Dosimetry in liver radioembolization with Y 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.

Purpose: Total body irradiation (TBI) is a technique that requires special equipment to control “in vivo” the dose to the patient because it is a complex technique performed in extraordinary conditions. There are several devices to perform this task (diodes, TLDs, ionization chambers, MOSFET). In this paper we study the possibility of performing these measurements with radiochromic films EBT3 properly calibrated. This method has been compared to the PTW diodes system for TBI. Methods: Once made the TC to the patients, we measured different thicknesses of the relevant areas of the body (head, neck, chest with or without arms, umbilicus area, knees and ankles); for each of these thicknesses we measured dose rate (cGy / UM) in RW3 phantom, in TBI conditions, with ionization chamber in the center; in turn, the input diode and the output of each configuration is placed to assign dose to each set of diodes. Movie calibration is performed according to manufacturer's recommendations but TBI conditions. The dose at the center of each thickness compared to a linear interpolation of the dose at the entrance and exit, resulting in an adequate approximation. Finally in each session for each patient put a piece of film (2×2 cm2) at the entrance and another at the exit in each area, obtaining these readings and interpolating the estimated center dose, as with the diodes. Results: These results show a greater homogeneity in the distribution for use with film and validate the use of the same for this task and, if necessary, to avoid purchasing diode group if they have not. Conclusion: By using radiochromic films for this technique gives us a proper calculation of the dose received by the patient in the absence of other methods, or gives us a second additional track that already used normally.

Purpose: To present a simple and feasible method of voxel‐S‐value (VSV) dosimetry calculation for daily clinical use in radioembolization (RE) with 90Y microspheres. Dose distributions are obtained and visualized over CT images. Methods: Spatial dose distributions and dose in liver and tumor are calculated for RE patients treated with Sirtex Medical miscrospheres at our center. Data obtained from the previous simulation of treatment were the basis for calculations: Tc‐99m maggregated albumin SPECT‐CT study in a gammacamera (Infinia, General Electric Healthcare.). Attenuation correction and ordered‐subsets expectation maximization (OSEM) algorithm were applied.For VSV calculations, both SPECT and CT were exported from the gammacamera workstation and registered with the radiotherapy treatment planning system (Eclipse, Varian Medical systems). Convolution of activity matrix and local dose deposition kernel (S values) was implemented with an in‐house developed software based on Python code. The kernel was downloaded from http://www.medphys.it. Final dose distribution was evaluated with the free software Dicompyler. Results: Liver mean dose is consistent with Partition method calculations (accepted as a good standard). Tumor dose has not been evaluated due to the high dependence on its contouring. Small lesion size, hot spots in health tissue and blurred limits can affect a lot the dose distribution in tumors. Extra work includes: export and import of images and other dicom files, create and calculate a dummy plan of external radiotherapy, convolution calculation and evaluation of the dose distribution with dicompyler. Total time spent is less than 2 hours. Conclusion: VSV calculations do not require any extra appointment or any uncomfortable process for patient. The total process is short enough to carry it out the same day of simulation and to contribute to prescription decisions prior to treatment. Three‐dimensional dose knowledge provides much more information than other methods of dose calculation usually applied in the clinic.

Purpose: In studies related to breast cancer and mortality, convincing evidence of an increased risk of cardiac morbidity following irradiation for leftsided breast cancer exists. The use of a breath hold technique enables a significant decrease of the dose to the heart as well as to the left anterior descending coronary artery (LAD). The purpose of deep inspiration Breath Hold (BH) is to expand the chest cavity during radiotherapy, which increases the distance between the breast to be treated and the heart. This allows for a lower heart dose as well as better PTV coverage. Methods: A study of 30 patients is showed. All patients underwent a free breathing (FB) and BH CT scan in supine treatment. Previously, the patient receives personal training to perform an adequate breathing and follows her own breathing cycle with glasses connected to the BH device. For simulation and treatment the same procedure as in the CT acquisition is performed. In the treatment, the patient placing includes daily image included in dosimetry. Results: The analysis compares the doses received in heart and LAD with FB and BH treatment. It presents data of medium dose with FB CT and BH CT and average and maximum dose (dose to 0.2 cm3) in LAD. The PTV coverage dose are between 95‐107 percentage of the prescribed dose is not present neither in the lung dose (V20) does not vary significantly.The DVH medium of LAD and heart (FB vs BH) is showed as well. Conclusion: The effects of radiation on the heart are late effects, which usually appear between 10 and 15 years after treatment. In young patients a dose reduction as drastic as that observed implies a reduced risk of heart disease a Result of radiation, which significantly increases the probability of survival over 10 years.

Purpose: To compare planning results of intensity modulated radiotherapy (IMRT) with conformal external radiotherapy (3DCRT) for oesophagus cancer treatment. Methods: IMRT and 3DCRT options were planned for 6 patients of oesophagus cancer and dose‐volume histograms were evaluated for the main organs at risk: lungs, heart and spinal cord. The prescription dose was 54Gy in all cases and the treatment planning system used was Eclipse (10.0 version with Anisotropic Analytical Algorithm 10.0.28 version). A conventional field arrangement was applied for 3DCRT with antero‐posterior and lateral opposed fields and a 3 field technique (antero‐posterior and 2 oblique posterior entrances) for IMRT. Results: Similar PTV coverage was found and spinal cord maximal dose was under recommendations in both cases. Main difference was in lung and heart dose. A significant reduction on heart dose was obtained with IMRT: mean values of V30, V40, V45 and V50 (volume irradiated with 30, 40, 45 and 50Gy) were reduced by 13.2, 9.9, 2.7 and 2.3Gy respectively. For lungs, mean dose and V5 were quite similar between IMRT and 3DCRT (less than 1Gy of difference); a mean reduction of 2.8Gy and a mean increase of 5.6Gy were found for V10 and V20 respectively. Compared with other IMRT options reported in the literature, such as 5 or more field entrances, a reduction on lung volume irradiated at low dose (V5) was observed. Rest of parameters were close to shown values in this work. Conclusion: This study shows the dosimetric advantages of using a three‐field IMRT technique for heart and lung dose values, keeping the rest of parameters within tolerances. Special attention was put in low lung dose parameters.