Toshiaki Miyati

Non-invasive measurement of intracranial compliance using cine MRI in normal pressure hydrocephalus

The aim of this study is to clarify biophysics of normal pressure hydrocephalus (NPH) based on non-invasive intracranial compliance measurement using magnetic resonance imaging (MRI). Patients with NPH after subarachnoid hemorrhage (NPH group, n = 5), brain atrophy or asymptomatic ventricular dilation (VD group, n = 5), and healthy volunteers (control group, n = 12) were included in this study. Net blood flow (bilateral internal carotid and vertebral arteries, and jugular veins) and cerebrospinal fluid (CSF) flow in subarachnoid space at the C2 level of cervical vertebra were measured using phase-contrast cine MRI. CSF pressure gradient and intracranial volume changes during a cardiac cycle were calculated based on Alperins method. Compliance index (Ci = delta V/delta P) was obtained from the maximum pressure gradient and volume changes. Pressure volume response (PVR) was measured in the NPH group during a shunt operation. Ci in the NPH group was the lowest among the three studies groups. No difference was found between the control and VD groups. There was a linear correlation between Ci and PVR. In conclusion, intracranial compliance can be determined by cine MRI non-invasively. It is well known that NPH has relatively low intracranial compliance, this non-invasive method can be used for the diagnosis of NPH.

Noninvasive estimation of intracranial compliance in idiopathic NPH using MRI

BACKGROUND The pathophysiology of idiopathic normal pressure hydrocephalus (I-NPH) is still unclear and the diagnosis is sometimes difficult. The aim of this study was to assess the biophysics of I-NPH by measuring intracranial compliance using cine MRI. METHODS The study included patients with I-NPH (I-NPH group, n = 13), brain atrophy or asymptomatic ventricular dilation (VD group, n = 10), and healthy volunteers (control group, n = 13). Net blood flow (bilateral internal carotid and vertebral arteries and jugular veins) and cerebrospinal fluid (CSF) flow in the subarachnoid space at the C2 cervical vertebral level were measured using phase-contrast cine MRI. CSF pressure gradient (PG(p-p)) and intracranial volume changes (VC(p-p)) during a cardiac cycle were calculated. FINDINGS The compliance index (CI=VC(p-p)/PG(p-p)) in the I-NPH group was significantly lower than in the control and VD groups, whereas no difference was found between the control and VD groups. CI values of I-NPH patients after the tap test were larger than those before. These results clearly show that the intracranial compliance of I-NPH is relatively low compared to that of brain atrophy or normal subject. The increase of CI after a tap test also supports this finding. CONCLUSIONS It is possible to estimate intracranial compliance as CI non-invasively using cine MRI. CI could become a useful method for the diagnosis of I-NPH.

Pleomorphic adenoma of the breast

Pleomorphic adenoma is a very rare benign tumor of the breast. Only 70 cases have been reported in the world literature. Recently, we encountered a case of pleomorphic adenoma of the breast and thus present here the mammographic and ultrasonographic findings with the pathology of this rare breast tumor. The patient was a 76-year-old Japanese woman with a right breast mass. The mammography showed a 1.5-cm, lobulated high-density mass with partially ill-defined margins. Ultrasonography revealed an irregularly shaped mass with partially ill defined borders, hypoechoic and heterogeneous internal echoes, and posterior acoustic enhancement. These findings suggested an invasive carcinoma. Awareness of this type of tumor will help in correct diagnosis, in spite of the rarity of this disease.

Subtraction SPECT for Parathyroid Scintigraphy Based on Maximization of Mutual Information

Our objective was to investigate the feasibility of subtraction for SPECT images of 99mTc-MIBI double-phase parathyroid scintigraphy. Methods: Fourteen patients with hyperparathyroidism were enrolled in the present study. Histopathologically, excised tissue specimens showed hyperplasia in 11 patients and adenoma in 3 patients. Both ultrasonography and 99mTc-sestamibi (MIBI) SPECT images were obtained from all patients. As standard lines to ensure that patient positioning remained identical between the different phases, we used the cross-marker produced by a pair of laser pointers, the orbitomeatal line, and the vertical midline through the patients nose. Data processing was performed with software that enables image registration by maximization of mutual information. The results of subtraction SPECT imaging were compared with those of ultrasonography. Results: The registration of double-phase SPECT images was successful in all patients when the salivary glands were excluded from the image reconstruction region. The overall sensitivities of scintigraphy and ultrasonography were 90.9% (40/44) and 70.5% (31/44), respectively, with respective specificities of 83.3% (10/12) and 75.0% (9/12). Scintigraphy and ultrasonography showed accuracies of 92.8% (52/56) and 71.4% (40/56), respectively. Conclusion: The new technique used in the present study allowed the subtraction for SPECT images. The sensitivity of parathyroid lesion detection using this technique was superior to that of ultrasonography.

Hemodynamic analysis of bladder tumors using T1-dynamic contrast-enhanced fast spin-echo MRI

OBJECTIVES To evaluate the hemodynamics of bladder tumors, we developed a method to calculate change in R(1) value (ΔR(1)) from T(1)-dynamic contrast-enhanced fast spin-echo magnetic resonance imaging (T(1)DCE-FSE-MRI). MATERIALS AND METHODS On a 1.5-T MR system, T(1)DCE-FSE-MRI was performed. This study was applied to 12 patients with urinary bladder tumor, i.e. urothelial carcinoma. We compared ΔR(1)-time and ΔSI-time between a peak in the ΔR(1)-time and ΔSI-time curve occurred during the first pass within 60s. Next, we assessed the slope of increase for 180s after CA injection (Slope(0-180)). RESULTS The mean slope of the first pass was significantly higher for bladder tumors on both the ΔR(1)-time and the ΔSI-time curve compared with normal bladder walls. Moreover, a significant difference was apparent between bladder tumors and normal bladder walls on the mean Slope(0-180) in the ΔR(1)-time curve. However, no significant difference in the mean Slope(0-180) was observed on the ΔSI-time curve between bladder tumors and normal bladder walls. CONCLUSION T(1)DCE-FSE-MRI offers three advantages: quantitative analysis; high-quality (i.e., artifact-free) images; and high temporal resolution even for SE images. Use of ΔR(1) analysis with T(1)DCE-FSE-MRI allows more detailed information on the hemodynamics of bladder tumors to be obtained and assists in differentiation between bladder tumors and the normal bladder wall.

Development of qualitative near infrared vascular imaging system with tuned aperture computed tomography

We developed a novel system for imaging and qualitative analysis of surface vessels using near infrared (NIR) radiation with tuned aperture computed tomography (TACT®), even if the NIR cannot transmit through thick regions. NIR-sensitive CCD camera was surrounded by sixty light emitting diodes (alternating wavelengths of 700 nm and 810 nm), and could only detect the NIR from the subcutaneous tissue. We obtained multiple near infrared projections of surface vessels at each wavelength in accordance with the optical aperture theory within one second. Then, we created tomograms using the TACT program, and determined the venous oxygenation index (VOI), which reflected the oxygen saturation level, calculated from the image signals at each wavelength. This system produced thinner NIR tomograms under 0.5 mm. The change in VOI after load test calculated from NIR tomograms was more sensitive than that from NIR images without tomography. Our novel system makes it possible to non-invasively obtain NIR tomograms and accurately analyze changes in oxygen saturation.

Spectral PTF analysis using cine-MRI in normal pressure hydrocephalus

To clarify intracranial dynamical properties in normal pressure hydrocephalus (NPH), we assessed a spectral phase transfer function (PTF) calculated from the driving vascular pulsation and cerebrospinal fluid (CSF) flow in the aqueduct. Because the PTF is thought to change in accordance with the degree of pressure damping.

Diffusion kurtosis imaging with the breath-hold technique for staging hepatic fibrosis: A preliminary study

PURPOSE To evaluate the potential of diffusion kurtosis imaging (DKI) analysis with the breath-hold technique to assess the stage or classify hepatic fibrosis. MATERIALS AND METHODS Patients (n=67) suspected of having a disease of the hepatobiliary system examined by diffusion-weighted imaging (DWI) using a 3.0-T magnetic resonance imaging unit were enrolled in this study. To evaluate hepatic fibrosis, mean kurtosis, Mean apparent diffusion (MD) and apparent diffusion coefficient (ADC) values were compared between groups with varying fibrosis; F0-F1, F2-F3, and F4. The Steel-Dwass test was used for overall comparisons. Correlations between the fibrosis stage and mean kurtosis, MD or ADC values were assessed using Spearmans rank correlation. Discriminative capacities of DKI were evaluated using receiver operating characteristic (ROC) analysis. RESULTS There were significant differences in ADC, MD and mean kurtosis values between non-cirrhosis and cirrhosis groups. Moreover, the mean kurtosis value was statistically different between the F0-F1 and F2-F3, F0-F1 and F4, and F2-F3 and F4 groups (all P<0.05). MD value was statistically different between the F0-F1 and F4 groups, and F2-F3 and F4 groups (all P<0.05). However, there was no significant difference in ADC values for all groups (all P>0.05). In addition, mean kurtosis and MD values significantly correlated with the extent of hepatic fibrosis staging (Spearmans rank correlation coefficient, ρ=0.851 and -0.672; P<0.0001). However, ADC values did not reveal a correlation with the extent of hepatic fibrosis staging (ρ=-0.227; P=0.078). According to the ROC analysis for the assessment of no fibrosis (F0), fibrosis (≥F1), and advanced fibrosis (≥F2) and liver cirrhosis, the DKI cut-off values were 0.923, 0.955, and 1.11, respectively. CONCLUSION Using the DKI method with the breath-hold technique in the liver, the stage of hepatic fibrosis can be classified into normal and early hepatic fibrosis, substantial stages, and advanced hepatic fibrosis.

Diffusion kurtosis imaging in the assessment of liver function: Its potential as an effective predictor of liver function

OBJECTIVES: We aimed to determine whether diffusion kurtosis imaging (DKI) analysis with the breath-hold technique can replace liver function results obtained from laboratory tests. METHODS: Patients (n = 79) suspected of having a hepatobiliary disease, and control group without liver diseases (n = 15) were examined with non-Gaussian diffusion-weighted imaging using a 3.0 T magnetic resonance imaging unit. Based on the findings of DKI, various blood serum parameters, including the indocyanine green (ICG) retention rate 15 min after an intravenous injection of ICG (ICG-R15) and mean kurtosis values and Child-Pugh and albumin-bilirubin (ALBI) scores, were calculated. In total, 17 patients were tested using ICG-R15. For evaluating liver function, correlations between the mean kurtosis value and the Child-Pugh score, ALBI score, and ICG-R15 value as indicators of liver function obtained from blood data were assessed using Spearmans rank correlation. In apparent diffusion coefficient as well, we assessed correlations with these indicators. RESULTS: The mean kurtosis value correlated with the Child-Pugh score (Spearmans rank-correlation coefficient, ρ = 0.3992; p < 0.0001). Moreover, the mean kurtosis value revealed a correlation with the ICG-R15 value (Spearmans rank-correlation coefficient, ρ = 0.5972; p = 0.00114). The correlation between the mean kurtosis value and the ALBI score was the poorest among these (Spearmans rank-correlation coefficient, ρ = 0.3395; p = 0.0008). CONCLUSION: Liver function correlating with the Child-Pugh score and ICG-R15 value can be quantitatively estimated using the mean kurtosis value obtained from DKI analysis. DKI analysis with the breath-hold technique can be used to determine liver function instead of performing laboratory tests. ADVANCES IN KNOWLEDGE: Previous studies have not evaluated liver function in vivo using DKI.