Tatsuro Kaminaga

Role of magnetic resonance imaging for evaluation of tumors in the cardiac region

Abstract.The aim of this study was to review the role of MRI in the assessment of heart neoplasm, 25 cases with heart neoplasm (10 myxoma, 6 rhabdomyoma, 5 angiosarcoma, 2 mesothelioma, 1 lymphoma, and 1 fibroma) were examined with MRI and echocardiography. Multislice T1- and T2-weighted spin-echo images and static gradient-echo images were taken in appropriate directions with electrocardiogram gating. Gadolinium enhancement was performed in 21 cases. Transthoracic echocardiography was performed in all cases. Except for the 5 patients with rhabdomyoma, the pathological diagnosis was obtained. MRI proved to be useful for tissue characterization of myxoma, angiosarcoma, mesothelioma, and fibroma in cases with tuberous sclerosis. MRI also proved to be useful for detection of the tumor, depiction of contour, relation with other cardiac structures, in cases with myxoma, angiosarcoma, mesothelioma, lymphoma, and fibroma. In the differential diagnosis, MRI provided important information in cases with myxoma, rhabdomyoma, angiosarcoma, and fibroma. In cases with tumors expanding into the mediastinum, such as mesothelioma and fibroma in this report, MRI was useful in determining the location and border. In cases with tumors adjacent to pericardium, MRI was useful in detecting pericardial invasion. Gadolinium enhancement added useful information in cases with myxoma, rhabdomyoma, angiosarcoma, and mesothelioma. The role of MRI with and without Gd enhancement differs somewhat in individual types of heart neoplasm, and adaptation must be considered in each kind of neoplasm. On the other hand, MRI is an essential examination in all cases with a cardiac mass, which has not been diagnosed, since it may provide useful information for the differential diagnosis.

Both parietal lobes are involved in drawing: a functional MRI study and implications for constructional apraxia

In clinical studies, many researchers have reported that drawing can be disturbed by left or right unilateral parietal lobe damage (constructional apraxia). There seem to be two possible predictions about the cerebral laterality for drawing. The first is that drawing requires both parietal lobes, therefore, a lesion to either side can disrupt drawing. The second is that individuals can differ in laterality: some have only right or left activations, and some have bilateral. To test these predictions, we investigated with functional magnetic resonance imaging (fMRI) the cerebral activation whilst 17 right-handed healthy subjects performed a drawing task. The experiment consisted of two conditions: (1). naming an object in a presented picture and drawing it by using right index finger (DRAWING & NAMING); (2). naming an object in a presented picture (NAMING). We considered the brain regions that had greater activity in the DRAWING&NAMING condition than in the NAMING condition were the neural substrates of drawing. Individual analysis revealed that all subjects showed parietal activation bilaterally. We interpret that the results support the first prediction that both parietal lobes are required for drawing. By calculating the laterality indices of the individual parietal activations, it was found that there were more left dominant subjects than right dominant subjects (left, 12; right, 5). The results are inconsistent with previous studies on the incidence of constructional apraxia. In addition, we found activation in regions that were not previously reported in the literature of constructional apraxia: they are the ventral premotor area and posterior part of inferior temporal sulcus.

Interindividual uniformity and variety of the "Writing center": a functional MRI study.

Our aim is to investigate the neural substrates for writing using fMRI (twenty right-handed subjects). We assumed that common areas involved in both writing with right and left hands are crucial to the central process of writing. We employed Japanese phonograms (Kana), in which phoneme-grapheme conversion would be extremely simple. Brain activation was examined under three conditions: (1) written naming with the right hand (WR), (2) written naming with the left hand (WL), and (3) naming silently (NA). While the comparison of WR to NA (WR>NA) exhibited activation only in the left frontoparietal area, the WL>NA comparison exhibited broader activation than the WR>NA comparison, i.e., the left frontoparietal area except the motor and sensory areas and the right frontoparietal area. A conjunction analysis in SPM2 revealed common areas of activation across the WR>NA and WL>NA comparisons, which are assumed to be crucial to writing. In the group analysis, three areas were found to be activated: the posterior end of the left superior frontal gyrus, which is superior and posterior to Exners center; the anterior part of the left superior parietal lobule; and the lower part of the anterior limb of the left supramarginal gyrus. In the single-subject analysis, whereas the first two of the above three areas were found to be crucial for writing in all individuals, an interindividual inconsistency of involvement with writing was observed in three areas: the lower part of the anterior limb of the left supramarginal gyrus (60% involved); the right frontal region (47%); and the right intraparietal sulcus (47%).

Impact of 16-slice computed tomography in percutaneous coronary intervention of chronic total occlusions

The main reason for failure of percutaneous coronary intervention (PCI) of chronic total occlusion (CTO) is because the calcified plaque prevents the guide wire crossing the occlusion. We aimed to identify the route, and characterize plaque components within CTO, using 16‐slice computed tomography (MSCT). Twenty three angiographic CTO in 22 patients (mean age 69 ±± 5 years, 17 males) were included. All patients had undergone MSCT prior to PCI. Images were analyzed for lesion visibility and plaque characteristics of CTO. The presence and location of calcified plaque within the CTO were systematically assessed. Each lesion was classified as a noncalcified, moderately calcified, or exclusively calcified plaque. Procedural failure was defined as the inability to cross a guide wire through the occlusion. All coronary routes of CTO segment were visualized. MSCT revealed three markedly bent CTO segments (13.0%), which could not be identified by coronary angiography only. Calcified plaques were detected in 30 lesions of 19 CTO segments (82.6%), but were not detected in the other four. The majority of calcified plaque was located in the proximal lesion, or both proximal and distal lesions. Fifteen out of 30 calcified lesions (50.0%) were exclusively calcified plaques. Overall procedural success was obtained in 21 CTOs (91.3%). MSCT can accurately identify the route of the CTO segment and evaluate both distribution and amount of the calcified plaque within it. Even with the complicated and/or calcified lesions, PCI success rate was excellent under MSCT guidance. MSCT should become a useful tool in PCI of CTO.

Detection of cerebral blood flow changes during repetitive transcranial magnetic stimulation by recording hemoglobin in the brain cortex, just beneath the stimulation coil, with near-infrared spectroscopy.

Many studies measured cerebral blood flow changes in the stimulated primary motor cortex during repetitive transcranial magnetic stimulation (rTMS) using PET, SPECT, and fMRI; however, most of these procedures are associated with problems related to temporal resolution and magnetic field artifacts that are produced by rTMS. In this study of 12 healthy right-handed volunteers, we measured the hemoglobin (Hb) concentration change in the stimulated primary motor cortex during and after rTMS using rTMS coil and near infrared spectroscopy (NIRS) with high temporal sampling (every 125 ms). The left primary motor cortex that controls the right first dorsal interosseus (FDI) muscle was stimulated 10 times with an angle figure-of-eight coil at a frequency of 0.5 or 2 Hz, at intensity of 80% or 120% of resting motor threshold (RMT). We used 4 stimulus conditions: (1) 2 Hz-120% RMT, (2) 2 Hz-80% RMT, (3) 0.5 Hz-120% RMT, and (4) 0.5 Hz-80% RMT. We observed small intensity-dependent increments in total- and oxy-Hb concentrations around 5 s at the 120% RMT condition. Greater decrements in total- and oxy-Hb concentrations and increment of deoxy-Hb concentration were observed during and after rTMS at all conditions, both at the supra-threshold and sub-threshold stimulus intensities. Our results emphasize the suitability of NIRS combined with rTMS for detecting changes in cerebral blood flow.

Accuracy of attenuation measurement of vascular wall in vitro on computed tomography angiography: Effect of wall thickness, density of contrast medium, and measurement point.

Objectives:We sought to assess the effects of measurement point, wall thickness, and intravascular density of contrast material on attenuation measurement of vascular wall. Materials and Methods:We used vascular models (actual attenuation value of the wall: 83 HU) with wall thicknesses of 1.5, 1.0, or 0.5 mm, filled with contrast material of 254, 325, or 400 HU. The 9 vascular models were fixed in an oil-filled container and scanned with a 16-detector computed tomography. The wall attenuation values were measured at 1 point for 0.5-mm thickness models, 3 for 1.0-mm thickness models, and 5 for 1.5-mm thickness models with the same interval of 0.25 mm. Total 20 measurements were done for each point. Results:For 1.0-mm and 1.5-mm thickness models, wall attenuation progressively increased as the measurement points approached the lumen (P < 0.0001). At all the measurement points for 0.5-mm and 1.0-mm thickness models and the 2 inner measurement points for 1.5-mm thickness models, the densities of contrast material affected the wall attenuations significantly (P < 0.0001). At the midportion for 1.5-mm thickness models, the wall attenuations were not affected by the densities of the contrast material (P = 0.6301), and were 65–68 HU. Conclusions:The effects of the intravascular density of contrast material, measurement point, and wall thickness should be considered in the attenuation measurement of the wall.

Activation of supplementary motor area during imaginary movement of phantom toes.

To evaluate changes in the human cerebral cortex after lower limb amputation, we studied repetitive toe movements using functional magnetic resonance imaging. The subject did not experience any phantom pain but had a vivid sensation of the phantom limbs presence and was able to imagine the movement of her phantom toes and ankle. Actual movement of her normal limb activated the contralateral supplementary motor area (SMA), the primary motor cortex (M1), and the primary somatosensory cortex (S1). Movement of her phantom limb activated the contralateral SMA and the M1. Imaginary movement of her normal toes without actual movement activated the contralateral SMA. The slice level that was activated by the movement of the phantom limb was shifted 8 mm caudally, suggesting that cortical reorganization had occurred after the lower limb amputation.

Neural consequences of somatosensory extinction: an fMRI study.

There are currently two main interpretations proposing mechanisms underlying tactile extinction: sensory and attention deficit hypotheses. Kinsbourne proposed an opponent processor model to support the attention deficit hypothesis. He insisted that bilateral hemispheres interact reciprocally through contralaterally oriented vectors, and in patients presenting extinction, balance is impaired, causing inattention. From Kinsbourne’s point of view, extinction is not caused by sensory disturbance but inattention, therefore even in extinction patients, simultaneous bilateral stimuli should reach the bilateral primary sensory cortices (SI). Using functional magnetic resonance imaging (fMRI), tactile stimuli were administered to both hands of healthy subjects as well as a tactile extinction patient. The patient with tactile extinction extinguished right palm stimuli following simultaneous palm stimulation. During the fMRI study, we gave tactile stimuli to the right palm, the left palm, and simultaneously to both palms. In normal subjects, simultaneous bilateral stimuli activated the bilateral SI and bilateral secondary sensory cortices (SII). In the patient with right tactile extinction, simultaneous bilateral stimuli activated the bilateral SI along with the bilateral SII and right superior parietal lobule. Our study suggests that activation of SI is insufficient to engender an awareness of sensory stimuli. From the view point of Kinsbourne, stimulus driven activity in one hemisphere suppresses activity in the other hemisphere via callosal connections. Our results support the notion that an undamaged superior parietal lobule in the patient with tactile extinction suppresses the damaged parietal lobe function and causes extinction.

Regional cerebral blood flow abnormalities in patients with kawasaki disease.

Purpose: Kawasaki disease (KD) is an acute febrile disorder of unknown etiology. Brain single-photon emission computed tomography (SPECT) and magnetic resonance imaging (MRI) help in detecting regional cerebral blood flow abnormalities and brain damage. The usefulness of SPECT and MRI in patients with KD was evaluated. Materials and Methods: All 22 patients with KD underwent brain SPECT using Tc-99m-hexamethyl propylene amine oxime from 6 days to 3 years after onset, and 8 patients underwent brain MRI. Of the 22 patients, 4 had neurologic symptoms. Case 1 showed prolonged apnea; case 2, prolonged disturbance of consciousness; and cases 3 and 4 generalized tonic-clonic seizures. Initial brain SPECT showed localized hypoperfusion in 4 and 13 patients with and without neurologic symptoms, respectively. Results: All patients with neurologic symptoms underwent follow-up SPECT; localized hypoperfusion was detected between 1- and 6-month follow-up in 3 of these patients. Six patients without neurologic symptoms underwent follow-up SPECT. Localized hypoperfusion was detected at approximately 1- to 11-month follow-up in 4 of these patients. Diffusion-weighted imaging revealed abnormal high-intensity areas in the corpus callosum in case 1. Case 2 showed a bilateral chronic subdural hematoma with decreased size and ischemic changes, and case 3 showed bilateral hippocampal atrophy and left hippocampal sclerosis. Conclusions: Because the occurrence of localized hypoperfusion is possibly not restricted to only the acute phase in KD, brain SPECT and MRI should also be performed in KD patients with neurologic symptoms.

Feasibility of multiparametric prostate magnetic resonance imaging in the detection of cancer distribution: histopathological correlation with prostatectomy specimens

Purpose To prevent overtreatment, it is very important to diagnose the precise distribution and characteristics of all cancer lesions, including small daughter tumors. The purpose of this study was to evaluate the efficacy of T2-weighted magnetic resonance imaging (T2W), diffusion-weighted magnetic resonance imaging (DWI), magnetic resonance spectroscopy (1H-MRS), and prostate biopsy (PBx) in the detection of intraprostatic cancer distribution. Methods All patients underwent T2W, DWI, 1H-MRS, and PBx followed by radical prostatectomy (RP). Individual prostates were divided into 12 segmental regions, each of which was examined for the presence or absence of malignancy on the basis of T2W, DWI, 1H-MRS, and PBx, respectively. These results were compared with the histopathological findings for RP specimens. Results We included 54 consecutive patients with biopsy-proven prostate cancer (mean age, 62.7 years; median prostate-specific antigen level, 5.7 ng/mL) in this study. We could detect cancer in 247 of 540 evaluable lesions. The area under the receiver operator characteristic curve analysis yielded a higher value for DWI (0.68) than for T2W (0.65), 1H-MRS (0.54), or PBx (0.56). In 180 cancerous regions of RP specimens with false-negative PBx results, T2W+DWI had the highest positive rate (53.3%) compared with that of each sequence alone, including T2W (45.6%), DWI (41.1%), and 1H-MRS (30.0%). Conclusions Multiparametric magnetic resonance imaging (T2W, 1H-MRS, DWI) enables the detection of prostate cancer distribution with reasonable sensitivity and specificity. T2W+DWI was particularly effective in detecting cancer distribution with false-negative PBx results.