Biomedical subjects

Dattatreyudu Nori

Publications and source records attributed to Dattatreyudu Nori.

4 recordsLinked to original sources

PubMed2006

Single course IMRT plan to deliver 45 Gy to seminal vesicles and 81 Gy to prostate in 45 fractions.

We treat prostate and seminal vesicles (SV) to 45 Gy in 25 fractions (course 1) and boost prostate to 81 Gy in 20 more fractions (course 2) with Intensity Modulated Radiation Therapy (IMRT). This two-course IMRT with 45 fractions delivered a non-uniform dose to SV and required two plans and two QA procedures. We used Linear Quadratic (LQ) model to develop a single course IMRT plan to treat SV to a uniform dose, which has the same biological effective dose (BED) as that of 45 Gy in 25 fractions and prostate to 81 Gy, in 45 fractions. Single course IMRT plans were compared with two-course IMRT plans, retrospectively for 14 patients. With two-course IMRT, prescription to prostate and SV was 45 Gy in 25 fractions and to prostate only was 36 Gy in 20 fractions, at 1.8 Gy/fraction. With 45-fraction single course IMRT plan, prescription to prostate was 81 Gy and to SV was 52 or 56 Gy for a alpha/beta of 1 and 3, respectively. 52 Gy delivered in 45 fractions has the same BED of 72 Gy3 as that of delivering 45 Gy in 25 fractions, and is called Matched Effective Dose (MED). LQ model was used to calculate the BED and MED to SV for alpha/beta values of 1-10. Comparison between two-course and single course IMRT plans was in terms of MUs, dose-max, and dose volume constraints (DVC). DVC were: 95% PTV to be covered by at least 95% of prescription dose; and 70, 50, and 30% of bladder and rectum should not receive more than 40, 60, and 70% of 81 Gy. SV Volumes ranged from 2.9-30 cc. With two-course IMRT plans, mean dose to SV was non-uniform and varied between patients by 48% (54 to 80 Gy). With single-course IMRT plan, mean dose to SV was more uniform and varied between patients by only 9.6% (58.2 to 63.8 Gy), to deliver MED of 56 Gy for alpha/beta - 1. Single course IMRT plan MUs were slightly larger than those for two-course IMRT plans, but within the range seen for two-course plans (549-959 MUs, n=51). Dose max for single-course plans were similar to two-course plans. Doses to PTV, rectum and bladder with single course plans were as per DVC and comparable to two-course plans. Single course IMRT plan reduces IMRT planning and QA time to half.

Adenocarcinoma↗

PubMed2004

HDR brachytherapy with surface applicators: technical considerations and dosimetry.

HDR surface molds offer an alternative radiotherapy modality to electrons for the treatment of skin lesions. Treatment planning and dosimetry are discussed for two types of surface molds used in our clinic. Standard rectangular applicators are used on a variety of sites where surface curvature is minimal. In these cases an idealized planar geometry is used for treatment planning dose calculations. The calculations yield treatment dose uniformity at the prescription depth in tissue as well as skin dose, as a percentage of the treatment dose, and its dose uniformity. The availability of optimization techniques results in superior dose uniformity at depth but the dose at the skin has to be carefully evaluated. We have studied the dependence of these dosimetric parameters on the size of the surface mold and the type of optimization procedure used in the dosimetry calculations. The second type of surface applicator involves the use of a customized silicone rubber mold attached to a thermoplastic mask of the patient. We have used them to treat lesions of the face where surface curvatures are appreciable and reproducibility of setup is more critical. In these cases a CT data set is used for reconstruction of the catheters, activation of relevant dwell positions and dosimetry, including optimization. Towards establishing effective methods for quality assurance of the optimized HDR surface mold planning calculations, we have compared their dosimetry to both a classical brachytherapy system and to one based on an analytical model of the applicator. The classical system yields an independent verification of the integrated activity used in the planning calculations, whereas the analytical model is used to evaluate depth dose dependence on mold size and optimization.

Brachytherapy↗

PubMed2004

The impact of technological advances on the evolution of 3D conformal brachytherapy for early prostate cancer.

Permanent implantation of I-125 and Pd-103 seeds is one of the widely used treatment options for the early stage prostate cancer with minimum normal tissue complications and long-term local control of the tumor. This is possible because of several technological advances made in the past decade to better understand the procedural aspects of implantations with the desired clinical outcome and with acceptable morbidities. In addition, with the widespread use of PSA testing, more widely disseminated information about prostate cancer and increased patient awareness, over 70% of patients are diagnosed early with localized disease and therefore are candidates for definitive local therapy. Delineation of soft tissue structures including the prostate, rectum, urethra and bladder has become more accurate with the use of imaging modalities including Ultrasound and MRI, with or without the CT. A re-evaluation of the dosimetric parameters of the radioactive sources has lead to a more precise estimate of the dose delivered to the prostate and the associated critical normal structures. Technological improvements in the post implant dosimetry have helped to understand the factors, which makes an implant a "good implant" or a "poor implant". Intraoperative treatment planning with on line dosimetry is emerging as one of the best approaches for prostate brachytherapy. In addition, better software is now available producing dose-volume histograms with 3D target and normal tissue reconstruction. The combination of seed implant followed by IMRT would provide scope for differentially boosting the regions under-dosed because of uncontrollable and unexpected reasons during the implant and unsuspected micro extensions of the tumor.

Brachytherapy↗

PubMed2002

Gynecologic brachytherapy I: Proper incorporation of brachytherapy into the current multimodality management of carcinoma of the cervix.

The incidence of carcinoma of the cervix has continuously declined over the past decades because of effective screening. The International Federation of Gynecology and Obstetrics (FIGO) clinical staging, though universally used, is considered inadequate either to determine the type of treatment or to predict treatment outcome. Over the last 10 years, treatment of cervical cancer has become increasingly sophisticated with advances in external beam and brachytherapy in the radiotherapeutic management of this carcinoma. In particular, brachytherapy plays a major role in enhancing both local control and survival. Experience to date suggests that either high-dose-rate (HDR) or low-dose-rate (LDR) brachytherapy, when properly applied, can be effective and give similar rates of local control with minimal complications. This article analyzes the current literature regarding treatment techniques of radiotherapy with special emphasis on brachytherapy integration to optimize radiotherapy treatment outcome.

Brachytherapy↗