Evaluation of non‐monoexponential diffusion models for hepatocellular carcinoma using b values up to 2000 s/mm²: A short‐term repeatability study

Abstract

Background Non‐monoexponential diffusion models are being used increasingly for the characterization and curative effect evaluation of hepatocellular carcinoma (HCC). But the fitting quality of the models and the repeatability of their parameters have not been assessed for HCC. Purpose To evaluate kurtosis, stretched exponential, and statistical models for diffusion‐weighted imaging (DWI) of HCC, using b‐values up to 2000 s/mm2, in terms of fitting quality and repeatability. Study Type Prospective. Population Eighteen patients with HCC. Field Strength/Sequence Conventional and DW images (b = 0, 200, 500, 1000, 1500, 2000 s/mm2) were acquired at 3.0T. Assessment The parameters of the kurtosis, stretched exponential, and statistical models were calculated on regions of interest (ROIs) of each lesion. Statistical Tests The fitting quality was evaluated through comparing the fitting residuals produced on the average data of ROI between different models using a paired t‐test or Wilcoxon rank‐sum test. Repeatability of the fitted parameters at the median values on the voxelwise data of ROI was assessed using the within coefficient of variation (WCV), the intraclass correlation coefficient (ICC), and the 95% Bland–Altman limits of agreements (BA‐LA). The repeatability was divided into four levels: excellent, good, acceptable, and poor, referring to the values of ICC and WCV. Results Among three models, the stretched exponential model provided the best fit to HCC (P < 0.05), whereas the statistical model produced the largest fitting residuals (P < 0.05). The repeatability of K from the kurtosis model was excellent (ICC 0.915; WCV 8.79%), while the distributed diffusion coefficient (DDC) from the stretched model was just acceptable (ICC 0.477; WCV 27.83%). The repeatability was good for other diffusion‐related parameters. Data Conclusion Considering the model fit and repeatability, the kurtosis and stretched exponential models are the preferred models for the description of the DW signals of HCC with respect to the statistical model. Level of Evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:297–304.

Scan Time Reduction in Intravoxel Incoherent Motion Diffusion-Weighted Imaging and Diffusion Kurtosis Imaging of the Abdominal Organs: Using a Simultaneous Multislice Technique With Different Acceleration Factors

“…These imaging techniques have been widely used to evaluate the degree of liver fibrosis, tumor characteristics, and treatment responses. [8][9][10][11][12][13] Generally, IVIM-DWI sequences require a minimum of 8 b value scans resulting in longer acquisition times, thereby limiting the integration of IVIM sequences into clinical protocols. The DKI requires ultra-high b-values (1500-2000 seconds/mm 2 ) for scanning procedures.…”

Non-mono-exponential diffusion models for assessing early response of liver metastases to chemotherapy in colorectal Cancer

“…The DWI images were acquired using a spin-echo EPI sequence with gated-navigator respiratory motion compensation technique (the navigator gating window was set as 5 mm). Six b values (0, 200, 500, 1000, 1500, 2000 s/mm 2 with 1, 1, 2, 2, 2, 4 signal averages, respectively) were applied in three orthogonal diffusion encoding directions [25]. The imaging parameters were: TR/TE 2000 /70 ms, number of slices 24, slice thickness 7 mm, slice gap 0 mm, matrix size 148 × 148, FOV 400 mm × 400 mm, NSA 2.…”

“…The ROIs were initially delineated on b0 image, then copied and pasted on corresponding DW images. The DW images were normalized by dividing them by the b0 images, and geometric mean of these images over different diffusion encoding directions was taken [25]. For each patient, the voxel-level DW data on ROIs were fitted by the non-mono-exponential diffusion models and the median values of calculated parameters over all ROIs were recorded as the measurements of the patient.…”

Diffusion weighted imaging and diffusion kurtosis imaging in abdominal oncological setting: why and when

“…Recently, several studies have evaluated the role of DKI in HCC for the characterization and evaluation of the response to treatment [1,83,[85][86][87][88][89][90]. However, the consistency and repeatability of the adapted parameters have not been assessed.…”