The purpose of this study is to investigate the spectra of a magnetic resonance spectroscopy (MRS) in accordance with the variance of TE and the volumes of metabolites in a localized voxel for the quality assurance using a designed single voxel spectroscopy QA phantom. Because a cone-shape phantom is designed as the volume of metabolite in a localized voxel is changeable, we try to analyze the peaks of each metabolite (NAA, Cr, Cho, Lac, etc.) in accordance with metabolite volume in a localized voxel as well as echo time (TE). All data were obtained using a 3T MRI/MRS machine and analyzed using jMRUI(R). The results of this study show that TE is in inverse proportion to the noise of MRS and the longer TE and the less metabolite volume in the localized voxel, the peak intensities of each metabolite decrease. In case of the lactate, its peak was observed on the all TE only if the greatest metabolite is included in the localized voxel. Then, the intensity of a metabolite is more sensitive to the metabolite volume in the localized voxel than the TE. These obtained in vitro MRS data is provide the guideline that is important for in vivo metabolite quantification. But, in the edge of cone-shape vial air bubbles were observed and spectrum could not obtained. Therefore our cone-shape MRS phantom needs to be modified in order to solve these problems.
Lactic Acid ; Magnetic Resonance Spectroscopy ; Noise ; Spectrum Analysis

An ultrasonic bone densitometer has been developed by measuring speed of sound signal transmitted and received on the skin, not through the horizontal axis but through the vertical one in tissue. The SOS(speed of sound) method measuring the time difference between the ultrasound signals reflected from the both sides of surface of bone could produce more precise result compared with the BUA(broadband ultrasound attenuation) method measuring the frequency difference. Middle finger is selected to be the best measurement position in order to increase the accuracy, after due consideration that the thickness of flesh at the down part of thumb shows too much variation although the ratio of the receiving signal is higher than the other fingers. The measured value by using SOS method shows almost the same result as compared with the conventional DEXA method.
Axis, Cervical Vertebra ; Fingers ; Skin ; Thumb ; Ultrasonics* ; Ultrasonography

In the case of radiotherapy following breast conservation therapy for breast cancer patients, the characteristic of skin dose was investigated in the treatment of intensity modulated radiation therapy (IMRT) for breast cancer patients by comparing and analysing entrance skin dose irradiated during radiotherapy using tangential technique radiotherpy, and IMRT. The calculation dose irradiated to breast skin was compared with TLD measurement dose in treatment planning by performing the two methods of radiotherapy using tangential technique, and IMRT in treatment planning equipment. The skin absorbed dose was measured to pass a nipple by spacing of 1 cm distance from center to edge of body. In the radiotherapy of tangential technique, for the irradiation of 180 cGy to PTV, the calculation dose was ranged from 103.6 cGy to 155.2 cGy, measurement dose was ranged from 107.5 cGy to 156.2 cGy, and skin dose in the center was maximum 1.45 times more irradiated than that in the edge. In the IMRT, for the irradiation of 180 cGy to PTV, the calculation dose was ranged 9.8 cGy at 80.2 cGy, measurement dose was ranged 8.9 cGy at 77.2 cGy, and skin dose in the center was maximum 0.23 times less irradiated than that in the edge. IMRT was more effective for skin radiation risks because radiation dose irradiated to skin in IMRT was much less than that in radiotherapy of tangential field technique.
Breast Neoplasms* ; Breast* ; Humans ; Nipples ; Radiotherapy ; Skin*

A model theory of passive-targeted drug delivery in sphere-shaped solid tumors is introduced on the basis of Fick's law of diffusion, with appropriate boundary and initial conditions. For a uniform initial concentration inside the tumor, the concentration is obtained as a function of time and radial position. The concentration is shown to approach the equilibrium distribution as the time elapses, as is expected by the Gedanken Experiment. The time-evolution rate is found to be determined by the diffusion coefficient of the drug in the tissue, the size of the tumor, the volume of the drug-injected region, and the concentration gradient at the boundary.
Diffusion ; Jurisprudence

Recent advent of 64-multidetctor (MD) CT enables more coverage of Z-axis in the perfusion imaging. The purpose of this study was to evaluate the clinical usefulness of perfusion CT by using 64-MD CT in detecting the lesion in patients with acute stroke. The perfusion CT was performed by using 64-MD CT in 62 consecutive patients who were initially suspected to have subacute ischemic stroke symptoms during the period of recent 9 months. These patients had subacute stroke (n=62). CT scanning was conducted with Jog Mode which provided 16 imaging slices with 5 mm of slice thickness, and 8 cm of coverage in Z-axis. Scan interval was 1 seconds for each imaging slice and total 15 scans were repeated. After CT scanning, perfusion maps (CBV, CBF, MTT and TTP) were created at Extended Brilliance Workstation. The CBV and CBF maps showed that lesions were smaller images. While on the MTT and TTP map lesions were seen to be larger fifty-one were large than they appeared on these images. Two slices of perfusion maps obtained at the level of the basal ganglia were chosen to simulate conventional older perfusion CT with 8 cm of coverage in Z-axis. TTP and MTT maps may be clinically useful for evaluation of the penumbral zone in cases of aubacute cerebral ischemic stroke. The perfusion CT is useful in the assessment of acute stroke as an initial imaging modality.
Basal Ganglia ; Humans ; Perfusion Imaging ; Perfusion* ; Stroke* ; Tomography, X-Ray Computed

Current digital radiography systems are rapidly growing in clinical applications. The purpose of this study was to evaluate the characteristics of a mobile digital radiographic system. The performance of the mobile DR system was evaluated by measuring the modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE). Measurements were made on a LISTEM Mobix-1000 generator and a Teleoptic PRA Alpha-R4000 detector. Imaging characteristics were measured for these two systems using the IEC-61267 defined RQA5 (kVp: 74, additional filtration: 21 mmAl) radiographic condition. The MTF at 10% was measured as 2.4 cycles/mm and the DQE(0) values for radiation exposure 0.19, 0.5, and 1.3 mR were measured as 54%, 55%, and 76%, respectively. The NPS curves gradually decreased at high spatial frequencies. This high DQE at low frequencies, may be useful for low frequency information. The results suggested that mobile DR system could be integrated with emergency ambulance system in teleradiologic imaging applications.
Ambulances ; Emergencies ; Filtration ; Noise ; Radiographic Image Enhancement

Photodynamic therapy (PDT) is one of the expectable current cure operation methods. Tumor tissue is treated by abundant oxygen in a body and generated singlet or free radical from exterior laser diode and photosensitizer. Current problem of PDT is the low penetration power of the light beam in a deep seated large tumor and solid tumor thus results in low treatment outcome. In the study, we tried to develop interstitial photodynamics therapy treatment to solve this problem. As the accurate determination of light dosimetry in biological tissue is one of the most important factors affecting the effectiveness of PDT, parameters used in this study are the optical property of biological tissue. Since biological tissues have large scattering coefficient to visible light the penetration depth of a biological tissue in visible light region is only 15~20 mm. We showed that it is possible to measure fluence rate and penetration depth within the biological tissues by Monte Carlo simulation very well. Based on the MC simulation study, the effectiveness of interstitial photodynamic therapy on tumor control in solid tumor was proved through in vivo animal experiment.
Animal Experimentation ; Light ; Oxygen ; Photochemotherapy* ; Treatment Outcome

The energy spectra and dose calculations were performed for secondary neutrons from a 24 MV LINAC using MCNPX code (V2, 4, 0). The energy spectra for neutrons and photons emitted from the LINAC head, and absorbed dose to water were calculated in water phantom. The absorbed doses calculated with Monte Carlo were 0.66~0.35 mGy/photon Gy at the surface to d=5 cm, and calculated with interaction data was 0.52 mGy/photon Gy at the depth of electron equilibrium in water. We have shown that this work can be applied to dose estimation of neutrons from high energy LINAC through the comparison of our results with other results.
Head ; Neutrons* ; Photons ; Water

In this study, we investigated the effect of time gating threshold on the delivered dose at a organ with internal motion by respiration. Generally, the internal organs have minimum motion at exhalation during normal breathing. Therefore to compare the dose distribution time gating threshold, in this paper, was determined as the moving region of target during 1 sec at the initial position of exhalation. The irradiated fields were then delivered under three conditions; 1) non-moving target 2) existence of the moving target in the region of threshold (1sec), 3) existence of the moving target region out of threshold (1.4 sec, 2 sec). And each of conditions was described by the moving phantom system. It was compared with the dose distributions of three conditions using film dosimetry. Although the treatment time increased when the dose distributions was obtained by the internal motion to consider the TGT, it could be obtained more exact dose distribution than in the treatment field that didn't consider the internal motion. And it could be reduced the unnecessary dose at the penumbra region. When we set up 1.4 sec of threshold, to reduce the treatment time, it could not be obtained less effective dose distribution than 1 sec of threshold. Namely, although the treatment time reduce, the much dose was distributed out of the treatment region. Actually when it is treated the moving organ, it would rather measure internal motion and external motion of the moving organ than mathematical method. If it could be analyzed the correlation of the internal and external motion, the treatment scores would be improved.
Exhalation ; Film Dosimetry ; Respiration*

In this study, the physical compensator made with the high density material, Cerrobend, and the electronic compensator realized by the movement of a dynamic multileaf collimator were analyzed in order to verify the properness of a design function in the commercial RTP (radiation treatment planning) system, Eclipse. The CT images of a phantom composed of the regions of five different thickness were acquired and the proper compensator which can make homogeneous dose distribution at the reference depth was designed in the RTP. The frame for the casting of Cerrobend compensator was made with a computerized automatic styrofoam cutting device and the Millennium MLC-120 was used for the electronic compensator. All the dose values and isodose distributions were measured with a radiographic EDR2 film. The deviation of a dose distribution was +/-0.99 cGy and +/-1.82 cGy in each case of a Cerrobend compensator and a electronic compensator compared with a +/-13.93 cGy deviation in an open beam condition. Which showed the proper function of the designed compensators in the view point of a homogeneous dose distribution. When the absolute dose value was analyzed, the Cerrobend compensator showed a +3.83% error and the electronic compensator showed a -4.37% error in comparison with a dose value which was calculated in the RTP. These errors can be admtted as an reasonable results that approve the accuracy of the compensator design in the RTP considering the error in the process of the manufacturing of the Cerrobend compensator and the limitation of a film in the absolute dosimetry.