Quantitative diffusion-weighted imaging in breast and liver tissue

Diffusie-gewogen beeldvorming (DWI) is een biomedische toepassing van MRI, gebaseerd op diffusie (de willekeurige verplaatsing) van waterstof protonen in het menselijk lichaam. Met o.a. DWI beelden beoordeelt een radioloog visueel of er afwijkingen aanwezig zijn in het onderzochte orgaan.Visuele beoordeling is echter subjectief. Een alternatief is kwantitatieve analyse, waarbij de diffusie in afwijkingen wordt gemeten, uitgedrukt in een getal en vergeleken met gezond weefsel. Dit heeft als voordeel dat de beoordeling niet of nauwelijks afhangt van diegene die het uitvoert. Er zijn twee modellen onderzocht voor de kwantitatieve analyse van diffusie in de lever en de borst. Het intravoxel incoherent motion (IVIM) model splitst diffusie op in langzame en snelle diffusie. Snelle diffusie komt voor in goed doorbloede weefsels, zoals tumoren. Het tweede model gebruikt een enkele maat, de apparent diffusion coefficient (ADC). De voor- en nadelen van beide modellen zijn onderzocht in DWI studies van de lever. Diffusie is afhankelijk van het vetpercentage en de ADC blijkt bovendien afhankelijk van de meetlocatie in de lever.Er is een nieuwe methode geïntroduceerd waarmee de beoordelaar semiautomatisch een borsttumor kan selecteren en analyseren. IVIM kan hierdoor beter goed- en kwaadaardige borsttumoren van elkaar onderscheiden, vergeleken met de ADC. Ook bleek de methode onafhankelijk van de beoordelaar. In de dagelijkse praktijk ondergaat een groep patiënten met verdenking op borstkanker een invasieve procedure om uitsluitsel te geven. In de toekomst kan mogelijk een aantal van deze invasieve procedures worden voorkomen door het integreren van IVIM in het diagnostische proces.Diffusion-weighted imaging (DWI) is a biomedical application of MRI, based on diffusion (random walk) of hydrogen protons in the human body. By visual inspection of DWI, and other MRI images, the radiologist determines whether there is any pathology present in the organ examined.Visual assessment is subjective. Quantitative analysis provides an objective alternative for assessing the diffusion of pathology by expressing it in a number in comparison with healthy tissue. The benefit of this approach is that it does not depend on the reader. Two models for quantitative analysis of diffusion in the liver and breast were investigated. The intravoxel incoherent motion (IVIM) model separates diffusion into slow and fast diffusion. Fast diffusion is present in highly perfused tissues, such as tumors. The second model describes only one parameter, the apparent diffusion coefficient (ADC). Benefits and drawbacks of both models were investigated in DWI studies of the liver. Diffusion is dependent on the hepatic fat fraction, and the ADC furthermore on the measurement location in the liver.A novel method was introduced for semi-automatic selection and analysis of breast lesions. This provides better discrimination between benign and malignant breast lesions compared to the ADC. Moreover, the method appeared independent of the reader.In daily practice, a group of patients suspected of breast cancer is subject to an invasive procedure to provide a diagnosis. The number of invasive procedures may be reduced in the future when IVIM is implemented in the diagnostic algorithm

Inter-observer reproducibility of quantitative dynamic susceptibility contrast and diffusion MRI parameters in histogram analysis of gliomas

Background Dynamic-susceptibility contrast and diffusion-weighted imaging are promising techniques in diagnosing glioma grade. Purpose To compare the inter-observer reproducibility of multiple dynamic-susceptibility contrast and diffusion-weighted imaging parameters and to assess their potential in differentiating low- and high-grade gliomas. Material and Methods Thirty patients (16 men; mean age = 40.6 years) with low-grade (n = 13) and high-grade (n = 17) gliomas and known pathology, scanned with dynamic-susceptibility contrast and diffusion-weighted imaging were included retrospectively between March 2006 and March 2014. Three observers used three different methods to define the regions of interest: (i) circles at maximum perfusion and minimum apparent diffusion coefficient; (ii) freeform 2D encompassing the tumor at largest cross-section only; (iii) freeform 3D on all cross-sections. The dynamic-susceptibility contrast curve was analyzed voxelwise: maximum contrast enhancement; time-to-peak; wash-in rate; wash-out rate; and relative cerebral blood volume. The mean was calculated for all regions of interest. For 2D and 3D methods, histogram analysis yielded additional statistics: the minimum and maximum 5% and 10% pixel values of the tumor (min5%, min10%, max5%, max10%). Intraclass correlations coefficients (ICC) were calculated between observers. Low- and high-grade tumors were compared with independent t-tests or Mann-Whitney tests. Results ICCs were highest for 3D freeform (ICC = 0.836-0.986) followed by 2D freeform (ICC = 0.854-0.974) and circular regions of interest (0.141-0.641). High ICC and significant discrimination between low- and high-grade gliomas was found for the following optimized parameters: apparent diffusion coefficient (P <0.001; ICC = 0.641; mean; circle); time-to-peak (P = 0.015; ICC = 0.986; mean; 3D); wash-in rate (P = 0.004; ICC = 0.826; min10%; 3D); wash-out rate (P <0.001; ICC = 0.860; min10%; 2D); and relative cerebral blood volume (

Which patients are prone to undergo disproportionate recurrent CT imaging and should we worry?

Purpose: To identify the spectrum of patients who undergo disproportionate recurrent computed tomography (CT) imaging, and to explore the cumulative effects of radiation exposure and intravenously injected contrast agents in these patients. Methods: This retrospective study investigated all patients who had undergone 40 or more CT scans at a tertiary care center between 2007–2017. Results: Fifty-six patients who had undergone a median of 47 (range: 40–92) CT scans were included. The main reason for CT scanning in all patients was oncological, and 55 patients (98.2 %) had metastatic disease. Twenty-six patients (45.6) had received chemotherapy, 35 (62.5 %) radiation therapy, 38 (67.9 %) targeted therapy, 12 (21.4 %) liver tumor microwave ablation, 44 (78.6 %) major surgery, and 34 (60.7 %) had participated in a therapeutic trial. Mean cumulative effective dose was 187.4 mSv (range: 120.7–278.4 mSv). Median estimated radiation-induced lifetime attributable risk (LAR) of cancer incidence was 1.0 % (range: 0.20–2.36 %). Mean estimated radiation-induced LAR of cancer mortality was 0.68 % (range: 0.18–1.37 %). Mean cumulative volume of intravenously injected iomeprol was 2339 mL (range: 540−3605 mL). Three patients (5.4 %) had developed severely decreased kidney function (estimated glomerular filtration rate between 15 and 29 mL/min per 1.73 m² for at least 3 months). Conclusion: Patients with metastatic disease who experience a relatively long survival may be prone to undergo disproportionate recurrent CT imaging. The non-negligible CT radiation-induced cancer risk and mortality should be taken into account in these patients, while the effect of cumulatively administered CT contrast agents on kidney function requires further investigation

Comparison of conventional and higher-resolution reduced-FOV diffusion-weighted imaging of breast tissue

Objective: Reduced FOV-diffusion-weighted imaging (rFOV-DWI) allows for acquisition of a tissue region without back-folding, and may have better fat suppression than conventional DWI imaging (c-DWI). The aim was to compare the ADCs obtained with c-DWI bilateral-breast imaging with single-breast rFOV-DWI. Materials and Methods: Breasts of 38 patients were scanned at 3 T. The mean ADC values obtained for 38 lesions, and fibro-glandular (N = 35) and adipose (N = 38) tissue ROIs were compared between c-DWI and higher-resolution rFOV-DWI (Wilcoxon rank test). Also, the ADCs were compared between the two acquisitions for an oil-only phantom and a combined water/oil phantom. Furthermore, ghost artifacts were assessed. Results: No significant difference in mean ADC was found between the acquisitions for lesions (c-DWI: 1.08 × 10–3 mm2/s, rFOV-DWI: 1.13 × 10–3 mm2/s) and fibro-glandular tissue. For adipose tissue, the ADC using rFOV-DWI (0.31 × 10–3 mm2/s) was significantly higher than c-DWI (0.16 × 10–3 mm2/s). For the oil-only phantom, no difference in ADC was found. However, for the water/oil phantom, the ADC of oil was significantly higher with rFOV-DWI compared to c-DWI. Discussion: Although ghost artifacts were observed for both acquisitions, they appeared to have a greater impact for rFOV-DWI. However, no differences in mean lesions’ ADC values were found, and therefore this study suggests that rFOV can be used diagnostically for single-breast DWI imaging.</p

Comparison of conventional and higher-resolution reduced-FOV diffusion-weighted imaging of breast tissue

Objective: Reduced FOV-diffusion-weighted imaging (rFOV-DWI) allows for acquisition of a tissue region without back-folding, and may have better fat suppression than conventional DWI imaging (c-DWI). The aim was to compare the ADCs obtained with c-DWI bilateral-breast imaging with single-breast rFOV-DWI. Materials and Methods: Breasts of 38 patients were scanned at 3 T. The mean ADC values obtained for 38 lesions, and fibro-glandular (N = 35) and adipose (N = 38) tissue ROIs were compared between c-DWI and higher-resolution rFOV-DWI (Wilcoxon rank test). Also, the ADCs were compared between the two acquisitions for an oil-only phantom and a combined water/oil phantom. Furthermore, ghost artifacts were assessed. Results: No significant difference in mean ADC was found between the acquisitions for lesions (c-DWI: 1.08 × 10–3 mm2/s, rFOV-DWI: 1.13 × 10–3 mm2/s) and fibro-glandular tissue. For adipose tissue, the ADC using rFOV-DWI (0.31 × 10–3 mm2/s) was significantly higher than c-DWI (0.16 × 10–3 mm2/s). For the oil-only phantom, no difference in ADC was found. However, for the water/oil phantom, the ADC of oil was significantly higher with rFOV-DWI compared to c-DWI. Discussion: Although ghost artifacts were observed for both acquisitions, they appeared to have a greater impact for rFOV-DWI. However, no differences in mean lesions’ ADC values were found, and therefore this study suggests that rFOV can be used diagnostically for single-breast DWI imaging.</p

Comparison of conventional and higher-resolution reduced-FOV diffusion-weighted imaging of breast tissue

Objective: Reduced FOV-diffusion-weighted imaging (rFOV-DWI) allows for acquisition of a tissue region without back-folding, and may have better fat suppression than conventional DWI imaging (c-DWI). The aim was to compare the ADCs obtained with c-DWI bilateral-breast imaging with single-breast rFOV-DWI. Materials and Methods: Breasts of 38 patients were scanned at 3 T. The mean ADC values obtained for 38 lesions, and fibro-glandular (N = 35) and adipose (N = 38) tissue ROIs were compared between c-DWI and higher-resolution rFOV-DWI (Wilcoxon rank test). Also, the ADCs were compared between the two acquisitions for an oil-only phantom and a combined water/oil phantom. Furthermore, ghost artifacts were assessed. Results: No significant difference in mean ADC was found between the acquisitions for lesions (c-DWI: 1.08 × 10–3 mm2/s, rFOV-DWI: 1.13 × 10–3 mm2/s) and fibro-glandular tissue. For adipose tissue, the ADC using rFOV-DWI (0.31 × 10–3 mm2/s) was significantly higher than c-DWI (0.16 × 10–3 mm2/s). For the oil-only phantom, no difference in ADC was found. However, for the water/oil phantom, the ADC of oil was significantly higher with rFOV-DWI compared to c-DWI. Discussion: Although ghost artifacts were observed for both acquisitions, they appeared to have a greater impact for rFOV-DWI. However, no differences in mean lesions’ ADC values were found, and therefore this study suggests that rFOV can be used diagnostically for single-breast DWI imaging.</p

Introduction of the Grayscale Median for Ultrasound Tissue Characterization of the Transplanted Kidney

Ultrasound examination is advised for early post-kidney transplant assessment. Grayscale median (GSM) quantification is novel in the kidney transplant field, with no systematic assessment previously reported. In this prospective cohort study, we measured the post-operative GSM in a large cohort of adult kidney transplant recipients (KTR) who consecutively underwent Doppler ultrasound directly after transplantation (within 24 h), compared it with GSM in nontransplanted patients, and investigated its association with baseline and follow-up characteristics. B-mode images were used to calculate the GSM in KTR and compared with GSM data in nontransplanted patients, as simulated from summary statistics of the literature using a Mersenne twister algorithm. The association of GSM with baseline and 1-year follow-up characteristics were studied by means of linear regression analyses. In 282 KTR (54 ± 15 years old, 60% male), the median (IQR) GSM was 55 (45-69), ranging from 22 to 124 (coefficient of variation = 7.4%), without differences by type of donation (p = 0.28). GSM in KTR was significantly higher than in nontransplanted patients (p < 0.001), and associated with systolic blood pressure, history of cardiovascular disease, and donor age (std. β = 0.12, -0.20, and 0.13, respectively; p < 0.05 for all). Higher early post-kidney transplant GSM was not associated with 1-year post-kidney transplant function parameters (e.g., measured and estimated glomerular filtration rate). The data provided in this study could be used as first step for further research on the application of early postoperative ultrasound in KTR

Clinical Implications of Non-Steatotic Hepatic Fat Fractions on Quantitative Diffusion-Weighted Imaging of the Liver

Diffusion-weighted imaging (DWI) is an important diagnostic tool in the assessment of focal liver lesions and diffuse liver diseases such as cirrhosis and fibrosis. Quantitative DWI parameters such as molecular diffusion, microperfusion and their fractions, are known to be affected when hepatic fat fractions (HFF) are higher than 5.5% (steatosis). However, less is known about the effect on DWI for HFF in the normal non-steatotic range below 5.5%, which can be found in a large part of the population. The aim of this study was therefore to evaluate the diagnostic implications of non-steatotic HFF on quantitative DWI parameters in eight liver segments. For this purpose, eleven healthy volunteers (2 men, mean-age 31.0) were prospectively examined with DWI and three series of in-/out-of-phase dual-echo spoiled gradient-recalled MRI sequences to obtain the HFF and T-2*. DWI data were analyzed using the intravoxel incoherent motion (IVIM) model. Four circular regions (circle divide 22.3 mm) were drawn in each of eight liver segments and averaged. Measurements were divided in group 1 (HFF 5.5%). DWI parameters and T-2* were compared between the three groups and between the segments. It was observed that the molecular diffusion (0.85, 0.72 and 0.49610 23 mm(2)/s) and T-2* (32.2, 27.2 and 21.0 ms) differed significantly between the three groups of increasing HFF (2.18, 3.50 and 19.91%). Microperfusion and its fraction remained similar for different HFF. Correlations with HFF were observed for the molecular diffusion (r = -0.514,