Endoleak detection using single-acquisition split-bolus dual-energy computer tomography (DECT).

OBJECTIVES: To assess a single-phase, dual-energy computed tomography (DECT) with a split-bolus technique and reconstruction of virtual non-enhanced images for the detection of endoleaks after endovascular aneurysm repair (EVAR). METHODS: Fifty patients referred for routine follow-up post-EVAR CT and a history of at least one post-EVAR follow-up CT examination using our standard biphasic (arterial and venous phase) routine protocol (which was used as the reference standard) were included in this prospective trial. An in-patient comparison and an analysis of the split-bolus protocol and the previously used double-phase protocol were performed with regard to differences in diagnostic accuracy, radiation dose, and image quality. RESULTS: The analysis showed a significant reduction of radiation dose of up to 42 %, using the single-acquisition split-bolus protocol, while maintaining a comparable diagnostic accuracy (primary endoleak detection rate of 96 %). Image quality between the two protocols was comparable and only slightly inferior for the split-bolus scan (2.5 vs. 2.4). CONCLUSIONS: Using the single-acquisition, split-bolus approach allows for a significant dose reduction while maintaining high image quality, resulting in effective endoleak identification. KEY POINTS: • A single-acquisition, split-bolus approach allows for a significant dose reduction. • Endoleak development is the most common complication after endovascular aortic repair (EVAR). • CT angiography is the imaging modality of choice for aortic aneurysm evaluation.

Utility and limitations of 3-Tesla diffusion-weighted magnetic resonance imaging for differentiation of renal tumors.

OBJECTIVE: To investigate utility and limitations of 3-Tesla diffusion-weighted (DW) magnetic resonance imaging (MRI) for differentiation of benign versus malignant renal lesions and renal cell carcinoma (RCC) subtypes. MATERIALS AND METHODS: Sixty patients with 71 renal lesions underwent 3 Tesla DW-MRI of the kidney before diagnostic tissue confirmation. The images were retrospectively evaluated blinded to histology. Single-shot echo-planar imaging was used as the DW imaging technique. Apparent diffusion coefficient (ADC) values were measured and compared with histopathological characteristics. RESULTS: There were 54 malignant and 17 benign lesions, 46 lesions being small renal masses ≤ 4 cm. Papillary RCC lesions had lower ADC values (p=0.029) than other RCC subtypes (clear cell or chromophobe). Diagnostic accuracy of DW-MRI for differentiation of papillary from non-papillary RCC was 70.3% resulting in a sensitivity and specificity of 64.3% (95% CI, 35.1-87.2) and 77.1 (95% CI, 59.9-89.6%). Accuracy increased to 83.7% in small renal masses (≤ 4 cm diameter) and sensitivity and specificity were 75.0% and 88.5%, respectively. The ADC values did not differ significantly between benign and malignant renal lesions (p=0.45). CONCLUSIONS: DW-MRI seems to distinguish between papillary and other subtypes of RCCs especially in small renal masses but could not differentiate between benign and malignant renal lesions. Therefore, the use of DW-MRI for preoperative differentiation of renal lesions is limited.

Three-Tesla dynamic contrast-enhanced MRI: a critical assessment of its use for differentiation of renal lesion subtypes.

PURPOSE: To evaluate the ability of dynamic contrast-enhanced (DCE) 3-T MRI for preoperative differentiation between benign and malignant renal tumors and RCC subtypes. METHODS: Sixty consecutive patients undergoing preoperative DCE 3-T MRI of the kidney were evaluated in this retrospective IRB-approved evaluation. Fifty-four malignant tumors and 17 benign tumors upon surgical verification were included. Relative enhancement values of complete lesions and the most enhancing part of the lesions (hotspot) were measured using four repetitions: precontrast, arterial, venous, and delayed. RESULTS: Mean relative enhancement patterns between malignant and benign lesions did not differ significantly during any postcontrast phase (p > 0.05). The highest mean enhancement during all postcontrast phases was identified in clear cell RCC followed by chromophobic RCC. The enhancement pattern in papillary RCC was significantly less than that of non-papillary RCC lesions. Arterial enhancement was an independent predictor for RCC subtypes (papillary vs. non-papillary, p = 0.008). The diagnostic accuracy for differentiation of papillary from non-papillary RCC based on ROC analysis was 76.4% [95% CI 62.2-87.2%]; p < 0.0001. CONCLUSIONS: Dynamic contrast-enhanced MRI at 3 T showed intermediate diagnostic capability for differentiation between papillary and non-papillary RCC subtypes but could not differentiate between benign and malignant renal lesions.