Published papers

Purpose: To qualitatively and quantitatively evaluate the diagnostic efficacy of the breathhold magnetic resonance (MR) imaging sequences in widespread clinical use for detection and characterization of focal hepatic lesions. Materials and Methods: Fifty patients with 143 lesions [57 hepatocellular carcinomas (HCC), 10 borderline lesions, 18 metastatic tumors, 21 hemangiomas, and 37 cysts] underwent single-shot fast spin echo (SSFSE), fast spin echo (FSE), and gadolinium-enhanced dynamic fast spoiled gradient-recalled acquisition in steady state (FSPGR) breath-hold MR imaging of the liver. Alternative free receiver operating characteristic (AFROC) analysis was performed to independently and prospectively assess each sequence. Results: For solid lesions, dynamic FSPGR allowed the most sensitive lesion detection and produced the highest lesion conspicuity and lesion-liver contrast-to-noise ratio (CNR). For non-solid benign lesions, SSFSE and FSE produced better results than dynamic FSPGR. SSFSE allowed the most sensitive detection and produced the best lesion conspicuity and lesion-liver CNR. Conclusion: SSFSE and dynamic FSPGR comprise the optimal imaging protocol for breathhold MR assessment of focal hepatic lesions. This combination of sequences allows acquisition of critical diagnostic information about both inherent T2 and T1 lesion contrast and lesion vascularity.

The number of hepatic nodules detected by ultrasonography in patients with chronic liver disease has increased. Although it potentially is important to understand the outcome of small solitary hepatic nodules, they have not been fully investigated. In this study, we evaluated retrospectively the outcome of 35 solitary hepatic nodules smaller than 10 mm in 35 patients with chronic liver disease. The follow-up period ranged from 24 to 94 months, and, during follow-up, 8 of 35 nodules (23%) increased in size, 17 nodules (49 %) showed no change, and 10 nodules (29%) disappeared. It took less than 12 months for 5 nodules to increase in size, and less than 24 months for 3 nodules. There was no significant difference between the ultrasonographic findings (echogenicity and size) of the nodules and their outcome. We conclude that follow-up observation of at least 24 months is essential to evaluate the outcome of solitary hepatic nodules.

Magnetic resonance (MR) imaging-guided prostate biopsy in a O.5-T open imager is described, validated in phantom studies, and performed in two patients. The needles are guided by using fast gradient-recalled echo and T2-weighted fast spin-echo images. Surgical navigation software provided T2-weighted images critical to targeting the peripheral zone and the tumor. MR imaging can be used to guide prostate biopsy.

Purpose: To correlate the enhancement pattern of double-phase helical computed tomography (CT) of small renal parenchymal neoplasms with pathologic findings and tumor angiogenesis, and evaluate whether the enhancement pattern would be useful in differentiating the histomorphologic types of small renal parenchymal neoplasms. Materials and Methods: Double-phase helical CT (5 mm slice) of the cortico-medullary phase (CMP) and late nephrographic phase (NP) was performed in 40 surgically resected renal neoplasms <3.5 cm. The patterns of CT attenuation value and homogeneity were correlated with the subtypes of neoplasms, microvessel density, and the existence of intratumoral necrosis or hemorrhage. Results: Clear cell renal cell carcinomas (RCC) (n = 29) showed a peak attenuation value in the CMP of >100 HU [Hounsfield units]. Chromophobe cell RCC (n = 2) showed a peak attenuation value in the CMP of <100 HU. Papillary RCC (n = 5) showed a gradual enhancement with the attenuation value in the CMP of <100 HU. However oncocytomas (n = 2) and metanephric adenomas (n = 2) also showed patterns similar to these subtypes of RCC. The degree of enhancement in the CMP correlated with microvessel density (r = 0.87). All tumors with an homogeneous enhancement pattern did not show necrosis or hemorrhage on histologic specimen. Conclusion: The enhancement pattern in double-phase helical CT was different among the subtypes of RCC, and correlated with microvessel density or the existence of intratumoral necrosis or hemorrhage. However it did not differentiate between RCC and other solid tumors.

A 54-year-old woman was admitted to this institution for further examination and treatment of a mass in the fight breast. The mass was a palpable hard lump that measured approximately 2 cm in diameter. Breast cancer was strongly suspected, and ultrasound examination was performed. The conventional B-mode image showed a well-defined, hypoechoic mass with a lobulated margin in the right mammary gland; the color Doppler image showed a penetrating feeding vessel and intralesional vessels; and the contrast-enhanced color Doppler image showed intense signals from the intralesional vessels. The feeding and intralesional vessels were clearly shown in B-mode contrast harmonic imaging with pulse inversion. It was suggested that B-mode contrast harmonic imaging with pulse inversion is suitable for detection of tumor vessels in a small, superficial organ such as a mammary gland.

Purpose: We report the findings of a transperineal magnetic resonance image (MRI) guided biopsy of the prostate in a man with increasing prostate specific antigen who was not a candidate for a transrectal ultrasound guided biopsy. Materials and Methods: Using an open configuration 0.5 Tesla MRI scanner and pelvic coil, a random sextant sample was obtained under real time MRI guidance from the peripheral zone of the prostate gland as well as a single core from each MRI defined lesion. The patient had previously undergone proctocolectomy for ulcerative colitis and, therefore, was not a candidate for transrectal ultrasound guided biopsy. Prior attempts to make the diagnosis of prostate cancer using a transurethral approach were unsuccessful. Results: The random sextant samples contained benign prostatic hyperplasia, whereas Gleason grade 3 + 3 = 6 adenocarcinoma was confirmed in 15% and 25% of the 2 cores obtained from the MRI targeted specimens of 2 defined lesions. The procedure was well tolerated by the patient. Conclusions: Transperineal MRI guided biopsy is a new technique that may be useful in detecting prostate cancer in men with increasing prostate specific antigen who are not candidates for transrectal ultrasound guided biopsy.

The optimal pulsating cardiac phantom is an important tool for the evaluation of cardiac images and cardiac applications on ECG-gated MDCT. The purpose of this study was to demonstrate the design and fabrication of the pulsating cardiac coronary phantom. The newly developed pulsating cardiac coronary phantom has the following five key advantages: 1 )a driver component that uses only one servomotor to move the phantom in three dimensions (X, Y, and Z directions) with 16 presets of different heart types (heartbeat: 0-120 bpm; ejection fraction: 0-90%): 2)versatile pumping and filling phases to simulate a real heart in a cardiac cycle can be incorporated into the driver sequence including shift of patient heartbeat or irregular pulse (maximum: 200 different heart waves in one scan): 3)a cardiac coronary component constituted of an acrylic/silicon/rubber tube(2-6 mm inner diameter)with stent/in-stent restenosis/steriosis/soft plaque/ calcification parts and maximum 16 coronary arteries that can be attached to the phantom in the same scan: 4)the complete phantom can be submerged in a tank to simulate the heart and its surrounding tissues: 5)ECG gating can be from interior trigger and exterior trigger. It has been confirmed that the developed pulsating cardiac phantom is very useful to quantitatively assess imaging of the heart and coronary arteries during phantom experiments.

Purpose: ECG-gated cardiac MDCT offers many cardiac clinical applications. The goals of this report are 1) to introduce a new concept of effective reliability (ER) from effective temporal resolution for the evaluation of ejection fraction (EF) and evaluation of image quality (IQ)of coronary arteries, and 2)to show the correlation of ER and the accuracy of EF with different cardiac reconstruction algorithms and different rotation speeds. Methods and Materials: To assess the accuracy of EF, helical scanning was performed with a gated cardiac MDCT(GE LightSpeed, 8/16 slice)on pulsating cardiac coronary phantoms(0.5 and 0.6 sec rotation speed for each 50-110 bpm, 5-bpm step). We define effective reliability(ER)from effective temporal resolution(%)as follows: ER=(1-TR/HC)x100: TR: Effective temporal resolution, HC: time of heart cycle in each bprn. Results: From the results of the EF measurement and calculated ER, high accuracy was obtained by using optimal scan conditions (optimal rotation speed and cardiac reconstruction algorithm)in a wide range of heart rates (heart rate<90: EF & ER>81%; heart rate<110 bpm: EF & ER>73%). Results showed that the calculated ER is closely correlated with the measurement results of EF based on the phantom experiment (R 2=0.901±0. 075; Max: 0.994, Min: 0.738). Optimal reconstruction thickness can reduce total image number for the evaluation of EF. Conclusion: We concluded that the ER is useful to evaluate EF accuracy and the IQ of images of coronary arteries.

Objective: The purpose of this study is to consider the possibility of quantitative evaluation of coronary arterial stenosis by using 16-slice multidetector-row computed tomography (MDCT). Methods: Simulated coronary arteries were prepared, which consist of 5-mm-diameter acryl tubes with contrast media (270 HU). Simulated stenoses of known density (-33 HU) were created in each coronary artery (25%, 50%, and 75%). Cardiac pulsating with 0, 50, 65, 85, and 105 beats per minute (bpm) was performed. Multiplanar reformation images for each coronary artery were created. Percent stenosis was calculated using the width middle value of boundary part of the arteries. Results: The stenoses were depicted in all heart rates. Average percent stenosis ± standard deviation was 27.4 ± 3.6%, 45.8 ± 2.6%, and 69.4 ± 2.7%, respectively. For each percent stenosis, there was a significant difference (P < 0.05). Conclusion: Sixteen-slice MDCT has a potential for noninvasive quantitative evaluation of stenosis in coronary arteries. Copyright © 2005 by Lippincott Williams & Wilkins.

We compared multidetector-row CT urography and intravenous urography (IVU) for the detection of pelvic tumors. CT images (axial image, MIP image and MPR image) and IVU images of three cases were evaluated with the consensus of two radiologists. The usefulness of CTU was as follows. 1) The MIP image is very similar to the IVU image. 2) The images of CTU are free from the overlying bowel gas, whereas IVU images are obscured by it. 3) Although the spatial resolution of CT is lower than that of IVU, pelvic tumors sized 10 mm can be demonstrated on CTU, but not on IVU.

OBJECTIVE. Our purpose was to determine whether thin overlapping reconstructions using MDCT improve the detection and characterization of small renal masses. MATERIALS AND METHODS. Thirty-seven patients were scanned with MDCT using 2.5-mm collimation. Nephrographic phase data were reconstructed in two ways: a standard protocol (5-mm section thickness, no overlap) and an experimental protocol (3-mm section thickness, 50% overlap). Masses were detected and classified into three groups: group 1, measuring less than 20 H on both protocols (classified as cysts on both); group 2, measuring 20 H or greater on standard protocol and less than 20 H on experimental protocol (classified as cysts using experimental protocol only); and group 3, measuring 20 H or greater on both protocols (not classified as cysts using either protocol). Masses 10 mm or larger in group 3 were evaluated further for enhancement. Statistically significant differences between protocols were assessed using an analysis of counts and proportions. RESULTS. Of 175 detected lesions, 29 (17%) were detected only with the experimental protocol; all but one were smaller than 5 mm. Using the experimental protocol, of 45 masses between 5 and 10 mm, the number of masses that could be characterized as cysts increased from 13 (29%) to 38 (84%). The overall number of indeterminate lesions was reduced from 101 (69%) of 146 lesions detected with the standard protocol to 86 (53%) of 161 lesions detected with the experimental protocol. CONCLUSION. Using MDCT and thin overlapping reconstructions, renal cysts as small as 5 mm can be diagnosed with more confidence than is possible with standard reconstructions, and the overall number of indeterminate renal masses is reduced.