Nonlinearity in MCF7 Cell Survival Following Exposure to Modulated 6 MV Radiation Fields: Focus on the Dose Gradient Zone

International audienceThe study of cell survival following exposure to nonuniform radiation fields is taking on particular interest because of the increasing evidence of a nonlinear relationship at low doses. We conducted in vitro experiments using the MCF7 breast cancer cell line. A 2.4 × 2.4 cm(2) square area of a T25 flask was irradiated by a Varian Novalis accelerator delivering 6 MV photons. Cell survival inside the irradiation field, in the dose gradient zone and in the peripheral zone, was determined using a clonogenic assay for different radiation doses at the isocenter. Increased cell survival was observed inside the irradiation area for doses of 2, 10, and 20 Gy when nonirradiated cells were present at the periphery, while the cells at the periphery showed decreased survival compared to controls. Increased survival was also observed at the edge of the dose gradient zone for cells receiving 0.02 to 0.01 Gy when compared with cells at the periphery of the same flask, whatever the isocenter dose. These data are the first to report cell survival in the dose gradient zone. Radiotherapists must be aware of this nonlinearity in dose response

Spleno-hepatic index to predict portal hypertension by equilibrium radionuclide ventriculography

International audienc

In-vivo dosimetry for conformal arc therapy using several MOSFET in stereotactic radiosurgery computed by an inverse model

In-vivo dosimetry is still a challenge in stereotactic radiosurgery since most of treatments are delivered using rotational technique with small fields. A realistic and practical solution for these treatments delivered in conformal radiotherapy is proposed to control the absorbed dose at isocentre, using multiple surface MOSFET measurements over an arc. On the one hand, a forward method was developed to optimize the location of the detectors at the patient surface, taking into account arc length, prescribed isocentre dose, collimator and field size. On the other hand, an inverse method was used to compute the dose at isocentre for conformal arc therapy in stereotactic radiosurgery, using MOSFET measurements. Finally, the reconstructed dose at isocentre was compared to real measurement, obtained for several detectors positioned at a phantom surface. Results show that the inverse method gives good results with five MOSFET equi-spaced positioned within the arc beam course: deviation between prescribed and computed average total dose at isocentre was below 2% both for 30×30 mm2 and 18×18 mm2 field siz

In-vivo dosimetry for conformal arc therapy using several MOSFET in stereotactic radiosurgery computed by an inverse model

In-vivo dosimetry is still a challenge in stereotactic radiosurgery since most of treatments are delivered using rotational technique with small fields. A realistic and practical solution for these treatments delivered in conformal radiotherapy is proposed to control the absorbed dose at isocentre, using multiple surface MOSFET measurements over an arc. On the one hand, a forward method was developed to optimize the location of the detectors at the patient surface, taking into account arc length, prescribed isocentre dose, collimator and field size. On the other hand, an inverse method was used to compute the dose at isocentre for conformal arc therapy in stereotactic radiosurgery, using MOSFET measurements. Finally, the reconstructed dose at isocentre was compared to real measurement, obtained for several detectors positioned at a phantom surface. Results show that the inverse method gives good results with five MOSFET equi-spaced positioned within the arc beam course: deviation between prescribed and computed average total dose at isocentre was below 2% both for 30×30 mm2 and 18×18 mm2 field siz

Comparison of commercial dosimetric software platforms in patients treated with 177 Lu‐DOTATATE for peptide receptor radionuclide therapy

International audiencePurpose: The aim of this study was to quantitatively compare five commercial dosimetric software platforms based on the analysis of clinical datasets of patients who benefited from peptide receptor radionuclide therapy (PRRT) with 177 Lu-DOTATATE (LUTATHERA® ).Methods: The dosimetric analysis was performed on two patients during two cycles of PRRT with 177 Lu. Single photon emission computed tomography/computed tomography images were acquired at 4, 24, 72, and 192 h post injection. Reconstructed images were generated using Dosimetry Toolkit® (DTK) from Xeleris™ and HybridRecon-Oncology version_1.3_Dicom (HROD) from HERMES. Reconstructed images using DTK were analyzed using the same software to calculate time-integrated activity coefficients (TIAC), and mean absorbed doses were estimated using OLINDA/EXM V1.0 with mass correction. Reconstructed images from HROD were uploaded into PLANET® OncoDose from DOSIsoft, STRATOS from Phillips, Hybrid Dosimetry Module™ from HERMES, and SurePlan™ MRT from MIM. Organ masses, TIACs, and mean absorbed doses were calculated from each application using their recommendations.esults: The majority of organ mass estimates varied by <9.5% between all platforms. The highest variability for TIAC results between platforms was seen for the kidneys (28.2%) for the two patients and the two treatment cycles. Relative standard deviations in mean absorbed doses were slightly higher compared with those observed for TIAC, but remained of the same order of magnitude between all platforms.Conclusions: When applying a similar processing approach, results obtained were of the same order of magnitude regardless of the platforms used. However, the comparison of the performances of currently available platforms is still difficult as they do not all address the same parts of the dosimetric analysis workflow. In addition, the way in which data are handled in each part of the chain from data acquisition to absorbed doses may be different, which complicates the comparison exercise. Therefore, the dissemination of commercial solutions for absorbed dose calculation calls for the development of tools and standards allowing for the comparison of the performances between dosimetric software platforms

Nonlinearity in MCF7 Cell Survival Following Exposure to Modulated 6 MV Radiation Fields

The study of cell survival following exposure to nonuniform radiation fields is taking on particular interest because of the increasing evidence of a nonlinear relationship at low doses. We conducted in vitro experiments using the MCF7 breast cancer cell line. A 2.4 × 2.4 cm 2 square area of a T25 flask was irradiated by a Varian Novalis accelerator delivering 6 MV photons. Cell survival inside the irradiation field, in the dose gradient zone and in the peripheral zone, was determined using a clonogenic assay for different radiation doses at the isocenter. Increased cell survival was observed inside the irradiation area for doses of 2, 10, and 20 Gy when nonirradiated cells were present at the periphery, while the cells at the periphery showed decreased survival compared to controls. Increased survival was also observed at the edge of the dose gradient zone for cells receiving 0.02 to 0.01 Gy when compared with cells at the periphery of the same flask, whatever the isocenter dose. These data are the first to report cell survival in the dose gradient zone. Radiotherapists must be aware of this nonlinearity in dose response

Comparison of commercial dosimetric software platforms in patients treated with 177Lu-DOTATATE for peptide receptor radionuclide therapy

Purpose The aim of this study was to quantitatively compare five commercial dosimetric software platforms based on the analysis of clinical datasets of patients who benefited from peptide receptor radionuclide therapy (PRRT) with 177Lu-DOTATATE (LUTATHERA®). Methods The dosimetric analysis was performed on two patients during two cycles of PRRT with 177Lu. Single photon emission computed tomography/computed tomography images were acquired at 4, 24, 72, and 192 h post injection. Reconstructed images were generated using Dosimetry Toolkit® (DTK) from Xeleris™ and HybridRecon-Oncology version_1.3_Dicom (HROD) from HERMES. Reconstructed images using DTK were analyzed using the same software to calculate time-integrated activity coefficients (TIAC), and mean absorbed doses were estimated using OLINDA/EXM V1.0 with mass correction. Reconstructed images from HROD were uploaded into PLANET® OncoDose from DOSIsoft, STRATOS from Phillips, Hybrid Dosimetry Module™ from HERMES, and SurePlan™ MRT from MIM. Organ masses, TIACs, and mean absorbed doses were calculated from each application using their recommendations. Results The majority of organ mass estimates varied by <9.5% between all platforms. The highest variability for TIAC results between platforms was seen for the kidneys (28.2%) for the two patients and the two treatment cycles. Relative standard deviations in mean absorbed doses were slightly higher compared with those observed for TIAC, but remained of the same order of magnitude between all platforms. Conclusions When applying a similar processing approach, results obtained were of the same order of magnitude regardless of the platforms used. However, the comparison of the performances of currently available platforms is still difficult as they do not all address the same parts of the dosimetric analysis workflow. In addition, the way in which data are handled in each part of the chain from data acquisition to absorbed doses may be different, which complicates the comparison exercise. Therefore, the dissemination of commercial solutions for absorbed dose calculation calls for the development of tools and standards allowing for the comparison of the performances between dosimetric software platforms.UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Ciencias Atómicas Nucleares y Moleculares (CICANUM

Feasibility and accuracy of gated blood pool SPECT equilibrium radionuclide ventriculography for the assessment of left and right ventricular volumes and function in patients with left ventricular assist devices

International audienceLeft ventricular assist devices (LVADs) require serial assessment of right and left ventricular (RV & LV) volumes and function. Because the RV is not assisted, its function is a critical determinant of the hemodynamic and contributes significantly to postoperative morbidity and mortality. We evaluated the feasibility and the accuracy of tomographic-equilibrium radionuclide ventriculography (t-ERV) for the assessment of patients with LVADs