Shigeru Sanada

Frequency analyses of CSF flow on cine MRI in normal pressure hydrocephalus

Abstract. Our objective was to clarify intracranial cerebrospinal fluid (CSF) flow dynamics in normal-pressure hydrocephalus (NPH). Frequency analyses of CSF flow measured with phase-contrast cine MRI were performed. The CSF flow spectra in the aqueduct were determined in patients (n=51) with NPH, brain atrophy or asymptomatic ventricular dilation (VD), and in healthy volunteers (control group; n=25). The changes in CSF flow spectra were also analyzed after intravenous injection of acetazolamide. Moreover, a phase transfer function (PTF) calculated from the spectra of the driving vascular pulsation and CSF flow in the aqueduct were assessed. These values were compared with the pressure volume response (PVR). The amplitude in the NPH group was significantly larger than that in the VD or control group because of a decrease in compliance. The phase in the NPH group was significantly different from that in either the VD or the control group, but no difference was found between the VD and control groups. The amplitude increased in all groups after acetazolamide injection. The PTF in the NPH group was significantly larger than in the control group, and a positive correlation was noted between PTF and PVR. Frequency analyses of CSF flow measured by cine MRI make it possible to noninvasively obtain a more detailed picture of the pathophysiology of NPH.

Sonographic Appearance of the Normal Appendix in Adults

To evaluate the sonographic visualization of the normal adult appendix, a large series of sonographic images from consecutive asymptomatic patients was analyzed.

Development of Perfusion CT Software for Personal Computers

RATIONALE AND OBJECTIVESnThe authors developed software for creating quantitative maps of arterial and portal perfusion in the upper abdominal organs on personal computers. The image quality of these perfusion computed tomographic (CT) images was visually evaluated.nnnMATERIALS AND METHODSnIn 58 patients (38 men, 20 women; mean age, 63.9 years +/- 11.9; range, 22-85 years) with various diseases of the upper abdomen, 91 single-section dynamic CT studies were obtained. The data were transferred on-line to a personal computer, and quantitative maps of arterial and portal perfusion were created by means of the maximum-slope method. Perfusion CT images were reviewed by a radiologist and a radiation technologist, and image quality was rated according to a four-category scoring system (1 = good quality, 2 = moderate, 3 = poor, 4 = images could not be created).nnnRESULTSnArterial perfusion CT images could be created in 81 (89%) of 91 examinations, and 74 images (81%) were scored as 1 or 2. Portal perfusion CT images could be created in 60 (68%) of 88 examinations, in which a portal trunk was included in the section, and 33 of them (38%) were scored as 1 or 2. Patient motion during dynamic CT sequences resulted in poor image quality in seven arterial and 27 portal perfusion images.nnnCONCLUSIONnPerfusion CT can combine quantitative perfusion maps with good anatomic detail in one image, although patient movement frequently degrades image quality in portal perfusion CT.

Breathing chest radiography using a dynamic flat-panel detector combined with computer analysis.

Kinetic information is crucial when evaluating certain pulmonary diseases. When a dynamic flat-panel detector (FPD) can be used for a chest examination, kinetic information can be obtained simply and cost-effectively. The purpose of this study was to develop methods for analyzing respiratory kinetics, such as movement of the diaphragm and lung structures, and the respiratory changes in x-ray translucency in local lung fields. Postero-anterior dynamic chest radiographs during respiration were obtained with a modified FPD, which provided dynamic chest radiographs at a rate of 3 frames/s. Image registration for correction of physical motion was followed by measurement of the distance from the lung apex to the diaphragm. Next, we used a cross-correlation technique to measure the vectors of respiratory movement in specific lung areas. Finally, the average pixel value for a given local area was calculated by tracing the same local area in the lung field. This method of analysis was used for six healthy volunteers and one emphysema patient. The results reported here represent the initial stage in the development of a method that may constitute a new method for diagnosing certain pulmonary diseases, such as chronic obstructive pulmonary disease, fibroid lung, and pneumonia. A clinical evaluation of our method is now in progress.

Improved accuracy of markerless motion tracking on bone suppression images: preliminary study for image-guided radiation therapy (IGRT)*

The bone suppression technique based on advanced image processing can suppress the conspicuity of bones on chest radiographs, creating soft tissue images obtained by the dual-energy subtraction technique. This study was performed to evaluate the usefulness of bone suppression image processing in image-guided radiation therapy. We demonstrated the improved accuracy of markerless motion tracking on bone suppression images. Chest fluoroscopic images of nine patients with lung nodules during respiration were obtained using a flat-panel detector system (120u2009kV, 0.1u2009mAs/pulse, 5u2009fps). Commercial bone suppression image processing software was applied to the fluoroscopic images to create corresponding bone suppression images. Regions of interest were manually located on lung nodules and automatic target tracking was conducted based on the template matching technique. To evaluate the accuracy of target tracking, the maximum tracking error in the resulting images was compared with that of conventional fluoroscopic images. The tracking errors were decreased by half in eight of nine cases. The average maximum tracking errors in bone suppression and conventional fluoroscopic images were 1.3 ± 1.0 and 3.3 ± 3.3u2009mm, respectively. The bone suppression technique was especially effective in the lower lung area where pulmonary vessels, bronchi, and ribs showed complex movements. The bone suppression technique improved tracking accuracy without special equipment and implantation of fiducial markers, and with only additional small dose to the patient. Bone suppression fluoroscopy is a potential measure for respiratory displacement of the target.

Measurements of MTF and SNR( f ) using a subtraction method in MRI

A method was developed for accurate measurement of the modulation transfer function (MTF) and signal-to-noise ratio in the spatial frequency domain (SNR(f)) of magnetic resonance images (MRI). The MTF was calculated from the complex images of a line object which were obtained by the subtraction of two separately acquired data sets of a specially designed phantom with a sliding sheet. Moreover, the SNR(f) was calculated from the MTF and Wiener spectrum, both of which were determined using the same phantom configuration. The MTFs and SNR(f)s in the conventional spin-echo (SE) and turbo SE, in which the effective echo time was set to the first echo, were evaluated by changing the T2 of the phantom and the echo train length. The MTFs in the positive and negative frequencies indicated the effect of the k-space trajectory for each pulse sequence. SNR(f)s gave spatial frequency information that was not obtained with conventional methods. In this method, the influence of image nonuniformity and unwanted artefacts (edge and ghost) could be eliminated. An analysis of the MTF and the SNR in the spatial frequency domain provides additional information for the assessment of image quality in MRI.

New tissue substitutes representing cortical bone and adipose tissue in quantitative radiology.

To employ quantitative radiology more accurately, we examined phantom materials for cortical bone and adipose tissue as calibration standards and as experimental phantoms. New tissue substitutes for cortical bone and adipose tissue composed of liquid phantom were verified by computing their attenuation coefficients and observing their chemical properties. We showed that a potassium pyrophosphate (K4P2O7) solution for cortical bone was comparable to a dipotassium hydrogen phosphate (K2HPO4) solution. Also, the use of methyl alcohol for adipose tissue was more suitable than ethyl alcohol as a phantom material because of its physical and chemical properties.

Psychophysical evaluation of calibration curve for diagnostic LCD monitor

PurposeIn 1998, Digital Imaging Communications in Medicine (DICOM) proposed a calibration tool, the grayscale standard display function (GSDF), to obtain output consistency of radiographs. To our knowledge, there have been no previous reports of investigating the relation between perceptual linearity and detectability on a calibration curve.Materials and methodsTo determine a suitable calibration curve for diagnostic liquid crystal display (LCD) monitors, the GSDF and Commission Internationale de lEclairage (CIE) curves were compared using psychophysical gradient δ and receiver operating characteristic (ROC) analysis for clinical images.ResultsWe succeeded in expressing visually recognized contrast directly using δ instead of the just noticeable difference (JND) index of the DICOM standard. As a result, we found that the visually recognized contrast at low luminance areas on the LCD monitor calibrated by the CIE curve is higher than that calibrated by the GSDF curve. On the ROC analysis, there was no significant difference in tumor detectability between GSDF and CIE curves for clinical thoracic images. However, the area parameter Az of the CIE curve is superior to that of the GSDF curve. The detectability of tumor shadows in the thoracic region on clinical images using the CIE curve was superior to that using the GSDF curve owing to the high absolute value of δ in the low luminance range.ConclusionWe conclude that the CIE curve is the most suitable tool for calibrating diagnostic LCD monitors, rather than the GSDF curve.

Automated analysis for the respiratory kinetics with the screening dynamic chest radiography using a flat-panel detector system

Abstract We have developed a new method for analyzing respiratory kinetics, such as the movement of the diaphragm, the movement of the chest wall, and the respiratory change in X-ray translucency in local lung fields on dynamic chest radiographs. Our approach could provide some respiratory kinetic information as well as severity of disease on image findings. In addition, the results of the movement analysis of the diaphragm well correlated with respiratory functional tests. It was concluded that dynamic chest radiography and our analysis method may be an effective aid for the evaluation of chronic obstructive pulmonary disease, pulmonary fibrosis, pneumonia, and other pulmonary diseases.

Relationship between the biodistributions of radioactive metal nuclides in tumor tissue and the physicochemical properties of these metal ions

This study was undertaken to elucidate the relationship between the biodistribution of radioactive metal nuclides in tumor tissue and its physicochemical properties.Potassium analogs (86Rb,134Cs,201Tl) were taken up into viable tumor tissue, although22Na concentrated in necrotic tumor tissue.67Ga and111In were more predominant in inflammatory tissue than in the viable and necrotic tumor tissue.169Yb and167Tm accumulated in viable tumor tissue and tissue containing viable and necrotic tumor tissue.67Ga,111In,169Yb and167Tm were bound to the acid mucopolysaccharide with a mol. wt. of about 10,000 daltons in the tumor tissue.46Sc,51Cr,95Zr,181Hf,95Nb,182Ta, and103Ru were highly concentrated in inflammatory tissue and were bound to the acid mucopolysaccharides with a mol. wt. exceeding 40,000 daltons.65Zn and103Pd concentrated in viable tumor tissue and were bound to the protein in the tissue.The results suggest that the difference in intra-tumor distribution of these elements is caused by a difference in the binding substances (or status) of these elements in the tissues, and the binding substance is determined by physicochemical properties of the elements. We therefore conclude that the biodistribution of radioactive metal ions in tumor tissue is determined by its own physicochemical properties.