The purpose of this study is to optimize a parallel-hole collimator for small gamma camera having the pixellated crystal array and evaluate the effect of crystal-collimator misalignment on the image quality using a simulation tool GATE (Geant4 Application for Tomographic Emission). The spatial resolution and sensitivity were measured for the various size of hexagonal-hole and matched square-hole collimators with a Tc-99m point source and the uniformity of flood image was estimated as a function of the angle between crystal array and collimator by misalignment. The results showed that the spatial resolution and sensitivity were greatly improved by using the matched collimator and the uniformity was reduced by crystal-collimator misalignment.
Gamma Cameras

Radioisotope renogram and linear scan have been widely used for evaluating various renal disease, knowing that there was some disadvantages to be revised. Sequential study using scintillation camera readily reveals both functional and morphological alterations of the kidney with accuracy. The scintillation photographic studies on various renal conditions have been presented.
Gamma Cameras* ; Kidney

No abstract available.
Gamma Cameras* ; Head*

A study on the morphism of patients with thyroid diseases (most of them with long-term hyperthyroidism treated by antithyroid drugs and operation) was carried out on 60 scintigraphy with gamma camera. The results have shown that the scintigraphy was very good value to diagnose the thyroid nuclear, plummer, marine-lenhart syndrome and determine the proper dosage.
Thyroid Gland ; Gamma Cameras

PURPOSE: The aim of this sutdy was to evaluate the feasibility of 3-[131I]Iodo-O-methyl-L-a-methyltyrosine ([131I]OMINT) as an agent for tumor image. MATERIALS AND METHODS: After synthesis of 4-O-methyl-L-a-methyltyrosine (OMAMT), OMAMT was labeled with 131I using Iodogen method. In viro cellular uptake study was performed using 9 L gliosarcoma cells at various time points upto 4 hr. The biodistribution (five rats implanted with the 9 L gliosarcoma cells per group) was evaluated at 30 min, 2 hr, 24 hr after iv injection of 3.7 MBq [131I]OMIMT or L-3-[131I]iodo-a-methyltyrosine ([131I]IMT). Gamma camera images were obtained at 30min, 2 hr, and 24 hr. RESULTS: [131I]OMINT uptake was 3.3 times and 2.5 times higher than [131I]IMT uptake at 30 min and 60 min, respectively and same after 2 hr in in vitro sutdy using 9L gliosarcoma cells. Maximum accumulation in tumor occurred at 30 min for both [131IOMINT and [131I]IMT in tumor bearing rats. The tumor uptake of [131I]OMINT was significantly higher than that of [131I]IMT in tumor bearing rats. The tumor uptake of [131I]OMIMT was significantly higher than that of [131I]IMT at early time point studied (3.74 +/- 0.48 vs 0.38 +/- 0.17% ID/g at 30 min and 2.40 +/- 0.17 vs 0.24 +/- 0.03% ID/g at 2 hr, respectively, p<0.01). However, the tumor uptake of both radiolabels were not significantly different at 24 hr (0.04 +/- 0.01 vs 0.05 +/- 0.01% ID/g). Tumor was visualized as early as at 30 min in gamma camera images. CONCLUSION: These data suggested that [131I]OMIMT might be a useful tumor imaging agent and has more advantage for the tumor imaging compared to [131I]IMT.
Animals ; Gamma Cameras ; Gliosarcoma ; Rats*

Scatter correction for I-131 plays a very important role to improve image quality and quantitation. I-131 has multiple and higher energy gamma-ray emissions. Image quality and quantitative accuracy in I-131 imaging are degraded by object scatter as well as scatter and septal penetration in the collimator. The purpose of this study was to estimate scatter and septal penetration and investigate two scatter correction methods using Monte Carlo simulation. The gamma camera system simulated in this study was a FORTE system (Phillips, Nederland) with high energy, general-purpose, parallel hole collimator. We simulated for two types of high energy collimators. One is composed of lead, and the other is composed of artificially high Z number and high density. We simulated energy spectrum using a point source in air. We estimated both full width at half maximum (FWHM) and full width at tenth maximum (FWTM) using line spread function (LSF) in cylindrical water phantom. We applied two scatter correction methods, triple energy window scatter correction (TEW) and extended triple energy window scatter correction (ETEW). The TEW method is a pixel-by pixel based correction which is easy to implement clinically. The ETEW is a modification of the TEW which corrects for scatter by using abutted scatter rejection window, which can overestimate or the underestimate scatter. The both FWHM and FWTM were estimated as 41.2 mm and 206.5 mm for lead collimator, respectively. The FWHM and FWTM were estimated as 27.3 mm and 45.6 mm for artificially high Z and high density collimator, respectively. ETEW showed that the estimation of scatter components was close to the true scatter components. In conclusion, correction for septal penetration and scatter is important to improve image quality and quantitative accuracy in I-131 imaging. The ETEW method in scatter correction appeared to be useful in I-131 imaging.
Gamma Cameras ; Rejection (Psychology) ; Water

PURPOSE: In order to obtain better quantitation of kidney uptake, this study is to evaluate a conjugate view method (CVM) using a geometric mean attenuation correction for kidney uptake and to compare it to Gate's method. MATERIALS AND METHODS: We used a Monte Carlo code, SIMIND and a Zubal phantom, to simulate kidney uptake. SIMIND was both simulated with or without scatter for the Zubal phantom. Also, a real phantom test was carried out using a dual-head gamma camera. The activity of 0.5 mCi was infused into two small cylinder phantoms of 5 cm diameter, and then, they were inserted into a cylinder phantom of 20 cm diameter. The results by the CVM method were compared with ideal data without both of attenuation and scatter and with Gate's method. The CVM was performed with or without scatter correction. The Gate's method was performed without scatter correction and it was evaluated with regards to 0.12 cm (-1) and 0.15 cm (-1) attenuation coefficients. Data were analyzed with comparisons of mean counts in the regions of interest (ROI), profiles drawn over kidney images and linear regression. Correlation coefficients were calculated with ideal data, as well. RESULTS: In the case of the computer simulation, mean counts measured from ideal data, the CVM and the Gate's method were (right: 998 +/- 209, left: 896 +/- 249), (right: 911 +/- 207, left: 815 +/- 265), and (right: 1065 +/- 267, left: 1546 +/- 267), respectively. The ideal data showed good correlation with the CVM and the correlation coefficients of the CVM, Gate's method were (right: 0.91, left: 0.93) and (right: 0.85, left: 0.90), respectively. CONCLUSION: The conjugate view method using geometric mean attenuation correction resulted in better accuracy than the Gate's method. In conclusion, the conjugate view method independent of renal depths may provide more accurate kidney uptake.
Computer Simulation ; Gamma Cameras ; Kidney* ; Linear Models

PURPOSE: To reduce ethanol reflux from the needle channel by injecting rat blood immediately after theinjection of ethanol into rat liver. MATERIALS AND METHODS: The first experiment involved 33 rat livers whichwere divided into four groups (three livers in group 1 ; ten in groups 2, 3, and 4). Group 1 animals were used ascontrols, and 0.1ml saline was injected into the liver ; in group 2, ethanol-Tc-99m-O4- mixed solution (0.1 ml,0.2 mCi) was injected into the liver ; in groups 3 and 4, the needle channel was blocked with 0.02 ml of freshblood and old blood, respectively, after the injection of ethanol. After removing the needle, a 3cm round filterpaper was laid on each injection site to absorb refluxed ethanol-Tc-99m-O4- mixed solution from the liver, andeach paper was then counted by a gamma camera unit. In the second experiment, 33 rats were divided into fourgroups (three rats in group 1 ; ten in groups 2, 3, and 4). Group 1 animals were used as controls, and afterexposing the left lateral lobe of the liver, 0.05 ml of saline was injected; in group 2, 0.05 ml of ethanol wasinjected into the liver in groups 3 and 4 the needle channel was blocked with 0.02 ml of fresh blood and oldblood, respectively, after the injection of ethanol. After ten days, peritoneal adhesions were scoredmacroscopically and microscopically. RESULTS: In the first experiment using ethanol-Tc-99m-O4- mixed solution,groups blocked with blood after the injection of mixed solution showed lower gamma counts than the group injectedwith mixed solution only (p-value = 0.0002). The group blocked with old blood showed the lowest count.Macroscopical and microscopical examination of peritoneal adhesions indicated that the grade of adhesion was lowerin groups blocked with blood than in the group injected with ethanol only (p-value = 0.0261 and 0.0163,respectively). CONCLUSION: The above results suggest that an injection of blood after an injection of ethanol isa very effective way of preventing reflux from the liver.
Animals ; Ethanol* ; Gamma Cameras ; Liver ; Needles ; Rats*

PURPOSE: We characterized the signals obtained from the components of a small gamma camera using NaI(Tl)-position sensitive photomultiplier tube (PSPMT) and optimized the parameters employed in the modules of the system. MATERIALS AND METHODS: The small gamma camera system consists of a NaI(Tl) crystal (60x60x6 mm3) coupled with a Hamamatsu R3941 PSPMT, a resister chain circuit, preamplifiers, nuclear instrument modules (NIMs), an analog to digital converter and a personal computer for control and display. The PSPMT was read out using a resistive charge division circuit which multiplexes the 34 cross wire anode channels into 4 signals (X+, X-, Y+, Y-). Those signals were individually amplified by four preamplifiers and then, shaped and amplified by amplifiers. The signals were discriminated and digitized via triggering signal and used to localize the position of an event by applying the Anger logic. The gamma camera control and image display was performed by a program implemented using a graphic software. RESULTS: The characteristics of signal and the parameters employed in each module of the system were presented. The intrinsic sensitivity of the system was approximately 8x103 counts/sec/microcurie. The intrinsic energy resolution of the system was 18% FWHM at 140 keV. The spatial resolution obtained using a line-slit mask and 99mTc point source were, respectively, 2.2 and 2.3 mm FWHM in X and Y directions. Breast phantom containing 2~7 mm diameter spheres was successfully imaged with a parallel hole collimator. The image displayed accurate size and activity distribution over the imaging field of view. CONCLUSION: We proposed a simple method for development of a small gamma camera and presented the characteristics of the signals from the system and the optimized parameters used in the modules of the small gamma camera.
Anger ; Breast ; Electrodes ; Gamma Cameras* ; Logic ; Masks ; Microcomputers

A coded aperture camera has been developed to improve the signal-to-noise ratio (SNR) while keeping the spatial resolution of a pinhole gamma camera. The purpose of this study was to optimize a coded aperture camera and to evaluate its possibility for thyroid imaging by Monte Carlo simulation. A clinical gamma camera, a pinhole collimator with 1.0 mm hole diameter, and a 79x79 modified uniformly redundant array (MURA) mask were designed using GATE (Geant4 Application for Tomographic Emission). The penetration ratio, spatial resolution, integral uniformity and signal-to-noise ratio (SNR) were simulated and evaluated as a function of the mask thickness. The spatial resolution of the coded aperture camera was consistent with the various mask thickness, SNR showed a maximum value at 1.2 mm mask thickness and integral uniformity was improved by increasing mask thickness. Compare to the pinhole gamma camera, the coded aperture camera showed improved SNR by a factor of 30 while keeping almost the same spatial resolution. In this simulation study, the results indicated that high spatial resolution and ultra-high SNR of the thyroid imaging are feasible using a coded aperture camera.
Gamma Cameras ; Masks ; Signal-To-Noise Ratio ; Thyroid Gland