RESUMO
PURPOSE: A feasibility study of 3D volume-based interstitial brachytherapy using thermoplastic polyether ether ketone (PEEK) catheters in advanced cervical cancer MR-based brachytherapy, when MR-compatible applicators are not available. MATERIAL AND METHODS: Five cervical cancer patients received EBRT dose of 50 Gy in 25 fractions to whole pelvis using 3D conformal radiotherapy after standard pre-treatment evaluation. In our institute, interstitial brachytherapy (ISBT) is planned in BrachyVision TPS and routinely performed using stainless steel needles with Syed-Neblett template. Standard MR-compatible ISBT applicators were not available; therefore, the implant was carried out using PEEK catheters and Syed-Neblett template. The T1 and T2 MR and CT images of patients were acquired for treatment planning. Gross tumor volume (GTV), high-risk clinical target volume (HR-CTV), intermediate-risk clinical target volume (IR-CTV), and organs at risk (OARs) were delineated with the use of MR T2 weighted images, following GEC-ESTRO guidelines. Volumetric optimization was used for planning, and the treatment plan was executed with high-dose-rate (HDR) 192Ir Gammamed Plus device. RESULTS: The dose prescribed to HR-CTV was 30 Gy low-dose-rate (LDR) equivalent (5 Gy × 4 fractions). Doses to target volume and OARs were analyzed using dose volume histogram (DVH). Dose values were biologically normalized to equivalent doses of 2 Gy fractions (EQD2). The average tumor volume was 67 cc and the average D90 of HR-CTV was 29 Gy (5.7 Gy/fraction) EQD2. D100 of HR-CTV volume was 18 Gy (3.8 Gy/fraction) EQD2. The total doses of 2 cc of rectum and bladder were 70 Gy and 76 Gy EQD2 (3.71 Gy and 4.04 Gy dose/fraction), respectively. CONCLUSIONS: When the facilities for MR-compatible applicators are not available, MR-based ISBT is feasible with PEEK catheters using available resources for advanced cervical cancer. Doses to HR-CTV and IR-CTV were achieved, restricting doses to OARs as per GEC-ESTRO guidelines.
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BACKGROUND AND PURPOSE: To examine the feasibility of improving breast-conserving radiotherapy with simultaneous integrated boost (SIB) and analyzing the efficiency of forward versus inverse intensity-modulated radiotherapy (IMRT) techniques in providing the same. MATERIALS AND METHODS: Three-dimensional conformal radiotherapy (3DCRT) field-in-field (FIF) plans with simultaneous and sequential boost and IMRT SIB plans were generated for the datasets of 20 patients who had undergone breast-conserving surgery. The 3 plans were compared dosimetrically for efficiency in terms of planning target volume (PTV) coverage (PTV 95%), homogeneity and conformity, dose delivered to ipsilateral/contralateral lungs (I/L: V10, V20, C/L: Vmean, V5), heart and contralateral breast (Vmean, V30 for heart and Vmean, V1, V5 for C/L breast). RESULTS: The FIF 3DCRT plan with SIB (PLAN B) was more homogeneous than the classical technique with sequential boost (PLAN A). There were less hot spots in terms of Dmax (63.7 ± 1.3) versus Dmax (68.9 ± 1), P < 0.001 and boost V107%, B (0.3 ± 0.7) versus A (3.5 ± 5.99), P = 0.001. The IMRT SIB (PLAN C) did not provide any significant dosimetric advantage over the 3DCRT SIB technique. IMRT SIB plan C was associated with increased dose to contralateral lung in-terms of V5 (10.35 +/- 18.23) vs. (1.13 +/- 4.24), P = 0.04 and Vmean (2.12 ± 2.18) versus Vmean (0.595 ± 0.89), P = 0.008. There was 3-fold greater exposure in terms of Monitor Unit (MU) (1024.9 ± 298.32 versus 281.05 ± 20.23, P < 0.001) and treatment delivery time. CONCLUSIONS: FIF 3DCRT SIB provides a dosimetrically acceptable and technically feasible alternative to the classical 3DCRT plan with sequential boost for breast-conserving radiotherapy. It reduces treatment time by 2 weeks. IMRT SIB does not appear to have any dosimetric advantage; it is associated with significantly higher doses to contralateral lung and heart and radiation exposure in terms of MU.
RESUMO
Various treatment planning systems are used to design plans for the treatment of cervical cancer using high-dose-rate brachytherapy. The purpose of this study was to make a dosimetric comparison of the 2 treatment planning systems from Varian medical systems, namely ABACUS and BrachyVision. The dose distribution of Ir-192 source generated with a single dwell position was compared using ABACUS (version 3.1) and BrachyVision (version 6.5) planning systems. Ten patients with intracavitary applications were planned on both systems using orthogonal radiographs. Doses were calculated at the prescription points (point A, right and left) and reference points RU, LU, RM, LM, bladder, and rectum. For single dwell position, little difference was observed in the doses to points along the perpendicular bisector. The mean difference between ABACUS and BrachyVision for these points was 1.88%. The mean difference in the dose calculated toward the distal end of the cable by ABACUS and BrachyVision was 3.78%, whereas along the proximal end the difference was 19.82%. For the patient case there was approximately 2% difference between ABACUS and BrachyVision planning for dose to the prescription points. The dose difference for the reference points ranged from 0.4-1.5%. For bladder and rectum, the differences were 5.2% and 13.5%, respectively. The dose difference between the rectum points was statistically significant. There is considerable difference between the dose calculations performed by the 2 treatment planning systems. It is seen that these discrepancies are caused by the differences in the calculation methodology adopted by the 2 systems.