Establishment of diagnostic reference levels in cardiac CT in France: a need for patient dose optimisation

The objective of this study was to propose diagnostic reference levels (DRLs) for coronary computed tomography angiography (CCTA), in the context of a large variability in patient radiation dose, and the lack of European recommendations. Volume Computed Tomography Dose Index (CTDIvol) and dose-length product (DLP) were collected from 460 CCTAs performed over a 3-month period at eight French hospitals. CCTAs (∼50 per centre) were performed using the routine protocols of the centres, and 64- to 320-detector CT scanners. ECG gating was prospective (n = 199) or retrospective (n = 261). The large gap in dose between these two modes required to propose specific DRLs: 26 and 44 mGy for CTDIvol, and 370 and 970 mGy cm for DLP, respectively. This study confirms the large variability in patient doses during CCTA and underlines the need for the optimisation of cardiac acquisition protocols. Availability of national DRLs should be mandatory in this setting.

Local reference levels and organ doses from pediatric cardiac interventional procedures

Interventional cardiology (IC) procedures can be responsible for relatively high radiation doses compared to conventional radiology especially for young patients. The aim of this study was to assess current exposure levels in a French reference centre of pediatric IC. Dosimetric data including dose area product (DAP), fluoroscopy time (FT) and number of cine frame (NF) were analysed taking into account patient weight. Doses to the lungs, esophagus, breast and thyroid were evaluated using anthropomorphic phantoms and thermoluminescent dosimeters. Finally, effective doses (E) were calculated using DAP and conversion factors calculated with PCXMC 2.0 software. 801 IC procedures performed between 2010 and 2011 were analysed. Large variations were observed for DAP, FT and NF values for a given procedure and a given weight group. The assessment of organ doses showed high levels of dose to the lungs and esophagus especially in new-born babies. For diagnostic procedures, E varied from 0.3 to 23 mSv with a mean value of 4.8 mSv and for therapeutic procedures, values ranged from 0.1 to 48.4 mSv with a mean value of 7.3 mSv. The highest values were recorded for angioplasty procedures (mean 13 mSv, range 0.6-48.4 mSv). The increasing use of IC in pediatric population stresses the need of setting up reference levels and keeping doses to children as low as possible.

IRSN methodological guide to conducting workplace studies in compliance with French regulations

Under French regulations governing radiation protection of workers, dosimetric workplace studies are mandatory. However, their practical implementation is not described. IRSN has developed a guide to help stakeholders in the radiological protection of workers conduct such studies. It proposes a general methodology applicable to most cases and 'workplace sheets', which apply this methodology to specific occupational settings. At present, two sheets are available: conventional radiology and interventional radiology.

Évaluation des doses d’irradiation aux organes en scanographie pédiatrique

PURPOSE

To estimate radiation doses from routine pediatric CT scans (body) and to propose dose reduction protocols.

MATERIAL AND METHODS

[corrected] Study performed with a phantom equivalent to the body of 5 year old child with evaluation of doses delivered to breast, gonads, bone marrow (sternum, T12) and thyroid for CT examinations of the chest, abdomen, pelvis and spine. Extrapolation is made to estimate the doses for 1 year old and 10 year old children. Finally, dose reduction protocols are evaluated.

RESULTS

CT of the chest delivers significant doses to breast tissue and bone marrow, CT of the abdomen and pelvis delivers significant doses to the ovaries and CT pf the spine delivers significant doses to thyroid and bone marrow. Optimization can be achieved without degradation of the image quality, by reducing Kv and mAs within reasonable limits. This study may be used in order to evaluate the doses delivered by multi-detector CT units.