Purpose:The purpose of this study was to develop and use a novel phantom to evaluate the accuracy and usefulness of the Leskell Gamma Plan convolution‐based dose calculation algorithm compared with the current TMR10 algorithm.Methods:A novel phantom was designed to fit the Leskell Gamma Knife G Frame which could accommodate various materials in the form of one inch diameter, cylindrical plugs. The plugs were split axially to allow EBT2 film placement. Film measurements were made during two experiments. The first utilized plans generated on a homogeneous acrylic phantom setup using the TMR10 algorithm, with various materials inserted into the phantom during film irradiation to assess the effect on delivered dose due to unplanned heterogeneities upstream in the beam path. The second experiment utilized plans made on CT scans of different heterogeneous setups, with one plan using the TMR10 dose calculation algorithm and the second using the convolution‐based algorithm. Materials used to introduce heterogeneities included air, LDPE, polystyrene, Delrin, Teflon, and aluminum.Results:The data shows that, as would be expected, having heterogeneities in the beam path does induce dose delivery error when using the TMR10 algorithm, with the largest errors being due to the heterogeneities with electron densities most different from that of water, i.e. air, Teflon, and aluminum. Additionally, the Convolution algorithm did account for the heterogeneous material and provided a more accurate predicted dose, in extreme cases up to a 7–12% improvement over the TMR10 algorithm. The convolution algorithm expected dose was accurate to within 3% in all cases.Conclusion:This study proves that the convolution algorithm is an improvement over the TMR10 algorithm when heterogeneities are present. More work is needed to determine what the heterogeneity size/volume limits are where this improvement exists, and in what clinical and/or research cases this would be relevant.

Purpose:The purpose of the study was to implement a method for accurate rat brain irradiation using the Gamma Knife Perfexion unit. The system needed to be repeatable, efficient, and dosimetrically and spatially accurate.Methods:A platform (“rat holder”) was made such that it is attachable to the Leskell Gamma Knife G Frame. The rat holder utilizes two ear bars contacting bony anatomy and a front tooth bar to secure the rat. The rat holder fits inside of the Leskell localizer box, which utilizes fiducial markers to register with the GammaPlan planning system. This method allows for accurate, repeatable setup.A cylindrical phantom was made so that film can be placed axially in the phantom. We then acquired CT image sets of the rat holder and localizer box with both a rat and the phantom. Three treatment plans were created: a plan on the rat CT dataset, a phantom plan with the same prescription dose as the rat plan, and a phantom plan with the same delivery time as the rat plan.Results:Film analysis from the phantom showed that our setup is spatially accurate and repeatable. It is also dosimetrically accurate, with an difference between predicted and measured dose of 2.9%. Film analysis with prescription dose equal between rat and phantom plans showed a difference of 3.8%, showing that our phantom is a good representation of the rat for dosimetry purposes, allowing for +/‐ 3mm diameter variation. Film analysis with treatment time equal showed an error of 2.6%, which means we can deliver a prescription dose within 3% accuracy.Conclusion:Our method for irradiation of rat brain has been shown to be repeatable, efficient, and accurate, both dosimetrically and spatially. We can treat a large number of rats efficiently while delivering prescription doses within 3% at millimeter level accuracy.

Purpose: To quantify the effectiveness of anti-VEGF antibodies (bevacizumab and B20-4.1.1) as mitigators of radiation-induced, central nervous system (brain) necrosis in a mouse model. Experimental Design: Cohorts of mice were irradiated with single-fraction 50or 60-Gy doses of radiation targeted to the left hemisphere (brain) using the Leksell Perfexion Gamma Knife. The onset and progression of radiation necrosis were monitored longitudinally by in vivo, small-animal MRI, beginning 4 weeks after irradiation. MRI-derived necrotic volumes for antibody (Ab)-treated and untreated mice were compared. MRI results were supported by correlative histology. Results: Hematoxylin and eosin–stained sections of brains from irradiated, non–Ab-treated mice confirmed profound tissue damage, including regions of fibrinoid vascular necrosis, vascular telangiectasia, hemorrhage, loss of neurons, and edema. Treatment with the murine anti-VEGF antibody B20-4.1.1 mitigated radiation-induced changes in an extraordinary, highly statistically significant manner. The development of radiation necrosis in mice under treatment with bevacizumab (a humanized anti-VEGF antibody) was intermediate between that for B20-4.1.1–treated and non–Ab-treated animals. MRI findings were validated by histologic assessment, which confirmed that anti-VEGF antibody treatment dramatically reduced late-onset necrosis in irradiated brain. Conclusions: The single-hemispheric irradiation mouse model, with longitudinal MRI monitoring, provides a powerful platform for studying the onset and progression of radiation necrosis and for developing and testing new therapies. The observation that anti-VEGF antibodies are effective mitigants of necrosis in ourmousemodel will enable a wide variety of studies aimed at dose optimization and timing and mechanism of action with direct relevance to ongoing clinical trials of bevacizumab as a treatment for radiation necrosis. Clin Cancer Res; 20(10); 2695–702. 2014 AACR.

Purpose: To compare the dose distributions for identical treatment plans calculated by the Gamma Knife TMR 10 and convolution algorithms and measured with film dosimetry. Methods: An anthropomorphic head phantom was CT imaged with EBT2 film placed between each of seven axial sections. The resulting data set was used to plan three 16mm collimated targets on the Gamma Knife Perfexion, with each target centered on a film plane. Target 1 was placed within a homogeneous region while Targets 2 and 3 were placed in heterogeneous regions, i.e. tissue‐air and bone‐tissue interfaces, respectively. Plans using the same targets were made using both the TMR 10 and convolution algorithms. The prescription was delivered to the phantom using the TMR 10 treatment plans after which the convolution treatment plans were adjusted to Result in identical treatment times, thus ensuring identical dose delivery. Film dosimetry was done to determine actual dose delivered at target center and was compared to the predicted dose for each algorithm. Results: While there was strong correlation between both algorithms, the convolution algorithm predicted a higher delivered maximum dose than TMR 10, up to 2.5% higher in homogeneous tissue and up to 7% near an air cavity. Film dosimetry results were consistent with the convolution algorithm predictions, with an error of less than three percent. Conclusion: The Gamma Knife convolution algorithm predicts delivered dose to a clinically acceptable level, which was confirmed by film dosimetry. However, film in an anthropomorphic head phantom may not be adequate to measure the most significant differences between the two algorithms. Precise stereotactic treatments will require precise dosimetry, and a phantom developed specifically with Gamma Knife geometry in mind may be necessary to fully characterize the dosimetry at anatomy interfaces.

Figure 2. (Left) The volume of radiation necrosis vs. time postirradiation for untreated (red), Avastin-treated (green) and B20-4.1.1treated (blue) mice; (Right) Volumetric rate of radiation necrosis progression, derived from the slope of the curves in the left panel, for the period 3 – 7 and 7 – 9 weeks. *, Significant difference (P<0.01), **, Significant difference (P<0.005) compared with the untreated group. Preclinical MRI Reveals Bevacizumab Mitigates Radiation Necrosis X Jiang, JA Engelbach, J Cates, DK Thotala, RE Drzymala, DE Hallahan, JJH Ackerman, and JR Garbow Chemistry, Washington Univ. in st. louis, st louis, MO, United States, Radiology, Washington Univ. in st. louis, st louis, MO, United States, Radiation Oncology, Washington Univ. in st. louis, st louis, MO, United States

Purpose: To provide a method of accurate, submillimeter image‐guidance for the targeting of small brain tumors in an array of 5 mice when irradiating with the Gamma Knife Perfexion treatment unit. Small‐animal models provide a useful platform for studying the effects of radioprotectors and radiosensitizers on normal brain tissue and tumors. Efficient irradiation of an array of up to 5 mice in a single programmed sequence, using the Leksell Gamma Knife Perfexion (GKPfx) treatment unit, is an ongoing technique at our institution. One challenge in the process is to accurately guide the 4‐ mm‐diameter radiation beamsˈ focus of the GKPfx treatment unit to irradiate only a small region of interest (ROI) that includes the hippocampus. This can be accomplished through image guidance using a high‐field, high‐resolution small‐animal MR imager and transforming the ROI image coordinates to Leksell stereotactic treatment coordinates. Materials and Methods: Uniquely‐tagged mice were individually‐scanned using a small‐animal MR imager. Prior to scanning, each mouse was carefully positioned and immobilized with ear bars and a bite bar using a specially designed mouse holder module, which has three, CT‐ and MR‐ viewable, fiducials embedded within it. The fiducials provide a 3‐D frame of reference to transform ROI image coordinates to Leksell stereotactic coordinates. A Matlab script displays the image set, provides a tool to locate fiducials and other ROIs in image coordinates, computes the coordinate system transforms and saves results in an Excel worksheet. Transform computation uses Hornˈs quaternion‐based method. Results: The previously described method shows accuracy of less than 1.0 mm, when imaging resolution is 0.3 mm in X and Y and 1.0mm in Z. Computation for one mouse holder position takes less than 2 s on 1.8GHz Centrino Duo PC.Conclusions: This image‐guided technique provides for fast and accurate MR/CT localized radiation targeting of mouse brain.

Purpose: To evaluate the effect of breathing motion and setup error on the accuracy of treatment planning surface dose calculation for breast cancer treatments on helical Tomotherapy. Method and Materials: In‐vivo dosimetry with MOSFET detectors was performed on a cohort of patients treated for breast cancer on helical Tomotherapy. The detectors were placed under the 0.5‐cm tissue‐equivalent bolus used for patient treatments. The pre‐treatment MVCT images were used to localize the MOSFET detectors. Tomotherapy's Planned Adaptive software was used to compare the measurements against both the planned surface doses at the locations of the dosimeters as well as the recalculated doses based on the MVCT scan. This allowed for evaluation of the combined impact of breathing and setup error on the surface dose contribution, and the quantification of dosimetric accuracy of the Tomotherapy treatment planning system for breast cancer patients. Results: The differences between dose values at the locations of the dosimeters from the plan and those calculated from the MVCT image were on average within 1% of each other. The average dosimetric differences between measured and calculated doses were 7.8 and 8 percent for the planned and adaptive calculated doses, respectively. Overall, the treatment planning system overestimated the dose at the skin/bolus interface. Conclusion: The treatment planning system was previously shown to overestimate dose at a 5‐mm depth by about 4%. The possible setup error is taken into account by the adaptive software since it recalculates the dose distribution based on the MVCT image associated with the treatment for which the measurement was made. Since the setup error was shown to be within 1%, it is therefore estimated that the dosimetric consequence of breathing motion may be as high as 3%.Conflict of Interest: This work was partially supported by a grant from Tomotherapy, Inc.

Purpose: To demonstrate the use of TomoTherapy's exit detector data to identify changes in patient anatomy for GYN radiation therapy. Methods and Materials: A pelvic anthropomorphic phantom with six layers of 0.5 cm bolus was used to simulate a patient with excess body fat in the lower abdomen and pelvis. The phantom was CT-simulated, and a GYN helical IMRT treatment plan was created using TomoTherapy treatment planning system. The contours, treatment plan quality, and fractionation were consistent with our department protocols. Two fractions were delivered to the phantom with six layers of bolus. Subsequent fractions following the removal of 1 layer of 0.5 cm bolus to simulate patient weight loss were treated until all layers of bolus were removed. Following each fraction, the exit detector data was collected using TomoTherapy TQA software and analyzed in MATLAB. MVCT scans were for the length of the target volume were obtained following the removal of 1.5 cm and 3.0 cm layers of bolus, and TomoTherapy Adaptive software was used to calculate modified dose distributions and DVHs on the ‘thinner’ phantom. Results: The exit detector data for each fraction is a sinogram with a width of 640 (the number of exit detectors) and a length of 51 × RG, where RG is the number of gantry rotations required by the treatment plan. Analysis of sinogram differences and ratios (relative to the first fraction with all six bolus layers in place) yields 2-D plots useful for qualitative indications of weight loss. Conclusions: Anatomical changes are observed following simple analysis of TomoTherapy exit detector data. Simulated weight loss in a phantom suggests these data will be useful for monitoring anatomical changes in patients. Minor changes have been observed for one GYN patient thus far, and we have begun collecting data for more patients.

At present, helical tomotherapy (HT) delivery is restricted to fixed jaw widths and constant couch speed (FJCC). Using this technique, there is a trade-off between treatment delivery time (TDT) and the plan quality. The next generation of HT delivery technique allows dynamic motion of both the jaws and couch called Dynamic Jaws and Dynamic Couch (DJDC). The main objective of this study is to compare the quality of the treatment plans (TPs) generated by FJCC and DJDC techniques for patients with esophageal cancer. Gain in TDTs of DJDC was also evaluated. In this study, nine clinical esophageal cancer patients, treated on tomotherapy system using FJCC technique, were retrospectively planned on TomoTherapy's research platform using DJDC technique. Patients received CT simulations upon which PTV60Gy, PTV54Gy and several organs at risk (OARs) were delineated for treatment planning. The OARs of interest were the lungs, spinal cord (SC), heart, liver, stomach, kidneys, and normal esophagus (NE). PTV60Gy had a mean volume of 271 ± 128 cc while PTV54Gy had a mean volume of 285 ± 137 cc. The FJCC plans were copied and used as a template for creating the DJDC TPs and followed our clinical treatment planning guidelines. The optimization goals were to keep the OARs doses below their toxic limits. Dose volume histograms (DVHs) were compared to evaluate the dose homogeneity in the PTvs. and critical structure sparing. For PTV60Gy, both average minimum dose (D99%) and the average mean dose (MD) are increased in DJDC plans by 1.2 ± 0.6 Gy and 0.5 ± 0.4 Gy. The homogeneity indexes (HI = (D1%-D99%)/DRx) of the PTV60Gy is same for DJDC and FJCC plans. For PTV54Gy the average HI is increased in DJDC plans by 0.12 ± 0.03 while maintaining the same average MD. The average MD in DJDC plans to the heart, total lung, liver, stomach and NE were decreased by 1.5 ± 3.2 Gy, 0.8 ± 0.8 Gy, 1.5 ± 1.6 Gy, 3.5 ± 2.4 Gy, 1.3 ± 1.0 Gy, respectively. The majority of the dose sparing in DJDC plans for heart, lungs, liver, stomach, and NE occurred in dose ranges of 20-50 Gy, 10-25 Gy, 5-30 Gy, 5-50 Gy, 5-55 Gy, respectively. The average maximum dose to the SC was 40.1 ± 4.3 Gy and 42.0 ± 2.9 Gy for FJCC and DJDC plans, respectively. DJDC planning reduced the amount of dose delivered to organs lying superiorly and inferiorly to the PVT. This can be seen in SC and NE DVHs. The average TDTs for FJCC and DJDC plans were 8:29±0.07 and 4:55±0.03, respectively. The average time saving in DJDC delivery is 42%. Although dosimetric accuracy of DJDC technique is unknown, this treatment planning study comparing the current FJCC and next generation DJDC delivery shows promising results in critical structure sparing while reducing the TDTs. All the TPs generated by DJDC technique were within our clinical planning guidelines and the protocol limits.

Purpose: Purpose of this study is to explore the feasibility of utilizing Tomotherapy's exit-detector-data for identifying setup-errors in treatments of breast-cancer patients. Material and methods: Tomotherapy treatment plan mimicing breast treatment, generated on an anthropomorphic phantom, was used in this study. Thorax phantom was irradiated with the planned delivery sinogram after registering MVCT with kVCT. TomoTherapy's exit-detector-data-sinograms (EDDSs) were downloaded and ported into MatLab for further analysis. The phantom was then shifted by known offsets in x-,y-,z directions and collected the EDDSs after each irradiation. EDDSs from repeated irradiations were used to characterize the noise in the detector-signals. Average EDDS of the unshifted irradiations was subtracted from the individual EDDSs of the shifted simulations. Resulting difference EDDSs were analyzed to determine the extent of sinograms changes in frequency and magnitude. EDDSs from five clinically treated breast patients were downloaded after completion of their daily treatments and analyzed the data. Results and Discussion Difference EDDSs show that sinogram differences in frequency and magnitude were increased with increase in shifts. Linear regression analysis revealed a good correlation with regression coefficients >0.97. The features of the difference EDDSs are quite predictable; the difference EDDSs were positive for +X-shifts due to missing tissue; negative for +Y-shifts near sloping portion of the chest-wall and also for +Z-shifts due to increase in attenuation. Different histogram plots of the shifted simulations show that the maximum deviations were up to ±60% and ±250% for shifts of 5mm and 20mm, respectively. Maximum deviation in the EDDSs of five clinically treated breast patients were within ±50% suggesting a ∼5mm residual uncertainty in the patient setup. Conclusion: Preliminary investigation of exit detector sinograms data suggests that EDDSs are useful to identify the inter-fraction and intra-fraction setup errors and has great potential for in-vivo QA of the patient treatments.

Helical Tomotherapy (HT) delivers conformal dose distribution in a complex manner and quality assurance of such treatments is essential for patient safety. Errors in patient positioning may result in either underdose or overdose of the targets and the organs at risk. Purpose of this study is to explore the feasibility of utilizing the TomoTherapy exit-detector-data for detecting patient setup errors during the treatments of Head and Neck (H&N) cancer patients. A treatment plan mimicking a H&N cancer treatment, generated on an anthropomorphic phantom, was used in this study. After registering MV-CT with kV-CT the phantom was irradiated 10 times without changing its position. TomoTherapy's exit-detector-data-sinograms (EDDSs) were downloaded after each irradiation and ported into MatLab for further analysis. The phantom was then shifted by known off-sets in x, y, z directions and the EDDSs collected after each irradiation. EDDSs of 10 unshifted irradiations were averaged (mean-EDDS) and subtracted from the individual EDDSs to determine the noise in detector-channels. Then the mean-EDDS was subtracted from the individual EDDSs of the shifted simulations. Low detector signals consistent with closed leaves were removed from analysis. Resulting EDDSs were analyzed to evaluate (i) the number of detector channels (frequency) exceeding the noise level and (ii) average differences in signal strength (magnitude). Difference EDDSs were also evaluated on a projection by projection basis. Difference EDDSs were converted to% of their mean signal strength (%Diff-EDDSs). In addition to the phantom studies, EDDSs from 4 clinical H&N cancer patients were downloaded and analyzed to estimate the setup errors. The average background signal in the detector channels was < 0.6% of the mean signal strength. Difference EDDSs of the shifted simulations showed that both frequency and magnitude were proportional to their shifts with a linear regression (LR) analysis showing good correlation with LR coefficients of > 0.99. EDDSs analysis for individual projections could be used to evaluate shifts. For example, lateral shifts were apparent in A/P projections with the EDDS magnitude linearly related to the shift. Similar results were seen correlating A/P shifts with lateral projections. The maximum differences between shifted and unshifted EDDSs were up to ± 60% and ± 200% for the shifts of 3 mm and 10 mm, respectively. Difference histogram plots of our clinically treated H&N patients were within ± 50% suggesting a < 3 mm residual error their setup. Our preliminary investigation suggests that EDDSs may be useful for detecting inter- and intra-fraction setup errors and have great potential for in-vivo QA of Tomotherapy treatments without additional cost or dose to the patient.

Purpose/Objective(s)Current helical tomotherapy (HT) treatments are limited to fixed jaw widths and constant couch speeds (FJCC) during delivery. With these restrictions, increased plan quality results in increased delivery time. The next generation HT delivery allows for dynamic jaw motion and dynamic couch speed, a treatment technique called Dynamic Jaw and Dynamic Couch (DJDC). This novel technique could potentially produce treatment plans (TPs) with significantly reduced treatment times that are of equal of greater quality than those produced by FJCC. The purpose of this study is to compare the quality of DJDC plans to FJCC plans for patients with cervical cancer. Total delivery times (TDTs) of the two techniques will be compared.Materials/MethodsIn this study, ten clinical post-operative cervical or endometrial cancer patients, treated using FJCC technique on HT, were retrospectively planned on TomoTherapy's research platform using DJDC technique. PTvs. and organs at risk (OARs) were contoured on CT simulations for each patient for treatment planning. The OARs of interest were the bladder, rectum, bowel, pelvic bones, vertebral column and femoral heads. The CT scans and contoured volumes used for the original FJCC plan were also used for the DJDC plans. Clinical treatment planning guidelines of our institution were followed. The optimization goals were to keep the OAR doses below their toxicity limits. Dose volume histograms of the FJCC and DJDC plans were evaluated and compared based on dose homogeneity in the PTV, OAR sparing, and average mean doses given to critical structures.ResultsFor the DJDC plans, on average the PTV minimum dose (D99%) was decreased by 0.29 ± 0.90 Gy, the PTV maximum dose (D1%) was increased by 1.47 ± 0.66 Gy, and the PTV mean dose was increased by 0.54 ± 0.54 Gy. The average Homogeneity Index (HI = (D1%-D99%)/DRx) of the PTV was increased by 0.03 ± 0.02 in the DJDC plans. In DJDC plans, mean dose to the bladder, bowel (for nine patients), and pelvic bones increased by 0.01 ± 2.18 Gy, 1.21 ± 2.39 Gy, and 2.39 ± 2.44 Gy, respectively; while mean dose to the rectum, left femoral head, and right femoral head decreased by 2.32 ± 2.29 Gy, 2.22 ± 3.19 Gy, and 2.29 ± 3.69 Gy, respectively. Dose sparing in DJDC plans was shown most notably in the bladder and rectum, where V45 was reduced by 4.72 ± 3.78% and 12.23 ± 6.51%, respectively. Average delivery times (DTs) for FJCC and DJDC techniques were 9.33 ± 1.1 minutes and 3.56 ± 0.42 minutes, respectively.ConclusionsWhile dosimetric accuracy of the DJDC technique was not validated, this treatment planning study shows that the DJDC technique can produce plans of comparable quality to and with significantly shorter treatment times than those of FJCC plans. Using DJDC, treatment delivery times were reduced on average by 62% from those of the FJCC plans. Purpose/Objective(s)Current helical tomotherapy (HT) treatments are limited to fixed jaw widths and constant couch speeds (FJCC) during delivery. With these restrictions, increased plan quality results in increased delivery time. The next generation HT delivery allows for dynamic jaw motion and dynamic couch speed, a treatment technique called Dynamic Jaw and Dynamic Couch (DJDC). This novel technique could potentially produce treatment plans (TPs) with significantly reduced treatment times that are of equal of greater quality than those produced by FJCC. The purpose of this study is to compare the quality of DJDC plans to FJCC plans for patients with cervical cancer. Total delivery times (TDTs) of the two techniques will be compared. Current helical tomotherapy (HT) treatments are limited to fixed jaw widths and constant couch speeds (FJCC) during delivery. With these restrictions, increased plan quality results in increased delivery time. The next generation HT delivery allows for dynamic jaw motion and dynamic couch speed, a treatment technique called Dynamic Jaw and Dynamic Couch (DJDC). This novel technique could potentially produce treatment plans (TPs) with significantly reduced treatment times that are of equal of greater quality than those produced by FJCC. The purpose of this study is to compare the quality of DJDC plans to FJCC plans for patients with cervical cancer. Total delivery times (TDTs) of the two techniques will be compared. Materials/MethodsIn this study, ten clinical post-operative cervical or endometrial cancer patients, treated using FJCC technique on HT, were retrospectively planned on TomoTherapy's research platform using DJDC technique. PTvs. and organs at risk (OARs) were contoured on CT simulations for each patient for treatment planning. The OARs of interest were the bladder, rectum, bowel, pelvic bones, vertebral column and femoral heads. The CT scans and contoured volumes used for the original FJCC plan were also used for the DJDC plans. Clinical treatment planning guidelines of our institution were followed. The optimization goals were to keep the OAR doses below their toxicity limits. Dose volume histograms of the FJCC and DJDC plans were evaluated and compared based on dose homogeneity in the PTV, OAR sparing, and average mean doses given to critical structures. In this study, ten clinical post-operative cervical or endometrial cancer patients, treated using FJCC technique on HT, were retrospectively planned on TomoTherapy's research platform using DJDC technique. PTvs. and organs at risk (OARs) were contoured on CT simulations for each patient for treatment planning. The OARs of interest were the bladder, rectum, bowel, pelvic bones, vertebral column and femoral heads. The CT scans and contoured volumes used for the original FJCC plan were also used for the DJDC plans. Clinical treatment planning guidelines of our institution were followed. The optimization goals were to keep the OAR doses below their toxicity limits. Dose volume histograms of the FJCC and DJDC plans were evaluated and compared based on dose homogeneity in the PTV, OAR sparing, and average mean doses given to critical structures. ResultsFor the DJDC plans, on average the PTV minimum dose (D99%) was decreased by 0.29 ± 0.90 Gy, the PTV maximum dose (D1%) was increased by 1.47 ± 0.66 Gy, and the PTV mean dose was increased by 0.54 ± 0.54 Gy. The average Homogeneity Index (HI = (D1%-D99%)/DRx) of the PTV was increased by 0.03 ± 0.02 in the DJDC plans. In DJDC plans, mean dose to the bladder, bowel (for nine patients), and pelvic bones increased by 0.01 ± 2.18 Gy, 1.21 ± 2.39 Gy, and 2.39 ± 2.44 Gy, respectively; while mean dose to the rectum, left femoral head, and right femoral head decreased by 2.32 ± 2.29 Gy, 2.22 ± 3.19 Gy, and 2.29 ± 3.69 Gy, respectively. Dose sparing in DJDC plans was shown most notably in the bladder and rectum, where V45 was reduced by 4.72 ± 3.78% and 12.23 ± 6.51%, respectively. Average delivery times (DTs) for FJCC and DJDC techniques were 9.33 ± 1.1 minutes and 3.56 ± 0.42 minutes, respectively. For the DJDC plans, on average the PTV minimum dose (D99%) was decreased by 0.29 ± 0.90 Gy, the PTV maximum dose (D1%) was increased by 1.47 ± 0.66 Gy, and the PTV mean dose was increased by 0.54 ± 0.54 Gy. The average Homogeneity Index (HI = (D1%-D99%)/DRx) of the PTV was increased by 0.03 ± 0.02 in the DJDC plans. In DJDC plans, mean dose to the bladder, bowel (for nine patients), and pelvic bones increased by 0.01 ± 2.18 Gy, 1.21 ± 2.39 Gy, and 2.39 ± 2.44 Gy, respectively; while mean dose to the rectum, left femoral head, and right femoral head decreased by 2.32 ± 2.29 Gy, 2.22 ± 3.19 Gy, and 2.29 ± 3.69 Gy, respectively. Dose sparing in DJDC plans was shown most notably in the bladder and rectum, where V45 was reduced by 4.72 ± 3.78% and 12.23 ± 6.51%, respectively. Average delivery times (DTs) for FJCC and DJDC techniques were 9.33 ± 1.1 minutes and 3.56 ± 0.42 minutes, respectively. ConclusionsWhile dosimetric accuracy of the DJDC technique was not validated, this treatment planning study shows that the DJDC technique can produce plans of comparable quality to and with significantly shorter treatment times than those of FJCC plans. Using DJDC, treatment delivery times were reduced on average by 62% from those of the FJCC plans. While dosimetric accuracy of the DJDC technique was not validated, this treatment planning study shows that the DJDC technique can produce plans of comparable quality to and with significantly shorter treatment times than those of FJCC plans. Using DJDC, treatment delivery times were reduced on average by 62% from those of the FJCC plans.