A Prospective Comparison of Computed Tomography with Transrectal Ultrasonography Assistance and Magnetic Resonance Imaging-Based Target-Volume Definition During Image Guided Adaptive Brachytherapy for Cervical Cancers.

PURPOSE: Although magnetic resonance imaging (MRI) represents the gold standard for image guided adaptive brachytherapy (IGABT) for cervical cancer, the majority of brachytherapy (BT) continues to be guided by computed tomography (CT). However, CT seems to overestimate the target-volume definition, and the potential of transrectal ultrasonography (TRUS) needs further evaluation. This prospective, comparative study aimed to evaluate CT-based target contouring with the incorporation of TRUS during BT. METHODS AND MATERIALS: Patients with locally advanced cervical cancer undergoing magnetic resonance IGABT between January 2013 and March 2014 were included. During the BT procedure, TRUS imaging with central tandem in situ was acquired at 3 representative levels. Reference points/dimensions (D1-D4) of the hypoechoic region on TRUS images with respect to the central tandem were recorded. CT and magnetic resonance BT planning imaging was performed after BT application. The high-risk clinical target volume (HR-CTV) was contoured on CT scans with incorporation of clinical and TRUS imaging findings and was compared with the gold standard MRI-based target approach. RESULTS: The image sets of 25 patients (International Federation of Gynecology and Obstetrics clinical stage IIB [11; 44%] and IIIB [14; 56%]) were evaluable. The mean (±standard deviation) volumes of HR-CTV on CT and MRI imaging were 39.1 (±20) cm³ and 39 (±19) cm³, respectively (r = 0.92; P < .001). A significant correlation was found between the HR-CTV dimensions (width and thickness) of CT and MRI scans at various levels (r = 0.70-0.80; P < .001). In addition, the absolute differences in target dimensions between CT and MRI were <0.5 cm. A strong correlation was seen between CT and MRI for patients with medial and lateral parametrial invasion (P < .05) compared with no parametrial disease at BT. Furthermore, the mean differences in HR-CTV width between CT and MRI contours at various levels, irrespective of parametrial involvement, was only 0.1 to 0.4 cm. CONCLUSIONS: This study suggests that a CT-based target and organ-at-risk delineation using MRI at diagnosis and real-time TRUS information during BT seems comparable with the gold standard MRI-based approach in IGABT for cervical cancer.

Commissioning and validation of commercial deformable image registration software for adaptive contouring.

PURPOSE: To report the commissioning and validation of deformable image registration(DIR) software for adaptive contouring. METHODS: DIR (SmartAdapt®v13.6) was validated using two methods namely contour propagation accuracy and landmark tracking, using physical phantoms and clinical images of various disease sites. Five in-house made phantoms with various known deformations and a set of 10 virtual phantoms were used. Displacement in lateral, anterio-posterior (AP) and superior-inferior (SI) direction were evaluated for various organs and compared with the ground truth. Four clinical sites namely, brain (n = 5), HN (n = 9), cervix (n = 18) and prostate (n = 23) were used. Organs were manually delineated by a radiation oncologist, compared with the deformable image registration (DIR) generated contours. 3D slicer v4.5.0.1 was used to analyze Dice Similarity Co-efficient (DSC), shift in centre of mass (COM) and Hausdorff distances Hf95%/avg. RESULTS: Mean (SD) DSC, Hf95% (mm), Hfavg (mm) and COM of all the phantoms 1-5 were 0.84 (0.2) mm, 5.1 (7.4) mm, 1.6 (2.2) mm, and 1.6 (0.2) mm respectively. Phantom-5 had the largest deformation as compared to phantoms 1-4, and hence had suboptimal indices. The virtual phantom resulted in consistent results for all the ROIs investigated. Contours propagated for brain patients were better with a high DSC score (0.91 (0.04)) as compared to other sites (HN: 0.84, prostate: 0.81 and cervix 0.77). A similar trend was seen in other indices too. The accuracy of propagated contours is limited for complex deformations that include large volume and shape change of bladder and rectum respectively. Visual validation of the propagated contours is recommended for clinical implementation. CONCLUSION: The DIR algorithm was commissioned and validated for adaptive contouring.

Magnetic Resonance Image Guided Adaptive Brachytherapy in Locally Advanced Cervical Cancer: An Experience From a Tertiary Cancer Center in a Low and Middle Income Countries Setting.

PURPOSE: To determine the clinical impact of magnetic resonance image guided adaptive brachytherapy (IGABT) for locally advanced cervical cancer (LACC) (stages II and III) in a tertiary care cancer hospital in a low and middle income countries setting. METHODS AND MATERIALS: Ninety-four LACC patients enrolled in a prospective EMBRACE (An International Study on MRI-Guided Brachytherapy in Locally Advanced Cervical Cancer) protocol treated with external radiation therapy (45 Gy in 25 fractions) with or without weekly cisplatin, followed by magnetic resonance IGABT (4 fractions of 7 Gy), were analyzed in detail for dosimetric and clinical outcomes including late toxicities. RESULTS: The mean (± standard deviation) high-risk clinical target volume (HR-CTV) at the first session of brachytherapy and at the second session of brachytherapy for the current study cohort was 46.94 ± 24.6 cm3 and 42.7 ± 22.5 cm3, respectively, with mean minimum dose received by 90% volume (D90) of 88.3 ± 4.4 equivalent 2-Gy fractionation (GyEQD2). At median follow-up (39 months), the local control rate (LCR) and overall progression-free survival rate were 90.1% ± 3.4% and 72.1% ± 4.8%, respectively, with grade 3 bladder toxicity in 3% of patients and rectum toxicity in 9%. The LCR at 39 months was significantly better in patients with stage IIB and IVA disease versus stage IIIB disease (100% vs 85%, P=.013). Local failures were limited to stage IIIB only and were associated with significantly larger HR-CTVs at brachytherapy (70 ± 25.7 cm3 vs 44.3 ± 21.9 cm3, P=.01) but not with HR-CTV D90 doses (which were similar for patients who had local failures vs those who did not: 86.3 ± 3.9 α/ß equal to 10 Gy (Gy10) vs 88.5 ± 5 α/ß equal to 10 Gy, P=.987). CONCLUSIONS: IGABT leads to a significant improvement in LCR and overall progression-free survival in LACC and should be considered for wider implementation in developing countries to improve outcomes.

Characterization of commercial MOSFET detectors and their feasibility for in-vivo HDR brachytherapy.

AIM: The present study was to investigate the use of MOSFET as an vivo dosimeter for the application of Ir-192 HDR brachytherapy treatments. MATERIAL AND METHODS: MOSFET was characterized for dose linearity in the range of 50-1000 cGy, depth dose dependence from 2 to 7 cm, angular dependence. Signal fading was checked for two weeks. RESULT AND DISCUSSION: Dose linearity was found to be within 2% in the dose range (50-1000 cGy). The response varied within 8.07% for detector-source distance of 2-7 cm. The response of MOSFET with the epoxy side facing the source (0 degree) is the highest and the lowest response was observed at 90 and 270 degrees. Signal was stable during the study period. CONCLUSION: The detector showed high dose linearity and insignificant fading. But due to angular and depth dependence, care should be taken and corrections must be applied for clinical dosimetry.

Uncertainties of deformable image registration for dose accumulation of high-dose regions in bladder and rectum in locally advanced cervical cancer.

PURPOSE: To compare the dose accumulation for bladder and rectum by deformable image registration (DIR) and direct addition (DA) of dose volume histogram parameters in magnetic resonance image-guided adaptive brachytherapy (IGABT). Two DIR algorithms, contour- and intensity-based, also have been analyzed. METHODS AND MATERIALS: Patients (n = 21) treated with IGABT for carcinoma cervix under the IntErnational study on MRI-guided BRachytherapy in locally Advanced CErvical cancer protocol were analyzed. Each patient underwent two HDR-BT applications, 1-week apart with two fractions of 7 Gy each delivered per application. For each application, magnetic resonance imaging, volume delineation, reconstruction, treatment planning (BT1 and BT2), and dose evaluation were carried out. BT1 and BT2 images were registered using an intensity-based DIR, followed by deformable dose accumulation (DDA), which was then compared with DA. To compare the intensity-based DIR to other DIR approaches, nine patients were further evaluated using an in-house contour-based DIR algorithm for bladder dose accumulation. RESULTS: Mean (±standard deviation; range) percentage variation between DA and DDA was found to be 2.4% (±3.3;-1.8, 11.5) and 5.2% (±5.1;-1.7, 16.5) for the rectum and bladder, respectively. The differences between the DA and DDA were found to be statistically significant for both rectum (p = 0.008) and bladder (p = 0.0003). Intensity-based DIR algorithm resulted in a larger mean deviation between DDA and DA as compared with contour-based DIR, although statistically insignificant (p = 0.32). The difference between DDA and DA was 2.4 ± 2.0% and 1.3 ± 1.2%, for intensity- and contour-based DIR, respectively. CONCLUSIONS: DA of dose volume histogram parameters provides a good estimate to the dose to the organs at risk; DIR based on image intensities may lead to systematic underestimation of dose due to implausible DIR.

Reirradiation using high-dose-rate brachytherapy in recurrent carcinoma of uterine cervix.

PURPOSE: To assess the feasibility of reirradiation with image-based high-dose-rate brachytherapy in previously irradiated patients with recurrent carcinoma of uterine cervix. METHODS AND MATERIALS: Thirty previously irradiated patients diagnosed with central recurrence were treated with reirradiation. Martinez Universal Perineal Implant Template was used in 24 patients and Vienna applicator in 6 patients. Median interval between two radiation schedules was 25 months. Median delivered dose was 42 Gy equivalent dose at 2 Gy (EQD2; interquartile range, 37-46 Gy EQD2). RESULTS: All 30 patients tolerated reirradiation well. Complete response was seen in 23 (76%) patients. With a median followup of 25 months, 2-year local control, disease-free survival, and overall survival were 44%, 42%, and 52%, respectively. Fifteen patients developed local recurrences; Local control rate was significantly higher with doses >40 Gy EQD2 (52% vs. 34%; p = 0.05). Disease-free survival was better for patients with longer interval (>25 months) between two radiotherapy schedules. Grade III radiation proctitis and cystitis was seen in 3 patients each, and Grade II small bowel toxicity was seen in 3 patients. CONCLUSIONS: Reirradiation using high-dose-rate brachytherapy is feasible with acceptable outcomes in isolated local recurrence deemed unsuitable for surgery. The outcome is better with higher doses.

A multicentre comparison of the dosimetric impact of inter- and intra-fractional anatomical variations in fractionated cervix cancer brachytherapy.

BACKGROUND AND PURPOSE: To compare the dosimetric impact of organ and target variations relative to the applicator for intracavitary brachytherapy by a multicentre analysis with different application techniques and fractionation schemes. MATERIAL AND METHODS: DVH data from 363 image/contour sets (120 patients, 6 institutions) were included for 1-6 fractions per patient, with imaging intervals ranging from several hours to ∼20 days. Variations between images acquired within one (intra-application) or between consecutive applicator insertions (inter-application) were evaluated. Dose plans based on a reference MR or CT image series were superimposed onto subsequent image sets and D(2cm(3)) for the bladder, rectum and sigmoid and D(90) for HR CTV were recorded. RESULTS: For the whole sample, the systematic dosimetric variations for all organs at risk, i.e. mean variations of D(2cm(3)), were found to be minor (<5%), while random variations, i.e. standard deviations were found to be high due to large variations in individual cases. The D(2cm(3)) variations (mean±1SD) were 0.6±19.5%, 4.1±21.7% and 1.6±26.8%, for the bladder, rectum and sigmoid. For HR CTV, the variations of D90 were found to be -1.1±13.1% for the whole sample. Grouping of the results by intra- and inter-application variations showed that random uncertainties for bladder and sigmoid were 3-7% larger when re-implanting the applicator for individual fractions. No statistically significant differences between the two groups were detected in dosimetric variations for the HR CTV. Using 20% uncertainty of physical dose for OAR and 10% for HR CTV, the effects on total treatment dose for a 4 fraction HDR schedule at clinically relevant dose levels were found to be 4-8 Gy EQD2 for OAR and 3 Gy EQD2 for HR CTV. CONCLUSIONS: Substantial variations occur in fractionated cervix cancer BT with higher impact close to clinical threshold levels. The treatment approach has to balance uncertainties for individual cases against the use of repetitive imaging, adaptive planning and dose delivery.

Inter-application variation of dose and spatial location of D(2cm(3)) volumes of OARs during MR image based cervix brachytherapy.

PURPOSE: Evaluation of Inter-application variation of doses and spatial location of D(2cm(3)) volumes of OARs during MR-image based cervix brachytherapy. MATERIALS AND METHODS: Twenty-seven patients treated with EMBRACE protocol were analyzed. Every patient had two applications, one week apart. For each application patient had undergone MR-imaging (MR-1 and MR-2), volume delineation, reconstruction, treatment planning (plan-1 and plan-2) and dose evaluation. Both the image series were then co-registered with applicator as the reference coordinate system (Eclipse planning system v8.6.14). Inter-application dose, volume and spatial location of D(2cm(3)) variation were evaluated. RESULTS: The largest inter-application systematic and random dose variations were observed for sigmoid as compared to rectum and bladder. The mean (±SD) of the relative D(2cm(3)) variations were 0.6(±15.1)%, 0.9(±13.1)% and 11.9(±37.5)% for rectum, bladder and sigmoid respectively. The overlap of D(2cm(3)) volumes was more than 50% in 16(59%), 8(30%) and 3(11%) patients for rectum, bladder and sigmoid, respectively. CONCLUSION: The 2cm(3) volumes between the applications/fractions are quite stable in topography for bladder and rectum, and hence the current practice of cumulative addition of D(2cm(3)) dose is expected to be valid for bladder and rectum. For sigmoid, significant topographical changes were seen, which need further validation in a larger patient population and in multi-centric settings.

Additional rectal and sigmoid mucosal points and doses in high dose rate intracavitary brachytherapy for carcinoma cervix: a dosimetric study.

BACKGROUND: Late rectal and sigmoid toxicities seen in cervical cancer patients are attributed to brachytherapy despite rectal doses within tolerance limits. The purpose of this study was to identify additional dosimetric points which may better forecast rectal complications. MATERIALS AND METHODS: Fifteen high dose rate intracavitary brachytherapy (ICA-HDR) applications with conventional X-ray and computed tomography (CT) based planning were studied. In addition to International Commission on Radiation Units and Measurement (ICRU) rectal and bladder points, proximal and distal rectal and sigmoid points were digitized on CT scans and dose volume histograms' (DVHs') parameters were computed and correlated. RESULTS: The mean ICRU, additional distal, proximal and sigmoid point doses were 486 ± 152 cGy, 527 ± 156 cGy, 401 ± 149 cGy and 838 ± 254 cGy, respectively, for a prescription of 700 cGy to point A. The mean sigmoid point dose was significantly higher than the ICRU rectal point doses (P=0.001). The high-dose sigmoid points were situated at a mean -8 mm (range -22.95 to 10.43 mm) lateral, 10 mm posterior (range -15.87 to 27.82 mm) and 31 mm (range 8.08-62.91 mm) cranial to the intracavitary applicator flange of central tandem. CONCLUSIONS: Our dosimetric study suggests that sigmoid points and 0.1 cm 3 receive significantly higher doses than rectal points during ICA-HDR in carcinoma of the uterine cervix. No definite conclusion on reproducible spatial distribution on orthogonal X-rays could be achieved. To document and reduce sigmoid doses, some form of 3D image-based planning is necessary.

Comparison of IPSA with dose-point optimization and manual optimization for interstitial template brachytherapy for gynecologic cancers.

PURPOSE: To compare inverse planning simulated annealing (IPSA) algorithm with the dose-point optimized (DPO) plan and manual/graphically optimized (GrO) plan for interstitial template brachytherapy for gynecologic cancers. METHODS AND MATERIALS: The data set of 10 consecutive patients was selected for this dosimetric study. For each patient, three plans were calculated: DPO, GrO, and IPSA. Dose-volume parameters from the three plans were compared to analyze the dosimetric outcome. RESULTS: Coverage of the clinical target volume (CTV) with GrO plan and IPSA algorithm was significantly better (mean V(100) of 88.8% and 89.1%; p=0.006) as compared with DPO plan (83.7%; p=0.62). Similarly, mean D(90) was same in both GrO plan and IPSA, 3.96±0.23 and 3.96±0.15Gy, respectively. DPO plans were homogeneous with homogeneity index being 0.82 as compared with 0.68±0.05 of GrO plan and 0.71±0.04 of IPSA. However, IPSA resulted in high conformity with conformity index of 0.78 as compared with 0.72 (p=0.001) and 0.68 (p≤0.001) for GrO and DPO plans, respectively. The dose to rectum (3.3±1.06Gy) and bladder (3.17±0.5Gy) was generally high for DPO plan. GrO plan reduced the dose to the rectum (2.91±0.63; p=0.011) and bladder (2.89±0.63Gy; p=0.003) significantly. IPSA resulted in a further reduction of the dose to rectum (2.79±0.67Gy; p=0.046) and bladder (2.81±0.67Gy; p=0.035), however with no statistical significance as compared with GrO plan. CONCLUSION: IPSA resulted in significant sparing of normal tissues without compromising CTV coverage as compared with DPO plan. However, IPSA did not show any significant improvement either in CTV coverage or in normal tissue sparing as compared with GrO plan. IPSA was found to be superior in terms of homogeneity and conformity as compared with GrO plan.

Does help structures play a role in reducing the variation of dwell time in IPSA planning for gynaecological brachytherapy application?

PURPOSE: To report our experience of dosimetric comparison of IPSA and manual plans, with a focus on the use of help structures (HS) during optimization. MATERIAL AND METHODS: 33 patients who underwent MR image-based HDR intracavitary-brachytherapy for cervix cancer based on GYN-ESTRO recommendations were selected for evaluation. Tandem/ovoid (T/O) and Vienna applicators were used. HS of diameter of 5 mm were drawn around the tandem/needles/ovoid and ring. Three plans were generated: manual optimized plan (MOPT), IPSA without help structures (IPSA_woHS) and IPSA with help structures (IPSA_wHS). Dose-volume parameters and the loading pattern were evaluated. RESULTS: For T/O, the use of HS did not make significant impact in the dose-volume parameters and in the loading of tandem and ovoids, however steep variation was found in the individual dwell time. In case of Vienna applicator, inclusion of HS in the optimization made a significant impact in loading of needles. The percentage ratio of total time of needles to the tandem (T(N/T%)) was found to be 14±2.5, 53±9, 22±6 for MOPT, IPSA_woHS and IPSA_wHS, respectively, which implies that in IPSA_woHS the dwell time in needles were half of the dwell time in the tandem, while in MOPT the needles were loaded only in 14%, and in IPSA_wHS it was 22% of the dwell time of tandem. Inclusion of HS in the optimization has reduced the contribution of dwell time of needle in IPSA_wHS. The individual variation of dwell time was also reduced in IPSA_wHS, however drawing of HS is a time consuming procedure and may not be practical for a routine practice. CONCLUSION: The role of HS was evaluated for IPSA for T/O and Vienna-applicator, the use of HS may be beneficial in case of combined intracavitary - interstitial approach.

Quantitative estimation of doses to salivary glands from using brachytherapy in head and neck cancers.

PURPOSE: To quantify the percentage doses received by salivary glands (SGDs) in head and neck interstitial brachytherapy (BT). METHODS AND MATERIALS: The study included 43 patients who underwent high-dose rate iridium-192 implant for oral cavity and oropharyngeal lesions treated with BT as a boost. BT dose varied with disease stage and external radiation dose, with the total mean dose of 66±4Gy. Patients were divided into two groups, midline and lateralized, based on anatomic implant location. Different dose parameters such as D(max), D(mean), DV(30%) of individual glands were derived from dose volume histogram representing the percentage maximum dose, mean dose, and dose received by 30% volume of individual SGDs, respectively. For better perception of the impact of BT on individual SGDs, the doses received are extrapolated to radical BT dose of 60Gy. RESULTS: For lateralized implants, the highest dose received by ipsilateral parotid (PTD) was 12.3% seen in tonsillar implants. The contralateral PTD receives minimal doses. As expected, the ipsilateral submandibular gland (SMG) received high doses in the range of 80% of the total prescribed dose, whereas contralateral SMG received 10% of ipsilateral dose. For the midline implants, the mean dose range for PTD was 7-11% of the total prescribed dose and for SMG between 17% and 56%, depending on the location. CONCLUSIONS: The study quantifies the percentage doses received by the individual SGDs in interstitial head and neck BT for use in future planning of the BT procedures and for salivary functional studies, prediction of damage, and quality-of-life parameters.

Whole abdomen radiation therapy in ovarian cancers: a comparison between fixed beam and volumetric arc based intensity modulation.

PURPOSE: A study was performed to assess dosimetric characteristics of volumetric modulated arcs (RapidArc, RA) and fixed field intensity modulated therapy (IMRT) for Whole Abdomen Radiotherapy (WAR) after ovarian cancer. METHODS AND MATERIALS: Plans for IMRT and RA were optimised for 5 patients prescribing 25 Gy to the whole abdomen (PTV_WAR) and 45 Gy to the pelvis and pelvic nodes (PTV_Pelvis) with Simultaneous Integrated Boost (SIB) technique. Plans were investigated for 6 MV (RA6, IMRT6) and 15 MV (RA15, IMRT15) photons. Objectives were: for both PTVs V90% > 95%, for PTV_Pelvis: Dmax < 105%; for organs at risk, maximal sparing was required. The MU and delivery time measured treatment efficiency. Pre-treatment Quality assurance was scored with Gamma Agreement Index (GAI) with 3% and 3 mm thresholds. RESULTS: IMRT and RapidArc resulted comparable for target coverage. For PTV_WAR, V90% was 99.8 ± 0.2% and 93.4 ± 7.3% for IMRT6 and IMRT15, and 98.4 ± 1.7 and 98.6 ± 0.9% for RA6 and RA15. Target coverage resulted improved for PTV_Pelvis. Dose homogeneity resulted slightly improved by RA (Uniformity was defined as U5-95% = D5%-D95%/Dmean). U5-95% for PTV_WAR was 0.34 ± 0.05 and 0.32 ± 0.06 (IMRT6 and IMRT15), 0.30 ± 0.03 and 0.26 ± 0.04 (RA6 and RA15); for PTV_Pelvis, it resulted equal to 0.1 for all techniques. For organs at risk, small differences were observed between the techniques. MU resulted 3130 ± 221 (IMRT6), 2841 ± 318 (IMRT15), 538 ± 29 (RA6), 635 ± 139 (RA15); the average measured treatment time was 18.0 ± 0.8 and 17.4 ± 2.2 minutes (IMRT6 and IMRT15) and 4.8 ± 0.2 (RA6 and RA15). GAIIMRT6 = 97.3 ± 2.6%, GAIIMRT15 = 94.4 ± 2.1%, GAIRA6 = 98.7 ± 1.0% and GAIRA15 = 95.7 ± 3.7%. CONCLUSION: RapidArc showed to be a solution to WAR treatments offering good dosimetric features with significant logistic improvements compared to IMRT.

Comparison of DVH parameters and loading patterns of standard loading, manual and inverse optimization for intracavitary brachytherapy on a subset of tandem/ovoid cases.

PURPOSE: Comparison of inverse planning with the standard clinical plan and with the manually optimized plan based on dose-volume parameters and loading patterns. MATERIALS AND METHODS: Twenty-eight patients who underwent MRI based HDR brachytherapy for cervix cancer were selected for this study. Three plans were calculated for each patient: (1) standard loading, (2) manual optimized, and (3) inverse optimized. Dosimetric outcomes from these plans were compared based on dose-volume parameters. The ratio of Total Reference Air Kerma of ovoid to tandem (TRAK(O/T)) was used to compare the loading patterns. RESULTS: The volume of HR CTV ranged from 9-68 cc with a mean of 41(±16.2) cc. Mean V100 for standard, manual optimized and inverse plans was found to be not significant (p=0.35, 0.38, 0.4). Dose to bladder (7.8±1.6 Gy) and sigmoid (5.6±1.4 Gy) was high for standard plans; Manual optimization reduced the dose to bladder (7.1±1.7 Gy p=0.006) and sigmoid (4.5±1.0 Gy p=0.005) without compromising the HR CTV coverage. The inverse plan resulted in a significant reduction to bladder dose (6.5±1.4 Gy, p=0.002). TRAK was found to be 0.49(±0.02), 0.44(±0.04) and 0.40(±0.04) cGy m(-2) for the standard loading, manual optimized and inverse plans, respectively. It was observed that TRAK(O/T) was 0.82(±0.05), 1.7(±1.04) and 1.41(±0.93) for standard loading, manual optimized and inverse plans, respectively, while this ratio was 1 for the traditional loading pattern. CONCLUSIONS: Inverse planning offers good sparing of critical structures without compromising the target coverage. The average loading pattern of the whole patient cohort deviates from the standard Fletcher loading pattern.

Treatment planning of epithelial ovarian cancers using helical tomotherapy.

Whole Abdomen Radiotherapy (WAR) for epithelial ovarian cancer though effective has been used sparingly due to inadequate target coverage and poor sparing of Organ At Risk (OAR) leading to significantly higher toxicities. Newer radiation techniques have shown potential for significant improvement in the therapeutic ratio. The purpose of this study was to evaluate Helical Tomotherapy(HT) for WAR. The objective parameters were to obtain uniform and adequate target coverage with maximum OAR sparing. HT plans were generated for five patients with field-width of 5.0/2.5 cm, modulation factor of 3.5/3.0, and a pitch of 0.3. A dose of 25 Gy in 25 fractions was prescribed to the abdomen with a simultaneous boost of 45 Gy in 25 fractions to the pelvis. Dose-volume parameters and various indices were analyzed and compared. Mean volume (standard-deviation) of abdominal and pelvic PTV (planning target volume) was 6630 +/-450 cm3 and 1235 +/-98 cm3 respectively. Mean length of PTV in cranio-caudal direction was 41+/-4 cm. Volume receiving 95% and 107% of the prescription dose, (V95% and V107%) was 95.6+/-2.7% and 2.6+/-0.5% for abdominal-PTV, and 95.7+/-2.4% and 0% for pelvic-PTV respectively. Homogeneity and Conformity indices were 17.5+/-1.7, 1.2+/-0.03 for abdominal PTV, and 5.2+/-0.7, 1.1+/-0.02 for pelvic-PTV respectively. Median dose received by the kidneys, liver and bone marrow were 9.6+/-1.2 Gy, 17+/-2.7 Gy and 22+/-1.4 Gy respectively. HT achieves an excellent coverage of WAR target with simultaneous pelvic boost and better organ (kidneys and liver) sparing. HT for WAR has the potential as consolidative therapy which is being evaluated further in a phase II cohort study in epithelial ovarian cancers.

Treatment outcome with low-dose-rate interstitial brachytherapy in early-stage oral tongue cancers.

PURPOSE: Although radical radiotherapy is known to be equally effective for early-stage oral tongue cancers (T1-2 N0) with the added advantage of organ and function preservation, surgery remains the preferred treatment. We present outcome of patients treated with brachytherapy (BT) either radical or boost. MATERIALS AND METHODS: Fifty-seven patients (T1/T2 31/26) were studied. Seventeen patients (30%) were treated with radical BT (50-67 Gy) while 40 (70%) with external beam radiation therapy (EBRT) + BT (36-56 Gy + 15-38 Gy]. Low-dose-rate (LDR) BT was delivered with 192 Ir wires, using plastic bead technique with varied dose rates (<60 cGy/h in 29 patients, 60-90 cGy/h in 17, and >90 cGy/h in 11). RESULTS: The overall local control (LCR) was achieved in 59.7% (34/57) patients. LCR for T1 and T2 was 67.8% and 50%, respectively. A total of 23 patients had failures [local: 20 (T1: 8; T2: 12 patients), node: 5 (T1:2; T2: 3), and local + nodal: 3]. Overall 5-year disease-free survival and overall survival (OAS) were 51% and 67%, respectively and those for T1 and T2 was 64.5/77.4% and 38.5/54% respectively (P = 0.002). All 16 patients were salvaged. Median survival after salvage treatment was 13.5 months (6-100 months). Soft tissue necrosis was observed in 12.3% (7/57) and osteoradionecrosis in two patients. CONCLUSION: BT, as an integral part of radical radiation therapy in early-stage tongue cancers, appears to be an effective alternative treatment modality with preservation of the organ and function without jeopardizing the outcome.

High-dose-rate brachytherapy boost for carcinoma of external auditory canal.

PURPOSE: To report dosimetry and outcome in a case of early stage carcinoma of external ear (T1N0M0) treated with radical radiotherapy alone using a combination of external beam radiotherapy (EBRT) and intracavitary irradiation with a high-dose-rate (HDR) (192)Ir remote afterloading system. METHODS AND METHODS: A 64-year-old gentleman who was diagnosed as T1N0M0 carcinoma of external ear was treated with combination of external beam radiation therapy followed by brachytherapy (BRT). A total dose of 40Gy was delivered by EBRT, following which a 6-Fr catheter for the HDR (192)Ir remote afterloader, fixed by a customized acrylic mold, was inserted into the external auditory canal (EAC) and a total intracavitary radiation dose of 22.5Gy (4.5Gy/F) was given. RESULTS: Evaluation at the completion of treatment and at the end of 4-year followup revealed no evidence of the disease. CONCLUSIONS: In the radical treatment of early stage EAC carcinoma, combination of external beam radiation therapy and BRT may be a modality of choice for its efficacy, less severe side effects, and better cosmetic results.

Dosimetric validation of first helical tomotherapy Hi-Art II machine in India.

A Helical Tomotherapy (HT) Hi-Art II machine, Hi ART (TomoTherapy, Inc., Madison, WI, USA) was installed at our center in July 2007, and was the first machine in India. Image-guided HT is a new modality for delivering intensity modulated radiotherapy (IMRT). Dosimetric tests done include (a) primary beam alignment (b) secondary beam alignment (c) water tank measurements (profiles and depth doses) (d) dose rate measurements (e) IMRT verification, and (f) Mega voltage Computed Tomography (MVCT) dose. Primary and secondary beam alignment revealed an acceptable linear accelerator (linac) alignment in both X and Y axes. In addition, it was observed that the beam was aligned in the same plane as gantry and the jaws were not twisted with respect to gantry. The rotational beam stability was acceptable. Multi-leaf collimators (MLC) were found to be stable and properly aligned with the radiation plane. The jaw alignment during gantry rotation was satisfactory. Transverse and longitudinal profiles were in good agreement with the "Gold" standard. During IMRT verification, the variation between the measured and calculated dose for a particular plan at the central and off-axis was found to be within 2% and 1mm in position, respectively. The dose delivered during the TomoImage scan was found to be 2.57 cGy. The Helical Tomotherapy system is mechanically stable and found to be acceptable for clinical treatment. It is recommended that the output of the machine should be measured on a daily basis to monitor the fluctuations in output.

Dose optimization of intra-operative high dose rate interstitial brachytherapy implants for soft tissue sarcoma.

OBJECTIVE: A three dimensional (3D) image-based dosimetric study to quantitatively compare geometric vs. dose-point optimization in combination with graphical optimization for interstitial brachytherapy of soft tissue sarcoma (STS). MATERIALS AND METHODS: Fifteen consecutive STS patients, treated with intra-operative, interstitial Brachytherapy, were enrolled in this dosimetric study. Treatment plans were generated using dose points situated at the "central plane between the catheters", "between the catheters throughout the implanted volume", at "distances perpendicular to the implant axis" and "on the surface of the target volume" Geometrically optimized plans had dose points defined between the catheters, while dose-point optimized plans had dose points defined at a plane perpendicular to the implant axis and on the target surface. Each plan was graphically optimized and compared using dose volume indices. RESULTS: Target coverage was suboptimal with coverage index (CI = 0.67) when dose points were defined at the central plane while it was superior when the dose points were defined at the target surface (CI=0.93). The coverage of graphically optimized plans (GrO) was similar to non-GrO with dose points defined on surface or perpendicular to the implant axis. A similar pattern was noticed with conformity index (0.61 vs. 0.82). GrO were more conformal and less homogeneous compared to non-GrO. Sum index was superior for dose points defined on the surface of the target and relatively inferior for plans with dose points at other locations (1.35 vs. 1.27). CONCLUSIONS: Optimization with dose points defined away from the implant plane and on target results in superior target coverage with optimal values of other indices. GrO offer better target coverage for implants with non-uniform geometry and target volume.