Radiation therapy for cervical cancer involves a team of specialists, including diagnostic radiologists (DRs), radiation oncologists (ROs), and medical physicists (MPs), to optimize imaging‐based radiation therapy planning. The purpose of the study was to investigate the interobserver variations in tumor delineation on MR images of cervical cancer within the same and among different specialties. Twenty MRI cervical cancer studies were independently reviewed by two DRs, two ROs, and two MPs. For every study, each specialist contoured the tumor regions of interest (ROIs) on T2‐weighted Turbo Spin Echo sagittal images on all slices containing tumor, and the total tumor volume was computed for statistical analysis. Analysis of variance (ANOVA) was used to compare the differences in tumor volume delineation among the observers. A graph of all tumor‐delineated volumes was generated, and differences between the maximum and minimum volumes over all the readers for each patient dataset were computed. Challenges during the evaluation process for tumor delineation were recorded for each specialist. Interobserver variations of delineated tumor volumes were significant (p<0.01) among all observers based on a repeated measures ANOVA, which produced an F(5,95)=3.55. The median difference between the maximum delineated volume and minimum delineated volume was 33.5 cm3 (which can be approximated by a sphere of 4.0 cm diameter) across all 20 patients. Challenges noted for tumor delineation included the following: (1) partial voluming by parametrial fat at the periphery of the uterus; (2) extension of the tumor into parametrial space; (3) similar signal intensity of structures proximal to the tumor such as ovaries, muscles, bladder wall, bowel loops, and pubic symphysis; (4) postradiation changes such as heterogeneity and necrosis; (5) susceptibility artifacts from bowels and vaginal tampons; (6) presence of other pathologies such as atypical myoma; (7) factors that affect pelvic anatomy, including the degree of bladder distension, bowel interposition, uterine malposition, retroversion, and descensus. Our limited study indicates significant interobserver variation in tumor delineation. Despite rapid progress in technology, which has improved the resolution and precision of image acquisition and the delivery of radiotherapy to the millimeter level, such “human” variations (at the centimeter level) may overshadow the gain from technical advancement and impact treatment planning. Strategies of standardization and training in tumor delineation need to be developed.PACS number(s):

Radiation therapy for cervical cancer involves a team of specialists, including diagnostic radiologists (DRs), radiation oncologists (ROs), and medical physicists (MPs), to optimize imaging‐based radiation therapy planning. The purpose of the study was to investigate the interobserver variations in tumor delineation on MR images of cervical cancer within the same and among different specialties. Twenty MRI cervical cancer studies were independently reviewed by two DRs, two ROs, and two MPs. For every study, each specialist contoured the tumor regions of interest (ROIs) on T2‐weighted Turbo Spin Echo sagittal images on all slices containing tumor, and the total tumor volume was computed for statistical analysis. Analysis of variance (ANOVA) was used to compare the differences in tumor volume delineation among the observers. A graph of all tumor‐delineated volumes was generated, and differences between the maximum and minimum volumes over all the readers for each patient dataset were computed. Challenges during the evaluation process for tumor delineation were recorded for each specialist. Interobserver variations of delineated tumor volumes were significant false(p<0.01false) among all observers based on a repeated measures ANOVA, which produced an Ffalse(5,95false)=3.55. The median difference between the maximum delineated volume and minimum delineated volume was 33.5 cm3 (which can be approximated by a sphere of 4.0 cm diameter) across all 20 patients. Challenges noted for tumor delineation included the following: (1) partial voluming by parametrial fat at the periphery of the uterus; (2) extension of the tumor into parametrial space; (3) similar signal intensity of structures proximal to the tumor such as ovaries, muscles, bladder wall, bowel loops, and pubic symphysis; (4) postradiation changes such as heterogeneity and necrosis; (5) susceptibility artifacts from bowels and vaginal tampons; (6) presence of other pathologies such as atypical myoma; (7) factors that affect pelvic anatomy, including the degree of bladder distension, bowel interposition, uterine malposition, retroversion, and descensus. Our limited study indicates significant interobserver variation in tumor delineation. Despite rapid progress in technology, which has improved the resolution and precision of image acquisition and the delivery of radiotherapy to the millimeter level, such “human” variations (at the centimeter level) may overshadow the gain from technical advancement and impact treatment planning. Strategies of standardization and training in tumor delineation need to be developed.PACS number(s):

Purpose: Best fitting Tomotherapy treatment planning parameters for nine different lesion sites. Method and Materials: Tomotherapy treatment planning and delivery depends on parameters that are not necessarily familiar to a radiotherapy physicist. It is important for planners to familiarize themselves with these parameters and their impact on the time required for delivery: 51 Prostate plans, 268 lungs, 197 Brain, 21Liver, 38 Head & Neck, 46 Breast, 51Pelvis and 59 Pancreas plans for parameters like Pitch, Gantry period, treatment time, delivery modulation, total dose, calculated treatment length and slice width were analyzed for the best fit. Results: For Prostate average modulation delivery factor of 1.8 with average delivered dose of 51.53Gy and average treatment time of 342.4 seconds was used. Average numbers of fractions were 27. For Lung average dose of 50.70Gy with average modulation of 1.726. Average treatment time was 338.6 seconds and average numbers of fractions was 24. For Brain lesions average dose of 28.42Gy with average modulation of 1.71 was used. Average treatment time was 401.45 seconds. Average numbers of fractions was 11. For liver lesions average dose of 28.42Gy was used. Average modulation factor of 1.71 and average treatment time of 401.45 seconds. Average numbers of fractions was 11. For Head & Neck average dose of 36.08Gy with average modulation factor of 1.81 was used. Average treatment time was 420.64 seconds. Average numbers of fractions was 20. For Breast average dose of 41.44Gy with average modulation of 1.97. Average treatment time of 429.27 seconds with average numbers of fractions of 24. For Pelvis average dose of 38.8Gy with average modulation of 1.95. Average treatment time was 344.91 seconds. Average numbers of fractions was 19. For Pancreas average dose of 46.88Gy with average modulation of 1.78. Average treatment time was 266.64 seconds. Average numbers of fractions of 24.

Purpose: An elegant method of time‐resolved output (cGy/min) measurements, or TROM, is presented as a unique quality assurance tool. This temporal sampling technique of the dose rate allows for visual investigation of the output under a variety of circumstances. Method and Materials: An available tool has been implemented to monitor time‐resolved accelerator output for quality assurance. Tomotherapy Inc. provides an electrometer and software package (Tomoelectrometer and TEMS) that can sample charge readings from multiple ionization chambers at rates of 0.1 – 1.0 Hz. The Tomoelectrometer is interfaced to a computer running the TEMS software by RS232 connector. An ionization chamber inserted in the phantom is connected to the Tomoelectrometer. The measured charge is converted to the dose rate using the chamber calibration factor and an atmospheric correction. Static measurements have been performed using an SAD setup at 1.5 cm depth in a solid water phantom. TROM were performed on 2 helical Tomotherapy HiART II systems and a Varian EXd linear accelerator for “beam on” times in excess of 10 minutes. Results: The output dose rate is plotted against time for Varian and Tomotherapy accelerators. Rise times were < 1 second for all accelerators. TROM show variations on the order of ±1% for the Varian accelerator. Tomotherapy units showed greater variation. Peak values for both machines have been found to be 3.5% above the “average” value. Conclusion: Both types of machines exhibit a similar overshoot phenomenon at the onset, but the Tomotherapy unit(s) showed larger variation for some measurements. Temporal measurements of the output allow one to examine the inter‐ and intra‐ fractional dose rate variations, provides insight into other prolonged beam measurements, and may be a useful tool for troubleshooting.

Purpose: The purpose of this study is to come up with the most desirable and achievable target dose and OAR sparing using helical TomoTherapy planning system based on the earlier conducted studies. Methods: Patient having mesothelioma with mediastinal nodes was planned using helical TomoTherapy with Gross tumor volumes (GTVs) outlined were investigated: The goal was (1) keeping the prescribed dose to the targets while reducing the dose to the OARs and (2) escalating the target dose while maintaining the original level of healthy tissue sparing. Results: The primary lesion and nodal mass were kept at 98.7% of the dose and planning target volume (PTV) margins of 3 mm inner and 1cm outer with the planned mean of 94% volume to 54 Gy. Mean lung dose is 15.6 Gy, V5Gy:33%, V20Gy:30.1%, with contralateral lung V5Gy:0.87% Heart V45:26.2%, PTV V54Gy:90.5%, Pitch: 0.43 and Modulation factor: 1.66 Conclusion: Based on many studies on the comparison of 3DCRT, IMRT and TomoTherapy, it is recommended that helical TomoTherapy provide better target coverage and sparing of OARs. Our data proved better PTV coverage. We planned a target dose of 54Gy but our institute would recommend re‐evaluation at 45Gy. Helical TomoTherapy is a promising technique in the multimodality treatment of malignant pleural mesothelioma. Unlike other studies where low doses received by the contralateral lung appear to be the limiting factor, we found using helical TomoTherapy the contralateral to be minimal V5Gy:0.87%.