Diagnostic Performance of 123I-FPCIT SPECT Specific Binding Ratio in Progressive Supranuclear Palsy: Use of Core Clinical Features and MRI for Comparison.

OBJECTIVE. Progressive supranuclear palsy (PSP) is listed as a core clinical feature in the Movement Disorder Society 2017 criteria, along with ocular motor dysfunction, postural instability, akinesia, and cognitive dysfunction. Imaging evidence shows predominant mid-brain atrophy and postsynaptic striatal dopaminergic degeneration as two supportive features. The purpose of this study was to investigate the diagnostic performance of 123I-N- ω-fluoropropyl-2ß-carbomethoxy-3ß-(4-iodophenyl) nortropane (123I-FP-CIT) SPECT by comparing it with evaluation of core clinical features and MRI in the diagnosis of PSP. MATERIALS AND METHODS. The study included 53 patients with clinically suspected PSP who had undergone 123I-FP-CIT SPECT and MRI examinations. MR parkinsonism index (MRPI) was used as the MRI index. For the 123I-FP-CIT SPECT index, specific binding ratio (SBR) was calculated as the average of the right and left SBRs. RESULTS. In regard to core clinical features, ocular motor dysfunction was present in 15 of 20 (75.0%) patients with the diagnosis of probable PSP (p < 0.0001). Calculation of the diagnostic performance of the imaging parameters showed that MRPI (cutoff > 11.6) had 85.0% sensitivity, 100% specificity, and 94.3% accuracy. SBR (cutoff < 3.7) had 95.0% sensitivity, 36.4% specificity, and 58.5% accuracy. CONCLUSION. Iodine-123-labeled FP-CIT SPECT has high sensitivity, and MRI has high specificity in the diagnosis of PSP. Because these tools have complementary roles, reach ing a more confident clinical diagnosis of PSP may be possible when both are used.

Prediction of left main or 3-vessel disease using myocardial perfusion reserve on dynamic thallium-201 single-photon emission computed tomography with a semiconductor gamma camera.

BACKGROUND: Myocardial perfusion imaging (MPI) may fail to detect balanced ischemia. We evaluated myocardial perfusion reserve (MPR) using Tl dynamic single-photon emission computed tomography (SPECT) and a novel cadmium zinc telluride (CZT) camera for predicting 3-vessel or left main coronary artery disease (CAD). METHODS AND RESULTS: A total of 55 consecutive patients with suspected CAD underwent SPECT-MPI and coronary angiography. The MPR index was calculated using the standard 2-compartment kinetic model. We analyzed the utility of MPR index, other SPECT findings, and various clinical variables. On multivariate analysis, MPR index and history of previous myocardial infarction (MI) predicted left main and 3-vessel disease. The area under the receiver operating characteristic curve was 0.81 for MPR index, 0.699 for history of previous MI, and 0.86 for MPR index plus history of previous MI. MPR index ≤1.5 yielded the highest diagnostic accuracy. Sensitivity, specificity, and accuracy were 86%, 78%, and 80%, respectively, for MPR index, 64%, 76%, 73% for previous MI, and 57%, 93%, and 84% for MPR index plus history of previous MI. CONCLUSIONS: Quantification of MPR using dynamic SPECT and a novel CZT camera may identify balanced ischemia in patients with left main or 3-vessel disease.

Quantitative index calculated by (99m)Tc-GSA scintigraphy.

(99m)Tc-galactosyl human serum albumin (GSA) scintigraphy is useful to evaluate hepatic function and hepatic functional reserve. A reliable SPECT and CT integrated system is now commercially available. Using this system, we can obtain (99m)Tc-GSA SPECT/CT fused imaging with a small registration error. Therefore, the (99m)Tc-GSA scintigraphy techniques prove more useful in clinical practice than have been previously reported. In the latest Annals of Surgical Oncology on Oct 2014, the uptake index (UI) values calculated from (99m)Tc-GSA scintigraphy are reported to be useful for predicting the functional reserve of the future remnant liver. In this paper, we describe the usefulness of (99m)Tc-GSA scintigraphy as well as some cautions that are necessary as regards using the system.

[Correction of Partial Volume Effect Using CT Images in Brain 18F-FDG PET].

PURPOSE: We performed partial volume effect correction of PET images using 18F-FDG-PET and CT images taken consecutively, compared it with correction using MRI images, and investigated the usefulness of correction using CT images. METHODS: A total of 9 clinically normal subjects were included in the study, and the CT and MRI images of each subject were segmented and normalized. PET images were coregistered to each morphological image and then normalized. The normalized morphological images of each subject were used to mask the brain atlas and to correct for the partial volume effect. For each brain region, comparison of counts, two-group test between CT- and MRI-corrected groups, and correlation analysis were performed. RESULTS: As a result of correction, some error was observed between the two groups. Correlation analysis showed strong positive correlations in many areas, but weak correlations were found in some areas. In the region where significant differences were found, the two groups showed strong positive correlation, and in the region where weak correlation was found, the error tended to be small. CONCLUSION: It is suggested that the correction by CT can be performed with the same accuracy, although some errors are generated compared with MRI.

[Usefulness of the collimator detector response (CDR) recovery and the scatter correction by the effective scatter source estimation (ESSE) method in myocardial SPECT study].

UNLABELLED: The aim of this study was to evaluate the usefulness of the collimator detector response (CDR) recovery and the effective scatter source estimation (ESSE) method which is the scatter correction method built into the ordered subsets expectation maximization (OSEM) method. METHOD: The SPECT quality evaluation phantom and the anthropomorphic torso phantom were used in this study, and image contrast and uniformity were evaluated. The effect of each image correction method on the quantification of absolute radioactivity was also assessed. RESULTS AND CONCLUSION: Image contrast and uniformity were improved with the combination of the CDR recovery and triple energy window (TEW) method or the ESSE method. The combination of the CDR recovery and the ESSE method was the best method for the estimation of absolute radioactivity. Image quality of the SPECT is improved by the combination of CDR recovery and scatter correction in addition to attenuation correction. CDR recovery in addition to attenuation and scatter correction is also useful for the quantification of absolute radioactivity.

[A fundamental study of non-contrast enhanced MR angiography using ECG gated-3D fast spin echo at 3.0 T].

Contrast-enhanced magnetic resonance angiography (CE-MRA) is frequently performed in body and extremity studies because of its superior ability to detect the vascular stenosis. However, nephrotoxicity of the contrast medium has been emphasized in recent years. Non-contrast MRA using the three-dimensional electrocardiogram-synchronized fast spin echo method (FBI, NATIVE and TRANCE) is recommended as a substitute for CE-MRA. There are a few reports in the literature that evaluate the detectability of vascular stenosis using non-contrast MRA on 3.0 T MRI. The purpose of this study was to evaluate the detectability of vascular stenosis using non-contrast MRA at 3.0 T with an original vascular phantom. The vascular phantom consisted of silicon tubes. 30% and 70% stenosis of luminal diameter were made. Each silicon tube connected a pump producing a pulsatile flow. A flowing material to was used in this study to show the similarity of the intensity to blood on MRI. MRA without a contrast medium (NATIVE sequence) were performed in the vascular phantom by changing the image matrix, static magnetic field strength and flow velocity. In addition, the NATIVE sequence was used with or without flow compensation. Vascular stenosis was quantitatively estimated by measurement of the signal intensities in non-contrast MRA images. MRA with NATIVE sequence demonstrated an accurate estimation of 30% vascular stenosis at slow flow velocity. However, 30% stenosis was overestimated in cases of high flow velocity. Estimation was improved by using a flow compensation sequence. 70% stenosis was overestimated on MRA with NATIVE sequence. Estimation of 70% stenosis was improved by using a flow compensation sequence. Accurate estimation of vascular stenosis in MRA with a NATIVE sequence is improved by using the flow compensation technique. MRA with NATIVE sequence is considered to be a promising method for the evaluation of patients with severe renal dysfunction as a substitute for CT angiography or CE-MRA.

A diagnostic strategy for Lewy body disease using DAT-SPECT, MIBG and Combined index.

PURPOSE: The functional imaging methods widely used for the diagnosis of Lewy body disease (LBD) are 123I-N-ω-fluoropropyl-2ß-carbomethoxy-3ß-(4-iodophenyl) nortropan (FP-CIT) with dopamine transporter single photon emission computed tomography (DAT-SPECT) and 123I-iodobenzylguanidine (MIBG) myocardial scintigraphy. The aim of this study was to determine whether DAT-SPECT or 123I-MIBG myocardial scintigraphy should be examined first and to evaluate whether the combined use of DAT-SPECT and MIBG myocardial scintigraphy is superior to using either modality alone for diagnosing suspected LBD. METHODS: In this retrospective study, a total of 117 patients suspected of having LBD underwent DAT-SPECT imaging followed by MIBG myocardial scintigraphy. The delayed heart-to-mediastinum (H/M) ratio of MIBG scintigraphy, and the specific binding ratio (SBR) of DAT-SPECT imaging, and Combined index (defined as SBR mean × H/M in the delayed phase) were used as semi-quantitative measures. The diagnostic ability was evaluated using these indexes. RESULTS: The sensitivity, specificity, and accuracy of diagnosing Lewy body disease were 59.6%, 71.4%, and 67.5% by SBR mean of DAT-SPECT, 85.1%, 91.4%, and 88.9% by delayed H/M ratio of MIBG myocardial scintigraphy, 76.6%, 74.3%, and 75.2% by Combined index, respectively. CONCLUSION: In the diagnosis of LBD, DAT-SPECT, MIBG myocardial scintigraphy, and Combined index may be reliable indices. In particular, MIBG myocardial scintigraphy was the specific modality for LBD diagnosis. Understanding the effectiveness and limits of DAT-SPECT and MIBG myocardial scintigraphy and using both properly will lead to a more accurate diagnosis and better treatment.

Clinical usefulness of quantification of myocardial blood flow and flow reserve using CZT-SPECT for detecting coronary artery disease in patients with normal stress perfusion imaging.

BACKGROUND: Relative myocardial perfusion imaging can misdiagnose "balanced" ischemia caused by coronary artery disease (CAD). We assessed the feasibility of myocardial blood flow (MBF) and myocardial perfusion reserve (MPR) using dynamic single-photon emission computed tomography (SPECT) with a cadmium-zinc-telluride (CZT) camera for estimating underlying CAD in patients with normal stress myocardial perfusion SPECT (MPS). METHODS: 125 patients with normal stress MPS (summed stress score ≤3) were enrolled. All patients underwent coronary angiography (CAG) and stress/rest 201Tl dynamic SPECT for MBF and MPR calculation. The diagnostic accuracy of both these quantitative values and other clinical risk factors for predicting occult CAD were validated by CAG. RESULTS: MPR was 2.85 in patients with no CAD, 2.47 with 1-, 1.98 with 2-, and 1.76 with 3-vessel CAD. The patient's age, morbidity of diabetes mellitus (DM), chronic kidney disease (CKD), stress MBF, and MPR were significantly associated with the presence of CAD (age, p=0.02; DM, p=0.005; CKD, p=0.005; creatinine level, p= 0.012, stress MBF, p=0.019, and MPR, p<0.001). Independent predictors in the multivariate regression analysis were as follows: DM, p=0.011, CKD, p=0.028, and MPR, p<0.001. The combined index was calculated from three independent predictors. Area under the receiver operating characteristic curve was 0.75 for MPR and 0.81 for the combined index. To identify CAD, sensitivity, and specificity for MPR were 77% and 66%, and for the combined index they were 79% and 66%, respectively. CONCLUSION: Quantification of MPR and MBF using dynamic SPECT with a CZT camera can be useful to identify balanced ischemia caused by occult CAD in patients with normal stress MPS findings.

Correlation of C-reactive protein with disease severity in CT diagnosed emphysema.

BACKGROUND AND OBJECTIVE: Recent studies suggest that CRP levels are related to airflow obstruction. However, limited data exist on the relevance of CRP levels in individuals with or without emphysema. The aim of this study was to assess the relationship between the extent of emphysema, COPD severity and serum CRP levels. METHODS: Lung function tests and high-sensitivity CRP were examined in 651 males with stable disease who underwent CT screening for lung cancer. CRP levels were examined cross-sectionally in individuals with various degrees of emphysema and in those without emphysema. RESULTS: Emphysema was detected in 179 (34.7%) of 516 current smokers. Airflow obstruction was observed in 47 (28.8%) of 163 smokers with mild emphysema, in eight (57.1%) of 14 smokers with moderate emphysema, and in two of two individuals with severe emphysema. CRP levels were not higher in individuals with mild or moderate emphysema compared with individuals without emphysema. Among 98 individuals with airflow obstruction (19.0% of the 516 current smokers), there was a modest correlation between CRP levels and FEV(1)%. CONCLUSIONS: The severity of COPD varied in individuals with similar degrees of emphysema. CRP levels were not significantly higher in individuals with mild or moderate emphysema compared with individuals without emphysema but CRP levels were modestly correlated with FEV(1)% among individuals with airflow obstruction.

[Effect of reconstruction parameters on a calculation of left ventricular volumes by OS-EM reconstruction algorithm including various image corrections].

UNLABELLED: The aim of this study was to evaluate the effect of reconstruction parameters on the measurement of global left ventricular (LV) volume and define the appropriate reconstruction parameters when using the ordered subsets expectation maximization (OS-EM) method and 3D OS-EM (Astonish) method including the collimator distance response (CDR) recovery (RC) for myocardial perfusion SPECT study. METHOD: An anthropomorphic torso phantom with a 56 ml LV part was used. The LV volume was calculated with QPS software by the Update number (iteration number x subsets number) of OS-EM and 3D OS-EM (Astonish). RESULTS AND CONCLUSION: LV volumes calculated with OS-EM and Astonish without attenuation and scatter corrections corresponded to the true obtained by the Update number about 32 times and 24 times when using the OS-EM and Astonish method with attenuation and scatter corrections, respectively. However, LV volumes have changed greatly in the Astonish method according to the change in the Update number. Appropriate numbers of iterations and subsets are the measurement of global LV volumes, especially when using the OS-EM algorithm with RC.

Tc-99m PMT scintigraphy in the diagnosis of pediatric biliary atresia.

PURPOSE: Hepatobiliary scintigraphy plays an important role in the differentiation of biliary atresia (BA) and non-BA. The usefulness of 99mTc-iminodiacetic acid (IDA) derivatives in BA diagnosis is reported in several papers. In contrast, there are no comprehensive data on differentiating BA from non-BA using 99mTc-N-pyridoxyl-5-methyl-tryptophan (PMT). Our objective was to evaluate the usefulness of 99mTc-PMT scintigraphy in the diagnosis of BA. MATERIALS AND METHODS: 52 infants who received 99mTc-PMT scintigraphy for suspected BA were retrospectively evaluated. Preoperative cholangiograms or follow-ups were used as the gold standard for diagnosis of BA. We analyzed the utility of 99mTc-PMT scintigraphy, various clinical and investigational parameters in the diagnosis of BA. RESULTS: The final diagnoses in this group were BA (67.3%) and non-BA (32.7%). 99mTc-PMT scintigraphy, stool color change, total bilirubin, direct bilirubin, aspartate aminotransferase (AST) and γ-glutamyl transferase (γ-GTP) led to distinguishing between BA and non-BA in univariate analysis. Subsequent multivariate logistic regression analysis indicated that 99mTc-PMT scintigraphy and γ-GTP were independent predictors of BA. The diagnostic accuracy of 99mTc-PMT scintigraphy was 94.2%. CONCLUSIONS: 99mTc-PMT scintigraphy is more accurate in the diagnosis of BA than other conventional examinations. In addition, false positives of 99mTc-PMT scintigraphy could be reduced by combining γ-GTP level monitoring.

Quantification of myocardial perfusion reserve using dynamic SPECT images of patients with chronic kidney disease.

BACKGROUND: Chronic kidney disease (CKD) is an independent risk factor for cardiovascular disorders. The aim of this study was to examine whether the quantitatively measured myocardial blood flow (MBF) or myocardial perfusion reserve (MPR), calculated by dynamic single photon emission computed tomography (SPECT) analysis using a cardiac cadmium zinc telluride (CZT) gamma camera, was related to renal dysfunction in patients with normal myocardial perfusion imaging (MPI) findings. METHODS: The study population consisted of 46 patients with CKD and 46 individuals without CKD (controls). Their MPR index was quantitatively measured using adenosine MPI with a cardiac CZT gamma camera. All assessments were with a single tissue compartment kinetic model. The K1 value was calculated on stress and at-rest images. To obtain the MPR index we divided K1 stress-by K1 at-rest values. RESULTS: The at-rest K1 value was significantly higher and the MPR index was significantly lower in patients with CKD than those without CKD [CKD vs. CONTROLS: at-rest K1 value, 0.21 (0.17-0.25) vs. 0.19 (0.16-0.22), p=0.040; MPR index, 1.86 (1.69-2.22) vs. 2.19 (1.93-2.41), p<0.001]. The stress K1 values were not significantly different. CONCLUSION: The MPR index is significantly lower in CKD patients; this is considered as being mainly due to an increase in the at-rest K1 value.

Liver Function in Areas of Hepatic Venous Congestion After Hepatectomy for Liver Cancer: 99mTc-GSA SPECT/CT Fused Imaging Study.

Background/Aim: The sacrifice of a major hepatic vein can cause hepatic venous congestion (HVC). We evaluated the effects of HVC on regional liver function using the liver uptake value (LUV), that was calculated from 99m Tc-labeled-galactosyl-human-serum-albumin ( 99m Tc-GSA) single-photon emission computed tomography (SPECT) /contrast-enhanced computed tomography (CE-CT) fused images. Patients and Methods: Sixty-two patients underwent 99m Tc-GSA SPECT/CE-CT prior to hepatectomy for liver cancer and at 7 days after surgery were divided into groups with (n=8) and without HVC (n=54). In the HVC group, CT volume (CTv) and LUV were separately calculated in both congested and non-congested areas. Results: The remnant LUV/CTv of the HVC group was significantly smaller than that of the non-HVC group (p<0.01). The mean functional ratio was 0.47±0.05, and all ratios were ≥0.39. Conclusion: After hepatectomy with sacrifice of major hepatic vein, liver function per unit volume in the congested areas was approximately 40% of that in the non-congested areas.

Impact of FDG-PET/CT imaging on nodal staging for head-and-neck squamous cell carcinoma.

PURPOSE: To evaluate the impact of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) imaging on nodal staging for head-and-neck squamous cell carcinoma (SCC). METHODS AND MATERIALS: The study population consisted of 23 patients with head-and-neck SCC who were evaluated with FDG-PET/CT and went on to neck dissection. Two observers consensually determined the lesion size and maximum standardized uptake value (SUVmax) and compared the results with pathologic findings on nodal-level involvement. Two different observers (A and B) independently performed three protocols for clinical nodal staging. Methods 1, 2, and 3 were based on conventional modalities, additional visual information from FDG-PET/CT images, and FDG-PET/CT imaging alone with SUV data, respectively. RESULTS: All primary tumors were visualized with FDG-PET/CT. Pathologically, 19 positive and 93 negative nodal levels were identified. The SUVmax overlapped in negative and positive nodes <15 mm in diameter. According to receiver operating characteristics analysis, the size-based SUVmax cutoff values were 1.9, 2.5, and 3.0 for lymph nodes <10 mm, 10-15 mm, and >15 mm, respectively. These cutoff values yielded 79% sensitivity and 99% specificity for nodal-level staging. For Observer A, the sensitivity and specificity in Methods 1, 2, and 3 were 68% and 94%, 68% and 99%, and 84% and 99%, respectively, and Method 3 yielded significantly higher accuracy than Method 1 (p = 0.0269). For Observer B, Method 3 yielded the highest sensitivity (84%) and specificity (99%); however, the difference among the three protocols was not statistically significant. CONCLUSION: Imaging with FDG-PET/CT with size-based SUVmax cutoff values is an important modality for radiation therapy planning.

Role of cardiac computed tomography in patients with suspected coronary artery disease: interaction with nuclear cardiology.

Coronary computed tomography (CT) angiography (CTA) and myocardial perfusion single photon emission CT (SPECT, or MPS) provide complementary information on vascular structure and myocardial perfusion. In patients with coronary artery disease (CAD), the combination of both methods is helpful for disease detection and therapeutic strategy planning. This article addresses the utility of coronary CTA with current 64-row multidetector CT instruments, MPS, and the combination of these methods in the evaluation of CAD.

Case report of intralobar pulmonary sequestration detected by lung cancer screening with low-dose spiral CT.

A 52-year-old man underwent lung cancer screening with low-dose spiral computed tomography (CT) in a medical check-up at the Japanese Red Cross Kumamoto Health Care Center. He was asymptomatic. Chest x-ray on a medical check-up showed no abnormal shadows. CT scans revealed a nodule in the right lower lung, suggestive of its connection to the descending thoracic aorta. A diagnosis of pulmonary sequestration was considered. He was transferred to Kumamoto University Hospital for further examination. Contrast enhanced multidetector CT images demonstrated that a nodule in the right lower lobe and an anomalous artery ran from the descending thoracic aorta, flowed through the right lower lobe and returned to the right inferior pulmonary vein. Intralobar pulmonary sequestration was confirmed by contrast enhanced multidetector CT. We report this case of asymptomatic intralobar pulmonary sequestration diagnosed using contrast enhanced multidetector CT.

Diagnosis of dementia with Lewy bodies: can 123I-IMP and 123I-MIBG scintigraphy yield new core features?

OBJECTIVE: Since the clinical symptoms of different types of dementia frequently overlap, especially in the earlier stages at onset, it is difficult to distinguish dementia with Lewy bodies (DLB) from other neurodegenerative dementias based on their clinical manifestations alone. Nuclear medicine imaging has been reported as a high-value index for the objective evaluation and diagnosis of DLB. The aim of this study was to evaluate whether nuclear medicine imaging findings may yield core features to be added to the diagnosis of DLB. METHODS: We enrolled 332 patients with suspected DLB. All were evaluated by both 123I-metaiodobenzylguanidine (123I-MIBG) myocardial scintigraphy and 123I-labelled N-isopropyl-p-iodoamphetamine (123I-IMP). brain perfusion single-photon emission CT. The final clinical diagnosis indicated probable DLB in 92 patients (40 males, 52 females; mean age ± standard deviation, 77.4 ± 6.4 years; range, 56-89 years); 240 patients (98 males, 142 females; mean age, 75.5 ± 9.0 years; range, 70-87 years) were recorded as being without DLB. The accepted core features used for clinical evaluations were fluctuating cognition, visual hallucinations and Parkinsonism. The nuclear medicine evaluation indices were the severity score of cerebral blood flow on 123I-IMP scintigraphs of the posterior cingulate and praecuneus and a reduction in the blood flow in the occipital lobe. For 123I-MIBG evaluation, we recorded the early and delayed heart-to-mediastinum (H/M) ratios and the washout rate. RESULTS: Univariate and multivariate analyses of fluctuating cognition, visual hallucinations, Parkinsonism and early H/M ratio in patients with probable and without DLB revealed significant differences. Parameters based on 123I-IMP studies did not show any significant differences by multivariate analysis. The area under the curve for the early H/M ratio was 0.918; for fluctuating cognition, visual hallucinations and Parkinsonism, it was 0.693, 0.760 and 0.611, respectively, by receiver-operating characteristic analysis. The early H/M ratio of <2.0 on 123I-MIBG scintigraphs was of the highest diagnostic accuracy. The sensitivity, specificity and accuracy for the diagnosis of probable DLB were 82.4%, 96.3% and 92.5%, respectively. CONCLUSION: The early H/M ratio obtained by 123I-MIBG myocardial scintigraphy can serve as a reliable diagnostic index for the core clinical features of DLB. It can be used for the early diagnosis and treatment of DLB. Advances in knowledge: 123I-MIBG myocardial scintigraphy performed at the initial clinical examination can facilitate the early identification or exclusion of DLB and the early H/M ratio may be a diagnostic biomarker for DLB.

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.

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.