Biomedical subjects

V Massullo

Publications and source records attributed to V Massullo.

22 records · Page 2Linked to original sources

PubMedDate not supplied

Initial studies with gamma radiotherpay to inhibit coronary restenosis.

BACKGROUND: Early studies indicate brachytherapy is a potential clinical treamtent for restenosis after coronary angioplasty procedures. The objective of this study was to evaluate the safety and efficacy of gamma radiation plus stenting in patients' previous restenosis. METHODS: In patients with previous coronary restenosis, balloon dilatation and/or coronary stenting was undertaken and then patients were randomly assigned to receive either Iridium-192 or placebo. Quantitative coronary angiographic, intravascular ultrasonographic, and clinical follow-up was obtained. RESULTS: Of the 55 patients enrolled, 26 were treated with Iridium-192 and 29 were in the placebo group. Late luminal loss was significantly lower in the treated group compared to the placebo group (0.38 +/- 1.06 mm vs. 1.03 +/- 0.97 mm, p = 0.03). Restenosis (stenosis of > or = 50% at follow-up) was found in 17% of treated patients compared to 54% of placebo patients (p = 0.01). The need for target lesion revascularization was observed in 12% of patients in the treated group compared to 45% in the placebo group (p = 0.01). CONCLUSIONS: In this initial trial, at 12 months follow-up, patients with previous restenosis were benefited by catheter-based gamma radiation therapy.

Angioplasty, Balloon, Coronary↗

PubMedDate not supplied

The American Brachytherapy Society perspective on intravascular brachytherapy.

BACKGROUND: Recent clinical studies indicate that intravascular brachytherapy (IVB) can reduce the rate of restenosis substantially after angioplasty procedures. However, no clinical guidelines exist for optimal therapy. METHODS: The members of the IVB Subcommittee of the American Brachytherapy Society (ABS) identified the areas of consensus and controversies in IVB to issue the ABS perspective on IVB, based on analysis of published reports and the clinical experience of the members in brachytherapy. RESULTS: IVB is still experimental. The long-term efficacy, toxicity, the target tissue, and dose required for IVB are not established. The ABS recommends that IVB procedures must be performed, with careful attention to radiation-related issues, in the context of controlled multidisciplinary clinical trials with the approval of the institutional review board, the Nuclear Regulatory Commission, the Food and Drug Administration, and under an Investigational Device Exemption. The therapeutic radiologist, with a qualified radiation physicist, is responsible for dose prescription and delivery and needs to be present during the IVB procedure as part of this multidisciplinary team. The long-term outcome from these studies should be reviewed critically and published in peer-reviewed journals. The ABS endorsed the dosimetric guidelines of the American Association of Physicists in Medicine Task Group 60 (AAPM TG-60) report. The ABS recommends that dose specification be defined clearly; to allow comparisons between studies, the dose should be prescribed at 2 mm from the source for intracoronary brachytherapy and at an average luminal radius of +2 mm for peripheral vascular brachytherapy. The prescription doses at the above point is generally in the 12-18 Gy range. Comprehensive procedures for quality assurance, radiation protection, and emergencies should be in place before initiating an IVB program. Higher energy beta sources, lower energy gamma sources, dose-volume histograms, and correlation of three-dimensional reconstructions of delivered dose with patterns of failure are areas for further research. CONCLUSION: The ABS perspective on IVB is presented to assist the interventional team in developing protocols for the use of IVB in the prevention of restenosis. Long-term outcome data with a standardized reporting system are needed to establish the role of brachytherapy in preventing vascular restenosis. Endovascular brachytherapy is a new and evolving modality, and these recommendations are subject to modifications as new data become available.

Brachytherapy↗

PubMedDate not supplied

Theoretical assessment of late cardiac complication from endovascular brachytherapy for restenosis prevention.

PURPOSE: In this study, a theoretical assessment of late cardiac complication from endovascular brachytherapy is performed using the integrated logistic model. MATERIALS AND METHODS: Calculation were performed for various lengths of Ir-192 sources using alpha/beta = 3.2 for the endpoint of chronic ischemia, TD50/5 = 7,000 cGy, and TD5/5 = 5,000 cGy. The dose distribution over a standard heart was divided into volume elements with uniform dose (dose-volume histogram). Using linear-quadratic equation, the dose in each of the volume elements was converted into dose equivalent to standard fractionation external beam irradiation. The normal tissue complication probability (NTCP) for each volume element was calculated and combined together to arrive at the cumulative risk of late cardiac complication. The NTCP was plotted against the dose prescribed at 2-mm radial distance for four treatment lengths. RESULTS: (1) The overall risk of late cardiac toxicity (chronic ischemia within 5 years) was estimated to be less than 1% for current clinical trials using Ir-192. (2) There is a volume effect with higher risk for larger irradiated volume, which can come from longer treatment time, the same dose prescribed at a greater radial distance, and a longer source train. (3) The NTCP vs. dose demonstrates a sigmoidal relationship. There is a threshold dose (about 500 cGy), below which the risk is minimal; the gradient of the curve is greater for longer treatment length. CONCLUSION: If the prediction from this model is validated with clinical data, it will contribute to guidelines for dose prescription, dose escalation, evaluation of new source design, and multivessel treatment.

Angioplasty, Balloon, Coronary↗

PubMedDate not supplied

Theoretical assessment of dose-rate effect in endovascular brachytherapy.

PURPOSE: Several prospective randomized clinical trials utilizing endovascular brachytherapy after coronary angioplasty have shown promising preliminary results. Numerous clinical trials have been initiated to evaluate different delivery systems and source types. In this study, the dose-rate effect is investigated using a biophysical model derived from linear-quadratic formalism. MATERIALS AND METHODS: The dose-rate effect is quantified using the Dale's formulation, which is based on a linear-quadratic model. This model converts the total absorbed dose into the biological equivalent dose (BED) based on the dose rate, total dose, treatment duration, biological endpoint (alpha/beta ratio), and sublethal damage repair constant. The calculations are performed for two common source configurations used in current clinical trials (192Ir and 90Sr/Y). RESULTS: At smaller radial distance, the dose rate is higher, hence BED increases due to the increase in the relative effectiveness per unit dose (RE) and absorbed dose for a given treatment duration. For 90Sr/Y source, a similar trend is observed; however, it is at a much greater magnitude. The RE for 192Ir is close to unity, which is equivalent to that of external beam irradiation. CONCLUSION: Although current clinical trials in endovascular brachytherapy report similar absorbed dose, the biological effects may be different due to the extremely high gradient of dose rate near the sources, a variety of isotopes and delivery systems, and different dose prescriptions. If the theoretical predictions in this study are validated in clinical trials, the proposed model can be useful to compare different protocols, design new delivery systems and isotopes, and optimize how radiation is delivered.

Biophysical Phenomena↗