Yuji Yuasa

Double-phase helical CT of small renal parenchymal neoplasms: correlation with pathologic findings and tumor angiogenesis.

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 corticomedullary 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.

Efficacy of gadolinium-diethylenetriaminepentaacetic acid-enhanced magnetic resonance imaging for differentiation between superficial and muscle-invasive tumor of the bladder: A comparative study with computerized tomography and transurethral ultrasonography

Gadolinium-labeled diethylenetriaminepentaacetic acid (Gd-DTPA)-enhanced magnetic resonance imaging (MRI) was evaluated in an effort to clarify whether MRI could replace or be proved to be superior to computerized tomography (CT) and/or transurethral ultrasonography. A total of 57 bladder cancer patients was evaluated. MRI was performed with a superconducting magnet operating at 1.5 Tesla. The images acquired were multisections, having a fast spin-echo pulse sequence of less than a 14-second breath holding. Serial scans were performed before and immediately after Gd-DTPA venous injection. The findings on different imaging techniques were compared with the histological stagings. A proper diagnosis was made in 42 of 57 cases (73.7%) by Gd-DTPA-enhanced MRI, in 27 of 57 (47.4%) by CT and in 31 of 57 (54.4%) by transurethral ultrasonography when comparing the histological findings. The sensitivity and specificity for differentiating superficial and muscle-invasive tumor of each imaging method were, respectively, 96.2 and 83.3% in Gd-DTPA-enhanced MRI, 96.0 and 58.3% in CT, and 88.0 and 66.7% in transurethral ultrasonography. These data suggest that the staging of bladder cancer by Gd-DTPA-enhanced MRI appears to be superior and more accurate than the staging obtained by CT and transurethral ultrasonography.

Large scale clinical evaluation of bowel contrast agent containing ferric ammonium citrate in MRI

Clear identification of bowel has been thought to be essential in diagnosis by abdominal MRI. We have completed the clinical phase III trial of a new oral contrast agent (FerriSeltz) which is a ferric ammonium citrate based bowel contrast agent. FerriSeltz is a powder that is dissolved in 300 ml water to create a grape-flavored effervescent drink. We have evaluated the usefulness of FerriSeltz, and compared groups receiving 600 mg and 1200 mg of ferric ammonium citrate, the use and nonuse of parasympathetic blockers, and patients with and without fasting in 174 patients who underwent abdominal MRI using this agent. FerriSeltz was found to brighten the stomach and duodenum, contribute to the improvement in diagnostic efficacy, be safe as a bowel contrast agent in abdominal MRI, and be associated with an extremely low incidence of side effects (only mild diarrhea in one of 169 patients). No significant differences were found in the contribution to the improvement in diagnostic efficacy between the two dosage groups, the use and nonuse of parasympathetic blockers, or patients with and without fasting. We concluded that ferric ammonium citrate based compound (FerriSeltz) is a promising bowel contrast agent in abdominal MRI.

Intraarterial digital subtraction angiography with carbon dioxide: superior detectability of arteriovenous shunting.

Intraarterial digital subtraction angiography (IADSA) with carbon dioxide (CO2) was performed on 41 patients with liver or renal diseases. CO2 produced no hypersensitivity reactions, and the pain or feeling of warmth was relatively mild compared with iodinated contrast media. Although the image quality of the arterial or capillary phase was inferior to that with iodinated contrast media, the detectability of arteriovenous shunting was excellent. IADSA with CO2 may become an effective method for detecting arteriovenous shunting which cannot be demonstrated with conventional angiography or DSA with iodinated contrast medium.

Intrauterine MRI with single-shot fast-spin echo imaging showed different signal intensities in hypoplastic lungs.

Abstract Ultrasonography is used for the prenatal diagnosis of hypoplastic lungs. However, ultrasound poses problems because of difficulties in getting the entire lung in perspective and the results depend on the skill of the examiner. When the alveolar formation of the fetal lung is retarded, the fetus is predicted to show an altered density on MRI using an SSFSE sequence due to a varied amount of alveolar lung fluid. We present a case of twins who showed a marked difference in signal intensity of the lung on MRI, which was useful for predicting the fetal pathophysiology. Intrauterine MRI provides the possibility of diagnosing hypoplastic lungs prenatally.

Steroid-responsive painful ophthalmoplegia in childhood: sphenoid sinusitis presenting as Tolosa-Hunt syndrome.

A childhood case of painful ophthalmoplegia which responded well to steroids was described. Although the clinical features suggested Tolosa-Hunt syndrome (THS), serial magnetic resonance imagings (MRI) revealed ethmoid and sphenoid sinusitis in this 7-year-old boy. It was considered that multiple factors such as allergy, viral infection and swimming predisposed him to develop severe sinusitis and gave rise to his painful ophthalmoplegia.

Magnetic resonance signal intensity ratio of gray/white matter in children: Quantitative assessment in developing brain

Magnetic resonance imaging (MRI) findings in 87 children with various clinical entities were used to determine the signal intensity ratio of gray/white matter in T1- and T2-weighted images using a 1.5 T MR Scanner. Signal intensity ratio changes in both T1- and T2-weighted images correlated well with advancing age (y = 0.9349-0.001575, r = -0.584, P < 0.0001 in T1-weighted images; y = 0.9798 + 0.002854, r = 0.723, P < 0.0001 in T2-weighted images), but the correlation was more linear when we included only normally developed (34) children (y = 0.9689-0.001967, r = -0.654, P < 0.0001 in T1-weighted images; y = 0.9882 + 0.002965, r = 0.747, P < 0.0001 in T2-weighted images). Abnormal ratios were observed in patients with congenital hydrocephalus, inherited metabolic diseases and cerebral palsy. Although the gray/white matter differentiation would not delineate the myelination itself, measurement of the signal intensity ratio of gray/white matter is a practical way to evaluate delayed myelination in a busy MR center.

Application of superparamagnetic iron oxide (AMI-227) for 3D phase-contrast MR angiography

Time-of-flight (TOF) MR angiography (MRA) has been utilized in evaluating vascular abnormalities, although there is still a limitation of saturation effect of intravascular spins in imaging slab. The use of contrast material is one of the solutions to reduce the saturation effect. Gadolinium (Gd)-chelating MR contrast agents have been applied for TOF MRA, particularly in body MRA within a short period (1,2). Recently, ultrasmall superparamagnetic iron oxide (USPIO) particles, targeted to RES (reticuloendothelial system), have been applied to TOF MRA (3,4). Their greater T1 relaxivity and longer blood half-life than Gd chelates are additionally promising for MRA. A disadvantage of using Gd chelates in TOF MRA is enhanced background, which is overlaid on vascular structares under maximum-intensity-projection (MIP) method. This problem can be circumvented by three-dimensional (3D) phase-contrast (PC) MRA. The advantage of contrast-enhanced PC MRA over contrast-enhanced TOF MRA is that all stationary tissues are subtracted in PC MRA, improving the visualization of small vessels with signal intensity close to the background. Although the clinical application of Gd-based MR contrast agents for PC MRA has been documented (5,6), the effect of USPIOs in PC MRA is not investigated. In this study, we applied USPIOs for 3D PC MRA and evaluated the efficacy in various scanning parameters.

Individualized total cavopulmonary connection technique for patients with Asplenia syndrome

BACKGROUND Outcomes after univentricular repair for patients with asplenia syndrome remain unsatisfactory, not only because of clinical difficulties in patient selection, but also secondary to technical difficulties in the separation of the systemic and pulmonary circulations, particularly with the rerouting technique for the inferior systemic veins. METHODS Between February 1995 and May 2000, a total of 14 consecutive patients with asplenia syndrome underwent bidirectional cavopulmonary connection with obliteration of additional pulmonary blood flow, followed by a total cavopulmonary connection. The rerouting technique for inferior systemic venous blood flow was individualized to optimize laminar nonturbulent flow characteristics in the pathway, and to minimize prosthetic load and suture load on the atrial wall. The lateral tunnel or tube conduit technique was used in an extraatrial, intra-extraatrial, or intraatrial fashion. No fenestration was applied. RESULTS No hospital mortality was observed. Systemic venous flow was evaluated using magnetic resonance angiography, revealing no signs of obstruction, turbulence, or stasis either in or near the reconstructed pathways, irrespective of the rerouting technique. Postoperative catheterization revealed favorable hemodynamics including an inferior vena cava pressure of 13 +/- 2 mm Hg and arterial oxygen saturation of 93.4% +/- 3.5% at room air. All patients have remained free of symptoms, although 1 patient died of acute septic complications 3.5 years after the procedure. CONCLUSIONS The complexity of cardiac anomalies in asplenia syndrome warrants individualization of the total cavopulmonary connection technique used in reconstruction of the inferior systemic venous pathway. Optimizing flow characteristics in the pathway should be a priority. A staging approach allows suitable selection of candidates for univentricular repair.

Dynamic MR Imaging and Tumor Angiogenesis in DMBA-Induced Rat Breast Cancer: Three Dimensional (3D) Reconstructed Image Analysis of Tumor Microvessels by Confocal Laser Scanning Microscopy.

We investigated the correlation between dynamic magnetic resonance imaging (MRI) findings in breast cancer and tumor angiogenesis in a dimethylbenz(a)anthracene (DMBA)-induced rat breast cancer model. In this study, we clearly demonstrated the three-dimensional (3D) architecture of tumor microvessel networks (MN) by confocal laser scanning microscopy (CLSM) and also investigated the hyperpermeability of tumor microvessels. Dynamic MRI findings were closely related to tumor angiogenesis. Three-dimensional reconstructed image analysis by CLSM revealed that the depicted images were dependent on microvessel density as well as microvessel permeability. It should be emphasized that dynamic MRI may have the potential to evaluate the tumor angiogenic activity in human breast carcinoma.