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Seiji Tomiguchi

Publications and source records attributed to Seiji Tomiguchi.

At least 19 recordsLinked to original sources
PubMed2006

Mutidetector-row CT and quantitative gated SPECT for the assessment of left ventricular function in small hearts: the cardiac physical phantom study using a combined SPECT/CT system.

UNLABELLED: The aim of this study was to compare results of left ventricular (LV) function obtained by quantitative gated single-photon emission tomography (QGS) and multidetector-row spiral computed tomography (MDCT) with reference parameters using an electrocardiogram-gated cardiac physical phantom. The phantom study was performed using a combined SPECT/CT system. Flexible membranes formed the inner and outer walls of the simulated LV. The stroke volume was adjusted (45 mL or 58 mL) and the fixed 42-mL end-systolic volume (ESV) produced two different volume combinations. The LV function parameters were estimated by means of MDCT and QGS. Differences in true and measured volumes were compared among CT with a reconstructed image thickness of 2.5 mm and 5.0 mm and QGS volumetric values. Each scan was repeated three-times. The estimation of LV volumes using both QGS and MDCT analyses were reproducible very well. QGS overestimated ejection fraction (EF) by approximately 20%; MDCT volumetry overestimated EF by approximately 5% in each volume setting. The differences in true and measured values for EF and ESV obtained with QGS were significantly greater than obtained with MDCT. CONCLUSION: MDCT provides a reliable estimation of functional LV parameters, whereas QGS tends to significantly overestimate the EF in small hearts.

Analysis of Variance↗
PubMed2006

Development of a collimator blurring compensation method using fine angular sampling projection data in SPECT.

Due to the collimator aperture, spatial resolution of SPECT data varies with source-to-detector distance. Since the radius of detector rotation is bigger when scanning larger patients, 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 the 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 the collimator aperture. Thus, fine angular sampling can compensate for collimator blurring. By using a 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. 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 the collimator aperture.

Artifacts↗
PubMed2006

Management of sentinel lymph nodes in malignant skin tumors using dynamic lymphoscintigraphy and the single-photon-emission computed tomography/computed tomography combined system.

BACKGROUND: The differentiation of true sentinel lymph nodes from nonsentinel lymph nodes is difficult in cases of multiple radiolabeled or dyed lymph nodes. METHODS: We examined the locations of sentinel lymph nodes in melanoma and other malignant skin tumors by using dynamic lymphoscintigraphy and the single-photon-emission computed tomography/computed tomography (SPECT/CT) combined system. RESULTS: Sentinel lymph nodes were detected in 45 of the 53 patients examined using only the ordinary blue dye method (85%), and were detected in all 35 patients examined using the SPECT/CT method (100%). Twenty of the 35 patients mentioned above had one sentinel lymph node. Multiple sentinel lymph nodes were demonstrated in the head and neck areas using the SPECT/CT method. Significant differences (P=0.0015) in the numbers of sentinel lymph nodes were found between the blue dye method only and the SPECT/CT method in the neck area. Popliteal sentinel lymph nodes were recognized in three patients, and cubital sentinel lymph nodes were recognized in two patients. Two patients had plural regional lymph nodes: one had popliteal and groin sentinel lymph nodes, while the other had cubital and axillary sentinel lymph nodes. The probe counts of the popliteus and cubitus were significantly lower (P=0.0241) than the counts in the groin, axilla, and neck areas. Micrometastatic sentinel lymph nodes were recognized in four patients, and two patients had metastases in both sentinel and nonsentinel lymph nodes. CONCLUSIONS: Dynamic lymphoscintigraphy was useful when we were concerned about cubital and popliteal lymph nodes. The SPECT/CT combined system was useful in recognizing the anatomical location of sentinel lymph nodes before biopsy. The detection rate of sentinel lymph nodes using the SPECT/CT method was always better than that with the blue dye method (P=0.0197).

Adult↗
PubMed2006

Quantitative analysis and effect of attenuation correction on lymph node staging of non-small cell lung cancer on SPECT and CT.

OBJECTIVE: The purpose of our study was to assess quantitative indexes and the effect of attenuation correction on the evaluation of lymph node metastasis in the staging of non-small cell lung cancer (NSCLC) using fused thallium-201 SPECT/CT images. MATERIALS AND METHODS: We evaluated 156 lymph nodes (66 metastatic, 90 nonmetastatic) from 29 patients with NSCLC. Using our combined SPECT/CT system, all patients underwent 201Tl SPECT and CT examinations immediately (early images) and 3 hr after (delayed images) the injection of 201Tl. SPECT images were reconstructed with and without attenuation correction. For the quantitative evaluation of lymph node metastasis, we calculated the early ratio, the delayed ratio, and the washout ratio for SPECT images and the short-axis diameter for CT images. Receiver operating characteristic (ROC) analysis was performed in each index for the differentiation between metastatic and nonmetastatic lymph nodes. Visual analysis was also performed by two experienced radiologists. RESULTS: The area under the ROC curve (A(z)) showed that early ratio and delayed ratio were superior to short-axis diameter for the assessment of lymph node metastasis. In addition, early and delayed ratios on attenuation-corrected images were superior to those ratios on images without attenuation correction. However, the A(z) value for washout ratio was smaller than that for short-axis diameter. Early ratio on attenuation-corrected images was the most useful index (A(z) = 0.94). The sensitivity, specificity, and accuracy for early ratio on attenuation-corrected images were 78.8%, 94.4%, and 87.8% for the diagnosis of lymph node metastasis and 84.6%, 100%, and 93.1% for clinical staging (N0-N1 vs N2-N3), respectively. Fused images showed significantly higher diagnostic accuracy than CT images on visual analysis. CONCLUSION: Quantitative assessment using fused SPECT/CT images is useful for the diagnosis of lymph node metastasis in patients with NSCLC.

Adult↗
PubMed2005

Added value of SPECT/CT fusion in assessing suspected bone metastasis: comparison with scintigraphy alone and nonfused scintigraphy and CT.

PURPOSE: To evaluate retrospectively if there is additional diagnostic value of fused single photon emission computed tomographic (SPECT) and computed tomographic (CT) images in assessing possible bone metastases. MATERIALS AND METHODS: Institutional review board approval was obtained, and each patient provided written informed consent. Bone scintigraphy--including planar and SPECT imaging-and CT were performed with a combined SPECT/CT system in 45 oncologic patients (24 men, 21 women; mean age, 64.7 years +/- 8.7), with a total of 42 metastatic bone foci and 40 benign foci. The reference standard was follow-up radiologic imaging. Two independent readers first analyzed only bone scintigraphic images and next analyzed two separate sets of bone scintigraphic and CT images. They then analyzed bone scintigraphic, CT, and fused images and focused on the additional value of fused images. Diagnostic confidence for each lesion was scored. The three analyses were performed 7 days apart, and the images were presented in random order at each session. The value of additional fused images was assessed by using receiver operating characteristic analysis. RESULTS: After review of fused images to classify indeterminate lesions, reviewer 1 became more confident in diagnosis of the 15 benign lesions and two metastases, and reviewer 2 became more confident in diagnosis of the seven benign lesions and one metastasis. The area under the receiver operating characteristic curve for reviewer 1 was 0.589 for scintigraphic images, 0.831 for separate data sets of scintigraphic and CT images, and 0.947 for fused images. The corresponding areas under the receiver operating characteristic curve for reviewer 2 were 0.771, 0.885, and 0.968, respectively. CONCLUSION: Results demonstrate the increased diagnostic confidence obtained with fused SPECT/CT images compared with separate sets of scintigraphic and CT images in differentiating malignant from benign bone lesions.

Adult↗
PubMed2005

Object-specific attenuation correction at SPECT/CT in thorax: optimization of respiratory protocol for image registration.

Institutional review board approval was obtained for multiple imaging examinations in healthy volunteers and patients and for the analysis of images. The purpose of the study, and the risks associated with radiation exposure with regard to stochastic effects that might result in cancer and/or genetic mutations, were explained to all subjects, and all questions from subjects were answered. Each subject provided written informed consent. The purpose of the study was to prospectively determine the respiratory protocol at computed tomography (CT) that results in the best registration of CT images with images acquired at single photon emission computed tomography (SPECT) in the thorax. Errors of registration between myocardial SPECT images and CT images obtained with different respiratory protocols (postinhalation breath hold, postexhalation breath hold, and free breathing) in 13 healthy subjects were compared. CT scans obtained with free breathing and postexhalation breath hold better matched SPECT images than did those obtained with postinhalation breath hold (one-way analysis of variance, P < .01). Fewer SPECT/CT images showed artifacts with registration performed by using internal landmarks (four, two, and one of 13 images with postinhalation breath-hold, postexhalation breath-hold, and free-breathing protocols, respectively) than with registration performed by using external markers (nine, four, and two of 13 images). CT data acquisition with a free-breathing or postexhalation breath-hold protocol and image registration by using internal landmarks are recommended for attenuation correction.

Adult↗
PubMed2005

Optimum energy window setting on Hg-201 x-rays photopeak for effective Tl-201 imaging.

For more effective Tl-201 imaging, the location and width of the energy window set on the Hg-201 x-rays photopeak was investigated using Monte Carlo simulation and phantom experiments. We calculated energy spectra and investigated the amount of primary and scattered photons within various energy windows set on the x-rays photopeak. The energy resolution (ER) at 71 keV (the peak of the x-rays photopeak) was changed to 10%, 12%, 14% and 16%. The relationships between the energy window and the primary counts rate or the scatter fraction (= scattered counts/primary counts, SF) were obtained. By compromise between the primary counts rate and the SF for ER = 12%, the optimum energy window was determined as a wider off-peak window, 77 keV +/- 14.3% (66-88 keV). This off-peak window increased the primary counts rate by 12.5% and decreased the SF by -17% as compared with the conventional on-peak energy window (71 keV +/- 10%, 64-78 keV). When this off-peak widow acquisition was compared with the conventional on-peak window one on a gamma camera, planar and SPECT images using the off-peak widow clearly showed superior results qualitatively and quantitatively.

Algorithms↗
PubMed2005

Initial experience with X-ray CT based attenuation correction in myocardial perfusion SPECT imaging using a combined SPECT/CT system.

OBJECTIVE: Attenuation artifacts adversely affect the diagnostic accuracy of myocardial perfusion imaging. We assessed the clinical usefulness of X-ray CT based attenuation correction (AC) in patients undergoing myocardial perfusion imaging by comparing their myocardial AC- and non-corrected (NC) SPECT images with the coronary angiography (CAG). METHODS: We retrospectively reviewed the myocardial SPECT images of 30 patients (18 men, 12 women; mean age 68 years). Thirteen of 30 patients with coronary artery disease (CAD) and 17 without CAD were confirmed by CAG. They underwent sequential CT and myocardial SPECT imaging with thallium-201 (111 MBq) under an exercise or pharmacological stress protocol using our combined SPECT/ CT system. Two readers reviewed the myocardial SPECT images for the presence of CAD on a 4-point scale where 1 = normal, 2 = probably normal, 3 = probably abnormal, and 4 = abnormal. Two reading sessions were held. First, non-corrected (NC)-SPECT and second, AC-SPECT images using X-ray CT images were interpreted. Interobserver variability was assessed with kappa statistics. Diagnostic performance (accuracy) of coronary arterial stenosis was compared between AC- and NC-images. RESULTS: Interobserver agreement for visual assessment was substantial or almost perfect. For AC-images, the observer consensus for analysis was 0.84 for the LAD-, 0.87 for the LCX-, and 0.71 for the RCA-territory. For NC-images, it was 0.91, 0.71, and 0.78. AC resulted in statistically significant improvements in overall diagnostic accuracy (sensitivity/ specificity/accuracy = 76%/93%/89%, 67%/86%/81%, respectively, for AC- and NC-images). CONCLUSIONS: Because of an increase in the specificity, diagnostic accuracy was significantly increased on AC-images. These preliminary data suggest that X-ray CT based AC in myocardial SPECT imaging has the potential to develop into a reliable clinical technique.

Aged↗
PubMed2005

Three-dimensional cardiac image fusion using new CT angiography and SPECT methods.

OBJECTIVE: The purpose of this study was to develop a method of fused images of coronary CT angiography and myocardial perfusion SPECT. CONCLUSION: Four patients with ischemic heart disease underwent 3D volume-rendering fused images using a conversion program and volume-rendering fusion function of a computer workstation. The fusion images clearly showed the relationship of relevant coronary arteries and the abnormal perfusion territory in all patients and were useful for the evaluation of coronary artery disease.

Aged↗
PubMed2004

Attenuation correction using asymmetric fanbeam transmission CT on two-head SPECT system.

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.

Aged↗
PubMed2004

Attenuation correction using combination of a parallel hole collimator and an uncollimated non-uniform line array source.

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.

Humans↗
PubMed2004

Accurate scatter correction for transmission computed tomography using an uncollimated line array source.

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.

Equipment Failure Analysis↗
PubMed2003

Struma ovarii coexisting with mucinous cystadenoma detected by radioactive iodine.

The authors describe a case of struma ovarii coexisting with mucinous cystadenoma. Ultrasonography and magnetic resonance imaging showed a multilocular cystic mass with a solid component. The ovarian tumor demonstrated uptake of I-123 sodium iodide, allowing a preoperative diagnosis of struma ovarii. In women with an unexplained increase in thyroid function and low I-123 uptake in the cervical thyroid gland, scintigraphy of the pelvis should be considered.

Adult↗
PubMed2003

[Clinical evaluation of gastric diverticulum on indirect radiograph for gastric mass survey].

The aim of this study was to evaluate the clinical conditions of gastric diverticulum. Fifty-four patients with gastric diverticulum (20 men and 34 women among 34,314 patients who underwent medical check-ups) were evaluated on indirect radiographs, for an incidence of 0.16% among the total number of examined cases, a rate lower than that of previous reports. Almost all cases were asymptomatic, had a single diverticulum, and showed a saccular shape. The age distribution indicated higher frequencies in the 5th and 6th decades, and the posterior wall of the fornix was the most common location. Size ranged from 0.6 cm to 12 cm, and 41 cases (75.9%) were between 1.0 cm and 4.0 cm in size. This entity should be kept in mind when reading radiographs of upper gastrointestinal series as well as recognition of pseudodiverticulum and aberrant pancreas as noted for the stomach in several past report. Diverticulum on the cardia, which was previously classified as gastric diverticulum, should be excluded because of the possibility of normal variation.

Adult↗
PubMed2002

[Multi-center study for the evaluation of clinical usefulness of attenuation and scatter correction on 201Tl myocardial SPECT].

The aim of this study was to evaluate the clinical usefulness of attenuation and scatter correction (AC, SC) on a 201Tl myocardial single-photon emission computed tomography (201Tl SPECT) as a multi-center trial. With a dual-detecter and a triple-detector SPECT systems with a 99mTc transmission source, simultaneous transmission/emission tomography (TCT/ECT) was performed on 38 patients with angiographically coronary heart disease (CHD) and 26 patients without evidence of CHD. Stress and delayed attenuation and scatter corrected images (SAC) and uncorrected images (NC) were reconstructed. On NC images of normal cases, influence of attenuation was greater in male than female. In comparison of 201Tl distribution between male and female, significant decrease in 201Tl activity was observed in the inferoposterior wall in male and that was observed in the anterobasal wall of the left myocardium in female. Such a difference in 201Tl distribution between male and female disappeared on SAC images. On the diagnostic performance for the identification of CHD, SAC images demonstrated improved specificity and accuracy values in the right coronary arterial territory (RCA) with visual analysis statistically. Sensitivity value in the RCA was also improved, but it was not statistically significant. Sensitivity value in the left circumflex arterial territory (LCX) increased without decrease in specificity value on SAC images. In the left anterior descending arterial territory (LAD), sensitivity value increased on SAC images. Although specificity value decreased on SAC images in LAD territory, it was not statistically significant. The difference in 201Tl distribution between male and female is improved in normal cases by attenuation and scatter correction on 201Tl myocardial SPECT. Diagnostic performance of CHD is also improved by attenuation and scatter correction, especially in territories of which specificity in assessing the absence of disease have been suboptimal. In conclusion, attenuation and scatter correction on 201Tl myocardial SPECT is considered to be clinically useful.

Adult↗
PubMedDate not supplied

Comparison of fusion imaging using a combined SPECT/CT system and intra-arterial CT: assessment of drug distribution by an implantable port system in patients undergoing hepatic arterial infusion chemotherapy.

Hepatic arterial infusion (HAI) chemotherapy is effective for treating primary and metastatic carcinoma of the liver. We compared the perfusion patterns of HAI chemotherapy on intra-arterial port-catheter computed tomography (iapc-CT) and fused images obtained with a combined single-photon emission computed tomography/computed tomography (SPECT/CT) system. We studied 28 patients with primary or metastatic carcinoma of the liver who bore an implantable HAI port system. All underwent abdominal SPECT using Tc-99m-MAA (185 Mbq); the injection rate was 1 mL/min, identical to the chemotherapy infusion rate, and 0.5 mL/sec for iapc-CT. Delivery was through an implantable port. We compared the intrahepatic perfusion (IHP) and extrahepatic perfusion (EHP) patterns of HAI chemotherapy on iapc-CT images and fused images obtained with a combined SPECT/CT system. In 23 of 28 patients (82%), IHP patterns on iapc-CT images and fused images were identical. In 5 of the 28 patients (18%), IHP on fusion images was different from IHP on iapc-CT images. EHP was seen on fused images in 12 of the 28 patients (43%) and on iapc-CT images in 8 patients (29%). In 17 patients (61%), upper gastrointestinal endoscopy revealed gastroduodenal mucosal lesions. EHP was revealed on fused images in 10 of these patients; 9 of them manifested gastroduodenal toxicity at the time of subsequent HAI chemotherapy. Fusion imaging using the combined SPECT/CT system reflects the actual distribution of the infused anticancer agent. This information is valuable not only for monitoring adequate drug distribution but also for avoiding potential extrahepatic complications.

Adult↗
PubMedDate not supplied

Evaluation of extrahepatic perfusion of anticancer drugs in the right gastric arterial region on fused images using combined CT/SPECT: is extrahepatic perfusion predictive of gastric toxicity?

BACKGROUND: Hepatic arterial infusion (HAI) chemotherapy is effective for treating primary and metastatic carcinomas of the liver. Since hepatic arteries also supply the stomach and duodenum, HAI may result in unwanted infusion into the upper gastrointestinal tract and consequent gastric toxicity. Using fused images obtained with a combined SPECT/CT system, we assessed extrahepatic perfusion (EHP) and its correlation with gastrointestinal toxicity in patients receiving HAI. METHODS: We studied 41 patients with primary or metastatic carcinoma of the liver who received HAI chemotherapy consisting of 5-fluorouracil and cisplatin. All underwent abdominal SPECT using a (99m)Tc-MAA (185 MBq) instrument and an injection rate of 0.1 ml/min, identical to the chemotherapy infusion rate. Delivery was through an implantable port. We analyzed the distribution of the anticancer agent on fused images and the relationship between EHP of the right gastric arterial region and gastric toxicity. All patients underwent esophagogastroduodenoscopy (EGDS). RESULTS: Of the 41 patients, 11 (27%) manifested enhancement of the duodenal and gastric pyloric region on fused images. EGDS at the time of reservoir placement detected gastric ulcers in 10 of these patients. CONCLUSION: Fusion imaging with combined SPECT/CT reflects the actual distribution of the infused anticancer agents. The detection of EHP on fused images is predictive of the direct gastric toxicity from anticancer agents in patients undergoing HAI.

Adult↗