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Boron Neutron Capture Therapy (BNCT) is an approach of cancer treatment using high reactivity of boron with neutron. In BNCT, image-based monitoring of the reactivity in target region is important for the safety of patient and the evaluation of efficacy in treatment. In this study, we designed and evaluated a system of GAGG based prompt gamma ray imaging (PGI) camera with parallel hole collimator using Monte Carlo (MC) simulation. GATE (v7.0) packages have been used in the MC simulation. Various parameters for parallel hole collimator design were considered. In the MC simulation, a spherical water phantom was placed at the center of field of view (FOV) of gamma camera and a spherical boron phantom was positioned at the center of the water phantom. The diameter of water phantom was changed to evaluate the effect of scatter and annihilation photons in PGI. As the neutron energy increased, the range of the neutron in the water increased. As the amount of scattering material increased, image quality was decreased due to the increased amount of scatter and annihilation gamma ray of 511 keV components. The septal penetration ratio of 3.5 %, which is generally considered suitable to nuclear medicine imaging, was not acceptable in PGI for differentiating target. For PGI in BNCT, higher value of septal penetration fraction should be considered in collimator design. Optimized design of collimator and scatter correction would be necessary for the better quality of PGI of BNCT.

We designed a novel single-photon emission computed tomography (SPECT) system with a variable pinhole (VP) collimator for obtaining high-sensitivity and high-spatial resolution imaging of a region of interest (ROI). Extending the capabilities of conventional SPECT systems, this novel SPECT system with a VP collimator can adjust its driving parameters, such as a collimator diameter, acceptance angle, and distances between the ROI, collimator, and detector at different rotation angles. Previously, we simulated a VP collimator and demonstrated the superiority of the VP SPECT system in terms of its sensitivity and spatial resolution. Based on these previous results, we developed a prototype SPECT system for performance evaluation of a VP collimator. The collimator was made from 99.9% pure tungsten layers, with 16 holes of different diameters. The area of the CsI(Tl) scintillator was 45.7 × 45.7 mm2 (51 × 51 pixels), with pixel dimensions of 0.7 × 0.7 × 5 mm3. The multi-pixel photon counter was tiled into a 2 × 2 configuration with dimensions of 52 × 52 mm2. The collimator, detector, and gantry of this SPECT system were independently controlled. We acquired initial reconstructed images from a point source (Co-57) and an ultra-micro phantom (Tc-99m). The point source and the phantom were clearly resolved, demonstrating satisfactory detector response, signal processing, and imaging processing capabilities. The 1.35mm phantom was also clearly resolved in the ultra-micro phantom.

The acute organ motion estimation in multimodal imaging improves quality of diagnosis and therapy of tumor. It is particularly important in the organ related involuntary movement such as lung and liver. The aim of this study was to compare the region specific motion in rodent using radioactive molecular sieve PET image and MRI image. The molecular sieve was contained 0.37 MBq F-18 and coated with hydrogel. For comparison of internal and external motion, molecular sieve was placed inside lung and liver and attached on the surface of each organ region in SD-rat. PET study was performed using a small animal PET scanner (Inveon) after IV injection of FDG 37 MBq/0.2 mL. List-mode data was synchronized with respiratory gating trigger signal from external monitoring system (Biovet). MRI study was performed using 3-T clinical MRI system (Magnetom Tim Trio) with human wrist coil. Coronal MRI images were acquired using T2-weighted turbo spin echo (TSE) sequence with respiratory triggering. The parameter is as follow settings: TR = 1000 ms, TE = 36 ms, FA = 20. We analyzed moving pattern and variation of movement in lung and liver region following respiratory cycle in both of PET and MRI images. Moving patterns in PET image were different in accordance with where molecular sieve was placed. The variation of lung and liver internal motion was 0.93 and 0.52 in PET image, respectively. Estimated organ motion in MRI image revealed moving pattern based on respiratory cycle. The maximum variation of lung and liver region was 1.75 and 1.36 in MRI image, respectively. We recognized organ motion was different depending on the region and the monitoring signal was overestimated compared to real motion in both of region in PET. This study demonstrated that region-specific motion estimation would realize through aid of MRI images without ext

Positron emission tomography (PET) can provide functional information in the human body. However, thoracic and abdominal PET images suffer from attenuation-related errors due to respiratory motion as well as blurs due to respiratory motion itself. In our previous study, to obtain respiratory-gated PET images, we proposed a novel method for respiratory phase matched attenuation correction (AC) and motion compensation (MC). That method utilizes a virtual 4D CT image generated via non-rigid registrations among a 3D CT image and a couple of respiratory-phase 3D MR images. In this paper, for respiratory phase matched attenuation correction and motion compensation, we propose to use a couple of respiratory-phase low-dose CT images rather than MR images. Experimental result for a clinical dataset shows that the proposed method can also provide much clearer organ boundaries as well as more accurate lesion information than the conventional method in a 3D PET image.

We are developing a block detector to be used in in-beam PET for hardron therapy, which consists of a discrete scintillator array and four round-type PMTs. To improve positioning performance we applied Gaussian mixture model (GMM)-based positioning algorithm that was previously developed by our group. In order to maximize separability of light distributions among adjacent scintillator pixels and thereby optimize the positioning performance, we used partially segmented block scintillator proposed by Chung et al. In partially segmented block scintillator, length of light reflectors between two adjacent discrete scintillators varies depending on the locations of the scintillators in the array. We simulated 3D crystal array with variable length of reflectors so that we extract best combinations of reflector dimensions in the array. With these optimal values, we showed the performance of our positioning algorithms. The DETECT2000 simulation package was used to model a proposed detector. The designed the detector was made up of 13 × 13 array of 4 × 4 × 20 mm3 LSO blocks. Four sides of each crystal was attached with different length of reflectors. We used 2 × 2 one inch PMTs(22 mm effective area) so that four PMTs can share the lights. In GMM-based positioning algorithm, the response of N detector channels is represented by a feature vector. Then it trains the feature vectors to obtain the optimal parameters of M Gaussian mixtures. In evaluation step, we decoded the spatial locations of incidence photons by evaluating the measured feature vector with respect to the trained mixture parameters. The results showed that the average bias were 0 mm. In addition, most of positions for the 13×13 scintillator block were clearly identified.

The objective of this study is to develop a deformable 3D image registration algorithm for breast PET-CT and MR images based on perturbation-weighted feature information. As a preprocessing, breast regions were separated by regional masks from the abdomen CT and MR. To remove the jig frame that was used for fixing patient posture during the PET-CT scan, we performed the breast segmentation by region growing. Then a point set was extracted from each modality for surface matching. The point set of CT was used as a target model, and the point set of contrast-enhanced MR was used as a reference model. The surface of a breast does not have many features, but we thought that the nipples and scars can be used as salient features to improve registration performance. The proposed algorithm imposes more weights on those features according to the degree of surface perturbation. Furthermore, we used the hierarchical block-wise operation to minimize the error of the local part. After matching the point sets of the global region, we divide the region to N by N blocks and match the point sets of local blocks. We repeat this step by increasing N until the similarity hit the maximum value. Finally, the PET image is transformed with the optimized transformation parameters and is overlaid onto the MR image. The preliminary results show that the surface of breasts from MR and CT matched well, thereby alignment of the clinically meaningful lesions of the MR and PET slices were improved. For future works, we will investigate more features other than surface and improve the performance of algorithm by adjustment of the weights.

The aim of this study was to automatically assessment of the 64Cu-PTSM, 99mTc-MIBI and 201Tl myocardial perfusion image using Multi Gaussian Mixture Model (MGMM). Myocardial infarction (MI) model was prepared through permanently ligated left circumflex artery of rats. PET/SPECT images were acquired using small animal PET/SPECT scanner (InveonTM, Siemens) with physiological monitoring system (BioVet, m2m Imag. Corp.). PET images were obtained at 10 min post injection of 37 MBq/0.2 mL of 64Cu-PTSM via tail vein as list-mode data. SPECT images were acquired at 60 min post IV injection of 110 MBq of Tc99m-MIBI and Tl-201/0.1 mL with 126-154 keV (Tc), 63-77 keV (Tl) energy window and 1.0 mm pinhole collimator. The acquired data was reconstructed by OSEM2D algorithm with 4 iterations. To automatically make the myocardial contour and generate polar map, we used Cedars-Sinai method. Myocardial infarct region of polar map were evaluated by using MGMM method for adaptive threshold calculation and predefined threshold method for absolute threshold calculation. Rat myocardium was stained by hematoxylin and eosin (H&E) for reference value of infarct size after the imaging. The infarct size of PET/SPECT image was defined by infarction area percentage of the total left myocardium. Comparative analysis was performed between MI size of histology and polar map. The size difference in 64Cu-PTSM PET polar map was 6.96 3.53% from the absolute value 40% and 4.40 0.58% from MGMM4. The difference in 99mTc-MIBI SPECT polar map was 8.87 1.16% from the absolute value 40%, and 3.47 1.99% from MGMM4. The difference in 201Tl SPECT polar map was 11.73 1.45% from the absolute value 40%, and 2.97 1.46% from MGMM4. MGMM method showed the possibility of quantitative evaluation for my

The objective of this study is to develop a 3D breast image registration algorithm for PET-CT and MR system. Proposed algorithm consists of three stages: breast segmentation, surface matching, and image transformation. Contrast-enhanced MR image volume was used as a reference and CT volume was transformed with varying parameters to calculate similarity between two image modalities. At first, the breast regions were cropped separately by the pre-determined regional masks. For the CT image case, region growing based breast segmentation was explored to eliminate the breast dedicated jig which has been developed to hold the shape of breast during PET-CT scan. After the segmentation, each of the points set of breast surface has been extracted. The extracted point sets were used as a feature vector for the surface matching. For the surface matching, we developed modified version of elastic-convolved iterative closest point (ECICP) algorithm to obtain the optimal transformation parameters. Then PET image was transformed with those parameters and overlaid it onto MR image. The results of this study show that the difference between MR and CT image has been considerably reduced and the suspicious lesions on MR and PET images were matched as well.

Gamma camera imaging is one of prevalent diagnostic imaging tool for nuclear medicine. Although gamma camera imaging widely used for diagnostic imaging, quantification of gamma camera imaging is difficult due to scattered radiation. Compton scattering is always a problematic phenomenon in gamma camera imaging. In previous study, Siemens symbia scintillation camera was modeled for assessment of septal penetration photons and validation of Monte Carlo simulation code for the Siemens scintillation camera. In this study, optimal energy window for triple energy window (TEW) scatter correction method was assessed in gamma camera for 99mTc, 131I radioisotopes using GATE simulation.

Radioimmunotherapy (RIT) is a promising approach for targeted therapy to treat intractable cancer because radionuclides are delivered more selective to tumor using monoclonal antibody, RIT can be used clinical practice with administration of murine anti-CD20. In this study, the absorbed dose of total body and red marrow of patient enrolled in RIT study was calculated.

Recently, we have reported the approach of transmitting photo-sensor charge signal to preamplifier using long cable for development of hybrid PET-MRI. However, pulse distortions degrading the performance of PET detector might occur in this approach. The purpose of this study is to develop a pulse restoration circuit (PRC) compensating the performance degradations caused by using the long cable from Gaige-mode avalanche photodiode (GAPD) to PET electronics. The effect of the cable length on the PET detector performance was examined using different lengths of flexible flat cable (FFC) ranging from 0 to 21 m. Rise time, fall time and amplitude of the GAPD output were measured as a function of the cable length. Photopeak position, energy resolution and time resolution were also measured using a 100 MS/s data acquisition unit. The PRC based on the filtering and shaping networks was consisted of amplitude, rise time-fall time restoration parts. The amplitude restoration part was designed using op-amp and resistors and the rise time-fall time restoration parts were designed using RC shaping filter. There were changes in the PET detector performance as a function of the FFC lengths ranging from 0 to 21m. The amplitude and the photopeak position decreased from 169 mV to 100 mV and from 400 ch to 300 ch, respectively. The rise time, fall time and the time resolution increased from 35 ns to 61 ns, from 210 ns to 450 ns and from 1.1 ns to 2.2 ns, respectively. No considerable changes were observed in the energy resolution of 16%. These performance changes was improved by employing the PRC. The measured pulse shapes passing through the long cable with PRC, were identical to the GAPD output with the cable length of 0 m, and the photopeak position was restored. The time resolution was also improved from 2.2 ns to 1.3 ns. This study demonstrated that the PRC could improve the performance degradations caused by using long cable.

The purpose of this study was to assess the optimal gates number of each region using estimated internal motion. Internal motion has been demonstrated in lung and liver region of small animal by coated molecular sieve. We coated molecular sieve with Pluronic F-127 hydrogel for keeping the activity in the body. All PET studies were performed with a dedicated small animal PET scanner. Respiratory gating was operated the external trigger device synchronized with the list mode acquisition. The trigger signals were simultaneously reflected motion of heart and breathing. The list mode data were converted to sinogram gated 2∼16 bin. In PET image analysis for determining optimal gate number, count and SNR were measured from ROI in the target region. Horizontal and vertical FWHM were measured from line profile in each images. The motion compensation PET image for optimal gate number was confirmed by internal motion. The measured value of lung region showed high count (8.67), high SNR (3.25), and high FWHM (1.83) in 8 bin. In liver region, high count (2.09), high SNR (3.99), and high FWHM (2.23) were revealed in 9 bin. The artificial tumor evaluation study using molecular sieve is a method to assess accurately internal organ motion in the rodent. The gate number for motion correction should be set differently in accordance with the organ because motion level varies as each organ. The estimated internal motion will be a useful method for motion compensation modeling.

We investigated optimized collimator designs for I-131 high energy gamma ray imaging on small animal gamma camera. The simulated structures of the pinhole collimator were evaluated by sensitivity, true, scatter and penetration count rates, and spatial resolution. The parameters, which were pinhole diameter, acceptance angle, and aperture thickness, were determined to improve image resolution with geometric conditions. In this study we showed optimized pinhole design for high energy I-131 imaging to meet the tradeoff between sensitivity and resolution

The aim of this study was to improve quantitative assessment of rat myocardial infarct size using attenuation corrected PET polar map with gated CT image and MRI polarmap. The PET/CT images obtained with a small animal PET/CT scanner. Gating was realized with the help of an external trigger device. Contrast enhanced FLASH sequence MRI image was acquired with a 3-T clinical MRI using ECG triggering. The SUV PET image pixel size was percent variation was calculated anterior wall (ANT), septal wall (SEP), inferior wall (INF) and lateral wall (LAT) in polar map. Homogeneity was calculated no corrected PET (NC), attenuation corrected PET with CT image (AC-CT) and AC gated PET with gated CT image (gAC-gCT). TTC staining measures tissue viability used to evaluate real infarct size. The reference infarct size was defined by infarction area percentage of the total left myocardium. The infarct size for optimal size was repeated varying threshold values. The NC and AC-CT image percent variation of ANT, SEP, INF and LAT was −0.42%, 1.61%, −0.41% and −0.86% respectively. The gAC-gCT image percent variation of ANT, SEP, INF and LAT was 3.74% 1.21% 3.28% and 4.29% respectively. The gated CT AC gated PET polar map homogeneity was improved myocardial activity in anterior, inferior and lateral region. MRI based polar map with FLASH sequence at threshold lower 60% provide good result of infarct size measurement. Integrated myocardial analysis technology of high sensitive PET and high resolution MRI images may potentially facilitate the improvement of volume and attenuation correction information in cardiology.

The objective of this research is to develop 2D/3D registration algorithm for PET/CT and CT or MR images acquired by different systems at different times. We matched two anatomical images first (one from PET/CT and the other from standalone CT or MR) that contains affluent anatomical information. Then we geometrically transformed PET image according to the result of transformation parameters calculated by previous step. We developed two stages of registration algorithm. The first stage is global registration. It is consists of 4 independent steps. After selection of reference and target images different data types and ROI of images have been normalized in the preprocessing step. As a next step, target image is geometrically transformed then the similarity between two images has been measured quantitatively. The optimization step updates transformation parameters to find the best matched parameter set efficiently. In second stage that is called fine adjustment, we introduce feature based registration algorithm. The features of each image slices are extracted by independent component analysis(ICA) and the extracted feature plane is used to measure the similarity. B-spline based freeform deformation is done to form a registered image as a final step. The result of proposed algorithm shows good agreement of images that between PET/CT to CT and PET/CT to MR. We will expand the application of the algorithm to different imaging modalities.

Transparent conducting AZO thin films were prepared by RF magnetron sputtering system with glass substrate (corning 1737) and annealed during 2 hr at 400degC in vacuum ambient and 600degC in oxygen ambient, respectively. The smooth AZO films were etched in diluted HCL (0.5%) to check the surface properties with the ambient post-annealing process. Using the methods of SEM and Spectro-radiometer, we analyzed the optical properties of the textured AZO thin films. We confirmed that the vacuum ambient post-annealing process is effective method for increasing the efficiency of long wavelength LED. The oxygen ambient post-annealing process is suitable method for increasing the efficiency of short wavelength LED. We presumed that the ambient post-annealing process can control textured surface of AZO thin films for increasing the efficiency of LED.

Multilayered Co/Pd nanowire array were obtained from atomic image projection electron beam lithography (AIPEL) and combined novel etching technique using amorphous Si layer. The role of dipolar interaction in magnetic anisotropy of the nanowire array was studied. The structural information were obtained by HR-TEM, XRD, SEM and AFM. The magnetic properties were measured by SQUID and vibrating sample magnetometry.

Animal model make the precise detection of ventilatory phase difficult, and the relatively high ventilation rates seen in small animals. The aim of this study was to develop cardiac and respiratory motion correction system with list-mode acquisition for the small animal microPET scanner. We utilized a commercially available slim force sensor to detect respiratory motion and trigger generating device built in-house during microPET scanning. The CT images obtained with the clinical CT scanner can be used to improve the anatomical localization of uptake in the microPET images. A method for co-registering CT and microPET images was developed to improve the anatomical localization of PET uptake. This technique improves the quantitative specific activity of the tracer, which is distorted because of the respiratory motion.

Scatter correction (SC) has been shown to be essential for the quantification of brain perfusion in SPECT. However, in the case using the tracer showing a high activity accumulation in a small region with only a small activity in other areas of brain, the contribution of SC has yet to be studied. In this work, the impact of SC on the quantitative kinetic parameters derived from SPECT studies using a dopamine D2 receptor ligand was investigated. SPECT data were acquired dynamically with serial arterial blood sampling following intravenous injection of I-123 iodobezofuran (IBF). SC was performed with the previously validated transmission dependent convolution subtraction (TDCS) technique. Images were reconstructed by OSEM including the attenuation correction (AC), and FBP with post AC by Chang's method. Time activity curves (TACs) were generated from the striatum (STR) and occipital lobe (OCC) regions, with and without SC. Quantitative values of binding potential (BP) were then compared for four kinetic models, including the 3 compartment model (3COM), linear graphic plot (GRP), reference tissue method (RTM), and multi-regression method (MLR). SC changed both TACs of STR and OCC, and introduced significant changes in kinetic parameters, which induced the significantly increased BP in 4 kinetic models, compared to those without SC. The change in BP by SC was greater with 3COM model, than the other models. SC caused significant change in the shape of TACs in both STR and OCC, resulting in increased BP with all four kinetic methods. Likewise for the brain perfusion study, SC is required for the dopamine D2 receptor ligand studies in SPECT.

Knowledg of the precision in the physiological parameters estimated by positron emission tomography (PET) is helpful for optimizing PET study and accurate diagnosis. Nonparametric bootstrap method proposed by Buvat is re- sampling techniques that can be used to accurately estimate the statistical properties of PET images in one scan and determine statistics of pixel values. The standard deviation (SD) of time activity curves (TAC) generated by region of interests (ROI) also are estimated by using the bootstrap method and the SD would propagate to estimated parameters such as blood flow. In order to evaluate the present method, a PET study for myocardial blood flow (MBF) measurement with H2 15 O_PET was performed. The statistical properties of MBF were estimated and the effects of scan-duration time and ROI size on the SD of MBF were developed. statistical properties of PET images in a single scan. The bootstrap approach is a computer-based statistical method for determining the accuracy of a statistic from experimental data (6). Buvat estimated statistical properties for PET and single photon emission computed tomography (SPECT) successfully using non-parametric bootstrap method (7). Noise estimates in reconstructed images could be introduced into quantitative data analysis to account for the uncertainty of pixel and region of interest (ROI) values. This study investigated the precision in the MBF with H2 15 O_PET using statistical properties expressed by bootstrapped images of a single acquisition. Using the concept of the non-parametric bootstrap method, we developed a method to know the standard deviation (SD) and coefficient of variation (COV) of estimated parameters of MBF, PTF, and arterial blood volume with H2 15 O_PET. A PET study with one pig was performed in order to evaluate the present technique. Strategies for scan duration and ROI selection were also investigated with the effect of SD and COV indicated by present method.

The telemedicine systems for the decision of patient transfer, and the direction of patient treatment through remote consultation are necessarily required for better patient care in emergency situation. In this paper, the prototype emergency telemedicine system has been designed and implemented. The unified integration of multimedia components, including full-quality video, vital sign signals, radiological images and video conferencing in a single computer, provides an efficient means to investigate the accurate status of emergency patient at the remote location. The software implementation of needed functionality without any externally attached hardware CODEC units enables the compact design with low cost, and ease of operation at the emergency room. Experimental tests at the local networks analyze the technical aspects of implemented systems, and optimize the parameters subjectively to run telemedicine systems with affordable error. Inter-hospital experiments demonstrate the possibility to be effectively used at emergency situation.

Head motion during PET scanning produces significant artifact or spatial resolution loss on the reconstructed image. Event-based motion correction (EBMC) technique has been developed to correct head movement during the scan incorporated with list mode acquisition of PET and an optical tracking system. In EBMC technique, each line-of-response (LOR) in the list-mode data was reoriented due to the motion data by the optical tracking system. Although EBMC technique has potential to correct head movement during PET acquisition, large size of list mode data set hampers the capability of on-line processing for the correction. In order to improve in the speed of computing time for EBMC, we implemented EBMC on a Beowulf PC cluster consisting of 7 PCs (24 GHz Xeon for a master node and 1.4 GHz PentiumIII for slave nodes) connecting each other through Gbit Ethernet. MPI (Message Passing Interface) protocol was utilized for parallelizing the task of EBMC. The performance of the PC cluster was evaluated using list-mode data and head motion data acquired by ECAT EXACT HR+ (CTI/Siemens) PET scanner and POLARIS (Northern Digital) optical tracking system. The six list-mode data sets (file sizes are from 161 to 253 Mbytes) were corrected for motion by EBMC technique on a single PC and the PC cluster. The PC cluster was 5.2 times faster than the single PC to perform the motion correction. The PC cluster remarkably improves the performance of EBMC with low cost.

In order to convert scatter uncorrected into corrected SPECT image, an image-based scatter correction (IBSC) method has been developed. The aim of this study was validation of its role as image converter from scatter uncorrected into corrected images equivalent to image corrected by conventional TEW method. IBSC method is executed in the postreconstruction process and only requires an attenuation corrected main photopeak image with broad /spl mu/ value, I/sub AC//sup /spl mu/b/. The scatter component image is estimated by convolving I/sub AC//sup /spl mu/b/ with a scatter function followed by multiplying with an image-based scatter fraction (SF) function. The IBSC method was evaluated with Monte Carlo simulations and /sup 99m/Tc-ECD SPECT human brain perfusion studies obtained from five volunteers. The noise property of the scatter corrected image using IBSC method, I/sub IBSC/, was compared with that by TEW method, I/sub TEW/, with simulated brain phantom images. Image contrast between gray with white matter in the human study was also compared between IBSC and TEW method. The global signal-to-noise (S/N) ratio of I/sub IBSC/ was decreased to 14% compared to that of I/sub AC//sup /spl mu/b/, whereas that of I/sub TEW/ was decreased to 21%. In human brain imaging, significant difference in image contrast between IBSC and TEW method was not observed (p

Measurements of the oxygen consumption in brain have been studied by PET. Autoradiographic method(ARG) was suggested (Mintum et al.) to yield CMRO2. This method required separately obtained information about CBF, CBV, thus time of 30-60 min. is required for three separate scans. We developed a rapid dual table method, in which water and oxygen are continuously administrated with the 90-180 sec of water and 180 sec of oxygen scan. In order to derive the quantitative CMRO2 in PET scan, it is necessary to obtain the arterial blood time activity curve. In this study, a method to estimate the input functions corresponds to [/sup 15/O] water injection and [/sup 15/O] oxygen inhalation, in a continuously administration study, was developed. A method developed was model-based, employing a fitting method. In order to estimate the reliability of developed method, input functions of [/sup 15/O] water injection and [/sup 15/O]oxygen inhalation obtained separately in a clinical study was combined with time lag of 90 seconds and 180 seconds. The reproducibility was examined by comparing the blood input functions obtained from present method and from original input functions obtained in clinical study. After fitting the combined input function with model function, each input function of [/sup 15/O] water injection and [/sup 15/O] oxygen inhalation was derived. The whole shapes were in agreement with each other. This method could be used for estimation of each input function in continuously water and oxygen administrated study.

A new input function monitoring system has been developed using a GSO detector for both PET and SPECT quantitative studies. The paired assembly of crystals provided an absolute sensitivity of approximately 7% for PET tracers and 70% for /sup 99m/Tc and /sup 201/Tl (SPECT tracers). This system was applied to clinical use and animal study such as monkey and rat. This study demonstrates that the present system can he of use in both clinical and small animal studies using SPECT and PET tracers.

Measurements of the oxygen consumption in brain have been studied by PET. Autoradiographic method(ARG) was suggested (Mintum et al.) to yield CMRO/sub 2/. This method required separately obtained information about CBF, CBV, thus time of 30-60 min. is required for three separate scans. To decrease the scan time, a new protocol was suggested as a rapid dual table method(ARG-D), in which [/sup 15/O]water injection scan and [/sup 15/O]O/sub 2/ inhalation scan are continuously carried out. Another method of weighted integration(WI) method with single 3 min. /sup 15/O/sub 2/ inhalation scan was suggested (Ohta et W.). We modified this method by taking into account the water re-circulation(WI-WR). In this study, the statistical noise properties and effects of error propagated from dispersion, delay and volume of distribution on CMRO/sub 2/ image, derived by these methods were evaluated. Tissue time activity curves was generated from typical blood time activity curves. A 80% of noise at a peak in [/sup 15/O]water tissue time activity curve was added to study the noise propagation and accuracy in CMRO/sub 2/ image. Also dispersion, delay, and volume of distribution was varied and evaluated the error propagation. Methods of ARG, WI-WR and ARG-D, reproduce the given CMRO/sub 2/ within 2% accuracy, while method WI gives CMRO/sub 2/ 5-15 The effect of noise in unit of %SD was 12 % for ARG, 25 % for WI and WI-WR, and 17 % for ARG-D method. On the basis of simulation study suggests that the ARG-D method developed could be used to estimate the CMRO/sub 2/ values in clinic.

The transmission-dependent convolution subtraction (TDCS) technique is a promising technique in quantitative SPECT to subtract the scatter components from emission images. Usually a 20% photo-peak energy window is used in SPECT acquisitions. So far no investigation has been done to investigate the effect of energy windows to subtract the scatter components from emission images with the TDCS technique. To evaluate the energy dependency of the TDCS technique, SPECT acquisitions were performed for the photo-peak energy windows of 5%, 10%, 15%, 20%, 25%, 30% and 35% by acquiring the data of nonuniform and uniform phantom with /sup 99m/Tc radionuclide. The parameters of the scatter fraction to be used in the TDCS technique were estimated with the point sources placed in the water phantom. The estimated parameters were used in the TDCS technique to subtract scatter components from the data of corresponding energy windows of non-uniform and uniform phantom. Poisson noises were added to each projection's data of uniform phantom before scatter corrections. All data were reconstructed with the OSEM algorithm. The energy window dependence of the TDCS technique was verified by comparing the coefficients of variance (COV) of the data of the uniform phantom of each energy window. The non-uniform phantom results showed that the estimated parameters effectively estimated the scatter component from the projection images for each energy window. The COV for 5%, 10%, 15%, 20%, 25%, 30% and 35% energy window were 2.10%, 1.76%, 1.44%, 1.39%, 1.34%, 1.37% and 1.61%, respectively. The COV in the 25% window was lower than the COV of other energy windows. In the TDCS technique the photo-peak energy window 25% or 30% may be more effective to obtain emission images for higher statistics of counts, which may make scan time shorter.

PET and SPECT have been widely used to investigate the physiological function of animals in vivo. However, little efforts have been done to estimate absolute physiological parameters, i.e. blood flow of small animals. The present study was aimed at the absolute quantitation of myocardial blood flow of rats by means of the dynamic SPECT fitted with a pinhole collimator with a careful determination of the arterial input function (IF). The center-of-rotation was carefully aligned to the center of the field-of-view of a fixed gamma camera with the accuracy < 0.05 mm. A rat was placed on a rotating device that fixes the rat in a stand position. The arterial blood samples were frequently collected and their radioactivity concentration was measured using a well counter cross-calibrated to the SPECT images. Dynamic SPECT (the step-and-shoot mode) was initiated at 5 min after the injection of 201TlCl into the tail vein. Acquisition period was 10 sec at each rotation angle, and 120 view projection data were obtained. The 360-degree complete data sets were obtained at approximately 20 min interval for 5 time frames. Images were reconstructed by filtered-back projection technique with Feldkamp algorithm. The cross-calibration factor was determined using a cylindrical phantom of 5 cm diameter filled with the 201TlCl solution. Regions-of-interest were placed on the left ventricular wall to generate the tissue time activity curve (TTAC). TTAC and IF were fitted to the previously validated single-tissue compartment model to estimate the regional myocardial blood flow (rMBF) and volume of distribution (Vd) of thallium. The present system provided clear images of myocardial uptake of 201TlCl, and the time-dependent change of the tissue radioactivity concentration in regional basis, which was statistically sufficient for applying the compartment model analysis. The kinetic analysis yielded the rMBF of approximately 0.77 ml/min/g, which appeared to be an acceptable value with a consideration of contribution of partial volume effect and other error sources. Vd of approximately 91.9 ml/ml was also consistent with the know value of the potassium potential across the cell membrane. These results strongly suggested the potential of the dynamic pinhole SPECT as a tool for absolute quantitation of physiological parameters in small animals.

For the application of a kinetic model to PET data, it is necessary to obtain the arterial input function. Since arterial blood sampling is invasive and labor intensive, a method to evaluate the input function without arterial blood sampling is important. In case of the [/sup 15/O] water injection study, because of the noise in the time activity curve obtained from the PET reconstructed image round the carotid artery region, a model based evaluation method might be promised. In this study, a model function is composed or combination of blood time activity curve function and tissue time activity curve function which is generated from blood activity curve function. The present method was applied to 15 of dynamic PET scans or /sup 15/O water (10 normal subjects, 10 : Rest, and 5 : Diamox) for normal volunteers. The time activity curve obtained was fitted with the above model function. The shapes or input function obtained was in agreement with that by arterial blood sampling. The accuracy of height of the peak was 14 % and the accuracy of area under the curve was 10 %. This study supposed that present method could be used for direct extraction of the carotid artery input function from the dynamic PET image, and could be used in a quantitative CBF study using /sup 15/O water PET.

For the estimation of left ventricular (LV) contractility, the fully noninvasive measurement of the maximum elastance (E/sub max/) from the steady-state single loop of end systolic pressure volume relation (ESPVR) is attempted. For 32 patients with coronary artery disease, we performed the gated myocardial SPECT with the simultaneous measurement of radial artery pressure using automated tonometer. The left ventricular volume generated from quantitative gated SPECT (QGS) program of SPECT and the central aortic pressure transferred from radial artery pressure measured by automated tonometer were used to make a pressure-volume (PV) loop. With a single PV loop, E/sub max/, was calculated using (1) single PV loop estimation method based on the consistency of normalized elastance curve and (2) regression method based on time-linearity of elastance, respectively. The values of E/sub max/ by the first method were distributed within the range (2.3-5.3) and showed the independence on calculation trials and initial condition for iterative calculation. Normalized elastance curves were consistent for all patients. The E/sub max/ and V/sub 0/ for PV data from sequential gated SPECT acquisition showed the consistent value, respectively (r=0.91 for E/sub max/, r=0.99 for V/sub 0/). The values of E/sub max/ by the second method were within (0.7-5.1) and showed the linear relationship (E/sub max normalized/=2.15/spl times/E/sub max linear/+0.45, r=0.64, p