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The national diagnostic reference level service (NDRLS), was launched in 2011, however no paediatric data were submitted during the first calendar year of operation. As such, Australian national diagnostic reference levels (DRLs), for paediatric multi detector computed tomography (MDCT), were established using data obtained from a Royal Australian and New Zealand College of Radiologists (RANZCR), Quality Use of Diagnostic Imaging (QUDI), study. Paediatric data were submitted to the NDRLS in 2012 through 2015. An analysis has been made of the NDRLS paediatric data using the same method as was used to analyse the QUDI data to establish the Australian national paediatric DRLs for MDCT. An analysis of the paediatric NDRLS data has also been made using the method used to calculate the Australian national adult DRLs for MDCT. A comparison between the QUDI data and subsequent NDRLS data shows the NDRLS data to be lower on average for the Head and AbdoPelvis protocol and similar for the chest protocol. Using an average of NDRLS data submitted between 2012 and 2015 implications for updated paediatric DRLS are considered.

Australian National Diagnostic Reference Levels for paediatric multi detector computed tomography were established for three protocols, Head, Chest and AbdoPelvis, across two age groups, Baby/Infant 0-4 years and Child 5-14 years by the Australian Radiation Protection and Nuclear Safety Agency in 2012. The establishment of Australian paediatric DRLs is an important step towards lowering patient CT doses on a national scale. While Adult DRLs were calculated with data collected from the web based Australian National Diagnostic Reference Level Service, no paediatric data was submitted in the first year of service operation. Data from an independent Royal Australian and New Zealand College of Radiologists Quality Use of Diagnostic Imaging paediatric optimisation survey was used. The paediatric DRLs were defined for CTDIvol (mGy) and DLP (mGy·cm) values that referenced the 16 cm PMMA phantom for the Head protocol and the 32 cm PMMA phantom for body protocols for both paediatric age groups. The Australian paediatric DRLs for multi detector computed tomography are for the Head, Chest and AbdoPelvis protocols respectively, 470, 60 and 170 mGy·cm for the Baby/Infant age group, and 600, 110 and 390 mGy·cm for the Child age group. A comparison with published international paediatric DRLs for computed tomography reveal the Australian paediatric DRLs to be lower on average. However, the comparison is complicated by misalignment of defined age ranges. It is the intention of ARPANSA to review the paediatric DRLs in conjunction with a review of the adult DRLs, which should occur within 5 years of their publication.

To study the feasibility of evaluation of collateral channel (CC) classification in patients with coronary chronic total occlusion (CTO) by coronary computed tomography angiography (CTA) with reference to invasive coronary angiography (ICA) validation. We retrospectively included CTO-confirmed patients who underwent both coronary CTA and ICA within 1 month. Collaterals were classified by coronary CTA into three types: CC0, no continuous connection between donor and recipient vessel; CC1, continuous thread-like connection; CC2, continuous, small sidebranch-like connection. With comparison to ICA results, the diagnostic performance of CTA-based CC classification was further assessed. 118 patients with 132 ICA-confirmed CTO lesions were included. Compared to ICA-based evaluation, good overall diagnostic accuracy of CT-based CC classification was observed (78%, 103/132, κ = 0.674, p < 0.001). Coronary CTA was also revealed to be accurate in terms of assessment of collateral tortuosity (76.2%, 77/101) and identification of principal donor vessel (70.3%, 71/101). Impaired diagnostic performance was observed in sub-group of septal collaterals as the accuracy for evaluation of the above parameters was 60.6% (20/33), 72.7% (24/33) and 45.5% (15/33) respectively. Non-invasive evaluation of CC classification by coronary CTA correlates well with ICA findings. In addition, the septal collaterals are much less visible at coronary CTA than epicardial collaterals.

Computed tomography coronary angiography (CTA) and cardiac magnetic resonance myocardial perfusion imaging (CMR-MPI) are state-of-the-art tools for noninvasive assessment of coronary artery disease (CAD). We aimed to compare the diagnostic accuracy of CTA and CMR-MPI for the detection of functionally relevant CAD, using invasive coronary angiography (XA) with fractional flow reserve (FFR) as a reference standard, and to evaluate the best protocol integrating these techniques for assessment of patients with suspected CAD. 95 patients (68 % men; 62 ± 8.1 years) with intermediate pre-test probability (PTP) of CAD underwent a sequential protocol of CTA, CMR-MPI and XA. Significant CAD was defined as >90 % coronary stenosis, 40-90 % stenosis with FFR ≤ 0.80 or left main stenosis ≥50 %. Prevalence of significant CAD was 43 %. CTA was more sensitive (100 %) but less specific (59 %) than CMR-MPI (88 and 89 %, respectively) for detection of significant CAD, with a strong trend for higher global diagnostic accuracy of CMR-MPI (88 vs. 77 %, p = 0.05). An integrated approach based on an initial CTA and subsequent referral to CMR-MPI of positive/inconclusive results had the best diagnostic performance (AUC 0.91). The direct referral to XA of patients with positive/inconclusive CTA performed worse than a selective approach based on CMR-MPI results (AUC 0.80 vs. 0.91, p = 0.005). In this intermediate PTP population, CMR-MPI showed a strong trend toward better performance compared to CTA for the assessment of functionally significant CAD. A combined protocol integrating coronary anatomy and function seems to be a very effective approach in the accurate diagnosis of CAD.

Coronary computed tomography angiography (CCTA) contrast opacification gradients, or transluminal attenuation gradients (TAG) offer incremental value to predict functionally significant lesions. This study introduces and evaluates an automated gradients software package that can potentially supplant current, labor-intensive manual TAG calculation methods. All 60 major coronary arteries in 20 patients who underwent a clinically indicated single heart beat 320 × 0.5 mm detector row CCTA were retrospectively evaluated by two readers using a previously validated manual measurement approach and two additional readers who used the new automated gradient software. Accuracy of the automated method against the manual measurements, considered the reference standard, was assessed via linear regression and Bland-Altman analyses. Inter- and intra-observer reproducibility and factors that can affect accuracy or reproducibility of both manual and automated TAG measurements, including CAD severity and iterative reconstruction, were also assessed. Analysis time was reduced by 68% when compared to manual TAG measurement. There was excellent correlation between automated TAG and the reference standard manual TAG. Bland-Altman analyses indicated low mean differences (1 HU/cm) and narrower inter- and intra-observer limits of agreement for automated compared to manual measurements (25 and 36% reduction with automated software, respectively). Among patient and technical factors assessed, none affected agreement of manual and automated TAG measurement. Automated 320 × 0.5 mm detector row gradient software reduces computation time by 68% with high accuracy and reproducibility.

Regional ejection fraction (REF) provides important functional information of the left ventricular regional myocardium. We aimed to test the diagnostic accuracy of computerized REF analysis for detecting the ischemia and significant stenosis with multidetector CT angiography (MDCT). This is a retrospective study including 155 patients who underwent MDCT scans for evaluation of coronary artery disease. Among them, 83 patients also underwent SPECT imaging and invasive coronary angiography (ICA). Two groups of patients were defined: Control group with 0 coronary artery calcium and normal global and regional ventricular function, and comparison group. REF measurement was performed on all patients using computerized software. Control group REF measurements will be used as reference standard (mean-2SD REF/mean global ejection fraction) to define abnormal REF. The sensitivity, specificity, positive and negative predictive value of REF in detecting perfusion defects (fixed and reversible) was 73, 80, 75 and 79 % respectively, in a patient based analysis of comparison group. The diagnostic accuracy of REF in predicting significant stenosis (>50 %) on ICA compared with SPECT was 72 versus 61 % and 85 versus 79 % in patient and vessel based analysis of comparison group, respectively. ROC curve analysis showed REF to be a better predictor of perfusion defects on SPECT compared with significant stenosis (>50 %) alone or stenosis combined with REF (P < 0.05). The computerized assessment of REF analysis is comparable to SPECT in predicting ischemia and a better predictor of significant stenosis than SPECT. This study also provides reference standard to define abnormal values.

Clinical palpation of a pulsating abdominal mass alerts the clinician to the presence of a possible abdominal aortic aneurysm (AAA). Generally an arterial aneurysm is defined as a localized arterial dilatation ≥50% greater than the normal diameter. Imaging studies are important in diagnosing the cause of a pulsatile abdominal mass and, if an AAA is found, in determining its size and involvement of abdominal branches. Ultrasound (US) is the initial imaging modality of choice when a pulsatile abdominal mass is present. Noncontrast computed tomography (CT) may be substituted in patients for whom US is not suitable. When aneurysms have reached the size threshold for intervention or are clinically symptomatic, contrast-enhanced multidetector CT angiography (CTA) is the best diagnostic and preintervention planning study, accurately delineating the location, size, and extent of aneurysm and the involvement of branch vessels. Magnetic resonance angiography (MRA) may be substituted if CT cannot be performed. Catheter arteriography has some utility in patients with significant contraindications to both CTA and MRA. The American College of Radiology Appropriateness Criteria(®) are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances where evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

A negative (zero) Agatston coronary calcium score (CCS) by current methods confers a very low risk for hard coronary events during the next years. However, controversy remains on how to use a negative score since some hard events still occur. We report on a new method with improved detection sensitivity for very small calcifications with the potential to more confidently rule out early atherosclerotic disease. Seventy-eight (78) patients with negative Agatston scores by conventional methods with 2.5 mm slices were selected from routine GE 64 MDCT scans. Each scan was reconstructed a second time from the same data to create 0.625 mm isotropic voxels. The 2.5 mm images were manually scored by the usual Agatston method using the GE SmartScore™ software. Both the 2.5 and 0.625 mm image sets were scored with a new automated and calibrated method (N-vivo™, Image Analysis). The software automatically computes dual scoring thresholds that are statistically defined and specific for each patient, scanner, and scan. The images were hybrid calibrated by simultaneous scanned phantoms in combination with in vivo blood/muscle references. The output reported the calibrated mass scores along with the number of plaques using 18 pt, 3-D connectivity criteria. A CCS Test phantom with known CaHA microspheres was used to validate the method. Twenty-three percent (18 of 78) of the patients with negative Agatston scores by the conventional method scored positive for coronary calcifications by the N-vivo method. The number of small plaques scored per patient varied from 1 to 4. One patient with a single small calcification suffered a hard coronary event during the CT scan. All of the detected plaques were located in the proximal heart. The conventional CCS method misclassified 23% of these patients as having negative coronary calcium scores. The N-vivo automated scoring method with small voxel CT images increased the detection sensitivity of small calcifications with no increase in radiation dose. Detection of small coronary calcified plaques occult to conventional scoring methods may increase the negative predictive power of calcium scoring and may improve plaque composition analysis.

To compare the measurement of global left-ventricular (LV) function parameters of 64-slice multidetector-row computed tomography (MDCT) between 20- and 10-reconstruction phases. Fifty five patients with suspected or known coronary artery disease underwent 64-slice MDCT. LV end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), and ejection fraction (EF) were measured from MDCT data sets using threshold-based volume segmentation and reconstruction at every 5% (20 phases) and 10% (10 phases) step through the R-R interval. These global functional parameters were compared to those obtained via two-dimensional transthoracic echocardiography (2D-TTE), considering the reference standard. The required time for CT data analysis was checked. Agreement for parameters of LV global function was determined using Pearson's correlation coefficient (r) and Bland-Altman analysis. LV volumes (EDV(-5%) 87.5 ± 17.1 ml, EDV(-10%) 87.7 ± 16.3 ml; ESV(-5%) 32.4 ± 10.6 ml, ESV(-10%) 31.9 ± 9.9 ml; SV(-5%) 55.1 ± 10.5 ml, SV(-10%) 55.8 ± 9.9 ml; mean ± SD) and EF (EF(-5%) 63.4 ± 6.2%, EF(-10%) 63.9 ± 5.8%) did not differ significantly between the 20- and 10 phase reconstructions, and evidenced good to excellent correlation (r = 0.786-0.896, all P < 0.001) with the 2D-TTE results. The mean required time for CT data analysis in the 20- and 10 phase reconstructions were 15.5 ± 4.0 and 7.3 ± 2.5 min. Within MDCT, using 10-phase image reconstruction is sufficient to evaluate LV volumes and EF, and is also more time-effective than 20-phase reconstruction.