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ABSTRACT: Thirty-one patients suffering from single vessel exertional angina with collaterals (Group A) were evaluated by stress 201T1 myocardial emission CT (T1-SPECT) with 16 controls of severely stenotic single vessel exertional angina without collaterals (Group B). Group A included 21 patients (68%) who showed an extensive perfusion defect in double artery myocardial regions, including the normal donor artery myocardial region (DMR). However, there were no such cases in Group B, giving a significant difference between these 2 groups (p < 0.001). Four patients in Group A, having a perfusion defect both in DMR and in the collateral dependent myocardial region (CMR) underwent a successful percutaneous transluminal coronary angioplasty (PTCA) with disappearance of collaterals. T1-SPECT findings after PTCA showed no perfusion defect either in CMR or in DMR. This has been explained on the basis that the coronary collaterals stole blood and produced perfusion defect in DMR.
01/2010; 33(1):10-15.
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R Murakami,
H Uozumi,
T Hirai,
R Nishimura,
S Katsuragawa,
S Shiraishi,
R Toya,
K Tashiro,
K Kawanaka,
N Oya, S Tomiguchi,
Y Yamashita
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ABSTRACT: Although gross tumor volume (GTV) at the primary site can predict local control of head-and-neck squamous cell carcinoma (SCC) in patients who are treated with organ-preservation therapy, GTV assessment does not eliminate substantial interobserver variation.
To evaluate whether F-18-fluorodeoxyglucose positron emission tomography (FDG-PET)/computed tomography (CT) fused imaging provides additional information for GTV assessment.
We obtained FDG-PET/CT fused images on 20 patients with head-and-neck SCC. All had undergone preoperative conventional workup, including contrast-enhanced CT and magnetic resonance imaging (MRI). The GTV of the primary tumors was designed by two independent observers who used routine clinical data. Observer A was a radiologist and observer B a radiation oncologist. GTV1 and GTV2 were designed without and with FDG-PET/CT, respectively. For geometric interobserver comparison, we calculated the concordance rate as the ratio of the intersection (AxB) of the GTVs to their union (AxB). Intermethod (GTV1 vs. GTV2) and interobserver (A vs. B) differences in the GTVs were assessed by Bland-Altman analysis and the Spearman rank-correlation test. The interobserver concordance rates for GTV1 and GTV2 were compared using a two-tailed paired-samples t test.
On FDG-PET/CT, all primary tumors were visualized. There was no systemic trend for a volume difference between GTV1 and GTV2. Although the 95% limits of agreement were wider for interobserver than intermethod differences, the 95% limits of interobserver agreement were narrower for GTV2 than GTV1. The mean interobserver concordance rate for GTV2 was higher than for GTV1 (54.5% vs. 39.1%, P=0.0002).
FDG-PET/CT is a useful modality for consistent GTV assessment, which should not be used as a single modality but rather to obtain supplemental information in patients with head-and-neck SCC.
Acta Radiologica 08/2008; 49(6):693-9. · 1.37 Impact Factor
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A Kojima,
K Kawanaka,
T Nakaura,
S Shiraishi,
D Utsunomiya,
N Katsuda, S Tomiguchi,
Y Yamashita,
M Matsumoto,
N Motomura,
T Ichihara
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ABSTRACT: Attenuation correction is very important for quantitative SPECT imaging. We designed an uncollimated non-uniform line array source (non-uniform LAS) for attenuation correction based on transmission computed tomography (TCT) using Tc-99m and compared its performance with an uncollimated uniform line array source (uniform LAS) in a thorax phantom study. This non-uniform LAS was attached to one camera head of a dual-head gamma camera, and transmission data were acquired with another camera head with a low-energy, general purpose, parallel-hole collimator at 50 cm-distance apart from the source. The modified TEW using a subtraction factor of 1.0 was employed to correct scattered Tc-99m photons for transmission data. In the phantom experiment, eight TCT data were acquired with the scanning time changed from 2 minutes to 20 minutes for each LAS. The Tc-99m attenuation coefficient (mu) maps with the non-uniform LAS and uniform LAS improved the statistical count variation in the mediastinum filled with water as the scanning time got longer. The Tc-99m mu-map with the non-uniform LAS and 6 minutes of scanning time had equal quality at the center of the thorax phantom to that with the uniform LAS and 16 minutes of scanning time. In conclusion, for the TCT imaging with combination of the parallel hole collimator and uncollimated Tc-99m external source the non-uniform LAS can reduce the Tc-99m radioactivity or the TCT scanning time compared with the uniform LAS.
Annals of Nuclear Medicine. 01/2004;
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A Kojima, S Tomiguchi,
K Kawanaka,
D Utsunomiya,
S Shiraishi,
T Nakaura,
N Katsuda,
M Matsumoto,
Y Yamashita,
N Motomura,
T Ichihara
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ABSTRACT: For transmission computed tomography (TCT) systems using a centered transmission source with a fan-beam collimator, the transmission projection data are truncated. To achieve sufficiently large imaging field of view (FOV), we have designed the combination of an asymmetric fan-beam (AsF) collimator and a small uncollimated sheet-source for TCT, and implemented AsF sampling on a two-head SPECT system. The purpose of this study is to evaluate the feasibility of our TCT method for quantitative emission computed tomography (ECT) in clinical application. Sequential Tc-99m transmission and Tl-201 emission data acquisition were performed in a cardiac phantom (30 cm in width) with a myocardial chamber and a patient study. Tc-99m of 185 MBq was used as the transmission source. Both the ECT and TCT images were reconstructed with the filtered back-projection method after scatter correction with the triple energy window (TEW) method. The attenuation corrected transaxial images were iteratively reconstructed with the Chang algorithm utilizing the attenuation coefficient map computed from the TCT data. In this AsF sampling geometry, an imaging FOV of 50 cm was yielded. The attenuated regions appeared normal on the scatter and attenuation corrected (SAC) images in the phantom and patient study. The good quantitative accuracy on the SAC images was also confirmed by the measurement of the Tl-201 radioactivity in the myocardial chamber in the phantom study. The AsF collimation geometry that we have proposed in this study makes it easy to realize TCT data acquisition on the two-head SPECT system and to perform quantification on Tl-201 myocardial SPECT.
Annals of Nuclear Medicine. 01/2004;
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ABSTRACT: We investigated scatter correction in transmission computed tomography (TCT) imaging by the combination of an uncollimated transmission source and a parallel-hole collimator. We employed the triple energy window (TEW) as the scatter correction and found that the conventional TEW method, which is accurate in emission computed tomography (ECT) imaging, needs some modification in TCT imaging based on our phantom studies. In this study a Tc-99m uncollimated line array source (area: 55 cm x 40 cm) was attached to one camera head of a dual-head gamma camera as a transmission source, and TCT data were acquired with a low-energy, general purpose (LEGP), parallel-hole collimator equipped on the other camera head. The energy spectra for 140 keV-photons transmitted through various attenuating material thicknesses were measured and analyzed for scatter fraction. The results of the energy spectra showed that the photons transmitted had an energy distribution that constructs a scatter peak within the 140 keV-photopeak energy window. In TCT imaging with a cylindrical water phantom, the conventional TEW method with triangle estimates (subtraction factor, K = 0.5) was not sufficient for accurate scatter correction (micro = 0.131 cm(-1) for water), whereas the modified TEW method with K = 1.0 gave the accurate attenuation coefficient of 0.153 cm(-1) for water. For the TCT imaging with the combination of the uncollimated Tc-99m line array source and parallel hole collimator, the modified TEW method with K = 1.0 gives the accurate TCT data for quantitative SPECT imaging in comparison with the conventional TEW method with K = 0.5.
Annals of Nuclear Medicine. 01/2004;
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ABSTRACT: We looked at regional cerebellar blood flow in patients with Minamata disease (MD) using technetium-99m ethyl cysteinate dimer (99m-Tc-ECD). We carried out single-photon emission computed tomography (SPECT) on 15 patients with MD (eight men, seven women, aged 51-78 years, mean 70.5 years) and 11 control subjects (eight men, three women, aged 62-80 years, mean 72.5 years). Regional blood flow was measured in the superior, middle, and inferior portions of the cerebellar hemispheres, and the frontal, temporal and occipital cerebral lobes. The degree of cerebellar atrophy was assessed on MRI. There were significant differences in regional blood flow in all parts of the cerebellum between patients and control, but no significant decrease was observed in the cerebrum. Blood flow was lower in the inferior cerebellum than in the other parts. Even in patients without cerebellar atrophy, flow was significantly decreased regional blood flow in the inferior part.
Neuroradiology 05/2001; 43(4):279-84. · 2.82 Impact Factor
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ABSTRACT: This study evaluates not only the clinical usefulness but also the problems in attenuation correction for thallium-201 (Tl-201) myocardial SPECT by means of simultaneous transmission and emission data acquisition in the detection of coronary artery disease (CAD).
A three-detector SPECT system equipped with a Tc-99m line source and fan-beam collimators was used for simultaneous transmission and emission data acquisition for Tl-201 myocardial SPECT in 73 patients (18 patients for normal database and 55 patients for the evaluation of diagnostic accuracy). Attenuation-corrected (AC) images and non-attenuation-corrected (NC) images were reconstructed with an iterative maximum-likelihood estimation-corrected (ML-EM) algorithm. Both sets of images were reoriented into the short axis. Normal database polar maps were constructed from the AC and NC images for quantitative analysis.
There was a significant difference in specificity between NC and AC images in the RCA territory and those in specificity and accuracy in the LCX territory. There was no significant difference in sensitivity found between NC and AC images in either territory, but sensitivity in both territories tended to decrease with attenuation correction. In the LAD territory, there were various changes in sensitivity and specificity observed with attenuation correction in cases with each quantitative criterion.
Diagnostic performance of significant stenosis in the RCA and LCX territories quantitatively improved with attenuation correction because of an increase in specificity, but no significant improvement in diagnostic performance was obtained in the LAD territory with attenuation correction. We recommend combined interpretation of AC and NC images and careful evaluation of any SPECT image by means of transmission computed tomography.
Annals of Nuclear Medicine 03/2001; 15(1):21-6. · 1.50 Impact Factor
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ABSTRACT: Due to the collimator aperture, the spatial resolution of SPECT data varies with source-to-detector distance. Since radius of detector rotation is bigger when scanning larger patients, the spatial resolution is degraded in these cases. Emitted gamma rays travel not only along the central axis of the collimator hole but also off-axis due to collimator aperture. However, an off-axis ray at one angle would be a central-axis ray at another angle; therefore, raw projection data at one angle can be thought of as an ensemble of central-axis rays collected from a small arc equal to collimator aperture. Thus, fine angular sampling can compensate for collimator blurring. By using sampling pitch of less than half the collimator aperture angle, compensation was performed by subtracting the weighted sum of the projection data from the raw projection data. Collimator geometry and detector rotation radius determined the weighting function. A cylindrical phantom with four different-sized rods and torso phantom for Tl-201 cardiac SPECT simulation were used for evaluation. Aperture angle of the collimator was 7 degrees. Projection sampling pitch was 2 degrees. In both phantom studies, the proposed method showed improvement in contrast and reduction of partial volume effect, thereby indicating that the proposed method can compensate adequately for image blurring caused by collimator aperture
Nuclear Science Symposium Conference Record, 2001 IEEE; 02/2001
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K Ichikado,
M Suga,
Y Gushima,
T Johkoh,
K Iyonaga,
T Yokoyama,
O Honda,
Y Shigeto, S Tomiguchi,
M Takahashi,
H Itoh,
J Ikezoe,
N L Müller,
M Ando
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ABSTRACT: To determine whether lung abnormalities at thin-section computed tomography (CT) in experimental hyperoxic lung injury correlate with the pathologic phases of diffuse alveolar damage (DAD).
Eighteen juvenile pigs were exposed to more than 80% oxygen-for 24, 48, 72, 96, or 120 hours-or room air in sealed cages. Their removed lungs were inflated with air infused through the trachea and examined with thin-section CT. Two independent observers, without knowledge of the exposure times, compared 63 areas selected on the CT scans with the corresponding pathologic and histologic findings, which were evaluated independently by two pathologists.
CT findings correlated well with histologic findings (rho = 0.86, P <.001), which corresponded to the pathologic phases of DAD. All areas of normal CT attenuation, eight of nine spared regions within areas of opacity, and two of 15 areas of ground-glass opacity corresponded to the early exudative pathologic phase of DAD. All areas that showed traction bronchiolectasis at CT corresponded to the early proliferative pathologic phase. There was good observer agreement regarding the interpretation of CT findings (kappa statistic, >0.60) and histologic results (>/=0.70).
Thin-section CT findings reflect the pathologic phases of DAD, although the early exudative phase cannot be specifically depicted by thin-section CT. Traction bronchiolectasis on a CT scan suggests progression to the proliferative phase.
Radiology 08/2000; 216(2):531-8. · 5.73 Impact Factor
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ABSTRACT: Tc-99m DTPA galactosyl human serum albumin (Tc-99m GSA) hepatic scintigraphy was performed in two patients with patent ductus venosus before and after operation. To evaluate the portosystemic shunt flow, per-rectal portal scintigraphy with I-123 N-isopropyl-p-iodoamphetamine (IMP) was undergone in the same period. The portosystemic shunt indices (PSS index) were decreased from 67.9% to 7.3% in the patient 1, and from 77.3% to 22.7% in the patient 2, respectively. Quantitative indices of Tc-99m GSA hepatic scintigraphy improved dramatically in both patients. Under microscopic examination, nearly all the hepatic cells showed signs of severe fatty degeneration. After the operation, the severe fatty degeneration was alleviated and all the hepatic cells appeared normal. I-123 IMP per-rectal portal scintigraphy and Tc-99m GSA hepatic scintigraphy were useful in evaluating the quantitative shunt flow of the persistent ductus venosus and its hepatic functional reserve.
Annals of Nuclear Medicine 07/2000; 14(3):213-6. · 1.50 Impact Factor
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ABSTRACT: Differentiation of tumor recurrence from treatment-related changes may be difficult with conventional MR imaging when newly enhancing lesions appear. Our aim was to determine the value of perfusion-sensitive contrast-enhanced MR imaging for differentiating recurrent neoplasm from nonneoplastic contrast-enhancing tissue.
Twenty patients in whom new enhancing lesions developed within irradiated regions were examined prospectively with perfusion-sensitive contrast-enhanced MR imaging. Twelve of them also underwent thallous chloride Tl 201 single-photon emission tomography (201Tl-SPECT). Normalized relative cerebral blood volume (rCBV) ratios and thallium indexes were evaluated to determine whether the new enhancing lesions were recurrent or not. Five instances of tumor recurrence and one of radiation necrosis were verified histologically; in the others, tumor recurrence was distinguished by lesions that progressively increased in size on serial MR examinations over at least 5 months, and nonneoplastic contrast-enhancing tissue was distinguished by lesions that disappeared or decreased in size on serial MR studies over at least 9 months.
When normalized rCBV ratios were higher than 2.6 or lower than 0.6, enhancing lesions were either recurrent (n = 5) or nonneoplastic contrast-enhancing tissue (n = 3), respectively. All nonneoplastic contrast-enhancing tissue had a low thallium index, whereas three of four recurrent lesions had a high index.
An enhancing lesion with a normalized rCBV ratio higher than 2.6 or lower than 0.6 may suggest tumor recurrence or nonneoplastic contrast-enhancing tissue, respectively. In these cases, further examination with 201Tl-SPECT may not be necessary. However, when the normalized rCBV ratio is between 0.6 and 2.6, 201Tl-SPECT may be useful in making the differentiation.
American Journal of Neuroradiology 06/2000; 21(5):901-9. · 2.93 Impact Factor
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ABSTRACT: We are proposing a method to accurately measure renal activity in renography using Tc-99m labeled tracers. This method uses a conjugate-view image and transmission data for attenuation correction, the triple energy window (TEW) method for scatter correction, and background correction techniques that consider the source volume for accurate background activity correction. To examine this method in planar imaging, we performed two renal phantom studies with various uniform background activity concentrations. One study used two ideal box-shaped kidney phantoms with a thickness of 2 or 4 cm in a water tank and the other study employed two real kidney-shaped phantoms in a fillable abdominal cavity. For these studies the kidney phantom-to-background activity concentration ratio (S) was changed from 5 to infinity. The transmission data were obtained with an external Tc-99m line array source. The anterior- and posterior-view emission images were acquired with a dual-headed gamma camera simultaneously and the TEW method was used to correct scatter for the emission and transmission images. The results showed that this method with both the accurate background correction and scatter correction could give depth-independent count rates and could estimate the true count rate with errors of less than 5% for all S values. However, if either accurate background correction or scatter correction was performed alone, the absolute error increased to about 50% for the smaller S values. Our proposed method allows one to accurately and simply measure the renal radioactivity by planar imaging using the conjugate-emission image and transmission data.
Medical Physics 04/2000; 27(3):608-15. · 2.83 Impact Factor
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ABSTRACT: Two new noninvasive imaging modalities, electron beam computed tomography (EBCT) and magnetic resonance imaging(MRI), have emerged in recent years and have provided images of the heart with high temporal and spatial resolution. They provides accurate information of myocardial thickness, ventricular shape and volume, wall motion, and ventricular function in patients with cardiomyopathy. In addition, myocardial damage can be evaluated using contrast media. They can give unique diagnostic information above and beyond that of more traditional noninvasive modalities such as two-dimensional echocardiography, left ventriculography and radionuclide technique because both modalities acquire images in three dimensions. They have a possibility to become an alternative modality of the left ventriculography in the diagnosis of cardiomyopathy.
Nippon rinsho. Japanese journal of clinical medicine 02/2000; 58(1):42-7.
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ABSTRACT: We have developed a new method of crosstalk correction in simultaneous dual-isotope imaging with Tl-201 and I-123 by using crosstalk ratios and a blurring filter. Single isotope myocardial studies (10 for Tl-201 and 7 for I-123) were performed with a dual energy window acquisition mode and two low energy general-purpose collimators. Then two planar images acquired with dual energy windows for a Tl-201 line source and an I-123 line source were obtained to measure line spread functions (LSFs) and crosstalk ratios for each image. The line source experiments showed that the LSFs for the Tl-201 imaging window from the single Tl-201 source were very similar to those for the I-123 imaging window from the single Tl-201 source, but the LSFs for the Tl-201 imaging window from the single I-123 source had broad shapes which differed from those for the I-123 imaging window from the single I-123. To obtain accurate I-123 crosstalk images in the Tl-201 imaging window from the I-123 images in the I-123 imaging window, we designed a low-pass blurring filter. In 7 clinical I-123 MIBG studies, I-123 window images processed with this filter became very similar to the Tl-201 window image from the single I-123 source. The method proposed in this study can accurately correct the crosstalk in dual isotope studies with Tl-201 and I-123 and is easily applicable to conventional gamma camera systems with any dual energy window acquisition mode.
Annals of Nuclear Medicine 11/1999; 13(5):317-23. · 1.50 Impact Factor
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ABSTRACT: Respiratory and cardiac motion correction may result in better turbo spin-echo (SE) imaging of the lung. To compare breath-hold cardiac-gated black-blood T2-weighted turbo SE and turbo short-inversion-time inversion-recovery (STIR) magnetic resonance (MR) imaging pulse sequences with conventional breath-hold turbo SE and half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequences for lesion conspicuity of focal lung lesions, 42 patients with focal lung lesions were prospectively studied with MR imaging at 1.5 T. Helical computed tomography was used as a reference. In comparison with the conventional breath-hold turbo SE sequence, all black-blood sequences had fewer image artifacts arising from the heart and blood flow. The overall image quality for the black-blood turbo SE and turbo STIR sequences was superior to that for the breath-hold turbo SE and HASTE sequence (P < 0.01). Not only focal lung lesions but also surrounding inflammatory changes were clearly visualized with these two sequences. With the HASTE sequence, although several slices could be obtained in one breath-hold, both the tumor and vessels appeared blurred. We conclude that T2-weighted turbo SE and turbo STIR imaging of the lung with effective suppression of flow and motion artifacts provide high-quality images in patients with focal lung lesions.
Journal of Magnetic Resonance Imaging 05/1999; 9(5):691-8. · 2.70 Impact Factor
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ABSTRACT: 99mTc-DTPA-galactosyl human serum albumin (99mTc-GSA) hepatic scintigraphy was performed in 32 patients with hepatocellular carcinoma before and after chemolipiodolization, which was performed from the right hepatic artery (RHA) in 15 patients and the proper hepatic artery (PHA) in 17 patients. Following a bolus injection of 99mTc-GSA, dynamic SPECT was performed with 1 minute rotation for 16 minutes. Data analysis was conducted by setting a region of interest (ROI) on the right liver, left liver and heart and then their time-activity curves were generated. The regional hepatic accumulation index (LHL15) and the regional uptake constant index (KU) were also calculated from the time-activity curves. In the RHA group, regional LHL15 and KU of the left lobe significantly increased, but they did not significantly increase in the PHA group. In the right lobe, no significant change in regional KU or LHL15 was observed. In the poor prognosis group, all indices in both regions decreased after chemolipiodolization, especially the value for regional KU had a poor score before chemolipiodolization. A decrease in each index in both lobes after chemolipiodolization is considered to be a sign of a poor prognosis. 99mTc-GSA dynamic SPECT scintigraphy is a useful method for evaluating the changes in regional hepatic reserve before and after chemolipiodolization.
Annals of Nuclear Medicine 01/1999; 12(6):369-73. · 1.50 Impact Factor
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ABSTRACT: Both N,N'-ethylene bis(benzohydroxamamide) [(C2(BHam)2)] and N,N'-propylene bis(benzohydroxamamide) [(C3(BHam)2)] were designed as new thiol-free chelating molecules for 99mTc radiopharmaceuticals. Synthetic procedures using oxadiazoline intermediates were developed for C2(BHam)2 and C3(BHam)2. Both C2(BHam)2 and C3(BHam)2 formed 99mTc complexes with high yields over a wide pH range (pH 3-12) at room temperature. Complexation yields of over 95% were achieved at ligand concentrations as low as 2.5 x 10(-6) M. Reversed-phase HPLC analyses indicated that both C2(BHam)2 and C3(BHam)2 formed 99mTc complexes as single species with stabilities much higher than those of 99mTc-BHam. Selective complex formation of 99mTc with the two ligands was observed in the presence of human IgG. No decomposition with low protein binding were demonstrated when the two 99mTc complexes were incubated in murine plasma. Although further structural studies are required, these findings implied that the Ham-based tetradentate ligands would serve as new chelating molecules for 99mTc radiopharmaceuticals.
Nuclear Medicine and Biology 05/1998; 25(3):295-303. · 3.02 Impact Factor
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ABSTRACT: We describe a 43-year-old Japanese female who developed hypercalcemia associated with malignant melanoma. The patient underwent three resections of tumors on her groin and buttock secondary to a bathing trunk congenital nevus, and the histopathological findings showed benign congenital nevi. At the age of 42 years, she developed a malignant melanoma under the giant pigmented nevus in her groin. Fourteen months after the diagnosis of melanoma, she developed metastases to the lung, para-aortic lymph nodes and bones accompanied by hypercalcemia resulting from a remarkable increase in the serum level of parathyroid hormone-related protein (PTHrP). The patient died from acute renal and respiratory failure. In addition, we analyzed serum levels of calcium and PTHrP in 19 patients with advanced malignant melanoma. Seven patients had hypercalcemia, and 3 had increased serum levels of PTHrP.
Dermatology 02/1998; 197(1):65-8. · 2.05 Impact Factor
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ABSTRACT: Transjugular intrahepatic portosystemic shunt (TIPS), a new therapeutic method, has been performed widely for the treatment of portal hypertension. TIPS produces a decrease in the portal blood flow to the hepatic parenchyma, which is considered to cause a reduction in hepatic functional reserve. To evaluate the changes in hepatic functional reserve after TIPS, we performed technetium-99m DTPA-galactosyl human serum algumin (99mTc-GSA) hepatic scintigraphy before and after TIPS in eight male patients, ranging in age from 54 to 72 years (mean 62.2 years). Two quantitative indices - blood clearance index (uptake ratio of the heart at 15 min to that at 3 min, HH15) and hepatic accumulation index (uptake ratio of the liver to the liver plus heart at 15 min, LHL15) - were calculated from the time-activity curves of the heart and liver. Early and late uptake constant indices (early and late KU) were also calculated from the time-activity curves of the heart and liver by means of Patlak plot. The values of HH15, LHL15 and late KU deteriorated after TIPS in all patients. Early KU (1-3 min) decreased by more than 55% in two patients who showed a poor prognosis and corresponded well with the status of the portosystemic shunt. It is concluded that 99mTc-GSA hepatic scintigraphy is a useful means of evaluating the degree to which hepatic function is compromised following TIPS. The post-TIPS alterations in HH15, LHL15 and late KU (5-10 min) reflect the changes in hepatic functional reserve, and early KU is a useful index for evaluating the degree of portosystemic shunt.
European Journal of Nuclear Medicine 11/1997; 24(10):1268-72.
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ABSTRACT: For scatter correction using the triple energy window (TEW) acquisition in 201Tl imaging, we propose an off-peak TEW (OFPTEW) method. This OFPTEW method employs a wide main energy window of 34 keV centered at 73 keV and two 5.1 keV sub-energy windows and uses the scatter correction factor of 0.55. To assess scatter correction using the OFPTEW method in 201Tl imaging, phantom studies for planar and SPECT imaging were performed and the data with the OFPTEW method were compared with those by the conventional TEW method using the trapezoidal formula with the 20% main energy window centered at 70 keV and two 4.9 keV sub-energy windows. The planar images corrected by both methods were visually similar. The OFPTEW method, however, estimated the true primary counts and the contrast value in the cold lesion accurately, while the conventional TEW method underestimated the primary counts by 30% and gave wrong contrast values. For the myocardial SPECT imaging, the short-axis images by both methods were very similar, but the images by the OFPTEW method had 1.46 times more counts than those corrected by the conventional TEW method. In conclusion, the OFPTEW method can correct scatter in 201Tl imaging accurately and increase the primary counts effectively compared with the conventional TEW method.
Kaku igaku. The Japanese journal of nuclear medicine 10/1997; 34(9):789-96.
