[Show abstract][Hide abstract] ABSTRACT: Background. Quantifying the interfraction dose variations in the organs at risk (OAR) in HDR intracavitary brachytherapy (HDR ICBT). Methods. Rectum and bladder were contoured in 44 patients of cervical carcinoma on CT after each fraction of HDR ICBT (9 Gy/2 fractions). Interfraction dose variations (VARact) were calculated. Rigid image registration of consecutive fraction images allowed quantification of the hypothetical variation in dose (VARhypo) arising exclusively due to changes in applicator placement and geometry. VARhypo was regressed against the VARact to find out to what extent the applicator variation could explain the VARact in the OAR. The rest of the variation was assumed to be due to organ deformation. Results. The VARact in the dose to 2 cc of bladder and rectum were 1.46 and 1.16 Gy, respectively. Increased dose was seen in 16 and 23 patients in the subsequent fraction for bladder and rectum, respectively. Doses to OAR would have exceeded constraints in 16% patients if second fraction was not imaged. VARhypo explained 19% and 47% of the VARact observed for the bladder and rectum respectively. Conclusions. Significant interfraction variations in OAR doses can occur in HDR ICBT. Organ deformations are mostly responsible for this variation.
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study is to find the uncertainties in the reconstruction of MR compatible ring-tandem intracavitary applicators of high-dose rate image-based brachytherapy treatment planning using rigid registration of 3D MR and CT image fusion. Tandem and ring reconstruction in MR image based brachytherapy planning was done using rigid registration of CT and MR applicator geometries. Verifications of registration for applicator fusion were performed in six verification steps at three different sites of tandem ring applicator set. The first site consists of three errors at the level of ring plane in (1) cranio caudal shift (Cranial Shift) of ring plane along tandem axis, (2) antero-posterior shift (AP Shift) perpendicular to tandem axis on the plane containing the tandem, and (3) lateral shift (Lat Shift) perpendicular to the plane containing the tandem at the level of ring plane. The other two sites are the verifications at the tip of tandem and neck of the ring. The verification at the tip of tandem consists of two errors in (1) antero-posterior shift (AP Shift) perpendicular to tandem axis on the plane containing the tandem, and (2) lateral shift (Lat Shift) perpendicular to the plane containing the tandem. The third site of verification at the neck of the ring is the error due to the rotation of ring about tandem axis. The impact of translational errors from -5 mm to 5 mm in the step of 1 mm along x-, y-, and z-axis and three rotational errors about these axes from -19.1° to 19.1° in the step of 3.28° on dose-volume histogram parameters (D2cc, D1cc, D0.1cc, and D5cc of bladder, rectum, and sigmoid, and D90 and D98 of HRCTV were also analyzed. Maximum registration errors along cranio-caudal direction was 2.2 mm (1 case), whereas the errors of 31 out of 34 cases of registration were found within 1.5 mm, and those of two cases were less than 2mm but greater than 1.5 mm. Maximum rotational error of ring about tandem axis was 3.15° (1.1 mm). In other direction and different sites of the ring applicator set, the errors were within 1.5 mm. The impacts of registration errors on DVH parameters of bladder, rectum, and sigmoid were very sensitive to antero-posterior shift. Cranio-caudal errors of registration also largely affected the rectum DVH parameters. Largest change of 17.95% per mm and 20.65% per mm in all the DVH parameters of all OARs and HRCTV were observed for ϕ and Ψ rotational errors as compare to other translational and rotational errors. Catheter reconstruction in MR image using rigid registration of applicator geometries of CT and MR images is a feasible technique for MR image-based intracavitary brachytherapy planning. The applicator regis-tration using the contours of tandem and neck of the ring of CT and MR images decreased the rotational error about tandem axis. Verification of CT MR image fusion using applicator registration which consists of six steps of verification at three different sites in ring applicator set can report all the errors due to translation and rotational shift along θ, ϕ, and Ψ. ϕ and Ψ rotational errors, which produced potential changes in DVH parameters, can be tackled using AP Shift and Lat Shift at the tip of tandem. The maximum shift was still found along the tandem axis in this technique.
Journal of Applied Clinical Medical Physics 01/2014; 15(2):4206. · 0.96 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background: The aim of the study was to evaluate the vaginal dose and toxicity in patients of cervical cancer treated with image guided brachytherapy at our institute. Materials and Methods: Thirty-five patients treated with image based brachytherapy for cervical cancer were included. Vaginal contouring was done on MRI at brachytherapy and with CT scans of subsequent brachytherapy fractions. Dose volume parameters (DVH) were reported in accordance with the GEC-ESTRO guidelines. These were correlated with vaginal toxicity (assessed by CTCAE version 3) and quality of sexual life assessed at one year of completion of treatment. Results: Vaginal shortness was observed in 22 out of 30 (62.8%) patients, Nine (25.7%) had vaginal dryness and in 10 (28.5%) patients, there was contact bleeding. No association could be demonstrated between the dose volume parameters and vaginal toxicity in the present study. Conclusions: The lack of association between dose volume parameters of vagina with vaginal morbidity may be due to uncertainties involved in the delineation of vaginal wall and dosimetry. Future research is required to accurately define vaginal dose distribution to study its correlation with vaginal morbidity. Vaginal morbidity needs to be documented in order to improve the sexual outcome in these patients.
Asian Pacific journal of cancer prevention: APJCP 01/2014; 15(8):3619-23. · 1.50 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose/Introduction
To assess the variation in the doses received by the organs at risk (OARs) that can occur during treatment planning of cervical cancer by image-based brachytherapy.
Methods and Materials
After intracavitary application, two sets of images—CT and MRI—were obtained. The two sets of images were fused together with respect to the applicator. Contouring was done separately on CT and MR images. Dose received by the OARs on CT images with respect to the plans made on the MR images was estimated and compared with those on the MR images.
Although there was always a difference between the dose received by the OARs based on the CT and MRI contours, it was not significant for the bladder and rectum; 2 cc doses differed by 0.49 Gy (±0.44) p = 0.28 for the bladder and 0.30 Gy (±0.29) p = 0.16 for the rectum. The 1 cc and 0.1 cc differences were also not significant. However for the sigmoid colon, there was significant intrafraction variation in the 2 cc doses 0.61 (±0.6) p = 0.001, 1 cc doses 0.73 (±0.67) Gy p = 0.00, and 0.1 cc dose 0.97 (±0.93) Gy p = 0.009.
The variation in the doses to the OARs must be considered while weighing target coverage against overdose to the OARs. Although not significant for the bladder and rectum, it was significant for the sigmoid colon. Estimated doses to OARs on the planning system may not be the same dose delivered at the time of treatment.
[Show abstract][Hide abstract] ABSTRACT: Nanocrystals of the Li2B4O7:Cu were synthesized by a combustion method using 1000 ppm and 2500 ppm concentrations of Cu. TL characteristics of the synthesized Li2B4O7:Cu material doped with Cu of concentration 1000 ppm and 2500 ppm were studied using 150 MeV proton beam, 4 MeV and 9 MeV electron beam. It is observed that Li2B4O7:Cu doped with Cu (both 1000 ppm and 2500 ppm) exhibits a linear response in the range 1×100–3×101 Gy for exposure to 150 MeV proton beam. Nanocrystalline Li2B4O7:Cu, doped with 1000 ppm and 2500 ppm Cu, shows a linear TL response in the range 1×10−1–1×101 Gy for 4 MeV and 9 MeV electron beam. Fading of phosphors was also studied and it was found that Li2B4O7:Cu is quite suitable for proton and electron beam dosimetry.
Radiation Physics and Chemistry. 01/2014; 102:5–10.
[Show abstract][Hide abstract] ABSTRACT: To evaluate dosimetric and clinical outcome in patients of anal cancer treated with image-based interstitial high-dose-rate brachytherapy following chemoradiation.
Sixteen patients with anal cancer were treated with chemoradiation followed by brachytherapy boost with image-based high-dose-rate interstitial brachytherapy from January 2007 to June 2011. Two brachytherapy dose schedules were used: 21 Gy in seven fractions and 18 Gy in six fractions depending on response to chemoradiation. CT scan was done after placement of needles for confirmation of placement and treatment planning. Target volume was contoured on CT scans. Volumetric quality indices and dose parameters were calculated.
The mean clinical target volume was 17.7 ± 4.98 cm(3), and the median overall tumor size was 4.2cm (3.4-5cm). The mean values of coverage index, dose homogeneity index, overdose volume index, dose non-uniformity ratio, and conformal index were 0.94, 0.83, 0.21, 0.37, and 0.88, respectively. With a median followup of 41 months (range, 20-67.2 months), preservation of the anal sphincter was achieved in 14 patients. The 1- and 2-year local control rates were 93.8% and 87.5%, respectively. Treatment was well tolerated and none of the patients developed Grade 3 or higher late toxicity.
The combination of external beam radiotherapy with interstitial brachytherapy increases the dose to the tumor volume and limits the volume of irradiated normal tissue, thereby decreasing late toxicity. The use of image-based treatment planning provides better dose conformality with reduced toxicity and helps to prevent a geographic miss.
[Show abstract][Hide abstract] ABSTRACT: PURPOSE: To test the toxicity and efficacy of concomitant boost radiotherapy alone against concurrent chemoradiation (conventional fractionation) in locally advanced oropharyngeal cancer in our patient population. METHODS AND MATERIALS: In this open-label, randomised trial, 216 patients with histologically proven Stage III-IVA oropharyngeal cancer were randomly assigned between June 2006 and December 2010 to receive either chemoradiation (CRT) to a dose of 66Gy in 33 fractions over 6.5weeks with concurrent cisplatin (100mg/m(2) on days 1, 22 and 43) or accelerated radiotherapy with concomitant boost (CBRT) to a dose of 67.5Gy in 40 fractions over 5weeks. The compliance, toxicity and quality of life were investigated. Disease-free survival (DFS) and overall survival (OS) curves were estimated with the Kaplan-Meier method and compared using log rank test. RESULTS: The compliance to radiotherapy was superior in concomitant boost with lesser treatment interruptions (p=0.004). Expected acute toxicities were significantly higher in CRT, except for grade 3/4 mucositis which was seen more in CBRT arm (39% and 55% in CRT and CBRT, respectively; p=0.02). Late toxicities like Grade 3 xerostomia were significantly high in CRT arm than CBRT arm (33% versus 18%; p<0.0001). The quality of life was significantly poor in CRT arm at all follow up visits (p<0.0001). The rates of 2year disease-free survival were similar with 56% in the chemoradiotherapy group and 61% in CBRT group (p=0.2; HR-0.81, 95%CI-0.53-1.2). Subgroup analysis revealed that patients with nodal size >2cm had significantly better DFS with CRT (p=0.05; HR-1.59, 95%CI-0.93-2.7). CONCLUSION: In selected patients of locally advanced oropharyngeal cancer, concomitant boost offers a better compliance, toxicity profile and quality of life with similar disease control, than chemoradiation.
Radiotherapy and Oncology 06/2013; · 4.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The aim of the present study is to develop and verify the single film calibration procedure used in intensity-modulated radiation therapy (IMRT) quality assurance.
Radiographic films have been regularly used in routine commissioning of treatment modalities and verification of treatment planning system (TPS). The radiation dosimetery based on radiographic films has ability to give absolute two-dimension dose distribution and prefer for the IMRT quality assurance. However, the single therapy verification film gives a quick and significant reliable method for IMRT verification.
A single extended dose rate (EDR 2) film was used to generate the sensitometric curve of film optical density and radiation dose. EDR 2 film was exposed with nine 6 cm × 6 cm fields of 6 MV photon beam obtained from a medical linear accelerator at 5-cm depth in solid water phantom. The nine regions of single film were exposed with radiation doses raging from 10 to 362 cGy. The actual dose measurements inside the field regions were performed using 0.6 cm(3) ionization chamber. The exposed film was processed after irradiation using a VIDAR film scanner and the value of optical density was noted for each region. Ten IMRT plans of head and neck carcinoma were used for verification using a dynamic IMRT technique, and evaluated using the gamma index method with TPS calculated dose distribution.
Sensitometric curve has been generated using a single film exposed at nine field region to check quantitative dose verifications of IMRT treatments. The radiation scattered factor was observed to decrease exponentially with the increase in the distance from the centre of each field region. The IMRT plans based on calibration curve were verified using the gamma index method and found to be within acceptable criteria.
The single film method proved to be superior to the traditional calibration method and produce fast daily film calibration for highly accurate IMRT verification.
Reports of Practical Oncology and Radiotherapy 01/2013; 18(4):235-40.
[Show abstract][Hide abstract] ABSTRACT: AIMS: External beam radiotherapy followed by brachytherapy is the standard treatment for patients with carcinoma cervix. However, for patients who come from peripheral hospitals after incomplete surgery, whole pelvic radiotherapy (WPRT) followed by boost with either vaginal vault brachytherapy if suitable or further external beam radiotherapy is recommended. This study was conducted to evaluate if it was possible to give a higher tumour dose using intensity-modulated radiotherapy for that group of patients who were not suitable for high dose rate vaginal vault brachytherapy because of gross disease after WPRT. MATERIALS AND METHODS: A prospective study was carried out from 2005 to 2010 in which 25 postoperative patients of cervical carcinoma with gross residual disease after WPRT of 46 Gy/23 fractions/4.5 weeks were included. Nine patients were treated with 20 Gy to the planning target volume and 30 Gy to the clinical target volume in 10 fractions; 16 patients were treated with 30 Gy to the planning target volume and 35 Gy to the clinical target volume in 15 fractions. The end points of this study were local control, survival and treatment-related toxicity. RESULTS: The median follow-up was 38 months. The 3 year local control, progression-free survival and overall survival rates were 76, 74 and 67%, respectively. Late grade 2 rectal toxicity was seen in 11 patients. Grade 2 bladder toxicity occurred in two patients and grade 3 bowel toxicity in two patients. No other grade 3 or higher toxicity was seen. CONCLUSION: Inadequate and inappropriate surgery in invasive cervical cancer with resulting gross residual disease is common in India. It is possible to escalate the tumour dose by intensity-modulated radiotherapy boost after WPRT in postoperative cervical carcinoma patients with gross residual disease with low incidence of severe toxicity and excellent local control.
[Show abstract][Hide abstract] ABSTRACT: DOSIMETERIC AND RADIOBIOLOGICAL COMPARISON OF TWO RADIATION SCHEDULES IN LOCALIZED CARCINOMA PROSTATE: Standard Three-Dimensional Conformal Radiotherapy (3DCRT) followed by Intensity Modulated Radiotherapy (IMRT) boost (sequential-IMRT) with Simultaneous Integrated Boost IMRT (SIB-IMRT).
Thirty patients were enrolled. In all, the target consisted of PTV P + SV (Prostate and seminal vesicles) and PTV LN (lymph nodes) where PTV refers to planning target volume and the critical structures included: bladder, rectum and small bowel. All patients were treated with sequential-IMRT plan, but for dosimetric comparison, SIB-IMRT plan was also created. The prescription dose to PTV P + SV was 74 Gy in both strategies but with different dose per fraction, however, the dose to PTV LN was 50 Gy delivered in 25 fractions over 5 weeks for sequential-IMRT and 54 Gy delivered in 27 fractions over 5.5 weeks for SIB-IMRT. The treatment plans were compared in terms of dose-volume histograms. Also, Tumor Control Probability (TCP) and Normal Tissue Complication Probability (NTCP) obtained with the two plans were compared.
The volume of rectum receiving 70 Gy or more (V > 70 Gy) was reduced to 18.23% with SIB-IMRT from 22.81% with sequential-IMRT. SIB-IMRT reduced the mean doses to both bladder and rectum by 13% and 17%, respectively, as compared to sequential-IMRT. NTCP of 0.86 ± 0.75% and 0.01 ± 0.02% for the bladder, 5.87 ± 2.58% and 4.31 ± 2.61% for the rectum and 8.83 ± 7.08% and 8.25 ± 7.98% for the bowel was seen with sequential-IMRT and SIB-IMRT plans respectively.
For equal PTV coverage, SIB-IMRT markedly reduced doses to critical structures, therefore should be considered as the strategy for dose escalation. SIB-IMRT achieves lesser NTCP than sequential-IMRT.
[Show abstract][Hide abstract] ABSTRACT: To compare volumes and doses of tumour and organs at risk with computed tomography vs. magnetic resonance imaging in cervical cancer brachytherapy.
Seventeen previously untreated patients with cervical cancer suitable for radical treatment were included. All patients underwent brachytherapy using a magnetic resonance imaging-compatible applicator followed by both computed tomography and magnetic resonance imaging. The tumour and organs at risk (bladder, rectum, sigmoid and intestines) were contoured on computed tomography using only clinical findings and on magnetic resonance imaging using GEC-ESTRO guidelines. The volume and doses for tumour and organs at risk were evaluated using two-sided t-test.
When magnetic resonance imaging information is not included in contouring on computed tomography images, there is significant underestimation of tumour height and overestimation of the width (P< 0.05). However, there was no significant difference in V(100), D(90) and D(100) for high- and intermediate-risk clinical target volume in computed tomography and magnetic resonance imaging. The volumes and doses to 0.1, 1 and 2 cc for organs at risk were also similar.
Magnetic resonance imaging remains the gold standard for tumour delineation, but computed tomography with clinical information can give comparable results, which need to be studied further. Computed tomography-based contouring can be used comfortably for delineation of organs at risk.
Japanese Journal of Clinical Oncology 02/2012; 42(4):309-13. · 1.90 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study is to compare Lyman-Kutcher-Burman (LKB) model versus Niemierko model for normal tissue complication probability (NTCP) calculation and Niemierko model versus Poisson-based model for tumor control probability (TCP) calculation in the ranking of different treatment plans for a patient undergoing radiotherapy. The standard normal tissue tolerance data were used to test the NTCP models. LKB model can reproduce the same complication probability data of normal tissue response on radiation, whereas Niemierko model cannot reproduce the same complication probability. Both Poisson-based and Niemierko models equally reproduce the same standard TCP data in testing of TCP. In case of clinical data generated from treatment planning system, NTCP calculated using LKB model was found to be different from that calculated using Niemierko model. When the fractionation effect was considered in LKB model, the calculated values of NTCPs were different but comparable with those of Niemierko model. In case of TCP calculation using these models, Poisson-based model calculated marginally higher control probability as compared to Niemierko model.
[Show abstract][Hide abstract] ABSTRACT: To describe the results of conformal radiotherapy in advanced juvenile nasopharyngeal angiofibroma in a tertiary care institution.
Retrospective chart review was conducted for 8 patients treated with conformal radiotherapy between 2006 and 2009. The median follow-up was 17 months. All patients had Stage IIIB disease with intracranial extension. Radiotherapy was considered as treatment because patients were deemed inoperable owing to extensive intracranial/intraorbital extension or proximity to optic nerve. All but 1 patient were treated with intensity-modulated radiotherapy using seven coplanar fields. Median (range) dose prescribed was 39.6 (30-46) Gy. Actuarial analysis of local control and descriptive analysis of toxicity profile was conducted.
Despite the large and complex target volume (median planning target volume, 292 cm(3)), intensity-modulated radiotherapy achieved conformal dose distributions (median van't Reit index, 0.66). Significant sparing of the surrounding organs at risk was obtained. No significant Grade 3/4 toxicities were experienced during or after treatment. Actual local control at 2 years was 87.5%. One patient died 1 month after radiotherapy secondary to massive epistaxis. The remaining 7 patients had progressive resolution of disease and were symptom-free at last follow-up. Persistent rhinitis was the only significant toxicity, seen in 1 patient.
Conformal radiotherapy results in good local control with minimal acute and late side effects in juvenile nasopharyngeal angiofibromas, even in the presence of advanced disease.
International journal of radiation oncology, biology, physics 08/2011; 80(5):1398-404. · 4.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Point doses, as defined by the International Commission on Radiation Units and Measurements (ICRU), are classically used to evaluate doses to the rectum and bladder in high dose rate intracavitary brachytherapy (HDR-ICBT) in cervical cancer. Several studies have shown good correlation between the ICRU point doses and the volumetric doses to these organs. In the present study we attempted to evaluate whether this correlation could be used to predict the volumetric doses to these organs.
A total of 150 HDR-ICBT insertions performed between December 2006 and June 2008 were randomly divided into two groups. Group A (n=50) was used to derive the correlation between the point and volumetric doses using regression analysis. This was tested in Group B (n=100) insertions using studentised residuals and Bland-Altman plots.
Significant correlations were obtained for all volumetric doses and ICRU point doses for rectum and bladder in Group A insertions. The strongest correlation was found for the dose to 2 cc volumes (D(2cc)). The correlation coefficients for bladder and rectal D(2cc) versus the respective ICRU point doses were 0.82 and 0.77, respectively (p<0.001). Statistical validation of equations generated in Group B showed mean studentised residual values of 0.001 and 0.000 for the bladder and rectum. However, Bland-Altman analysis showed that the error range for these equations for bladder and rectum were ±64% and ±41% of the point A dose, respectively, which makes these equations unreliable for clinical use.
Volumetric imaging is essential to obtain proper information about volumetric doses.
The British journal of radiology 05/2011; 84(1001):441-8. · 2.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To assess the quality of high dose rate (H,D,R.) interstitial implants in breast cancer by using different volumetric indices and correlating them with skin and subcutaneous tissue toxicity. Out of 15 patients who were selected for interstitial implants after undergoing breast conservation surgery, five were treated radically with 34 Gy in 10 fractions in 5 days @ 3.4 Gy # twice daily and 10 patients recieved boost dose of 12 Gy in 4 fractions @ 3 Gy /# twice daily. The median follow up was 15 months. During each follow up assessment of late skin and subcutaneous tissue toxicity as per RTOG criteria was done . Various dosimetric indices were analysed. Dose Volume Histogram for dose per unit volume of skin for 10cc,5cc,2cc,1cc,0.1cc and 0.01cc was calculated. Best estimates and correlation of toxicity was revealed by assessment of Dose Nonuniformity Ratio(DNR) which also correlated well with geometry defining indices like Uniformity Index (UI).Volumetric assessment of skin dose for less than 2 cc correlated most with toxicity. DNR and UI can help us to assess and correlate late skin and subcutaneous tissue toxicity and thus serve useful to determine the quality of implant.
Indian journal of surgical oncology. 12/2010; 1(4):294-302.
[Show abstract][Hide abstract] ABSTRACT: Compare the planning target volume (PTV) coverage in three different shielding techniques in cranial irradiation.
Tertiary care center, prospective study.
The whole brain and meninges were contoured in ten planning CT scans, and expanded by 5 mm for the PTV. Shielding was designed using the French Society of Pediatric Oncology (SFOP) guidelines (SFOP plan), in-house recommendation (with 1 cm margin from the orbital roof and sphenoid wing) on a igitally Reconstructed Radiograph (DRR) and a third plan was generated using a 3D conformal radiation technique (3DCRT). The coverage of the PTV was noted using the isodose covering 95% of the PTV(D95), minimum dose within the PTV(D min ), and maximum dose within the PTV(D max ). The location of PTV not covered by the 95% isodose curve was noted. The median dose and maximum dose (D max ) to both eyes and maximum dose D max for the lens were noted.
General linear model method repeated the measure of analysis of variance test (ANOVA).
PTV coverage was significantly poorer in the SFOP and in-house plans as compared to 3DCRT plan (P=0.04). Median volume of PTV not covered by 95% isodose curve was 4.18 cc, 1.01 cc, and 0 cc in SFOP, in-house, and 3DCRT plan, respectively.
In the absence of volumetric planning techniques, SFOP guidelines lead to inadequate coverage and the in-house method is recommended.
Journal of cancer research and therapeutics 01/2010; 6(2):152-8. · 0.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The purpose of this comparative study was to test the accuracy of anisotropic analytical algorithm (AAA) and pencil beam convolution (PBC) algorithms of Eclipse treatment planning system (TPS) for dose calculations in the low- and high-dose buildup regions. AAA and PBC algorithms were used to create two intensity-modulated radiotherapy (IMRT) plans of the same optimal fluence generated from a clinically simulated oropharynx case in an in-house fabricated head and neck phantom. The TPS computed buildup doses were compared with the corresponding measured doses in the phantom using thermoluminescence dosimeters (TLD 100). Analysis of dose distribution calculated using PBC and AAA shows an increase in gamma value in the dose buildup region indicating large dose deviation. For the surface areas of 1, 50 and 100 cm2, PBC overestimates doses as compared to AAA calculated value in the range of 1.34%-3.62% at 0.6 cm depth, 1.74%-2.96% at 0.4 cm depth, and 1.96%-4.06% at 0.2 cm depth, respectively. In high-dose buildup region, AAA calculated doses were lower by an average of -7.56% (SD = 4.73%), while PBC was overestimated by 3.75% (SD = 5.70%) as compared to TLD measured doses at 0.2 cm depth. However, at 0.4 and 0.6 cm depth, PBC overestimated TLD measured doses by 5.84% (SD = 4.38%) and 2.40% (SD = 4.63%), respectively, while AAA underestimated the TLD measured doses by -0.82% (SD = 4.24%) and -1.10% (SD = 4.14%) at the same respective depth. In low-dose buildup region, both AAA and PBC overestimated the TLD measured doses at all depths except -2.05% (SD = 10.21%) by AAA at 0.2 cm depth. The differences between AAA and PBC at all depths were statistically significant (p < 0.05) in high-dose buildup region, whereas it is not statistically significant in low-dose buildup region. In conclusion, AAA calculated the dose more accurately than PBC in clinically important high-dose buildup region at 0.4 cm and 0.6 cm depths. The use of an orfit cast increases the dose buildup effect, and this buildup effect decreases with depth.
Journal of Applied Clinical Medical Physics 01/2010; 11(4):3351. · 0.96 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A prospective study was conducted to assess the feasibility of simultaneous integrated boost intensity-modulated radiotherapy (SIB IMRT) in our setting. Acute toxicities encountered during and immediately after treatment are reported.
Acute toxicity data prospectively collected during the treatment of the evaluable 28 patients with two SIB IMRT schedules were analysed. Toxicity was graded using the Common Terminology Criteria for Adverse Events version 3.0 system. Twenty-one patients were treated with the SIB72 schedule, delivering 72, 66 and 57 Gy in 33 fractions to the gross tumour volume, the high-risk clinical target volume and the low-risk clinical target volume, respectively, whereas seven patients were treated with the SIB66 schedule, delivering 66, 60 and 54 Gy in 30 fractions to the above volumes. No chemotherapy was given during the course of treatment. Descriptive analysis of the incidence and actuarial analysis of the duration of toxicities are presented.
Grade 3 or greater acute mucosal and actinic toxicity were seen 42.9 and 14.3% of the patients, respectively. Mucosal toxicity appeared by the second week in most patients. Atypical patterns of mucositis were encountered, including one patient with prolonged grade 4 mucosal ulceration in the SIB72 schedule. Grade 3 weight loss was seen in 10.57% of patients. Grade 3 pain was seen in 70% and grade 3 dysphagia in 10% during treatment.
SIB IMRT as used in this study was feasible, although associated with increased rates of mucosal and dermal toxicity.
[Show abstract][Hide abstract] ABSTRACT: 2D array of ionization chambers can be used for both absolute and relative dose verification of patient-specific intensity-modulated radiotherapy (IMRT) quality assurance. After an analysis of the dose linearity and spatial resolution of this 2D array (I'mRT MatriXX), the signal sampling time of 200 ms was selected for data acquisition. Multiple-sequence acquisitions at the nearest 4 positions with the shift of half of the distance between the centers of two adjacent ion chambers increase the spatial resolution up to four times when used with this I'mRT MatriXX. IMRT verification of head-and-neck case, which requires a large area for dosimetric verification, can be done with limited size of 24x24 cm(2), depending on the user requirements. It is found that the convolution method can also be used to improve the IMRT dose verification with the same parameters of the passing criteria significantly, viz., up to 99.87% agreement, by smoothening the treatment planning system profile.
[Show abstract][Hide abstract] ABSTRACT: Intensity-modulated radiotherapy using simultaneous integrated boost (SIB-IMRT) is an attractive method for the treatment of head and neck cancers with sparing of the salivary function.
To assess the feasibility, toxicity, and tumor control using SIB-IMRT in locally advanced head and neck cancers in the Indian setting.
The study was conducted in a regional cancer center in northern India. A review of the treatment result of the first 20 patients is presented.
SIB-IMRT was planned for 20 patients--14 patients were treated with the SIB-72 schedule delivering a dose of 72 Gy, 66 Gy, and 57 Gy to the PTV GTV , PTV CTV1 , and PTV CTV2 in 33 fractions. Six patients were treated with the SIB-66 schedule delivering 66 Gy, 60 Gy, and 54 Gy to the above-mentioned volumes in 30 fractions. Patients were monitored for toxicity using the CTCAE v 3.0 criteria. Descriptive analysis of toxicity and actuarial estimates of the loco-regional control and survival are presented.
Grade III mucositis was seen in 65% patients. None of the patients had Grade III dermatitis. The projected 2-year overall survival was 95%.
SIB-IMRT schedules evaluated were found to be safe and effective and are being subjected to further prospective studies.
Journal of cancer research and therapeutics 01/2009; 5(3):165-72. · 0.83 Impact Factor