Shigeo Okuda

Temperature mapping using the water proton chemical shift: Self- referenced method with echo-planar spectroscopic imaging

An echo‐planar spectroscopic imaging method of temperature mapping is proposed. This method is sufficiently faster than the so‐called 3D magnetic resonance spectroscopic imaging (3D‐MRSI) method and does not require image subtractions, unlike the conventional phase mapping method when an internal reference signal is detectable. The water proton chemical shift measured by using the tissue lipid as an internal reference clearly visualized the temperature change in a porcine liver sample in vitro. It was also demonstrated that the internally referenced echo‐planar spectroscopic imaging method could markedly reduce a temperature error caused by a simple, translational motion between scans compared with the phase‐mapping method. Magn Reson Med 43:220–225, 2000.

Biexponential apparent diffusion coefficients in prostate cancer

PURPOSE The purpose of this study was to investigate the need for biexponential signal decay modeling for prostate cancer diffusion signal decays with b-factor over an extended b-factor range. MATERIALS AND METHODS Ten healthy volunteers and 12 patients with a bulky prostate cancer underwent line scan diffusion-weighted MR imaging in which b-factors from 0 to 3000 s/mm(2) in 16 steps were sampled. The acquired signal decay curves were fit with both monoexponential and biexponential signal decay functions and a statistical comparison between the two fits was performed. RESULTS The biexponential model provided a statistically better fit over the monoexponential model on the peripheral zone (PZ), transitional zone (TZ) and prostate cancer. The fast and slow apparent diffusion coefficients (ADCs) in the PZ, TZ and cancer were 2.9+/-0.2, 0.7+/-0.2 x 10(-3) mm(2)/ms (PZ); 2.9+/-0.4, 0.7+/-0.2 x 10(-3) mm(2)/ms (TZ); and 1.7+/-0.4, 0.3+/-0.1 x 10(-3) mm(2)/ms (cancer), respectively. The apparent fractions of the fast diffusion component in the PZ, TZ and cancer were 70+/-10%, 60+/-10% and 50+/-10%, respectively. The fast and slow ADCs of cancer were significantly lower than those of TZ and PZ, and the apparent fraction of the fast diffusion component was significantly smaller in cancer than in PZ. CONCLUSIONS Biexponential diffusion decay functions are required for prostate cancer diffusion signal decay curves when sampled over an extended b-factor range, providing additional, unique tissue characterization parameters for prostate cancer.

Decreased pregnancy rate is linked to abnormal uterine peristalsis caused by intramural fibroids

BACKGROUND The relationship between fibroids and infertility remains an unsolved question, and management of intramural fibroids is controversial. During the implantation phase, uterine peristalsis is dramatically reduced, which is thought to facilitate embryo implantation. Our aims were to evaluate (i) the occurrence and frequency of uterine peristalsis in infertile women with intramural fibroids and (ii) whether the presence of uterine peristalsis decreases the pregnancy rate. METHODS Ninety-five infertile patients with uterine fibroids were examined using magnetic resonance imaging (MRI). Inclusion criteria were as follows: (i) presence of intramural fibroids, excluding submucosal type; (ii) no other significant infertility factors (excluding endometriosis); and (iii) regular menstrual cycles, and MRI performed at the time of implantation (luteal phase day 5-9). The frequency of junctional zone movement was evaluated using cine-mode-display MRI. After MRI, patients underwent infertility treatment for up to 4 months, and the pregnancy rate was evaluated prospectively. RESULTS Fifty-one patients fulfilled the inclusion criteria, and 29 (57%) and 22 (43%) patients were assigned to the low (0 or 1 time/3 min) or high frequency (≥ 2 times/3 min) uterine peristalsis group, respectively. Endometriosis incidence was the same in both groups. Ten out of the 29 patients (34%) in the low-frequency group achieved pregnancy, compared with none of the 22 patients (0%) in the high-frequency group (P< 0.005). Comparing pregnant and non-pregnant cases, 4 of 10 patients (40%) and 9 of 41 patients (22%), respectively, had endometriosis (not significant). CONCLUSIONS A higher frequency of uterine peristalsis during the mid-luteal phase might be one of the causes of infertility associated with intramural-type fibroids.

Incidence and Prognostic Significance of Myocardial Late Gadolinium Enhancement in Patients With Sarcoidosis Without Cardiac Manifestation

BACKGROUND Cardiac death is the leading cause of mortality associated with sarcoidosis in Japan. However, the involvement of sarcoidosis infiltration often remains undetected. Recently, late gadolinium enhancement with cardiovascular MRI (LGE-CMR) imaging has been introduced for the detection of myocardial infiltrative disease, as it enables the detection of even minor myocardial damage. We investigated the incidence and prognostic value of LGE-CMR in patients with extracardiac sarcoidosis without cardiac manifestations. METHODS Sixty-one consecutive patients who met the histologic and clinical criteria for sarcoidosis, and who did not have signs or symptoms of cardiovascular involvement, were prospectively recruited. LGE-CMR was performed at the time of enrollment, and patients were classified into positive or negative late gadolinium enhancement groups based on the findings. The study end point was a composite of all-cause death, symptomatic arrhythmia, and heart failure necessitating admission. RESULTS Patients were predominantly middle aged (57 ± 15 years) and female (66%), and most had stable disease activity that did not require treatment with immunosuppressants. LGE-CMR detected cardiac involvement in eight patients (13%). Interventricular septal thinning detected by echocardiography was an independent predictor of LGE-CMR-detected cardiac involvement. During the follow-up period of 50 ± 12 months, no significant difference in adverse events was noted between patients in the LGE-CMR-positive and LGE-CMR-negative groups. CONCLUSIONS LGE-CMR detected cardiac involvement in 13% of patients with sarcoidosis without cardiac manifestation, but both patients with and without LGE had relatively low event rates. TRIAL REGISTRY Japan Primary Registries Network; No.: UMIN000001549; URL: www.umin.ac.jp.

Quantitative Analysis of Right Ventricular Function in Patients With Pulmonary Hypertension Using Three-Dimensional Echocardiography and a Two-Dimensional Summation Method Compared to Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is considered the clinical reference standard for measuring the right ventricular (RV) volume and ejection fraction, although real-time 3-dimensional echocardiography (RT3DE) would be a preferred method owing to its convenience and availability for repetitive examinations. However, the feasibility, accuracy, and reproducibility of RT3DE have not been fully examined. The present study sought to validate the correlation of RT3DE with a 2-dimensional summation method compared to MRI for assessing the function of the right ventricle and to evaluate the RV function in patients with pulmonary hypertension (PH). Thirty patients with PH underwent both RT3DE and MRI. The right ventricle was reconstructed with RT3DE using a 2-dimensional summation method to analyze the MRI measurements. The RV end-diastolic volume, RV end-systolic volume, and RV ejection fraction were measured. Fifteen normal subjects underwent the same echocardiographic protocol for comparison. The RV end-diastolic volume index, RV end-systolic volume index, and RV ejection fraction measured using RT3DE correlated well with those measured using MRI (R = 0.96, p <0.001; R = 0.96, p <0.001; p = 0.93, and p <0.001, respectively). All inter- and intraobserver variability values for the RV end-diastolic volume, RV end-systolic volume, and RV ejection fraction were <17%. Both the RV end-diastolic volume index and the RV end-systolic volume index were significantly enlarged in those with PH compared to those in the normal subjects (RVEDVI 123 ± 42 ml/m² vs 74 ± 12 ml/m²; RVESVI 86 ± 33 ml/m² vs 26 ± 5 ml/m² in those with PH and the normal subjects, respectively, p <0.0001). In contrast, the RV ejection fraction was significantly reduced in the patients with PH compared to that in the normal subjects (30 ± 12% vs 65 ± 6%, respectively, p <0.01). Thus, RT3DE with a 2-dimensional summation method might provide comparable and feasible measurements of the RV volume in patients with PH compared to MRI.

Myomectomy Decreases Abnormal Uterine Peristalsis and Increases Pregnancy Rate

BACKGROUND The relationship between fibroids and infertility remains a critical and unresolved question. During the implantation phase, it is known that uterine peristalsis is dramatically reduced, which is thought to facilitate implantation of the embryo to the endometrium. In the previous study, using a cine MRI mode, we found that less than half of the patients with intramural fibroids exhibited abnormal uterine peristalsis during the mid-luteal phase. In the present study, we further investigated whether myomectomy for patients in the high peristalsis group is a constructive method to normalize uterine peristalsis. METHODS The frequency of junctional zone movement was evaluated using a cine MRI mode during the mid-luteal phase. Fifteen infertility patients, who had intramural myomas and exhibited abnormal uterine peristalsis (≥2 times/3 min) in their first MRI, underwent myomectomy and a second MRI. After receiving the second MRI, patients underwent infertility treatment for at least 8 months, and pregnancy rate was evaluated prospectively. RESULTS Among 15 patients, the frequency of uterine peristalsis was normalized (0 or 1 time/3 min) in 14 patients. Following myomectomy and second MRI test, 6 of the 15 patients achieved pregnancy (n = 15, pregnancy rate: 40%). CONCLUSIONS The presence of uterine fibroids might induce abnormal uterine peristalsis in some patients, leading to infertility, and myomectomy may improve fertility in these patients.

Superparamagnetic iron oxide-enhanced MR imaging for focal hepatic lesions: a comparison with CT during arterioportography plus CT during hepatic arteriography.

BackgroundWe aimed to evaluate the efficacy of a breath-hold superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging protocol for the detection of focal hepatic lesions, in comparison with a non-breath-hold SPIO-enhanced imaging protocol and computed tomography during arterioportography (CTAP) plus CT during hepatic arteriography (CTHA).MethodsFindings of SPIO-enhanced MR imaging and CTAP/CTHA for 24 hepatic metastases in 17 patients and 29 HCCs in 21 patients were analyzed. All patients underwent breath-hold SPIO-enhanced MR imaging (1.5 tesla), breath-hold plus non-breath-hold SPIO-enhanced MR imaging, and CTAP plus CTHA prior to partial hepatectomy or laparoscopic ablation therapy. Histopathology for lesion characterization and intraoperative ultrasound for lesion detection were available for all patient. Breath-hold SPIO-enhanced MR imaging consisted of T2-weighted single-short fast spin echo (FSE), T2-weighted (T2W) FSE, T2*-weighted gradient echo (GRE), and T1-weighted GRE. For the non-breath-hold imaging protocol, respiratory-triggered, fat-suppressed T2W-FSE was added to the breath-hold MR imaging protocol. Double phase CTAP plus CTHA was performed on an angio-CT system. To compare the three imaging protocols, three radiologists performed blind film reading, and all data, on a hepatic segment-to-segment basis, were entered for alternative free-response receiver-operating characteristic (AFROC) analysis.ResultsROC analysis showed that there was no significant difference in the area under the AFROC curve (A1) value for metastases and HCCs among the three protocols; the breath-hold SPIO-enhanced MR imaging protocol, non-breath-hold MR imaging protocol, and CTAP plus CTHA. The breath-hold SPIO-enhanced MR imaging protocol showed a sensitivity, specificity, and accuracy equivalent to the non-breath-hold MR imaging protocol and CTAP plus CTHA.ConclusionsAs a preoperative test, SPIO-enhanced MR imaging could have the potential to replace CTAP plus CTHA in a certain clinical setting.

Diagnostic accuracy of stress myocardial perfusion MRI and late gadolinium-enhanced MRI for detecting flow-limiting coronary artery disease: a multicenter study

The aim of this study was to determine the diagnostic performance of stress and rest perfusion magnetic resonance imaging (MRI) and late gadolinium-enhanced (LGE) MRI for identifying patients with obstructive coronary artery disease (CAD). A total of 50 patients with suspected CAD underwent stress-rest perfusion MRI, followed by LGE MRI with a 1.5-T system. Stress-rest perfusion MRI resulted in an area under the receiver-operating characteristic curve (AUC) of 0.92 for observer 1 and 0.84 for observer 2 with sensitivity and specificity of 89% (32/36) and 79% (11/14) by observer 1, 83% (30/36) and 71% (10/14) by observer 2, respectively, showing a moderate interobserver agreement (Cohen’s κ = 0.49). While combination of stress-rest perfusion and LGE MRI did not result in improved accuracy for the prediction of flow-limiting obstructive CAD (AUC 0.81 for observer 1 and 0.80 for observer 2), the sensitivity was increased to 92% in both observers with a substantial interobserver agreement (κ = 0.70). Stress-rest myocardial perfusion MRI is an accurate diagnostic test for identifying patients with obstructive CAD.

OATP1B3 expression is strongly associated with Wnt/β-catenin signalling and represents the transporter of gadoxetic acid in hepatocellular carcinoma

BACKGROUND & AIMS In the current era of emerging molecular targeted drugs, it is necessary to identify before treatment the specific subclass to which a tumour belongs. Gadoxetic acid is a liver-specific contrast agent that is preferentially taken up by hepatocytes. Therefore, gadoxetic acid-enhanced magnetic resonance imaging (EOB-MRI) should provide precise molecular information about hepatocellular carcinomas (HCCs). The aim of this study was to investigate the transporters of gadoxetic acid in HCC comprehensively and to analyse the molecular regulatory mechanism of such transporters. METHODS Expression levels of transporters, transcriptional factors and Wnt target genes in clinical samples were examined by quantitative real-time reverse transcription polymerase chain reaction and immunohistochemistry. LiCl treatment of the HCC cell line KYN-2 was conducted in vitro to assess the effects of Wnt signalling activity. RESULTS Comprehensive analyses of transporter mRNAs and protein expressions revealed that the organic anion transporting polypeptide 1B3 (OATP1B3) had the strongest correlation with tumour enhancement in hepatobiliary-phase images of EOB-MRI. Association analysis with OATP1B3 expression revealed significant correlation with the expression of Wnt/β-catenin target genes. Further, LiCl treatment induced OATP1B3 mRNA expression in KYN-2 cells, indicating a strong association between OATP1B3 expression and Wnt/β-catenin signalling. The sensitivity and specificity to predict Wnt/β-catenin-activated HCC using tumour enhancement in EOB-MRI were 78.9% and 81.7%, respectively. CONCLUSIONS OATP1B3 was confirmed as the most important transporter mediating HCC enhancement in EOB-MRI. OATP1B3 expression showed a strong association with the expression of Wnt/β-catenin target genes, therefore, OATP1B3-upregulated HCC likely represents a specific subclass of Wnt/β-catenin-activated HCC.

MR-based temperature monitoring for hot saline injection therapy

We applied magnetic resonance (MR) phase mapping methods to monitor the thermal frequency shift of water in order to study temperature changes from percutaneous hot saline injection therapy (PSIT) using in vitro swine livers and in vivo rabbit livers. The thermal coefficients calculated from the shifts of the water frequency with thermocouple based temperature measurements were −0.0085 ± 0.0019 ppm/°C for the in vitro studies and −0.0089 ppm/°C for the in vivo studies. The error range was estimated to be ± 3°C and ± 4.5 °C, respectively. Color‐coded temperature maps were compared with macroscopic lesion sizes of the specimen. Regions defined using a 20°C elevation in the initial images following hot saline injection (around 55°C in absolute temperature) closely correlated with visible coagulation in size. We conclude that MR temperature monitoring of PSIT is quite feasible and may be helpful in expanding the clinical use of this thermal therapeutic tool for liver tumors. J. Magn. Reson. Imaging 2000;12:330–338.