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Purpose The appropriate object thickness to start using anti-scatter grids (grids) has not sufficiently investigated in previous studies, and thus we rigorously investigated the effectiveness of two generally used grids with grid ratios of 6 and 10 (G6 and G10) for different 50–200 mm thicknesses at tube voltages of 60–100 kV. Methods Acrylic phantoms with 30 × 30 cm2 and different thicknesses were used to measure the signal-to-noise ratio improvement factors (SIFs) of grids. To evaluate the infants’ conditions, field sizes of 225, 400, and 625 cm2 were also evaluated at 60–80 kV. In addition, the signal difference-to-noise ratio (SDNR) was used to evaluate tube voltage dependencies of grids for each thickness. Results SIF values exceeded 1.0 for ≥70 mm thicknesses and mostly exceeded 1.07 for the 100 mm thickness with 400 cm2 field size corresponding to a 1-year-old infant abdomen. The estimated dose reduction capabilities for a 1-year-old infant were approximately 15% using G10 at 70 and 80 kV. The tube voltage dependencies for grid use was almost not prominent for all conditions tested, except for some conditions that are not clinically realistic. Conclusions G6 and G10 can improve SNR for ≥100 mm thickness. The results from this work demonstrate approximately 15% dose reduction or image quality improvements at the same dose level for the use of G6 and G10 grids for 100 mm thickness, traditionally excluded from the recommended grid use conditions.

Introduction Aim of the present study is to evaluate homolateral and contralateral hippocampus (H-H, C-H, respectively) dose during Fractionated Stereotactic Radiotherapy (FSRT) or Radiosurgery (SRS) for brain metastases (BM). Materials & methods Patients with BM 3 months, were considered for SRS/FSRT (total dose 15–30 Gy, 1–5 fractions). For each BM, a Flattening Filter Free (FFF) Volumetric Modulated Arc Therapy (VMAT) plan was generated with one or two arcs. Hippocampi were not considered during optimizations phase and were contoured and evaluated retrospectively in terms of dose: the Dmedian, Dmean, D0.1cc and the V1Gy, V2Gy, V5Gy and V10Gy were analyzed. Results From April 2014 to December 2015, 81 BM were treated with FFF-FSRT/SRS. For the H-H, the average values of Dmedian, Dmean and D0.1cc were 1.5Gy, 1.54Gy and 2.2Gy, respectively, while the V1Gy, V2Gy, V5Gy and V10Gy values were 25%, 8.9%, 8.9% and 2.1%, respectively. For the C–H, the average Dmedian, Dmean and D0.1 cc were 0.7Gy, 0.7Gy, 0.9Gy, respectively, while the average values of V1Gy, V2Gy, V5Gy and V10Gy were 18%, 10.2%, 2.8% and 1.4%, respectively. Tumor dimension, tumor cranial-caudal length and the distance between BM and H-H were correlated to Dmedian, Dmean and D0.1cc. For C-H, only the distance from PTV was correlated with a dose reduction. Conclusion During FFF-FSRT/SRS, hippocampus received a negligible dose. Despite its clinical significance is still under evaluation, in patients with a long life expectancy, H-H should be considered during Linac-based FSRT/SRS.

Purpose To investigate lens dose reduction with organ based tube current modulation (TCM) using the Monte Carlo method. Methods To calculate lens dose with organ based TCM, 36 pairs of X-ray sources with bowtie filters were placed around the patient head using a projection angle interval of 10° for one rotation of Computed Tomography (CT). Each projection was simulated respectively. Both voxelized and stylized eye models and Chinese reference male phantoms were used in the simulation, and tube voltages 80, 100, 120 and 140 kVp were used. Results Dose differences between two eye models were less than 20%, but large variations were observed among dose results from different projections of all tube voltages investigated. Dose results from 0° (AP) directions were 60 times greater than those from 180° (PA) directions, which enables organ based TCM reduce lens doses by more than 47%. Conclusions Organ based TCM may be used to reduce lens doses. Stylized eye models are more anatomically realistic compared with voxelized eye models and are more reliable for dose evaluation.

To reduce the radiation dose to patients by optimizing oncological FDG PET/CT protocols.The baseline PET/CT protocol in our institution for oncological PET/CT examinations consisted of the administration of 5.18 MBq/kg of FDG and a CT acquisition with a reference current-time product of 120 mAs. In 2016, FDG activity was reduced to 4.44 and 3.70 MBq/kg and reference CT current-time-product was reduced to 100 and 80 mAs. 322 patients scanned with different protocols were retrospectively evaluated. For each patient, effective dose was calculated. The overall image quality was subjectively rated by the referring physician on a 4-point scale (IQ score: 1 excellent, 2 good, 3 poor but interpretable, 4 poor not interpretable). Image quality was quantitatively evaluated measuring noise in the liver.CT Results: Effective dose was progressively reduced from 9.5 ± 2.8 to 8.0 ± 2.3 and 6.2 ± 1.5 mSv (p 0.001). A mean dose reduction of 34.9% was achieved. There was a significant degradation of IQ score (p 0.05) and noise (p 0.001). Nevertheless, the number of poor quality studies (IQ score2) did not increase. PET Results: Effective dose was gradually reduced from 6.5 ± 1.4 to 5.7 ± 1.3 and 5.0 ± 1.0 mSv (p 0.001). Average dose reduction was 23.4%. IQ score (p 0.05) and noise (p 0.001) significantly degraded for lower activity protocols. However, all images with reduced activity were scored as interpretable (IQ score ≤ 3).A significant radiation dose reduction of 28.7% was reached. Despite a slight reduction in image quality, the new regime was successfully implemented with readers reporting unchanged clinical confidence.

Purpose The purpose of this study was to investigate the effects of routine exposure parameters on patient’s dose during neuro-interventional radiology procedures. Methods We scrutinized the routine radiological exposure parameters during 58 clinical neuro-interventional procedures such as, exposure direction, magnification, frame rate, and distance between image receptor to patient’s body and evaluate their effects on patient’s dose using an anthropomorphic phantom. Radiation dose received by the occipital region, ears and eyes of the phantom were measured using MOSkin detectors. Results DSA imaging technique is a major contributor to patient’s dose (80.9%) even though they are used sparingly (5.3% of total frame number). The occipital region of the brain received high dose largely from the frontal tube constantly placed under couch (73.7% of the total KAP). When rotating the frontal tube away from under the couch, the radiation dose to the occipital reduced by 40%. The use of magnification modes could increase radiation dose by 94%. Changing the image receptor to the phantom surface distance from 10 to 40 cm doubled the radiation dose received by the patient’s skin at the occipital region. Conclusion Our findings provided important insights into the contribution of selected fluoroscopic exposure parameters and their impact on patient’s dose during neuro-interventional radiology procedures. This study showed that the DSA imaging technique contributed to the highest patient’s dose and judicial use of exposure parameters might assist interventional radiologists in effective skin and eye lens dose reduction for patients undergoing neuro-interventional procedures.

Prostate cancer is a frequently diagnosed malignancy worldwide and radiation therapy is a first-line approach in treating localized as well as locally advanced cases. The limiting factor in modern radiotherapy regimens is dose to normal structures, an excess of which can lead to aberrant radiation-induced toxicities. Conversely, dose reduction to spare adjacent normal structures risks underdosing target volumes and compromising local control. As a result, efforts aimed at predicting the effects of radiotherapy could invaluably optimize patient treatments by mitigating such toxicities and simultaneously maximizing biochemical control. In this work, we review the types of data, frameworks and techniques used for prostate radiotherapy outcome modeling. Consideration is given to clinical and dose-volume metrics, such as those amassed by the QUANTEC initiative, and also to newer methods for the integration of biological and genetic factors to improve prediction performance. We furthermore highlight trends in machine learning that may help to elucidate the complex pathophysiological mechanisms of tumor control and radiation-induced normal tissue side effects.

Purpose the aim of this study was to evaluate the stability of image quality (IQ) metrics in pediatric 18F-FDG PET/MR acquisitions while decreasing statistical counts, mimicking an injected activity reduction. Methods 21 18F-FDG PET/MR whole body acquisitions performed on an hybrid scanner (Biograph mMR, Siemens Healthcare) were retrospectively reconstructed with the e7-tools package. The full tracer activity (FTA) list-mode data (3 MBq/kg, 5 min/bed position) were truncated at 4, 3, 2.5, 2 and 1 min, simulating lower tracer activity (LTA) images corresponding to 2.4, 1.8, 1.5, 1.2 and 0.6 MBq/kg. Subjective IQ (score 1 to 5) and number of detectable lesions were assessed by two expert nuclear medicine physicians. SUV metrics (SUVmean, SUVmax and SUVpeak) and semi-quantitative parameters as contrast-to-noise ratio (CNR), normalized noise in liver (NN), metabolic tumor volume (MTV) and total lesion glycolysis (TLG) were evaluated on each image. Results Results of subjective IQ evaluations are reported in Fig. 1; the assigned score decreased when reducing tracer activity, but remained acceptable till 1.5 MBq/kg. All the total 56 lesions were detected until 1.2 MBq/kg activity level, whereas 5 lesions were missed on the 0.6 MBq/kg image. Results of quantitative analysis are collected in Table 1 , espressed as a ratio of LTA and FTA values. Semi-quantitative parameters (except SUVpeak) and IQ metrics showed limited variation respect to the FTA image until 1.5 MBq/kg image. Differences were not statistically significant in LTA images down to 1.5 MBq/kg with pairwise paired Wilcoxon and t-tests. SUVpeak is the parameter less affected by dose reduction (average difference for all LTA images inferior than 2%). NN showed a constant increase while decreasing statistical counts. Conclusions An injected activity reduction up to 50% (1.5 MBq/kg) guarantees a stability in semi-quantitative parameters representing lesion detectability and tumor burden information.

Purpose We have evaluated, using a software tool for monitoring and tracking radiation dose, the radiation exposures in hybrid myocardial perfusion imaging (MPI) before and after the optimization of the SPECT/CT acquisition protocol. Methods and materials Examination data was collected from a SPECT/CT scanner Siemens Symbia T6 using Radimetrics version 2.6 (Bayer HealthCare, Whippany, NY). Data of MPI performed between 1st March 2016 and 1st March 2017 have been extracted from the DICOM header and Dose Report files produced by the scanner and stored in PACS. All analysis were made for exams in two days (TD) and in single day (SD). CTDIvol, DLP, SSDE, administered activity and Effective Dose were collected. A new optimized acquisition protocol was created changing CT parameters (mAs and pitch) and defining a new administered dose activity card with a reduction of the administered dose of about 18% for TD protocol and of only 4% for SD protocol because it was already well optimised. Examinations performed between 29th May 2017 and 30th November 2017 have been extracted and all dosimetric param eters were compared between old and new protocol. Results The dose reduction for CT part of the MPI was approximately 52% for all the parameters analysed (CTDIvol, DLP, SSDE, Effective Dose) both for TD and SD protocol. The dose reduction for SPECT part was aligned with the reduction introduced in the new administered dose activity card. In MPI study we have achieved, with the new optimized protocol, a total dose reduction of about 30% in TD exams and of about 24% in SD exams (see table below). Conclusion Using a software tool for monitoring and tracking radiation dose was possible to monitor, in real time, radiation exposure in SPECT/CT exams and analyze how to optimize the protocol to reduce effective dose to the patients.

Purpose Deep inspiration breath-hold (DIBH) has been routinely applied in left breast radiotherapy to reduce cardiac exposure. The purpose of this study was to compare deep inspiration breath hold and free breathing techniques (FB) in terms of heart and left-lung doses and to determine possible predictors of the dose reduction achieved with DIBH ( Δ DBH-FB). Methods Ten patients with left breast cancer have been treated with postoperative radiotherapy in Parma Hospital. For each patient both the FB and the DIBH planning CT were acquired. 3DCRT treatment plans using tangential field-in-field beams were developed for both FB and DIBH. FB and DIBH dose distributions were compared in terms of Dmean, V5Gy, V20Gy, V30Gy of the heart and V5Gy, V20Gy of the left-lung. Many geometric/anatomical parameters were measured in the FB condition: heart and left-lung volumes (Vheart, Vlung-L), maximum thickness of the same organs inside the tangential fields (dheart, dlung-L), axial and para-sagittal cardiac contact distances (CCDax, CCDps), maximum tangential distance between beam-entrance and beam-exit (dentrance-exit), maximum anteroposterior diameter of the chest. Results DIBH plans showed a significant reduction of Dmean (−60.9%), V5Gy (−82.5%), V20Gy (−93.6%) and (−95.8%) of the heart (p Δ DBH-FB were: Vheart (0.041 Conclusions This study confirmed how DIBH for left breast cancer treatment can decrease cardiac dose. The benefit of DIBH over FB strictly depends on chest shape, heart size and heart position. However, most of the parameters showed a weak correlation with Δ DBH-FB, so they cannot be used to effectively predict Δ DBH-FB. Only dheart seems to be a good predictor of Δ DBH-FB, but more cases must be included to confirm/reject these findings.

Background and purpose Helical tomotherapy (HT) can deliver highly conformal, uniform doses to the target volume. However, HT can only be delivered in a coplanar mode. The purpose of this study was to perform a dosimetric comparison of HT versus coplanar (cIMRT) and non-coplanar (n-cIMRT) beam arrangements on a conventional linear accelerator in a diverse group of brain tumors. Materials and methods A total of 45 treatment plans were calculated retrospectively for 15 cases. For each case, 3 different delivery techniques (n-cIMRT, cIMRT and HT) were used. The treatment plans were compared using the parameters of the target coverage (conformity index; CI) and homogeneity (HI) for the planning target volume (PTV) and the maximum and mean doses for organs at risk (OARs). Results Median HI and CI were the best for HT plans and the worst for cIMRT. The largest reduction of maximum dose for lenses and mean dose for both eyes was achieved for n-cIMRT plans. Mean dose for chiasm and the ipsilateral optic nerve were the lowest for HT. The contralateral optic nerve was most spared with n-cIMRT. For D 1% in the brain stem, there was no significant difference between HT and the IMRT plans. Conclusions Both HT and n-cIMRT are capable of producing conformal and homogeneous treatment plans with a good sparing of OARs. However, due to the non-coplanar capabilities of IMRT, n-cIMRT led to a superior dose reduction to the lenses.

Introduction All medical examinations using radiation for imaging must be optimized for both adult and paedriatric patients. To support the Medical Physicist in their work with optimization the Swedish Radiation Safety Authority (SSM) has developed a web-based tool, DosReg, for reporting local diagnostic reference level (LDRL) that in real time gives the user a feedback of how their LDRL stands in comparison to other clinics in Sweden as well to by the authority established diagnostic reference levels (DRL). Materials and methods The web-based tool DosReg has been developed during 2016 and 2017 for six different modalities: Computer Tomography, Nuclear Medicine, Mammography, Interventional procedures, Conventional Radiology, and Dental CBCT. With all DSD registrations are used examination protocols included, these protocols are then visible for other users to simplify their optimization process. When reporting LDRLs the user receives in real time a histogram that shows other clinics’ results as well as the national DRL’s for each modality and its procedures. Results DosReg for CT was the first modality to be released, September 2016, therefor has CT most registrations, with 351 as of December 2017. Several clinics in Sweden have used DosReg in their optimization work in cases where their initially reported LDRLs were higher than those of other clinics. There have been several cases where DosReg’s optimization tool has resulted in a dose reduction in the range of 50–80 per cent. Conclusions LDRL has been reported to SSM since 2002, but then the results where available 3-4 years after the reporting of the clinics. With this long lead-time the Swedish National DRL reports did not support to the user in their optimization of examinations and protocols. The use of DosReg with its immediate analysis of LDRL compared to other clinics will lead to substantially improved optimization of radiological protocols in Sweden, which in turn will result in less variation between different clinics in doses received by patients from the same kind of examination.

Purpose Evaluation of the doses to patients obtained during intraoral dental X-ray radiography procedure. Methods Gafchromic films were used for dose measurements in homemade PMMA head phantom reconstructed from CT scans of real patients. The absorbed doses to organs were evaluated at distinguished locations corresponding to the locations of certain organs in the head phantom. For the recalculation of the effective doses tissue weighting factors were applied. Results It was found, that the doses were ∼60% lower applying digital image detectors as compared to the analogue dental X-ray equipment. Absorbed doses measured using analogue technique was noticeable higher for the salivary glands and oral mucosa. Recalculated effective dose varied from the 0.5 to 5.5 μSv depending on the technical irradiation parameters and field size/collimation. Conclusions Performed investigation has shown statistically significant dose variations during intraoral dental X-ray procedure, that were related to the technical parameters of irradiation. This indicated an important issue of possible patient’s dose reduction in intraoral dental X-ray radiography, which could be managed when selecting appropriate set of technical parameters for the examination. Some recommendations regarding patient’s dose reduction are also provided.

Purpose To present a detailed optimization process of automated radiation dose tracking data in standard CT chest examination for multi detector computed tomography (MDCT). Tasks resulting from such a goal are related with correct processing of collected data, deep analysis and interpretation of the data, identification of incorrect clinical practice and to compare the results with another radiology department practice. Materials and methods A single retrospective study was conducted involving regular enrolled patients for routine CT chest examination in Acibadem City Clinic Tokuda Hospital. All MDCT exams were performed on a 64-detector row computed tomography (LightSpeed VCT, GEHC) without any iterative reconstructions. The tube voltage (kV), slice thickness (mm), rotation time (s/rot) and table speed (mm/s) were periodically altered parameters according to radiation dose reduction without compromising the quality of the image. In the course of the study a web-based dose management software was used (DoseWatch, GEHC) which allows all MDCT chest examinations to be properly tracked and radiation doses to be collected. Results After the step by step optimization the CTDIvol and DLP were decreased to 9,20 mGy and 373,77 mGy.cm respectively while maintaining good diagnostic image quality. In comparison with Acibadem City Clinic Cancer Centre (Optima CT660, SS40 ASIR, GEHC) these values are slightly higher which is explained by the fact that in Optima CT660 an iterative reconstruction algorithm was systematically used (CTDIvol6,43 mGy and DLP 265,2 mGy·cm). Conclusions The CT chest radiation dose was reduced with 56% (CTDIvol) and 63% (DLP) with preserving the diagnostic image quality. A significant CT chest dose reduction was achieved even without using any iterative reconstruction algorithm.

Purpose The aim is to compare the Average Glandular Dose (AGD) of a photon counting detector (PCD) digital breast tomosynthesis prototype with those of a conventional tomosynthesis system (CTS). Methods After ethical committee approval, some consenting women older than 40y with highly suspicious breast finding at clinical or imaging evaluation (BIRADS 4c-5) underwent bilateral 2-view tomosynthesis with a CTS and a PCD prototype before breast biopsy. AGD and breast thickness were recorded and compared. To verify the correspondence between displayed and measured dose, a set of measurements was done following the EUREF protocol. Furthermore, entrance surface dose to the contralateral breast was evaluated with 21 thermoluminescent dosimeters placed on a anthropomorphic phantom Alderson RANDO simulating an adult female. Results 16 women (mean age 70 y; 44–82 y) underwent bilateral 2-view tomosynthesis with both systems. The mean RCC displayed AGD was 0.75 mGy for PC and 1.61 mGy for CS with a 51% mean AGD reduction. The mean RMLO AGD was 0.77 mGy for PC and 1.81 mGy for CS with a 57% mean AGD reduction. The mean LCC AGD was 0.72 mGy for PC and 1.5 mGy for CS with a 50% mean AGD reduction. The mean LMLO AGD was 0.75 mGy for PC and 1.72 mGy for CS with a 55% mean dose reduction. Also considering small compression differences, we found a minimum of 50% dose reduction and a correlation between dose reduction and breast thickness: large breasts seem to benefit more from PCD AGD reduction. The doses delivered to the contralateral breast with the PCD device were up to 85% lower than that delivered with the CTS. The highest differences were relative to the nipple area. Conclusions Our results demonstrate that PCD tomosynthesis allows a significant dose reduction especially in large breasts and a sensible reduction of dose delivered to the contralateral breast.

Objectives To verify the dosimetric accuracy of treatment plans in high dose rate (HDR) brachytherapy by using Gafchromic EBT2 film and to demonstrate the adequacy of dose calculations of a commercial treatment planning system (TPS) in a heterogeneous medium. Methods Absorbed doses at chosen points in anatomically different tissue equivalent phantoms were measured using Gafchromic EBT2 film. In one case, tandem ovoid brachytherapy was performed in a homogeneous cervix phantom, whereas in the other, organ heterogeneities were introduced in a phantom to replicate the upper thorax for esophageal brachytherapy treatment. A commercially available TPS was used to perform treatment planning in each case and the EBT2 films were irradiated with the HDR Ir-192 brachytherapy source. Results Film measurements in the cervix phantom were found to agree with the TPS calculated values within 3% in the clinically relevant volume. In the thorax phantom, the presence of surrounding heterogeneities was not seen to affect the dose distribution in the volume being treated, whereas, a little dose perturbation was observed at the lung surface. Doses to the spinal cord and to the sternum bone were overestimated and underestimated by 14.6% and 16.5% respectively by the TPS relative to the film measurements. At the trachea wall facing the esophagus, a dose reduction of 10% was noticed in the measurements. Conclusions The dose calculation accuracy of the TPS was confirmed in homogeneous medium, whereas, it was proved inadequate to produce correct dosimetric results in conditions of tissue heterogeneity.

A new GE Discovery CT590 RT scanner 1] was purchased for a Radiotherapy Department in January 2017. During the commissioning process it was noted that the system had a number of new technological capabilities. These included dose reduction options and post processing software to reduce certain artifacts. ASiR (Adaptive Statistical Iterative Reconstruction), MAR (Metal Artifact Reduction), extended FOV (Field of View) and extended Hounsfield units were some of the new technologies available. From a physics perspective the availability of such technologies presented some interesting challenges – both during the commissioning period and in deciding how best to adapt clinical protocols so that the most modern advances in CT could be used in a safe and accessible fashion. The techniques were tested to assess their impact on image quality, dose to patient and compatibility with the treatment planning system (Elekta’s Monaco in our case). Most of the options have now been implemented clinically and results have been positive. Patient doses are approximately 30% lower than previously, thanks to ASiR. Image quality remains good and results for imaging patients with implants are markedly better due to MAR. The use of extended Hounsfield units is the one area that has proved difficult to move forward with due to incompatibilities with our treatment planning system.

With the advent of the transposition of the new Basic Safety Standard into Irish Law there is an imperative on all health providers using ionising radiation to record, provide and optimise radiation dose to patients and accordingly to staff. Radiation dose management tools (RDMT), such as DoseWatch, Radimetrics, etc., are beneficial in aiding Medical Physics Experts on a day to day basis responding to individual patient doses (micro level) and Radiation Protection Advisors will use it on a population based perspective (macro level). In our hospital, GE DoseWatch is installed on Cath Labs, IR, CT and DR (high dose or high-volume modalities). We have recently replaced all of these systems and the RDMT has proved effective for establishing Dose Optimization Teams (DOT), comprising physics, radiologists and radiographers to set dose alert levels and to highlight opportunities for dose reduction. This study will show the advantages of a RDMT over a manual entry system and what that means for both patients and staff exposure, over time. This study reviews the effectiveness of DOTs. This study is undertaken over the past few months for the most frequent scans, using several modalities and results are then reviewed in conjunction with reports such as the COMARE 16th Report and SIR Guidelines 2009. We also undertook a holistic review of patient and staff doses in the Cath Lab, in concurrence with a recent position document published by the EHRA, regarding staff with reproductive potential and during pregnancy.

Purpose As low as reasonably achievable (ALARA) based protocols have been widely implemented to significant effect in diagnostic computed tomography (CT) scans for paediatric patients, but investigation of dose reduction techniques in paediatric cone beam CT (CBCT) IGRT are lacking. The purpose of this review is to report the level of dose from paediatric CBCT, the implications of this, and to investigate the potential for dose reduction. Methods A search and review of published studies investigating kV CBCT dose (in-field and out-of-field); long term effect of kV CBCT dose and dose reduction interventions was carried out. Dose studies included paediatric radiotherapy patients aged zero to nineteen years old, adult radiotherapy patients, and both paediatric and adult anthropomorphic phantoms. Results Nineteen articles were selected for review. Over a course of treatment using daily CBCT, the cumulative imaging dose can be comparable to the dose of a single treatment fraction and has the potential to be greater than peripheral doses from IMRT techniques. A number of dose reduction interventions have been proposed, which include: reducing tube energy and current; shielding radiosensitive structures; reducing the scan length/volume; reducing scan frequency; reducing rotational angle and using bow tie filters. Conclusion Paediatric patients are at an increased risk of developing second malignancies with daily CBCT. Particular consideration must be given to the use of CBCT in very young; female patients and close to radiosensitive structures. The imaging dose to these patients should be minimised, provided the image quality is sufficient for verification purposes.

Purpose Following publication of Canada’s first national survey of Computed Tomography (CT) in 2016 [1] , Diagnostic Reference Levels (DRLs) are now available for select head and trunk examinations of both pediatric (0–3, 3–7 and 7–13 yrs.) and adult ( ≥ 19 yrs.) patients. The analysis performed also included additional investigation into the effect of scanning mode (axial or helical), contrast use (C+ or C−) and inclusion of dose reduction methods (Fixed or Dose Reduction (DR)). The intent was to investigate, at least semi-quantitatively whether this can help identify key protocols that could benefit from further optimization. Methods The Canadian CT survey was adapted from the 2003 CT survey performed in the United Kingdom [2] . In close collaboration with all Canadian provinces and territories, data was collected from approximately 75% of all CT scanners in Canada and ultimately provided machine, dose index, age, mass and cross-sectional dimension information from 24 280 individual patient sequences. For each patient sequence, an algorithm also scored and confirmed the scan mode, use of contrast and use of DR. CTDIvol data for each examination type (group) could then be sub-divided and compared with 8 sub-group DRLs or CTDIvol percentiles. E.g. Adult Head DRL versus Adult Head, Helical, C+ and Fixed current DRL, and so on. A custom graphic plot was created in order to clearly compare group (or examination) with sub-group dose index distributions. Results In almost all cases, the use of a fixed (non-modulated) current (mAs) showed higher CTDIvol values, across sub-group DRLs (75th percentile of CTDIvol sub-group data). Indicating that those protocols may potentially benefit most from dose reduction activities. Conclusions DRLs are an important part of dose reduction initiatives, and with some additional analysis, clear indicators can be produced that provide guidance on where to initiate any protocol review for potential dose reduction.

Purpose Increasing number of breast cancer women receiving post-mastectomy radiation therapy (PMRT) had immediate two-stage tissue expander (TE)/implant for breast reconstruction. TEs with metallic port become popular due to convenient saline injection. Previous studies showed 10–30% actual dose reduction under tangential beam arrangement caused by high Z material. This study was conducted to quantify the dosimetric effects in the region of the metallic ports using helical tomotherapy. Methods Bolus with 0.5 cm thickness was placed on the surface of rando-phantom simulating post mastectomy pectoralis major and skin beyond as layer M. TE with different capacities (100 cc, 150 cc, 200 cc, 250 cc, and 300 cc) was placed under layer M simulating treatment condition. 1 cm bolus was placed on layer M for routine PMRT technique. Artifact removement and heterogeneity correction of simulation image were performed via tomotherapy planning system. Two tomotherapy plans were generated for each capacity of TE: Plan A) artifact removed; Plan B) artifact removed plus CT electron density 1 was assigned to the metallic port region. Radiochromic films were used for absolute dose measurement at three locations: 1) surface of layer M; interface between 2) TE and layer M 3) bottom of TE. Film QA was utilized for dose analysis. Results The distance between TE top and metallic port is range from 0.7 for small capacity to 1.0 cm for large capacity. The distance between metallic port and TE bottom is range from 0 to 1.4 cm along with increasing capacity. The measured dose at layer M surface was range from −0.53% to −8.9% and −0.39% to −8.29% for plan A and B. The measured dose at interface between TE and layer M was range from 1.09% to −6.01% and 1.92% to −6.09% for plan A and B. The measured dose at bottom of TE was range from −0.14% to −7.57% and 1.08% to −5.37% for plan A and B. Conclusions The actual dose under helical tomotherapy for patient with metallic port breast tissue expander is acceptable comparing to tangential technique. TEs with 100 cc and 150 cc have higher metallic port position reproducibility. Helical tomotherapy is a suitable treatment technique for patient with breast tissue expander with metallic port.

Purpose The aim of this study was to describe and analyze a long term project of dose management from the beginning to results obtained. Methods and materials In late 2014 our radiology department in agreement with the hospital’s leadership decided to implement a dose management program with the help of a software (Dosewatch™) and a training program.The number of radiological equipments initially monitored were 2 CT, 1 CT-PET, 1 MX and 2 RX. It was created a dose team, made by a radiologist, a physicist (team leader) and a technician; the training program started at the beginning of 2015, regarded initially the 2 CT equipments, and was based on four topic elements: standardization of protocols used, justification on dose levels that exceeded a fixed dose threshold, optimization of acquisition protocols to decrease doses and communication of obtained results at the hospital community and to the public/patients. To actuate this program we defined an action plan in which it was clearly evident what to do, who is responsible for, and a date dead line for each step. Nowadays the dose management program is applied to four CT and one PET/CT equipments. Results The first step was to map the number of protocols that we used and to train all technicians about the dose alert justification procedure. This initial part had permitted to eliminate a certain number of “double” protocols and to mapped the remnant ones. From data analysis we noted that on one CT equipment the 3 protocols that were over DRL in terms of DLP and CTDI were Head, Thorax and Abdomen: the dose team decided to change acquisition protocol by lowering current and changing collimation. These protocols optimization led to a mean reduced doses of about 25% in terms both of DLP and CTDI. Conclusion Long term results in terms of dose reduction were very promising; moreover the most important things were the dose team creation and the implementation of a job methodology that could lead to optimize patients absorbed doses.

Purpose To assess the potential dose reduction to the thyroid and breasts in chest CT, using organ-based tube-current modulation (OBTCM). Posterior organs in the field of view were analyzed and overall lifetime attributable risk (LAR) of cancer induction and mortality was evaluated. Methods With OBTCM, the exposure is lower when the X-ray tube passes over the anterior surface of the patient. In this way, the breast doses can be limited. However, to preserve image quality, the total exposure during one rotation has to be equal to the exposure of scans without OBTCM enabled. Therefore, the tube-current is higher during posterior projections. In this study (Jan 2015–Dec 2016), the location of the breasts with respect to the reduced tube-current zone was determined. Using Monte-Carlo simulations, patient-specific dose distributions of chest CT scans were calculated for 50 female patients (mean age 53.7 y ± 17.5, range 20–80 y). The potential dose reduction of OBTCM was assessed. In addition, simulations of clinical OBTCM scans were made for 17 female patients (mean age 43.8 y ± 17.1 y, range 20–69 y). LAR of cancer incidence and mortality was estimated according to BEIR-VII. Image quality (IQ) between standard and OBTCM scans was compared. Results No women had all breast tissue within the reduced tube-current zone. Clinical observed dose reductions were 18% (thyroid) and 9% (breasts) whereas lung, liver and kidney doses were 17%, 11% and 26% higher. Overall, LAR for cancer incidence was not significantly different (p = .06) between conventional and OBTCM scanning. IQ improved with OBTCM (p Conclusions The potential benefit of OBTCM to the female breast in chest CT is overestimated due to a limited reduced tube-current zone; despite a 9% dose reduction to the female breast, posterior organs will absorb up to 26% more radiation, resulting in no reduction of radiation induced malignancies.

Purpose Left-sided breast radiotherapy is associated with increased risk of coronary artery disease. Active Breathing Coordinator (ABC) reduces radiation dose to the heart and preserves local control in patients with left breast cancer. The aim of this study is to estimate the dose reduction to the heart and its inter-fraction variation in moderate deep inspiration breath hold (mDIBH) breast radiotherapy using ABC (Elekta). Methods Ten patients with left-sided breast cancer with tangential radiotherapy plans and ten patients with VMAT plans performed using to Monaco (Elekta) TPS, where included in the study. All the patients were trained on ABC procedure to enhance patient compliance and to determine individual (mDIBH) levels, which was set at 70–80% of maximum inspiratory capacity. During simulation two sets of CT images were acquired for each patient, one with mDIBH with ABC system and the other with free breathing. Treatment plans were performed for both scans and the mean dose to the heart was recorded. Treatment was performed using the ABC system. 200 cone-beam CT (CBCT) scans were acquired for all patients investigated throughout their course of treatment to take into account inter-fraction patient set-up inaccuracies. CBCTs were exported to Monaco TPS for registration and mean heart dose determination after the application of the original patient plan. Results For all patients evaluated, compared to free breathing, mDIBH with ABC significantly reduced mean dose to the heart by 20% or greater independently of the planning technique (tangential fields or VMAT). This reduction remains the same with minor differences (on average 1 cGy per fraction) throughout the treatment course. Conclusion Moderate deep inspiration breath hold (mDIBH) breast radiotherapy using ABC (Elekta) can significantly reduce mean dose to the heart. Variation in mean heart dose was minor and mean dose remains significantly reduced throughout the treatment course without being affected by inter-fraction variations.

A procedure previously been described that has an effect on the image quality and radiation dose of conventional radiographs already at the time of acquisition [Paech A, Schulz AP, Hahlbrauck B, Kiene J, Wenzl ME, Jürgens C. Physical evaluation of a new technique for X-ray dose reduction: measurement of signal-to-noise ratio and modulation transfer function in an animal model. Physica Medica 23 (2007):33-40]. This development is using X-ray sensitization by optical re-exposure. Aim of this study was to establish if the results of optical re-exposure measured with SNR and MTF also meant that the subjective quality of 50% dose-reduced and re-exposed radiographs of bony structures was equal or better than conventional full dose radiographs of the same area. Freshly slaughtered anterior shoulders of lambs served as the animal model. A comminuted fracture in the middle of the shaft was artificially produced. After taking a normal exposed reference image, dose-reduced, five underexposed images were prepared. These underexposed X-rays were then optically re-exposed for a defined period of time before development. The subjective changes in the image quality (information loss or gain) of the images were compared to the reference image and evaluated by 16 physicians with large experience in diagnosis of orthopedic radiographs. The evaluation of the observers scoring showed a significant decrease in the subjective image quality regarding the detail recognition in all images apart from the images re-exposed for 60s. In conclusion, there is a possibility of reducing the collective radiation dose whilst keeping a high degree of diagnostic reliability. Film sensitization provides a technically simple and inexpensive procedure, which can be easily integrated into common film development processes and could considerably reduce patient radiation exposure as well as improve image quality and thus detail recognition.

The continuous evolution of computed tomography (CT) technology has allowed for wider clinical CT utilization. However the increased radiation doses associated with CT have raised concerns about the risk of carcinogenesis among Radiation Protection Authorities, health professionals and patients. Although the benefit of a justified CT examination by and large outweighs the risk, optimization of the procedure is essential to further this risk. Moreover CT manufacturers have developed several dose reduction tools and dose alert platforms to modulate and record the radiation doses administered to patients. The scope of this presentation is to outline the significance of optimization in CT, to describe CT parameters, scanner dose output indices and the methodology to reduce dose without compromising diagnostic quality. Learning Outcomes: Following the presentation, participants will be able to: 1. Demonstrate the difference between CT scanner output and effective dose. 2. Fine-tune dose reduction parameters ensuring ALARA and according to clinical requirements (i.e. mAs and kV modulation, section collimation, detector array selection, pitch). 3. Distinguish between noise reduction iterative reconstruction algorithms and dose. 4. Correlate CT dose indices to national DRLs. 5. Participate in CT protocol design and continuous quality improvement programs. 6. Promote Radiation Protection Campaigns (i.e. Image Wisely, Image Gently, Eurosafe Imaging, RPOP). No disclosures.

Purpose To highlight a novel methodology for patient dose management of radiological examinations in a regional public health framework. Material and methods DoseWatch-GE is a multivendor and multimodality patient dose management software for radiological examinations. The framework in this study is a Region of Spain with 10 hospitals and 1.5 Million population. Dose indexes and examination protocols are recorded in individual patient files. Our methodology is divided into three foundations: (1) standardization of protocols, (2) Setting of Regional Diagnostic Reference Levels (RDRL), and (3) dose optimization. Results Nowadays, 60 devices from 10 public hospitals are monitored: 13 CT’s, 9 Interventional, 9 Mammo and 23 conventional. Every month the system is collecting approximately: 9000 CT, 800 Interventional, 2500 Mammo and 33000 conventional examinations. Standardization of protocols must be the first step because examinations nomenclature is highly variable among both manufactures and hospitals. We have established a master protocol list as reference for local protocols, thus allowing coherent data analysis. RDRL can be established and updated thanks to the massive amount of data available from a wide variety of equipment. This data might serve for future national DRL, currently not available. Dose optimization is supported by a multidisciplinary Dose Committee (radiologist, medical physicist, technologist, administration and application specialists), actively searching for dose reduction opportunities, based on comparative analysis with international DRL’s and among similar equipments. Conclusion We conclude that dose management systems might play an important role in the radiological patient safety task. Disclosure None.

Introduction Spot scanning proton therapy (SSPT) treatments suffer from poor conformity, especially at low energy, due to increased lateral spot size, which is further increased with the patient scattering. The University of Iowa Hospitals and Clinics recently proposed a dynamic collimation system (DCS) for SSPT, which is capable of providing spot-by-spot collimation. The purpose of this study is to quantify by simulations improvement in target conformity from the use of the DCS, in brain and head and neck tumor treatments. Methods Two spot scanning proton therapy delivery systems (Universal Nozzle, UN, and Dedicated Nozzle, DN – IBA company) with median spot sizes of 5.2 mm and 3.2 mm over a range of energies from 100 to 230 MeV were considered. Uncollimated and collimated plans were calculated with both UN and DN beam models implemented within our in–house treatment planning system for five brain and ten head and neck datasets of patients previously treated with spot scanning proton therapy. The DCS was simulated as close as 5 cm from the patient surface. The average reduction of the mean dose to the 10-mm ring surrounding the target between the uncollimated and collimated plans was calculated for the UN and DN. Target conformity was analyzed using the mean dose to 1-mm thickness rings surrounding the target at increasing distances ranging from 1 mm to 10 mm. The dose reduction to some organs-at-risk was also quantified. Results The average reductions of the 10-mm ring mean dose for the UN and DN plans were 13.7% (95% CI: 11.6–15.7%; p p p p Conclusions According to these simulations, the DCS improved the target conformity for both the UN and the DN, and offered better dose reduction to OARs [1] , [2] , [3] .

A diagnostic or interventional X-ray examination of a pregnant patient is sometimes considered to be necessary. In these cases, conceptus dose estimation is needed to assess radiogenic risks to the unborn child. During extra-abdominal examinations, the unborn child is exposed to scattered radiation and in most cases its dose is lower than 1 mGy. A detailed embryo/fetus dose evaluation is not needed for these examinations. Abdominal and/or pelvis X-ray examinations may deliver higher radiation doses to the conceptus. An abdominal CT examination performed on the mother is associated with an embryo/fetus dose of about 10–25 mGy. However, this is only a typical range of dose values. The actual dose depends on factors such as exposure parameters, x-ray tube filtration and use of dose reduction tools such as automatic exposure control. Doses to the unborn child below 100 mGy should not lead to therapeutic abortion. The risk to the embryo/fetus for stochastic effects is assessed on the basis of radiation dose using appropriate conversion coefficients provided by international organizations. Several methods have been developed to estimate doses to unborn children from X-ray examinations. CODE (COnceptus Dose Estimation) is a free web-based software tool (uploaded on embryodose.med.uoc.gr) developed for the estimation of conceptus radiation dose and risks in case of: a) pregnant patients subjected to radiological examinations and b) pregnant employees exposed during fluroscopically guided interventional procedures.

Introduction Optical systems provide both patient setup verification and intrafraction motion detection and enable respiratory gating treatment procedure. Purpose Aim of this work is the evaluation of a deep inspiration breath-hold (DIBH) technique guided by an advanced optical system in terms of dosimetric benefits and positional accuracy. Materials and methods The CatalystTM (C-RAD Sweden) can manage respiratory gated treatments by enabling visualization of the respiratory pattern and direct beam control. Forty left side adjuvant radiotherapy patients were included in this study. Standard 3D conformal radiotherapy technique with tangential beams and 50 Gy dose prescription were used. For each patient a free breathing (FB) and a DIBH treatment plans were elaborated and dose volume histograms were compared. Treatments were performed in DIBH. Interfraction and intra-fraction variability were quantified in mean and SD translations and rotations displacements over all the treatment fractions. Results A significant dose reduction in Heart Mean Dose (1,3 Gy FB vs 0,4 Gy BH), and LAD mean dose (10,7 Gy FB vs 2,0 Gy BH) was achieved by DIBH technique. DIBH plans provided a better PTV coverage (V 95% 88,9% FB vs 92,6% BH) and no difference in Lung V10, V20 and Dmean. Inter-fraction variability after setup correction was lower than 1 mm and 1° for translations and rotations respectively. Intra-fraction variability was 2.1 mm in translations and 1° in rotations. Conclusion Significant reduction of hearth and LAD mean dose and a limited inter-fraction and intra-fraction variability were obtained by DIBH treatments guided by an optical system.

Introduction The potential heart damage in left-sided breast cancer radiotherapy is well known; nevertheless the biological mechanisms are only partially understood. Radiotherapy guidelines impose dose-volume constrains for the whole heart but newer data propose that excessive dose to the Left Anterior Descending artery (LAD) endothelium may cause cardiac toxicity. Purpose To evaluate the dose-volume data for the whole heart and LAD and performed dose distribution optimization based on a LAD dose constrain. Materials and methods 11 left-sided breast cancer patients were retrospectively selected for this study. All patients underwent 3D-CRT with 2-field tangential irradiation technique. The dose prescription was 50–60 Gy in 2 Gy/fraction. LAD was delineated for all patients and DVHs were calculated and compared. Every plan was acceptable regarding the V25 Results The measured D mean was 2.9 Gy to the heart and 24.8 Gy to the LAD. Volumes below 1.5% of the heart received dose ⩾50 Gy in 6 patients (55%). LAD D mean in 6 cases (55%) was > 20 Gy. Plan optimization based on LAD dose reduction was possible for 5 cases where D max reduced 13.6-38.3% and D mean reduced 35.1–52%. Conclusion In left-sided breast cancer 3D-CRT, even when the DVH constrain is met for the whole heart; the LAD receives significant higher doses. In the case that LAD dose is responsible for cardiac toxicity, new dose constrain should be added for plan optimization.

Introduction Multi detector CT (MDCT) X-ray systems provide high quality paediatric imaging. However, the last years, concern has been expressed on radiation exposure to children. Very few surveys depicting paediatric exposure from MDCT s are available. Purpose To shape the status of radiation dose in children from MDCT practice in a dedicated paediatric hospital in Greece. Materials and methods This was a retrospective study in a 160 bed paediatric hospital equipped with a Philips Brilliance 16 CT scanner installed in 2010. Patient data and acquisition parameters were recorded for CT studies of head, abdomen, chest and spine and were divided in three age groups (1–5 years, 5–10 years, 10–15 years). The dosimetric results were reported in terms of volumetric CT dose index (CTDIvol) (mGy), dose length product (DLP) (mGycm), and total DLP for multiphase studies. The results were compared with adult national DRLs and paediatric European published data. Results Data were collected from 97 MDCT examinations and included 39 head CTs, 12 abdomen CTs, 20 chest CTs and 26 spine CTs. Acquisition parameters used were according to age for head CTs and weight-dependent for the other scans. Spiral or axial scan depended on anatomic area and on the radiologist on duty. Multiphase studies accounted for 10% of patient sample, 80% of these in the abdomen region. For the three age groups, CTDIvol, DLP and total DLP average values were significantly lower than adult national DRLs, although they increased with age, and were in accordance with published paediatric European data. Conclusion Initial data showed that use of protocols tailored to patient’s age or weight results in significant dose reduction. Use of standardized CT protocols should be encouraged.

Introduction Despite the use of bismuth shields to reduce dose to eye lens and thyroid from CT scans has been reported efficient and recommended, there are conflicting opinions regarding breast bismuth shielding during thoracic CT. Purpose To assess breast dose reduction and diagnostic quality degradation associated with the use of bismuth shields in women undergoing coronary CT angiography (CCTA). Materials and methods Standard prospective and retrospective 256-slice CCTA exposures with and without breast bismuth shielding were simulated on a series of female anthropomorphic mathematical phantoms of varying size and 45 voxelized phantoms corresponding to patients subjected to CCTA using Monte Carlo methods. Bismuth shielding-induced reduction in dose to breast, lung and esophagus was determined. The effect of breast and thorax size on reduction efficiency was investigated. Shielding-related diagnostic quality degradation was assessed by two experienced radiologists in the series of 45 female patients subjected to CCTA. Results Breast bismuth shielding was found to reduce dose to breast, lung and esophagus of anthropomorphic phantoms by 22–33%, 12–21% and 13–20%, respectively. Corresponding mean reduction efficiency determined in voxelized phantoms of 45 CCTA patients was found 8–24%. The diagnostic quality degradation associated with the use of breast bismuth shields during CCTA was found to be unimportant. Conclusion Despite the breast dose reduction efficiency of bismuth shielding during CCTA was found lower than corresponding values reported in literature for thoracic CT, the use of breast bismuth shields in CCTA is not to be discouraged since associated diagnostic quality degradation is inconsequential.

Purpose To evaluate the patient dose in computed tomography (CT) examinations and contribute to the stablishment of dose reference levels using a dose management system. Material and methods Data from 5 CT hellical multi-slice scanners (16–128 slices) in 3 public hospitals were surveyed (4 Siemens, 1 General-Electric) during 3 months. Three typical examinations were selected: head (1445 cases), thorax (579 cases) and abdomen-pelvis (1055 cases). GE-Dosewatch was used to register patient dose indexes, CTDIvol and DLP, and the technical parameters. The statistical analysis was done in Matlab. Results Both the CTDIvol and the DLP data approximate well to a log-normal distribution function whereas the scanned length fits better to a normal distribution. Median CTDIvol of head scans ranged 33.0–63.8 mGy, thorax 6.7–9.7 mGy and abdomen-pelvis 10.0–12.1 mGy. Median DLP of head scans ranged 527–1162 mGy cm, thorax 218–334 mGy cm and abdomen-pelvis 383–453 mGy cm. We noticed that same CT model scanners use different technical examinations parameters, resulting in dose variations up to 30%. A dose optimization process was initiated to standardize the scanning protocols, thus expecting a dose reduction around 20% in some cases. Patient size selection was not deemed necessary due to the high number of cases per examination, more than 100. A drawback of this massive data is the presence of extreme outliers, and thus data filtering is mandatory. Conclusion Dose management systems provide an efficient tool to overview and optimize radiological dose levels. Disclosure None.

Radiation originated from CT examinations has been identified as the major contributor of radiation dose to patient population from medical purposes in the United States. Therefore, there is a great concern regarding the risk associated with radiation exposure from these examinations in both children and adults. Although effective dose has been the most commonly used dose metric when reporting the risk related to a given type of procedure, it has been recently suggested that the radiation dose delivered to specific radiosensitive organs should be determined. Physical anthropomorphic phantoms and mathematical models have been widely used for this purpose. However, the variability of human anatomy may be significant, especially for pediatric patients. In addition, modern CT scanners are equipped with automatic tube current modulation systems (TCM), which allow for images at reduced patient radiation dose. These systems modulate the tube current depending on the patient body size. Consequently, the dose reduction due to the activation of the TCM will considerably vary for patients with different body habitus. Methods based on voxelized patient models have been developed to individualize patient radiation dose. Size-specific, scanner-independent ‘CTDIvol to organ’ dose conversion factors have been produced to estimate organ doses from various CT examinations. Patient’s sex, body status and TCM settings should be taken into account in patient specific CT-dosimetry. In this presentation methods developed to determine individual-specific organ doses from CT examinations, based on patient specific models, will be reviewed.

Introduction There is a much concern regarding occupational radiation dose of the interventional cardiologists with numerous papers presenting their results during the last 10 years. Purpose A 9-years follow-up of interventional cardiology personal dosimetry records was done in one department with two angiography units in a big university hospital in Bulgaria. Materials and methods Personal dosimetry records of twelve cardiologists were recorded using personal thermoluminescent dosemeters worn under their lead aprons. Different analysis of the number and complexity of procedures was done. Results The number of procedures performed in the department increased from 3018 in 2007 to the maximum of 3256 in 2008, with a minimum of 2235 in 2012, followed by a new increase to 2440 in 2013, and reaching a constant level of approximately 2310 patients during the last two years. A number of individual doses in the range of 15.5–19.5 mSv per year were recorded from the dosemeter under the apron, close to the regulatory dose limit of 20 mSv per year. Strong increase in individual doses for a number of cardiologists was observed during the last 5 years, following the changes in the organization of the department and the team members. The reason for such a trend is in the uneven distribution of the number of patients between the cardiologists and the uneven distribution of the most complicated interventional procedures. Conclusion The observed trends prompted actions on better organization and control, and a program for increasing the radiation protection awareness was introduced in 2014, which resulted in 2 fold decrease in personal doses for some of the staff members. The most effective actions involved increased radiation protection awareness and training, steps for patient-dose reduction using all available dose reduction options of the angiography equipment and the systematic use of radiation protection tools including ceiling-suspended protective screens.

Introduction Head radiography comprises a common examination protocol in clinical routine. Diagnostic decisions are associated with the detected injuries. Consequently, image quality of the x-ray examinations is essential for the early diagnosis and appropriate treatment, especially for the sensitive population of children. Therefore each examination protocol should be appropriately optimized to achieve images of high diagnostic quality and minimum radiation burden to patients. Purpose To optimize the radiographic technique for head examination protocols in pediatric patients. Methods and materials Three anthropomorphic phantoms (ATOM Phantoms, CIRS, Norfolk, VA) representing the average individual as neonate, 5-year-old, and 10-year-old child were employed. The phantoms were subjected to head radiographs using a state of the art digital radiographic system (AGFA GAEVART, DX-D600) for various tube voltages (50–125 kVp) and current settings (0.2–50 mAs). For each exposure, image quality objective parameters, including contrast to noise ratio values (CNR) were estimated to determine figure of merit (FOM) in the optimization process. The technique associated with the higher CNR value for the same FOM was considered as the optimized method. Results Dose reduction of up to 88% was recorded for the same CNR value when decreasing tube voltage. CNR was found to be improved decreasing tube voltage for all ages of pediatric phantoms. However, due to larger exposure time, motion artifacts may be conspicuous. Conclusion A reliable optimization methodology for head radiographs in pediatric patients was presented. The method described may be also applied in other anatomical regions.

Introduction Real time visual feedback from electronic personal dosimeters has been shown to reduce occupational exposures when first introduced in an interventional cardiology setting [1] . In a recent paper by our group, we found that there was little difference one month and six months after the introduction of such a system. This study aims to assess the effect of removing the visual dose feedback on operator exposures. Materials and methods Occupational collar exposures were monitored for cardiologists ( n = 5) over a series of mixed case types ( n = 95) in a busy interventional cardiology laboratory [1] . For half the cases the visual feedback screen was switched off during the procedure depending on an assigned random number. The radiation exposure data was analysed using a Mann Whitney U test. Results/discussion There was no significant statistical difference in radiation exposure to the cardiologists between when the visual feedback system was switched off or on. Increased case numbers may point to differences between operators and case types. Conclusion This study suggests that real time visual feedback may not prove beneficial to dose reduction in an established electronic monitoring system.

Radiotherapy services in Ireland have undergone extensive changes in terms of number and complexity of equipment installed in both public and private institutes in recent years. The latest addition to the ever growing number of sophisticated equipment was the unveiling of the CyberKnife facility at the Hermitage Medical Clinic. Due to planning restrictions the new facility had to be contained in the existing hospital’s blueprint with the only available location being an unused CT simulation room. The room design would be different from conventional radiotherapy bunkers due to the fact that the CyberKnife can fire an unfiltered beam in any direction except the roof (restriction of 220 above the horizontal). Therefore all walls must be primary barriers with the roof designed to protect against the large leakage radiation resulting from the high MUs used during the treatments. Space consideration indicated that concrete alone could not be used to restrict the radiation beam to acceptable limits. To this end a combination of steel, lead, normal and heavy concrete were used to meet the dose constraints established by the Irish licensing authorities. Novel designs to protect against ground shine and from primary and leakage radiation emerging under the direct shielding door had to be developed. Also many of the difficulties encountered during the design and conversion of the CT simulation room will be addressed.