Application of diffusion kurtosis imaging in differential diagnosis of focal liver lesions.

Purpose: Diffusion kurtosis imaging (DKI) is an MRI method related to diffusion imaging (DWI) that is distinguished by a non-Gaussian calculation of water particles movements in tissues. The aim of the study was to assess DKI advantage over DWI in differentiating benign and malignant liver lesions. Material and methods: Analysis included prospectively acquired group of 83 patients referred consecutively for 3T-MRI liver tumor examination, with 95 liver lesions (31 benign, 59 malignant). MRI assessments were performed with standard protocol and DKI sequence with seven b-values (0-2,000 s/mm2). Quantitative data were acquired by placing ROIs in liver tumors on all b-value images, ROI data extracted, and calculation of DWI and DKI parameters. ADC was calculated for all b-values (ADC0-2000) and for three values of b = 0, 500, and 750 (s/mm2) (ADC0-500-750). DKI and ADC parameters for benign and malignant lesions were compared, and ROC curves were plotted. Results: Significant differences were obtained for all DKI and ADC parameters. ROC analysis showed AUC of DK, K, ADC0-2000, and ADC0-500-750 was 0.74, 0.77, 0.77, and 0.75, respectively. The highest sensitivity (of 0.91) was obtained for ADC0-2000. The highest specificity (0.65) and accuracy (0.80) was obtained for K. Conclusion: DKI technique yields statistically comparable results with DWI technique.

Summary of radiation dose management and optimization: comparison of radiation protection measures between Poland and other countries.

The purpose of this study is to show the actual recommendations for dose management and provide an overview of the available options for dose tracking and dose optimization. The legal institutions that supervise the radiological exposure of patients and their most important directives are presented. A literature review of existing diagnostic reference levels for computed tomography (CT), interventional radiology, radiography, paediatric radiography, mammography, and fluoroscopy in Europe and Poland was carried out. It has been shown that, in Poland, it is necessary to verify and determine the new diagnostic reference levels (DRLs) for each imaging modality because the existing ones are adapted from other countries and are not determined on the basis of data from Polish hospitals. They have not been updated for 11-17 years, although it is recommended to update them every 3-5 years. Many countries in Europe have already determined DRLs based on the analysis of their own dosage data (e.g. Austria and Germany). Analysing the existing DRLs for CT in Poland, it was noticed that they concern only a single anatomical region. It is necessary to determine the DRLs for multi-region CT (i.e. chest-abdomen-pelvis and neck-chest-abdomen-pelvis) examinations because these examinations account for about 60% of all oncological CT examinations-based on data collected from The Maria Sklodowska-Curie National Research Institute of Oncology in Warsaw.

Perfusion-Diffusion Ratio: A New IVIM Approach in Differentiating Solid Benign and Malignant Primary Lesions of the Liver.

INTRODUCTION: In order to improve the efficacy of intravoxel incoherent motion (IVIM) parameters in characterising specific tissues, a new concept is introduced: the perfusion-diffusion ratio (PDR), which expresses the relationship between the signal S(b) decline rate as a result of IVIM and the rate of signal S(b) decline due to diffusion. The aim of this study was to investigate this novel approach in the differentiation of solid primary liver lesions. Material and Methods. Eighty-three patients referred for liver MRI between August 2017 and January 2020 with a suspected liver tumour were prospectively examined with the standard liver MRI protocol extended by DWI-IVIM sequence. Patients with no liver lesions, haemangiomas, or metastases were excluded. The final study population consisted of 34 patients with primary solid liver masses, 9 with FNH, 4 with regenerative nodules, 10 with HCC, and 11 with CCC. The PDR coefficient was introduced, defined as the ratio of the rate of signal S(b) decrease due to the IVIM effect to the rate of signal S(b) decrease due to the diffusion process, for b = 0. RESULTS: No significant differences were found between benign and malignant lesions in the case of IVIM parameters (f, D, or D ∗) and ADC. Significant differences were observed only for PDR, with lower values for malignant lesions (p = 0.03). The ROC analysis yielded an AUC value for PDR equal to 0.74, with a cut-off value of 5.06, sensitivity of 81%, specificity of 77%, and accuracy of 79%. CONCLUSION: PDR proved to be more effective than IVIM parameters and ADC in the differentiation of solid benign and malignant primary liver lesions.

Intravoxel incoherent motion MRI in evaluating inflammatory activity in ulcerative colitis: a pilot study.

BACKGROUND: A non-invasive tool for the assessment of ulcerative colitis (UC) activity is needed for treatment control. PURPOSE: To determine the efficacy of intravoxel incoherent motion (IVIM) in assessing inflammatory activity in UC. MATERIAL AND METHODS: In this prospective study, 20 adult patients underwent 3.0-T magnetic resonance imaging (MRI) IVIM diffusion-weighted imaging (DWI) with 10 b-values (0-900 s/mm2) 0-6 days after biopsies entailing colonoscopy. The inflammatory activity of large bowel segments was graded on endoscopy with Mayo score and on pathology with a six­grade classification system. IVIM­derived parameters (f, D, and D*) calculated from regions of interest placed within the bowel wall were correlated with both scores (56 and 34 bowel segments, respectively). Radiologists were blinded to endoscopy and pathology results. A T-test and Wilcoxon rank sum test was used in comparisons and receiver operating characteristic curve analysis was performed. RESULTS: Statistically significant differences were found between histopathologically inactive or mild activity and moderate to severe activity in f (respectively: mean = 0.19 and mean = 0.28, P = 0.024; area under the curve [AUC] = 0.723, sensitivity 0.82, specificity 0.59, accuracy 0.67 for a 0.185 cut-off value) and D (mean = 1.34 × 10-3mm2/s and mean = 1.07 × 10-3mm2/s, P = 0.0083; AUC = 0.735, sensitivity 0.91, specificity 0.54, accuracy 0.66 for cut-off value 1.24 × 10-3mm2/s). No significant difference in D* was noted. No significant correlation between Mayo endoscopic subscore, and f, D, nor D* was found. CONCLUSION: IVIM perfusion fraction correlates with UC activity and might represent emerging tool in assessment of inflammatory activity.

Optimal b-values for diffusion kurtosis imaging of the liver and pancreas in MR examinations.

PURPOSE: The objective was to optimise the number of b-values for diffusion kurtosis imaging (DKI) of the liver and pancreas in MR examinations to ensure reliable results with the shortest possible acquisition time. METHODS: Twenty healthy volunteers underwent DKI at 3.0 T Siemens Magnetom Skyra using 7 b-values (b = 0, 200, 500, 750, 1000, 1500, 2000 s/mm2). The regions of interest (ROIs) were placed in the liver (right lobe, left lobe) and pancreas (head, tail). DKI parameters (Dapp, Kapp) for ROIs were calculated for 7 b-values utilising the nonlinear least-squares (NLLS) Marquardt-Levenberg algorithm. All calculations were repeated for ten subsets of data, with the number of b-values reduced to 4. DKI parameters calculated for subsets were compared with parameters calculated for all 7 b-values. RESULTS: The correlation coefficient between DKI parameters calculated for 7 b-values and subsets ranged from 0.65 to 1.00. The coefficient of variation (CoV) of DKI parameters calculated for a group of volunteers varied from 8% to 42% and was not affected by the reduction of the b-values number. Only one subset of data (b = 0, 500, 1500 and 2000 s/mm2) simultaneously met two criteria: no statistical difference (p < 0.05) from results obtained for 7 b-values and very good correlation with them. CONCLUSIONS: DKI acquisition with 4 b-values (b = 0, 500, 1500 and 2000 s/mm2), compared to DKI acquisition utilising 7 b-values, allowed for the reduction of acquisition time by 36%, without affecting the calculated DKI parameters.

Reproducibility of intravoxel incoherent motion of liver on a 3.0T scanner: free-breathing and respiratory-triggered sequences acquired with different numbers of excitations.

PURPOSE: To optimise the intravoxel incoherent motion (IVIM) imaging of the liver on a 3.0T scanner by assessing parameter reproducibility on free-breathing (FB) and respiratory-triggered (RT) sequences acquired with different numbers of signal averages (NSA). MATERIAL AND METHODS: In this prospective study 20 subjects (M/F: 10/10; age: 25-62 years, mean: 39 years) underwent IVIM magnetic resonance imaging (MRI) on a 3.0T scanner using an 18-channel phase-arrayed coil and four different echo-planar sequences, each with 10 b values: 0, 10, 30, 50, 75, 100, 150, 200, 500, and 900 s/mm2. Images were acquired with FB and RT with NSA = 1-4 (FBNSA1-4, RTNSA1-4) and with NSA = 3-6 (FBNSA3-6, RTNSA3-6). Subsequently, for the assessment of reproducibility of IVIM-derived parameters (f, D, D*), each subject was scanned again with an identical protocol during the same session. IVIM parameters were calculated. The distribution of IVIM-parameters for each DWI sequence were given as the median value with first and third quartile. Inter-scan reproducibility for each IVIM parameter was evaluated using coefficient of variance and Bland-Altman difference. Differences between FB sequence and RT sequence were tested using non-parametric Wilcoxon signed-rank test. RESULTS: Mean coefficient of variance (%) for f, D, and D* ranged from 60 to 64, from 58 to 84, and from 82 to 99 for FBNSA1-4 sequence; from 50 to 69, from 41 to 97, and from 80 to 82 for RTNSA1-4 sequence; from 22 to 27, 15, and from 70 to 80 for FBNSA3-6 sequence; and from 21 to 32, from 12 to, and from 50 to 80 for RTNSA3-6 sequence, respectively. CONCLUSIONS: Increasing the number of signal averages for IVIM acquisitions allows us to improve the reproducibility of IVIM-derived parameters. The sequence acquired during free-breathing with NSA = 3-6 was optimal in terms of reproducibility and acquisition time.