Marc Haspeslagh

Model-based Iterative Reconstruction and Adaptive Statistical Iterative Reconstruction Techniques in Abdominal CT: Comparison of Image Quality in the Detection of Colorectal Liver Metastases

PURPOSEnTo prospectively evaluate dose reduction and image quality characteristics of abdominal computed tomographic (CT) scans reconstructed with model-based iterative reconstruction (MBIR) compared with adaptive statistical iterative reconstruction (ASIR) in oncology patients with colorectal liver metastases.nnnMATERIALS AND METHODSnThe study complied with HIPAA guidelines and was approved by the ethics committee of the institutional review board. All patients gave written informed consent. Fifty-one patients with colorectal liver metastases underwent body CT (thorax and abdomen) with a 64-section multidetector unit. With a radiation dose reduction by 2.36 mGy compared to standard of care CT with ASIR 50% (radiation dose, 7.54 mGy), MBIR can provide diagnostically acceptable CT scans without compromising image quality. Two radiologists independently assessed randomized images in a blinded manner. Imaging sets were compared for lesion detection, lesion conspicuity, overall image quality, and signal-to-noise ratio with a paired sample t test. Inter- and intraobserver agreement was assessed with the Cohen κ.nnnRESULTSnThe mean volume CT dose index was 5.18 mGy ± 0.76, mean dose-length product 374 mGy · cm ± 63.47, mean effective diameter 29.38 cm ± 3.46, and mean size-specific dose estimate 6.52 mGy ± 0.73. In small liver lesions (<10 mm), detection and conspicuity were significantly higher with MBIR than with ASIR for both right (t = 3.245, P = .004 and t = 2.696, P = .013, respectively) and left (t = 2.390, P = .038 and t = 2.283, P = .046) liver lobes. Subjective image noise (t = 4.506, P < .001), artifacts (t = 3.479, P = .001), and diagnostic confidence (t = 2.643, P = .011) were significantly better with MBIR than with ASIR.nnnCONCLUSIONnMBIR performed better than ASIR 50% at providing diagnostically acceptable CT scans without compromising image quality and in the detection of colorectal liver metastases.

Improved focal liver lesion detection: comparison of single-shot spin-echo echo-planar and superparamagnetic iron oxide (SPIO)-enhanced MRI.

To prospectively compare single‐shot spin‐echo echo‐planar imaging (SSSE‐EPI) using b = 0, 10, 150, and 400 seconds/mm2 with standard MRI techniques after intravenous super paramagnetic iron oxide (SPIO) in the detection and characterization of focal liver lesions with focus on small (<10 mm) focal liver lesions.

Focal liver lesion detection and characterization: Comparison of non-contrast enhanced and SPIO-enhanced diffusion-weighted single-shot spin echo echo planar and turbo spin echo T2-weighted imaging

PURPOSEnTo compare lesion conspicuity and image quality between single-shot spin echo echo planar imaging (SS SE-EPI) before, immediately and 5min after intravenous (IV) injection of superparamagnetic iron oxide (SPIO) for detecting and characterizing focal liver lesions (FLLs).nnnMATERIALS AND METHODSnTwenty-five patients suspected for colorectal liver metastases were prospectively included. Lesion detection and characterization were compared between all SS SE-EPI and T2-weighted turbo spin echo (T2w TSE) sets (two-sided Fishers exact test). Image quality and lesion conspicuity were compared for SS SE-EPI sets using rank order statistic (RIDIT). Reference standard comprised of surgery, biopsy and/or follow-up.nnnRESULTSnReference standard demonstrated 18 benign and 43 malignant FLLs. Best lesion detection (p<0.05) was achieved with non-contrast-enhanced SS SE-EPI. Lesion characterization was best using all T2w TSE sequences. Best image quality and lesion conspicuity (p<0.05) was achieved with non-contrast-enhanced SS SE-EPI.nnnCONCLUSIONnNon-contrast-enhanced SS SE-EPI was best for lesion detection. SS SE-EPI sequences were not useful for lesion characterization (differentiation between benign and malignant lesions). Unenhanced SS SE-EPI did not allow differentiation especially as many benign FLLs were hyperintense on the highest b-value images. Combining unenhanced and SPIO-enhanced SS SE-EPI performed better but still was not clinically useful due to variable degree of uptake and vascular pooling of SPIO for (especially) benign FLLs. T2w TSE with SPIO-enhancement was needed for characterization.

Perfusion maps of the whole liver based on high temporal and spatial resolution contrast-enhanced MRI (4D THRIVE): Feasibility and initial results in focal liver lesions

PURPOSEnTo prospectively evaluate a new imaging sequence (4D THRIVE) for whole liver perfusion in high temporal and spatial resolution. Feasibility of parametric mapping and its potential for characterizing focal liver lesions (FLLs) are investigated.nnnMATERIALS AND METHODSnFifteen patients suspected for colorectal liver metastases (LMs) were included. Parametric maps were evaluated qualitatively (ring-enhancement and lesion heterogeneity) and compared to three-phased contrast-enhanced MRI. Quantitative analysis was based on average perfusion values of entire FLLs. Reference standard comprised surgery with histopathology or follow-up imaging. Fishers exact test was used for qualitative and Kruskal-Wallis test for quantitative analysis.nnnRESULTSnIn total 29 LMs, 17 hemangiomas and 4 focal nodular hyperplasias were evaluated. FLLs could be differentiated by qualitative assessment of parametric maps respectively three-phased contrast-enhanced MRI (Fishers p<0.001 for comparisons between LMs and hemangiomas and LMs and FNHs for both ring-enhancement and lesion heterogeneity) rather than by quantitative analysis of parametric maps (Chi-square for Kep=0.33 (p=0.847) and Chi-square for Kel=1.35 (p=0.509)).nnnCONCLUSIONnThis preliminary study shows potential of 4D THRIVE for whole liver imaging enabling calculation of parametric maps. Qualitative rather than quantitative analysis was accurate for differentiating malignant and benign FLLs.

Prediction and monitoring of treatment effect using T1-weighted dynamic contrast-enhanced magnetic resonance imaging in colorectal liver metastases: Potential of whole tumour ROI and selective ROI analysis

PURPOSEnTo evaluate dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) for prediction and early monitoring of treatment in colorectal liver metastases.nnnMATERIALS AND METHODSnTen patients were included. Baseline and follow-up DCE-MRI examinations were evaluated by whole tumour and selected ROI placements calculating Kep-values. Selective ROIs, concentric-like and hot spot, were drawn on early arterial phase images. Monitoring of treatment was performed comparing RECIST1.1 criteria with whole tumour and selected ROI placement. To evaluate treatment effect between responders and non-responders, independent samples t-test was used on Kep-values.nnnRESULTSnIn each patient largest lesion was evaluated totalling 10 target lesions. At baseline, for whole tumour ROI placements mean Kep-values in responders were significantly higher than mean Kep-values in non-responders (t=7.481, p<0.001). Selective ROI placement comparison of mean Kep-values at baseline and after 6 weeks of treatment (first follow-up measurement) showed significant decrease in responding patients (t=4.706, p=0.003) whereas increase in Kep-values in non-responding patients was not statistically significant.nnnCONCLUSIONnThis preliminary study shows that baseline Kep for whole tumour ROI is a predictor for treatment outcome. Decrease of Kep using selective ROIs allows early identification of response after 6 weeks of treatment.

A prospective clinical study using a dynamic contrast-enhanced CT-protocol for detection of colorectal liver metastases

OBJECTIVEnTo evaluate a dynamic contrast-enhanced CT-protocol and compare this method with standard of care monophasic portovenous CT for detection of colorectal liver metastases.nnnMATERIALS AND METHODSnA dynamic contrast-enhanced CT protocol was developed to detect liver metastasis in patients suffering from colorectal cancer, in clinical practice. The study was approved by the Hospital Ethics Committee. Written informed consent was obtained from all patients. 135 patients were included in this prospective study. All patients were naive to treatment. A dynamic contrast-enhanced CT was performed, followed by routine monophasic portovenous CT of thorax-abdomen-pelvis. 42 of these patients presented with liver metastasis. The number and lesion conspicuity of detected liver metastasis on dynamic contrast-enhanced CT using perfusion maps, was compared to monophasic CT.nnnRESULTSn135 patients were included, of which 42 presented with metastases to the liver. Dynamic contrast-enhanced CT outperformed portovenous CT for detection as well as conspicuity of colorectal liver metastasis, at a relatively low dose increment. Wilcoxon Signed Rank test had a p-value of 0.016 and <0.001 respectively for detection and conspicuity of colorectal liver metastasis.nnnCONCLUSIONnDynamic contrast-enhanced CT increases the detection of colorectal liver metastasis, especially for lesions smaller than 15u2009mm, when compared to monophasic portovenous CT. Dynamic contrast-enhanced CT also has the added advantage of improved lesion conspicuity, which can positively influence reader confidence and clinical workflow.

Intravoxel incoherent motion and dynamic contrast-enhanced MRI for differentiation between hepatocellular adenoma and focal nodular hyperplasia

OBJECTIVEnTo examine if intravoxel incoherent motion (IVIM) and dynamic contrast-enhanced MRI (DCE-MRI) can be used as new and supplemental MRI techniques to differentiate hepatocellular adenomas (HCAs) from focal nodular hyperplasias (FNHs) and analyse if diffusion parameter apparent diffusion coefficient (ADC) and IVIM parameter true diffusion coefficient (D) differ in doing so.nnnMETHODSnThis prospective study included 21 patients (8 HCAs and 13 FNHs) who underwent a specifically designed MRI scanning protocol, including series for analysis of IVIM (four b-values 0, 10, 150 and 800u2009su2009mm-2) and DCE-MRI. On a dedicated workstation, identical regions of interest were placed in parametric maps of Ktrans, Ve, D and ADC in each lesion for quantification. Diagnostic accuracy was assessed using receiver operating characteristics analysis. Time-intensity curves (TICs) were classified in different types.nnnRESULTSnHCAs had significantly lower values for Ktrans (mean 1.45 vs 2.68u2009min-1; pu2009=u20090.029) and D (mean 1.02u2009×u200910-3 vs 1.22u2009×u200910-3u2009mm2u2009s-1; pu2009=u20090.033). Both parameters showed good diagnostic accuracy of 76%. TIC analysis could not differentiate between HCAs and FNHs.nnnCONCLUSIONnIn this exploratory study, Ktrans and D were able to differentiate HCAs from FNHs in most cases, whereas Ve, ADC and TIC analysis were not. Advances in knowledge: Histological differences between HCAs and FNHs can be quantified on MRI using Ktrans and D.