Nicola Schieda

Multiparametric MRI of solid renal masses: pearls and pitfalls.

Functional imaging [diffusion-weighted imaging (DWI) and dynamic contrast enhancement (DCE)] techniques combined with T2-weighted (T2W) and chemical-shift imaging (CSI), with or without urography, constitutes a comprehensive multiparametric (MP) MRI protocol of the kidneys. MP-MRI of the kidneys can be performed in a time-efficient manner. Breath-hold sequences and parallel imaging should be used to reduce examination time and improve image quality. Increased T2 signal intensity (SI) in a solid renal nodule is specific for renal cell carcinoma (RCC); whereas, low T2 SI can be seen in RCC, angiomyolipoma (AML), and haemorrhagic cysts. Low b-value DWI can replace conventional fat-suppressed T2W. DWI can be performed free-breathing (FB) with two b-values to reduce acquisition time without compromising imaging quality. RCC demonstrates restricted diffusion; however, restricted diffusion is commonly seen in AML and in chronic haemorrhage. CSI must be performed using the correct echo combination at 3 T or T2* effects can mimic intra-lesional fat. Two-dimensional (2D)-CSI has better image quality compared to three-dimensional (3D)-CSI, but volume averaging in small lesions can simulate intra-lesional fat using 2D techniques. SI decrease on CSI is present in both AML and clear cell RCC. Verification of internal enhancement with MRI can be challenging and is improved with image subtraction. Subtraction imaging is prone to errors related to spatial misregistration, which is ameliorated with expiratory phase imaging. SI ratios can be used to confirm subtle internal enhancement and enhancement curves are predictive of RCC subtype. MR urography using conventional extracellular gadolinium must account for T2* effects; however, gadoxetic acid enhanced urography is an alternative. The purpose of this review it to highlight important technical and interpretive pearls and pitfalls encountered with MP-MRI of solid renal masses.

Whole-Tumor Quantitative Apparent Diffusion Coefficient Histogram and Texture Analysis to Predict Gleason Score Upgrading in Intermediate-Risk 3 + 4 = 7 Prostate Cancer

OBJECTIVE The objective of our study was to evaluate whole-lesion quantitative apparent diffusion coefficient (ADC) for the prediction of Gleason score (GS) upgrading in 3 + 4 = 7 prostate cancer. MATERIALS AND METHODS Fifty-four patients with GS 3 + 4 = 7 prostate cancer diagnosed at systematic transrectal ultrasound (TRUS)-guided biopsy underwent 3-T MRI and radical prostatectomy (RP) between 2012 and 2014. A blinded radiologist contoured dominant tumors on ADC maps using histopathologic correlation. The whole-lesion mean ADC, ADC ratio (normalized to peripheral zone), ADC histogram, and texture analysis were compared between tumors with GS upgrading and those without GS upgrading using multivariate ROC analyses and logistic regression modeling. RESULTS Tumors were upgraded to GS 4 + 3 = 7 after RP in 26% (n = 14) of the 54 patients, and tumors were downgraded after RP in none of the patients. The mean ADC, ADC ratio, 10th-centile ADC, 25th-centile ADC, and 50th-centile ADC were similar between patients with GS 3 + 4 = 7 tumors (0.99 ± 0.22, 0.58 ± 0.15, 0.77 ± 0.31, 0.94 ± 0.28, and 1.15 ± 0.24, respectively) and patients with upgraded GS 4 + 3 = 7 tumors (1.02 ± 0.18, 0.55 ± 0.11, 0.71 ± 0.26, 0.89 ± 0.20, and 1.11 ± 0.16) (p > 0.05). Regression models combining texture features improved the prediction of GS upgrading. The combination of kurtosis, entropy, and skewness yielded an AUC of 0.76 (SE = 0.07) (p < 0.001), a sensitivity of 71%, and a specificity of 73%. The combination of kurtosis, heterogeneity, entropy, and skewness yielded an AUC of 0.77 (SE = 0.07) (p < 0.001), a sensitivity of 71%, and a specificity of 78%. CONCLUSION In this study, whole-lesion mean ADC, ADC ratio, and ADC histogram analysis were not predictive of pathologic upgrading of GS 3 + 4 = 7 prostate cancer after RP. ADC texture analysis improved accuracy.

Focal Nodular Hyperplasia and Hepatocellular Adenoma: Accuracy of Gadoxetic Acid–enhanced MR Imaging—A Systematic Review

Although the reported diagnostic accuracy in the differentiation of hepatocellular adenoma from focal nodular hyperplasia with hepatobiliary phase gadoxetic acid–enhanced MR imaging is high, a significant proportion of inflammatory hepatocellular adenomas demonstrate iso- or hyperintensity in the hepatobiliary phase.

Diagnosis of Sarcomatoid Renal Cell Carcinoma With CT: Evaluation by Qualitative Imaging Features and Texture Analysis.

OBJECTIVE The objective of our study was to determine whether CT findings, including texture analysis, can differentiate sarcomatoid renal cell carcinoma (RCC) from clear cell RCC. MATERIALS AND METHODS A retrospective case-control study was performed of consecutive patients with a histologic diagnosis of sarcomatoid RCC (n = 20) and clear cell RCC (n = 25) who underwent preoperative CT over a 3-year period. The CT images were independently reviewed by two blinded abdominal radiologists; they evaluated the following: tumor heterogeneity, tumor margin, calcification, intratumoral neovascularity, peritumoral neovascularity, renal sinus invasion, renal vein invasion, and adjacent organ invasion. Interobserver agreement was assessed using the Cohen kappa coefficient, and results were compared between groups using an independent Student t test and the chi-square test with a Bonferroni correction. For texture analysis, gray-level co-occurrence and run-length matrix features were extracted and compared using Mann-Whitney U tests. ROC curves for each tumor were constructed, and AUCs were calculated. RESULTS Overall, sarcomatoid RCCs were larger than clear cell RCCs, measuring 77 ± 27 mm (mean ± SD) compared with 50 ± 29 mm (p = 0.003), respectively; however, there was no difference in tumor size between the tumors that were compared using texture analysis or subjective analysis (p = 0.06 and 0.03, respectively). From the subjective analysis, only peritumoral neovascularity (readers 1 and 2: 70% and 70% sarcomatoid RCCs vs 0% and 41.6% clear cell RCCs, respectively; p = 0.001) and the size of the peritumoral vessels (p < 0.001) differed between sarcomatoid RCCs and clear cell RCCs, and interobserver agreement was fair (κ = 0.38). Other subjective imaging features did not differ between the tumors (p > 0.005). There was greater run-length nonuniformity and greater gray-level nonuniformity in sarcomatoid RCCs than in clear cell RCCs (p = 0.03 and p = 0.04, respectively). The combined textural features identified sarcomatoid RCC with an AUC of 0.81 ± 0.08 (standard error) (p < 0.0001). CONCLUSION Large tumor size, the presence of peritumoral neovascularity, and larger peritumoral vessels are features that are more commonly associated with sarcomatoid RCCs than with clear cell RCCs. Sarcomatoid RCCs are also more heterogeneous by texture analysis than clear cell RCCs.

Evaluation of the European Society of Urogenital Radiology (ESUR) PI-RADS scoring system for assessment of extra-prostatic extension in prostatic carcinoma

INTRODUCTION To evaluate extra-prostatic extension (EPE) comparing PI-RADS to non-standardized reporting. MATERIALS AND METHODS With IRB approval, 145 consecutive patients underwent radical prostatectomy (RP) and multi-parametric (T2W+DWI+DCE) MRI between 2012 and 2013. Eighty patients (66.3% with EPE) were staged without PI-RADS and 65 patients (64.6% with EPE) were staged using a 5-point PI-RADS scoring system. Studies were reported by fellowship-trained radiologists in routine clinical practice. Individual PIRADS scores were assessed using ROC to determine the score which optimized sensitivity/specificity. Diagnostic accuracy for EPE was compared with/without PI-RADS using the McNemar test. Subgroup analysis by radiologist experience was performed using Spearman correlation and chi-square. RESULTS Area under ROC curve for EPE using PI-RADS was 0.62 and optimal sensitivity/specificity was achieved with PI-RADS score ≥ 3. Compared to non-standardized reporting, sensitivity for EPE improved with PI-RADS (59.5% [49.1-68.2] vs. 24.5% [16.7-31.2]), p=0.01; with no difference in specificity (68.0% [50.5-82.6]) vs. (75.0% [60.1-87.6]), p=0.06. Overall accuracy improved with PI-RADS (62.7% [49.6-73.6] vs. 42.0% [31.7-50.7%]), p=0.006. Diagnostic accuracy was better among experienced radiologists without PI-RADS (p=0.005); however, there was no difference in accuracy by reader experience using PI-RADS (p=0.24). CONCLUSION The PI-RADS criteria for EPE improves sensitivity without reducing specificity. PI-RADS may reduce differences in accuracy by reader experience.

Does a cleansing enema improve image quality of 3T surface coil multiparametric prostate MRI

To assesses the utility of a preparatory enema in the interpretation of prostate multiparametric (MP) magnetic resonance imaging (MRI).

Canadian Heart Rhythm Society and Canadian Association of Radiologists consensus statement on magnetic resonance imaging with cardiac implantable electronic devices.

Magnetic resonance imaging (MRI) has historically been considered contraindicated for individuals with cardiac implantable electronic devices (CIEDs) such as pacemakers and implantable defibrillators. Magnetic resonance scanners produce magnetic fields that can interact negatively with the metallic components of CIEDs. However, as CIED technology has advanced, newer MRI conditional devices have been developed that are now in clinical use and these systems have had demonstrated safety in the MRI environment. Despite the supportive data of such CIED systems, physicians remain reluctant to perform MRI scanning of conditional devices. This joint statement by the Canadian Heart Rhythm Society and the Canadian Association of Radiologists describes a collaborative process by which CIED specialists and clinics can work with radiology departments and specialists to safely perform MRI in patients with MRI conditional CIED systems. The steps required for patient and scanning preparation and the roles and responsibilities of the CIED and radiology departments are outlined. We also briefly outline the risks and a process by which patients with nonconditional CIEDs might also receive MRI in highly specialized centres. This document supports MRI in patients with MRI conditional CIEDs and offers recommendations on how this can be implemented safely and effectively.

Comparison of Contrast-Enhanced Multiphase Renal Protocol CT Versus MRI for Diagnosis of Papillary Renal Cell Carcinoma

OBJECTIVE The objective of this study was to compare contrast-enhanced (CE) CT with MRI for the diagnosis of papillary renal cell carcinoma (pRCC). MATERIALS AND METHODS Between 2006 and 2013, a total of 27 pRCCs were assessed using CECT or CE-MRI. A blinded radiologist placed ROIs that measured attenuation on unenhanced CT; corticomedullary and nephrographic phase CECT images, with an attenuation difference of 20 HU or more denoting enhancing lesions, 10-19 HU indicating indeterminate findings, and less than 10 HU denoting nonenhancing lesions. MRI enhancement ratios were calculated as follows: (signal intensity on gadolinium-enhanced image minus signal intensity) / (signal intensity on unenhanced image × 100) for phase 1 (acquired at 30 s), phase 2 (acquired at 70 s), and phase 3 (acquired at 180 s), where a difference of 15% or more denoted enhancement. Two additional blinded radiologists qualitatively assessed tumor margin, homogeneity, and calcification with the use of CT, and they also assessed enhancement with the use of subtraction MRI. A fourth radiologist established consensus. Twenty consecutive hemorrhagic/proteinaceous cysts served as a control group. Statistical analyses were performed using a chi-square test and multivariate regression. RESULTS There was no statistically significant difference in patient age (p = 0.22), patient sex (p = 0.36), or tumor size (p = 0.29), when pRCCs were compared with hemorrhagic/proteinaceous cysts. On unenhanced CT, attenuation of pRCCs (mean ± SD, 35.7 ± 12.9 HU; range, 19-66 HU) was similar to that of hemorrhagic/proteinaceous cysts (mean, 38.9 ± 16.9; range, 8-71 HU) (p = 0.48). A total of 51.9% of pRCCs (14/27) had either absent or indeterminate enhancement on corticomedullary phase CECT images (mean attenuation difference, 23.2 ± 20.3 HU; range, 6-105 HU), and 14.8% of pRCCs (4/27) had indeterminate enhancement on nephrographic phase CECT images (mean attenuation difference, 36.4 ± 24.9; range, 10-128 HU). No pRCC was nonenhancing on nephrographic phase CECT. Qualitatively, pRCCs were more heterogeneous (80% vs 45%; p = 0.02; κ = 0.24), irregular (50% vs 5%; p < 0.001; κ = 0.21), and calcified (25% vs 0%; p = 0.004; κ = 0.67), with overlap existing between hemorrhagic/proteinaceous cysts. On CE-MRI, all pRCCs were quantitatively enhanced by phase 2 (95.4 ± 83.1; percentage change in signal intensity ratio, 16-450%) and qualitatively enhanced after consensus review. No hemorrhagic/proteinaceous cyst enhanced on MRI when quantitative or subjective analysis was performed. CONCLUSION A small number of pRCCs have indeterminate enhancement when renal protocol CT is used. Heterogeneity, irregular margins, and calcification are suggestive diagnostic features; however, quantitative and qualitative CE-MRI can accurately differentiate hemorrhagic/proteinaceous cysts from pRCC.

Pitfalls of adrenal imaging with chemical shift MRI

Chemical shift (CS) MRI of the adrenal glands exploits the different precessional frequencies of fat and water protons to differentiate the intracytoplasmic lipid-containing adrenal adenoma from other adrenal lesions. The purpose of this review is to illustrate both technical and interpretive pitfalls of adrenal imaging with CS MRI and emphasize the importance of adherence to strict technical specifications and errors that may occur when other imaging features and clinical factors are not incorporated into the diagnosis. When performed properly, the specificity of CS MRI for the diagnosis of adrenal adenoma is over 90%. Sampling the in-phase and opposed-phase echoes in the correct order and during the same breath-hold are essential requirements, and using the first echo pair is preferred, if possible. CS MRI characterizes more adrenal adenomas then unenhanced CT but may be non-diagnostic in a proportion of lipid-poor adenomas; CT washout studies may be able to diagnose these lipid-poor adenomas. Other primary and secondary adrenal tumours and supra-renal disease entities may contain lipid or gross fat and mimic adenoma or myelolipoma. Heterogeneity within an adrenal lesion that contains intracytoplasmic lipid could be due to myelolipoma, lipomatous metaplasia of adenoma, or collision tumour. Correlation with previous imaging, other imaging features, clinical history, and laboratory investigations can minimize interpretive errors.

Parenteral ferumoxytol interaction with magnetic resonance imaging: a case report, review of the literature and advisory warning

Background:Ferumoxytol is a safe and effective parenteral therapy used for the treatment of iron deficiency anaemia that has recently been approved for use in North America and in Europe.Methods:Ferumoxytol consists of a superparamagnetic iron oxide (SPIO) core, which causes T1, T2 and T2* shortening effects, and a carbohydrate shell, which results in a prolonged intravascular half life.Results:These properties are under-reported and not well recognised. They can interfere with MRI interpretation, potentially masking enhancement and rendering examinations non-diagnostic or simulating pathologic disease states. Both radiologists and non-radiologist physicians must consider the potential interaction of ferumoxytol with MRI when interpreting and prescribing MRI examinations in their patients.Main Messages• Ferumoxytol has recently been approved for the treatment of iron deficiency anaemia.• Ferumoxytol is a small iron oxide particle with prolonged intravascular half life and T1, T2 and T2* shortening effects.• Administration of ferumoxytol can mask enhancement, rendering MRI studies potentially non-diagnostic.• Ferumoxytol can mimic diseases such as haemosiderosis, haemochromatosis and superficial siderosis.• Ferumoxytol interactions with MRI must be recognised by radiologists and non-radiologist physicians.