Hussain, S.M.

Liver imaging at 3.0 T: Diffusion-induced black-blood echo-planar imaging with large anatomic volumetric coverage as an alternative for specific absorption rate-intensive echo-train spin-echo sequences: Feasibility study (Article)

2008-07-01T00:00:00Z

Institutional Review Board approval and signed informed consent were obtained by all participants for an ongoing sequence optimization project at 3.0 T. The purpose of this study was to evaluate breath-hold diffusion-induced blackblood echo-planar imaging (BBEPI) as a potential alternative for specific absorption rate (SAR)-intensive spin-echo sequences, in particular, the fast spin-echo (FSE) sequences, at 3.0 T. Fourteen healthy volunteers (seven men, seven women; mean age ± standard deviation, 32.7 years ± 6.8) were imaged for this purpose. Liver coverage (20 cm, z-axis) was always performed in one 25-second breath hold. Imaging parameters were varied interactively with regard to echo time, diffusion b value, and voxel size. Images were evaluated and compared with fat-suppressed T2-weighted FSE images for image quality, liver delineation, geometric distortions, fat suppression, suppression of the blood signal, contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR). An optimized short- (25 msec) and long-echo (80 msec) BBEPI provided full anatomic, single breath-hold liver coverage (100 and 50 sections, respectively), with resulting voxel sizes of 3.3 x 2.7 x 2.0 mm and 3.3 x 2.7 x 4.0 mm, respectively. Repetition time was 6300 msec, matrix size was 160 x 192, and an acceleration factor of 2.00 was used. b Values of more than 20 sec/mm2showed better suppression of the blood signal but b values of 10 sec/mm2provided improved volume coverage and signal consistency. Compared with fat-suppressed T2-weighted FSE, the optimized BBEPI sequence provided (a) comparable image quality and liver delineation, (b) acceptable geometric distortions, (c) improved suppression of fat and blood signals, and (d) high CNR and SNR. BBEPI is feasible for fast, low-SAR, thin-section morphologic imaging of the entire liver in a single breath hold at 3.0 T.

Magnetic Resonance Imaging of Liver Lesions: Exceptions and Atypical Lesions (Article)

2008-05-01T00:00:00Z

On state-of-the-art magnetic resonance imaging, most lesions can be detected and characterized with confidence according to well-known criteria. However, atypical characteristics in some common lesions and the incidental encounter with rare lesions may pose diagnostic difficulties. In this article, six challenging hepatic lesions will be discussed and evaluated on the most important magnetic resonance imaging sequences, with histological correlation when available. In addition, the background information concerning these lesions will be described based on the most recent available literature. By reading this article, the reader will be able to (1) categorize the lesion in solid and fluid-containing lesions, based on the T2 signal intensity; and (2) define the benign or malignant nature of the lesion, in relation to the signal intensity and dynamic enhancement pattern, despite the presence of atypical characteristics of some lesions.

Primary Hepatocellular Lesions: Imaging Findings on State-of-the-Art Magnetic Resonance Imaging, with Pathologic Correlation (Article)

2008-05-01T00:00:00Z

Magnetic resonance imaging is routinely used for the workup of patients with focal or diffuse liver disease, including primary hepatocellular lesions, storage diseases, metastatic liver disease, and diseases of the hepatobiliary tree. The most important magnetic resonance imaging sequences used for diagnostic imaging of the liver consist of T1-weighted sequences, T2-weighted sequences, and at least the arterial and delayed phases of dynamic gadolinium-enhanced imaging. This article provides an overview of magnetic resonance imaging of primary hepatocellular lesions and will describe the following: (1) the classification and etiology of primary hepatocellular lesions, including focal nodular hyperplasia, hepatocellular adenoma, and hepatocellular carcinoma; (2) the stepwise carcinogenesis of hepatocellular carcinoma in cirrhosis on magnetic resonance imaging; and (3) the typical imaging findings of primary hepatocellular lesions on magnetic resonance imaging, with differential diagnoses.

Hepatocellular carcinoma complicating biliary atresia after Kasai portoenterostomy (Article)

2008-03-01T00:00:00Z

Kasai portoenterostomy (PE) increases the survival for children with biliary atresia (BA) and consequently postpones subsequential liver transplantation. All long-term survivors, however, develop complications of biliary cirrhosis. We report a case of hepatocellular carcinoma (HCC) in a 19-year-old male patient with BA and Kasai PE. The preoperative abdominal ultrasound and magnetic resonance imaging showed a large hepatic mass (diameter 10 cm). The serum α-fetoprotein level was within normal range. Pathologic findings of the mass, after orthotopic liver transplantation, demonstrated a well-differentiated HCC (T1N0M0). HCC is a rare complication of BA, but will intensively impair the survival. Therefore, clinicians should be alert to the development of HCC in this very young patient group. Repeated sequential magnetic resonance imaging of the native liver in patients with Kasai PE is necessary to monitor possible malignant transformation of liver nodules that may potentially develop as a result of chronic cholestatic liver disease.

Extending slice coverage for breathhold fat-suppressed T2-weighted fast spin-echo of the liver at 3.0T: Application of Variable-Rate Selective-Excitation (VERSE) RF pulses (Article)

2008-01-01T00:00:00Z

Purpose: To determine the benefits of variable-rate selective-excitation (VERSE) radio frequency (RF) pulses for increased slice coverage in breathhold (BH) fat-suppressed T2-weighted fast spin-echo (FS-T2W-FSE) liver imaging at 3.0T. Materials and Methods: A total of 12 healthy volunteers were imaged on 3.0T, using FS-T2W-FSE. Slice coverage and specific absorption rate (SAR) levels were monitored for VERSE-RF and standard-RF (sRF), respectively. BH time was 25 seconds; slice thickness 3.5 mm. Maximum coverage was recorded for interactive variation of repetition time (TR), bandwidth (BW), and echo-train length (ETL). Image quality was assessed qualitatively and quantitatively. Results: Total slice coverage was always higher using VERSE-RF, but varied depending on the selected parameters. For BW ≥ 62.5 kHz, slice coverage using VERSE increased between 38% (TR = 8200 msec) and 58% (TR = 2500 msec). Maximum coverage was obtained for TR = 5000 msec, ETL = 12, and BW ≥ 62.5 kHz; with a mean of 31.8 slices for VERSE-RF and 22.5 slices for sRF, respectively (P < 0.005, 41% increased coverage). SAR was lower for VERSE-RF using BW < 41.67 kHz (P < 0.05), and equal to sRF for higher BW. Image quality was best for TR ≤ 5000 msec (P < 0.05). FS was more homogeneous for lower ETL (P < 0.05). Blood suppression was best for TR ≤ 5000 msec (P < 0.05). Conclusion: VERSE-RF pulses can be applied for thin-slice BH FS-T2W liver imaging at 3.0T, with significantly improved slice coverage.

MR imaging of hepatocellular carcinoma: Relationship between lesion size and imaging findings, including signal intensity and dynamic enhancement patterns (Article)

2007-12-01T00:00:00Z

Purpose: To assess the relationship between lesion size and MR imaging findings of pathologically-proven hepatocellular carcinoma (HCC). Materials and Methods: In a retrospective, single-center study, 37 consecutive patients were identified between 1999 and 2005 that underwent preoperative MRI and surgical resection of HCC. A total of 47 lesions (mean size = 6.85 cm, range = 1-25 cm) were assessed for signal intensity (SI), enhancement patterns, and secondary morphologic features. Interobserver rating, percentage enhancement, and contrast-to-noise-ratio (CNR) were determined. Lesions were assessed for combinations of typical MRI features. Regression analysis was used to assess relations between MRI findings and tumor size. Results: On fat-suppressed T2-weighted (T2w) fast-spinecho, smaller lesions had lower SI compared to larger lesions (P < 0.05). In the arterial phase, smaller lesions showed significantly higher percentage enhancement compared to larger lesions (P < 0.05). In the delayed phase, smaller lesions showed less pronounced washout (P < 0.05). Heterogeneity of the lesions, including fatty infiltration, internal nodules, or mosaic pattern, was observed significantly more frequently in larger lesions (P < 0.001). The classic combination of high T2w signal, strong arterial enhancement, and delayed phase washout was present in 23 of 44 lesions (52%). Conclusion: Smaller HCC often showed lower SI on T2w, more intense arterial enhancement, and less pronounced delayed washout compared to larger HCC.

Anovaginal fistulas: evaluation with endoanal MR imaging. (Article)

2004-04-01T00:00:00Z

PURPOSE: To evaluate endoanal magnetic resonance (MR) imaging in the assessment of anovaginal fistulas and associated findings. MATERIALS AND METHODS: In a retrospective descriptive study, two radiologists systematically reviewed MR findings in 20 patients with a clinically proved anovaginal fistula and looked for the main fistula tract, the internal opening in the anal canal and/or vagina, secondary fistula tracts, abscesses within the rectovaginal septum, and sphincter damage. Interobserver variability was calculated, and clinical records were searched for possible underlying causes that could explain the complexity of anovaginal fistulas. The kappa value was calculated. Patients with or without a complex anovaginal fistula were compared in regard to the presence of any underlying disease or condition. Statistical significance was calculated with the Fisher exact test. RESULTS: In all 20 patients, anovaginal fistulas were identified on T2-weighted MR images as predominantly high-signal-intensity linear abnormalities extending between the anal canal and the vagina. In all patients, the fistulas were typically located in the sagittal plane, and the mean distance from the anal verge to the fistula was 25.0 mm (range, 13-32 mm). The internal opening in the anal canal was detected in all patients. The internal opening in the vagina was detected in 19 (95%) patients. In seven (35%) patients, an anovaginal fistula with an additional abnormality was found and included an abscess within the rectovaginal septum (n = 1), a perianal fistula (n = 3), and a perianal fistula in combination with an abscess (n = 3). Defects of the external anal sphincter were present in three (15%) patients. There was complete agreement between observers for all items on endoanal MR images, except for the presence of secondary fistula extensions (agreement, 90%; kappa, 0.74). History of obstetric trauma, pelvic floor surgery, or Crohn disease was present in 10 (50%) patients. Of these patients, six (60%) had a complex anovaginal fistula and four (40%) had a simple anovaginal fistula. In the remaining 10 patients without relevant medical history, one (10%) had a complex anovaginal fistula. This difference tended toward statistical significance (P =.057). CONCLUSION: Endoanal MR imaging allows evaluation of anovaginal fistulas and additional abnormalities, such as abscesses within the rectovaginal septum, secondary perianal fistula tracts, and sphincter damage.

Focal nodular hyperplasia: findings at state-of-the-art MR imaging, US, CT, and pathologic analysis. (Article)

2004-01-01T00:00:00Z

Focal nodular hyperplasia (FNH) is the second most common benign liver tumor after hemangioma. FNH is classified into two types: classic (80% of cases) and nonclassic (20%). Distinction between FNH and other hypervascular liver lesions such as hepatocellular adenoma, hepatocellular carcinoma, and hypervascular metastases is critical to ensure proper treatment. An asymptomatic patient with FNH does not require biopsy or surgery. Magnetic resonance (MR) imaging has higher sensitivity and specificity for FNH than does ultrasonography or computed tomography. Typically, FNH is iso- or hypointense on T1-weighted images, is slightly hyper- or isointense on T2-weighted images, and has a hyperintense central scar on T2-weighted images. FNH demonstrates intense homogeneous enhancement during the arterial phase of gadolinium-enhanced imaging and enhancement of the central scar during later phases. Familiarity with the proper MR imaging technique and the spectrum of MR imaging findings is essential for correct diagnosis of FNH.

MR imaging: a 'One Stop Shop' Modality for Preoperative Evaluation of Potential Living Kidney-Donors (Article)

2003-01-01T00:00:00Z

At many institutions, magnetic resonance (MR) angiography is the technique of choice for assessment of the renal arteries and renal parenchyma in potential living kidney donors. The renal arteries and renal veins have a varied anatomy and may consist of one or more vessels at several levels with variable calibers and levels of branching. These findings may play an important role in the surgeon's decision about which kidney to harvest, especially if laparoscopic nephrectomy is used. A comprehensive MR imaging protocol is used at one hospital to assess the arteries, veins, parenchyma, and collecting system of the kidneys. The protocol includes T2-weighted single-shot fast spin-echo imaging, fat-saturated T2-weighted fast spin-echo imaging, three-dimensional MR angiography and MR venography, and delayed fat-saturated three-dimensional T1-weighted gradient-echo imaging. Meticulous assessment of the source images as well as images produced with various postprocessing methods, such as full maximum intensity projection, targeted maximum intensity projection, and axial and oblique reformation, allows detailed description of the vascular anatomy and its relationship to the collecting system and parenchyma to facilitate the surgeon's decision making. The findings of MR imaging are comparable with those of other imaging modalities.

Benign versus malignant hepatic nodules: MR imaging findings with pathologic correlation (Article)

2002-01-01T00:00:00Z

According to the currently used nomenclature, there are only two types of hepatocellular nodular lesions: regenerative lesions and dysplastic or neoplastic lesions. Regenerative nodules include monoacinar regenerative nodules, multiacinar regenerative nodules, cirrhotic nodules, segmental or lobar hyperplasia, and focal nodular hyperplasia. Dysplastic or neoplastic nodules include hepatocellular adenoma, dysplastic foci, dysplastic nodules, and hepatocellular carcinoma (HCC). Many of these types of hepatic nodules play a role in the de novo and stepwise carcinogenesis of HCC, which comprises the following steps: regenerative nodule, low-grade dysplastic nodule, high-grade dysplastic nodule, small HCC, and large HCC. State-of-the-art magnetic resonance (MR) imaging facilitates detection and characterization in most cases of hepatic nodules. State-of-the-art MR imaging includes single-shot fast spin-echo imaging, in-phase and opposed-phase T1-weighted gradient-echo imaging, T2-weighted fast spin-echo imaging with fat saturation, and two-dimensional or three-dimensional dynamic multiphase contrast material-enhanced imaging.

Imaging of the anal sphincter complex (Doctoral Thesis)

1996-06-05T00:00:00Z

Endoanal MRI of the anal sphincter complex: correlation with cross-sectional anatomy and histology (Article)

1996-01-01T00:00:00Z

The purpose of this study was to correlate the in vivo endoanal MRI findings of the anal sphincter with the cross-sectional anatomy and histology. Fourteen patients with rectal tumours were examined with a rigid endoanal MR coil before undergoing abdominoperineal resection. In addition, 12 cadavers were used to obtain cross-sectional anatomical sections. The images were correlated with the histology and anatomy of the resected rectal specimens as well as with the cross-sectional anatomical sections of the 12 cadavers. The findings in 8 patients, 11 rectal preparations, and 10 cadavers, could be compared. In these cases, there was an excellent correlation between endoanal MRI and the cross-sectional cadaver anatomy and histology. With endoanal MRI, all muscle layers of the anal canal wall, comprising the internal anal sphincter, longitudinal muscle, the external anal sphincter and the puborectalis muscle were clearly visible. The levator ani muscle and ligamentous attachments were also well demonstrated. The perianal anatomical spaces, containing multiple septae, were clearly visible. In conclusion, endoanal MRI is excellent for visualising the anal sphincter complex and the findings show a good correlation with the cross-sectional anatomy and histology.