Dosimetry and prescription in liver radioembolization with 90Y microspheres: 3D calculation of tumor-to-liver ratio from global 99mTc-MAA SPECT information.

Dosimetry in liver radioembolization with 90Y microspheres is a fundamental tool, both for the optimization of each treatment and for improving knowledge of the treatment effects in the tissues. Different options are available for estimating the administered activity and the tumor/organ dose, among them the so-called partition method. The key factor in the partition method is the tumor/normal tissue activity uptake ratio (T/N), which is obtained by a single-photon emission computed tomography (SPECT) scan during a pre-treatment simulation. The less clear the distinction between healthy and tumor parenchyma within the liver, the more difficult it becomes to estimate the T/N ratio; therefore the use of the method is limited. This study presents a methodology to calculate the T/N ratio using global information from the SPECT. The T/N ratio is estimated by establishing uptake thresholds consistent with previously performed volumetry. This dose calculation method was validated against 3D voxel dosimetry, and was also compared with the standard partition method based on freehand regions of interest (ROI) outlining on SPECT slices. Both comparisons were done on a sample of 20 actual cases of hepatocellular carcinoma treated with resin microspheres. The proposed method and the voxel dosimetry method yield similar results, while the ROI-based method tends to over-estimate the dose to normal tissues. In addition, the variability associated with the ROI-based method is more extreme than the other methods. The proposed method is simpler than either the ROI or voxel dosimetry approaches and avoids the subjectivity associated with the manual selection of regions.

Ionizing radiation in patients with Crohn´s disease. Estimation and associated factors.

INTRODUCTION: exposure to ionizing radiation is associated with an increased risk of developing tumors. Patients with Crohn's disease (CD) usually require multiple imaging tests using this type of radiation. OBJECTIVES: the objectives of this study were to estimate the total dose of ionizing radiation received by patients with Crohn's disease during their course and to identify the factors associated with higher radiation doses. METHODS: two hundred thirty-five CD patients diagnosed between 1972 and 2010 were included. The effective dose (ED) received by each patient was calculated retrospectively based on the number of gastrointestinal transit studies and computed tomography scans performed. Considering recent epidemiological studies, an ED greater than or equal to 50 mSv was used as the cut-off point for increased risk of developing cancer. RESULTS: the mean ED received per patient was 33.4 mSv (95% CI 29.3-37.5). A total of 49 (20.8%) patients received an ED ≥ 50 mSv. The following factors were identified as independent predictors associated with an ED ≥ 50 mSv: Age older than 40 years, need for surgery, age under 16 years at diagnosis and disease duration over 8 years. CONCLUSIONS: a substantial proportion of patients with Crohn's disease receive high doses of potentially carcinogenic ionizing radiation. Identification of the most susceptible patients to receive high doses of radiation, monitoring of effective doses received and the use of imaging techniques that do not require ionizing radiation (MR enterography, abdominal ultrasound) could contribute in reducing patients' exposure to potentially carcinogenic ionizing radiation.

Radiación ionizante en pacientes con enfermedad de Crohn. Estimación y factores asociados / Ionizing radiation in patients with Crohn's disease. Estimation and associated factors

Introducción: la exposición a radiación ionizante se asocia a un mayor riesgo de desarrollar tumores. Los pacientes con enfermedad de Crohn requieren habitualmente múltiples pruebas de imagen que utilizan este tipo de radiación. Objetivos: los objetivos de este estudio son estimar la dosis total de radiación ionizante recibida por pacientes con enfermedad de Crohn a lo largo de su evolución e identificar los factores asociados a dosis de radiación más altas. Métodos: se incluyeron 235 pacientes con enfermedad de Crohn diagnosticados entre 1972 y 2010. Se calculó retrospectivamente la dosis efectiva (DE) recibida por cada paciente, teniendo en cuenta los tránsitos gastrointestinales y las tomografías computarizadas que se habían realizado. Basados en estudios epidemiológicos previos, se consideró un valor umbral de DE ≥ 50 mSv de mayor riesgo de desarrollar cáncer. Resultados: la media de DE recibida por paciente fue 33,4 mSv (IC 95% 29,3-37,5). Un total de 49 (20,8%) pacientes recibió una DE >= 50 mSv. Se identificaron como factores predictivos independientes asociados a una DE >= 50 mSv: edad mayor de 40 años, necesidad de cirugía, edad al diagnóstico menor 16 años y tiempo de evolución mayor de 8 años. Conclusiones: un porcentaje considerable de pacientes con enfermedad de Crohn recibe dosis elevadas de radiación ionizante potencialmente carcinogénicas. La identificación de los pacientes mas susceptibles a recibir dosis altas de radiación, la monitorización de la dosis efectiva recibida y la utilización de pruebas de imagen que no utilizan radiación ionizante (enterorresonancia, ecografía abdominal), podrían contribuir a reducir la exposición a la radiaciones ionizantes potencialmente carcinogénicas(AU)

Introduction: exposure to ionizing radiation is associated with an increased risk of developing tumors. Patients with Crohn’s disease (CD) usually require multiple imaging tests using this type of radiation. Objectives: the objectives of this study were to estimate the total dose of ionizing radiation received by patients with Crohn’s disease during their course and to identify the factors associated with higher radiation doses. Methods: two hundred thirty-five CD patients diagnosed between 1972 and 2010 were included. The effective dose (ED) received by each patient was calculated retrospectively based on the number of gastrointestinal transit studies and computed tomography scans performed. Considering recent epidemiological studies, an ED greater than or equal to 50 mSv was used as the cut-off point for increased risk of developing cancer. Results: the mean ED received per patient was 33.4 mSv (95% CI 29.3-37.5). A total of 49 (20.8%) patients received an ED >= 50 mSv. The following factors were identified as independent predictors associated with an ED >= 50 mSv: Age older than 40 years, need for surgery, age under 16 years at diagnosis and disease duration over 8 years. Conclusions: a substantial proportion of patients with Crohn’s disease receive high doses of potentially carcinogenic ionizing radiation. Identification of the most susceptible patients to receive high doses of radiation, monitoring of effective doses received and the use of imaging techniques that do not require ionizing radiation (MR enterography, abdominal ultrasound) could contribute in reducing patients’ exposure to potentially carcinogenic ionizing radiation(AU)