Intra-patient comparison of reduced-dose model-based iterative reconstruction with standard-dose adaptive statistical iterative reconstruction in the CT diagnosis and follow-up of urolithiasis.

OBJECTIVES: To evaluate the accuracy of reduced-dose CT scans reconstructed using a new generation of model-based iterative reconstruction (MBIR) in the imaging of urinary tract stone disease, compared with a standard-dose CT using 30% adaptive statistical iterative reconstruction. METHODS: This single-institution prospective study recruited 125 patients presenting either with acute renal colic or for follow-up of known urinary tract stones. They underwent two immediately consecutive scans, one at standard dose settings and one at the lowest dose (highest noise index) the scanner would allow. The reduced-dose scans were reconstructed using both ASIR 30% and MBIR algorithms and reviewed independently by two radiologists. Objective and subjective image quality measures as well as diagnostic data were obtained. RESULTS: The reduced-dose MBIR scan was 100% concordant with the reference standard for the assessment of ureteric stones. It was extremely accurate at identifying calculi of 3 mm and above. The algorithm allowed a dose reduction of 58% without any loss of scan quality. CONCLUSIONS: A reduced-dose CT scan using MBIR is accurate in acute imaging for renal colic symptoms and for urolithiasis follow-up and allows a significant reduction in dose. KEY POINTS: • MBIR allows reduced CT dose with similar diagnostic accuracy • MBIR outperforms ASIR when used for the reconstruction of reduced-dose scans • MBIR can be used to accurately assess stones 3 mm and above.

Drugless and radiographer led: the start of a new era for CT coronary angiography.

OBJECTIVE: Since inception CT coronary angiography (CTCA) has required facilitating beta blockers (BB). However, CT technology has improved rapidly as has radiographer and reporter expertise. Using these factors, we instituted a radiographer led cardiac CT service (RLCCTS), without routine BB, which we studied for quality control (QC). METHODS: RLCCTS started October 2021 using a wide detector array CT system, with 20 min slots. QC study was registered with the clinical audit team, University Hospitals Plymouth, CA_2020-21-118. Uniform reporting was agreed including indication, BB administration, demographics, dose length product (DLP) and the coronary artery disease-reporting and data system (CAD-RADS) score. Uncertain CAD-RADS meant a non-diagnostic scan (NDS). Six months of data were collected; stable chest pain (SCP) patients, who have national CTCA QC comparators, were analysed using descriptive statistics. RESULTS: Of 1475 patients, 447 were not SCP patients-known CAD (157); valves (286); removed (4, data incomplete) leaving 1028 SCP patients CTCA for analysis. Demographics-mean age 63 years, body mass index 29, 50.4% women. BB therapy-four patients (two recalls). Overall, 36/1024 or 3.5% were NDS; median DLP 173mGy×cm; mean heart rate (HR) 70 bpm, 99/1024 or 9.7% HR >90 bpm (45% not sinus rhythm). CONCLUSIONS: Quality for RLCCTS was judged by NDS rate and DLP. National QC comparators suggest 4% NDS rate; median DLP for SCPP CTCA 209 mGy×cm. RLCCTS compares favourably. With modern cardiac CT, experienced radiographers and reporters, 'drugless' RLCCTS can deliver 20 min slot CTCA with satisfactory QC indicators.