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Purpose Urothelial carcinomas (UCs), also known as transitional cell carcinomas, account for the majority of upper urinary tract tumors. The gold-standard therapy for operable patients with localized disease is radical nephroureterectomy. However, some patients are not surgical candidates. Data on the use of modern radiation therapy for upper urinary tract UC (UTUC) are scarce. The purpose of this study was to assess the safety and efficacy of SABR in UTUC. Methods and Materials This retrospective study included all patients with UTUC treated with SABR at one institution. Charts were reviewed to evaluate renal function and the development of toxicity using Common Terminology Criteria for Adverse Events, version 3.0. Tumor response on follow-up imaging with computed tomography or magnetic resonance imaging scans was assessed using the Response Evaluation Criteria in Solid Tumors, version 1.1. Results A total of 16 patients (7 patients with UC at the ureter and 9 at the renal pelvis) were identified as treated with SABR. Of the 9 patients with renal pelvis UC, 4 had a previous history of bladder cancer. At the time of treatment, the median age was 85 years (range, 67-95 years). Most patients received 40 Gy in 8 fractions every second day. The median followup was 21 months (range, 3-110 months). Most patients maintained stable renal function, and only 2 patients developed worsening chronic kidney disease, but none required dialysis. Acutely, 4 patients developed grade 1 diarrhea, and 1 patient had new grade 1 hematuria. No chronic side effects were observed. One patient did not have follow-up imaging and was excluded from the tumor-response analysis. Two patients had a complete response of the treated lesion, 9 had a partial response, 2 had stable disease, and 2 had disease progression within the treatment field. Conclusions This small case series suggests that SABR for UTUC is safe and well-tolerated, with good radiographic tumor response to ablative doses of radiation therapy.

External beam radiotherapy is an effective curative treatment option for localized prostate cancer, the most common cancer in men worldwide. However, conventionally fractionated courses of curative external beam radiotherapy are usually 8–9 weeks long, resulting in a substantial burden to patients and the health-care system. This problem is exacerbated in low-income and middle-income countries where health-care resources might be scarce and patient funds limited. Trials have shown a clinical equipoise between hypofractionated schedules of radiotherapy and conventionally fractionated treatments, with the advantage of drastically shortening treatment durations with the use of hypofractionation. The hypofractionated schedules are supported by modern consensus guidelines for implementation in clinical practice. Furthermore, several economic evaluations have shown improved cost effectiveness of hypofractionated therapy compared with conventional schedules. However, these techniques demand complex infrastructure and advanced personnel training. Thus, a number of practical considerations must be borne in mind when implementing hypofractionation in low-income and middle-income countries, but the potential gain in the treatment of this patient population is substantial., Conventionally fractionated external beam radiotherapy is an effective treatment for localized prostate cancer, but long treatment programmes result in a substantial burden to patients and the health-care system, which is particularly problematic in low-income and middle-income countries (LMICs) where health-care resources might be scarce and patient funds limited. Here, the authors discuss the outcomes and benefits of hypofractionation — in terms of both oncology and economics — and how it could be used to improve prostate cancer care in LMICs., Key points The global burden of prostate cancer is increasing and prostate cancer is becoming a major source of health-care burden in low-income and middle-income countries (LMICs).Radiotherapy is an essential treatment modality in the management of prostate cancer. However, radiotherapy resources are lacking in LMICs, resulting in excess morbidity and mortality.Hypofractionated radiotherapy schedules offer an opportunity to maintain excellent treatment outcomes while shortening curative radiotherapy courses. This approach expands the treatment capacity and could improve crucial access in communities with limited radiotherapy resources.Initial investments are required for technological upgrades, such as intensity-modulated radiotherapy and image-guided radiotherapy, as well as in specialized training in order to optimally provide hypofractionated treatment. Discussion amongst government agencies and device manufacturers is essential to lower these costs.Personnel training and access to external consultation are critical resources for developing radiotherapy centres. Information and communication technologies enable remote guidance between developing and developed radiotherapy centres.In the long term, hypofractionation programmes result in long-term cost savings and simultaneously expand patient access to a curative modality in the management of prostate cancer.

The Canadian Organization of Medical Physicists (COMP), in close partnership with the Canadian Partnership for Quality Radiotherapy (CPQR) has developed a series of Technical Quality Control (TQC) guidelines for radiation treatment equipment. These guidelines outline the performance objectives that equipment should meet in order to ensure an acceptable level of radiation treatment quality. This particular TQC contains detailed performance objectives and safety criteria for CyberKnife® Technology. The quality control recommendations in this document are based upon previously published guidelines and the collective experience of all Canadian sites using this technology. This TQC guideline has been field tested at the newest Canadian CyberKnife installation site and includes recommendations for quality control of the Iris™ and InCise™ MLC collimation systems.

The Canadian Organization of Medical Physicists (COMP), in close partnership with the Canadian Partnership for Quality Radiotherapy (CPQR) has developed a series of Technical Quality Control (TQC) guidelines for radiation treatment equipment. These guidelines outline the performance objectives that equipment should meet in order to ensure an acceptable level of radiation treatment quality. This particular TQC contains detailed performance objectives and safety criteria for CyberKnife® Technology. The quality control recommendations in this document are based upon previously published guidelines and the collective experience of all Canadian sites using this technology. This TQC guideline has been field tested at the newest Canadian CyberKnife installation site and includes recommendations for quality control of the Iris™ and InCise™ MLC collimation systems.

Purpose: To model the stereotactic mode of the Varian‐Brainlab Novalis TX linear accelerator using the BEAMnrc Monte Carlo user code Methods: The EGSnrc Monte Carlo user codes BEAMnrc and DOSXYZnrc were used for photon simulations and dose calculations, respectively. A Monte Carlo model of a Varian Clinac 21 EX was modified to model the stereotactic radiosurgery(SRS) mode of the Novalis, taking into account the smaller dimensions of the SRS flattening filter and limited field sizes. The parameters of source such as energy, size and angular spread, were readjusted following a new procedure outlined by Almberg et al, 2012. A component module, DYNVMLC, previously used to model the Varian Millennium 120 multi‐leaf collimator(MLC), was reprogrammed to include the four leaf types of the Varian high definition 120 leaf MLC. Interleaf air‐gap and leaf density were adjusted to match interleaf leakage profiles measured with EBT2 film. Subsequent validation included profiles, percent depth dose curves and output factors measured with ion chambers, and other film measurements. Results: From PDD measurements, the energy of the incident electron beam was determined to be 6.6 MeV. From penumbra measurements, the electron radial intensity distribution, given as the full width at half maximum of a Gaussian distribution, was found to be 0.7 mm (cross‐plane) and 0.8 mm (in‐plane). From profiles in water, the mean angular spread had to be adjusted to 1.27° to achieve an acceptable match. The interleaf air‐gap and the density of the leaves of the HDMLC were determined to be 0.0047 cm and 18.5 g/cm3, respectively. Conclusions: The Almberg procedure was successfully implemented in determining the electron beam parameters to model the Novalis Tx's SRS mode. Dose profiles simulated with the new HDMLC component module agreed with measurements within 2%.

To report our experience with linear accelerator-based stereotactic fractionated radiotherapy in the treatment of juxtapapillary choroidal melanoma.We performed a retrospective review of 50 consecutive patients diagnosed with juxtapapillary choroidal melanoma and treated with linear accelerator-based stereotactic fractionated radiotherapy between April 2003 and December 2009. Patients with small to medium sized lesions (Collaborative Ocular Melanoma Study classification) located within 2 mm of the optic disc were included. The prescribed radiation dose was 60 Gy in 10 fractions. The primary endpoints included local control, enucleation-free survival, and complication rates.The median follow-up was 29 months (range, 1-77 months). There were 31 males and 29 females, with a median age of 69 years (range, 30-92 years). Eighty-four percent of the patients had medium sized lesions, and 16% of patients had small sized lesions. There were four cases of local progression (8%) and three enucleations (6%). Actuarial local control rates at 2 and 5 years were 93% and 86%, respectively. Actuarial enucleation-free survival rates at 2 and 5 years were 94% and 84%, respectively. Actuarial complication rates at 2 and 5 years were 33% and 88%, respectively, for radiation-induced retinopathy; 9.3% and 46.9%, respectively, for dry eye; 12% and 53%, respectively, for cataract; 30% and 90%, respectively, for visual loss [Snellen acuity (decimal equivalent),0.1]; 11% and 54%, respectively, for optic neuropathy; and 18% and 38%, respectively, for neovascular glaucoma.Linear accelerator-based stereotactic fractionated radiotherapy using 60 Gy in 10 fractions is safe and has an acceptable toxicity profile. It has been shown to be an effective noninvasive treatment for juxtapapillary choroidal melanomas.

Introduction: We have assessed the planning target volume (PTV) margins required for adequate treatment of the prostate in the absence of daily localization imaging based on the statistical analysis of a large data set obtained from 5 years of use of a two-dimensional ultrasound pretreatment localization device. Methods and Materials: Data from 387 prostate patients were analyzed retrospectively. Every patient in the study received daily pretreatment localization resulting in a total of 10,327 localizations, each comprising an isocenter displacement in three directions: anteroposterior, right-left lateral, and superior-inferior. The mean displacement for each direction for each patient was computed from daily treatment records, and a mean of the means was used in the analysis. Results: The mean displacements required to shift the target to the required position were 6.1 mm posterior (4.4 mm SD), 2.1 mm superior (4.5 mm SD), and 0.5 mm right (3.6 mm SD). The 6.1-mm shift posterior is indicative of a systematic uncertainty. Differences in planning conditions between the computed tomography simulation and the treatment room may account for this discrepancy. Conclusion: Our study has revealed systematic intertreatment uncertainties that would have required a nonuniform PTV margin ranging in dimensions between 2.7 mm anterior, 14.9 mm posterior, 7.7 mm right, 6.7 mm left, 11 mm superior, and 7 mm inferior to encompass the prostate for 95% of our sample if the ultrasound localization system were not used. In the absence of systematic uncertainties, a uniform PTV margin of 9 mm would suffice.

Stereotactic radiosurgery with several static conformal beams shaped by a micro multileaf collimator (microMLC) is used to treat small irregularly shaped brain lesions. Our goal is to perform Monte Carlo calculations of dose distributions for certain treatment plans as a verification tool. A dedicated microMLC component module for the BEAMnrc code was developed as part of this project and was incorporated in a model of the Varian CL2300 linear accelerator 6 MV photon beam. As an initial validation of the code, the leaf geometry was visualized by tracing particles through the component module and recording their position each time a leaf boundary was crossed. The leaf dimensions were measured and the leaf material density and interleaf air gap were chosen to match the simulated leaf leakage profiles with film measurements in a solid water phantom. A comparison between Monte Carlo calculations and measurements (diode, radiographic film) was performed for square and irregularly shaped fields incident on flat and homogeneous water phantoms. Results show that Monte Carlo calculations agree with measured dose distributions to within 2% and/or 1 mm except for field size smaller than 1.2 cm diameter where agreement is within 5% due to uncertainties in measured output factors.

Radioactive plaque brachytherapy has an established role for selected patients with retinoblastoma. Newer non-invasive radiotherapy techniques such as stereotactic conformal radiotherapy (SCR) that uses highly accurate positioning to deliver treatment with small beams may be an interesting alternative to brachytherapy. We report a case treated with SCR and compare the dosimetry with that achievable with brachytherapy. With advantages and disadvantages to both, SCR should more often be considered in the management of RB because of the more homogeneous dose within the target volume and similar or lower doses to surrounding normal tissues. Pediatr Blood Cancer. 2010;55:1210–1212. © 2010 Wiley-Liss, Inc.

Purpose: For female patients, radiotherapy treatment for Hodgkin’s disease invariably results in the irradiation of breast tissue that may lead to radiation induced secondary cancers. The risk for secondary breast cancer is correlated with dose. We have developed a technique in an attempt to increase breast sparing during mantle field irradiation for female patients. Material and Methods: To minimize the irradiated breast volume, a virtual simulation technique making use of a Styrofoam breast immobilization board has been developed whereby the patient lies prone with the breasts positioned in grooves within the board. The breast position is adjusted using Styrofoam wedges, and breast placement is verified using an AP CT-pilot view. A CT scan of the neck and thoracic regions is taken, and the lymph nodes, breast volume and critical structures are outlined. Virtual simulation of the mantle fields (typically AP/PA isocentric beams) is performed, and beam blocks are drawn on the digitally reconstructed radiographs (DRR) generated by the virtual simulation package. The shielding is designed to allow adequate margins around the lymph nodes while maximizing shielding of the lung and breast tissues. The para-aortic fields are also easily determined through virtual simulation, where multi-planar reconstructions (MPR) and 3D renderings of the patient’s CT data are used to determine the field limits and beam gaps. In addition to allowing for the geometric optimization of the positioning of the breasts under the lung shields, the virtual simulation technique provides the necessary information for a 3D dosimetric analysis, including dose-volume histograms (DVHs) of the irradiated breast volume. Results: The 3D breast sparing technique was qualitatively and quantitatively compared to non-CT-based techniques and other 3D techniques currently available to assess the protection of the breasts. In a preliminary analysis, virtual simulation images (DRRs, 3D rendering and multi-planar reconstruction) demonstrated the advantage of using the breast sparing technique. A further analysis of DVHs showed a reduction of at least 50% in the volume of breast tissue irradiated when using the breast positioning board and virtual simulation as compared to the conventional simulation techniques where a breast immobilization board was not used. Conclusions: The use of a breast immobilization board and of a virtual simulation technique is recommended for the planning and treatment of female patients with Hodgkin’s disease. DVH analysis has shown that this leads to a decrease in the volume of breast irradiated. It is hoped that this approach will reduce the risk of secondary breast malignancies in female patients with Hodgkin’s disease.

Purpose: The dosimetry of hip irradiation for the prevention of heterotopic bone formation following arthroplasty is complicated by the use of custom shielding in the treatment portal, and the fact that irradiation is usually required during a 48 hour period following surgery. Both the machine output and depth dose factors of the resulting fields are modified by the presence of the shielding blocks. A simplified dosimetric approach, based on correction factors for both the output and depth dose as a function of field geometry is presented for various megavoltage energy beams. Materials and Methods: Measurements of relative dose factors (RDF) and percentage depth dose (PDD) were carried out for different combinations of field size, block size and separation between adjacent blocks. Both RDF and PDD measurements were made in a water phantom. Ratios of RDF and PDD were obtained by dividing individual measurements or curves by the corresponding values for the open field (i.e., without blocks). The average values of these ratios constitute the correction factors to be applied for a given MU or treatment time calculation. Results: Extensive RDF and PDD measurements reveal that for the field and block dimensions of interest the correction factors for RDF can be parameterized as a function of separation between two adjacent blocks and beam energy alone and the depth correction factors are additionally only a function of depth. The correction factors for depth dose are equally valid for fixed source-skin distance techniques (that use PDD) and fixed source-axis distance techniques (that use TMR). Conclusion: A simple model for the calculation of output in hip irradiation is presented for the situation where the use of computer-based algorithms may not be practical. The model accurately predicts the RDF of the treatment portal to within 2% and the PDD to within 2% for the range of field sizes, block sizes, block gaps and beam energies of interest ignoring other variables.

Purpose: To assess intra-fraction positional stability of lung cancer tumours in patients treated by kilo-voltage cone-beam computed tomography (CBCT)-guided stereotactic body radiotherapy (SBRT) without the use of customized immobilization devices. Material and Methods: Twenty-two patients underwent 4D-CT in the supine position with the arms in a wing board but without customized immobilization. The PTV was the internal target volume based on maximum intensity projections and a 5mm symmetric setup margin. Treatments were planned using 7–9 static fields or two volumetric modulated arcs. At treatment, the patient position was adjusted using pre-treatment CBCT. A post-treatment CBCT was taken immediately after the treatment ended. The 41 CBCT pairs were automatically matched and the transitional shifts between the two CBCTs recorded. The mean values and standard deviations were calculated for these displacements. Results and conclusions: The mean time between CBCTs (treatment time) was 16.5 ± 6 minutes (range: 10 to 34 minutes). In all cases the tumour remained inside the PTV in the post-treatment CBCT. The mean shifts between pre and post-treatment CBCTs were −0.7 ± 1.6 mm (range −5.0 to 3.0 mm) vertically, −0.3 ± 1.7 mm (range −4.8 to 3.0 mm) longitudinally, and −0.4 ± 1.5 mm (range −4.0 to 2.0 mm) laterally. Our results suggest little systematic shifting during treatment, and standard deviations that are consistent with another published report for treatments where customized immobilization was used. This result is encouraging for SBRT programs in clinics with limited resources.

We have developed a total body photon irradiation technique using multiple overlapping open field arcs (TB-ARC). This simple technique uses predetermined arc-weights, with MUs calculated as a function of prescription depth only. Patients lie on a stretcher, in the prone/supine treatment position with AP/PA arcs. This treatment position has many advantages including ease of delivery (especially for tall, pediatric or compromised patients), dose uniformity, simplicity for organ shielding, and imaging capabilities. Using a Varian TrueBeam linac, 14 arcs using 40×40 cm2 6 MV open photon beams, sweeping across 10 degrees each, complete a 140 degree arc. The nominal SSD at zero degrees is 200 cm. Arcs at the sweep limits (+/− 70 degrees) are differentially weighted and deliver a dose within 10% of the prescription on central axis, at a depth of 10 cm over a superior-inferior length of 275 cm. CT planning using Varian Eclipse enables dose evaluation. A custom made beam spoiler, consisting of a 2.5 m sheet of polycarbonate (6 mm thick) increases the surface dose from 45% to 90%. This beam spoiler also serves as a support in the event that differential attenuation is required for organs such as lung, heart, liver, kidneys. The geometry of the sweeping beam technique limits organ dose (using varying thicknesses of melting alloy) to about 20% and 40% of prescription at dmax and midplane respectively. Digital imaging with a portable DR cassette enables proper attenuator location prior to treatment.

Background: Liver lesions cannot be directly visualized at the time of radiation treatments using conventional imaging techniques. Metal markers are often used as surrogates of tumo

Aims Late rectal toxicity is a major concern for prostate cancer patients treated with radiotherapy. Rectal dose–volume constraints, set as guidelines to reduce its incidence, vary among institutions. From a group of patients uniformly treated with hypofractionated radiotherapy, we correlated the incidence of late rectal toxicity with rectal dose–volume rectal constraints as described in three randomised trials for prostate cancer. Materials and methods Favourable-risk prostate cancer patients received a dose of 66 Gy in 22 fractions without hormonal therapy. Toxicity was prospectively assessed using Common Toxicity Criteria v3. The whole or part of the rectum and rectal wall were contoured as an organ at risk for all patients. The rectal constraints of the RTOG 0126, RTOG 0415 and the PROFIT trials were used to correlate with late rectal toxicity. Results The median follow-up time was 58 months. Late rectal toxicity was 62, 20 and 18% for grades 0, 1 and 2/3, respectively. No statistically significant correlation was found between late rectal toxicity and the rectal constraints used in the three trials. The number of patients violating the recommended constraints was similar for the group with grade 2/3 toxicity and the group without any toxicity. Analysis derived from the actual dose–volume histogram dose parameters of this group of patients did not show a relationship between dose to volume of the rectum and late rectal toxicity that could generate a guideline of dose constraints. Conclusion For this group of patients, despite the use of recognised dose–volume constraint guidelines of three trials, we were unable to establish a relationship between these constraints and the late rectal toxicity registered. Further studies on the correlation of dosimetric parameters with rectal toxicity, particularly for hypofractionated regimens, are required. Non-dosimetric factors may also be involved in the risk of late rectal toxicity.

Purpose High–dose rate brachytherapy (HDRB) is frequently used as a boost to external beam radiation therapy (EBRT) in prostate cancer patients. With the increasing use of small planning target volume margins in EBRT, prostatic edema induced by HDRB can be a contributing factor to geometric miss when HDRB is performed before or during EBRT. We assessed prostate gland volumetric change after single-fraction HDRB and its impact on definition of treatment volume for EBRT. Methods and Materials Thirty-one consecutive patients with intermediate-risk prostate cancer treated with single-fraction HDRB (10 Gy) combined with hypofractionated EBRT were analyzed. A second CT scan was performed 7 days after HDRB, and images were coregistered with the planning CT scan that contained the original clinical target volume (CTV). The post-HDRB prostate CTV volume was compared with the original CTV by a single observer. Results All patients presented volumetric variation. In most cases (68%), the prostate increased in volume, whereas it decreased in 32%. The mean prostatic volume was 42.2 cc before HDRB and 43.6 cc after HDRB, representing a mean volume difference of 3.4%, ranging from −14.2% to 23.8% (p = 0.756). This difference is the result of mean changes of 0.6 mm (−6.1 to 6.6) in the anterior–posterior, 0.5 mm (−5.5 to 3.0) in the lateral, and 0.2 mm (−5.0 to 5.0) in the superior–inferior axes. Conclusions Although a nonsignificant volumetric change occurs after single-fraction HDRB, individual variations on specific axis could lead to important uncertainties during EBRT.

The use of fractionated stereotactic radiotherapy (fsrt) has evolved with technical advances in noninvasive immobilization, radiation delivery, and image guidance. The application of fsrt to pituitary tumours is aimed at reducing toxicity through improved dose conformality and reduced treatment margins. The aim of the present paper is to report our own experience and to review the published data on fsrt for pituitary macroadenomas. Between September 2000 and October 2005, 13 patients with pituitary macroadenoma underwent fsrt at our institution. In 12 patients, radiotherapy treatment followed surgical resection (transsphenoidal resection in 8, frontal craniotomy in 3, and multiple transsphenoidal resections followed by craniotomy in 1). In 4 patients, the tumours were functional (2 adrenocorticotropic hormone&ndash, secreting, 1 prolactinoma, and 1 growth hormone&ndash, secreting), the tumours in the remaining patients were clinically non-secretory. Before radiation, 3 patients had panhypopituitarism, and 6 patients had visual field defects. All patients were treated with fsrt using non-coplanar micro&ndash, multileaf collimation portals. A median dose of 50.4 Gy (range: 45&ndash, 60 Gy) was prescribed to the 76.9%&ndash, 95.2% isodose surface and delivered in 1.8-Gy fractions. The median planning target volume (gross tumour plus 3 mm) was 33.5 cm3 (range: 3.2&ndash, 75 cm3). After a median follow-up of 24 months (range: 6&ndash, 60 months), local control was 100%. One patient achieved clinical complete response. Treatment was well tolerated acutely for all patients. Neither radiation-induced optic neuropathy nor any radiation-related endocrine dysfunction was observed in our patients. In accordance with published series, we found fsrt to be safe and effective in the management of large pituitary macroadenomas.

Objective To determine the feasibility and toxicity profile of accelerated radiotherapy with a simultaneous integrated boost fractionation scheme with intensity-modulated radiotherapy (SIB-IMRT) with or without chemotherapy. Study Design and Setting Forty-nine patients with advanced head and neck cancer underwent SIB-IMRT. Concomitant chemotherapy was administered in 29 patients. Results Grade 3 acute toxicities included 55% mucositis, 20% odynophagia, 12% nausea, 18% hematologic, and 8% skin. There were no grade 4 toxicities or treatment-related deaths. With a median follow-up of 25 months, locoregional control was 83%, and overall survival was 80%. Of patients with grade 3 late toxicities, two patients (4% of the total) required a permanent percutaneous endoscopic gastrostomy tube, and osteonecrosis occurred in one patient (2% of the total). Conclusions SIB-IMRT is a feasible technique that shortens the overall treatment time in the radical treatment of patients with advanced head and neck cancer while maintaining acceptable rates of acute toxicity in this study. Although the results are promising, this approach should be considered only in the setting of a clinical trial.

From a radiation treatment planner perspective, in the treatment of prostate cancer, inverse-planned intensity-modulated radiation therapy (IMRT) differs considerably from conventional, conformal, and forward-planned IMRT. In this work we aim to discuss the rationale behind the use of inverse-planned IMRT for the treatment of prostate cancer, as well as some of the practical aspects, including the differences in planning strategies, dose fractionation and issues in plan evaluation.The primary motivation behind the use of inverse-planned IMRT for prostate cancer radiotherapy is to attempt further dose escalation while maintaining critical structure and healthy tissue sparing at an acceptable level. The sparing of normal tissues is largely dependent on the size of the planning target volume (PTV) defined, and if the PTV overlaps critical structures. Depending on how the PTV is defined it may be impossible to achieve the desired healthy tissue sparing even with IMRT. A second role for the use of IMRT in the treatment of prostate cancer may be to conform the isodose distribution to a complex PTV, such as one that includes the seminal vesicles or the pelvic lymph nodes in the treatment volume. Finally, inverse planned IMRT may be useful in the planning and delivery of simultaneous integrated boosts where different parts of the target structures receive different daily doses. This again has applications for the simultaneous treatment of pelvic lymph nodes with the prostate treatment volume, and presents interesting opportunities for hypo-fractionation. All of these options of course require careful plan evaluation with respect to isodose distributions and dose-volume constraints as well as the radiobiological consequences of using unconventional fractionation.IMRT seems to be the most effective modality for treating complex target geometries and for delivering simultaneous integrated boosts. In particular for prostate cancer, the simultaneous treatment of the prostate and pelvic lymph nodes lends itself perfectly to IMRT, allowing the prostate to receive a higher daily dose per fraction, as well as minimizing the amount of small bowel in the field, while at the same time sparing the rectum and bladder adequately. Inverse-planned IMRT is, however, a complex procedure, and to safely implement it, an extensive patient- and machine-specific quality assurance program is required.

Purpose Despite major advances in treatment modalities, the prognosis of patients with glioblastoma multiforme (GBM) remains poor. Exploring hypofractionated regimens to replace the standard 6-week radiotherapy schedule is an attractive strategy as an attempt to prevent accelerated tumor cell repopulation. There is equally interest in dose escalation to the gross tumor volume where the majority of failures occur. We report our preliminary results using hypofractionated intensity-modulated accelerated radiotherapy regimen in the treatment of patients with GBM. Methods and materials Between July 1998 and December 2001, 25 patients with histologically proven diagnosis of GBM, Karnofsky performance status ≥60, and a postoperative tumor volume ≤110 cm 3 were treated with a hypofractionated accelerated course of radiotherapy. The gross tumor volume (GTV) was defined as the contrast-enhancing lesion on the postoperative MRI T1-weighted images with the latter fused with computed tomography images for treatment planning. The planning target volume was defined as GTV + 1.5-cm margin. Using forward-planning intensity modulation (step-and-shoot technique), 60 Gy in 20 daily fractions of 3 Gy each were given to the GTV, whereas the planning target volume received a minimum of 40 Gy in 20 fractions of 2 Gy each at its periphery. Treatments were delivered over a 4-week period using 5 daily fractions per week. Dose was prescribed at the isocenter (ICRU point). Three beam angles were used in all of the cases. Results Treatments were well tolerated. Acute toxicity was limited to increased brain edema during radiotherapy in 2 patients who were on tapering doses of corticosteroids. This was corrected by increasing the steroid dose. At a median follow-up of 8.8 months, no late toxicity was observed. One patient experienced visual loss at 9 months after completion of treatment. MRI suggested nonspecific changes to the optic chiasm. On review of the treatment plan, the total dose to the optic chiasm was confirmed to be equal to or less than 40 Gy in 20 fractions. When Radiation Therapy Oncology Group recursive partitioning analysis was used, 10 patients were class III–IV, and 15 patients were class V–VI. To date, 21 patients have had clinical and/or radiologic evidence of disease progression, and 16 patients have died. The median survival was 9.5 months (range: 2.8–22.9 months), the 1-year survival rate was 40%, and the median progression-free survival was 5.2 months (range: 1.9–12.8 months). Conclusion This hypofractionated accelerated irradiation schedule using forward planning (step-and-shoot) hypofractionated, intensity-modulated accelerated radiotherapy is feasible and seems to be a safe treatment for patients with GBM. A 2-week reduction in the treatment time may be of valuable benefit for this group of patients. However, despite this accelerated regimen, no survival advantage has been observed.

Stereotactic radiosurgery is often used for treating functional disorders. For some of these disorders, the size of the target can be on the order of a millimeter and the radiation dose required for treatment on the order of 80 Gy. The very small radiation field and high prescribed dose present a difficult challenge in beam calibration, dose distribution calculation, and dose delivery. In this work the dose distribution for dynamic stereotactic radiosurgery, carried out with 1.5 and 3 mm circular fields, was studied. A 10 MV beam from a Clinac-18 linac (Varian, Palo Alto, CA) was used as the radiation source. The BEAM/EGS4 Monte Carlo code was used to model the treatment head of the machine along with the small-field collimators. The models were validated with the EGSnrc code, first through a calculation of percent depth doses (PDD) and dose profiles in a water phantom for the two small stationary circular beams and then through a comparison of the calculated with measured PDD and profile data. The three-dimensional (3-D) dose distributions for the dynamic rotation with the two small radiosurgical fields were calculated in a spherical water phantom using a modified version of the fast XVMC Monte Carlo code and the validated models of the machine. The dose distributions in a horizontal plane at the isocenter of the linac were measured with low-speed radiographic film. The maximum sizes of the Monte Carlo-calculated 50% isodose surfaces in this horizontal plane were 2.3 mm for the 1.5 mm diameter beam and 3.8 mm for the 3 mm diameter beam. The maximum discrepancies between the 50% isodose surface on the film and the 50% Monte Carlo-calculated isodose surfaces were 0.3 mm for both the 1.5 and 3 mm beams. In addition, the displacement of the delivered dose distributions with respect to the laser-defined isocenter of the machine was studied. The results showed that dynamic radiosurgery with very small beams has a potential for clinical use.

Radiosurgery for arteriovenous malformations (AVM) is commonly planned with MR, CT and digital subtraction angiography (DSA) images. T1-weigted MRI and CT provide excellent anatomical information but do not reveal vascular flow. For this reason, DSA images are employed for target localisation, but being 2D projections of 3D structures, they have been shown to be inadequate for the 3D definition of large, complexly shaped AVMs. Magnetic resonance angiography (MRA) does provide vascular volume data, but it suppresses stationary anatomical information and therefore, alone, it cannot be used for treatment planning. To benefit from the functionality of all modalities, the authors have developed a multimodality image fusion environment, which combines 3D MRA and 2D DSA vasculature information with 3D MR/CT anatomical information. Within this environment, MRA/MR/CT datasets are registered and fused by reformatting in common stereotactic space. DSA images are linked to 3D datasets in stereotactic space by recovering their acquisition geometry. The consistency of the recovery procedure is verified by correlation of the DSA images to 2D ray-traced projections of the MRA/MR/CT datasets. Since after the fusion, organ contours drawn on any dataset simultaneously appear on all others, all vascular and anatomical information can be used in the process of target/organ localisation and true 3D delineation. Seven patients that have previously undergone radiosurgery for AVMs are currently being replanned within this environment. The newly defined target volumes are found to differ from those based only on DSA images. This finding can have significant dosimetric implications especially for large AVMs.

Purpose: To evaluate the role of stereotactic radiosurgery in the treatment of angiographically occult vascular malformations (AOVMs). Methods and Materials: From 1987 to 1996, 21 patients, 10 males and 11 females, median age of 41 years (range: 7–75 years), with an intracerebral AOVM underwent stereotactic radiosurgery at our institution. All were considered at high risk for surgical intervention. The vascular lesions were located in the brainstem (17 patients), basal ganglia (2), occipital lobe (1), and cerebellum (1). Diagnosis was based on high-resolution magnetic resonance imaging (MRI). Clinical presentation at onset included previous intracerebral hemorrhage (20 patients) and epilepsy (1). All patients were treated with a linac-based radiosurgical technique. The median dose delivered was 25 Gy (range 13–50 Gy), typically prescribed to the 80–90% isodose surface (range 50–90%), which corresponded to the periphery of the vascular malformation. Patients were followed by clinical neurologic assessment and by MRI on a regular interval basis. Results: Follow-up was obtained in 20 patients; clinical or MRI information was not available for 1 patient, and this patient was excluded from our analysis. At a median follow-up of 77 months (range: 4–141 months), follow-up MRIs postradiosurgery do not demonstrate any changes in the appearance of the AOVM. Four patients developed an intracranial bleed at 4, 8, 35, and 57 months postradiosurgery. Annual hemorrhage rates were considerably higher in the observation period preradiosurgery than postradiosurgery (30% vs. 3.2%, p < 0.001). Complications postradiosurgery were observed in 4 patients. Three patients developed mild to moderate edema surrounding the radiosurgical target, expressed at 5, 8, and 24 months, respectively. In all cases, the edema was transient and resolved completely on subsequent MRIs. One of the 4 patients developed radiation necrosis 8 months after radiosurgery. Conclusion: The use of stereotactic radiosurgery in the treatment of AOVM continues to be controversial. Our results appear to show a reduction in the risk of symptomatic hemorrhage post treatment. Patients with previous history of hemorrhage or progressive neurologic deficit and small, well circumscribed lesions may benefit from a trial of stereotactic radiosurgery.

Radiosurgery is the preferred treatment for arteriovenous malformations (AVM) which are situated in deep brain locations such as close to the brain stem, or near critical areas such as the visual cortex1. The technique is commonly planned using multiple modalities, such as magnetic resonance (MR), computed tomography (CT) and digital subtraction angiography (DSA). T1 weighted MR images and CT images provide anatomical information but without additional contrast media, these techniques fail to provide adequate vascular information. For this reason, DSA images, which are obtained after contrast injection, are employed for target localisation. However, since these images are 2D projections of 3D structures, they may be inadequate for the 3D definition of large, complexly shaped AVMs2. Since the AVMs treated by radiosurgery are usually close to organs at risk, the dose must conform to the target and therefore accurate 3D target delineation may help achieve this goal.

Models for the calculation of upper and lower limiting values to the backscatter factor (BSF) are presented. The upper limit is obtained from Monte Carlo simulations of infinite parallel beams incident on semi-infinite phantoms with the dose contributions from all orders of photon scatter considered. The lower limits are calculated using an analytical photon transport model which considers only the primary dose and the scatter dose from photons that have undergone single scattering interactions in the phantom. The limiting values can be used to evaluate measured and modelled BSF values for x-ray beams with photons ofor = 150 keV. A parametrization of the limiting values in terms of photon energy and irradiation field size is presented so that results determined for monoenergetic beams can be extended to polyenergetic spectra. The utility of the limits is illustrated by comparisons made with BSFs from the literature.

Our project consisted of validating the BrainLab iPlan Monte Carlo algorithm, used in conjunction with the stereotactic radiosurgery (SRS) mode of the Varian Novalis TX linear accelerator, for clinical use. Our approach was to "benchmark" the iPlan algorithm by comparing dose distributions with those obtained using a BEAMnrc model of the Novalis SRS mode. The BEAMnrc model was obtained by modifying an existing accelerator model to include the SRS flattening filter and source characteristics of the Novalis TX, and by reprogramming a component module to model the high definition 120-leaf multi-leaf collimator. The free parameters of interleaf air gap and leaf density were adjusted by matching to interleaf leakage profiles measured with EBT2 film. The BEAMnrc model was used to perform comparisons of depth dose curves and planar distributions for fields in homogeneous and heterogeneous slab phantoms between both MC codes and film. The source parameters of electron beam energy, size and angular spread were determined to be 6.6 MeV, 0.7 mm and 0.8 mm (cross and in-plane), and 1.27°, respectively. Comparisons between iPlan and EGSnrc MC codes show agreement within 2% for PDD curves, and a high pass rate (>98%) on gamma analysis (3%/3mm) for planar distributions, when the scored quantity is dose to medium. Discrepancies between both MC codes and film measurements were seen near bone inhomogeneities, where the film trend agrees somewhat with iPlan MC reporting dose-to-water. Further work is being performed to understand these differences and how film is used to measure dose near bone.

Purpose: To evaluate the positioning accuracy of the BrainLAB ExacTrac Image Guidance System under gating conditions. Methods: Two types of phantoms were used in measurements: an anthropomorphic RANDO head phantom and a BrainLAB ExacTrac Gating Phantom. Our setup included a Varian Novalis Tx radiosurgery system equipped with the ExacTrac 6D IGRT. This system consists of an infrared positioning system for the initial patient positioning and patient tracking, and a stereoscopic kV X‐ray imaging system for final localization using internal markers or anatomy.Uncertainties were broken down into individual components, and the different BrainLAB fusion modalities (internal markers and bony fusion) were used to compare the effect of slice thickness on positional accuracy. Gating uncertainties were deduced with varying tumor motion amplitudes and window sizes in conjunction with a hidden target test. Results: Our results of CT slice thickness dependence for both fusion algorithms with the hidden target test gave similar deviation (

Purpose: To implement and assess the radiological safety of a modified Last‐Person‐Out (LPO) interlock circuit in the bunker of a robotic Novalis/Exactrac stereotactic radiosurgerylinac allowing the Exactrac imaging system to operate with the bunker door open. Methods: The Exactrac floor mounted X‐ray imaging system is designed to be used with the bunker door open, however access control is a concern in bunkers not designed for open door operation. The door interlock contact in our Exactrac generator was identified and a LPO circuit for the Exactrac imaging system interlocked with the operator console was installed. This allowed for operation of the Exactrac imaging system with the door open while providing access control using a light shower (Banner‐Engineering) installed at the maze entrance. To assess the radiological safety for operators, a large volume ionization chamber (PTW32003) used in conjunction with an electrometer (Keithley6517A) was placed at the location of the bunker door at the entrance to the maze. 100 radiographs (50 from each X‐ray tube) were taken with the Exactrac X‐ray imaging using a cranial standard (100 kVp, 80 mA and 100 ms) and a 20 × 20 × 20 cm3 solid water phantom placed at isocentre to simulate the patient. This corresponds to 2 to 3 times our typical daily load. Results: The Exactrac LPO system runs in parallel to the Novalis Last‐Person‐Out system that remains unaffected by the modification. Our measurements revealed a yearly equivalent dose at the open door of 4 micro‐Sv per year, and a committed dose of 0.5 micro‐Sv per year (assuming one‐eighth occupancy factor). Conclusions: An access control system was implemented on our Novalis/Exactrac system allowing the imaging system to be safely used with the treatment door open. Prior to use, the federal regulator (CNSC) was notified and staff training was provided.

83 Background: We present the long-term results of a cohort of patients with intermediate-risk prostate cancer (PC) treated with single fraction high-dose-rate brachytherapy (HDRB) combined with hypofractionated external beam radiation therapy (HRT). Methods: Patients with intermediate-risk PC were treated exclusively with HDRB and HRT. HDRB delivered a dose of 10 Gy to the prostate gland and HRT consisted of 50 Gy delivered in 20 daily fractions. The planning target volume was the prostate gland with a 1 cm margin all around. The first 121 consecutive patients with a minimum of 2 years post-treatment follow-up were assessed for acute and chronic toxicity and disease control. Results: The median follow-up was 62.8 months. No acute grade III or higher toxicities were seen. Grade II late GI toxicity was seen in 9 patients (7.4%) and grade III in 2 (1.6%). Grade 3 GU toxicity was seen in 2 patients (1.6%), both with urinary obstructive symptoms requiring catheterization. A repeat biopsy was offered to the first 58 consecutively treated patients, and 44 patients agreed with the procedure. A negative biopsy was found in 40 patients (91%). The biochemical relapse-free survival rate at 5 and 8 years were 90.7% and 81.4%, with 13 patients presenting biochemical failure. Among them, nine were diagnosed with distant metastasis. Prostate cancer-specific and overall survival rates at 8 years were 100% and 95.5%, respectively. Conclusions: Our program of HDRB and HRT is well tolerated, with acceptable toxicity rates. Furthermore, results from re-biopsies revealed an elevated rate of local control. These results are encouraging and confirm that the use of conformal RT techniques, adapted to specific biological features, have the potential to improve the therapeutic ratio in intermediate risk PC patients. No significant financial relationships to disclose.

Author Disclosure: M.C. Ward, None; L. Lan, None; J.J. Beitler, Oakstone Medical Publishing, A. Employment; Community Cancer Education, Inc, D. Speakers Bureau/Honoraria; Educational Concepts Group, D. Speakers Bureau/Honoraria; ACR-Image Metrix, F. Consultant/Advisory Board; American College of Radiology, F. Consultant/Advisory Board; American Board of Radiology, F. Consultant/Advisory Board; Bayer Schering Pharma AG, F. Consultant/Advisory Board; United States Army Reserve, G. Other.

A commercially available liquid ionization chamber (PTW, Freiburg, Germany) was used in the commissioning of stereotactic radiosurgery beams for a Novalis Tx linear accelerator. The chamber has a small collecting volume (0.002cm3) yet providing a relatively high signal for its size. The chamber was attached to a solitary electrometer for output measurements, and to a water scanning system for PDD and beam profile measurements. The commissioning set consisted of output factors, percentage depth doses and off‐axis beam profiles for six collimator sizes ranging from 4mm to 15mm in diameter. The measured data was compared to both Gafchromic filmdosimetry measurements and to data from the literature. Output factors measured with the liquid ion chamber are in good agreement with film measurements (

Helical tomotherapy (HT) with daily imaging using mega‐voltage computed tomography for 3D image guided radiotherapy(IGRT). We present two techniques developed in our department to verify the integrity of the HT IGRT process. A phantom was constructed of two equally sized (5×10×10cm3) polystyrene blocks stacked on top of each other, each piece having a hole capable of receiving a small volume ionization chamber. A piece of Radiochromic film fits neatly in between the blocks. The phantom was CT scanned and the CT slices were transferred to the HT treatment planning system (TPS). The first procedure is used daily to test the image registration aspects of the IGRT process, and involves setting the phantom on the tomotherapy treatment unit table in an arbitrary position, imaging it, and performing image registration to determine what displacements are necessary to return the phantom to the planned position. A variation of this test is to place the phantom at a position incurring known displacements and ensuring the registration recognizes the shifts. The second procedure verifies the entire IGRT procedure, and includes the first procedure and the delivery of a treatment plan. An inverse plan is created to deliver simultaneously 2 and 3 Gy to 2 pre‐defined targets. The treatment plan can be setup as a QA plan in the TPS software, allowing for a detailed comparison of ion chamber measurements and film dosimetry to the planned dose distribution. We have found that these QA procedures adequately test the IGRT capabilities of our HT unit.

15598 Background: In curative radiation treatment of prostate cancer,the advent of 3DCRT has made a reduction in the incidence of normal tissue toxicities while optimizing tumor control. To optimize 3DCRT, the ICRU has published standard definitions of target volumes and organs at risk such that the tumor can receive the optimal dose with as little as possible dose to the organs at risk. However, the definition of the rectum as an organ at risk in radiation treatment of the prostate varies widely among institutions and so does the report of toxicities. We studied the effect of varying rectal contouring on rectal dose obtained from DVHs in a homogenous group of prostate cancer patients treated with hypo fractionationed radiation. Methods: 71 patients with favorable risk prostate cancer treated with a total of 66Gy in 3Gy/day fractionation.18 MV photons in a 5-field technique was used. None of the patients received hormonal therapy. Their treatment plans were archived and the rectum was re-contoured by a single investigator. 4 different contours were drawn to compare the rectal dose: i) the whole rectum from the anal verge to the recto sigmoid junction (WR); ii) the rectum from 1cm below the PTV to 1cm above (RPTV); iii) the rectal wall (i.e. the inner and outer rectal wall) from the anal verge to the recto sigmoid junction (RW); iv) the rectal wall from 1cm below the PTV to 1cm above (RWPTV) Results: There were significant differences in the median volume, minimum, mean rectal doses and dose to 50% of the volume, (p=0.0001). The whole rectum (WR) is having the lowest and the rectal wall with 1cm above and below the PTV (RWPTV) having the highest in all the parameters. The only parameter not significantly different among the 4 contours is the maximum rectal dose. Conclusion: the varied rectal contouring across different institutions is a possible reason for the broadly different reports of rectal toxicity after prostate irradiation. Our results suggest significant differences in rectal doses with varied contouring. Contouring the rectal wall only and limiting the volume to 1cm above and below the PTV confers the highest mean rectal dose. Comparison of rectal toxicity between institutions can only be meaningful if a consensual volume definition of the organ at risk is agreed upon. No significant financial relationships to disclose.

Introduction: Daily 2D ultrasound‐based target localization is routinely used for the patient setup in treatment of localized prostate cancer with external beam radiation therapy. A statistical analysis of a large data set can provide insight into target margin definition. Methods and Materials: Data from 387 patients treated between 2001 and the end of 2005 was retrospectively analyzed. Every patient in the study received daily pretreatment localization resulting in a total of 10,327 localizations, each comprising an isocenter shift in 3 directions: anterior‐posterior (AP), right‐left (RL), and superior‐inferior (SI). The mean shift for each direction for each patient was computed from daily treatment records, and a mean of the means was used in the analysis. The standard deviations (SD) for each direction were also computed for each patient and averaged. The data was statistically verified for normality. The mean shifts represent systematic uncertainties in the patient setup, and the SD represent the random variations. Results and discussion: The mean distances required for shifting the target to the required position were 6.1 mm posterior (4.4 mm SD), 2.1 mm superior (4.5 mm SD), and 0.5 mm right (3.6 mm SD). The 6.1 mm shift posterior is indicative of a non‐negligible systematic uncertainty. There are several sources of this uncertainty, the major one being the difference in patient setup and procedures between the CT simulation and the treatment room. Conclusion: Our study has revealed systematic inter‐treatment uncertainties. The results support the use of up to a 15 mm PTV margin to encompass the CTV for 95% of our sample, if the ultrasound localization system were not used.

Q4 patients had similar incidence of rectal toxicity ( 16%), but different DVH patterns. Compared with the DVHs in Q4, DVHs in Q2 demonstrate that more reduction of the overall dose (smaller coeff. of 1st PC) is needed to compensate for increased high dose volume (larger coeff. of 2nd PC), due to the serial structure of rectal tissue. 88% of the patients with severe toxicity grade 3 or higher have DVHs in Q1, thus this can serve as strong signature for clinically unacceptable plans.