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P3. The influence of reconstruction parameters on PET image quality
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A. Delmas et al. / Physica Medica 32 (2016) 367–383
2. Redus, Charge trapping in XR-100T-CdTe and -CZT detectors, Application note ANCZT-2 Rev. 3, 2007. 3. Chen L, Wei YX. Monte Carlo simulations of the SNM spectra for CZT and NaI spectrometers. Appl. Radiat. Isot. 2008;66:1146–50. http://dx.doi.org/10.1016/j.ejmp.2016.11.014
P3. The influence of reconstruction parameters on PET image quality A. Ben-Abdennebi, A. Montrot, B. Farman La Timone Hospital-AP-HM, Nuclear Medicine Department, Marseille, France Introduction. The PET image quality is directly related to the reconstruction algorithm. The statistical reconstruction methods can improve the image quality by improving the spatial resolution. This may change the image contrast and the quantitative measurement of SUV (standardized uptake value) in small structures. The aim of this study is to determine the changes in SUV, image contrast, recovery coefficient and spatial resolution within the reconstruction parameters such as iterations and subsets number and also the applied corrections. Material and method. The measurements of SUV (average and maximum), contrast, recovery coefficient and spatial resolution were obtained through a Jaszczak Deluxe phantom image, acquired on a PET-CT GE scanner Discovery 710Ò. The phantom was filled with a 18F-FDG solution of 22 MBq. These parameters were studied based on the corrections applied during the reconstruction, including the Point Spread Function (PSF) and the Time-Of-Flight (TOF) option. Comparisons have also been made in terms of number of iterations and subsets: OSEM (2.4 and 10 iterations, 1.12 and 24 subsets). Results. Reconstruction results for 4 iterations and 24 subsets showed that the average SUV value, with TOF function is reduced by 5.2%, 2.1% and 4.2% compared to non-TOF, PSF and TOF-PSF reconstructions respectively. With PSF, the average SUV value is reduced by 3% and 2% compared to the non-PSF and TOF-PSF reconstructions respectively. However the average SUV value is increased by 2% compared to the reconstruction integrating the TOF function. The contrast measurement is reduced by 80%, 75% and 45% compared to the expected absolute value for the reconstructions with TOF, PSF and TOF-PSF respectively. The recovery coefficient is improved with the correction of TOF and PSF however improvements become less important when the diameter of the sphere is large. The spatial resolution with the full width at half maximum (FWHM) measured on the largest sphere is underestimated by 5.5%, 0.6% and 5.6% for TOF, PSF and TOF-PSF reconstructions respectively. Conclusion. The reconstruction parameters can improve image quality, however any image reconstruction protocol should be validated before clinical routine or research use. http://dx.doi.org/10.1016/j.ejmp.2016.11.015
Posters 2 - Radiology/MRI P4. A study to establish dose index registry for CT-scan examinations S. Amir a, L. Gonzalez Mendez a,b, S. Fayolle a, A. Noel a,c, I. Rousselle a, H. Miloudi a, F. Dufay a a
Pôle de Physique Médicale C2i santé, Maxeville, France UFR Faculté de Sciences et d’Ingénierie (FSI), Université Toulouse III, Toulouse, France b
c Centre de Recherche en Automatique de Nancy (CRAN - UMR 7039), Vandoeuvre-les-Nancy France
Introduction. This article aims to provide a dose index registry for CT scans in adults; they are distinguished between scanners with or without an iterative reconstruction system. CT scans of interest are those concerning to the national DRLs order (24/10/2011) and seven other exams frequently realized in clinical practice (sinuses, middle ear, dentascan, aorta, cervical spine, shoulder arthrogram and pelvimetry). Methods. Data have been collected over the years 2013 to 2015, taking account 167 scanners from different brands and models, of which 115 are equipped with an iterative reconstruction system. For each CT scan, median, 75th and 25th percentiles, as well as their ratio 75th/25th were determined from the distribution of values registered by the CTDI v ol and the DLP. A comparison with regulatory values from the national DRLs order (24/10/2011) and those from the last IRSN balance sheet (2011–2012) has been established. Results. Due to the increasing number of scanners equipped with an iterative reconstruction system, doses for the national DRLs exams have decreased by an average of 24% for the CTDI v ol and 21% for the DLP. Taking account of this technological characteristic seems essential for the establishment of a dose index registry. Conclusion. Waiting for an update of national DRLs order, health professionals are therefore able to situate their practices and to identify protocols to optimize. http://dx.doi.org/10.1016/j.ejmp.2016.11.016
P5. Variation in head and trunk staff exposure to magnetic fields in 1.5T interventional MRI A. Delmas a,b, N. Weber a,b, P.A. Vuissozy a,b, E. Bretonz c, A. Gangi c,d, J. Felblinger a,b,e, C. Pasquier a,b a
Imagerie Adaptative Diagnostique et Interventionnelle, Nancy, France U947 Inserm, Nancy, France c ICube UMR 7357, Illkirch, France d Interventional Radiology, NHC, Strasbourg, France e CIC-IT Nancy, Vandoeuvre-les-Nancy, France b
Purpose. Percutaneous procedures, such as thermal ablations or biopsies, are increasingly performed under real-time MRI-guidance. During the interventional MRI procedure, physicians are continuously exposed to electromagnetic fields (EMF) generated by the MRI scanner, during the active MRI-guided insertion as well as during ”passive” times such as higher resolution 3D acquisitions or therapy. The European union has suggested electromagnetic field (EMF) threshold values to not be overtaken. These values require EMF assessment methods, thus, in a previous study, EMF exposition variation between head and trunk have been observed in a 3T clinical MRI. We now want to focus on these variations for interventional MRI staff. Material and method. An in house developed MR exposimeter has been designed allowing 3D monitoring of magnetic field, and storage of the information at a 60 Hz sampling rate for a complete working day. Two MR exposimeters were placed simultaneously on the headband of ear defender and the ‘‘thoracic pocket” of two interventional MR radiologists at 1.5T. Physicians were monitored during two tumor cryo-ablations that lasted about 3 h each. Magnetic field normalized vector is used to compare MR exposure. Exposure curves and comparative measurements were performed: mean, peak and cumulative (time integration) assessment of magnetic field (B) and time derivative magnetic field (dB/dt). Results. Comparison of head and trunk exposures are shown in Table 1. Higher peak exposure is seen for the head (red curves) than for the trunk during active needle insertion, while during wait times
A. Delmas et al. / Physica Medica 32 (2016) 367–383
2. Redus, Charge trapping in XR-100T-CdTe and -CZT detectors, Application note ANCZT-2 Rev. 3, 2007. 3. Chen L, Wei YX. Monte Carlo simulations of the SNM spectra for CZT and NaI spectrometers. Appl. Radiat. Isot. 2008;66:1146–50. http://dx.doi.org/10.1016/j.ejmp.2016.11.014
P3. The influence of reconstruction parameters on PET image quality A. Ben-Abdennebi, A. Montrot, B. Farman La Timone Hospital-AP-HM, Nuclear Medicine Department, Marseille, France Introduction. The PET image quality is directly related to the reconstruction algorithm. The statistical reconstruction methods can improve the image quality by improving the spatial resolution. This may change the image contrast and the quantitative measurement of SUV (standardized uptake value) in small structures. The aim of this study is to determine the changes in SUV, image contrast, recovery coefficient and spatial resolution within the reconstruction parameters such as iterations and subsets number and also the applied corrections. Material and method. The measurements of SUV (average and maximum), contrast, recovery coefficient and spatial resolution were obtained through a Jaszczak Deluxe phantom image, acquired on a PET-CT GE scanner Discovery 710Ò. The phantom was filled with a 18F-FDG solution of 22 MBq. These parameters were studied based on the corrections applied during the reconstruction, including the Point Spread Function (PSF) and the Time-Of-Flight (TOF) option. Comparisons have also been made in terms of number of iterations and subsets: OSEM (2.4 and 10 iterations, 1.12 and 24 subsets). Results. Reconstruction results for 4 iterations and 24 subsets showed that the average SUV value, with TOF function is reduced by 5.2%, 2.1% and 4.2% compared to non-TOF, PSF and TOF-PSF reconstructions respectively. With PSF, the average SUV value is reduced by 3% and 2% compared to the non-PSF and TOF-PSF reconstructions respectively. However the average SUV value is increased by 2% compared to the reconstruction integrating the TOF function. The contrast measurement is reduced by 80%, 75% and 45% compared to the expected absolute value for the reconstructions with TOF, PSF and TOF-PSF respectively. The recovery coefficient is improved with the correction of TOF and PSF however improvements become less important when the diameter of the sphere is large. The spatial resolution with the full width at half maximum (FWHM) measured on the largest sphere is underestimated by 5.5%, 0.6% and 5.6% for TOF, PSF and TOF-PSF reconstructions respectively. Conclusion. The reconstruction parameters can improve image quality, however any image reconstruction protocol should be validated before clinical routine or research use. http://dx.doi.org/10.1016/j.ejmp.2016.11.015
Posters 2 - Radiology/MRI P4. A study to establish dose index registry for CT-scan examinations S. Amir a, L. Gonzalez Mendez a,b, S. Fayolle a, A. Noel a,c, I. Rousselle a, H. Miloudi a, F. Dufay a a
Pôle de Physique Médicale C2i santé, Maxeville, France UFR Faculté de Sciences et d’Ingénierie (FSI), Université Toulouse III, Toulouse, France b
c Centre de Recherche en Automatique de Nancy (CRAN - UMR 7039), Vandoeuvre-les-Nancy France
Introduction. This article aims to provide a dose index registry for CT scans in adults; they are distinguished between scanners with or without an iterative reconstruction system. CT scans of interest are those concerning to the national DRLs order (24/10/2011) and seven other exams frequently realized in clinical practice (sinuses, middle ear, dentascan, aorta, cervical spine, shoulder arthrogram and pelvimetry). Methods. Data have been collected over the years 2013 to 2015, taking account 167 scanners from different brands and models, of which 115 are equipped with an iterative reconstruction system. For each CT scan, median, 75th and 25th percentiles, as well as their ratio 75th/25th were determined from the distribution of values registered by the CTDI v ol and the DLP. A comparison with regulatory values from the national DRLs order (24/10/2011) and those from the last IRSN balance sheet (2011–2012) has been established. Results. Due to the increasing number of scanners equipped with an iterative reconstruction system, doses for the national DRLs exams have decreased by an average of 24% for the CTDI v ol and 21% for the DLP. Taking account of this technological characteristic seems essential for the establishment of a dose index registry. Conclusion. Waiting for an update of national DRLs order, health professionals are therefore able to situate their practices and to identify protocols to optimize. http://dx.doi.org/10.1016/j.ejmp.2016.11.016
P5. Variation in head and trunk staff exposure to magnetic fields in 1.5T interventional MRI A. Delmas a,b, N. Weber a,b, P.A. Vuissozy a,b, E. Bretonz c, A. Gangi c,d, J. Felblinger a,b,e, C. Pasquier a,b a
Imagerie Adaptative Diagnostique et Interventionnelle, Nancy, France U947 Inserm, Nancy, France c ICube UMR 7357, Illkirch, France d Interventional Radiology, NHC, Strasbourg, France e CIC-IT Nancy, Vandoeuvre-les-Nancy, France b
Purpose. Percutaneous procedures, such as thermal ablations or biopsies, are increasingly performed under real-time MRI-guidance. During the interventional MRI procedure, physicians are continuously exposed to electromagnetic fields (EMF) generated by the MRI scanner, during the active MRI-guided insertion as well as during ”passive” times such as higher resolution 3D acquisitions or therapy. The European union has suggested electromagnetic field (EMF) threshold values to not be overtaken. These values require EMF assessment methods, thus, in a previous study, EMF exposition variation between head and trunk have been observed in a 3T clinical MRI. We now want to focus on these variations for interventional MRI staff. Material and method. An in house developed MR exposimeter has been designed allowing 3D monitoring of magnetic field, and storage of the information at a 60 Hz sampling rate for a complete working day. Two MR exposimeters were placed simultaneously on the headband of ear defender and the ‘‘thoracic pocket” of two interventional MR radiologists at 1.5T. Physicians were monitored during two tumor cryo-ablations that lasted about 3 h each. Magnetic field normalized vector is used to compare MR exposure. Exposure curves and comparative measurements were performed: mean, peak and cumulative (time integration) assessment of magnetic field (B) and time derivative magnetic field (dB/dt). Results. Comparison of head and trunk exposures are shown in Table 1. Higher peak exposure is seen for the head (red curves) than for the trunk during active needle insertion, while during wait times