors which affect the image noise for X-ray CT polymer gel dosimetry. A cylindrical water filled phantom was imaged with single slice Siemens Somatom Emotion CT scanner. The imaging parameters like tube voltage, tube current, slice scan time, slice thickness and reconstruction algorithm were varied independently to study the dependence of noise on each other. Reductions of noise with number of images to be averaged and spatial uniformity of the image were also investigated. Normoxic polymer gel PAGAT was manufactured and irradiated using Siemens Primus linear accelerator. The radiation induced change in CT number was evaluated using X-ray CT scanner. From this study it is clear that image noise is reduced with increase in tube voltage, tube current, slice scan time, slice thickness and also reduced with increasing the number of images averaged. However to reduce the tube load and total scan time, it was concluded that tube voltage of 130 kV, tube current of 200 mA, scan time of 1.5 s, slice thickness of 3 mm for high dose gradient and 5 mm for low dose gradient were optimal scanning protocols for this scanner. Optimum number of images to be averaged was concluded to be 25 for X-ray CT polymer gel dosimetry. Choice of reconstruction algorithm was also critical. From the study it is also clear that CT number increase with imaging tube voltage and shows the energy dependency of polymer gel dosimeter. Hence for evaluation of polymer gel dosimeters with X-ray CT scanner needs the optimization of scanning protocols to reduce the image noise.

To evaluate the water equivalence and radiation transport properties of polymer gel dosimeters over the wide range of photon and electron energies 14 different types of polymer gels were considered. Their water equivalence was evaluated in terms of effective atomic number ( Z eff ), electron density ( ρ e ), photon mass attenuation coefficient ( μ / ρ ), photon mass energy absorption coefficient ( μ en / ρ ) and total stopping power ( S / ρ ) tot of electrons using the XCOM and the ESTAR database. The study showed that the effective atomic number of polymer gels were very close ( 1 % ) to that of water except PAGAT, MAGAT and NIPAM which had the variation of 3%, 2% and 3%, respectively. The value of μ / ρ and μ en / ρ for all polymer gels were in close agreement ( 1 % ) with that of water beyond 80 keV. The value of ( S / ρ ) tot of electrons in polymer gel dosimeters were within 1% agreement with that of water. From the study we conclude that at lower energy ( 80 keV ) the polymer gel dosimeters cannot be considered water equivalent and study has to be carried out before using the polymer gel for clinical application.

Summary Background The bioeffect of a physical dose depends on the nature of the tissue, fractionation scheme, dose rate and treatment time. Certainly, experienced radiotherapists are convinced of the existence of patient-to-patient variability in normal tissue response to radiotherapy for malignant tumours. The absorbed dose needs to be translated into a bioeffect dose, which takes into account treatment variables and the radiobiological characteristics of the relevant tissue. Various bioeffect models such as NSD, CRE, TDF and BED have been proposed to predict the biological effect of radiotherapy treatments. Aim This study was aimed at deriving tolerance bioeffect dose values for normal tissue complication rate. Materials/Methods Compiled clinical data of time dose fractionation schedules and incidence of erythema, desquamation and telangiectasia were used for the present analysis. Results For erythema and desquamation the radiation dose varied from 23.9 to 55.1Gy in 04 to 50 fractions (dose per fraction 1.1 to 7.3Gy) in 11 to 40 days. For telangiectasia (score ≥1 at 3 years) the radiation dose varied from 25.8 to 55.1Gy in 04 to 50 fractions (dose per fraction 1.1 to 7.3Gy) in 11 to 40 days. For telangiectasia (score ≥2 at 5 years) the radiation dose varied from 25.8 to 63.0Gy in 04 to 50 fractions (dose per fraction 1.1 to 7.3Gy) in 11 to 68 days. For telangiectasia (score ≥1, ≥2, ≥3, ≥4 at 10 years) the radiation dose varied from 25.8 to 63.0Gy in 04 to 35 fractions (dose per fraction 1.7 to 7.3Gy) in 22 to 68 days. TDF and LQF values for erythema, desquamation and telangiectasia were evaluated with α/β values of 7.5Gy, 11.2Gy and 2.8Gy respectively. TDF and LQF had a statistically significant correlation with probability of erythema, desquamation and telangiectasia (p Conclusions TDF and LQF values should be limited to 60 and 86Gy in order to limit the probability of telangiectasia.

Measurement of Transit Time of a Gammamed-Plus Remote Afterloading High Dose Rate Brachytherapy Source Accurate measurement of transit time of the HDR brachytherapy source of a remote after-loading unit is necessary to calculate the total radiation dose given to the treatment volume. Presently, most of the HDR brachytherapy treatment planning systems neglect the transit time in the computation of dose. The aim of this investigation is to use a well type ionization chamber to measure the transit time during the source movement between two dwell positions. As well type ionization chamber and a precision electrometer (manufacturer CD instruments, Bangalore) were used to measure the charge generated during the movement of the Ir-192 source of a Gammamed HDR brachytherapy unit with an interstitial needle. Effective transit time and effective speed were determined on the basis of methodology described by Sahoo [2]. Corrections were done on the basis of relative sensitivity values for varaious dwell position in the ionization chamber. In the present study the variation of effective speed with interdwell distance was minimal as compared with that of Sahoo [2]. The effective transit times were 0.129, 0.182, 0.301, 0.402, 0.701, and 0.993 seconds for 1, 2, 4, 6, 8 and 10 cm interdwell separations respectively. The effective transit times in the present study were higher than those of Sahoo [2]. Software modification accounting for the dynamic dose should be incorporated into all HDR planning systems. Such an improvement would enhance the safety and accuracy of HDR brachytherapy.

Summary Background New radiotherapy techniques such as stereotactic radiotherapy (SRT) stereotactic radiosurgery (SRS), three dimensional conformal radiotherapy (3DCRT) and intensity modulated radiation therapy (IMRT) aim to deliver a high dose to the tumour while sparing the surrounding normal healthy tissues. As a result of these complicated treatment techniques there is a need for a 3-dimensional (3D) dose verification system. However, currently available dosimeters such as ion chambers, diodes, thermoluminescent dosimeters and films are limited to point (or) planar measurement. Multiple measurements are required to obtain the 3-dimensional dose distribution using the above dosimeters. Hence volumetric measurements are not feasible without multiple detectors (or) multiple measurements. Gel dosimetry attempts to meet the requirements of 3D radiation dose distribution. Gel dosimetry is tissue equivalent [1] and it acts as a phantom as well as dosimeter so there is no need for dose perturbation correction. Aim Radiation-induced polymerization in polymer gel dosimeters gives rise to a change in CT number which can be measured with X-ray computed tomography (CT). The aim of this study is to assess the feasibility of using the X-ray CT scanner for the evaluation of dose distribution in polymer gel dosimetry. Materials/Methods Polymer gel called PAGAT ( P oly a crylamide G elatin a nd T etrakis hydroxymethyl phosphonium) consisting of 3.5% (w/w) BIS, 3.5% (w/w) acrylamide, 5% (w/w) gelatin, 10 mM Tetrakis hydroxymethyl phosphonium (THP) and 88% (w/w) water was manufactured in normal atmospheric conditions. The gel was irradiated using a Siemens Primus linear accelerator. The radiation-induced change in CT number was evaluated using a Siemens Somatom Emotion CT scanner. The percentage depth doses and profiles were deduced. The same study was carried out using radiation field analyzer RFA-200 with RK-ion chamber and film and compared with polymer gel measurements. Results Polymer gel dosimetry measurement was in agreement with ion chamber and film measurements except for a slight deviation in the build-up region. Discrepancies found were due to analysis of image without image averaging and background subtraction. Conclusions This preliminary study was conducted to evaluate the feasibility of using X-ray CT-based polymer gel dosimetry for clinical use. The results of this study encourage further use of X-ray CT in conjunction with polymer gel for 3D radiation dose measurements.

Purpose: To analyze backscattered dose enhancements near different metallic interfaces for cobalt-60 ( 6 0 Co) gamma rays and hand 18-MV photon beams. Material and Methods: Measurements were carried out with a PTW thin-window, parallel-plate ionization chamber and an RDM-1F electrometer. Thin sheets of aluminum, mild steel, copper, cadmium and lead were used as inhomogeneities. The chamber was positioned below the inhomogenities with the gantry maintained under the couch. Results: It can be noticed that the backscatter dose factor (BSDF) reaches the saturation value within few millimeters of all inhomogeneities and the thickness at which the saturation value is reached depends on the atomic number of the inhomogeneity. The amount of backscattered radiation was noticed to be greater with lesser-energy photons ( 6 0 Co) compared to the higher-energy photons. The BSDF varies across the beam when the inhomogeneity is present due to the change in beam quality. The backscattered electrons from lead inhomogeneity have a range in the order of 5-7 mm. Conclusion: Higher atomic number inhomogeneities result in an increase in BSDF, as they have higher scattering cross section for the secondary electrons. The increase in dose was noticed for few millimeters upstream from the metallic inhomogeneity, which suggests that the range of backscattered electrons is very small. Since the factors affecting the BSDF at the interface are energy-dependent, it is expected that the variation in BSDF will also be sensitive to the beam energy.

Re-irradiation tolerance of the spinal cord depends upon the volume of the spinal cord irradiated, the total dose, the dose per fractional, the elapsed time between the treatments and the region of the spinal cord involved. Clinical data on the retreatment tolerance of the spinal cord are sparse and inconclusive. Radiobiological laboratory evidence has indicated the presence of long term recovery of the spinal cord damage. Fractionation sensitivity during reirradiation is comparable with the first session of radiation treatment. After an initial dose of 45 Gy, 50% recovery has been reported by Schultheiss and Stephens for an elapsed period of two years for re-irradiation considerations.

Increased fractionation spares late reacting normal tissues more than acute reacting normal tissues. A linear quadratic model is valid from large dose per fraction down to dose per fraction of 2 Gy. Experimental studies on animals and clinical studies on the spinal cord tolerance have shown incidences of myelopathy at doses lower than 50 Gy. The α/β value of the linear quadratic model have been lower for low doses per fraction, indicating a sparing effect of altered fractionation for spinal cord myelitis. Animal data, clinical and radiobiological explanations suggest limitation of the radiobiological models. Further data suggest that one must not assume the spinal cord to have a greater tolerance at doses per fraction below the conventional dose per fraction of 2 Gy.

AimTo study the influence of segment width on plan quality for volumetric modulated arc based stereotactic body radiotherapy.BackgroundThe redundancy of modulation for regularly shaped small volume tumors results in creation of many small segments and an increase of monitor units, with a consequent prolongation of treatment and uncertainty in treatment delivery.Materials and methodsSix cases each in lung, abdomen and liver were taken for the study. For each case, three VMAT SBRT plans were generated with different penalties on minimum segment width of 0.5, 1.0 and 1.5cm. A comparison was made on the metrics of dose volume histogram, dosimetric indices, monitor units (MUs) and delivery accuracy.ResultsThe mean reduction of total MUs when compared with 0.5cm plan was observed as 12.7±6.0% and 17.5±7.2% for 1.0cm and 1.5cm of minimum segment width, respectively. The p value showed a significant degradation in dosimetric indices for 1.5cm plans when compared with 0.5cm and 1.0cm plans. The average deviation of measured dose with TPS calculated was 3.0±1.1%, 2.1±0.84% and 1.8±0.9% for 0.5, 1.0 and 1.5cm, respectively. The calculated gamma index with pass criteria of 2% dose difference and 2mm distance to agreement was 95.9±2.8%, 96.5±2.6% and 97.8±1.6% as calculated for 0.5, 1.0 and 1.5cm of penalties, respectively. In view of the trade off between delivery efficiency and plan quality, 1cm minimum segment width plans showed an improvement.ConclusionsVMAT SBRT plans with increased optimal value of minimum segment width showed better plan quality and delivery efficiency for stereotactic body radiotherapy.

Context: Possible benefits of inverse planning. Aims: To analyze possible benefits of inverse planning intensity modulated radiation therapy (IMRT) over field-in-field 3D conformal radiation therapy (FIF-3DCRT) and to evaluate the differences if any, between low (6 Million Volts) and high energy (15 Million Volts) IMRT plans. Materials and Methods: Ten patients with squamous cell carcinoma of oropharynx, previously treated with 6 MV step and shoot IMRT were studied. V 100 , V 33 , V 66 , mean dose and normal tissue complication probabilities (NTCP) were evaluated for parotid glands. Maximum dose and NTCP were the parameters for spinal cord. Statistical Analysis Used: A two-tailed t-test was applied to analyze statistical significance between the different techniques. Results: For combined parotid gland, a reduction of 4.374 Gy, 9.343 Gy and 7.883 Gy were achieved for D 100 , D 66 and D 33 , respectively in 6 MV-IMRT when compared with FIF-3DCRT. Spinal cord sparing was better in 6 MV-IMRT (40.963 ± 2.650), with an average reduction of maximum spinal cord dose by 7.355 Gy from that using the FIF-3DCRT technique. The uncomplicated tumor control probabilities values were higher in IMRT plans thus leading to a possibility of dose escalation. Conclusions: Though low-energy IMRT is the preferred choice for treatment of oropharyngeal cancers, FIF-3DCRT must be given due consideration as a second choice for its well established advantages over traditional conventioan technique.

The purpose of the study was to analyze the effects of the number of intensity levels on treatment planning outcome of static IMRT method with dynamic IMRT method and also to investigate the integral dose to non-target tissues in both the methods. The IMRT planning was carried out using Eclipse treatment planning system with millennium 120 multileaf collimator (Varian Clinac- 2100 DHX). Five cases each of head and neck, cervix and esophagus cancer were selected for this study. For each case, planning was carried out using both delivery methods. Further for the static IMRT, different numbers of intensity levels ranging from 5 to 20 were studied. The optimization values were kept common for both the techniques and only the leaf motion calculation was varied. The parameters associated with the Dose volume histograms were examined for a more quantitative comparison. The integral doses (0.5 Gy to 30 Gy) of Non-target tissues were also calculated for both techniques. Analyses were performed using a t test to determine difference in any of the parameters examined. For three sites studied, there were no significant changes observed between static IMRT (above 10 intensity levels) and dynamic IMRT method. However there were significant differences observed with 5 intensity level static IMRT plans compared to dynamic IMRT plans. There were no significant changes observed in normal tissue dose values between static IMRT plans and dynamic IMRT plans. The total number of monitor unit was more for dynamic IMRT plans compared to static IMRT plans for all three sites. The integral doses from 0.5 Gy to 30 Gy were analyzed and no significant changes were observed between static IMRT and dynamic IMRT plans.

Clinically pertinent data of the photon beams of nominal energy 6 MV and 18 MV from a dual photon energy linear accelerator are measured using a radiation field analyser with semiconductor diodes and ionisation chambers. Percentage depth dose values are compared with available data from other linacs and BJR-17. Measurements made in the buildup region using a parallel plate chamber show a marked increase in the surface dose and dmax shifts by 3 mm and 14 mm for 6 MV and 18 MV photons, respectively as the field size is increased from 4 x 4 cm2 to the maximum. Variations of wedge angles with energy and field size are also determined up to wedge widths of 15 cm for all the four available wedge angles. Isodose plots of both the energies are plotted using semiconductor diodes in a RFA-3 system. Output factors, wedge transmission factors, and shielding tray factors were also measured in clear polystyrene phantom for both the photon energies at the depths of maximum ionisation. Beam characteristics of the electron beams of energies 6, 9, 12, 16, and 20 MeV produced by the Clinac-1800 have also been studied. The characteristics include percentage depth dose, isodose distribution, depth of maximum dose, surface dose, photon contamination, uniformity index, and penumbra. Most of the measurements were carried out using semiconductor detectors, whereas small volume ionization chambers and a plane-parallel chamber were kept as standards for comparison. Isodose distributions were drawn from the film densitometry method. Range-energy parameters are obtained from the observed depth dose data. These parameters vary from machine to machine and must be ascertained for individual units. The parameters differ to a considerable extent from their theoretically predicted values but generally follow the trend, experimentally observed by others, for similar types of units.

Demonstration of the influence of intraluminal brachytherapy dose on complications in the treatment of esophageal carcinoma.Between January 1990 and June 1991, 75 patients with esophageal cancer were treated with external radiotherapy followed by intraluminal brachytherapy. Patients had a Karnofsky score of over 70, with no supra-clavicular nodal or distant disease. An external radiotherapy dose between 40 and 55 Gy (mean 52 Gy), 5 times a week, 2 to 2.06 Gy/fraction, followed by a single session of Intraluminal brachytherapy using a locally developed, manual, afterloading applicator with Cs-137 sources with dose ranges of 8-10 Gy (Group 1: 42 patients), 10-12 Gy (Group 2: 11 patients), and 12-15 Gy (Group 3: 22 patients) at a mean dose rate of 2.09 Gy/hr was delivered.The actuarial figures at 1 year were 39% for overall survival, 29% for disease-free survival, and 38% for local control. Fourteen patients (18.6%) developed complications of either an esophageal stricture or fistula. These were dependent on intra-luminal brachytherapy dose, whereas external radiotherapy and intra-luminal brachytherapy doses did not contribute significantly to local control. For Groups 1, 2, and 3, actuarial local control were 28%, 45%, and 63% (p0.1) and of complications were 6%, 20%, and 70% (p0.001), respectively. Also, on applying the Time/Dose/Fractionation formula on brachytherapy doses, it was found that the complication rate was 6% for TDF of31, 25% for TDF of 32-37, and 70% for TDF of38 (p0.001).External radiotherapy doses in the range of 50 to 55 Gy followed by a dose of 10-12 Gy of intraluminal brachytherapy was found optimal with respect to complications and local control in the radiotherapeutic management of esophageal cancer.

IMRT implementation and patient specific dose verification with film and ion chamber array detectors Implementation of Intensity Modulation Radiotherapy (IMRT) and patient dose verification was carried out with film and I'mariXX using linear accelerator with 120-leaf Millennium dynamic multileaf collimator (dMLC). The basic mechanical and electrical commissioning and quality assurance tests of linear accelerator were carried out. The leaf position accuracy and leaf position repeatability checks were performed for static MLC positions. Picket fence test and garden fence test were performed to check the stability of the dMLC and the reproducibility of the gap between leaves. The radiation checks were performed to verify the position accuracy of MLCs in the collimator system. The dMLC dosimetric checks like output stability, average leaf transmission and dosimetric leaf separation were also investigated. The variation of output with gravitation at different gantry angles was found to be within 0.9%. The measured average leaf transmission for 6 MV was 1.6% and 1.8% for 18 MV beam. The dosimetric leaf separation was found to be 2.2 mm and 2.3 mm for 6 MV and 18 MV beams. In order to check the consistency of the stability and the precision of the dMLC, it is necessary to carryout regular weekly and monthly checks. The dynalog files analysis for Garden fence, leaf gap width and step wedge test patterns carried out weekly were in good agreement. Pretreatment verification was performed for 50 patients with ion chamber and I'matiXX device. The variations of calculated absolute dose for all treatment fields with the ion chamber measurement were within the acceptable criterion. Treatment Planning System (TPS) calculated dose distribution pattern was comparable with the I'matriXX measured dose distribution pattern. Out of 50 patients for which the comparison was made, 36 patients were agreed with the gamma pixel match of > 95% and 14 patients were with the gamma pixel match of 90-95% with the criteria of 3% delta dose (DD) and 3 mm distance-to-agreement (DTA). Commissioning and quality assurance of dMLC for IMRT application requires considerable time and effort. Many dosimetric characteristics need to be assessed carefully failing which the delivered dose will be significantly different from the planned dose. In addition to the issues discussed above we feel that individual MU check is necessary before the treatment is delivered.

Various treatment planning systems are used to design plans for the treatment of cervical cancer using high-dose-rate brachytherapy. The purpose of this study was to make a dosimetric comparison of the 2 treatment planning systems from Varian medical systems, namely ABACUS and BrachyVision. The dose distribution of Ir-192 source generated with a single dwell position was compared using ABACUS (version 3.1) and BrachyVision (version 6.5) planning systems. Ten patients with intracavitary applications were planned on both systems using orthogonal radiographs. Doses were calculated at the prescription points (point A, right and left) and reference points RU, LU, RM, LM, bladder, and rectum. For single dwell position, little difference was observed in the doses to points along the perpendicular bisector. The mean difference between ABACUS and BrachyVision for these points was 1.88%. The mean difference in the dose calculated toward the distal end of the cable by ABACUS and BrachyVision was 3.78%, whereas along the proximal end the difference was 19.82%. For the patient case there was approximately 2% difference between ABACUS and BrachyVision planning for dose to the prescription points. The dose difference for the reference points ranged from 0.4-1.5%. For bladder and rectum, the differences were 5.2% and 13.5%, respectively. The dose difference between the rectum points was statistically significant. There is considerable difference between the dose calculations performed by the 2 treatment planning systems. It is seen that these discrepancies are caused by the differences in the calculation methodology adopted by the 2 systems.

Objective The use of radiation for the treatment of keloids has been the topic of debate for years. Methods In this study, 46 symptomatic cases were treated with 90 Sr- 90 Y β-rays. Patients were given four fractions of 5 Gy per fraction either as weekly or twice weekly schedules. Results Radiation dose of 20 Gy given twice weekly in four fractions showed response in 92% of the cases as compared to 81% in those receiving four fractions of 5 Gy weekly. Conclusion Further studies with numerous dose fractionation schedules would open up new dimensions in the radiotherapy of keloids.

A two and half years old male child of sinus histiocytosis with massive lymphadenopathy, paraplegia and spinal cord involvement was treated with surgery and radiotherapy for the spinal cord compression and later with chemotherapy for his nodal disease in the neck. There was a significant improvement in his neurologic status as well as in his nodal status reiterating the role of combination therapy in this disease.

In this study forward scattering effects near different metallic interfaces are measured for Co-60 gamma and 6 and 18 MV photon beams. The studied effects are the transport of secondary electrons across the metallic interface and the scattering of photons by the metallic inhomogeneity.All measurements were carried out with a PTW thin-window, parallel plate ionisation chamber (B 23344-036) and an RDM-1F electrometer with digital readout. Thin sheets of aluminium, mild steel, copper, cadmium and lead were used as inhomogeneities. The inhomogeneities were placed between the polystyrene phantom and the front window of the chamber which was maintained at 100 cm SSD.It was noticed that for a high energy photon beam (18 MV) the forward scatter dose factor (FSDF) increases rapidly as the thickness of the metallic inhomogeneity increases. For low energy photons, there is a sharp initial decrease of the FSDF until a minimum value is reached followed by a slow increase with increasing thickness of the inhomogeneity. It was also noted that the FSDF variation at off-axis distances has slightly more slope compared with the ionization ratio (IR) curves for both 6 MV and 18 MV photons. However, the variation in slope is prominent for 18 MV compared with 6 MV photon beam.The sharp dose decrease observed downstream of a metallic inhomogeneity at relatively low photon energies (Co-60, 6 MV) is attributed to the internal scattering of secondary electrons within the metal. The dose enhancement observed for high energy photon beams is attributed to the domination of the pair production process, increasing with atomic number. Since FSDF is dependent on the photon beam spectra, it can be used as a measure of beam quality across the beam.

Purpose: The aim of this study was to compare few of the dosimetric characteristics of a physical and enhanced dynamic wedge from a dual energy (6 and 18 MV) linear accelerator.Materials and Methods: This study used the Varian Clinac‐DHX (S.No.3172) linear accelerator which is equipped with three different type of wedges. To compare the change in beam quality with physical and enhanced dynamic wedge half value layer (HVL) was measured using a 0.14 cc ion chamber covered with brass build up cap positioned at 2 meter distance from the source and the distance from the target to absorber distance was maintained as 1 meter. Transmission measurements were made for varying thickness of white polystyrene phantom placed on the couch. The surface dose with physical and enhanced dynamic wedges were measured using a parallel plate chamber at 85 and 100 cm source to surface distance (SSD), for 6 and 18 MV photons.Results: The HVL was estimated for 6 and 18 MV photons along the central axis and at off‐axis points for the field size of 20 × 20 cm2 with 45° upper physical wedge and compared with that of the enhanced dynamic wedge (EDW). For physical wedged field, at heel edge side HVL value was high compared with the measured that of EDW. It was noticed that, the HVL variation across the beam was significantly high for 6 MV X‐rays than for 18 MV X‐rays. The measured surface dose was found to be more at 85 cm FSD for all the fields. The lower energy photons (6 MV) were found to result in higher surface dose than the higher energy photons (18 MV). Conclusion: The three wedge systems produce significantly different surface doses that should be considered in properly choosing a wedge system for clinical use.

Purpose: To study the dosimetric characteristics of 2D ion chamber array matrix for verification of Radiotherapy treatment plans. Method and Materials: The ionization chamber array consists of 1020 single air‐vented plane‐parallel plate ion chambers arranged in 32 × 32 matrix. Each chamber is of 4.5 mm diameter, 5 mm height and 0.08 cc of sensitive volume. The measurements were performed in Clinac DHX linear accelerator with 6 MV and 18 MV photons in a solid water phantom. The absolute dose and output factors were estimated for 6 and 18 MV photons using matrix device. The detector reproducibility, dose linearity and dose rate effect was studied. The performance of 2D array, in measuring clinical dose maps, was also investigated. Dose profiles of physical and enhanced dynamic wedge fields were analyzed. Furthermore, various IMRT fluence patterns generated from treatment planning system (TPS) were measured and compared. Results: The matrix device gives the absolute dose values based on estimated calibration factor. The reproducibility of measurements was good and the output and the output factor values were in good agreement with the standard ion chamber measurements. The system response was found to be linear in the dose range of 2–500 cGy and the response of the detector was found to be independent of dose rate. The 2D verification of intensity map at different depths for physical and enhanced dynamic wedges were in good agreement. The calculated and measured IMRT fluence patterns were found to be in good agreement (γ ⩽1:96 %, criteria 3 % &3 mm). Conclusion: On the basis of broad range of tests performed in this study, we conclude that the 2D array matrix is dosimetrically accurate and it can be a useful device for QA and verification of clinical radiotherapy beams.