CT chest abdomen pelvis doses in Scotland: has the DRL had its day?

ESTIMATION OF RADIATION RISK AND ESTABLISHMENT OF DIAGNOSTIC REFERENCE LEVELS FOR PATIENTS UNDERGOING COMPUTED TOMOGRAPHY CHEST-ABDOMEN-PELVIC EXAMINATIONS IN SUDAN

Establishment of diagnostic reference levels (DRLs) is an essential radiation optimization tool used to indicate optimum practice and radiation protection. This study aimed to report the current computed tomography (CT) of the chest-abdomen-pelvis radiation practice in Sudan as a part of the DRL establishment effort and dose optimization. CT radiation doses were collected from 530 patients of age ranging between 28 and 85 y and body weight ranging between 65 and 120 kg. DRLs were calculated based on the 75th percentile of dose length product (DLP) and CT dose index volume (CTDIvol). Effective and organ doses were calculated using the National Cancer Institute dosimetry system for the CT programme. The proposed DRLs are CTDIvol, 6 mGy, and DLP, 970 mGy.cm, and an effective dose of 9.9 mSv. Organ dose estimation showed that the thyroid received the highest dose during the scan.

Automatic calculation of patient size metrics in computed tomography: What level of computational accuracy do we need?

Objectives

To compare the effectiveness of two different patient size metrics based on water equivalent diameter (D_w), the mid‐scan water equivalent diameter D_{w_c}, and the mean (average) water equivalent diameter in the imaged region, D_{w_ave}, for automatic detection of accidental changes in computed tomography (CT) acquisition protocols.

Methods

Patient biometric data (height and weight) were available from a previous survey for 80 adult chest examinations, and 119 adult single‐acquisition chest–abdomen–pelvis (CAP) examinations for two 16 slice scanners (GE LightSpeed and Toshiba Aquilion RXL) equipped with automatic tube current modulation (ATCM). D_{w_c} and D_{w_ave} were calculated from the archived CT images. Size‐specific dose estimates (SSDE) were obtained from volume CT dose index (CTDI_vol), using the conversion factors for a patient diameter of D_{w_c}.

Results

CTDI_vol and SSDE correlate better with D_{w_ave} than with D_{w_c}. R‐squared values of linear fits to CTDI_vol of CAP examinations were 0.81–0.89 for D_{w_c} and 0.93–0.94 for D_{w_ave} (SSDE: 0.69–080 for D_{w_c}, 0.87–0.92 for D_{w_ave}). Percentage differences between D_{w_c} and D_{w_ave} were −4 ± 4% for chest and +5 ± 4% for CAP examinations (in % of D_{w_ave}). However, small D_w variations translated as larger variations in CTDI_vol for these ATCM systems (e.g., a 24% increase in D_w doubled CTDI_vol). The dependence of CTDI_vol on D_{w_ave} was similar for chest and CAP examinations performed with similar ATCM parameters, while use of D_{w_c} resulted in a clear separation of the same data according to examination type. Maximum D_w variation in the imaged region was 5.6 ± 1.6 cm for chest and 6.5 ± 1.4 cm for CAP examinations.

Conclusions

D_{w_ave} is a better metric than D_{w_c} for binning similar‐sized patients in dose comparison studies, despite the additional computational effort required for its calculation Therefore, when implementing automatic determination of D_w for SSDE calculations, automatic calculation of D_{w_ave} should be considered.

CT dose reduction: approaches, strategies and results from a province-wide program in Quebec

Many studies have shown a statistically significant increase of life-time risk of radiation-induced cancer from CT examinations. In this context, in Canada, the Quebec's provincial clinical center of expertise in radiation safety (CECR) has led a province-wide tour of 180 CT installations in order to: (i) evaluate the technical and functional performance of CT scanners, (ii) evaluate and improve radiation safety practices and (iii) initiate, with local teams, a CT dose optimization process. The CT tour consisted of a two day visit of CT installations by a CECR multidisciplinary team of medical physicists, engineers and medical imaging technologists (MITs) carried out in close collaboration with local teams composed of MITs, radiologists, physicists, engineers and managers. The CECR has evaluated 112 CT scanners since 2011. Optimization of CT protocols was performed in all centers visited. The average dose reduction obtained from optimization was [Formula: see text], [Formula: see text] and [Formula: see text] for adult head, thorax and abdomen-pelvis, respectively. The main recommendations often made by the CECR experts were: (1) the implementation of low-dose protocols for the follow-up of pulmonary nodules and for renal calculi, (2) the compliance to the prescribed scan range as defined by local guidelines, (3) the correct positioning of patients and (4) the use of bismuth shielding to reduce the dose to radiosensitive organs. The CECR approach to optimize CT doses to patients is based on the active participation of local stakeholders and takes into account the performance of CT scanners. The clinical requirements as expressed by radiologists remain at the core of the optimization process.

Radiation dose from multidetector CT studies in children: results from the first Italian nationwide survey

BACKGROUND

Multidetector CT (MDCT) scanners have contributed to the widespread use of CT in paediatric imaging. However, concerns are raised for the associated radiation exposure. Very few surveys on radiation exposure from MDCT studies in children are available.

OBJECTIVE

The aim of this study was to outline the status of radiation exposure in children from MDCT practice in Italy.

MATERIALS AND METHODS

In this retrospective multicentre study we asked Italian radiology units with an MDCT scanner with at least 16 slices to provide dosimetric and acquisition parameters of CT examinations in three age groups (1-5, 6-10, 11-15 years) for studies of head, chest and abdomen. The dosimetric results were reported in terms of third-quartile volumetric CT dose index (CTDIvol) (mGy), size-specific dose estimate (SSDE) (mGy), dose length product (DLP) (mGy cm), and total DLP for multiphase studies. These results were compared with paediatric European and adult Italian published data. A multivariate analysis assessed the association of CTDIvol with patient characteristics and scanning modalities.

RESULTS

We collected data from 993 MDCT examinations performed at 25 centres. For age groups 1-5 years, 6-10 years and 11-15 years, the CTDIvol, DLP and total DLP values were statistically significantly below the values observed in our analogous national survey in adults, although the difference decreased with increasing age. CTDIvol variability among centres was statistically significant (variance = 0.07; 95% confidence interval = 0.03-0.16; P < 0.001).

CONCLUSIONS

This study reviewed practice in Italian centres performing paediatric imaging with MDCT scanners. The variability of doses among centres suggests that the use of standardised CT protocols should be encouraged.