Proton magnetic resonance spectroscopy (1H MRS) is used to evaluate tumors and their remaining function under the assumption that event-related inspection and a method of data collection dependent on time are difficult. Therefore, this study examined the possibility that time depended on in MRS with a visual cortex. We conducted experiments using the following stimulations: REST: eyes are in a closed state, Control: eyes are in an open state, and Continuous: consecutive stimulation and time dependence in the visual cortex. We enabled dependence in time by collecting data with a system that controlled stimulation and experimented on stimulation for a short time using this system. The results showed that no significant difference in metabolites was seen in the REST, Control, and Consecutive stimulations. However, a significant difference was seen in Cr and NAA with time-dependent stimulation. Therefore, we considered functional magnetic resonance spectroscopy (fMRS) useful because time-dependent stimulation showed a meaningful difference with REST.
We devised a method of analyzing a regional fat fraction using a modulus and real multiple gradient-echo (MRM-GRE) 4-7 echo Dixon sequence. The regional fat fraction was calculated with a theoretically fitted signal-intensity curve for multiple GRE images at each echo time (i.e., 4-7 echoes.) on a 1.5 Tesla MRI to correct T2* decay and phase cycling. Then the real image of the first echo was used to differentiate between the areas above and below the 50 percent fat fraction. To eliminate the T1-effect, the flip angle was set at 12 degrees. Fat fractions of the phantom with MRM-GRE were compared with those using conventional double-GRE and other MRI techniques. Fat fractions of liver and spinal bone marrow in healthy volunteers were determined during a breath-hold. The fat fraction of the phantom obtained by the MRM-GRE method tended to agree with the actual fat fraction. On the other hand, in both the phantom and in healthy volunteers, the double-GRE was underestimated owing to T2* decay. The MRM-GRE method enables simple, accurate analysis of the regional fat fraction.
In this study, we evaluated the resolving power of three-dimensional (3D) multiplanar reformation (MPR) images with various angles by using 16 data acquisition system multi detector row computed tomography (16DAS-MDCT) . We reconstructed the MPR images using data with a 0.75 mm slice thickness of the axial image in this examination. To evaluate resolving power, we used an original new phantom (RC phantom) that can be positioned at any slice angle in MPR images. We measured the modulation transfer function (MTF) by using the methods of measuring pre-sampling MTF, and used Fourier transform of image data of the square wave chart. The scan condition and image reconstruction condition that were adopted in this study correspond to the condition that we use for three-dimensional computed tomographic angiography (3D-CTA) examination of the head in our hospital. The MTF of MPR images showed minimum values at slice angles in parallel with the axial slice, and showed maximum values at the sagittal slice and coronal slice angles that are parallel to the Z-axis. With an oblique MPR image, MTF did not change with angle changes in the oblique sagittal slice plane, but in the oblique coronal slice plane, MTF increased as the tilt angle increased from the axial plane to the Z plane. As a result, we could evaluate the resolving power of a head 3D image by measuring the MTF of the axial image and sagittal image or the coronal image.
Intensity-modulated radiation therapy (IMRT) radiation treatment planning (RTP) requires accuracy. Metal artifacts are one of the factors that influence RTP. The metal artifacts from dental structures are problems at the level of the oropharynx, since these artifacts impair visualization of tumors or lymph nodes and change CT (computed tomography) values. We simulated RTP at the level of the oropharynx using CT images with and without artifacts from dental structures. Gantry tilt scanning was performed to avoid artifacts from dental structures and transverse images reconstructed from oblique images by gantry tilt scanning using a technique of multiplanar reconstruction (MPR) . The reconstructed transverse images were used for the RTP. The reconstructed transverse images were useful to obtain accurate target volumes and the RTP of two opposed equally weighted beams by correct CT values. As dose distribution was changed slightly by the metal artifacts, the use of CT images without artifact is recommended in RTP.
An amendment concerning the enforcement of the law on the prevention of radiation hazards due to radioisotopes, etc., and the medical service law enforcement regulations were promulgated on June 1, 2005. This amendment concerned international basic safety standards and the sealing of radiation sources. Sealed radiation sources ≤3.7 MBq, which had been excluded from regulation, were newly included as an object of regulation. Investigation of the SPECT system instituted in hospitals indicated that almost all institutions adhere to the new amendment, and the calibration source, the checking source, etc., corresponding to this amendment were maintained appropriately. Any institutions planning to return sealed radioisotopes should refer to this report.
Although radiographic image quality is considered difficult to evaluate in a straightforward and systematic manner, it may be possible by using an index of transmitted information. As a preliminary study, relations between transmitted information and two image characteristics, namely, image noise and image blurring, were evaluated by simulation. The value of transmitted information was decreased if image noise and image blurring increased. The relationships were corroborated on an experimental basis. This paper suggests the possibility of a simple, straightforward method for synthetically evaluating radiographic images by a single parameter in terms of transmitted information.