Search PubMed⌕ Search

Biomedical subjects

A den Boer

Publications and source records attributed to A den Boer.

20 records · Page 2Linked to original sources
PubMedDate not supplied

Comparison of brachytherapy strategies based on dose-volume histograms derived from quantitative intravascular ultrasound.

PURPOSE: We present in this paper the comparison, by simulation, of different treatment strategies based either on beta- or gamma-sources, both with and without a centering device. Ionizing radiation to prevent restenosis is an emerging modality in interventional cardiology. Numerous clinical studies are presently being performed or planned, but there is variability in dose prescription, and both gamma- and beta-emitters are used, leading to a wide range of possible dose distributions over the arterial vessel wall. This paper discusses the potential merits of dose-volume histograms (DVH) based on three-dimensional (3-D) reconstruction of electrocardiogram (ECG)-gated intravascular ultrasound (IVUS) to compare brachytherapy treatment strategies. MATERIALS AND METHODS: DVH describe the cumulative distribution of dose over three specific volumes: (1) at the level of the luminal surface, a volume was defined with a thickness of 0.1 mm from the automatically detected contour of the highly echogenic blood-vessel interface; (2) at the level of the IVUS echogenic media-adventitia interface (external elastic lamina [EEL]), an adventitial volume was computed considering a 0.5-mm thickness from EEL; and (3) the volume encompassed between the luminal surface and the EEL (plaque + media). The IVUS data used were recorded in 23 of 31 patients during the Beta Energy Restenosis Trial (BERT) conducted in our institution. RESULTS: On average, the minimal dose in 90% of the adventitial volume was 37 +/- 16% of the prescribed dose; the minimal dose in 90% of the plaque + media volume was 58 +/- 24% and of the luminal surface volume was 67 +/- 31%. The minimal dose in the 10% most exposed luminal surface volume was 296 +/- 42%. Simulations of the use of a gamma-emitter and/or a radioactive source train centered in the lumen are reported, with a comparison of the homogeneity of the dose distribution. CONCLUSIONS: It is possible to derive DVH from IVUS, to evaluate the dose delivered to different parts of the coronary wall. This process should improve our understanding of the mechanisms of action of brachytherapy.

Brachytherapy↗
PubMedDate not supplied

Endovascular brachytherapy in coronary arteries: the Rotterdam experience.

PURPOSE: The use of endovascular coronary brachytherapy to prevent restenosis following percutaneous transluminal coronary angioplasty (PTCA) began in April 1997 at the Department of Interventional Cardiology of the Thoraxcenter at the University Hospital of Rotterdam. This article reviews the more than 250 patients that have been treated so far. METHODS AND MATERIALS: The Beta-Cath System (Novoste), a manual, hydraulic afterloader with 12 90Sr seeds, was used in the Beta Energy Restenosis Trial (BERT-1.5, n = 31), for compassionate use (n = 25), in the Beta-Cath System trial (n = 27) and in the Beta Radiation in Europe (BRIE, n = 14). Since the Beta-Cath System has been commercialized in Europe, 57 patients have been treated and registered in RENO (Registry Novoste). In the Proliferation Reduction with Vascular Energy Trial (PREVENT), 37 patients were randomized using the Guidant-Nucletron remote control afterloader with a 32P source wire and a centering catheter. Radioactive 32P coated stents have been implanted in 102 patients. In the Isostent Restenosis Intervention Study 1 (IRIS 1), 26 patients received a stent with an activity of 0.75-1.5 microCi, and in the IRIS 2 (European 32P dose response trial), 40 patients were treated with an activity of 6-12 microCi. In two consecutive pilot trials, radioactive stents with non-radioactive ends (cold-end stents) and with ends containing higher levels of activity (hot-end stents) were implanted in 21 and 17 patients, respectively. RESULTS: In the BERT-1.5 trial, the radiation dose, prescribed at 2 mm from the source train (non-centered), was 12 Gy (10 patients), 14 Gy (10 patients) and 16 Gy (11 patients). At 6-month follow-up, 8 out of 28 (29%) patients developed restenosis. The target lesion revascularization rate (TLR) was 7 out of 30 (23%) at 6 months and 8 out of 30 (27%) at 1 year. Two patients presented with late thrombosis in the first year. For compassionate use patients, a restenosis rate (RR) of 53% was observed. In the PREVENT trial, 34 of 37 patients underwent an angiographic 6-month follow-up. The doses prescribed at 0.5 mm depth into the vessel wall were 0 Gy (8), 28 Gy (9), 35 Gy (11) and 42 Gy (8). TLR was 14% in the irradiated patients and 25% in the placebo group. One patient developed late thrombosis. In the IRIS 1 trial, 23 patients showed an RR of 17% (in-stent). In the IRIS 2 trial, in-stent restenosis was not seen in 36 patients at 6-month follow-up. However, a high RR (44%) was observed at the stent edges. CONCLUSIONS: The integration of vascular brachytherapy in the catheterization laboratory is feasible and the different treatment techniques that are used are safe. Problems, such as edge restenosis and late thrombotic occlusion, have been identified as limiting factors of this technique. Solutions have been suggested and will be tested in future trials.

Angioplasty, Balloon, Coronary↗