Naozo Sugimoto

Age‐dependent brain temperature decline assessed by diffusion‐weighted imaging thermometry

Brain metabolism declines with age, but cerebral blood flow (CBF) is less age dependent. We therefore hypothesized that the brain temperature would decline with age, and measured the temperatures of the lateral ventricles in healthy volunteers. Diffusion‐weighted imaging (DWI) data from 45 healthy volunteers [mean (± standard deviation) age, 30.6 ± 8.66 years; range, 19–56 years] were used for this study. The temperature of water molecules is directly related to the diffusion coefficient, so that the temperature of cerebrospinal fluid can be measured using DWI. Temperature was calculated using the equation, T ( °C) = 2256.74/ln(4.39221/D) – 273.15, where D is the diffusion coefficient. The lateral ventricles were manually extracted by an experienced neuroradiologist on b0 images. The mean ventricular temperature was determined from the distribution function of the temperature of all selected voxels. The mean lateral ventricular temperature in healthy volunteers showed a linear decrease with age (correlation coefficient R2 = 0.8879; p < 0.01), presumably caused by an asynchronous decline in brain metabolism and CBF. DWI‐based thermometry demonstrates that ventricular temperature declines with the normal aging process. Further study is warranted to define the relationships between temperature, metabolism and circulation. Copyright

Moyamoya patients exhibit higher brain temperatures than normal controls.

The balance between heat production (metabolism) and heat removal (blood flow) helps in keeping the temperature of the brain constant. In patients with moyamoya disease, this balance may be disturbed. The purpose of this study was to assess the thermal pathophysiology of the brain in patients with moyamoya disease. The study included 12 consecutive patients with moyamoya disease and 10 controls. Temperature was measured by image postprocessing of diffusion-weighted images. Our noninvasive thermometry showed that the ventricular temperature of moyamoya disease patients was higher than that of normal controls. The mean temperature difference of 1.1°C between the two groups was significant. Patients with moyamoya disease tend to have elevated ventricular temperatures, which may represent a mismatch between cerebral metabolism and perfusion.

Automatic extraction of coronary artery tree on coronary angiograms by morphological operators

This paper presents a new method of fully automatic detection of the coronary artery tree by using several morphological filters. The contrast between coronary artery and background is enhanced by the morphological Top-Hat operation and subtraction of the result from the original image. Pixels which are obviously out of the coronary artery are removed by the half-threshold processing and the erosion operation. The labeling according to gray level difference is done on the half-threshold image so as to extract the candidates of the coronary artery. The main part of the coronary artery is extracted as the biggest area among the labeled areas. Because the tip parts of the coronary artery are narrower than the area of main coronary artery, multi-structure elements of Top-Hat operator are used repeatedly to enhance the narrow artery. The morphological watershed transform is used to detect the edge of coronary artery on the gradient image of the original image. We have tried the method on several images. Results show that the method is efficient to detect the artery tree automatically even on a less contrast image.

Detailed motion analysis of the left ventricular myocardium using an MR tagging method with a dense grid

Detailed analysis of myocardial deformation through a whole cardiac cycle was accomplished using a tagging method with a high‐density grid. Four sets of tagged images with a 4‐mm‐spacing grid were measured by generating four tagging pulses arranged at regular intervals in the cardiac cycle. Through each set of images, tag intersections were tracked semi‐automatically. The estimated motions of tag intersections were concatenated so that sequential positions of myocardium were connected through a whole cardiac cycle. In vitro evaluation of the precision of this technique showed that the mean error of tracked 4‐mm tag intersections was less than 0.47 ± 0.17 mm, even on the quite low‐contrast images, and the concatenation error caused by double concatenation was comparable to the interpolation error in the subendocardial area obtained with 8‐mm tag intersection motion. The small difference between the two mean distance curves of the in vivo evaluation indicated that the method is useful for analyzing heart wall abnormalities. Magn Reson Med 44:73–82, 2000.

Calculation methods for ventricular diffusion‐weighted imaging thermometry: phantom and volunteer studies

A method for the measurement of temperature in the lateral ventricle using diffusion‐weighted imaging (DWI) has been proposed recently. This method uses predetermined arbitrary thresholds, but a more objective method of calculation would be useful. We therefore compared four different calculation methods, two of which were newly created and did not require predetermined thresholds. A rectangular polyethylene terephthalate bottle (8 × 10 × 28 cm3) was filled with heated water (35.0–38.8 °C) and used as a water phantom. The DWI data of 23 healthy subjects (aged 26–75 years; mean ± standard deviation, 50.13 ± 19.1 years) were used for this study. The temperature was calculated using the following equation: T(°C) = 2256.74/ln(4.39221/D) − 273.15, where D is the diffusion coefficient. The mean ventricular temperature was calculated by four methods: two thresholding methods and two histogram curve‐fitting methods. As a reference, we used the temperature measured at the tympanic membrane, which is known to be approximately 1 °C lower than the brain temperature. The averaged differences in temperature between mercury thermometry and classical predetermined thresholding methods for the water phantom were 0.10 ± 0.42 and 0.05 ± 0.41 °C, respectively. The histogram curve‐fitting methods, however, yielded temperatures a little lower (averaged differences of −0.24 ± 0.32 and −0.14 ± 0.31 °C, respectively) than mercury thermometry. There was very little difference in temperature between tympanic thermometry and classical predetermined thresholding methods (+0.01 and −0.07 °C, respectively). In humans, however, the histogram curve‐fitting methods yielded temperatures approximately 1 °C higher (+1.04 °C and +1.36 °C, respectively), suggesting that temperatures measured in this way more closely approximate the true brain temperature. The histogram curve‐fitting methods were more objective and better matched the estimated brain temperature than did classical predetermined thresholding methods, although the standard deviation was wider in the former methods. Copyright

Preoperative and intraoperative image processing for assisting endovascular stent grafting

Recent development in interventional radiology enables minimally invasive treatment of aortic aneurysm: endovascular stent grafting. We report image processing method in preoperative planning and intraoperative guidance for assisting endovascular stent grafting. In preoperative planning, it is necessary to design stent graft suitable for each clinical case. Thus we present shape measurement method of aneurysmal aorta for computer assisted design of stent graft. In stent grafting, fluoroscopic image is used as intraoperative image for visualizing lesion and interventional device. As fluoroscopic image is a two-dimensional (2D) image, a doctor has to imagine three-dimensional (3D) shape of aneurysmal aorta. For intraoperative guidance, it is useful to register preoperative 3D CT image with intraoperative 2D fluoroscopic images. We present intraoperative 3D/2D registration method for assisting endovascular stent grafting and show application result to clinical data.

Fuzzy inference filter and morphological operators for short circuits detection in printed circuit board

Surface mounting technology (SMT) is one of the most common techniques for the production of printed circuit board (PCB). During manufacturing process, especially during soldering process, faults, such as short circuits, may happen. For a good efficiency of the production line an automatic system for faults recognition is suitable. In this paper we propose a method based on fuzzy logic inference, for short circuit detection in X-ray images of printed circuit boards. The images are acquired with a digital laminographic technique, in particular with HP 5DX system. We present a fuzzy rule based system that is able to enhance solder joints from the other objects in the laminographic images, such as wire lines and other electronic devices mounted on the bottom side of boards. Fuzzy system results are compared with the outputs of gray scale morphological filter. The fuzzy rule based filtering presents efficiency, robustness and a relative low computational cost. The system presented consists of only two inputs and six rules and is based on the Sugeno-Takagi fuzzy model. Once solder joints enhancement is performed, the image is converted in binary format and an a priori number of binary erosions is performed in order to detect short-circuits.

Registration of Preoperative CTA and Intraoperative Fluoroscopic images for Assisting Aortic Stent Grafting

We investigated a registration method between preoperative 3D-CTA and intraoperative fluoroscopic images during intervention. Our final goal is assisting endovascular stent grafting for aortic aneurysm. In our method, DRR (Digitally Reconstructed Radiograph) are generated by voxel projection of 3D-CTA after extracting an aorta region. By increasing/decreasing CT value in the aorta region of CTA, DRR with/without contrast media injection are obtained. Subsequently we calculate matching measures between DRR and fluoroscopic images iteratively by changing imaging parameters. The most similar DRR to fluoroscopic image is selected. We investigated characteristics of several matching measures using simulated fluoroscopic images. From simulation results, we use M-estimator of residual in our method. From an application example to clinical data, registration was successfully applied by M-estimator of residual.

Automated temperature calculation method for DWI-thermometry: The usefulness of LV probability map on healthy subjects

Diffusion-weight imaging (DWI) has already been incorporated as a regular sequence for patients. If DWI could indicate brain temperature without a complicated procedure, such information may greatly contribute to initial diagnosis. The temperature (T: °C) was calculated using the following equation form the diffusion coefficient (D): T= 2256.74/ln (4.39221/D) - 273.15. The cerebrospinal fluid region for automated temperature computation was segmented by lateral ventricle probability map which was constructed from 46 healthy volunteers. No significant differences were seen between temperatures using the proposed method and the manually segmented. The proposed method of fully automated deep brain temperature computation from DWI may prove feasible for application in MRI consoles.

DWI based thermometry: The effects of b-values, resolutions, signal-to-noise ratio, and magnet strength

Among MR methods, the most clinically applicable temperature measurement method at deep brain might be the diffusion-weighted image (DWI) thermometry. Although only applicable to cerebrospinal fluid (CSF), it is thought to be potentially useful in assessing the thermal pathophysiology of the brain in both patients and healthy subjects. The purpose of this study was to investigate the effects of b-value, pixel resolution, magnet strength and signal to noise ratio (SNR) for the DWI-thermometry with healthy volunteer. Formerly, an ADC from b=0 and b=1000 has been thought to be useful for diffusion thermometry, this study revealed b=200 to 800 was more appropriate for DWI thermometry. The SNR was strongly affected the results of DWI thermometry.