Non-invasive evaluation of hepatic fibrosis for type C chronic hepatitis.

OBJECTIVE: The aim of this study was to investigate liver fibrosis using non-invasive Real-time Tissue Elastography (RTE) and transient elastography (FibroScan) methods. METHODS: RTE, FibroScan and percutaneous liver biopsy were all performed on patients with chronic liver disease, particularly hepatitis C, to investigate liver fibrosis. RESULTS: FibroScan and RTE were compared for fibrous liver staging (F stage), which was pathologically classified using liver biopsy. In FibroScan, significant differences were observed between F1/F3 and F2/F4, but no such differences were observed between F1/F2, F2/F3 and F3/F4. In RTE, significant differences were observed between F1/F2, F2/F3 and F2/F4. But for F3/F4, no significant differences were observed. CONCLUSION: FibroScan and RTE correlated well with F staging of the liver. In particular RTE was more successful than FibroScan in diagnosing the degree of liver fibrosis.

Real-time Virtual Sonography for navigation during targeted prostate biopsy using magnetic resonance imaging data.

OBJECTIVES: To evaluate the effectiveness of the medical navigation technique, namely, Real-time Virtual Sonography (RVS), for targeted prostate biopsy. METHODS: Eighty-five patients with suspected prostate cancer lesions using magnetic resonance imaging (MRI) were included in this study. All selected patients had at least one negative result on the previous transrectal biopsies. The acquired MRI volume data were loaded onto a personal computer installed with RVS software, which registers the volumes between MRI and real-time ultrasound data for real-time display. The registered MRI images were displayed adjacent to the ultrasonographic sagittal image on the same computer monitor. The suspected lesions on T2-weighted images were marked with a red circle. At first suspected lesions were biopsied transperineally under real-time navigation with RVS and then followed by the conventional transrectal and transperineal biopsy under spinal anesthesia. RESULTS: The median age of the patients was 69 years (56-84 years), and the prostate-specific antigen level and prostate volume were 9.9 ng/mL (4.0-34.2) and 37.2 mL (18-141), respectively. Prostate cancer was detected in 52 patients (61%). The biopsy specimens obtained using RVS revealed 45/52 patients (87%) positive for prostate cancer. A total of 192 biopsy cores were obtained using RVS. Sixty-two of these (32%) were positive for prostate cancer, whereas conventional random biopsy revealed cancer only in 75/833 (9%) cores (P < 0.01). CONCLUSIONS: Targeted prostate biopsy with RVS is very effective to diagnose lesions detected with MRI. This technique only requires additional computer and RVS software and thus is cost-effective. Therefore, RVS-guided prostate biopsy has great potential for better management of prostate cancer patients.

Novel and Simple Ultrasonographic Methods for Estimating the Abdominal Visceral Fat Area.

OBJECTIVES: To evaluate the abdominal visceral fat area (VFA), we developed novel ultrasonographic (US) methods for estimating. METHODS: 100 male volunteers were recruited, and their VFA was calculated by two novel US methods, the triangle method and the ellipse method. The VFA calculated by these methods was compared with the VFA calculated by CT. RESULTS: Both the VFA calculated by the triangle method (r = 0.766, p < 0.001) and the ellipse method (r = 0.781, p < 0.001) showed a high correlation coefficient with the VFA calculated by CT. Also, the VFA calculated by our novel methods were significantly increased in subjects with one or more metabolic risk factors than in those without any risk factors. Furthermore, the correlation coefficients obtained using the two methods were enhanced by the addition of multiple regression analysis (with the triangle method, r = 0.8586, p < 0.001; with the ellipse method, r = 0.8642, p < 0.001). CONCLUSIONS: The VFA calculated by the triangle or ellipse method showed a high correlation coefficient with the VFA calculated by CT. These US methods are easy to use, they involve no radiation exposure, and the measurements can be conducted frequently. We hope that our simple methods would be widely adopted for the evaluation of VFA.

A single mediaprocessor-based programmable ultrasound system.

We have developed a programmable ultrasound imaging system using a single commercially available mediaprocessor. We have efficiently mapped all of the necessary B-mode processing algorithms on the underlying processor architecture, including envelope detection, dynamic range compression, lateral and axial filtering, persistence processing, and scan conversion. Our system can handle varying specifications ranging from 128 vectors and 512 samples per vector to more than 256 vectors and 1024 samples per vector. For an image size of 330 vectors and 512 samples per vector, it can process 30 frames per second using a 300-MHz MAP-CA mediaprocessor from Hitachi/Equator Technologies. This programmable ultrasound machine will not only offer significant advantages in terms of low cost, portability, scalability, and reduced development time, but also provide a flexible platform for developing and deploying new clinical applications to aid the clinicians and improve the quality of healthcare to patients.

Measuring medium-sized muscular arteries using a novel broadband 15-MHz linear array probe.

We recently developed a wideband 15-MHz linear array probe (15 M) with a band width of 8 MHz (9-17 MHz). Both axial and lateral resolution of 15 M, evaluated using a phantom model, were better than those of the current 10-MHz linear probe. To compare interobserver variability in measurement of medium-sized muscular arteries acquired using a 7.5-MHz linear probe (7.5 M), a 10-MHz linear probe (10M) and 15 M, two observers independently acquired images of the brachial and radial arteries, and measured the diameter and intima-media thickness (IMT) of those arteries in 17 male volunteers. Intraobserver variability in determining percent flowmediated dilatation (%FMD) was assessed in the same subjects using 15 M. Coefficients of variation (CV) in arteries measured using 7.5 M, 10 M, and 15 M were 7.0%, 2.5%, and 1.5%, respectively, for the diameter of the brachial artery; 10.3%, 5.8%, and 3.2%, respectively, for the diameter of the radial artery; and 17.0%, 13.8%, and 8.5%, respectively, for IMT of the far wall of the brachial artery. The CV of measurement of %FMD was 4.6%. The new 15-MHz probe thus warrants use in evaluating morphology and function of muscular arteries of medium size.

Ex vivo and in vivo assessment of the non-linearity of elasticity properties of breast tissues for quantitative strain elastography.

The aim of this study was to reveal the background to the image variations in strain elastography (strain imaging [SI]) depending on the manner of manipulation (compression magnitude) during elasticity image (EI) acquisition. Thirty patients with 33 breast lesions who had undergone surgery followed by SI assessment in vivo were analyzed. An analytical approach to tissue elasticity based on the stress-elastic modulus (Young's modulus) relationship was adopted. Young's moduli were directly measured ex vivo in surgical specimens ranging from 2.60 kPa (fat) to 16.08 kPa (invasive carcinoma) under the weak-stress condition (<0.2-0.4 kPa, which corresponds to the appropriate "light touch" technique in SI investigation. The contrast (ratio) of lesion to fat in elasticity ex vivo gradually decreased as the stress applied increased (around 1.0 kPa) on the background of significant non-linearity of the breast tissue. Our results indicate that the differences in non-linearity in elasticity between the different tissues within the breast under minimal stress conditions are closely related to the variation in EI quality. The significance of the "pre-load compression" concept in tissue elasticity evaluation is recognized. Non-linearity of elasticity is an essential attribute of living subjects and could provide useful information having a considerable impact on clinical diagnosis in quantitative ultrasound elastography.

Initial experience of intraoperative three-dimensional navigation for liver resection using real-time virtual sonography.

BACKGROUND: Real-time virtual sonography is an innovative imaging technology that detects the spatial position of an ultrasound probe and immediately reconstructs a section of computed tomography (CT) and/or magnetic resonance in accordance with the ultrasound image, thereby allowing a real-time comparison of those modalities. A novel intraoperative navigation system for liver resection using real-time virtual sonography has been devised for the detection of tumors and navigation of the resection plane. METHODS: Sixteen patients with hepatic malignancies (26 tumors in total) were involved in this study, and the system was used intraoperatively. The tumor size ranged 2 to 140 mm (23 mm in median). By the navigation system, operators could refer intraoperative ultrasound image displayed on the television monitor side-by-side with corresponding images of CT and/or magnetic resonance. In addition, the system overlaid preoperative simulation on the CT image and highlighted the extent of resection so as to navigate the resection plane. Because the system used electromagnetic power in the operation room, the feasibility and safety of the system was investigated as well as its validity. RESULTS: The system could be used uneventfully in each operation. All of the 26 tumors scheduled to be resected were detected by the navigation system. The weight of the resected specimen correlated with the preoperatively simulated volume (R = 0.995, P < .0001). CONCLUSION: The feasibility and safety of the navigation system were confirmed. The system should be helpful for intraoperative tumor detection and navigation of liver resection.

Automatic distance measurement of abdominal aorta for ultrasonography-based visceral fat estimation.

Ultrasonography-based visceral fat estimation is a promising method to assess central obesity, which is associated with metabolic syndrome. The key to this method is to measure three types of distance in the ultrasound image. The most important one is the distance from the skin surface to the posterior wall of the abdominal aorta. We present a novel automatic measurement method to calculate this distance using 1D ultrasound signal processing. It is different from the conventional 2D image processing based methods which have high failure rate when the target is blurred or partially imaged. The proposed method identifies the waveforms of the aorta along a group of ultrasound scan lines and a rating mechanism is introduced to choose the best waveform for distance calculation. The robustness and accuracy of the method were evaluated by experiments based on clinical data.