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MR
M. Fontana et al. / Physica Medica 44 (2017) 28–45
36. A DACS (Dose Archiving and Communication System) successful implementation in a private and multisite radiology group V. Plagnol a,b, P.-M. Blayac a,b, L. Chirveches b, I. Joby a, P. Ponsonnaille a a b
SCM Coradix, Perpignan, France GIE Magnescan, Perpignan, France
Introduction. Setting up a Radiation Dose Tracking and Managing program in all our sites is part of a larger Quality Approach intended to homogenize practices. Its main objective is to ensure a radiological follow-up of patients in regards to the dose delivered during CT examinations, not only at the examination level but also in terms of cumulative dose for patients who have several examinations performed at our sites. Methods. We have four CT scanners, two Optima GEMS, one Siemens Somaton and one Philips iCT, located in the Pyrénées-Orien tales (South of France) and geographically distant. The data are centralized in real time on a server. We have chosen the Radimetrics software, from Bayer, since this software perfectly addresses our medical and physical needs. The software implementation took about five weeks. The first step consisted in making an audit of all procedures. Some protocols have been optimized in order to homogenize the dose delivered at all sites. We have also conducted a postural study in order to limit the dose delivered to lenses during head and neck examinations. A set of alerts has been configured on Radimetrics so that we are alerted in case of inappropriate practice. We have also analyzed protocols per physician and per technologist. Results. For one of the sites, which was historically the first to be equipped with an iterative reconstruction solution, we were able, for the Chest-Abdomen-Pelvis and Abdomen-Pelvis examinations to decrease the dose by about 40%. This decrease was achieved by turning the noise index back to the value recommended by the manufacturer. The postural study on the cervical rachis allowed us to significantly decrease the dose delivered to the lenses (minus 70%). The alerts level setup is based on the French Dose Reference Levels (aka NRD Niveaux de Référence Diagnostiques) for the main localizations [1]. They are until now set at the acquisition level and not at the full examination one. One of the outcomes is the technologists’ awareness regarding the importance of the scoutview [2]. Conclusions. The implementation of a DACS in our sites allowed a radiation dose follow-up and the homogenization of the practices. We noted a raising awareness of the radiologists as well as the technologists regarding the positioning and the centering of the patients, the optimization of the lengths of explorations, the choice of the good protocol, the scoutviews importance on the mA modulation. The next step will be to establish alerts on complete examinations and to establish local reference levels for all the localizations.
References 1. AAPM 2011 – Dose Check Guidelines. 2. ECR2015 – Poster C-0891 – J. H. Kim, K. B. Lee. https://doi.org/10.1016/j.ejmp.2017.10.116
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37. Use of a dedicated brain phantom in PET/MR J.-A. Maisonobe a, M. Soret a, M. Khalifé b, C. Jenny a, A. Kas c a Groupe hospitalier Pitié–Salpêtrière – Medical Physics Department, Paris, France b ICM – Brain and Spine Institut, Paris, France c Groupe hospitalier Pitié–Salpêtrière – Nuclear Medicine Department, Paris, France
Introduction. The attenuation correction of PET/MR brain imaging is based on a human atlas. However, this atlas cannot be used for phantoms employed for the usual PET/CT experiments. The method based on the DIXON MRI is used instead to separate water and fat tissues and assign them attenuation coefficients at 511 keV. Nevertheless, the usual PET/CT phantoms generate artefacts on the MRbased attenuation maps. Additionally, their materials have different attenuation coefficients from those of human body. Here, we suggest to substitute the MR derived attenuation correction map with a CT derived attenuation correction map for a brain phantom in PET/MR. Methods. Two PET acquisitions of a 3D Hoffman phantom were achieved: one a PET/CT Biograph mCT Flow (Siemens) and one on a Signa PET/MR (GE). Based on these acquisitions, 4 images were reconstructed: 1 with the PET/CT (PETref) and 3 with the PET/MR (one without attenuation correction (PETNAC), one corrected using MR-based attenuation map (PETMRAC) and one corrected using the CT obtained with the PET/CT, registered on the MRI images (PETCTAC). To evaluate the effect of the different attenuation correction of the PET images, activity concentrations ratio between white matter (WM) and gray matter (GM), as well as between anterior and posterior regions (A/P) and between right and left (R/L) regions, were measured on PETNAC, PETMRACand PETCTAC and compared to the ratios obtained with PETref. Results. The MR based attenuation correction map of the Hoffman phantom showed artefacts due to segmentation and tissue classification errors. Moreover, for all the reconstructed images, no R/L asymmetry was observed (ratios between 0.96 and 0.99). However, a strong A/P asymmetry with a mean value of 20% was measured in the PETNAC for both WM and GM, versus 1% for the 3 attenuationcorrected images. The WM/GM ratio was underestimated on the PETMRAC (1.84) compared to the CT-based attenuation-corrected ones (1.95 and 1.96 for PETCTAC and PETref, respectively). Conclusions. All the attenuation correction methods allowed to correct the A/P asymmetry, which was increased by the presence of MR coil in the PET/MR system. However, MR-based attenuationcorrection map suffered from artefacts and was not adapted to correct the PET image of the Hoffman phantom in PET/MR. The CT-based attenuation correction method used to correct the Hoffman phantom PET/MR image showed ratios comparable to the ones measured on a PET/CT considered as reference. https://doi.org/10.1016/j.ejmp.2017.10.117
38. Comparison between Anger and Compton cameras for medical imaging: A Monte Carlo simulation study M. Fontana a, D. Dauvergne b, J. Krimmer a, J.M. Létang c, J.L. Ley a, V. Maxim c, E. Testa a a
IPNL, Medical Physics, Lyon, France LPSC, Medical Physics, Grenoble, France c CREATIS, Medical Physics, Lyon, France b
36. A DACS (Dose Archiving and Communication System) successful implementation in a private and multisite radiology group V. Plagnol a,b, P.-M. Blayac a,b, L. Chirveches b, I. Joby a, P. Ponsonnaille a a b
SCM Coradix, Perpignan, France GIE Magnescan, Perpignan, France
Introduction. Setting up a Radiation Dose Tracking and Managing program in all our sites is part of a larger Quality Approach intended to homogenize practices. Its main objective is to ensure a radiological follow-up of patients in regards to the dose delivered during CT examinations, not only at the examination level but also in terms of cumulative dose for patients who have several examinations performed at our sites. Methods. We have four CT scanners, two Optima GEMS, one Siemens Somaton and one Philips iCT, located in the Pyrénées-Orien tales (South of France) and geographically distant. The data are centralized in real time on a server. We have chosen the Radimetrics software, from Bayer, since this software perfectly addresses our medical and physical needs. The software implementation took about five weeks. The first step consisted in making an audit of all procedures. Some protocols have been optimized in order to homogenize the dose delivered at all sites. We have also conducted a postural study in order to limit the dose delivered to lenses during head and neck examinations. A set of alerts has been configured on Radimetrics so that we are alerted in case of inappropriate practice. We have also analyzed protocols per physician and per technologist. Results. For one of the sites, which was historically the first to be equipped with an iterative reconstruction solution, we were able, for the Chest-Abdomen-Pelvis and Abdomen-Pelvis examinations to decrease the dose by about 40%. This decrease was achieved by turning the noise index back to the value recommended by the manufacturer. The postural study on the cervical rachis allowed us to significantly decrease the dose delivered to the lenses (minus 70%). The alerts level setup is based on the French Dose Reference Levels (aka NRD Niveaux de Référence Diagnostiques) for the main localizations [1]. They are until now set at the acquisition level and not at the full examination one. One of the outcomes is the technologists’ awareness regarding the importance of the scoutview [2]. Conclusions. The implementation of a DACS in our sites allowed a radiation dose follow-up and the homogenization of the practices. We noted a raising awareness of the radiologists as well as the technologists regarding the positioning and the centering of the patients, the optimization of the lengths of explorations, the choice of the good protocol, the scoutviews importance on the mA modulation. The next step will be to establish alerts on complete examinations and to establish local reference levels for all the localizations.
References 1. AAPM 2011 – Dose Check Guidelines. 2. ECR2015 – Poster C-0891 – J. H. Kim, K. B. Lee. https://doi.org/10.1016/j.ejmp.2017.10.116
43
37. Use of a dedicated brain phantom in PET/MR J.-A. Maisonobe a, M. Soret a, M. Khalifé b, C. Jenny a, A. Kas c a Groupe hospitalier Pitié–Salpêtrière – Medical Physics Department, Paris, France b ICM – Brain and Spine Institut, Paris, France c Groupe hospitalier Pitié–Salpêtrière – Nuclear Medicine Department, Paris, France
Introduction. The attenuation correction of PET/MR brain imaging is based on a human atlas. However, this atlas cannot be used for phantoms employed for the usual PET/CT experiments. The method based on the DIXON MRI is used instead to separate water and fat tissues and assign them attenuation coefficients at 511 keV. Nevertheless, the usual PET/CT phantoms generate artefacts on the MRbased attenuation maps. Additionally, their materials have different attenuation coefficients from those of human body. Here, we suggest to substitute the MR derived attenuation correction map with a CT derived attenuation correction map for a brain phantom in PET/MR. Methods. Two PET acquisitions of a 3D Hoffman phantom were achieved: one a PET/CT Biograph mCT Flow (Siemens) and one on a Signa PET/MR (GE). Based on these acquisitions, 4 images were reconstructed: 1 with the PET/CT (PETref) and 3 with the PET/MR (one without attenuation correction (PETNAC), one corrected using MR-based attenuation map (PETMRAC) and one corrected using the CT obtained with the PET/CT, registered on the MRI images (PETCTAC). To evaluate the effect of the different attenuation correction of the PET images, activity concentrations ratio between white matter (WM) and gray matter (GM), as well as between anterior and posterior regions (A/P) and between right and left (R/L) regions, were measured on PETNAC, PETMRACand PETCTAC and compared to the ratios obtained with PETref. Results. The MR based attenuation correction map of the Hoffman phantom showed artefacts due to segmentation and tissue classification errors. Moreover, for all the reconstructed images, no R/L asymmetry was observed (ratios between 0.96 and 0.99). However, a strong A/P asymmetry with a mean value of 20% was measured in the PETNAC for both WM and GM, versus 1% for the 3 attenuationcorrected images. The WM/GM ratio was underestimated on the PETMRAC (1.84) compared to the CT-based attenuation-corrected ones (1.95 and 1.96 for PETCTAC and PETref, respectively). Conclusions. All the attenuation correction methods allowed to correct the A/P asymmetry, which was increased by the presence of MR coil in the PET/MR system. However, MR-based attenuationcorrection map suffered from artefacts and was not adapted to correct the PET image of the Hoffman phantom in PET/MR. The CT-based attenuation correction method used to correct the Hoffman phantom PET/MR image showed ratios comparable to the ones measured on a PET/CT considered as reference. https://doi.org/10.1016/j.ejmp.2017.10.117
38. Comparison between Anger and Compton cameras for medical imaging: A Monte Carlo simulation study M. Fontana a, D. Dauvergne b, J. Krimmer a, J.M. Létang c, J.L. Ley a, V. Maxim c, E. Testa a a
IPNL, Medical Physics, Lyon, France LPSC, Medical Physics, Grenoble, France c CREATIS, Medical Physics, Lyon, France b