RESUMEN
PURPOSE: Motions of the bladder and rectum during pelvic irradiation are considered as major causes of geometrical uncertainties. As a result, the volume status of these organs is changed and the definition of the treatment margins is imperative. The aim of this study was, firstly, to determine these margins, comparing series of CT scans, performed at simulation time, with empty (EB) and full bladder (FB) and, secondly, to evaluate the dose volume histograms (DVHs) of tumor and rectum using standard treatment margins. METHODS: Fifteen patients with muscle-invading urinary bladder carcinoma underwent two scan series with EB and FB bladder during radiotherapy (RT) simulation. Gross tumor volume (GTV), clinical target volume (CTV), planning treatment volume (PTV) and organs at risk (OAR) were contoured. Displacements of the bladder wall were determined at all directions. Cumulative DVHs were generated for the volumes of interest. Using the same beam arrangements for both the EB and FB CT series, DVHs were also produced. RESULTS: The mean bladder volume was 119.3±55.9 cm3 and 264.3±145.7 cm3 for EB and FB CT series, respectively (p<0.001). The maximum bladder wall displacement was observed at cranial direction (2.2±0.6 cm for the EB vs. 3.4±1.0 cm for the FB series; p<0.001) and at caudal direction (2.3±0.6 cm for the EB vs. 3.6±1.0 cm for the FB series; p<0.001). Standard anisotropic margins of 2 cm in craniocaudal and posterior-anterior directions and 1.2 cm in lateral direction gave coverage to 75% of all bladder movements caused by FB. Analysis of DVHs and tumor control probability (TCP) calculations gave same results (74%), while normal tissue complication probability (NTCP) of the rectum showed no significant changes. CONCLUSION: CT scans series with empty and full bladder, performed at simulation time, could offer a potential advantage to evaluate the target expansion necessary to cover the bladder wall for each patient, giving more information about safe margining.
Asunto(s)
Planificación de la Radioterapia Asistida por Computador/métodos , Neoplasias de la Vejiga Urinaria/radioterapia , Anciano , Femenino , Humanos , Masculino , Persona de Mediana Edad , Tomografía Computarizada por Rayos X , Neoplasias de la Vejiga Urinaria/patologíaRESUMEN
Endovascular brachytherapy (EVBT) is an established treatment to reduce the probability of restenosis after a percutaneous coronary intervention. The purpose of this study was to assess (1) the manufacturer's stated dosimetric data for (90)Sr/(90)Y source trains to be used in EVBT and (2) the procedure-related radiation burden. The radiation fields in water around six (90)Sr/(90)Y source trains were studied using phantoms made of 'solid water' and MD55-2 radiochromic films. The water equivalence of the phantom material was tested by applying quantitative computed tomography. Thermoluminescence dosemeters were used to assess personal radiation burden and crosscheck the dose distribution along the source trains. Technical failure was observed in one source train and this train was excluded from analysis. The measured dose rate in water at 2 mm radial distance was on average 8% higher than the manufacture's stated value (range of measured to stated values 1.05--1.15). The dose rate decreased exponentially with radial distance between 2 and 6 mm. The dose rate in contact with the source viewing window of the delivery devices ranged between 0.5 and 7.5 mGy h(-1). Low-energy photons were the main contributors to personal dose.
Asunto(s)
Prótesis Vascular , Braquiterapia/métodos , Exposición a Riesgos Ambientales/análisis , Dosimetría por Película/métodos , Garantía de la Calidad de Atención de Salud/métodos , Medición de Riesgo/métodos , Radioisótopos de Estroncio/análisis , Radioisótopos de Itrio/análisis , Carga Corporal (Radioterapia) , Braquiterapia/normas , Análisis de Falla de Equipo/métodos , Dosimetría por Película/normas , Humanos , Dosis de Radiación , Protección Radiológica/métodos , Efectividad Biológica Relativa , Factores de Riesgo , Radioisótopos de Estroncio/uso terapéutico , Radioisótopos de Itrio/uso terapéuticoRESUMEN
BACKGROUND: Parallel, thin (<100 microm) planes of synchrotron-generated X rays, have been shown to spare normal tissues and preferentially damage tumors in animal models. The aim of the present study was to assess the effect of such microbeams directed unidirectionally on angioplasted rat carotid arteries. METHODS AND MATERIALS: Three groups of Sprague-Dawley rats were studied: (a) rats with normal, untreated arteries, (b) rats treated by balloon angioplasty, but not irradiated, and (c) rats treated with balloon angioplasty and exposed to single fraction, unidirectional, parallel, microbeams an hour after angioplasty. The microbeam array, 15 mm widex7.6 mm high, consisting of 27-microm-wide beam slices, spaced 200 microm center-to-center laterally traversed the damaged artery. The in-depth in-beam dose was 150 Gy, the "valley" dose (dose midway between microbeams resulting mainly from X-ray scattering) was 4.5 Gy on average, and the "integrated" (averaged) dose was 26 Gy. RESULTS: Microbeam irradiation, as given in the present study, was tolerated, but was insufficient to significantly suppress the neointimal hyperplasia. DISCUSSION: The microbeam dose used is considered low. Dose escalation would be necessary to reach conclusive results regarding the X-ray microbeam efficacy to control restenosis.
Asunto(s)
Angioplastia de Balón/efectos adversos , Arteria Carótida Común/patología , Arteria Carótida Común/cirugía , Estenosis Carotídea/terapia , Oclusión de Injerto Vascular/etiología , Oclusión de Injerto Vascular/radioterapia , Animales , Arteria Carótida Común/efectos de la radiación , Modelos Animales de Enfermedad , Relación Dosis-Respuesta en la Radiación , Hiperplasia/etiología , Hiperplasia/radioterapia , Modelos Cardiovasculares , Ratas , Ratas Sprague-Dawley , Túnica Íntima/patología , Túnica Íntima/efectos de la radiación , Rayos XRESUMEN
BACKGROUND: The effects of brachytherapy performed 24 h postintervention in de novo native coronary artery lesions. METHODS AND RESULTS: Thirty-nine patients with 39 de novo coronary artery lesions were randomised to prompt (immediately after intervention, n=21) or delayed (24 h later, n=18) beta brachytherapy ((90)Sr/(90)Y) after been successfully revascularized with stenting. Clinical follow-up data up to 21 months (median time) were compared. After irradiation and at 6-month follow-up, paired volumetric analysis of the stented segment and the 5-mm proximal and distal reference segments was performed; this included measurements of the external elastic membrane, lumen, plaque, and media (external elastic membrane minus lumen), stent and intima hyperplasia (stent minus lumen). Baseline clinical and angiographic characteristics were similar in the two groups. Postintervention measurements of stent, lumen, and intima hyperplasia volumes as well as postintervention minimum lumen cross-sectional areas were not different. In the stented segments and in the segments 5 mm proximal and distal to the stent, similar changes of all IVUS measurements were measured in the two patient groups, but in the lumen volume at the proximal stent edge of patients irradiated 24 h postinjury. At 21 months median follow-up time, target lesion revascularization (TLR) was performed in 8 patients (38%) in the prompt irradiation group compared with 3 (17%) in the delayed (P=.17). CONCLUSION: Beta irradiation is similarly effective whether performed immediately after percutaneous coronary intervention or 24 h later.
Asunto(s)
Angioplastia Coronaria con Balón , Braquiterapia/métodos , Estenosis Coronaria/diagnóstico por imagen , Estenosis Coronaria/terapia , Oclusión de Injerto Vascular/prevención & control , Stents , Anciano , Angioplastia Coronaria con Balón/efectos adversos , Angiografía Coronaria , Femenino , Estudios de Seguimiento , Oclusión de Injerto Vascular/diagnóstico , Oclusión de Injerto Vascular/etiología , Humanos , Masculino , Persona de Mediana Edad , Stents/efectos adversos , Factores de Tiempo , Resultado del Tratamiento , Ultrasonografía IntervencionalRESUMEN
PURPOSE: To study the dose and time effect of external beam irradiation on the morphometry of both angioplasted and nonangioplasted arteries in a hypercholesterolemic rabbit model. METHODS AND MATERIALS: Eight groups of rabbit femoral arteries were studied: arteries (a) with no intervention, (b) irradiated with a 12-Gy 6 MV X-ray dose, (c) with a 18-Gy, (d) treated with balloon angioplasty, (e) dosed with 12-Gy half an hour post-angioplasty, (f) dosed with 18-Gy half an hour post-angioplasty, (g) dosed with 12-Gy 48 h post angioplasty, (g) dosed with 18-Gy 48 h post angioplasty. RESULTS: External irradiation at either 12 or 18 Gy was not found to change vessel morphometry in noninjured arteries. The 12-Gy dose given soon after angioplasty further increased percentage stenosis (63% on the average), despite the preservation of the lumen cross-sectional area. Positive remodeling was not observed in arteries given 18-Gy half an hour post angioplasty to counterbalance the increased neointimal formation. Therefore, this treatment resulted in a drastic reduction in lumen area and in enhancement of percentage stenosis (84% on the average). On the contrary, the delayed irradiation of the angioplasted arteries at either 12 or 18 Gy was not found to influence any of the studied morphometric parameters 5 weeks after angioplasty. CONCLUSIONS: Uniform external beam irradiation up to 18 Gy was well tolerated by intact femoral arteries. Prompt 12- or 18-Gy irradiations accentuated percentage stenosis. However the lumen cross-sectional area was preserved only at the lower dose point. Delayed irradiation at any dose did not influence the restenosis process.