[en] For evaluation of the significance of signal intensity and contrast which determine the MR imaging quality, SNR (signal-to-noise ratio) and CNR (contrast-to-noise ratio) were studied as their respective measures on the cross-talk artifact (CTA), partial volume effect (PVE), intensity of the fast spin echo (SE) imaging and contrast in the 3T field area (Con). The machine used was 3.0T Signa HDx (GE). CTA, the SNR-reducing coherence between neighboring slices at multi-slice imaging, was studied with a series of phantoms of 0.75-4 mm diameter acrylic pins in cupric sulfate solution with various imaging modes and slice numbers to calculate CNR and contrast (C) involving SNR factor. PVE, the determinant of the intensity depending on the mixture of different tissues within a voxel (slice thickness), was studied with similar phantoms to above with 1-12 mm thick slices and different slice gaps to obtain CNR and C. The intensity of fast SE image was studied with phantoms in a brain-equivalent 0.125 mM Gd solution of sealed water, 0.25-0.5mM Gd, butter, salad oil and detergent on magnetization transfer, J-coupling and diffusion. Con in the 3T machine was studied with the same phantoms as above on the image contrasts at the central and peripheral imaging areas and the intensity/contrast changes by different coils. Presented data of above examinations revealed the effects of characteristic of each environmental factor, and of which recognition was concluded necessary to exactly read the obtained images. (K.T.)

[en] When the chest CT examination is performed, an observation is made that the posterior side of the lung often appears higher density than the anterior side. Various explanations, from disease, physiological phenomenon, etc. are hypothesized, and examinations are conducted to determine the cause. In a normal lung, the breathed air is gradually filled from the top (relative to gravity) to the bottom, and physiologically, there is a noticeable difference in the CT values. When a deep breath is taken, air fills the whole pulmonary field, and CT values for the top and the bottom of the lung become equal. However, if a patient has inflammation or other disease which restricts the breathed air volume to below normal, a CT value difference is observed. Therefore, the conclusion is reached that the posterior side of the normal pulmonary field having high density is caused by the subject breathing a below normal amount of air, and the pulmonary alveolar wall appearing high density. (author)

[en] The signal intensity obtained from an organism is determined by its tissue composition, the scanning technique, parameters of the apparatus, and other factors. We examined the influence of the partial volume effect on signal intensity and vision in the relation between voxel and photographic subject. We studied the influence that the photographic subject and slice thickness (slice face) exerted on signal intensity, and measured changes in signal intensity according to the positional relation between pixels and the photographic subject. From the results, we clarified the mechanism by which signal is given out from the voxel and examined the relation between the partial volume effect and signal intensity (contrast to noise ratio). We found that signal intensity is determined by the partial volume effect as determined by the ratio between the signal body and a substance set in the surroundings using a macro target and micro target. Moreover, the stimulation given to vision has the relation of a logarithm in contrast. We clarified that the CNR is applied as an approximate value. (author)

[en] We examined the appearance of turbo MRA using zero-filling in k-space, and verified that overlapping scanning created a decline in signal intensity by the partial volume effect. In clinical application, in a case of multiangle visualization after MIP of the CE-3DMRA method, we obtained the effective slice thickness for maintaining the time resolution and spatial resolution. When using an angle within 45 degrees, the effective slice thickness has to be set at less than the diameter of the signal material (objective aortic diameter). And when using a 90-degree angle (lateral direction), the effective slice has to be set at less than 80% of the signal material diameter. (author)

[en] In scanning of the hip joint anterio-posterior radiography, by changing the lower extremities to the extension position and moving the foot axis (base line of the foot) by medial rotation, the angle of anteversion of the femoral neck is corrected. In this study, we assessed the effects on medial rotation of the femoral neck when keeping the planta vertically-positioned by ankle dorsiflexion (intermediate position of the ankle) and making change of the medial rotation angle of the foot axis by scanning the magnetic resonance (MR) images of knee joints and hip joints. The subjects in this study were 12 males (age: 37.9±13.8, weight: 67.3±5.5 kg) and 7 females (age: 27.6±5.1, weight: 50.0±4.5 kg). We measured the medial rotation angles of knee joints and femoral necks on MR images. Also, differences of these angles between males and females were compared. Although the gender differences were not found in medial rotation angle of both joints at all leg positions (P>0.05), the medial rotation angles increased by approximately 1.5 to 2.0 times larger by putting them at the intermediate position, and there were significant differences between the naturally plantar-flexed position and the intermediate position (P<0.05). In conclusion, our results showed that the optimal leg position for correcting the angle of anteversion was 20 degrees medial rotation of the foot axis at the naturally plantar-flexed position, or 10 degrees medial rotation of the foot axis at the intermediate position, regardless of gender. (author)

[en] Enhanced MRA using the three-dimensional Fourier transform (3DFT) sequence for the body or its extremities is commonly adopted. Through advanced technology in the areas of turbo-MRA and ZIP (zero-filled interpolation) high-quality imaging as well as progress in spatial resolution, the anatomy of blood vessels can be depicted with the same high quality as that provided by DSA (digital subtraction angiography). In spite of these technological advances, it is still difficult to obtain clear delineation of the arteriovenous phase and hemodynamics because of the 7-30 second acquisition time. In this study, we examined the possibility of shortening the time to provide effective temporal resolution in the clinical setting. MR-DSA is useful for clinical application because high-quality images with good spatial resolution can be obtained with the 2DFT sequence. (author)

[en] We evaluated low contrast resolution in CT images from various apparatuses by using the second recommendation of the x-ray CT commission. This method is based on visual assessment by an observer using a CT performance evaluation phantom. We evaluated CT images with low contrast resolution using the contrast-to-noise ratio (CNR) in terms of quantity of data, region of interest (ROI) size, and the relation between the second recommendation and CNR, and compared various kinds of machines according to CNR. We found that this method had certain factors that influenced the precision of measurement. However, there was a correlation between CNR and visual evaluation, and we were able to evaluate low contrast resolution in each apparatus. This method was considered a useful step, because low contrast resolution could be easily evaluated. (author)

[en] The FEDIF method in MR imaging has been examined: In particular, the use of low flip angles for enhancing the cervical spinal cord and breath-holding practice for the abdomen. The experimental parameters such as the flip angle and TR in the FEDIF method were determined by measuring the MR intensity for white matter, gray matter and cerebrospinal fluid in human brain, and fat in temporal region. Based on these data, the flip angle clinically suitable for MR imaging of cervical spinal cord and abdomen were determined from the measurement of object contrast and S/N as well as a visual inspection. Due to the smaller motion artifacts present in the FEDIF method with 8deg flip angle than the long SE method, the former is clinically more advantageous than the latter to obtain the enhancement of cerebrospinal fluid. The imaging with breath-holding in abdomen produced distinctly clear images. The contrast between different tissues can be varied by flip angle, and thus, a region of interest is clearly seen. The above result can lead to the conclusion that the FEDIF method is extremely suitable for obtaining distinct images from the abdomen and cervical spinal cord in a shorter time than other MR imaging method. (author)

[en] We have classified liver tumors on dynamic MRI by analyzing their enhanced patterns, and examined how useful it is for the differential diagnosis of hepatic tumors. We have analyzed the staining patterns and sequential changes of 211 nodules of 184 cases on MRI with the contrast media Gadopentetate gimegulmin (hereafter Gd-DTPA) injection. By analyzing the staining patterns of tumors on MRI, we found that diseases each have characteristic staining patterns. In conclusion, it can be said that dynamic MRI with Gd-DTPA injected has made more accurate qualitative diagnosis possible and has improved the existential diagnosis of diseases of minimal change, identifying the expanse of lesions and the degree of infiltration into tissues and organs. (author)

[en] We evaluated the fitting scan technique for contrast enhanced (CE)-3dMRDSA, and found common ground that determines spatial resolution and time resolution (slab thickness and partition number). We also examined the relation between appearance and time resolution (volume of contrast medium and injection speed). To obtain good image contrast, the volume of contrast medium needs to be at least 7 ml and suitable for an injection speed of 3-5 ml/sec. However, when we increased the volume of contrast medium and decreased injection speed, changes in MRDSA images with time became worse. The measure of the bolus with contrast medium was found to determine image contrast. When contrast medium is injected earlier, it circulates earlier within the brain. If the scan time is not short enough, it is not possible to observe changes in MRDSA images. And when spatial resolution is improved, time resolution becomes worse. Therefore, it is important to find the point of compromise between spatial resolution and time resolution. If we look for anterior maximum intensity projection (MIP) images, the contrast-to-noise ratio (CNR) in the spatial resolution didn't change, when the slice thickness is more than 3 mm. Because, the partial volume effect decide the image contrast. However, unless the view is from the front, slice thickness influences spatial resolution. Therefore, when we view MIP images form the lateral direction, slice thickness must be set at less than 2 mm. Results indicated that, in CE-3dMRDSA with the fitting technique, slice thickness should be less than 3 mm, partition number 16-20, slab thickness 48 mm, contrast medium volume 7-10 ml, and injection speed 3-5 ml. (author)