RPS 615 - CT in vascular imaging

Purpose:

Guidelines on the safe use of iodinated contrast material recommend intravenous prophylactic hydration to prevent post-contrast adverse (renal) effects. The AMACING trial showed that standard prophylaxis was not (cost-) effective in the bulk of patients targeted by the guidelines and the latter have been updated accordingly. The current study aims to evaluate the consequences for the clinical practice in terms of reductions in complications, hospitalisations, and costs.

Methods and materials:

The Contrast-Induced Nephropathy After Reduction of the Threshold for prophylaxis (CINART) project is a retrospective observational study. All elective procedures with intravascular iodinated contrast administration at Maastricht University Medical Centre (UMC+) in patients aged >18 years, formerly eligible for prophylaxis (eGFR30-44ml/min/1.73m² or eGFR45-59ml/min/1.73m² in combination with diabetes or >1 predefined risk factor) and currently eligible for prophylaxis (eGFR<30ml/min/1.73m²), were included. Data was used to calculate the relative reductions in complications, hospitalisations, and costs associated with standard prophylactic intravenous hydration. CINART is registered with Clinicaltrials.gov: NCT03227835.

Results:

From July 1, 2017-July 1, 2018, 1,992 elective procedures with intravascular iodinated contrast in patients formerly and currently eligible for prophylaxis were identified: 1,808 in patients formerly eligible for prophylaxis and 184 in patients currently eligible for prophylaxis. At Maastricht UMC+, guideline updates led to large relative reductions in the number of complications from prophylaxis, e.g. symptomatic heart failure (-89%), extra hospitalisations (-93%), and costs (-91%).

Conclusion:

Guideline updates have had a demonstrable impact on daily clinical practice, benefiting patients, hospitals, and health care budgets. The local impact on costs, hospitalisations, and complications can be calculated using the interactive calculator.

Limitations:

A single-centre study at Maastricht UMC+. Parameters may vary at other centres.

Ethics committee approval

The Medical Research Ethics Committee Maastricht UMC+ waived the requirement for informed consent.

Funding:

Stichting de Weijerhorst.

Purpose:

CT protocols for TAVI planning have to be adapted when using a dual-layer spectral CT scanner (DLCT) with 4 cm detector width instead of a conventional single-layer CT with 8 cm detector width (SLCT). The purpose of this study was to compare the objective image quality of aortic CT angiograms (CTA) performed for TAVI planning using a split-phase technique with the reconstruction of 40keV virtual monoenergetic images (VMI40) obtained with DLCT versus a single-phase technique with the reconstruction of standard polychromatic images obtained with SLCT.

Methods and materials:

115 CTA from each scanner were retrospectively analysed. For SLCT, spiral CTA with retrospective ECG-gating was performed for heart and vessel assessment at once. For DLCT, spiral CTA without ECG-synchronisation was performed immediately after a retrospectively ECG-gated spiral acquisition covering the heart. For the image quality assessment, SNR and CNR were calculated on the basis of abdominal aortic and lumbar muscle ROI analyses. Sufficient aortic enhancement was considered at attenuation >250HU.

Results:

Contrast material volume was comparable for DLCT and SLCT (82±6ml vs 81±4ml, p=0.191). Aortic enhancement of VMI40 DLCT-CTA was significantly higher than of SLCT-CTA (610±273HU vs 413±127 HU, p<0.001). No significant differences were found for SNR (21±11 vs 21±8, p=0.420) and CNR (24±15 vs 24±10, p=0.524). Sufficient aortic enhancement was achieved in 97% for DLCT-CTA and in 93% for SLCT-CTA. Total dose length products of TAVI planning examinations were 2003±417mGy*cm for DLCT and 2401±754mGy*cm for SLCT (p<0.001).

Conclusion:

Using a split-phase acquisition technique with the reconstruction of VMI40, CTA for TAVI planning can be obtained with similar objective image quality with DLCT compared to an ECG-gated CT acquisition of the whole aorta performed with conventional SLCT.

Limitations:

n/a

Ethics committee approval

This study was approved by our local ethical committee.

Funding:

No funding was received for this work.

Purpose:

Thoracic aorta dilatation is a major risk factor for dissection or rupture. Diameter measurements on cross-sectional imaging are time-consuming and show inter-reader variability.

We evaluated an artificial intelligence (AI)-Rad companion (AI-RC, Siemens Healthineers) which automatically performs guideline-based measurements of the thoracic aorta and compares them to radiologists' measurements.

Methods and materials:

We identified ECG-gated scans of patients (pts) which were suspected or already diagnosed with dilatation. AHA guideline-based diameter measurements were included in the report. In parallel, those cases were processed with AIRC according to current AHA guidelines. Measurements of the aortic sinus (AS) and ascending aorta (AA) were compared.

Cases with a difference of 5 mm or less between AIRC and manual measurements were considered plausible. If the difference was >5 mm, further evaluation was performed.

Results:

367 scans of 346 patients (mean age 64.5 yrs, 261 male (75.4%)) were included in this study.

The mean difference between reported and AIRC measurements were 0.26 mm for AS (95% CI: -0.71-0.40 mm) and 0.03 mm for AA (95% CI: -0.34-0.34 mm), respectively. Correlations coefficients (Pearson) were high for AS (0.702) and very high for AA (0.912).

Of 367 pts measurements, 270 (74%) were within 5 mm. 97 cases showed a difference >5 mm between measurements. 70 of those 97 cases (72%) showed a misidentification of AS, 4 (4%) a sole misidentification of AA, and 19 (20%) were correctly measured by AIRC. In total, 289/367 cases (79%) were correctly measured by AIRC.

Conclusion:

AIRC shows the potential to assist radiologists since it automatically performs measurements of the thoracic aorta. It reliably measures AA but struggles in identifying the AS in some cases.

Limitations:

A single-centre study and retrospective analysis.

Ethics committee approval

Approved by the regional ethics committee. Informed consent was waived.

Funding:

No funding was received for this work.

Purpose:

To investigate the feasibility of radiomics analysis of AAA CE-CT images to predict fast growth 0.3 cm/year.

Methods and materials:

This retrospective cross-sectional study included 84 AAAs (44 fast-growing, 40 stable) with an index CE-CT for morphologic assessment. Growth was calculated from subsequent clinically-indicated imaging (mean follow-up 3.3±2.6 years). A semi-automated algorithm isolated the AAA outer wall and 1,130 quantitative shape, and 1^st-order and texture features were extracted for each segmentation using an open-source package. Recursive feature elimination (RFE) was used to select the maximally-independent features robustly associated with growth. A random forest (RF) classifier then classified AAAs as fast-growing or stable on the basis of the selected features. The performance of the classifier and a model using conventional risk factors (maximum diameter, age, BMI, diabetes, hypertension, and smoking) were evaluated via 5-fold cross-validation. These two were compared by the area under the receiver operating characteristic (ROC) curve (AUC) using DeLong’s test. Finally, using multivariate logistic regression, the RFE-selected radiomics features and clinical factors were examined for independent association with the growth outcome.

Results:

The mean AUC of the radiomics classification model was 0.80±0.09 and was statistically significantly different (P=0.017) from the conventional risk factor model (mean AUC=0.59±0.12). In multivariate regression, 10 radiomics features independently predicted fast growth. The overall model achieved an odds ratio of 63.20 (95% CI: 8.15-490.06, p<0.001).

Conclusion:

Radiomics features of AAAs in CT images appear to have value in detecting fast growth and may assist in rupture risk stratification.

Limitations:

The small sample size and lacked an independent stability test for the selected radiomics features.

Ethics committee approval

IRB approved.

Funding:

No funding was received for this work.

Purpose:

To study the various anatomical variations in the branching patterns and origins of the arterial supply to the liver and portal vein and discuss their surgical implications in living donor liver transplant (LDLT).

Methods and materials:

The study included an MDCT angiography evaluation of 450 liver donors. The hepatic artery and portal vein branching patterns were described according to Michel’s and Nakamura et al classification and miscellaneous findings were discussed separately.

Results:

Standard arterial anatomy was seen in 66% of cases. The most common arterial variant was type V followed by type III and II. The remaining Michel’s variants including type IV, VI, VIII, and IX were seen in 8% cases. The origin of the segment 4 artery was seen most commonly from LHA. In the remaining cases, it was seen originating from RHA, CHA, HAP, and both LHA and RHA.

Miscellaneous arterial anatomy was seen in 4% cases, including segmental arterial supply to the right lobe from LHA, GDA, CHA, and CA , early branching of the hepatic artery from CHA, aberrant origin of RHA from CA, GDA, and the aorta, and the origin of CA from SMA and the aorta.

Type A portal vein anatomy was seen in 83% cases followed by type C and B. Type D anatomy was seen in 1 case. Type E portal vein anatomy was seen in 2 cases. In 5 cases, branches to segment 7 and 8 were seen arising from LPV. In one case, the accessory segment 8 branch was arising from the MPV bifurcation.

Conclusion:

Variant hepatic vascular anatomy is seen in a significant number of donors and its evaluation allows the selection of suitable donors and operative procedures, and hence decreases intra-operative time and complications.

Limitations:

A single-centre study.

Ethics committee approval

n/a

Funding:

No funding was received for this work.

Purpose:

CT angiography (CTA) provides information on the patency of peripheral arteries and 3-phase scintigraphy can assess perfusion and viability of affected tissues. Our aim was to evaluate the utility of hybrid imaging comprising CTA and three-phase scintigraphy using osteotropic or perfusion radiotracers.

Methods and materials:

From September 2018-August 2019, we examined 79 patients (mean age 68.3±9.7) with acute lower limb ischaemia. The hybrid studies comprised CT angiography (CTA) and three-phase scintigraphy performed on Discovery 670NM/16-rowCT, GE, USA. Scintigraphy was performed in group 1 in 63/79 patients using ^99mТс-pyrоphosphate (500MBq, 2.85mSv) and in group 2 - in 16/79 using ^99mТс-MIBI (500MBq, 4.5mSv).

Results:

We evaluated two groups of patients based on the severity of ischaemia: grade 1-2A-51 (45/6), grade 2B-18 (13/5), and grade 3-10 (5/5); groups 1 and 2, respectively. 51/79 patients with grades 1-2А had either normal or slightly decreased tissue blood flow. 28/79 patients with grades 2B-3 had a significant decrease in tissue blood flow. In group 1, the washout index in tissue and bone phases ("muscle/muscle") was decreasing and the "muscle/bone ratio" index in bone phase was increasing, with a clear difference between grades 1-2A, 2B, and З. 4/5 patients from group 1 (grade 3) had areas of necrotic changes. In group 2, the washout index was significantly different between 1-2A-2B and 3 (р≤0.05). ^99mТс-pyrоphosphate studies were more informative for acute ischaemia grades with less radiation 2.85mSv vs 4.5mSv.

Conclusion:

CTA and scintigraphy are complementary and their fusion provides a reliable diagnosis of patency and grades of ischaemia. Moreover, hybrid imaging using osteotropic radiotracer defines the areas of aseptic necrosis, which is essential in planning endovascular or surgical intervention. ^99mТс-pyrоphosphate studies were more informative than ^99mТс-MIBI with less patient exposure.

Limitations:

The retrospective design.

Ethics committee approval

n/a

Funding:

No funding was received for this work.