Tagged MR imaging of intracranial aneurysm models.

We used tagged MR imaging to investigate the flow in two lateral and two terminal saccular intracranial aneurysm models of different neck sizes. Imaging was performed with a 1.5-T superconducting MR system using 2D fast spatial modulation of magnetization (SPAMM) sequences with an intersegmental delay of 25 milliseconds. The flow in the saccular aneurysm models varied with the shape and size of the neck: flow was faster in wider-necked aneurysms than in those with narrower necks.

Magnetization transfer contrast of various regions of the brain in liver cirrhosis.

BACKGROUND AND PURPOSE: T1-weighted MR images show high signal intensity in the pallidum of many patients with liver cirrhosis. The purpose of this study was to evaluate quantitative changes in MR signals in patients with liver cirrhosis by using the magnetization transfer technique. METHODS: Magnetization transfer ratios were measured in seven different regions of the brain in 37 patients with liver cirrhosis and in 37 healthy volunteers. RESULTS: The magnetization transfer ratios in patients with liver cirrhosis were significantly lower than those in control subjects in the globus pallidus, putamen, thalamus, corona radiata, and subcortical white matter. CONCLUSION: Abnormal magnetization transfer ratios may be found in otherwise normal-appearing cerebral regions.

Detection of pyramidal tract lesions in amyotrophic lateral sclerosis with magnetization-transfer measurements.

PURPOSE: To determine the presence of small lesions in the pyramidal tract in patients with amyotrophic lateral sclerosis (ALS) by using magnetization-transfer (MT) measurements and MR imaging. METHODS: MT ratios (MTRs) were measured in the posterior limb of the internal capsule in nine patients with ALS and in nine healthy volunteers. RESULTS: The mean value of MTRs (%) in patients with ALS was 15.76 +/- 1.48, while that of the control subjects was 19.83 +/- 1.54. The difference was statistically significant. CONCLUSIONS: MT measurements are useful for detecting abnormalities associated with degeneration of the pyramidal tract in patients with ALS.

Saturation transfer ratio imaging in invasive ductal carcinomas of the breast.

A prospective study was performed to investigate the correlations between saturation transfer ratio (STR) and histologic parameters of invasive ductal carcinomas in human breast. The histologic parameters investigated were the extent of fibrosis in the intercellular matrix, dysplastic changes of nuclei, and mitotic index. Twenty-seven patients with breast carcinoma were examined using an off-resonance saturation pulse in conjunction with conventional field-echo T(1)-weighted imaging at frequency offsets of 448 Hz and 1200 Hz from water resonance. The values of STR at frequency offset of 1200 Hz (STR(1200)) increased from non-scirrhous carcinoma to scirrhous carcinoma. Although STR(1200) showed correlation with the extent of fibrosis in the intercellular matrix (p<0.01, n = 27), they did not correlate with the dysplastic changes of nuclei or mitotic index. On the other hand, the values of STR at frequency offset of 448 Hz (STR(448)) demonstrated close correlation to dysplastic changes of nuclei and mitotic index (p<0.01, n = 27). STR(1200) correlates with the structural characteristics and STR(448) correlates with the nature of malignant cells with regard to nuclear dysplasia and mitotic potential.

New image network system and its informational background at Yamada Red Cross Hospital.

To assess the relationship between the numbers of images and films under the influence of the recent growth in imaging technology in a general hospital, we made a survey of 4424 and 4959 X-CT examinations conducted in the first halves of 1994 and 1995, respectively. We made a survey of 2344 MRI examinations conducted in the first half of 1995 also. This study revealed that the increase in the number of images obtained with latest imaging modalities was rather high compared to the number of examinations and it was difficult to print all of the images obtained. But the image network system, where distributed diagnostic workstations and network cameras formed important parts of the system, could solve or reduce some difficulties and produce a new service for out-patients. In this study, we show the newly-introduced image network system into Yamada Red Cross Hospital, its informational background and the results of the routine use of the system.

Real-time radiology--new concepts for teleradiology.

We propose two new concepts for teleradiology: 'real-time radiology' and 'seamless operation of a workstation to view images from both local and remote hospitals'. In this paper, we describe an experimental real-time radiology system with a new multimedia diagnostic workstation, which has been established under teleradiology concepts and can be used for cooperative diagnosis by interchanging radiographic images bilaterally in real-time during an audio-visual discussion. The clinical evaluation of real-time radiology using a newly developed diagnostic workstation demonstrated the system to be practical and routinely available to enhance the radiological diagnostic quality of teleradiology.

New non-invasive technique to visualize three-dimensional anatomical structures of myelinated white matter tracts of human brain in vivo.

We have developed a new non-invasive technique to visualize three-dimensional anatomical structures of myelinated white matter tracts of the human brain in vivo. The basic principle of our idea is the combination of the magnetic resonance (MR) imaging technique, which represents the myelinated white matter tracts as hyperintense signal areas, and the post-image processing technique, which extracts only hyperintense areas on the image. The intravoxel incoherent motion imaging sequence was used for the former step. The maximum intensity projection method, on the other hand, was utilized for the latter step. To examine the clinical usefulness of the idea, normal volunteers and selected patients with paralysis were investigated on a 1.5 Tesla MR system. The structure of white matter tracts of normal volunteers was found to be in good agreement with known anatomy. The structure of the nerve fiber system of patients with paralysis, on the other hand, reflected some abnormalities of the nerve fibers and correlated with clinical symptoms. Some results of clinical examinations with our proposed technique showed great promise for the study of neuroanatomy and neuroradiology.

Basic studies on the equivalent cross-relaxation rate imaging (equivalent CRI)--phantom studies.

We have studied saturation transfer in hydrophilic, cross-linked copolymer gels from irradiated polymer protons to observed water protons, using f2 (ppm) profiles of [1 - (I(infinity)/I(0))], [(I(0)/I(infinity)) - 1] or 1/T(IS)(H2O), where I(0) and I(infinity) are the longitudinal magnetization of the observed water protons before and after long-time-f2-irradiation on polymer protons, respectively, and 1/T(IS)(H2O) is the cross-relaxation rate. (A) [1 - (I(infinity)/I(0))] (magnetization transfer ratio, MTR) was used in magnetic resonance imaging (MRI) as the MTR imaging. 1/T(IS)(H2O) (cross-relaxation rate) was used in the imaging of the magnetization transfer rate constant. This method was quite time-consuming compared with MTR imaging. However, f2 (ppm) profiles of [(I(0)/I(infinity)) - 1] correlated well with corresponding profiles of 1/T(IS)(H2O), because [(I(0)/I(infinity)) - 1] is equal to 1/[T(IS)(H2O)/T1(H2O)]. These results lead us to the conclusion that [(I(0)/I(infinity)) - 1] might be applicable to cross-relaxation rate (CR)-like imaging, i.e. equivalent CRI. (B) W (%) (dry weight) profiles of [(I(0)/I(infinity)) - 1] and 1/T(IS)(H2O), obtained by near-resonance f2-irradiation, seem to indicate participation of molecular rigidity and an amount of bound water. However, those values, monitored with off-resonance f2-irradiation, seem to be independent of monomer composition and to indicate mainly participation of rigidity, i.e. W (%) of copolymer gels.

[Quantitative evaluation of magnetization transfer ratio in irradiated breast with breast conservation therapy].

To assess the late effects of radiotherapy, magnetization transfer was evaluated in 2 patients with breast conservation treatment and in 4 patients without treatment. The magnetization transfer ratios (MTRs) were measured from a pair of images obtained by the conventional SPGR pulse sequence and the MT-prepared SPGR sequence on a 1.5-TMR system. The MTR values of irradiated breast were higher than those of non-irradiated breast. The difference in MTR between them was considered to represent tissue change due to irradiation. We showed that MTR is a useful parameter in estimating the late effects of radiotherapy.

[Changes of magnetization transfer ratio according to rat brain development].

We assessed the age-related changes in magnetization transfer ratio (MTR) value and the ratio of water content in rat brain (frontal lobe and pons) during normal development. All studies were done on 42 normal Wistar rats. MTR was calculated by using the equation (Moff-Mon)/Moff, where Moff and Mon were the measured signal intensities on the conventional and MT-prepared SPGR images, respectively. The ratios of water content were measured by comparing the wet weight with the dry weight of the frontal lobe and the pons, which were extracted from a rat brain soon after MTR measurements. The ratio of water content was calculated by using the equation 100 x (wet weight-dry weight)/wet weight (%). The ratio of water content decreased markedly during the first 30 days, but the decrease was very slight there after both in the frontal lobe and the pons. The change in MTR was similar to that of the ratio of water content, though the direction of change was opposite. Statistically significant inverse relationships existed between MTR and the ratio of water content both in the frontal lobe and the pons. MTR could be a new parameter with which to assess brain development.

Uterine neoplasms: magnetization transfer analysis of MR images.

PURPOSE: To determine whether the magnetization transfer effects seen at fast spin-echo (SE) magnetic resonance (MR) imaging provide additional information in the diagnosis of uterine neoplasms. MATERIALS AND METHODS: MR images were obtained in 58 subjects with a normal uterus, 27 patients with cervical carcinoma (17 before therapy; 10 after irradiation), 10 with endometrial carcinoma, and five with endometrial hyperplasia. The magnetization transfer ratios (MTRs) were calculated by measuring the signal intensity on the central section of multisection fast SE images (15 sections) and that on a single-section fast SE image (5,000/136 [repetition time msec/echo time msec]). The additional imaging time required for MTR measurement was 4 minutes. RESULTS: Conspicuity of lesions and normal zonal anatomy was improved with single-section fast SE. The mean MTR in untreated cervical carcinoma (37.6% +/- 4.2 [standard deviation]) showed a statistically significant increase relative to that in irradiated cervical carcinoma (24.5% +/- 5.1, P < .01), normal cervical stroma (23.8% +/- 6.7, P < .01), or normal endocervix (24.2% +/- 7.3, P < .01). The mean MTR in endometrial carcinoma (34.5% +/- 3.6) was significantly higher than that in endometrial hyperplasia (25.5% +/- 1.5, P < .01) or normal endometrium (24.3% +/- 3.6, P < .01). CONCLUSION: Single-section fast SE imaging provides better lesion contrast than multisection fast SE imaging and enables quantification of the MTRs in uterine neoplasms.

Serial P-31 MR spectroscopy after fructose infusion in patients with chronic hepatitis.

Serial changes in phosphorus metabolites after intravenous administration of fructose were compared between five healthy volunteers and five patients with chronic hepatitis by means of phosphorus-31 magnetic resonance (MR) spectroscopy. P-31 spectra were obtained every 5 minutes after intravenous drip infusion of 20% fructose at a dose of 0.5 g/kg of body weight. In the healthy volunteers, phosphomonoesters (PME) increased to 338% +/- 76% of the preadministration value at 15-20 minutes. Inorganic phosphate (Pi) was depleted in the first 15 minutes, then rebounded to 260% +/- 67% of the initial value. beta-adenosine triphosphate decreased to less than 50% of its initial value and then gradually recovered. In patients with chronic hepatitis, the increase of PME at 15-20 minutes (151% +/- 49% of the preadministration value) was significantly less than that in healthy volunteers (P less than .05). In addition, the rebound of Pi at 35-40 minutes (126% +/- 42%) was significantly less than that in healthy volunteers (P less than .05). In conclusion, P-31 MR spectroscopy with fructose administration is valuable in the functional evaluation of diffuse liver diseases.

Single photon emission computed tomography to determine effective hepatic blood flow and intrahepatic shunting.

The noninvasive determination of effective hepatic blood flow, intrahepatic shunted blood flow, intrahepatic shunt index, and total hepatic blood flow was investigated by using the sequential single photon emission computed tomography. This method was performed for a period of 10 minutes following an intravenous injection of 99mTc-(Sn)-N-pyridoxyl-5-methyltryptophan and a venous blood sampling. This study comprised 8 healthy volunteers, 16 patients with chronic hepatitis, and 33 patients with liver cirrhosis. The intrahepatic shunt index measured with this method coincided with the intrahepatic shunt index determined by catheterization, indicating the high reliability of this procedure. The effective hepatic blood flow in patients with liver cirrhosis was significantly lower than that in the healthy controls and the chronic hepatitis group. The intrahepatic shunted blood flow was significantly higher in patients with liver cirrhosis compared with the flow in healthy controls. The intrahepatic shunt index was also significantly higher in patients with liver cirrhosis compared with the index of healthy controls and those with chronic hepatitis. No substantial differences were noted in the total hepatic blood flow among the three groups. The effective hepatic blood flow, the intrahepatic shunted blood flow, and the intrahepatic shunt index, correlated with the serum albumin concentration, the serum cholinesterase level, and the plasma indocyanine green attenuation rate. From these results, it was concluded that the present procedure constitutes a reliable and effective method for the noninvasive determination of hepatic blood flows. Consequently, it will be of high clinical value for assessing the functional and the pathological alterations of the liver.

Hepatic cirrhosis: magnetisation transfer contrast in the globus pallidus.

The magnetisation transfer ratio (MTR), a quantitative tissue characteristic, and the pallidal index were measured in the globus pallidus of 37 patients with hepatic cirrhosis and 37 control subjects. The MTR decreased with severity of the disease, as indicated by the serum total bililubin, indocyanine green 15-min retention rate, and plasma ammonia. The pallidal index correlated significantly with haematological parameters, although the correlation coefficients tended to be lower than those between MTR and haematological parameters. This change in MTR corresponded to the results of the manganese chloride experiments. T1 shortening in the pallidum of patients with cirrhosis is presumably caused by paramagnetic effects, and possibly attributed to manganese deposition.

[MR tractography--visualization of structure of nerve fiber system from diffusion weighted images with maximum intensity projection method].

We developed a new noninvasive technique to visualize the anatomical structure of the nerve fiber system in vivo, and named this technique magnetic resonance (MR) tractography and the acquired image an MR tractogram. MR tractography has two steps. One is to obtain diffusion-weighted images sensitized along axes appropriate for depicting the intended nerve fibers with anisotropic water diffusion MR imaging. The other is to extract the anatomical structure of the nerve fiber system from a series of diffusion-weighted images by the maximum intensity projection method. To examine the clinical usefulness of the proposed technique, many contiguous, thin (3 mm) coronal two-dimensional sections of the brain were acquired sequentially in normal volunteers and selected patients with paralyses, on a 1.5 Tesla MR system (Signa, GE) with an ECG-gated Stejskal-Tanner pulse sequence. The structure of the nerve fiber system of normal volunteers was almost the same as the anatomy. The tractograms of patients with paralyses clearly showed the degeneration of nerve fibers and were correlated with clinical symptoms. MR tractography showed great promise for the study of neuroanatomy and neuroradiology.

[Hard-copy (film) versus soft-copy (CRT) reading performance between compressed and uncompressed images: SOLs in abdominal CT images].

The objective of this study was to examine the feasibility of soft-copy (CRT) reading and suitable compression. Forty abdominal CT images with a space-occupying lesion (SOL) in liver and 40 normal images were selected for receiver-operating-curve (ROC) analysis. Each image was compressed by JPEG extended mode into 1/10 its original capacity, and then an expanded image was printed on film. Ten radiologists evaluated the presence of liver SOLs (primary and secondary tumors) on soft-copy (CRT) and hard-copy (film) images. Each radiologist reviewed four types of images (original and compressed hard-copy and original and compressed soft-copy images). Values of the area under the curve in the various ROC analyses were 0.858 (FILM) and 0.842 (CRT) for original images and 0.879 (FILM) and 0.846 (CRT) for compressed images. The results of ROC analysis showed better reading performance with hard-copy than soft-copy images, but the difference was not statistically significant. Compressed images showed a higher value (0.879) than original images (0.858), a difference that was statistically significant (p < 0.029) by the paired t-test but not by the jackknife method. The results indicate that soft-copy reading is a clinically acceptable alternative to hard-copy reading. We have had no difficulty in reading abdominal CT images compressed to 1/10 of the original size by the JPEG method. This study was supported in part by a grant from the Japanese Ministry of Health and Welfare.