Improving practice in radiology: a quality-improvement project examining CT colonography patient dose and scanning technique

AIM

To audit scanning technique and patient doses for computed tomography (CT) colonography (CTC) examinations in a large UK region and to identify opportunities for quality improvement.

MATERIALS AND METHODS

Scanning technique and patient dose data were gathered for both contrast-enhanced and unenhanced CTC examinations from 33 imaging protocols across 27 scanners. Measurements of patient weight and effective diameter were also obtained. Imaging protocols were compared to identify technique differences between similar scanners. Scanner average doses were calculated and combined to generate regional diagnostic reference limits (DRLs) for both examinations.

RESULTS

The regional DRLs for contrast-enhanced examinations were volume CT dose index (CTDIvol) of 11 and 5 mGy for the two scan phases (contrast-enhanced and either delayed phase or non-contrast enhanced respectively), and dose-length product (DLP) of 740 mGy·cm. For unenhanced examinations, these were 5 mGy and 450 mGy·cm. These are notably lower than the national DRLs of 11 mGy and 950 mGy·cm. Substantial differences in scan technique and doses on similar scanners were identified as areas for quality-improvement action.

CONCLUSION

A regional CTC dose audit has demonstrated compliance with national DRLs but marked variation in practice between sites for the dose delivered to patients, notably when scanners of the same type were compared for the same indication. This study demonstrates that the national DRL is too high for current scanner technology and should be revised.

Pictorial review: Trigeminal nerve: anatomy and pathology

MRI is the imaging modality of choice when trigeminal nerve pathology is suspected. Most lesions are readily recognizable if appropriate imaging sequences are performed. Routine cranial MRI sequences augmented by a three-dimensional gradient echo sequence such as FISP (fast inflow with steady-state precession) are sufficient to demonstrate most pathological processes involving the trigeminal nerve and nucleus. Intravenous gadolinium-DTPA occasionally provides additional diagnostic information. MRI is particularly useful in planning the management of those conditions where surgical or medical intervention can result in improvement or resolution of symptoms. In this review, examples of a range of pathologies involving the trigeminal nerve and nucleus are presented.