Computed tomography liver volumetry using 3-dimensional image data in living donor liver transplantation: effects of the slice thickness on the volume calculation.

The purpose of this study was to evaluate the relationship between the slice thickness and the calculated volume in computed tomography (CT) liver volumetry through the comparison of the results from images [including 3-dimensional (3D) images] with various slice thicknesses. Twenty potential adult liver donors (12 men and 8 women) with a mean age of 39 years (range = 24-64 years) underwent CT with a 64-section multidetector row CT scanner after the intravenous injection of a contrast material. Four image sets with slice thicknesses of 0.625, 2.5, 5, and 10 mm were used. First, a program developed in our laboratory for automated liver extraction was applied to the CT images, and the liver boundaries were determined automatically. Then, an abdominal radiologist reviewed all images onto which automatically extracted boundaries had been superimposed and then edited the boundaries on each slice to enhance the accuracy. The liver volumes were determined via the counting of the voxels within the liver boundaries. The mean whole liver volumes estimated with CT were 1322.5 cm(3) from 0.625-mm images, 1313.3 cm(3) from 2.5-mm images, 1310.3 cm(3) from 5-mm images, and 1268.2 cm(3) from 10-mm images. The volumes calculated from 3D (0.625-mm) images were significantly larger than the volumes calculated from thicker images (P < 0.001). The partial liver volumes of right lobes, left lobes, and lateral segments were evaluated in a similar manner. The estimated maximum difference in the calculated volumes of lateral segments was -10.9 cm(3) (-4.63%) between 0.625- and 5-mm images. In conclusion, liver volumes calculated from 2.5-mm-thick or thicker images are significantly smaller than liver volumes calculated from 3D images. If a maximum error of 5% in the calculated graft volume will not have a significant clinical impact, 5-mm-thick images are acceptable for CT volumetry. If the impact is significant, 3D images could be essential.

Quantitative radiology: automated CT liver volumetry compared with interactive volumetry and manual volumetry.

OBJECTIVE: The purpose of this study was to evaluate automated CT volumetry in the assessment of living-donor livers for transplant and to compare this technique with software-aided interactive volumetry and manual volumetry. MATERIALS AND METHODS: Hepatic CT scans of 18 consecutively registered prospective liver donors were obtained under a liver transplant protocol. Automated liver volumetry was developed on the basis of 3D active-contour segmentation. To establish reference standard liver volumes, a radiologist manually traced the contour of the liver on each CT slice. We compared the results obtained with automated and interactive volumetry with those obtained with the reference standard for this study, manual volumetry. RESULTS: The average interactive liver volume was 1553 ± 343 cm(3), and the average automated liver volume was 1520 ± 378 cm(3). The average manual volume was 1486 ± 343 cm(3). Both interactive and automated volumetric results had excellent agreement with manual volumetric results (intraclass correlation coefficients, 0.96 and 0.94). The average user time for automated volumetry was 0.57 ± 0.06 min/case, whereas those for interactive and manual volumetry were 27.3 ± 4.6 and 39.4 ± 5.5 min/case, the difference being statistically significant (p < 0.05). CONCLUSION: Both interactive and automated volumetry are accurate for measuring liver volume with CT, but automated volumetry is substantially more efficient.

Contrast enhancement of hepatic hemangiomas on multiphase MDCT: Can we diagnose hepatic hemangiomas by comparing enhancement with blood pool?

OBJECTIVE: The purpose of this article is to determine whether enhancement of nodular foci within hemangiomas is homogeneous and matches blood vessels at different phases on contrast-enhanced MDCT. MATERIALS AND METHODS: Multiphase (unenhanced, arterial, portal venous, and delayed phases) MDCT images of 58 hemangiomas were reviewed by two radiologists. Nodular-enhancing foci within hemangiomas were evaluated for enhancement pattern and were subjectively compared with enhancement of the aorta, inferior vena cava, hepatic vein, and portal vein for each contrast-enhanced phase. Both readers measured CT attenuation of enhancing nodules and vessels at each phase, and enhancement of nodules and vessels was compared. RESULTS: Qualitative analysis showed heterogeneously enhancing nodules in 79.3% and 65.5% of hemangiomas in the arterial phase and in 74.1% and 53.4% of hemangiomas in the portal venous phase, according to readers 1 and 2, respectively. In the arterial phase, 3.8% and 12.3% of nodules showed enhancement similar to that in the aorta. In the portal venous phase, 15.4% and 21.7%, 16.8% and 18.2%, 14.1% and 23.8%, and 19.5% and 25.9% of nodules were scored with enhancement similar to that in the aorta, inferior vena cava, hepatic vein, and portal vein by readers 1 and 2, respectively. Differences between attenuation of nodules and all vessels in the arterial, portal venous, and delayed phases were statistically significant. Statistically significant differences were also noted between attenuation among blood vessels in the arterial and portal venous phases but not in the delayed phase. CONCLUSION: Attenuation of enhancing foci within hemangiomas does not match vessel density qualitatively or quantitatively. No common blood pool density exists in the arterial or portal venous phase. Although persistent enhancement without washout is a useful CT criterion, specific criteria to match the blood pool cannot be used to confirm a diagnosis of hemangioma.

Diffusion-weighted MRI: a new tool for the diagnosis of fistula in ano.

PURPOSE: To retrospectively determine the additional value of diffusion-weighted magnetic resonance imaging (MRI) to T2-weighted imaging in the evaluation of anal fistulae in comparison with gadolinium (Gd)-enhanced imaging. MATERIALS AND METHODS: Thirteen patients (mean age, 35.2 years) with 20 anal fistulae were included. The protocol consisted of fat-suppressed T2-weighted fast spin-echo, diffusion-weighted single-shot echo-planar (b factors 0 and 800 s/mm(2)), and fat-suppressed Gd-enhanced T1-weighted gradient echo sequences. Two radiologists evaluated images in consensus. RESULTS: Eighteen (90%) fistulae were detected on T2-weighted images, and 19 (95%) and 19 (95%) were detected on diffusion-weighted and T2-weighted images combined and on Gd-enhanced and T2-weighted images combined, respectively. There was no statistically significant difference in sensitivity of the techniques (P > 0.5 for all comparison pairs). Confidence scores with diffusion-weighted and T2-weighted images combined or those with Gd-enhanced and T2-weighted images combined were significantly greater than those with T2-weighted images alone (P = 0.0047 and 0.014, respectively). CONCLUSION: Diffusion-weighted MRI of anal fistulae is a useful sequence and can be a helpful adjunct to T2-weighted imaging, especially in patients with risk factors for contrast agents.

Focal confluent fibrosis in cirrhotic liver: natural history studied with serial CT.

OBJECTIVE: The objective of this study was to assess the long-term natural history of focal confluent fibrosis in cirrhotic liver with CT. MATERIALS AND METHODS: Two radiologists retrospectively reviewed in consensus 118 liver CT examinations in 26 patients (19 men, seven women; age range, 32-68 years; mean age, 50 years) performed over approximately 6 years. Helical CT scans were obtained before and 30-35 and 65-70 seconds after injection of 125-150 mL of contrast medium at a rate of 4-5 mL/s. Proof of cirrhosis was based on liver transplantation (n = 6), biopsy (n = 9), or imaging findings (n = 11). The number, location, and attenuation of fibrotic lesions and presence of trapped vessels were evaluated. Variation of hepatic retraction associated with the development of focal confluent fibrosis lesions was assessed using the ellipsoid volume formula and an arbitrary retraction index. RESULTS: Each radiologist identified 41 focal confluent fibrosis lesions. All lesions were identified by both radiologists. Twelve patients (46%) had a single lesion, 13 (50%) had two lesions, and one (4%) had three lesions. Thirty-four (83%) of 41 lesions were located in segment IV, VII, or VIII. Thirty-two lesions (78%) were hypoattenuating on unenhanced images, 25 lesions (61%) were hypoattenuating on hepatic arterial phase images, and 20 lesions (49%) were isoattenuating on portal venous phase images. Seven lesions (17%) were or became hyperattenuating at follow-up on portal venous phase images. Trapped vessels were found in six lesions (15%). The retraction index showed a significant increase over time (r = 0.423, p < or = 0.0001). CONCLUSION: The degree of capsule retraction associated with focal confluent fibrosis evolves with time and relates to the natural evolution of cirrhosis.

Single, aligned carbon nanotubes in 3D nanoscale architectures enabled by top-down and bottom-up manufacturable processes.

We have developed manufacturable approaches for forming single, vertically aligned carbon nanotubes, where the tubes are centered precisely, and placed within a few hundred nm of 1-1.5 microm deep trenches. These wafer-scale approaches were enabled by using chemically amplified resists and high density, low pressure plasma etching techniques to form the 3D nanoscale architectures. The tube growth was performed using dc plasma-enhanced chemical vapor deposition (PECVD), and the materials used in the pre-fabricated 3D architectures were chemically and structurally compatible with the high temperature (700 degrees C) PECVD synthesis of our tubes, in an ammonia and acetylene ambient. Such scalable, high throughput top-down fabrication processes, when integrated with the bottom-up tube synthesis techniques, should accelerate the development of plasma grown tubes for a wide variety of applications in electronics, such as nanoelectromechanical systems, interconnects, field emitters and sensors. Tube characteristics were also engineered to some extent, by adjusting the Ni catalyst thickness, as well as the pressure and plasma power during growth.

Imaging the spectrum of biliary tract disease.

An understanding of underlying biliary pathology and the corresponding subtle changes reflected at imaging can greatly improve imaging accuracy in evaluating the biliary tract. The optimal demonstration of biliary tract imaging findings requires attention to specific imaging and contrast techniques, regardless of the modality used.

Balancing the three missions and the impact on academic radiology.

The three missions of academic radiology compete with one another for time and funding. Revenue for the clinical mission often subsidizes education and research. Given the internal and external drivers/pressures on health care and, more particularly, on academic health centers, the current model is unsustainable. Trends seen in other industries are entering academic health care. The radiology department of the future will need to be more efficient with increasingly fewer resources while meeting its missions at higher levels of expectation.

Arterially enhancing liver lesions: significance of sustained enhancement on hepatic venous and delayed phase with magnetic resonance imaging.

Benign hepatic vascular neoplasms and vascular pseudolesions are commonly encountered in magnetic resonance (MR) imaging. Most of these benign lesions demonstrate not only arterial-phase hyperintensity, but also persistent enhancement on venous and delayed imaging, unlike most malignant hepatic masses. These features, along with other MR findings and morphological characteristics, may allow for more confident diagnosis and distinction from hepatic malignancy. The objective of our study was to illustrate the MR imaging findings of hepatic lesions that demonstrate both early arterial and sustained enhancement on hepatic venous and delayed phase.

Computed tomographic imaging of hepatocellular carcinoma.

The ability of x-ray computed tomography (CT) to detect and characterize liver lesions has been one of the most studied issues in radiology during the past 20 years. Technological advances, combined with increased knowledge about the pathophysiological characteristics of these tumors, have dramatically increased the ability to detect and characterize large hepatocellular carcinomas (HCCs). Nonetheless, detection and characterization of early and small HCC lesions remains a difficult task. We review the imaging appearances of HCC on CT and discuss the sensitivity and specificity of computed tomographic imaging in screening patients with cirrhosis for HCC.

Helical CT screening for hepatocellular carcinoma in patients with cirrhosis: frequency and causes of false-positive interpretation.

OBJECTIVE: The purpose of our study was to determine the specificity of helical CT for depiction of hepatocellular carcinoma in a population of patients with cirrhosis. SUBJECTS AND METHODS: Single-detector helical CT screening was undertaken in 1329 patients with cirrhosis who were referred for transplantation. The patients underwent one or more helical CT examinations over 30 months and were followed up for an additional 19 months or until transplantation. We predominantly used unenhanced and biphasic contrast-enhanced techniques with infusions of 2.5-5.0 mL/sec. Four hundred thirty patients underwent transplantation within this period. Liver specimens were sectioned at 1-cm intervals, with direct comparison of imaging and pathologic findings and histologic confirmations of all lesions. Prospective preoperative helical CT reports were used for the primary data analysis. A retrospective unblinded review was undertaken to determine characteristics of false-positive lesions diagnosed as hepatocellular carcinoma. RESULTS: Thirty-five patients (8%) had false-positive diagnoses for hepatocellular carcinoma based on helical CT. Twenty of these patients (5%) showed hypoattenuating lesions seen during one of the three helical CT examination phases. Fifteen patients (3%) had hyperattenuating lesions seen during the arterial phase. Among the 15 hyperattenuating lesions, CT revealed the causes to be transient benign hepatic enhancement (n = 3), hemangiomas (n = 2), fibrosis (n = 2), peliosis (n = 1), volume averaging (n = 1), low-grade dysplastic nodule (n = 1), or undetermined (n = 5). Of the 20 hypoattenuating lesions, the causes were shown to be fibrosis (n = 8), focal fat (n = 4), infarcted regenerative nodules (n = 2), regenerative nodules (n = 1), fluid trapped at the dome of the liver (n = 1), hemangioma (n = 1), or undetermined (n = 3). Follow-up helical CT in 13 (72%) of 18 patients allowed a change in the diagnosis of hepatocellular carcinoma to a finding of no cancer present. CONCLUSION: Helical CT screening for hepatocellular carcinoma in patients with cirrhosis has a substantial false-positive detection rate. Although most of lesions were hypoattenuating, a few hyperenhancing arterial phase lesions were proven not to be hepatocellular carcinoma. An awareness of imaging characteristics and follow-up imaging can help radiologists avoid a mistaken diagnosis in many patients.

Intrahepatic biliary anatomy of living adult liver donors: correlation of mangafodipir trisodium-enhanced MR cholangiography and intraoperative cholangiography.

OBJECTIVE: The purpose of our study was to assess the usefulness of mangafodipir trisodium-enhanced MR cholangiography for evaluating intrahepatic biliary anatomy of adult living liver donors and to correlate the results with intraoperative cholangiography. CONCLUSION: Mangafodipir trisodium-enhanced MR cholangiography accurately shows the biliary anatomy in the livers of donors. Noninvasive preoperative evaluation of the biliary anatomy in donor candidates is important for the detection of common anatomic variants that may require alternative graft-harvesting surgery.