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

International audienc

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

Quantification of myocardial 99mTc-labeled bisphosphonate uptake with cadmium zinc telluride camera in patients with transthyretin-related cardiac amyloidosis

Abstract Purpose We aimed to compare different methods for semi-quantitative analysis of cardiac retention of bone tracers in patients with cardiac transthyretin amyloidosis (ATTR). Methods Data from 67 patients with ATTR who underwent both conventional whole-body scan and a CZT myocardial SPECT (DSPECT, Spectrum Dynamics) 3 h after injection of 99mTc-labeled bone tracer were analyzed. Visual scoring of cardiac retention was performed on whole-body scan according to Perugini 4-point grading system from 0 (no uptake) to 3 (strong cardiac uptake with mild/absent bone uptake). A planar heart-to-background (H:B) ratio was calculated using whole-body scan (wb-H:B). CZT SPECT was quantified using three methods: planar H:B ratio calculated from anterior reprojection (ant-H:B), left anterior oblique reprojection (LAO-H:B), and 3D-H:B ratio calculated from transaxial slices as mean counts in a VOI encompassing the heart divided by background VOI in the contralateral lung. Interventricular septal thickness was obtained using echocardiography. Results H:Bs obtained from planar and reprojected data were not statistically different (wb-H:B, 2.05 ± 0.64, ant-H:B, 1.97 ± 0.61, LAO-H:B, 2.06 ± 0.64, all p = ns). However, 3D-H:B was increased compared to planar H:Bs (3D-H:B, 4.06 ± 1.77, all p &lt; 0.0001 vs. wb-H:B, ant-H:B, and LAO-H:B). Bland-Altman plots demonstrated that the difference between 3D and planar H:Bs increased with the mean value of myocardial uptake. 3D-H:B was best correlated to septal thickness (r = 0.45, p &lt; 0.001). Finally, abnormal right ventricular uptake was associated with higher values of cardiac retention. Conclusion 3D semi-quantitative analysis of CZT SPECT optimized the assessment of 99mTc-labeled bone tracer myocardial uptake in patients with cardiac amyloidosis. </jats:sec

Quantification of myocardial 99mTc-labeled bisphosphonate uptake with cadmium zinc telluride camera in patients with transthyretin-related cardiac amyloidosis

International audienceAbstract Purpose We aimed to compare different methods for semi-quantitative analysis of cardiac retention of bone tracers in patients with cardiac transthyretin amyloidosis (ATTR). Methods Data from 67 patients with ATTR who underwent both conventional whole-body scan and a CZT myocardial SPECT (DSPECT, Spectrum Dynamics) 3 h after injection of 99m Tc-labeled bone tracer were analyzed. Visual scoring of cardiac retention was performed on whole-body scan according to Perugini 4-point grading system from 0 (no uptake) to 3 (strong cardiac uptake with mild/absent bone uptake). A planar heart-to-background (H:B) ratio was calculated using whole-body scan (wb-H:B). CZT SPECT was quantified using three methods: planar H:B ratio calculated from anterior reprojection (ant-H:B), left anterior oblique reprojection (LAO-H:B), and 3D-H:B ratio calculated from transaxial slices as mean counts in a VOI encompassing the heart divided by background VOI in the contralateral lung. Interventricular septal thickness was obtained using echocardiography. Results H:Bs obtained from planar and reprojected data were not statistically different (wb-H:B, 2.05 ± 0.64, ant-H:B, 1.97 ± 0.61, LAO-H:B, 2.06 ± 0.64, all p = ns). However, 3D-H:B was increased compared to planar H:Bs (3D-H:B, 4.06 ± 1.77, all p &lt; 0.0001 vs. wb-H:B, ant-H:B, and LAO-H:B). Bland-Altman plots demonstrated that the difference between 3D and planar H:Bs increased with the mean value of myocardial uptake. 3D-H:B was best correlated to septal thickness ( r = 0.45, p &lt; 0.001). Finally, abnormal right ventricular uptake was associated with higher values of cardiac retention. Conclusion 3D semi-quantitative analysis of CZT SPECT optimized the assessment of 99m Tc-labeled bone tracer myocardial uptake in patients with cardiac amyloidosis

Cerebral perfusion measured by 99mTc-HMPAO SPECT in a simulated microgravity model using a 5-day dry immersion

International audienceAim/Introduction: Regional cerebral perfusion (rCBF) may be modified during exposure to microgravity. Microgravity induces a rapid thoraco-cephalic fluid shift and generates a possible increase of intra-cranial pressure [1]. Dry immersion (DI) is a simulated microgravity model that reproduces the effects of microgravity on human fluids [2]. However, consequences on rCBF have never been directly assessed in real or simulated microgravity.Materials and Methods: Cerebral perfusion was measured 4 days before and at the end of a 5-day DI in 18 healthy male subjects (34.0 +/- 5.5 years old, 16 right dominant hand) using a single photon emission computed tomography (SPECT) with the radiopharmaceutical 99mTc-hexamethylpropylene amine oxime (HMPAO). SPECT-HMPAO were compared between the two groups using SPM 12, by paired t test statistical analysis with a threshold of p < 0.005. Results: DI induced a significant hypoperfusion in the cortex, mainly in the two temporal regions (right temporal peak level : Z = 3,61, p uncorr <0,001;left temporal peak level : Z = 3,40, puncorr <0,001))and induced an increase in perfusion in subcortical regions (including left thalamus (peak level: Z = 3,07, p uncorr <0,001)). Conclusion: After 5 days of DI, subjects presented significant hypoperfusion mainly in the bilateral temporal regions and hyperperfusion in the left thalamus region, measured by SPECT-HMPAO. Hyperperfusion in the left thalamus may be related to a muscular biopsy in the right vastus lateralis performedthe day before the SPECTthe end of DI. Hypoperfusion in the cortical regions might be due to the thoraco-cephalic fluid shift and/or to the unloading support induced by the DI model. To test these assumptions, we need to conduct analysis of other parameters such as indirect assessment of intracranial pressure and psychological tests.References: [1] Heer M, et al. Space motion sickness: incidence, etiology, and countermeasures. Auton Neurosci 2006; 129(1-2):77-9.[2] Navasiolava et al. 2011). Long-term dry immersion: review and prospects. Eur J Appl Physiol 2011;111(7):1235-60

Cerebral perfusion measured by 99mTc-HMPAO SPECT in a simulated microgravity model using a 5-day dry immersion

International audienceAim/Introduction: Regional cerebral perfusion (rCBF) may be modified during exposure to microgravity. Microgravity induces a rapid thoraco-cephalic fluid shift and generates a possible increase of intra-cranial pressure [1]. Dry immersion (DI) is a simulated microgravity model that reproduces the effects of microgravity on human fluids [2]. However, consequences on rCBF have never been directly assessed in real or simulated microgravity.Materials and Methods: Cerebral perfusion was measured 4 days before and at the end of a 5-day DI in 18 healthy male subjects (34.0 +/- 5.5 years old, 16 right dominant hand) using a single photon emission computed tomography (SPECT) with the radiopharmaceutical 99mTc-hexamethylpropylene amine oxime (HMPAO). SPECT-HMPAO were compared between the two groups using SPM 12, by paired t test statistical analysis with a threshold of p < 0.005. Results: DI induced a significant hypoperfusion in the cortex, mainly in the two temporal regions (right temporal peak level : Z = 3,61, p uncorr <0,001;left temporal peak level : Z = 3,40, puncorr <0,001))and induced an increase in perfusion in subcortical regions (including left thalamus (peak level: Z = 3,07, p uncorr <0,001)). Conclusion: After 5 days of DI, subjects presented significant hypoperfusion mainly in the bilateral temporal regions and hyperperfusion in the left thalamus region, measured by SPECT-HMPAO. Hyperperfusion in the left thalamus may be related to a muscular biopsy in the right vastus lateralis performedthe day before the SPECTthe end of DI. Hypoperfusion in the cortical regions might be due to the thoraco-cephalic fluid shift and/or to the unloading support induced by the DI model. To test these assumptions, we need to conduct analysis of other parameters such as indirect assessment of intracranial pressure and psychological tests.References: [1] Heer M, et al. Space motion sickness: incidence, etiology, and countermeasures. Auton Neurosci 2006; 129(1-2):77-9.[2] Navasiolava et al. 2011). Long-term dry immersion: review and prospects. Eur J Appl Physiol 2011;111(7):1235-60

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

Cerebral perfusion measured by 99mTc-HMPAO SPECT in a simulated microgravity model using a 5-day dry immersion

International audienceAim/Introduction: Regional cerebral perfusion (rCBF) may be modified during exposure to microgravity. Microgravity induces a rapid thoraco-cephalic fluid shift and generates a possible increase of intra-cranial pressure [1]. Dry immersion (DI) is a simulated microgravity model that reproduces the effects of microgravity on human fluids [2]. However, consequences on rCBF have never been directly assessed in real or simulated microgravity.Materials and Methods: Cerebral perfusion was measured 4 days before and at the end of a 5-day DI in 18 healthy male subjects (34.0 +/- 5.5 years old, 16 right dominant hand) using a single photon emission computed tomography (SPECT) with the radiopharmaceutical 99mTc-hexamethylpropylene amine oxime (HMPAO). SPECT-HMPAO were compared between the two groups using SPM 12, by paired t test statistical analysis with a threshold of p < 0.005. Results: DI induced a significant hypoperfusion in the cortex, mainly in the two temporal regions (right temporal peak level : Z = 3,61, p uncorr <0,001;left temporal peak level : Z = 3,40, puncorr <0,001))and induced an increase in perfusion in subcortical regions (including left thalamus (peak level: Z = 3,07, p uncorr <0,001)). Conclusion: After 5 days of DI, subjects presented significant hypoperfusion mainly in the bilateral temporal regions and hyperperfusion in the left thalamus region, measured by SPECT-HMPAO. Hyperperfusion in the left thalamus may be related to a muscular biopsy in the right vastus lateralis performedthe day before the SPECTthe end of DI. Hypoperfusion in the cortical regions might be due to the thoraco-cephalic fluid shift and/or to the unloading support induced by the DI model. To test these assumptions, we need to conduct analysis of other parameters such as indirect assessment of intracranial pressure and psychological tests.References: [1] Heer M, et al. Space motion sickness: incidence, etiology, and countermeasures. Auton Neurosci 2006; 129(1-2):77-9.[2] Navasiolava et al. 2011). Long-term dry immersion: review and prospects. Eur J Appl Physiol 2011;111(7):1235-60

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