Applications of phase-contrast velocimetry sequences in cardiovascular imaging.

AIMS: To describe and illustrate the main applications of phase-contrast flow quantification in cardiovascular imaging. CONCLUSION: Phase-contrast velocimetry sequences provide an accurate, reliable, reproducible and non-invasive study of blood flow, information which is sometimes not available from other investigation methods. The haemodynamic information obtained from these complement MRI angiography images. They appear to have a range of clinical applications, firstly improving pathophysiological understanding but also contributing to the treatment and follow-up strategy after surgical or endovascular treatment

Optimization of radiation dose for CT detection of lytic and sclerotic bone lesions: a phantom study.

To determine the best compromise between low radiation dose and suitable image quality for the detection of lytic and sclerotic bone lesions of the lumbar spine and pelvis. A phantom was scanned using the routine protocol (STD, 13 mGy) and six decreasing dose levels. Raw data were reconstructed using level 3 of iterative reconstruction (IR3) with 1-mm slice thickness for the STD protocol and highest IR levels with 3-mm slice thickness for the others. CTDI <sub>vol</sub> was used for radiation dose assessment. Quantitative criteria (noise power spectrum [NPS], task-based transfer function [TTF], and the detectability index [d']), as well as qualitative analysis, were used to compare protocols. NPS and TTF were computed using specific software (imQuest). d' was computed for two imaging tasks: lytic and sclerotic bone lesions. A subjective analysis was performed to validate the image quality obtained on the anthropomorphic phantom with the different dose values. Similar d' values were found for CTDI <sub>vol</sub> from 3 to 4 mGy with IR4 and from 1 to 2 mGy for IR5 compared with d' values using the STD protocol. Image quality was validated subjectively for IR4 but rejected for IR5 (image smoothing). Finally, for the same d', the dose was reduced by 74% compared with the STD protocol, with the CTDI <sub>vol</sub> being 3.4 mGy for the lumbar spine and for the pelvis. A dose level as low as 3.4 mGy, in association with high levels of IR, provides suitable image quality for the detection of lytic and sclerotic bone lesions of the lumbar spine and pelvis. • A CTDI <sub>vol</sub> of 3.4 mGy, in association with high iterative reconstruction level, provides suitable image quality for the detection of lytic and sclerotic bone lesions, both at objective and subjective analysis. • Compared with the standard protocol, radiation dose can be reduced up to 74% for the lumbar spine and pelvis. • A task-based image quality assessment using the detectability index represents an objective method for the assessment of image quality and bridges the gap between complex physical metrics and subjective image analysis

Étude de poste et zonage aux blocs opératoires : application pratique d’une méthodologie en 6 étapes

La réalisation pratique des études de poste et du zonage aux blocs opératoires est complexe du fait de l’environnement, des contraintes et de l’activité de ce secteur. L’objectif de notre étude est d’illustrer au sein du CHU de Nîmes l’application de la méthode définie dans Duverger et al. (2015) [Étude de poste et zonage aux blocs opératoires : méthodologie pratique en six étapes, Radioprotection 50 (4), 287-293] en présentant les résultats obtenus pour 3 spécialités chirurgicales (orthopédie, urologie et vasculaire). À partir de la base de données dosimétrique mise en place, une large proportion (>85 %) de l’activité avec rayonnements ionisants de chaque spécialité est regroupée en 3 (urologie) ou 5 (orthopédie et vasculaire) types d’intervention. Ces types d’intervention font l’objet de simulations permettant d’évaluer l’exposition à chaque poste de travail. Le zonage de chaque salle est obtenu à partir d’une proportion de chaque type d’intervention dans la salle la plus pénalisante de chaque spécialité. L’activité regroupée est ensuite extrapolée à l’activité totale pour obtenir les études de poste et le zonage de chaque spécialité. Les résultats obtenus permettent de proposer un classement en catégorie B de l’ensemble des agents. La zone contrôlée verte calculée est étendue aux parois de la salle et les zones attenantes sont classées en zone non réglementée. L’application de cette méthode basée sur 6 étapes permet de pallier les difficultés rencontrées dans ce secteur

PICC management led by technicians: Establishment of a cooperation program with radiologists and evaluation of complications

International audienceThe purpose of this study was to evaluate a cooperation program in order to compare incidence of complications after peripherally inserted central catheter (PICC) placement between radiologists and technicians.Materials and methods: PICC placement technique was standardized with ultrasound-guided puncture and fluoroscopic guidance. Numbers of PICC delegated to technicians, and PICC placement difficulties, were prospectively recorded for the whole study population whereas complications such as PICC infection, deep venous thrombosis and catheter occlusion were prospectively recorded until PICC removal for a subgroup of patients included during one month.Results: A total of 722 patients had PICC placement. There were 382 men and 340 women with a mean age of 66.8±15.8 (SD) years (range: 18-94years); of these, 442/722 patients (61.22%) were included in the cooperation program with 433/722 patients (59.97%) who effectively had PICC placement by technicians and 289/722 (40.03%) by radiologists. Technicians needed radiologists' help for 23/442 patients (5.20%) including 6 failed PICC placement subsequently performed by radiologists. Twenty complications (20/77; 26%) were recorded in the subgroup of 77 patients studied for complications. No differences in complications rate were found between the 33 patients who underwent PICC placement by radiologists (6/33; 18%) and the 44 patients who underwent PICC placement by technicians (14/44; 32%) (P=0.296). Complications included 8 PICC-related infections (8/77; 10.4%), 3 deep venous thromboses (3/77; 3.9%) and 9 catheter occlusions (9/77; 11.7%).Conclusion: PICC placement led by technicians is feasible and safe without statistical difference in terms of complications compared to PICC placement made by radiologists

Brain image quality according to beam collimation width and image reconstruction algorithm: A phantom study.

To compare quantitatively and qualitatively brain image quality acquired in helical and axial modes on two wide collimation CT systems according to the dose level and algorithm used. Acquisitions were performed on an image quality and an anthropomorphic phantoms at three dose levels (CTDI <sub>vol</sub> : 45/35/25 mGy) on two wide collimation CT systems (GE Healthcare and Canon Medical Systems) in axial and helical modes. Raw data were reconstructed using iterative reconstruction (IR) and deep-learning image reconstruction (DLR) algorithms. The noise power spectrum (NPS) was computed on both phantoms and the task-based transfer function (TTF) on the image quality phantom. The subjective quality of images from an anthropomorphic brain phantom was evaluated by two radiologists including overall image quality. For the GE system, noise magnitude and noise texture (average NPS spatial frequency) were lower with DLR than with IR. For the Canon system, noise magnitude values were lower with DLR than with IR for similar noise texture but the opposite was true for spatial resolution. For both CT systems, noise magnitude was lower with the axial mode than with the helical mode for similar noise texture and spatial resolution. Radiologists rated the overall quality of all brain images as "satisfactory for clinical use", whatever the dose level, algorithm or acquisition mode. Using 16-cm axial acquisition reduces image noise without changing the spatial resolution and image texture compared to helical acquisitions. Axial acquisition can be used in clinical routine for brain CT examinations with an explored length of less than 16 cm

Dose reduction with iterative reconstruction: Optimization of CT protocols in clinical practice

AbstractObjectivesTo create an adaptable and global approach for optimizing MDCT protocols by evaluating the influence of acquisition parameters and Iterative Reconstruction (IR) on dose reduction and image quality.Materials and methodsMDCT acquisitions were performed on quality image phantom by varying kVp, mAs, and pitch for the same collimation. The raw data were reconstructed by FBP and Sinogram Affirmed Iterative Reconstruction (SAFIRE) with different reconstruction kernel and thickness. A total of 4032 combinations of parameters were obtained. Indices of quality image (image noise, NCT, CNR, SNR, NPS and MTF) were analyzed. We developed a software in order to facilitate the optimization between dose reduction and image quality. Its outcomes were verified on an adult anthropomorphic phantom.ResultsDose reduction resulted in the increase of image noise and the decrease of SNR and CNR. The use of IR improved these indices for the same dose without affecting NCT and MTF. The image validation was performed by the anthropomorphic phantom. The software proposed combinations of parameters to reduce doses while keeping indices of the image quality adequate. We observed a CTDIvol reduction between −44% and −83% as compared to the French diagnostic reference levels (DRL) for different anatomical localization.ConclusionThe software developed in this study may help radiologists in selecting adequate combinations of parameters that allows to obtain an appropriate image with dose reduction