Phase analysis by gated F-18 FDG PET/CT for left ventricular dyssynchrony assessment: a comparison with gated Tc-99m sestamibi SPECT

Purpose

To investigate the value of gated F-18 FDG PET/CT on left ventricular (LV) dyssynchrony assessment in comparison with gated Tc-99m sestamibi SPECT in patients with coronary artery disease (CAD).

Methods

The data of 100 consecutive CAD patients who underwent both gated myocardial Tc-99m sestamibi SPECT and F-18 FDG PET/CT imaging were analyzed. Phase standard deviation (SD) and histogram bandwidth (BW) were derived from phase analysis using Cedars software package. The correlation and agreement of SD and BW between Tc-99m sestamibi SPECT and F-18 FDG PET/CT were examined. Myocardial viability and the site of latest activation assessed by the two imaging methods were compared as well.

Results

A moderate correlation for SD (r = 0.58, p < 0.0001) and BW (r = 0.60, p < 0.0001) was found between gated SPECT and gated F-18 FDG PET/CT. Bland–Altman analysis revealed an overestimation of SD and BW (6.4° ± 14.3° and 22.0° ± 46.8°) by gated F-18 FDG PET/CT. Multivariate logistic regression analysis identified that significant LV remodeling on SPECT imaging, LV functional parameters and F-18 FDG uptake ratio of myocardium to blood pool (SUV_M/B) were associated with the overestimation. Myocardial SPECT and F-18 FDG PET/CT had a 67.1 % identity in determining the latest activation site and 5.2 % more viable myocardium was detected by F-18 FDG PET/CT than SPECT.

Conclusion

Gated F-18 FDG PET/CT moderately correlated with gated Tc-99m sestamibi SPECT in assessing LV dyssynchrony. Gated F-18 FDG PET/CT phase analysis should be cautiously applied in CAD patients with significant LV remodeling on SPECT imaging, severe LV functional impairment or poor myocardial F-18 FDG uptake.     

A comparison of the image quality of full-time myocardial perfusion SPECT vs wide beam reconstruction half-time and half-dose SPECT

Objectives

Wide Beam Reconstruction (WBR) (UltraSPECT, Ltd) uses resolution recovery and noise modeling to cope with decreased SPECT count statistics. Because WBR processing reconstructs half the usual SPECT count statistics, we postulate that image quality equivalent to a full-time acquisition can be achieved in either half the time or with half the radiopharmaceutical activity.

Methods

In 156 consecutive patients (pts) rest and 8-frame gated post-stress myocardial perfusion SPECT was performed following 333-444 and 1184-1480 MBq (9-12 and 32-40 mCi) Tc-99m sestamibi injections, respectively, with full-time (rest = 14 min; stress = 12.3 min) acquisitions processed with OSEM and also separate “half-time” acquisitions processed with WBR. A subsequent group of 160 consecutive pts matched in gender, weight, and chest circumference received “half-dose” rest and stress injections 214.6 ± 22.2 and 647.5 ± 92.5 MBq (5.8 ± 0.6 and 17.5 ± 2.5 mCi) with full-time SPECT acquisitions. Image quality (1 = poor to 5 = excellent) was judged by myocardial count density and uniformity, endocardial edge definition, perfusion defect delineation, right ventricular visualization, and background noise.

Results

Mean image quality for rest, stress, and post-stress gated images were 3.6 ± 0.7, 3.8 ± 0.7, and 3.9 ± 1.0, respectively, for “full-time OSEM; 3.7 ± 0.8, 4.0 ± 0.7, and 4.8 ± 0.4 for “half-time” WBR; and 4.3 ± 0.8, 4.6 ± 0.6, and 4.7 ± 0.6 for “half-dose” WBR. “Half-time” and “half-dose” WBR image quality were both superior to standard full-time OSEM (P’s < .001). There was no significant difference between the summed stress and rest scores for “full-time” OSEM vs “half-time” WBR in 82 patients with perfusion defects.

Conclusions

Both “half-time” and “half-dose” WBR provide myocardial perfusion SPECT quality superior to full-time OSEM, with an associated decrease in scan acquisition time and patient radiation exposure, respectively.     

Angiographic correlation of myocardial perfusion imaging with half the radiation dose using ordered-subset expectation maximization with resolution recovery software

Background

We previously described the feasibility of performing myocardial perfusion imaging (MPI) with half the technetium (Tc-99m) activity using ordered-subset expectation maximization with resolution recovery (OSEM-RR) processing. This study sought to assess the accuracy of this technique by correlating the findings with coronary angiography.

Methods

Of 290 patients who underwent MPI-gated SPECT using a half dose of Tc-99m sestamibi and OSEM-RR software in 2010-2012 at a tertiary medical center, 62 were referred for invasive coronary angiography within 90 days and formed the study group. Ischemia was defined as a summed difference score (SDS) of >3 on the MPI scan. Luminal stenosis of ≥70% on invasive coronary angiography served as the reference.

Results

Mean Tc-99m activity per study was 23.9 ± 11.5 mCi and mean effective radiation dose was 7.2 ± 3.4 mSv. MPI revealed no abnormalities in 10 patients (16.2%), myocardial infarction only in 8 patients (12.9%), and ischemia in 44 patients (71.1%). Overall sensitivity, specificity, and positive and negative predictive values for MPI compared to invasive angiography were 89.1%, 75.0%, 91.1%, and 70.5%, respectively.

Conclusions

MPI SPECT performed with a half dose of Tc-99m and OSEM-RR image processing correlates well with invasive angiography. (J Nucl Cardiol 2013)     

Diagnostic performance of low-dose rest/stress Tc-99m tetrofosmin myocardial perfusion SPECT using the 530c CZT camera: Quantitative vs visual analysis

Background

We set out to develop normal databases and prospectively validate abnormality criteria for a low-dose Tc-99m tetrofosmin myocardial perfusion SPECT protocol using the 530c CZT camera.

Methods

All patients received 6 mCi rest/20 mCi stress doses of Tc-99m tetrofosmin. Rest and stress images were obtained over 7-9 and 5-7 minutes according to the chest size. Low-dose CT of the chest was obtained on a standalone CT scanner. Forty patients with very low likelihood (LLK) of coronary artery disease (CAD) were used to define the normal count distributions. The abnormality criteria were prospectively validated in 55 patients who had coronary angiography and in 40 patients with LLK of CAD.

Results

The results for quantitative non-attenuation-corrected (AC) and AC analysis and visual analysis were as follows: sensitivity of 79%, 85%, and 92% (P = NS) and specificity of 44%, 75%, and 56% (P = NS), respectively. The normalcy rates for quantitative non-AC and AC analyses and visual analysis were 95%, 98%, and 98% (P = NS).

Conclusions

We have developed non-AC and AC normal databases for low-dose rest/stress Tc-99m tetrofosmin myocardial perfusion SPECT protocol using the 530c CZT camera. The per-patient diagnostic performance of quantitative analyses is not significantly different from visual analysis by an experienced reader.     

I-123 mIBG and Tc-99m myocardial SPECT imaging to predict inducibility of ventricular arrhythmia on electrophysiology testing: A retrospective analysis

Objectives

The purpose of this study is to assess mIBG uptake in scar border zone and its relation with ventricular arrhythmia (VA) inducibility on electrophysiology (EP) testing using I-123 mIBG SPECT and resting Tc-99m SPECT myocardial perfusion imaging (MPI).

Methods

Forty-seven patients from a previous clinical trial were retrospectively analyzed. These patients underwent I-123 mIBG and resting Tc-99m tetrofosmin SPECT, and EP testing. Twenty-eight patients were positive (EP+) and 19 patients were negative (EP?) for inducibility of sustained (>30 seconds) VA on EP testing. MPI scar extent, border zone extent, and mIBG uptake in border zone were used to predict VA inducibility on EP testing, respectively.

Results

There was no significant difference in scar extent between the EP+ and EP? groups. The EP+ group had significantly larger border zone and lower mIBG uptake ratio in the border zone than the EP? group. Receiver operating characteristic (ROC) curve analysis showed that the prediction accuracy for border zone extent (area under ROC = 0.75) was better than scar extent (area under ROC = 0.66). The prediction accuracy was further improved (area under ROC = 0.78), when assessing mIBG uptake in the border zone.

Conclusion

A new tool has been developed to measure scar and border zone and to assess mIBG uptake in scar and border zone from combined I-123 MIBG SPECT and resting Tc-99m SPECT MPI. The mIBG uptake in the border zone predicted VA inducibility on EP testing with a promising accuracy.     

Incremental diagnostic benefit of resolution recovery software in patients with equivocal myocardial perfusion single-photon emission computed tomography (SPECT)

Background

Though myocardial perfusion imaging (MPI) with single-photon emission computed tomography (SPECT) is an established diagnostic method, equivocal studies are commonly encountered. New software has been introduced that incorporates resolution recovery (RR) and noise regulation into the reconstruction algorithm and has been used to facilitate “half-dose” and “half-time” studies. Its utility with “full-time, full-dose” acquisition has not been well studied.

Objective

We sought to understand the potential benefit of incorporating RR software in equivocal SPECT studies.

Methods

Patients with full-time, full-dose SPECT MPI were reviewed and those with equivocal results, who subsequently underwent cardiac Rb-82 positron emission tomography (PET) scan were identified. Image reconstruction was performed with iterative reconstruction (IR), attenuation correction (IR + AC), and RR software (IR + AC + RR). Images were anonymized and read blindly by consensus of two experienced readers. All images were qualitatively assessed and semi-quantitatively graded using summed stress and summed rest scores.

Results

45 patients were included (28 males, age = 59.6 ± 9.9 years) and the diagnostic accuracy of each of the reconstruction algorithms (IR, IR + AC, IR + AC + RR) was compared to Rb-82 PET. Agreement of clinical diagnosis of each SPECT reconstruction with Rb-PET showed incremental improvement. The agreement with PET for IR + AC + RR (κ = 0.66, CI 0.454-0.875) is significantly better than for IR (κ = 0.22, CI 0.0-0.450, P = .005) and for IR + AC (κ = 0.32, CI 0.077-0.563, P = .03). Also, IR + AC + RR improved the clinical diagnosis in 14 cases and with overall improvement of reclassification proportion of 23.5% compared to IR (P = .01). Using PET as a reference standard, ROC curves were created for IR + AC + RR, IR + AC, and IR which showed incremental value of the area under the curve of IR + AC + RR (AUC: 0.87; CI 0.76-0.98) over IR + AC (AUC: 0.75; CI 0.61-0.89, P = .078), and over IR (AUC 0.68; CI 0.52-0.84, P = .025).

Conclusion

The addition of RR may help in the diagnosis of patients with equivocal SPECT MPI without the need for additional testing. Further prospective studies are needed to define the role of this new software.     

Effect of dialysis on cerebral blood flow in depressive end-stage renal disease patients

Objective

The aim of this study was to investigate regional cerebral blood flow (rCBF) changes of end-stage renal disease (ESRD) patients with depressive symptoms during dialysis.

Methods

Fourteen patients with ESRD underwent Tc-99m ethylcysteinate dimer (Tc-99m ECD) brain single photon emission computed tomography (SPECT) and were evaluated the severity of depressive mood at pre-dialytic period and at least 6 months after dialysis initiation. rCBF was analyzed using statistical parametric mapping (SPM) in brain SPECT image. The responder was defined as a decrease of ≥25% in Hamilton Depression Rating Scale (HDRS) score from baseline HDRS score.

Results

Pre-dialysis brain SPECT did not show any rCBF differences between responders and non-responders. The follow-up brain SPECT revealed a significant higher perfusion in left middle temporal gyrus of responder group when compared with non-responder (hemisphere coordinate X, Y, Z; ?58, ?2, ?16, peak Z = 3.36, p = 0.046). In responder, a significant increase in rCBF was found in right parahippocampal gyrus (hemisphere coordinate X, Y, Z; 30, ?40, ?14, peak Z = 3.51, p = 0.043). In non-responder, there were significant decreases in rCBF in left superior frontal gyrus (hemisphere coordinate X, Y, Z; ?22, 30, 42, peak Z = 3.86, p = 0.032) and right orbitofrontal cortex (hemisphere coordinate X, Y, Z; 10, 58, ?6, peak Z = 3.81, p = 0.046).

Conclusion

The present findings showed the characteristic patterns of rCBF changes in depressive ESRD patients having maintenance dialysis. Further investigations in brain blood flow and glucose metabolism are needed to elucidate the effect of dialysis itself and the difference of according to dialysis modality in patients having depression and ESRD.     

Synthesis and evaluation of Tc-99m DTPA–glutathione as a non-invasive tumor imaging agent in a mouse colon cancer model

Purpose

Glutathione (GSH) plays a critical role in detoxification reactions by reducing the levels of reactive oxygen species in cancer cells. This study aimed to develop technetium (Tc)-99m diethylenetriaminepentaacetic acid (DTPA)–GSH as a tumor imaging agent, and to evaluate the diagnostic performance of Tc-99m DTPA–GSH in terms of its ability to differentiate tumors from inflammatory lesions.

Methods

DTPA–GSH was synthesized by reaction of GSH with DTPA anhydride under anhydrous conditions in a nitrogen atmosphere. DTPA–GSH was then reacted with Tc-99m sodium pertechnetate in a tin (II) chloride (SnCl₂) solution. Gamma camera imaging was performed after intravenous injection of Tc-99m DTPA–GSH into a mouse CT-26 colon cancer model, or a mouse model of inflammation induced by the intramuscular injection of Freund’s complete adjuvant.

Results

DTPA–GSH was successfully prepared via a straightforward synthetic procedure and radiolabeled with Tc-99m at a high labeling efficiency (>95 %). Tc-99m DTPA–GSH was strongly internalized by tumors in colon cancer model mice, with the tumor-to-normal muscle ratio of the complex reaching 4.3 ± 0.9 at 4 h. By contrast, Tc-99m DTPA–GSH showed relatively weak uptake in inflammatory lesions (target-to-non-target ratio = 2.0 ± 0.3 at 4 h). A competition study showed that the uptake of Tc-99m DTPA–GSH into tumors was blocked by co-injection with high concentrations of free GSH.

Conclusions

The results of this work indicate that Tc-99m DTPA–GSH is a good candidate for development as a non-invasive tumor imaging agent. Furthermore, Tc-99m DTPA–GSH effectively distinguished between cancerous tissue and inflammatory lesions.     

High-efficiency SPECT MPI: Comparison of automated quantification, visual interpretation, and coronary angiography

Background

Recently introduced high-efficiency (HE) SPECT cameras with solid-state CZT detectors have been shown to decrease imaging time and reduce radiation exposure to patients. An automated, computer-derived quantification of HE MPI has been shown to correlate well with coronary angiography on one HE SPECT camera system (D-SPECT), but has not been compared to visual interpretation on any of the HE SPECT platforms.

Methods

Patients undergoing a clinically indicated Tc-99m sestamibi HE SPECT (GE Discovery 530c with supine and prone imaging) study over a 1-year period followed by a coronary angiogram within 2 months were included. Only patients with a history of CABG surgery were excluded. Both MPI studies and coronary angiograms were reinterpreted by blinded readers. One hundred and twenty two very low (risk of CAD < 5%) or low (risk of CAD < 10%) likelihood subjects with normal myocardial perfusion were used to create normal reference limits. Computer-derived quantification of the total perfusion deficit at stress and rest was obtained with QPS software. The visual and automated MPI quantification were compared to coronary angiography (≥70% luminal stenosis) by receiver operating curve (ROC) analysis.

Results

Of the 3,111 patients who underwent HE SPECT over a 1-year period, 160 patients qualified for the correlation study (66% male, 52% with a history of CAD). The ROC area under the curve (AUC) was similar for both the automated and the visual interpretations using both supine only and combined supine and prone images (0.69-0.74). Using thresholds determined from sensitivity and specificity curves, the automated reads showed higher specificity (59%-67% vs 27%-60%) and lower sensitivity (71%-72% vs 79%-93%) than the visual reads. By including prone images sensitivity decreased slightly but specificity increased for both. By excluding patients with known CAD and cardiomyopathies, AUC and specificity increased for both techniques (0.72-0.82). The use of a difference score to evaluate ischemic burden resulted in lower sensitivities but higher specificities for both automated and visual quantification. There was good agreement between the visual interpretation and automated quantification in the entire cohort of 160 unselected consecutive patients (r = 0.70-0.81, P < .0001).

Conclusions

Automated and visual quantification of high-efficiency SPECT MPI with the GE Discovery camera provides similar overall diagnostic accuracy when compared to coronary angiography. There was good correlation between the two methods of assessment. Combined supine and prone stress imaging provided the best diagnostic accuracy.     

The prognosis of a normal Tl-201 stress-only SPECT MPI study

Background

Stress-only Tc-99m SPECT myocardial perfusion imaging (MPI) decreases test time and patient radiation exposure with a proven benign prognosis of a normal study. The imaging sequence of Tl-201 MPI always starts with the stress portion; therefore, no pre-test decisions are needed regarding the imaging sequence. The recent intermittent Tc-99m shortage afforded the unique opportunity to study an unselected group of patients undergoing Tl-201 imaging.

Methods

We retrospectively reviewed all the patients who had SPECT MPI with Tc-99m or Tl-201 over a 1-year period. When Tc-99m was not available, patients received Tl-201. All stress Tl-201 images were routinely processed, and if normal, rest imaging was not done. When Tc-99m was used, patients with lower pre-test probability were selected for a stress-first protocol. We compared the all-cause mortality of patients with normal Tl-201 studies to those with normal stress-only and rest-stress Tc-99m studies using the Social Security Death Index. Unadjusted and risk-adjusted survival analysis was performed. Specific causes of death (cardiac or non-cardiac) were determined by medical record review and contact with treating physicians.

Results

A total of 3,658 patients underwent stress MPI during this time period. Of the 1,215 patients who had Tl-201 MPI, 716 (67%) had a normal stress-only study. Out of 2,443 patients who underwent Tc-99m MPI, 70% had normal perfusion with 1,098 normal stress-only studies and 493 normal rest-stress studies. The average follow-up was 23.3?±?5.3?months. Unadjusted all-cause mortality at the end of follow-up was 7.1% in the Tl-201 stress-only group, 6.3% for Tc-99m stress-only patients, and 4.3% in the Tc-99m rest-stress cohort. After controlling for confounding variables, survival was similar in the three groups (HR 1.07, 95% CI 0.62-1.82, P?=?.82 for normal Tl-201 stress-only compared to normal Tc-99m rest-stress). The risk-adjusted 1-year survival was between 98.5 and 98.8% in the three groups.

Conclusions

Normal stress-only Tl-201 SPECT MPI study has a similarly benign prognosis when compared to Tc-99m rest-stress and Tc-99m stress-only normal SPECT MPI studies. The stress-first design allowed for early triage of over 60% of patients and marked improvement in laboratory efficiency due to shortened test time.     

Evaluation of left ventricular ejection fraction from radial long-axis tomography: A new reconstruction algorithm for ECG-gated technetium-99m sestamibi SPECT

Methods

ECG-gated Tc-99m MIBI SPECT was performed with a temporal resolution of 10 frames per R-R interval. LVEF was calculated on the basis of left ventricular volume estimates at end diastole (ED) and end systole (ES) with using an ellipsoid body model. To validate this method, LVEF’s derived from ECG-gated Tc-99m MIBI SPECT were compared with those from LVG in 11 patients with coronary artery disease.

Results

There was a close linear correlation between LVEF values calculated from Tc-99m MIBI SPECT and those from LVG (r = 0.89, p < 0.001), although the gated SPECT underestimated LVEF compared to LVG. The technique showed excellent reproducibility (intra-observer variability, r = 0.96, p < 0.001; inter-observer variability, r = 0.71, p < 0.005).

Conclusion

The radial long-axis tomography technique gives a good estimate of LVEF, in agreement with estimates based on LVG. ECG-gated Tc-99m MIBI SPECT can, therefore, be applicable to assess myocardial perfusion and ventricular function at the same time.     

Discordance in the anatomical locations between morphological and perfusion changes occurring with the progression of Alzheimer’s disease

Objective

The aim of this study was to clarify the difference between the morphological and perfusion changes occurring with the progression of Alzheimer’s disease (AD).

Methods

The study focused on 37 patients who were clinically diagnosed with AD and were examined by both MRI and perfusion SPECT twice during a 1- to 2-year clinical observation period. Twenty-four of the 37 patients showed a progression of cognitive deterioration during the 1.2(±0.4)-year period of clinical observation (rapidly progressing group: initial mean MMSE score = 23.3; second mean MMSE score = 20.2), while 13 patients showed no apparent progression of cognitive deterioration (slowly progressing group: initial mean MMSE score = 21.2; second mean MMSE score = 22.2). The morphological changes were evaluated using a voxel-based morphometric technique with segmented MRI images. Cerebral perfusion was measured by Tc-99m ECD SPECT. Data analysis was performed by SPM on a MATLAB work space (2007.a).

Results

There was no significant difference in either the perfusion or gray matter density between the rapidly progressing and slowly progressing groups at the initial examination. The rapidly progressing group showed an interval decrease of perfusion in the bilateral parieto-occipital cortex and a decrease of gray matter density in the bilateral temporal and cingulate cortex. The slowly progressing group did not show a significant interval change in either the cerebral perfusion or gray matter density.

Conclusions

These results suggest that rapid symptomatic progression in AD patients accompanies rapid progression of both morphological and perfusion changes, although the regions of the changes differ between them.     

Whole-body SPECT/CT for bone scintigraphy: diagnostic value and effect on patient management in oncological patients

Purpose

This study was designed to assess the additional value of SPECT/CT of the trunk used in conjunction with conventional nuclear imaging and its effects on patient management in a large patient series.

Methods

In 353 patients, whole-body scintigraphy (WBS), SPECT, and SPECT/CT were prospectively performed for staging and restaging. SPECT/CT of the trunk was performed in all patients. In the 308 evaluable patients (211 with breast cancer, 97 with prostate cancer), clinical follow-up was used as the gold standard. Bone metastases were confirmed in 72 patients and excluded in 236. Multistep analyses per lesion and per patient were performed. Clinical relevance was expressed in terms of downstaging and upstaging rates on a per-patient basis.

Results

In the total patient group, sensitivities, specificities, and negative and positive predictive values on a per-patient basis were 93 %, 78 %, 95 % and 59 % for WBS, 94 %, 71 %, 97 % and 53 % for SPECT, and 97 %, 94 %, 97 % and 88 % for SPECT/CT, respectively. In all subgroups, specificity and positive predictive value were significantly (p?<?0.01) better with SPECT/CT. Downstaging of metastatic disease in the total, breast cancer and prostate cancer groups using SPECT/CT was possible in 32.1 %, 33.8 % and 29.5 % of patients, respectively. Upstaging in previously negative patients by additional SPECT/CT was observed in three breast cancer patients (2.1 %). Further diagnostic imaging procedures for unclear scintigraphic findings were necessary in only 2.5 % of patients. SPECT/CT improved diagnostic accuracy for defining the extent of multifocal metastatic disease in 34.6 % of these patients.

Conclusions

SPECT/CT significantly improved the specificity and positive predictive value of bone scintigraphy in cancer patients. In breast cancer patients, we found a slight increase in sensitivity. SPECT/CT had a significant effect on clinical management because of correct downstaging and upstaging, better definition of the extent of metastases, and a reduction in further diagnostic procedures.     

Tc-99m depreotide SPECT/CT for lymph node staging of non-small-cell lung cancer

Objective

To investigate the potential role of Tc-99m depreotide (Tc-DEPR) in the preoperative lymph node (N) staging of non-small-cell lung cancer (NSCLC).

Methods

Sixty-one patients with NSCLC at the potentially operable stage were enrolled and underwent scintigraphy before surgery (n = 56) or mediastinoscopy (n = 5). Imaging was performed with a hybrid single photon emission computed tomography/computed tomography (SPECT/CT) system. Depreotide uptake in N stations was evaluated visually and semi-quantitatively and compared to histology. Quantification was carried out in attenuation-corrected SPECT slices. Different sites of normal uptake were used as a reference for comparison with lesional uptake. Receiver operating characteristic analysis was employed to identify the most preferable reference area and the cut-off best discriminating disease-free from disease-involved lymph nodes.

Results

With reference to 53 Ν1 hilar and 147 Ν2/Ν3 sampled stations, sensitivity of scintigraphy by visual interpretation was 100 and 94 %, specificity 43 and 59 % and accuracy 55 and 67 %, respectively. No patient was down-staged, but 52 % were incorrectly up-staged and 44 % were misclassified as inoperable. Compared to scintigraphy, preoperative contrast-enhanced diagnostic CT demonstrated lower sensitivity (36 % for hilar and 73 % for N2/N3 stations), higher specificity (79 and 75 %) and similar accuracy (70 and 75 %). Regarding the ultimate N-stage and the prediction of surgical disease, diagnostic CT was wrong in 51 and 34 % of cases. Dichotomy of quantitative scintigraphic data by the use of certain N-to-spine ratio cut-offs resulted in a significant increase of specificity (76 % for hilar and 89 % for N2/N3 stations), while sensitivity remained high (82 % in both circumstances) and accuracy for Ν2/Ν3 stations was substantially improved (88 %). By this quantitative approach, misclassifications as to the N-stage and patient operability (25 and 16 %) were considerably less than that of visual Tc-DEPR and diagnostic CT interpretations.

Conclusion

Tc-99m depreotide SPECT/CT seems to have a role in the N-staging of NSCLC, mainly because of its high sensitivity and negative predictive value. Quantification of uptake can improve specificity, at a low cost of sensitivity. If F-18 fluoro-deoxyglucose positron emission tomography is not available, this method may be used as a surrogate to conventional staging modalities.     

Cardiac hybrid SPECT/CTA imaging to detect “functionally relevant coronary artery lesion”: a potential gatekeeper for coronary revascularization?

Objective

Combination of both morphological and functional information has gained more and more appreciation with the concept of “functionally relevant coronary artery lesion (FRCAL)” and “functional revascularization”. This has paved the way for non-invasive single-photon emission computed tomography (SPECT)/computed tomography angiography (CTA) hybrid imaging. We aimed at assessing the value of cardiac hybrid imaging on the detection of FRCAL and its potential as a gatekeeper for invasive examination and treatment.

Methods

In Two hundred and thirty-eight patients with known or suspected coronary artery disease (CAD) underwent CTA and myocardial perfusion imaging (MPI) using SPECT on a dual system scanner in one session before treatment. 78 patients underwent invasive coronary angiography (CAG) within 1 month. Detection of FRCAL by the combination of SPECT/CTA was compared with SPECT/CAG, which served as a standard of reference. According to the both combination results, treatment decision (revascularization or medical treatment) was chosen in the catheterization laboratory.

Results

Sensitivity, specificity, accuracy, positive and negative prediction rate by SPECT/CTA vs. SPECT/CAG for the detection of flow-limiting coronary stenosis on patient- and vessel-based analysis were 94.33, 72.00, 87.18, 87.71, 85.71 % and 88.71, 92.44, 91.45, 80.89, 95.78 %, respectively. No revascularization procedures were performed in patients without flow-limiting stenosis. However, more than one-third (25/67, 37 %) of revascularized vessels were not associated with ischemia on MPI.

Conclusions

The cardiac SPECT/CTA hybrid imaging can accurately detect FRCAL and thereby it may be used as a gatekeeper for CAG and revascularization procedures.     

Feasibility of myocardial perfusion imaging with half the radiation dose in obese patients using ordered-subset expectation maximization with resolution recovery software

Background

We previously described the feasibility of myocardial perfusion imaging (MPI) with nearly half the radiation dose using ordered-subset expectation maximization with resolution recovery (OSEM-RR) processing. This study sought to determine if the findings can be expanded to obese patients.

Methods

Fifty obese patients (>100 kg) referred for MPI underwent stress-rest or rest-stress studies with a half dose of Tc-99m sestamibi in a 1-day protocol using OSEM-RR processing. Image quality and clinical results were compared with matched patients (by age, sex, weight, presence/probability of coronary artery disease) evaluated with standard “full-dose” Tc-99m sestamibi, mostly in a 2-day protocol. Dose activities were adjusted individually by weight.

Results

Mean Tc-99m activity was 33.4 ± 13.9 mCi in the half-dose group and 60 ± 10 mCi in the full-dose group (P < .0001). Respective mean effective doses per study were 10 ± 4 and 18 ± 3 mSv (P < .0001). Overall image quality was good-to-excellent in 94% of the half-dose group and 80% of the full-dose group (P < .045). There was no between-group difference in rate or size of ischemia or infarction, except for stress left ventricular ejection fraction.

Conclusions

MPI with half the radiation dose is feasible in obese patients. Image quality is better than for full-dose MPI, and the procedure can be performed in 1 day.     

Comparison of nitrate augmented Tc-99m tetrofosmin gated SPECT imaging with FDG PET imaging for the assessment of myocardial viability in patients with severe left ventricular dysfunction

Background

Of various nuclear medicine techniques, F-18/flourodeoxyglucose (FDG) positron emission tomography (PET) is considered as the best modality for the assessment of viable myocardium (VM). In this study, we compared the diagnostic accuracy of nitrate augmented Tc-99m tetrofosmin gated G-single-photon emission computed tomography (SPECT) with FDG PET.

Methods

54 consecutive cases of angiographically proven CAD with severe LV dysfunction were enrolled in the study. The patients underwent Tc-99m tetrofosmin G-SPECT and FDG PET as per the standard protocols and were compared.

Results

SPECT data analysis indicated functional abnormalities in 661/918 myocardial segments. F-18 FDG PET revealed VM in 496/661 segments. The diagnostic accuracy of baseline NAC, postnitrate NAC, baseline AC, and postnitrate AC Tc-99m tetrofosmin SPECT was 84%, 87%, 90%, and 94%, respectively. ?? values for NAC baseline, NAC postnitrate, AC baseline, and AC postnitrate Tc-99m tetrofosmin G-SPECT were 0.65, 0.70, 0.77, and 0.85, respectively. Attenuation correction revealed viability additionally in 46 segments which were non-viable on NAC postnitrate study (P?<?.001). Nitrate augmentation showed viability additionally in 25 segments which were non-viable on AC baseline scan (P?=?.004). On patient-based analysis FDG PET changes the management only in 13% (7/54) of patients.

Conclusions

Nitrate augmented AC Tc-99m tetrofosmin G-SPECT shows excellent (???=?.85) agreement with FDG PET. FDG PET changes management only in 13% of the patients. Tc-99m tetrofosmin G-SPECT being more widely available and cheaper imaging modality can be reliably used to detect VM where FDG PET is not available.     

4D-SPECT/CT in orthopaedics: a new method of combined quantitative volumetric 3D analysis of SPECT/CT tracer uptake and component position measurements in patients after total knee arthroplasty

Objective

The purpose was to evaluate the intra- and inter-observer reliability of combined quantitative 3D-volumetric single-photon emission computed tomography (SPECT)/CT analysis including size, intensity and localisation of tracer uptake regions and total knee arthroplasty (TKA) position.

Materials and methods

Tc-99m-HDP-SPECT/CT of 100 knees after TKA were prospectively analysed. The anatomical areas represented by a previously validated localisation scheme were 3D-volumetrically analysed. The maximum intensity was recorded for each anatomical area. Ratios between the respective value and the mid-shaft of the femur as the reference were calculated. Femoral and tibial TKA position (varus–valgus, flexion–extension, internal rotation– external rotation) were determined on 3D-CT. Two consultant radiologists/nuclear medicine physicians interpreted the SPECT/CTs twice with a 2-week interval. The inter- and intra-observer reliability was determined (ICCs). Kappa values were calculated for the area with the highest tracer uptake between the observers.

Results

The measurements of tracer uptake intensity showed excellent inter- and intra-observer reliabilities for all regions (tibia, femur and patella). Only the tibial shaft area showed ICCs <0.89. The kappa values were almost perfect (0.856, p?<?0.001; 95 % CI 0.778, 0.922). For measurements of the TKA position, there was strong agreement within and between the readings of the two observers; the ICCs for the orientation of TKA components for inter- and intra-observer reliability were nearly perfect (ICCs >0.84).

Conclusion

This combined 3D-volumetric standardised method of analysing the location, size and the intensity of SPECT/CT tracer uptake regions (“hotspots”) and the determination of the TKA position was highly reliable and represents a novel promising approach to biomechanics.     

Utility of 99mTc-MDP hybrid SPECT-CT for diagnosis of skull base osteomyelitis: comparison with planar bone scintigraphy, SPECT, and CT

Purpose

To evaluate single photon emission tomography–computed tomography (SPECT-CT) for diagnosis of skull base osteomyelitis (SBO) and to compare this technique with planar bone scintigraphy (BS), SPECT, and CT.

Methods

Data from 13 patients with known/suspected SBO were retrospectively analysed. Planar BS and SPECT images were evaluated by an experienced nuclear medicine physician, CT by and experienced radiologist, and SPECT-CT by the nuclear medicine physician and radiologist in consensus. On the basis of diagnostic confidence a score of 1–5 was given, with 1 being definitely osteomyelitis, 2 being probably osteomyelitis, 3 being equivocal, 4 being probably normal, and 5 being definitely normal. ROC analysis areas under the curves (AUC) were calculated. For diagnostic values a score of ≤2 was taken as positive. Clinical/imaging follow-up/microbiology was taken as reference standard.

Results

AUC was largest for SPECT-CT (0.977) followed by SPECT (0.909), CT (0.886), and planar BS (0.614). However, no significant difference was found between the techniques except for borderline significance between planar BS with SPECT-CT (P = 0.071) and CT (P = 0.072). Accuracy was 46 % for planar BS, 85 % for SPECT, 77 % for CT and 92 % for SPECT-CT.

Conclusion

SPECT-CT seems to be useful, but not superior to planar BS, SPECT, or CT, for diagnosis of SBO.     

Three-dimensional brain phantom containing bone and grey matter structures with a realistic head contour

Introduction

A physical 3-dimensional phantom that simulates PET/SPECT images of static regional cerebral blood flow in grey matter with a realistic head contour has been developed. This study examined the feasibility of using this phantom for evaluating PET/SPECT images.

Methods

The phantom was constructed using a transparent, hydrophobic photo-curable polymer with a laser-modelling technique. The phantom was designed to contain the grey matter, the skull, and the trachea spaces filled with a radioactive solution, a bone-equivalent solution of K₂HPO₄, and air, respectively. The grey matter and bone compartments were designed to establish the connectivity. A series of experiments was performed to confirm the accuracy and reproducibility of the phantom using X-ray CT, SPECT, and PET.

Results

The total weight was 1997 ± 2 g excluding the inner liquid, and volumes were 563 ± 1 and 306 ± 2 mL, corresponding to the grey matter and bone compartments, respectively. The apparent attenuation coefficient averaged over the whole brain was 0.168 ± 0.006 cm^?1 for Tc-99 m, which was consistent with the previously reported value for humans (0.168 ± 0.010 cm^?1). Air bubbles were well removed from both grey-matter and bone compartments, as confirmed by X-ray CT. The phantom was well adapted to experiments using PET and SPECT devices.

Conclusion

The 3-dimensional brain phantom constructed in this study may be of use for evaluating the adequacy of SPECT/PET reconstruction software programs.