Virtual histology-intravascular ultrasound as a diagnostic alternative for morphological characterization of carotid plaque: comparison with histology and high-resolution magnetic resonance findings.

BACKGROUND: Stroke is the third most common cause of death and one of the most common cause of long-term disability in the Western world. Carotid plaque morphology is the main predictor of cerebrovascular accidents, more than the degree of stenosis. AIMS: The primary aim was to validate virtual histology- intravascular ultrasound (VH-IVUS) as a diagnostic tool for carotid plaque characterization, by comparison with histology, through ex-vivo evaluation of carotid plaques. The secondary target was to compare VH-IVUS with high-resolution MRI (HR-MRI) through in-vivo evaluation of carotid artery plaques. MATERIALS AND METHODS: In the ex-vivo study, data were acquired from six carotid arteries explanted from six symptomatic male patients with a mean age of 72 W 9.64 years. Sectional images obtained with the IVUS catheter were compared with digitalized histological images. Twelve consecutive patients (eight men, four women, mean age of 75 W 6.33 years), candidates for carotid artery stenting, were included in the in-vivo study. All histological and HR-MR images were converted to a digital format and the exact percentages of the four plaque components were determined. RESULTS: Forty-two images were used for correlation between VH-IVUS and histology. Quantitative analysis of different plaque components revealed a good concordance (0.82) between the two methods [95% confidence interval (CI) 0.69-0.92]. Precision rates of VH-IVUS for concordance with true histology of different plaque components were 99.4% for fibrous tissue, 85.9% for fibrolipid tissue, 71.4% for calcium and 83.4% for necrosis. Comparison between HR-MRI and VH-IVUS was performed on 27 images. Concordance between the two methods was 0.84 (95% CI 0.69-0.92). Precision rates were, respectively, 85.3, 95.2, 90.2 and 82.0%. CONCLUSION: We believe that VH-IVUS may be useful when a quick intraprocedural evaluation of a carotid plaque before or after stent placement is required, but is not suitable for the accurate in-vivo differentiation between stable and unstable plaques prone to rupture, due to the suboptimal assessment of the necrotic component, fibrous cap thickness and rupture signs. We do believe, however, that these results need further evaluation in larger populations to be confirmed.

What is a reliable CT scan for diagnosing splenosis under emergency conditions?

Splenosis is a condition in which splenic tissue is present in a non-anatomical position. Implants of splenic tissue can mimic neoplasms and only specific examinations can confirm the correct diagnosis. Here we report a case of a 23-year-old male patient with a history of surgical splenectomy during childhood after trauma. He was admitted to the emergency department with acute bowel obstruction. An abdominal-pelvic computed tomography (CT) scan revealed small bowel obstruction and the presence of two rounded, solid masses located in the rectal-vescical pouch. Quantitative analyses of the different density values in the arterial phase and early portal venous phase demonstrated that these lesions were highly vascularised (92 and 97 Hounsfield Units, respectively). The hypothesis of an ectopic splenic mass was made after evaluation of the CT images and clinical history. The acute bowel obstruction caused by adhesive intestinal syndrome was resolved by surgical adhesiolysis. The smallest mass adherent to the rectum was removed. Histopathologic examination confirmed the benign nature of the lesion, which consisted of splenic tissue.

High-resolution multicontrast-weighted MR imaging from human carotid endarterectomy specimens to assess carotid plaque components.

The American Heart Association modified classification for atherosclerotic plaque lesions has defined vulnerable plaques as those prone to rupture. The aim of our study was to assess the sensitivity and specificity of 1.5-T magnetic resonance imaging (MRI) in the evaluation of the characteristics of plaque components. Twelve carotid endarterectomy specimens were imaged by ex-vivo high-resolution 1.5-T MRI. Thirty-four cross-section axial images were selected for pixel-by-pixel basis analysis to demonstrate the most significant tissue features. Data were then submitted for histopathological examination and each specimen analysed in the light of the histological components (lipid core, fibrous tissue, fibrous/loose connective tissue, calcifications). The overall sensitivity and specificity rates for each tissue type were, respectively, 92% and 74% for the lipid core, 82% and 94% for the fibrous tissue, 72% and 87% for the fibrous/loose connective tissue, and 98% and 99% for calcification. The use of 1.5-T MRI appears to be a reliable tool to characterise plaque components and could help in the screening of patients with high risk of plaque rupture. The possibility of applying MRI in clinical daily practice may change the non-invasive approach to carotid artery diagnostic imaging, thus allowing an early identification of patients with vulnerable plaques.

Staging of colon cancer: whole-body MRI vs. whole-body PET-CT--initial clinical experience.

BACKGROUND: To assess the accuracy of whole-body MR imaging (WB-MRI) in comparison with whole-body [18(F)]-2-fluoro-2-deoxy-D-glucose (FDG) PET-CT in staging patients with diagnosed colorectal carcinoma (CRC). METHODS: Twenty consecutive patients with previously diagnosed CRC underwent WB-MRI (3T) and PET-CT for staging of lymph node (N) and distant metastases (M). Evaluation was done according to the American Joint Committee on Cancer Staging Criteria. MR images were evaluated by two radiologists while PET-CT images by one radiologist and one nuclear medicine physician. Histology and/or a clinical follow-up of 3-6 months served as standard of reference. RESULTS: Lymph node involvement was determined in 10/20 cases as N-positive in WB-MRI and in 15/20 in PET-CT. M-stage was evaluated for liver metastases (27 lesions in 15 patients with WB-MRI, 23/15 patients with PET-CT), lung (19/5 patients with WB-MRI, 25/7 patients with PET-CT), and bone (9/3 patients with WB-MRI, 9/3 patients with PET-CT). Two patients showed peritoneal implants and three patients demonstrated local recurrence at the surgery site on both modalities. No brain metastases were found. CONCLUSIONS: WB-MRI is a feasible method for examining colon cancer patients but cannot displace the present role of PET-CT.

Diffusion tensor magnetic resonance imaging of prostate cancer.

PURPOSE: To explore the feasibility of 3T magnetic resonance (MR) diffusion tensor imaging (DTI) and fiber tracking (FT) in patients with prostate cancer. MATERIALS AND METHODS: Thirty consecutive patients (mean age, 62.5 years) with biopsy proven prostate cancer underwent 3T-MR imaging (MRI) and DTI using a 6-channel external phased-array coil before radical prostatectomy. Regions of interest of 14 pixels were defined in tumors and nonaffected areas in the peripheral zone (PZ) and central gland (CG), according to histopatology after radical prostatectomy. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values were determined. Differences in mean ADC and FA values among prostate cancer, normal PZ and CG were compared by 2-sided Student t test. The predominant diffusion direction of the prostate anisotropy was color coded on a directionally encoded color (DEC) map. A 3D reconstruction of fiber tract orientations of the whole prostate was determined using the continuous tracking method. The overall image quality for tumor localization and local staging was assessed in retrospective matching with whole-mount section histopathology images. Nodules detected at MRI were classified as matched lesions if tumor presence and extension were evidenced at histopathology. RESULTS: For all the patients, the DTI sequence images were suitable for the evaluation of the zonal anatomy of the prostate gland and the tumor localization. Quantitative evaluation of the regions of interest (ROIs) showed a mean ADC value significantly lower in the peripheral neoplastic area (1.06 +/- 0.37 x 10(-3) mm2/s) than in the normal peripheral portion (1.95 +/- 0.38 x 10(-3) mm2/s) (P < 0.05). The mean FA values calculated in the normal peripheral (0.47 +/- 0.04) and central area (0.41 +/- 0.08) were very similar (P > 0.05). The mean FA values in the neoplastic lesion (0.27 +/- 0.05) were significantly lower (P < 0.05) than in the normal peripheral area and in the normal central and adenomyomatous area. DEC map showed a top-bottom type preferential direction in the peripheral but not in the central area, with the tumor lesions reducing the diffusion coding direction represented as color zones tending toward gray. Tractographic analysis permitted good delineation of the prostate anatomy (capsule outline, peripheral and central area borders) and neoplastic lesion extension and capsule infiltration compared with histopathology. CONCLUSIONS: Three Tesla DTI of the prostate gland is feasible and has the potential for providing improved diagnostic information.