Evaluation of a deep image-to-image network (DI2IN) auto-segmentation algorithm across a network of cancer centers.

PURPOSE/OBJECTIVE S: Due to manual OAR contouring challenges, various automatic contouring solutions have been introduced. Historically, common clinical auto-segmentation algorithms used were atlas-based, which required maintaining a library of self-made contours. Searching the collection was computationally intensive and could take several minutes to complete. Deep learning approaches have shown significant benefits compared to atlas-based methods in improving segmentation accuracy and efficiency in auto-segmentation algorithms. This work represents the first multi-institutional study to describe and evaluate an AI algorithm for the auto-segmentation of organs at risk (OARs) based on a deep image-to-image network (DI2IN). MATERIALS/METHODS: The AI-Rad Companion Organs RT (AIRC) algorithm (Siemens Healthineers, Erlangen, Germany) uses a two-step approach for segmentation. In the first step, the target organ region in the optimal input image is extracted using a trained deep reinforcement learning network (DRL), which is then used as input to create the contours in the second step based on DI2IN. The study was initially designed as a prospective single-center evaluation. The automated contours generated by AIRC were evaluated by three experienced board-certified radiation oncologists using a four-point scale where 4 is clinically usable and 1 requires re-contouring. After seeing favorable results in a single-center pilot study, we decided to expand the study to six additional institutions, encompassing eight additional evaluators for a total of 11 physician evaluators across seven institutions. RESULTS: One hundred and fifty-six patients and 1366 contours were prospectively evaluated. The five most commonly contoured organs were the lung (136 contours, average rating = 4.0), spinal cord (106 contours, average rating = 3.1), eye globe (80 contours, average rating = 3.9), lens (77 contours, average rating = 3.9), and optic nerve (75 contours, average rating = 4.0). The average rating per evaluator per contour was 3.6. On average, 124 contours were evaluated by each evaluator. 65% of the contours were rated as 4, and 31% were rated as 3. Only 4% of contours were rated as 1 or 2. Thirty-three organs were evaluated in the study, with 19 structures having a 3.5 or above average rating (ribs, abdominopelvic cavity, skeleton, larynx, lung, aorta, brachial plexus, lens, eye globe, glottis, heart, parotid glands, bladder, kidneys, supraglottic larynx, submandibular glands, esophagus, optic nerve, oral cavity) and the remaining organs having a rating of 3.0 or greater (female breast, proximal femur, seminal vesicles, rectum, sternum, brainstem, prostate, brain, lips, mandible, liver, optic chiasm, spinal cord, spleen). No organ had an average rating below 3. CONCLUSION: AIRC performed well with greater than 95% of contours accepted by treating physicians with no or minor edits. It supported a fully automated workflow with the potential for time savings and increased standardization with the use of AI-powered algorithms for high-quality OAR contouring.

Multicenter Study of Pelvic Nodal Autosegmentation Algorithm of Siemens Healthineers: Comparison of Male Versus Female Pelvis.

Purpose: The autosegmentation algorithm of Siemens Healthineers version VA 30 (AASH) (Siemens Healthineers, Erlangen, Germany) was trained and developed in the male pelvis, with no published data on its usability in the female pelvis. This is the first multi-institutional study to describe and evaluate an artificial intelligence algorithm for autosegmentation of the pelvic nodal region by gender. Methods and Materials: We retrospectively evaluated AASH pelvic nodal autosegmentation in both male and female patients treated at our network of institutions. The automated pelvic nodal contours generated by AASH were evaluated by 1 board-certified radiation oncologist. A 4-point scale was used for each nodal region contour: a score of 4 is clinically usable with minimal edits; a score of 3 requires minor edits (missing nodal contour region, cutting through vessels, or including bowel loops) in 3 or fewer computed tomography slices; a score of 2 requires major edits, as previously defined but in 4 or more computed tomography slices; and a score of 1 requires complete recontouring of the region. Pelvic nodal regions included the right and left side of the common iliac, external iliac, internal iliac, obturator, and midline presacral nodes. In addition, patients were graded based on their lowest nodal contour score. Statistical analysis was performed using Fisher exact tests and Yates-corrected χ2 tests. Results: Fifty-two female and 51 male patients were included in the study, representing a total of 468 and 447 pelvic nodal regions, respectively. Ninety-six percent and 99% of contours required minor edits at most (score of 3 or 4) for female and male patients, respectively (P = .004 using Fisher exact test; P = .007 using Yates correction). No nodal regions had a statistically significant difference in scores between female and male patients. The percentage of patients requiring no more than minor edits was 87% (45 patients) and 92% (47 patients) for female and male patients, respectively (P = .53 using Fisher exact test; P = .55 using Yates correction). Conclusions: AASH pelvic nodal autosegmentation performed very well in both male and female pelvic nodal regions, although with better male pelvic nodal autosegmentation. As autosegmentation becomes more widespread, it may be important to have equal representation from all sexes in training and validation of autosegmentation algorithms.

Stereotactic radiosurgery in India: A nationwide survey of technology and quality assurance practices.

PURPOSE: India is rapidly adopting advanced treatments like Stereotactic Radiosurgery (SRS). However, there is a paucity of data on SRS practice. The aim of study is to assess the current status of technology and practices of machine quality assurance (QA) and patient specific quality assurance for SRS in India. MATERIALS AND METHODS: A survey questionnaire was designed using Google Forms and sent to chief/senior medical physicists across 220 radiotherapy centers in India on July 15, 2022. It contained questions on infrastructure availability, treatment planning, and QA. RESULTS: SRS was found to be extensively used for the treatment of brain metastases (99.3%), followed by meningioma (50.3%), acoustic neuroma (45.5%), and pituitary tumours (33.1%). The most commonly used photon energy and treatment technique were 6MV FFF and VMAT, respectively. A prescription isodose line ranging from 70% to 100% was selected by linac users. Most linac institutes verify pretreatment doses. There was a lack of uniformity in the analysis metrics such as Low Dose Threshold, Dose Difference, and Distance to Agreement. A survey revealed that the variety of SRS QA programs being followed at Indian radiotherapy centers. CONCLUSION: This is the first study to report the physics practice of SRS in India. The survey shows a need to carry out a postal dose audit for small static photon fields in India.

Multi-institutional dose audit in radiotherapy facilities using in-house developed optically stimulated luminescence disc dosimeters.

Aim: The aim of this study was to carried out the audit of radiotherapy centers practicing conformal radiotherapy techniques and demonstrate the suitability of this indigenous optically stimulated luminescence (OSL) disc dosimeters in beam quality audit and verification of patient-specific dosimetry in conventional and conformal treatments in radiotherapy. Materials and Methods: Dose audit in conventional and conformal (intensity-modulated radiotherapy and volumetric-modulated arc therapy) radiotherapy techniques was conducted using in-house developed Al2O3:C-based OSL disc dosimeter and commercially available Gafchromic EBT3 film in 6 MV (flat and unflat) photon and 6 and 15 MeV electron beams. OSL disc dosimeter and Gafchromic EBT3 film measured dose values were verified using the ionization chamber measurements. Results: Percentage variations of doses measured by OSL disc dosimeters and EBT3 Gafchromic film for conventional radiotherapy technique were in the range of 0.15%-4.6% and 0.40%-5.45%, respectively, with respect to the treatment planning system calculated dose values. For conformal radiotherapy techniques, the percentage variations of OSL disc and EBT3 film measured doses were in the range of 0.1%-4.9% and 0.3%-5.0%, respectively. Conclusion: The results of this study supported by statistical evidence provided the confidence that indigenously developed Al2O3:C-based OSL disc dosimeters are suitable for dose audit in conventional and advanced radiotherapy techniques.

Deficiency of phyto-available sulphur, zinc, boron, iron, copper and manganese in soils of India.

Nutrient deficiencies in soil-crop contexts and inappropriate managements are the important reasons for low crop productivity, reduced nutritional quality of agricultural produce and animal/human malnutrition, across the world. The present investigation was carried out to evaluate nutrient deficiencies of sulphur (S) and micronutrients [zinc (Zn), boron (B), iron (Fe), copper (Cu) and manganese (Mn)] in agricultural soils of India for devising effective management strategies to achieve sustainable crop production, improved nutritional quality in crops and better animal/human health. A total of 2,42,827 surface (0-15 cm depth) soil samples were collected from agriculture fields of 615 districts lying in 28 states of India and were analysed for available S and micronutrients concentration. The study was carried out under the aegis of All India Coordinated Research Project on Micro- and Secondary-Nutrients and Pollutant Elements in Soils and Plants. The mean concentrations were 27.0 ± 29.9 mg kg-1 for available S, 1.40 ± 1.60 mg kg-1 for available Zn and 1.40 ± 4.70 mg kg-1 for available B, 31.0 ± 52.2 mg kg-1 for available Fe, 2.30 ± 3.50 mg kg-1 for available Cu and 17.5 ± 21.4 mg kg-1 for available Mn. There were variable and widespread deficiencies of S and micronutrients in different states. The deficiencies (acute deficient + deficient + latent deficiency) of S (58.6% of soils), Zn (51.2% of soils) and B (44.7% of soils) were higher compared to the deficiencies of Fe (19.2% of soils), Cu (11.4% of soils) and Mn (17.4% of soils). Out of 615 districts, > 50% of soils in 101, 131 and 86 districts were deficient in available S, available Zn and available B, respectively. Whereas, > 25% of soils in 83, 5 and 41 districts had deficiencies of available Fe, available Cu and available Mn, respectively. There were occurrences of 2-nutrients deficiencies such S + Zn (9.30% of soils), Zn + B (8.70% of soils), S + B (7.00% of soils) and Zn + Fe (5.80% of soils) to a greater extent compared to the deficiencies of Zn + Mn (3.40% of soils), S + Fe (3.30% of soils), Zn + Cu (2.80% of soils) and Fe + B (2.70% of soils). Relatively lower % of soils were deficient in 3-nutrients (namely S + Zn + B, S + Zn + B and Zn + Fe + B), 4-nutrients (namely Zn + Fe + Cu + Mn) and 5-nutrients (namely Zn + Fe + Cu + Mn + B) simultaneously. The information regarding the distribution of deficiencies of S and micronutrients (both single and multi-nutrients) could be used by various stakeholders for production, supply and application of right kind of fertilizers in different districts, states and agro-ecological regions of India for better crop production, crop nutritional quality, nutrient use efficiency, soil health and for tackling human and animal malnutrition.

Relative energy response of indigenously developed optically stimulated luminescence dosimeters Al2 O3 :C, LiMgPO4 :B and LiCaAlF6 :Eu,Y in therapeutic photon and electron beams.

The relative energy responses of three indigenously developed optically stimulated luminescence (OSL) phosphors in the disc form were studied in therapeutic photon and electron beams. Calibration in terms of absorbed dose was carried out in the dose range 5-500 cGy in 60 Co gamma rays, high energy X-rays, and electron beams used in radiotherapy. The combined standard uncertainty in the estimation of absorbed dose using these OSL discs (OSLDs) was 3.3%. Dose-response curves of these OSLDs in 60 Co gamma rays, 6 and 10 MV (flat and unflat), 15 MV and 6 and 15 MeV electron beams were found to be linear. Furthermore, these OSLDs exhibited a relative energy-dependent response for both photon and electron beams. The relative energy response correction factor for photon and electron beams were in the range 1.01-1.05 and 1.03-1.06, respectively.

PATIENT-SPECIFIC DOSIMETRY USING IN-HOUSE DEVELOPED OSL DISC DOSEMETERS.

Circular discs of diameter 5 mm were made from three indigenously developed optically stimulated luminescent (OSL) phosphors for medical dosimetry. Dosimetric characteristics of these discs were evaluated for their use in machine and patient-specific dosimetry in radiotherapy. Uncertainty in dosimetric measurements using these discs was also estimated, and combined standard uncertainty in measurement of absorbed dose was found to be 3.34%. Characterisation studies indicate that OSL discs are suitable for dosimetric application in radiotherapy. These discs were also used for patient-specific dosimetry in conventional and conformal radiotherapy treatments (five different cases) vis-à-vis ionisation chamber and Gafchromic EBT3 film. Doses measured by OSL discs were found comparable to ionisation chamber and Gafchromic EBT3 film measured values and radiotherapy treatment planning system (TPS) calculated dose values in all the cases. The variation between TPS calculated dose values and OSL discs measured dose values was found within the measurement uncertainty.

Measurement of Total Scatter Factor for Stereotactic Cones with Plastic Scintillation Detector.

Advanced radiotherapy modalities such as stereotactic radiosurgery (SRS) and image-guided radiotherapy may employ very small beam apertures for accurate localized high dose to target. Accurate measurement of small radiation fields is a well-known challenge for many dosimeters. The purpose of this study was to measure total scatter factors for stereotactic cones with plastic scintillation detector and its comparison against diode detector and theoretical estimates. Measurements were performed on Novalis Tx™ linear accelerator for 6MV SRS beam with stereotactic cones of diameter 6 mm, 7.5 mm, 10 mm, 12.5 mm, and 15 mm. The advantage of plastic scintillator detector is in its energy dependence. The total scatter factor was measured in water at the depth of dose maximum. Total scatter factor with plastic scintillation detector was determined by normalizing the readings to field size of 10 cm × 10 cm. To overcome energy dependence of diode detector for the determination of scatter factor with diode detector, daisy chaining method was used. The plastic scintillator detector was calibrated against the ionization chamber, and the reproducibility in the measured doses was found to be within ± 1%. Total scatter factor measured with plastic scintillation detector was 0.728 ± 0.3, 0.783 ± 0.05, 0.866 ± 0.55, 0.885 ± 0.5, and 0.910 ± 0.06 for cone sizes of 6 mm, 7.5 mm, 10 mm, 12.5 mm, and 15 mm, respectively. Total scatter factor measured with diode detector was 0.733 ± 0.03, 0.782 ± 0.02, 0.834 ± 0.07, 0.854 ± 0.02, and 0.872 ± 0.02 for cone sizes of 6 mm, 7.5 mm, 10 mm, 12.5 mm, and 15 mm, respectively. The variation in the measurement of total scatter factor with published Monte Carlo data was found to be -1.3%, 1.9%, -0.4%, and 0.4% for cone sizes of 7.5 mm, 10 mm, 12.5 mm, and 15 mm, respectively. We conclude that total scatter factor measurements for stereotactic cones can be adequately carried out with a plastic scintillation detector. Our results show a high level of consistency within our data and compared well with published data.

High dose chemoradiation for unresectable hilar cholangiocarcinomas using intensity modulated external beam radiotherapy: a single tertiary care centre experience.

BACKGROUND: We present results of patients diagnosed with unresectable hilar cholangiocarcinomas treated with high dose radiotherapy and concurrent chemotherapy. METHODS: From Aug 2005 to Dec 2012, 68 consecutive patients were treated. Fifty patients (group 1) presenting to us with obstructive jaundice were planned for endobiliary brachytherapy (EBBT 14 Gy) followed external beam radiotherapy (EBRT 45 Gy). Twenty-two patients (group 2) who had previously undergone biliary drainage underwent EBRT (57 Gy). All patients received injection Gemcitabine 300 mg/m2/weekly along with EBRT. RESULTS: Twenty-nine patients in group 1 and 22 patients in group 2 completed the treatment. Twenty-six (55%) patients achieved complete radiological response, 16 (64%) belonging to group 1 and 8 (44%) of group 2 (P=0.05). The median overall survival (MOS) was 17.5 and 16 months for group 1 and 2 respectively (P=0.07). The 1- and 2-year survival was 63%, and 18% for group I and 61% and 22% for group II respectively. The MOS was 5 months and 1 year survival was 14% for patients receiving EBBT only. MOS was significantly better after complete response (P=0.001). CONCLUSIONS: Intensity modulated radiotherapy (IMRT) modulated high dose radiotherapy used either alone or with brachytherapy demonstrates potential to prolonged overall survival in unresectable hilar cholangiocarcinomas.

Interobserver Variability in the Delineation of Gross Tumour Volume and Specified Organs-at-risk During IMRT for Head and Neck Cancers and the Impact of FDG-PET/CT on Such Variability at the Primary Site.

PURPOSE: To assess interobserver variability (IOV) in the delineation of structures during intensity-modulated radiation therapy for head and neck squamous cell carcinoma and the impact of fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) on such variability at the primary site. METHODS: Three experienced head-neck radiation oncologists, blinded to each other, delineated the primary site gross tumour volume (GTV) and specified organs-at-risk (OARs) viz parotid gland, spinal cord, and cochlea in 10 patients with pharyngolaryngeal cancers suited for definitive intensity-modulated radiation therapy. IOV was assessed by concordance index (CI), Dice similarity coefficient (DSC), and Fleiss' kappa. Subsequently, the observers refined their corresponding GTVs incorporating information from FDG-PET/CT. The impact of FDG-PET/CT on variability of GTV was assessed by comparing the overlap indices with and without FDG-PET/CT using paired 't' test. RESULTS: There was moderate IOV in the delineation of GTV as evidenced by mean CI, DSC, and Fleiss' kappa of 0.41, 0.57, and 0.56, respectively. The use of FDG-PET/CT improved consistency of target volume delineation with resultant improvement in the overlap indices (mean CI, DSC, and Fleiss' kappa of 0.54, 0.69, and 0.69, respectively) that was statistically significant (P < .001). There was good agreement between the three observers for delineation of spinal cord and parotid glands. Concordance was worst for the cochlea. CONCLUSION: This study demonstrates the presence of moderate IOV between three experienced head and neck radiation oncologists in an academic institutional setting for the delineation of GTV. The use of FDG-PET/CT for target volume delineation results in significant reduction of such variability.

Volume changes with stereotactic body radiation therapy in early lung cancer: Time trends and outcomes.

INTRODUCTION: Tumour response during stereotactic body radiotherapy (SBRT) could be heterogeneous and the pattern of response may be used as an early predictor for outcome. METHODS: Twenty-two consecutive patients with early lung cancer (ELC), treated with SBRT, were evaluated retrospectively for their gross tumour volume (GTV) changes during radiation therapy (RT). Kilo-voltage computed tomography scans (KVCTs) were acquired before every fraction and GTV was contoured manually on a total of 152 datasets. Tumour volume changes were noted with every fraction. The overall survival (OS), locoregional recurrence free survival (LRFS) and distant metastasis free survival (DMFS) were computed using the Kaplan-Meier method and comparisons were made using log-rank test. RESULTS: Of the 22 patients, six had T1 tumours and 16 had T2 tumours. Median GTV was 40.6 cc (range 7.3-140.2 cc) on CT1 (KVCT at first fraction) and 33.3 cc (range 4.1-83.4 cc) on CTlast (KVCT at last fraction), suggesting a 17.9% median volume reduction at RT completion. Increase in tumour volume was noted in 18 (81.8%) patients at some point during RT. In the mid-treatment scan, 12 (54.5%) patients had higher tumour volumes than in CT1, however, only six (27.3%) patient's GTV remained larger compared to the baseline at the end of treatment. The median follow-up was 12.4 months. The OS, LRFS and DMFS rate at 12 and 18 months were 86.4%, 88.2%, 62% and 64.8%, 75.6% and 37.2% respectively. Tumours that regressed in volume by >17.9% (median volume reduction at RT completion) had significantly worse OS and LRFS compared to those that regressed <17.9% (P = 0.03 and 0.01 respectively). CONCLUSION: Gross tumour volume undergoes significant changes during SBRT. Early regression in tumour volume may be used as a predictor of poor LRFS and OS.

Superficial ocular malignancies treated with strontium-90 brachytherapy: long term outcomes.

PURPOSE: The incidence of conjunctival malignancies is less than 1%. Though surgical excision remains the mainstay of treatment, the incidence of positive surgical margins and local recurrence rates are high, which is approximately up to 33% in negative margins and 56% in positive margins. Radiotherapy reduces the risk of recurrence in these cases. Brachytherapy using ß emitters such as strontium-90 ((90)Sr) is an ideal treatment technique for these tumors with the advantage of treating only a few millimeters of tissue while sparing the underlying normal eye. We report the long term outcomes in the form of local control and late sequelae of patients with conjunctival malignancies treated with (90)Sr applicator brachytherapy. MATERIAL AND METHODS: During 1999-2013, 13 patients with conjunctival tumors, treated using (90)Sr brachytherapy were analyzed. Brachytherapy was either in a post-operative adjuvant or in a recurrent setting. Local control (LC), disease free survival (DFS), overall survival (OS), and late sequelae were evaluated. RESULTS: The median age at presentation was 47 years (range: 11-71 years). Thirteen patients with 15 tumors were treated. The commonest histology was squamous cell carcinoma. The median dose was 44 Gy over 11 fractions. The median follow up of all the patients was 51 months (range: 3-139 months). The median follow up of patients with carcinoma only was 64 months with a LC and DFS of 90.9% at 5 years. None of the patients developed ≥ grade II Radiation Therapy Oncology Group (RTOG) acute toxicities. One patient developed a focal scar and another developed corneal opacification at the limbus. Vision was not impaired in any of the patients. CONCLUSIONS: Strontium-90 brachytherapy used in early invasive conjunctival malignancies as an adjunct to surgery in primary and recurrent settings, results in optimal disease control and ocular functional outcomes.

Adaptive radiation therapy for pediatric head and neck malignancies: Dosimetric implications.

PURPOSE: This study was designed to evaluate the role of adaptive radiation therapy for children receiving curative radiation therapy to the head and neck region. METHODS AND MATERIALS: Ten children receiving definitive, conformal radiation therapy to the head and neck region were prospectively evaluated for anatomic changes during the course of radiation therapy. Images were acquired midway through the number of planned radiation therapy fractions during the planned course of radiation therapy. Body contours, target volumes, and organs at risk were redrawn on the new set of images. Two sets of additional treatment plans were generated: (1) a nonoptimized plan (plan 2), that is, an overlay of the original plan (plan 1) on the new set of contours, and (2) an optimized plan (plan 3) with the new set of contours. These 3 sets of plans were then compared for dosimetric differences. RESULTS: Five children had nasopharynx carcinoma, whereas the other 5 had embryonal rhabdomyosarcoma. The average reduction in gross tumor volume was 40% (mean volume, 41.87 mL; P = .005). The average changes in right and left parotid volumes were 2.72 and 1.92 mL, respectively. With nonoptimized plans, the average increase in maximum dose to the spinal cord was 15% (79.99%-94.99%; P = .013). With reoptimization, the maximum dose to the spinal cord decreased from 94.99% to 85.26% (mean difference, -9.73%; P = .02). Average D99 for the planning target volume (dose received by 99% of the target volume) was 88.66% and 86.89% with the original and reoptimized plans, respectively (P = .50). For the entire group, the mean conformation number index with nonoptimized plans was reduced from 0.734 to 0.628 (P = .013). This improved with reoptimization (P = .114). The homogeneity index improved with reoptimization from a mean value of 0.113 to 0.098 (P = 0.28). For nonoptimized plans, the average integral dose increased from 74.66 to 76.27 L-Gy (P = .486) compared with the original plans. Reoptimization resulted in a 5% average reduction in the integral dose, from 76.27 to 72.28 L-Gy (P = .007). CONCLUSIONS: This study demonstrates the usefulness of adaptive radiation therapy for children receiving radiation therapy to the head and neck region.

Comparison of 2 contouring methods of bone marrow on CT and correlation with hematological toxicities in non-bone marrow-sparing pelvic intensity-modulated radiotherapy with concurrent cisplatin for cervical cancer.

OBJECTIVES: To compare volumes and dose volume histogram (DVH) parameters for bone marrow contours using 2 methods on computed tomography (CT) and correlation with grade 2 or higher hematological toxicity (HT) in patients with cervical cancer treated with non-bone marrow-sparing intensity-modulated radiotherapy (IMRT) with concurrent cisplatin. MATERIALS AND METHODS: The planning CT scans of 47 patients prospectively enrolled and treated with IMRT arm of a phase 2 trial (NCT00193804) contoured for pelvic bone marrow in 2 sets; whole bone (WB), and freehand (FH) inner cavity of bone. Various subvolumes were made in each set--sacrum, ilium, ischium, lower pelvis, lumbosacral spine, sacrum, and whole pelvis--and compared for volume and DVH parameters (V(10), V(20), V(30), and V(40)) using paired t test. The hematological parameters during RT compiled from electronic database analyzed for higher than grade 2 (Radiation Therapy Oncology Group) HT and correlated with DVH parameters using log regression analysis (P < 0.05 significant). RESULTS: The FH subvolumes were 25% to 30% of WB. The mean DVH parameters V(10), V(20), V(30), and V(40) for whole-pelvis FH and WB were 86.5%, 77.5%, 62.5%, and 40.5%; and 88%, 79.6%, 62.9%, and 40%, respectively. There was significant difference between the DVH parameters of 2 sets (P < 0.05) for all subvolumes except ischium V(20), sacrum V(10), and lumbosacral spine V(10). The leukopenia, neutropenia, anemia, and thrombocytopenia higher than grade 2 was seen in 53%, 29.8%, 65.9%, and 10.6%, respectively. The mean V(10) for whole pelvis was less than 90% for both sets. On both univariate and multivariate analyses, only FH whole pelvis V(40) more than or equal to 40% correlated with higher than grade 2 leukopenia (Mann-Whitney U test, P = 0.026) and neutropenia (P = 0.05) with odds ratio, 4 (95% confidence interval, 1.166-13.728; P = 0.028). CONCLUSIONS: The FH bone marrow cavity volume is a better surrogate of active bone marrow on CT images and correlated with higher than grade 2 HT (V(40) >40%). Further prospective studies validating significance of high-dose effects and identifying correlation of bioimaging with CT contouring are warranted.

Dosimetric validation of new semiconductor diode dosimetry system for intensity modulated radiotherapy.

INTRODUCTION: The new diode Isorad was validated for intensity modulated radiotherapy (IMRT) and the observations during the validation are reported. MATERIALS AND METHODS: The validation includes intrinsic precision, post-irradiation stability, dose linearity, dose-rate effect, angular response, source to surface (SSD) dependence, field size dependence, and dose calibration. RESULTS: The intrinsic precision of the diode was more than 1% (1 σ). The linearity found in the whole range of dose analyzed was 1.93% (R² = 1). The minimum and maximum variation in the measured and calculated dose were found to be 0.78% (with 25 MU at ioscentre) and 4.8% (with 1000 MU at isocentre), respectively. The maximal variation in angular response with respect to arbitrary angle 0° found was 1.31%. The diode exhibited a 51.7% and 35% decrease in the response in the 35 cm and 20 cm SSD range, respectively. The minimum and the maximum variation in the measured dose from the diode and calculated dose were 0.82% (5 cm × 5 cm) and 3.75% (30 cm × 30 cm), respectively. At couch 270°, the response of the diode was found to vary maximum by 1.4% with ± 60 gantry angle. Mean variation between measured dose with diode and planned dose by TPS was found to be 1.3% (SD 0.75) for IMRT patient-specific quality assurance. CONCLUSION: For the evaluation of IMRT, use of cylindrical diode is strongly recommended.

Dosimetry and treatment planning of Occu-Prosta I-125 seeds for intraocular lesions.

Intraocular malignant lesions are frequently encountered in clinical practice. Plaque brachytherapy represents an effective means of treatment for intraocular lesions. Recently Radiopharmaceutical Division, BARC, Mumbai, has indigenously fabricated reasonable-cost I-125 sources. Here we are presenting the preliminary experience of dosimetry of sources, configuration of treatment planning system (TPS) and quality assurance (QA) for eye plaque therapy with Occu-Prosta I-125 seeds, treated in our hospital, for a patient with ocular lesions. I-125 seeds were calibrated using well-type chamber. BrachyVision TPS was configured with Monte Carlo computed radial dose functions and anisotropy functions for I-125 sources. Dose calculated by TPS at different points in central axis and off axis was compared with manually calculated dose. Eye plaque was fabricated of 17 karat pure gold, locally. The seeds were arranged in an outer ring near the edge of the plaque and in concentric rings throughout the plaque. The sources were manually digitized on the TPS, and dose distribution was calculated in three dimensions. Measured activity using cross-calibrated well-type chamber was within +/-10% of the activity specified by the supplier. Difference in TPS-calculated dose and manually calculated dose was within 5%. Treatment time calculated by TPS was in concordance with published data for similar plaque arrangement.