Prognostic value of left ventricular mechanical dyssynchrony indices derived from gated myocardial perfusion SPECT in coronary artery disease: a systematic review and meta-analysis

PURPOSE

Left ventricular mechanical dyssynchrony (LVMD) is an important prognostic factor in coronary artery disease. A growing body of evidence indicates that LVMD parameters derived from phase analysis of gated myocardial SPECT may allow risk stratification for future cardiac events. We performed a systematic review and meta-analysis on the prognostic value of LVMD on gated SPECT in patients with coronary artery disease.

METHODS

PubMed, Embase, and the Cochrane library were searched until August 25, 2022, for studies reporting the prognostic value of LVMD on gated SPECT for outcomes of all-cause death, cardiac death, or major adverse cardiovascular event (MACE) in patients with coronary artery disease. Hazard ratios (HRs) and their 95% confidence intervals (CIs) were meta-analytically pooled using a random-effects model.

RESULTS

Nine studies (26,750 patients) were included in a qualitative synthesis. Among the SPECT LVMD parameters used in various studies, high phase standard deviation, phase bandwidth, and phase entropy were widely evaluated and reported to be associated with high rates of all-cause death, cardiac death, or MACE. For five studies (23,973 patients) in the quantitative synthesis, the pooled HR of LVMD for predicting MACE was 2.81 (95% CI 2.03-3.88). Studies using combined phase parameters to define LVMD showed higher HRs than a study using phase entropy (p = 0.0180).

CONCLUSION

LVMD from gated myocardial SPECT is a significant prognostic factor for coronary artery disease. Phase analysis of gated SPECT may be useful for accurate risk stratification and could be applied for clinical decision-making in such patients.

Discordant Uptake of Leg Thrombi Versus Pulmonary Emboli on 68 Ga-FAPI-46 PET/CT

ABSTRACT

Fibroblast activation protein inhibitor (FAPI) PET is gaining clinical relevance for visualizing activated fibroblasts in various diseases. Here, we report discordant FAPI uptake between venous thrombi of the lower extremities and pulmonary emboli. An 86-year-old man complained of left leg swelling and acute dyspnea; he was diagnosed with deep vein thrombosis involving the left femoral vein and acute pulmonary thromboembolism. Positive FAPI uptake was observed only in the thrombi of the left femoral vein, but not in the pulmonary emboli. Such discrepancies may indicate different thrombus constituents and chronologies even in the same patient.

Tc-99m DMSA SPECT for Follow-Up of Non-Operative Treatments in Renal Injuries: A Prospective Single-Center Study

OBJECTIVE

The assessment of cortical integrity following renal injuries with planar Tc-99m dimercaptosuccinic acid (DMSA) scintigraphy depends on measuring relatively decreased cortical uptake (i.e., split renal function [SRF]). We analyzed the additive values of the volumetric and quantitative analyses of the residual cortical integrity using single-photon emission computed tomography (SPECT) compared to the planar scintigraphy.

MATERIALS AND METHODS

This prospective study included 47 patients (male:female, 32:15; age, 47 ± 22 years) who had non-operatively managed renal injuries and underwent DMSA planar and SPECT imaging 3-6 months after the index injury. In addition to planar SRF, SPECT SRF, cortical volume, and absolute cortical uptake were measured for the injured kidney and both kidneys together. The correlations of planar SRF with SPECT SRF and those of SRF with volumetric/quantitative parameters obtained with SPECT were analyzed. The association of SPECT parameters with renal function, grades of renal injuries, and the risk of renal failure was also analyzed.

RESULTS

SPECT SRF was significantly lower than planar SRF, with particularly higher biases in severe renal injuries. Planar and SPECT SRF (dichotomized with a cutoff of 45%) showed 19%-36% of discrepancies with volumetric and quantitative DMSA indices (when dichotomized as either high or low). Absolute cortical uptake of the injured kidney best correlated with glomerular filtration rate (GFR) at follow-up (ρ = 0.687, P < 0.001) with significant stepwise decreases by GFR strata (90 and 60 mL/min/1.73 m²). Total renal cortical uptake was significantly lower in patients with moderate-to-high risk of renal failure than those with low risk. However, SRF did not reflect GFR decrease below 60 mL/min/1.73 m² or the risk of renal failure, regardless of planar or SPECT (count- or volume-based SRF) imaging.

CONCLUSION

Quantitative measurements of renal cortical integrity assessed with DMSA SPECT can provide more clinically relevant and comprehensive information than planar imaging or SRF alone.

Case report: A fatal case of myocardial infarction due to myocardial bridge and concomitant vasospasm: the role of stress gated SPECT

Introduction

Although most cases of myocardial bridge (MB) are clinically benign, sometimes it can be one of potential threats of myocardial infarction (MI) and life-threatening arrhythmia. In the present study, we present a case of ST-segment elevation MI caused by MB and concomitant vasospasm.

Case Presentation

A 52-year-old woman was brought to our tertiary hospital due to resuscitated cardiac arrest. Because the 12-lead electrocardiogram indicated ST-segment elevation MI, coronary angiogram was promptly commenced, which showed near-total occlusion at the middle portion of left anterior descending coronary artery (LAD). After intracoronary nitroglycerin administration, this occlusion was dramatically relieved, however, systolic compression at this site remained, indicative of myocardial bridge (MB). Intravascular ultrasound also showed eccentric compression with a "half-moon" sign, which is consistent with MB. Coronary computed tomography also showed a bridged coronary segment surrounded by myocardium at the middle portion of LAD. To assess the severity and extent of myocardial damages and ischemia, myocardial single photon emission computed tomography (SPECT) was additionally conducted, showing a moderate fixed perfusion defect around the cardiac apex, suggesting MI. After receiving optimal medical therapy, the patient's clinical symptoms and signs were improved then the patient was discharged from the hospital successfully and uneventfully.

Conclusion

We demonstrated a case of MB-induced ST-segment elevation MI which was confirmed with its perfusion defects via myocardial perfusion SPECT. There have been proposed a number of diagnostic modalities to examine its anatomic and physiologic significance. Among them, myocardial perfusion SPECT can be available as one of useful modalities to evaluate the severity and extent of myocardial ischemia in patients with MB.

Acute respiratory distress syndrome and severe pneumonitis after atezolizumab plus bevacizumab for hepatocellular carcinoma treatment: A case report

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide and has a high mortality. However, the treatment options for advanced HCC are limited to tyrosine kinase inhibitors, such as sorafenib and lenvatinib. Since previous regimens have an insufficient efficacy, the combination therapy of atezolizumab and bevacizumab (Ate/Bev) has been investigated, which showed an improvement in progression-free and overall survival. However, the adverse events of this combination therapy in advanced HCC have not been established. Herein, we report a novel case of an unresectable HCC and acute respiratory distress syndrome (ARDS) after a combination therapy of Ate/Bev.

CASE SUMMARY

An 82-year-old male visited our outpatient clinic for an incidentally detected liver mass. Liver magnetic resonance imaging and enhanced chest computed tomography (CT) were performed, which showed arterial hyperenhancement with washout in delayed phase suggesting HCC, and a well-defined metastatic solid nodule, respectively. F-18 fluorodeoxyglucose positron emission tomography (PET)-CT exhibited multiple hypermetabolic lesions in the iliac bone, lumbar vertebrae, and femur. Because of the high burden of the intrahepatic tumor, transarterial radioembolization was initially performed; after 37 d, a combination therapy of Ate/Bev was administered. The patient visited the emergency department three days after Ate/Bev treatment complaining of dyspnea. He was diagnosed with severe pneumonitis based on CT. Despite administering oxygen via a high-flow nasal cannula, the P/F ratio was only 74; therefore, the patient was diagnosed with ARDS based on the overall examination results. Low tidal volume with high positive end-expiratory pressure, sedative agents combined with a neuromuscular blocker, and a systemic steroid were promptly applied to manage the ARDS. However, the patient did not recover from the hypoxia and expired 31 h after being admitted.

CONCLUSION

Clinicians should be aware of severe pneumonitis due to the immune-related adverse events of this combination therapy, and patients should be closely monitored after therapy.

Applying Pix2pix to Translate Hyperemia in Blood Pool Image into Corresponding Increased Bone Uptake in Delayed Image in Three-Phase Bone Scintigraphy

Purpose

Delayed images may not be acquired due to severe pain, drowsiness, or worsening vital signs while waiting after blood pool imaging in three-phase bone scintigraphy. If the hyperemia in the blood pool image contains information from which increased uptake on the delayed images can be inferred, the generative adversarial network (GAN) can generate the increased uptake from the hyperemia. We attempted to apply pix2pix, a type of conditional GAN, to transform hyperemia into increased bone uptake.

Methods

We enrolled 1464 patients who underwent three-phase bone scintigraphy for inflammatory arthritis, osteomyelitis, complex regional pain syndrome (CRPS), cellulitis, and recent bone injury. Blood pool images were acquired 10 min after intravenous injection of Tc-99 m hydroxymethylene diphosphonate, and delayed bone images were obtained after 3 h. The model was based on the open-source code of the pix2pix model with perceptual loss. Increased uptake in the delayed images generated by the model was evaluated using lesion-based analysis by a nuclear radiologist in areas consistent with hyperemia in the blood pool images.

Results

The model showed sensitivities of 77.8% and 87.5% for inflammatory arthritis and CRPS, respectively. In osteomyelitis and cellulitis, their sensitivities of about 44% were observed. However, in cases of recent bone injury, the sensitivity was only 6.3% in areas consistent with focal hyperemia.

Conclusion

The model based on pix2pix generated increased uptake in delayed images matching the hyperemia in the blood pool image in inflammatory arthritis and CRPS.

Association between myocardial ischemia and plaque characteristics in chronic total occlusion

BACKGROUND

Myocardial ischemia varies in chronic total occlusion (CTO) despite the occluded artery. We analyzed whether it is associated with the plaque characteristics of the occluded segment.

METHODS

We retrospectively enrolled 100 patients with CTO who underwent myocardial perfusion single-photon emission computed tomography (SPECT) and coronary computed tomography angiography (CCTA) within 2 months. CTO-related ischemia was classified as moderate to severe (summed difference score [SDS] of the CTO territory ≥ 5) or mild or none (SDS < 5) on SPECT. Using CCTA, the atherosclerotic plaques of the occluded segment were subdivided into low-density (- 100-30 HU), intermediate-density (31-350 HU), and high-density (351-1000 HU) plaques. The plaque composition was compared according to the severity of CTO-related ischemia.

RESULTS

Moderate-to-severe CTO-related ischemia (n = 23) showed significantly higher proportion of intermediate-density plaques (72.4% vs. 64.0%), intermediate/low-density (7.10 vs. 3.65) and intermediate-to-high/low-density (7.78 vs. 3.80) plaque ratios, frequent shorter occlusion (30% vs. 6%), and lower volume (26.5 mm3 vs. 58.8 mm3) and proportion (11.4% vs. 20.8%) of low-density plaques. Multivariable analysis revealed significant associations between higher proportion of intermediate-density plaques and moderate-to-severe CTO-related ischemia, independent of occlusion length.

CONCLUSION

Higher proportion of intermediate-density plaques in the occluded segment was associated with the moderate-to-severe CTO-related ischemia.

Determination of [N-13]-ammonia extraction fraction in patients with coronary artery disease by calibration to invasive coronary and fractional flow reserve

BACKGROUND

This study presents a new extraction fraction (EF) model based on physiological measures of invasive coronary flow reserve (CFR) and fractional flow reserve (FFR) in patients with suspected coronary artery disease (CAD) and normal index microcirculatory resistance (IMR). To ascertain the clinical relevance of the new EFs, flow measurements using the newly patient-determined EFs were compared to flow measurements using traditional animal-determined EFs.

METHODS

39 patients were retrospectively selected that included a total of 91 vascular territories with invasive coronary angiography physiological measures. [N-13]-ammonia dynamic rest/adenosine-stress PET imaging was conducted in all patients and absolute myocardial flow was estimated using four published compartmental models. The extraction fraction during hyperemic flow was iteratively estimated by maximizing the agreement between invasive CFR and FFR with the non-invasive analogs myocardial flow reserve (MFR) and relative flow reserve (RFR) at similar physiological states, respectively.

RESULTS

Using the new patient-determined EFs, agreement between CFR vs MFR for Model 1 and 2 was moderate and poor for Model 3 and 4. All models showed moderate agreement for FFR vs RFR. When using published models of animal-determined EFs, agreement between CFR vs MFR remained moderate for Model 1 and 2, and poor for Model 3 and 4. Similarly, all models showed moderate agreement for FFR vs RFR using animal-determined EF values. None of the observed differences were statistically significant.

CONCLUSIONS

Flow measurements using extraction fraction correction for [N-13]-ammonia based on calibration to invasive intracoronary angiography physiological measures in patients with CAD were not discordant from those reported in the literature. Either patient-determined or traditional animal-determined EF correction, when used with the appropriate flow model, yields moderate agreement with invasive measurements of coronary flow reserve and fractional flow reserve.

Clinically viable myocardial CCTA segmentation for measuring vessel-specific myocardial blood flow from dynamic PET/CCTA hybrid fusion

Background

Positron emission tomography (PET)-derived LV MBF quantification is usually measured in standard anatomical vascular territories potentially averaging flow from normally perfused tissue with those from areas with abnormal flow supply. Previously we reported on an image-based tool to noninvasively measure absolute myocardial blood flow at locations just below individual epicardial vessel to help guide revascularization. The aim of this work is to determine the robustness of vessel-specific flow measurements (MBF^vs) extracted from the fusion of dynamic PET (dPET) with coronary computed tomography angiography (CCTA) myocardial segmentations, using flow measured from the fusion with CCTA manual segmentation as the reference standard.

Methods

Forty-three patients’ ¹³NH₃ dPET, CCTA image datasets were used to measure the agreement of the MBF^vs profiles after the fusion of dPET data with three CCTA anatomical models: (1) a manual model, (2) a fully automated segmented model and (3) a corrected model, where major inaccuracies in the automated segmentation were briefly edited. Pairwise accuracy of the normality/abnormality agreement of flow values along differently extracted vessels was determined by comparing, on a point-by-point basis, each vessel’s flow to corresponding vessels’ normal limits using Dice coefficients (DC) as the metric.

Results

Of the 43 patients CCTA fully automated mask models, 27 patients’ borders required manual correction before dPET/CCTA image fusion, but this editing process was brief (2–3 min) allowing a 100% success rate of extracting MBF^vs in clinically acceptable times. In total, 124 vessels were analyzed after dPET fusion with the manual and corrected CCTA mask models yielding 2225 stress and 2122 rest flow values. Forty-seven vessels were analyzed after fusion with the fully automatic masks producing 840 stress and 825 rest flow samples. All DC coefficients computed globally or by territory were ≥ 0.93. No statistical differences were found in the normal/abnormal flow classifications between manual and corrected or manual and fully automated CCTA masks.

Conclusion

Fully automated and manually corrected myocardial CCTA segmentation provides anatomical masks in clinically acceptable times for vessel-specific myocardial blood flow measurements using dynamic PET/CCTA image fusion which are not significantly different in flow accuracy and within clinically acceptable processing times compared to fully manually segmented CCTA myocardial masks.

Precise characterization of a solitary pulmonary nodule using tumor shadow disappearance rate-corrected F-18 FDG PET and enhanced CT

We aimed to characterize solitary pulmonary nodule (SPN) using imaging parameters for F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) or enhanced CT corrected by tumor shadow disappearance rate (TDR) to reflect the tissue density.We enrolled 51 patients with an SPN who underwent PET/CT and chest CT with enhancement. The FDG uptake of SPN was evaluated using maximum standardized uptake value (SUVmax) on PET/CT. The mean Hounsfield unit (HU) for each SPN was evaluated over the region of interest on nonenhanced and enhanced CT images. The change in mean HU (HUpeak-pre) was quantified by subtracting the mean HU of the preenhanced CT from that of the post-enhanced CT. TDR was defined as the ratio of the tumor area, which disappears at a mediastinal window, to the tumor area of the lung window. We investigated which parameters (SUVmax or HUpeak-pre) could contribute to the characterization of SPN classified by TDR value and whether diagnostic performance could be improved using TDR-corrected imaging parameters.For SPN with higher tissue density (TDR <42%, n = 22), high value of SUVmax (≥3.1) was a significant factor to predict malignancy (P = .006). High value of HUpeak-pre (≥38) was a significant factor to characterize SPN (P = .002) with lower tissue density (TDR ≥42%, n = 29). The combined approach using TDR-corrected parameters had better predictive performance to characterize SPN than SUVmax only (P = .031).Applying imaging parameters such as SUVmax or HUpeak-pre in consideration of tissue density calculated with TDR could contribute to accurate characterization of SPN.

Evaluation of Non-infarct-Related Arteries Using C-11 Acetate PET in STEMI With Multivessel Disease

BACKGROUND

We analyzed whether C-11 acetate positron emission tomography (PET) can be used for the evaluation of non-infarct-related artery (NIRA) in patients with ST-elevation myocardial infarction (STEMI) and multivessel disease.

METHODS

We prospectively enrolled 31 patients with STEMI and at least one NIRA stenosis (diameter stenosis [DS] ≥ 50%). C-11 acetate PET was performed after successful revascularization for the infarct-related artery (IRA). Myocardial blood flow (MBF) and oxidative metabolism (k_mono) were measured and compared between NIRA vs. IRA, stenotic (DS ≥ 50%) vs. non-stenotic (DS < 50%) NIRAs, and NIRAs with significant stenosis (DS ≥ 70% or fractional flow reserve [FFR] ≤ 0.80) vs. those without (neither DS ≥ 70% nor FFR ≤ 0.80). The correlations between PET and angiographic parameters were also analyzed.

RESULTS

MBF and k_mono were significantly higher in NIRAs than those in IRAs. Stenotic NIRAs showed significantly reduced stress MBF, myocardial flow reserve (MFR), relative flow reserve (RFR) (0.72 ± 0.12 vs. 0.82 ± 0.14; p = 0.001), and stress k_mono, as compared to those in non-stenotic NIRAs. NIRAs with significant stenosis had significantly lower stress MBF, MFR, and RFR (0.70 ± 0.10 vs. 0.80 ± 0.14; p = 0.001). RFR showed the best, but modest linear correlation with DS of NIRA stenosis (r = −0.429, p = 0.001). RFR > 0.81 could effectively exclude the presence of significant NIRA stenosis.

CONCLUSIONS

C-11 acetate PET could be a feasible alternative noninvasive modality in patients with STEMI and multivessel disease, by excluding the presence of significant NIRA stenosis.

Prediction of radiation-related cardiotoxicity using F-18 FDG PET in non-small-cell lung cancer

Background

Radiation-related cardiotoxicity has been refocused nowadays as the follow-up was increased amomg the patients with advanced lung cancer. The early recognition of the occult cardiotoxicity enables the early intervention preventing clinically significant cardiac events or worsening of severity.

Purpose

We aim to search whether the F-18 fluorodeoxyglucose positron emission tomography (FDG PET) performed immediately after radiotherapy could predict the late cardiac events.

Methods

We retrospectively enrolled 133 patients with locally advanced, unresectable stage III NSCLC who underwent F-18 fluorodeoxyglucose positron emission tomography (FDG PET) immediately after CCRT for the response evaluation and survived at least for 6 months. Heart was recontoured according to the RTOG 0617 secondary analysis atlas for the dose volume analysis. Standardized uptake values (SUV) of the left ventricular myocardium were measured on FDG PET images. The patients were regularly followed up for the disease progression and complications. The primary end-point was the cardiac events grade ≥2 based on the Common Terminology Criteria for Adverse Events (version 5.0).

Results

FDG PET was performed at median interval of 11 days after CCRT. Fourty-two patients experienced cardiotoxicity during a median follow-up of 47 months (range, 12 – 123 months). In univariable analysis, mean heart dose, maximum SUV of the left ventricle (LV SUVmax), white blood cell count, and diabetes were associated with the risk of cardiotoxicity. In multivariable analysis, only higher mean heart dose (&gt;11.1 Gy, hazard ratio 3.930 [95% confidence interval 1.933–7.988]; p=0.0002) and higher LV SUVmax (&gt;12.84, 2.189 [1.162–4.124]; p=0.0152) were independently associated with increased risk of cardiotoxicity. In subgroup analyses, LV SUVmax remained predictive of cardiotoxicity among those with higher mean heart dose, but not among those with lower mean heart dose.

Conclusion

Early FDG PET after CCRT for NSCLC could predict the late cardiac events, especially in patients with high dose cardiac irradiation.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): This work was supported by a grant of the Basic Science Research Program through the National Research Foundation funded by the Ministry of Education, Republic of Korea (Principal Investigator: Sang-Geon Cho)

Impact of COVID-19 Pandemic on Cardiovascular Testing in Asia

Background

The coronavirus disease-2019 (COVID-19) pandemic significantly affected management of cardiovascular disease around the world. The effect of the pandemic on volume of cardiovascular diagnostic procedures is not known.

Objectives

This study sought to evaluate the effects of the early phase of the COVID-19 pandemic on cardiovascular diagnostic procedures and safety practices in Asia.

Methods

The International Atomic Energy Agency conducted a worldwide survey to assess changes in cardiovascular procedure volume and safety practices caused by COVID-19. Testing volumes were reported for March 2020 and April 2020 and were compared to those from March 2019. Data from 180 centers across 33 Asian countries were grouped into 4 subregions for comparison.

Results

Procedure volumes decreased by 47% from March 2019 to March 2020, showing recovery from March 2020 to April 2020 in Eastern Asia, particularly in China. The majority of centers cancelled outpatient activities and increased time per study. Practice changes included implementing physical distancing and restricting visitors. Although COVID testing was not commonly performed, it was conducted in one-third of facilities in Eastern Asia. The most severe reductions in procedure volumes were observed in lower-income countries, where volumes decreased 81% from March 2019 to April 2020.

Conclusions

The COVID-19 pandemic in Asia caused significant reductions in cardiovascular diagnostic procedures, particularly in low-income countries. Further studies on effects of COVID-19 on cardiovascular outcomes and changes in care delivery are warranted.

KSNM60 in Cardiology: Regrowth After a Long Pause

The Korean Society of Nuclear Medicine (KSNM) is celebrating its 60th anniversary in honor of the nuclear medicine professionals who have dedicated their efforts towards research, academics, and the more comprehensive clinical applications and uses of nuclear imaging modalities. Nuclear cardiology in Korea was at its prime time in the 1990s, but its growth was interrupted by a long pause. Despite the academic and practical challenges, nuclear cardiology in Korea now meets the second leap, attributed to the growth in molecular imaging tailored for many non-coronary diseases and the genuine values of nuclear myocardial perfusion imaging. In this review, we describe the trends, achievements, challenges, and perspectives of nuclear cardiology throughout the 60-year history of the KSNM.

Dynamic cardiac PET motion correction using 3D normalized gradient fields in patients and phantom simulations

This work expands on the implementation of three-dimensional (3D) normalized gradient fields to correct for whole-body motion and cardiac creep in [N-13]-ammonia patient studies and evaluates its accuracy using a dynamic phantom simulation model.

METHODS

A full rigid-body algorithm was developed using 3D normalized gradient fields including a multi-resolution step and sampling off the voxel grid to reduce interpolation artifacts. Optimization was performed using a weighted similarity metric that accounts for opposing gradients between images of blood pool and perfused tissue without the need for segmentation. Forty-three retrospective dynamic [N-13]-ammonia PET/CT rest/adenosine-stress patient studies were motion corrected and the mean motion parameters plotted at each frame time point. Motion correction accuracy was assessed using a comprehensive dynamic XCAT simulation incorporating published physiologic parameters of the heart's trajectory following adenosine infusion as well as corrupted attenuation correction commonly observed in clinical studies. Accuracy of the algorithm was assessed objectively by comparing the errors between isosurfaces and centers of mass of the motion corrected XCAT simulations.

RESULTS

In the patient studies, the overall mean cranial-to-caudal translation was 7 mm at stress over the duration of the adenosine infusion. Noninvasive clinical measures of relative flow reserve and myocardial flow reserve were highly correlated with their invasive analogues. Motion correction accuracy assessed with the XCAT simulations showed an error of <1 mm in late perfusion frames that broadened gradually to <3 mm in earlier frames containing blood pool.

CONCLUSION

This work demonstrates that patients undergoing [N-13]-ammonia dynamic PET/CT exhibit a large cranial-to-caudal translation related to cardiac creep primarily at stress and to a lesser extent at rest, which can be accurately corrected by optimizing their 3D normalized gradient fields. Our approach provides a solution to the challenging condition where the image intensity and its gradients are opposed without the need for segmentation and remains robust in the presence of PET-CT mismatch.

Increasing Use of Cardiac PET/CT for Inflammatory and Infiltrative Heart Diseases in Korea

Recently the incidence of inflammatory and infiltrative heart diseases is increasing in Korea. Cardiac PET/CT is a useful technology evaluating inflammatory and infiltrative heart diseases. This study analyzed trends in the use of cardiac PET/CT for evaluating inflammatory and infiltrative heart diseases in the Chonnam National University Hospital and Chonnam National University Hwasun Hospital. The general trend in Korea was also assessed based on the domestic nuclear medicine database. There was a common increasing trend in the number of F-18 FDG PET/CT for the evaluation of inflammatory and infiltrative heart diseases. A representative case with cardiac sarcoidosis is illustrated.

Change of Therapeutic Response Classification According to Recombinant Human Thyrotropin-Stimulated Thyroglobulin Measured at Different Time Points in Papillary Thyroid Carcinoma

Purpose

We investigated whether response classification after total thyroidectomy and radioactive iodine (RAI) therapy could be affected by serum levels of recombinant human thyrotropin (rhTSH)-stimulated thyroglobulin (Tg) measured at different time points in a follow-up of patients with papillary thyroid carcinoma (PTC).

Methods

A total of 147 PTC patients underwent serum Tg measurement for response assessment 6 to 24 months after the first RAI therapy. Serum Tg levels were measured at 24 h (D1Tg) and 48-72 h (D2-3Tg) after the 2^nd injection of rhTSH. Responses were classified into three categories based on serum Tg corresponding to the excellent response (ER-Tg), indeterminate response (IR-Tg), and biochemical incomplete response (BIR-Tg). The distribution pattern of response classification based on serum Tg at different time points (D1Tg vs. D2-3Tg) was compared.

Results

Serum D2-3Tg level was higher than D1Tg level (0.339 ng/mL vs. 0.239 ng/mL, P < 0.001). The distribution of response categories was not significantly different between D1Tg-based and D2-3Tg-based classification. However, 8 of 103 (7.8%) patients and 3 of 40 (7.5%) patients initially categorized as ER-Tg and IR-Tg based on D1Tg, respectively, were reclassified to IR-Tg and BIR-Tg based on D2-3Tg, respectively. The optimal cutoff values of D1Tg for the change of response categories were 0.557 ng/mL (from ER-Tg to IR-Tg) and 6.845 ng/mL (from IR-Tg to BIR-Tg).

Conclusion

D1Tg measurement was sufficient to assess the therapeutic response in most patients with low level of D1Tg. Nevertheless, D2-3Tg measurement was still necessary in the patients with D1Tg higher than a certain level as response classification based on D2-3Tg could change.

Differences in diagnostic impact of dual-tracer PET/computed tomography according to the extrahepatic metastatic site in patients with hepatocellular carcinoma

OBJECTIVES

We compared the diagnostic performance of C-11 acetate and F-18 fluorodeoxyglucose (FDG) PET/computed tomography (CT) for the detection of extrahepatic metastasis in patients with hepatocellular carcinoma (HCC) and evaluated whether the improvement in the diagnostic performance of dual tracer PET/CT differs by the metastatic site.

METHODS

Fifty-eight patients who had extrahepatic metastasis on either C-11 acetate or F-18 FDG PET/CT were enrolled, and 193 metastatic lesions were analyzed in this retrospective study. The metastatic lesions were categorized based on six sites of involvement. According to each involved site, the tracer avidity of the metastatic lesions was compared using the maximum standardized uptake value (SUVmax).

RESULTS

Bone was the most frequent categorized metastatic site (44.8%), followed by lymph node (39.7%), lung (34.5%), soft tissue (27.6%), adrenal gland (6.9%), and vascular category (3.4%). C-11 acetate PET/CT showed a higher SUVmax than F-18 FDG PET/CT in metastatic bone lesions (P = 0.003). F-18 FDG uptake was significantly higher than C-11 acetate uptake in metastatic lymph node lesions (P < 0.001). The detection rate of dual tracer PET/CT was significantly higher in the metastatic lung (93.6%) and soft tissue (100%) lesions. However, the diagnostic performance of dual tracer PET/CT was limited in the metastatic bone and lymph node lesions because each tracer's detection rate was very high (bone: 94.6% in C-11 acetate, lymph node: 94.1% in F-18 FDG).

CONCLUSIONS

The tracer avidity of metastatic lesions differed according to the involved site. This difference affected the complementary role of dual tracer PET/CT in the diagnosis of extrahepatic metastases in patients with HCC.

Comparison of diagnostic accuracy of PET-derived myocardial blood flow parameters: A meta-analysis

BACKGROUND

Although absolute quantification of myocardial blood flow (MBF) by positron emission tomography provides additive diagnostic value to visual analysis of perfusion defect, diagnostic accuracy of different MBF parameters remain unclear.

METHODS

Clinical studies regarding the diagnostic accuracy of hyperemic MBF (hMBF), myocardial flow reserve (MFR) and/or relative flow reserve (RFR) were searched and systematically reviewed. On a per-vessel basis, pooled measures of the parameters' diagnostic performances were analyzed, regarding significant coronary stenosis defined by fractional flow reserve or diameter stenosis.

RESULTS

Ten studies (2,522 arteries from 1,099 patients) were finally included. Pooled sensitivity [95% confidence interval (CI)] was 0.853 (0.821-0.881) for hMBF, 0.755 (0.713-0.794) for MFR, and 0.636 (0.539-0.726) for RFR. Pooled specificity (95% CI) was 0.844 (0.827-0.860) for hMBF, 0.804 (0.784-0.824) for MFR, and 0.897 (0.860-0.926) for RFR. Pooled area under the curve ± standard error was 0.900 ± 0.020 for hMBF, 0.830 ± 0.026 for MFR, and 0.873 ± 0.048 for RFR.

CONCLUSIONS

hMBF showed the best sensitivity while RFR showed the best specificity in the diagnosis of significant coronary stenosis. MFR was less sensitive than hMBF and less specific than hMBF and RFR.

Association between FDG uptake in the right ventricular myocardium and cancer therapy-induced cardiotoxicity

BACKGROUND

The aim of this study was to investigate changes in myocardial uptake evaluated by oncologic 18F-fluorodeoxyglucose (FDG) PET/CT scans and to determine the relationship between myocardial FDG uptake and cancer therapy-induced cardiotoxicity in breast cancer patients who underwent anthracycline or trastuzumab.

METHODS

We reviewed 121 consecutive patients who underwent oncologic FDG PET/CT and echocardiography at baseline and post-therapy with anthracyclines or trastuzumab for breast cancer. Grade in LV wall, uptake pattern in LV wall, and the presence of RV wall uptake were assessed by visual analysis, and the mean SUV in the LV and RV walls and the change of SUV (ΔSUV) between baseline and post-therapy PET/CT were measured by quantitative analysis. Multiple logistic regression analyses were performed to evaluate the association between PET parameters and cardiotoxicity.

RESULTS

Fifteen patients (12%) showed cardiotoxicity after therapy. The cardiotoxic group tended to show more diffuse LV uptake, higher SUV, and ΔSUV of RV wall than the non-cardiotoxic group following therapy with anthracyclines or trastuzumab. Logistic regression analysis showed that the presence of RV wall uptake, SUV of RV wall (> 1.8), and ΔSUV of RV wall (> 0.4) were significantly associated with cardiotoxicity after controlling for age, radiotherapy, and treatment.

CONCLUSIONS

The presence of RV wall uptake and the increase of SUV of RV wall on post-therapy PET/CT were associated with cardiotoxicity in breast cancer patients who underwent anthracycline or trastuzumab. Oncologic FDG PET/CT scans can provide information regarding cancer therapy-induced cardiotoxicity as well as tumor response.

Vessel-specific quantification of absolute myocardial blood flow, myocardial flow reserve and relative flow reserve by means of fused dynamic 13NH3 PET and CCTA: Ranges in a low-risk population and abnormality criteria

OBJECTIVES

The goal of the present work is to present a novel methodology for the extraction of MBF, MFR and RFR along coronary arteries by means of multimodality image fusion of dynamic PET and CCTA images.

BACKGROUND

FFR is the reference standard to identify flow-limiting lesions, but its invasiveness limits broad application. New noninvasive methodologies are warranted to stratify patients and guide treatment.

METHODS

A group of 16 low-risk CAD subjects who underwent both 13NH3 PET and CCTA were analyzed. Image fusion techniques were employed to align the studies and CCTA-derived anatomy used to identify coronaries trajectories. MBF was calculated by means of a 1-tissue compartmental model for the standard vascular territories and along patient-specific vessel paths from the base to the apex of the heart.

RESULTS

Low-risk ranges for MBF. MFR and RFR for LAD, LCX and rPDA were computed for the entire cohort and separated by gender. Computed low-risk ranges were used to assess a prospective patient with suspected CAD.

CONCLUSIONS

Our vessel-specific functional indexes and 3D displays offer promise to more closely replicate what is commonly performed during a catheterization session and have the potential of providing effective noninvasive tools for the identification of flow-limiting lesions and image-guided therapy.

Clinical Impact of F-18 FDG PET-CT on Biopsy Site Selection in Patients with Suspected Bone Metastasis of Unknown Primary Site

Purpose

We investigated the clinical role of F-18 fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) in the identification of the primary site and the selection of the optimal biopsy site in patients with suspected bone metastasis of unknown primary site.

Methods

The patients with suspected bone metastasis who underwent PET-CT for evaluation of primary site were enrolled in this study. The primary sites were identified by the histopathologic or imaging studies and were classified according to the FDG uptake positivity of the primary site. To evaluate the guiding capability of PET-CT in biopsy site selection, we statistically analyzed whether the biopsy site could be affected according to the presence of extra-skeletal FDG uptake.

Results

Among 74 enrolled patients, 51 patients had a metastatic bone disease. The primary site was identified in 48 of 51 patients (94.1%). Forty-six patients were eligible to test the association of clinical choice of biopsy site with PET positivity of extra-skeletal lesion. The extra-skeletal biopsies were done in 42 out of 43 patients with positive extra-skeletal uptake lesions. Bone biopsies were inevitably performed in the other three patients without extra-skeletal uptake lesions. The association came out to be significant (Fisher's exact test, P < 0.001).

Conclusion

F-18 FDG PET-CT significantly contributed not only to identify the primary site but also to suggest optimal biopsy sites in patients with suspected bone metastasis.

Rationale and design of the quantification of myocardial blood flow using dynamic PET/CTA-fused imagery (DEMYSTIFY) to determine physiological significance of specific coronary lesions

BACKGROUND

Coronary physiology assessments have been shown by multiple trials to add clinical value in detecting significant coronary artery disease and predicting cardiovascular outcomes. Fractional flow reserve (FFR) obtained during invasive coronary angiography (ICA) has become the new reference standard for hemodynamic significance detection. Absolute myocardial blood flow (MBF) quantification by means of dynamic positron emission tomography (dPET) has high diagnostic and prognostic values. FFR is an invasive measure and as such cannot be applied broadly, while MBF quantification is commonly performed on standard vascular territories intermixing normal flow from normal regions with abnormal flow from abnormal regions and consequently limiting its diagnostic power.

OBJECTIVE

The aim of this study is to provide physicians with reliable software tools for the non-invasive assessment of lesion-specific physiological significance for the entire coronary tree by combining PET-derived absolute flow data and coronary computed tomography angiography (CTA)-derived anatomy and coronary centerlines.

METHODS

The dynamic PET/CTA myocardial blood flow assessment with fused imagery (DEMYSTIFY) study is an observational prospective clinical study to develop algorithms and software tools to fuse coronary anatomy data obtained from CTA with dPET data to non-invasively measure absolute MBF, myocardial flow reserve, and relative flow reserve across specific coronary lesions. Patients (N = 108) will be collected from 4 institutions (Emory University Hospital, USA; Chonnam National University Hospital, South Korea; Samsung Medical Center, South Korea; Seoul National University Hospital, South Korea). These results will be compared to those obtained invasively in the catheterization laboratory and to a relatively novel non-invasive technique to estimate FFR based on CTA and computational fluid dynamics.

CONCLUSIONS

Success of these developments should lead to the following benefits: (1) eliminate unnecessary invasive coronary angiography in patients with no significant lesions, (2) avoid stenting physiologically insignificant lesions, (3) guide percutaneous coronary interventions process to the location of significant lesions, (4) provide a flow-color-coded 3D roadmap of the entire coronary tree to guide bypass surgery, and (5) use less radiation and lower the cost from unnecessary procedures.

TRIAL REGISTRY

The DEMYSTIFY study has been registered on ClinicalTrials.gov with registration number NCT04221594.

Risk factors of malignant fluorodeoxyglucose-avid lymph node on preablation positron emission tomography in patients with papillary thyroid cancer undergoing radioiodine ablation therapy

F-18 fluorodeoxyglucose (FDG)-avid metastatic lesions are associated with a poor response to radioiodine ablation therapy (RIT) in papillary thyroid cancer (PTC). This study evaluated the significance of preablative FDG positron emission tomography (PET) for the assessment of risk factors and frequency of malignant FDG-avid lymph nodes in patients with PTC undergoing RIT.The study included 339 consecutive patients (mean age 46.3 ± 12.5 y; 260 females) with PTC referred for the first RIT and who underwent routine preablative FDG PET between April 2011 and February 2013. FDG-avid lymph nodes (FALNs) were identified using retrospective image reviews. The frequency of malignant FALN (mFALN), its contribution to persistent or recurrent PTC, and its risk factors were analyzed.Among the patients, 112 had FALNs (33.0%): 11 mFALNs (3.2%) and 101 benign FALNs (bFALNs, 29.8%). mFALN contributed to 55% of persistent or recurrent PTC after RIT, which was observed in 20 of 339 patients (5.9%) during the post-RIT follow-up. Among preoperative risk factors, suspicious extrathyroidal extension and lateral neck lymph node metastasis on imaging studies were associated with mFALN. Among postoperative risk factors, T3/T4 and N1b stages, higher stimulated thyroglobulin, and higher numbers of metastatic lymph nodes and dissected lymph nodes, were associated with mFALN.mFALNs were observed in a small number of patients with PTC undergoing RIT, but it contributed 55% of total recurrent or persistent disease. Increased frequency of mFALNs is associated with more advanced PTC. Preablative FDG PET has value in evaluation of patients with RIT-resistant lesions and may help determine further treatment strategies.

Diagnostic Reference Levels for Adult Nuclear Medicine Imaging Established from the National Survey in Korea

Purpose

There is substantial need for optimizing radiation protection in nuclear medicine imaging studies. However, the diagnostic reference levels (DRLs) have not yet been established for nuclear medicine imaging studies in Korea.

Materials and Methods

The data of administered activity in 32 nuclear medicine imaging studies were collected from the Korean Society of Nuclear Medicine (KSNM) dose survey database from 2013 and 2014. Through the expert discussions and statistical analyses, the 75th quartile value (Q3) was suggested as the preliminary DRL values. Preliminary DRLs were subjected to approval process by the KSNM Board of Directors and KSNM Council, followed by clinical applications and performance rating by domestic institutes.

Results

DRLs were determined through 32 nuclear medicine imaging studies. The Q3 value was considered as appropriate selection as it was generally consistent with the most commonly administered activity. In the present study, the final version of initial DRL values for nuclear medicine imaging in Korean adults is described including various protocols of the brain and myocardial perfusion imaging.

Conclusion

The first DRLs for nuclear medicine imaging in Korean adults were confirmed. The DRLs will enable optimized radiation protection in the field of nuclear medicine imaging in Korea.

Association of muscle and visceral adipose tissues with the probability of Alzheimer's disease in healthy subjects

Increasing evidence indicates that sarcopenia and obesity can be risk factors for incident dementia. We investigated the association of body composition including muscle and visceral adipose tissue (VAT) with the probability of Alzheimer’s disease (AD) in healthy middle-aged and elderly subjects using ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT). This study included 110 healthy subjects with available whole-body FDG PET/CT scans and medical records. Muscle and VAT tissues were measured on the abdominal CT slice, and the PMOD Alzheimer’s discrimination FDG PET analysis tool (PALZ) score was evaluated on the brain PET of the same subject using software PALZ. Skeletal muscle index (r: −0.306; P = 0.031) was significantly negatively associated with the PALZ score in the elderly patients. Muscle area (β: −0.640; P = 0.043) and skeletal muscle index (β: −0.557; P = 0.043) were independently associated with the PALZ score in elderly subjects after adjustments for sex, duration of education, hypertension, diabetes mellitus, and smoking and drinking status. Increased muscle tissue was associated with a lower probability of AD in elderly subjects, but VAT was not associated with a lower probability of AD in middle-or older-aged adults.

Emerging Tracers for Nuclear Cardiac PET Imaging

Myocardial perfusion imaging using positron emission tomography (PET) has several advantages over single photon emission computed tomography (SPECT). The recent advances in SPECT technology have shown promise, but there is still a large need for PET in the clinical management of coronary artery disease (CAD). Especially, absolute quantification of myocardial blood flow (MBF) using PET is extremely important. In spite of considerable advances in the diagnosis of CAD, novel PET radiopharmaceuticals remain necessary for the diagnosis of CAD because clinical use of current cardiac radiotracers is limited by their physical characteristics, such as decay mode, emission energy, and half-life. Thus, the use of a radioisotope that has proper characteristics and a proper half-life to develop myocardial perfusion agents could overcome these limitations. In this review, the current state of cardiac PET and a general overview of novel 18F or 68Ga-labeled radiotracers, including their radiosynthesis, in vivo characterization, and evaluation, are provided. The future perspectives are discussed in terms of their potential usefulness based on new image analysis methods and hybrid imaging.

Response Prediction of Altered Thyroglobulin Levels After Radioactive Iodine Therapy Aided by Recombinant Human Thyrotropin in Patients with Differentiated Thyroid Cancer

Purpose

Thyroglobulin (Tg) may be released from damaged residual thyroid tissues after radioactive iodine (RAI) therapy in patients with differentiated thyroid carcinoma (DTC). We investigated whether altered levels of serum Tg after recombinant human thyrotropin (rhTSH)-aided RAI therapy could be a prognostic marker in patients with DTC.

Methods

We evaluated 68 patients who underwent RAI therapy after total thyroidectomy. Serum Tg levels were measured just before RAI administration (D0Tg) and 7 days after RAI therapy (D7Tg). Patients with a D0Tg level greater than 2.0 ng/mL were excluded to more precisely evaluate the injury effect of RAI in small remnant tissues. The ratioTg was defined as the D7Tg level divided by that on D0Tg. The therapeutic responses were classified as acceptable or non-acceptable. Finally, we investigated which clinicopathologic parameters were associated with therapeutic response.

Results

At the follow-up examination, an acceptable response was observed in 50 patients (73.5%). Univariate analysis revealed significant differences in N stage (P = 0.003) and ratioTg (acceptable vs. non-acceptable responses, 21.9 ± 33.6 vs. 3.8 ± 6.5; P = 0.006). In multivariate analysis, only ratioTg significantly predicted an acceptable response (odds ratio 1.104; 95% confidence interval 1.005-1.213; P = 0.040). A ratioTg above 3.5 predicted an acceptable response with a sensitivity of 66.0%, specificity of 83.3%, and accuracy of 70.6% (area under the curve = 0.718; P = 0.006).

Conclusions

Altered levels of serum Tg after RAI therapy, calculated as the ratioTg (D7Tg/D0Tg), significantly predicted an acceptable response in patients with DTC.

Optimization of diagnostic performance for differentiation of recurrence from radiation necrosis in patients with metastatic brain tumors using tumor volume-corrected 11C-methionine uptake

Background

Tumor to normal tissue ratio (T/N ratio) on ¹¹C-methionine (¹¹C-MET) positron emission tomography/computed tomography (PET/CT) is affected by variable factors. We investigated whether T/N ratio cutoff values corrected according to metabolic tumor volume (MTV) could improve the diagnostic performance of ¹¹C-MET PET/CT for diagnosis of recurrence in patients with metastatic brain tumor.

Forty-eight patients with metastatic brain tumors underwent ¹¹C-MET PET/CT for differential diagnosis between recurrence and radiation necrosis after gamma knife radiosurgery (GKR). Both T/N ratio and MTV were estimated in each lesion on ¹¹C-MET PET/CT. The lesions were classified into three groups based on MTV criteria (≤ 0.5 cm³; > 0.5, ≤ 4.0 cm³; and > 4.0 cm³). The optimal cutoff values of the T/N ratio from receiver operating characteristic (ROC) curve were determined in each group (MTV-corrected) as well as total lesions (non-corrected). Finally, diagnostic performance of ¹¹C-MET PET/CT was compared with the MTV-corrected cutoff values.

Results

Among 77 lesions, 51 were diagnosed with recurrence. The mean T/N ratio was 2.25 (± 1.12) for recurrent lesions and 1.44 (± 0.22) for radiation necrosis (P < 0.001). T/N ratio of 1.61 (non-corrected) provided the best sensitivity, specificity, and diagnostic accuracy (70.6, 80.8, and 74.0%, respectively). Using the MTV criteria, optimal cutoff values of the T/N ratios in each group were 1.23 (MTV ≤ 0.5 cm³), 1.54 (0.5 cm³ < MTV ≤ 4.0 cm³), and 1.85 (MTV > 4.0 cm³). In small-sized lesions (MTV ≤ 0.5 cm³), MTV-corrected cutoff values (1.23) could maintain favorable diagnostic performance with sensitivity, specificity, and diagnostic accuracy (70.0, 80.0, and 73.3%, respectively), compared to non-corrected cutoff values.

Conclusions

MTV-corrected cutoff values of T/N ratio could maintain the diagnostic performance of ¹¹C-MET PET/CT in small sized, metastatic brain tumors. We expect our results to contribute to reproducible and standardized interpretation of ¹¹C-MET PET/CT.

Radiation Safety in Nuclear Medicine Procedures

Since the nuclear disaster at the Fukushima Daiichi Nuclear Power Plant in 2011, radiation safety has become an important issue in nuclear medicine. Many structured guidelines or recommendations of various academic societies or international campaigns demonstrate important issues of radiation safety in nuclear medicine procedures. There are ongoing efforts to fulfill the basic principles of radiation protection in daily nuclear medicine practice. This article reviews important principles of radiation protection in nuclear medicine procedures. Useful references, important issues, future perspectives of the optimization of nuclear medicine procedures, and diagnostic reference level are also discussed.

Preparation for radioactive iodine therapy is not a risk factor for the development of hyponatremia in thyroid cancer patients

The aim of this study was to evaluate whether the preparation for radioactive iodine (RAI) therapy by thyroid hormone withdrawal (THW) or a low-iodine diet (LID) can be risk factors for the development of hyponatremia in patients with differentiated thyroid cancer after thyroidectomy.We retrospectively reviewed the medical records and laboratory findings of 326 patients who underwent preparation for RAI therapy after thyroidectomy from 2012 to 2014. Demographic and clinical variables including the method of thyrotropin stimulation and duration of LID were assessed. Serum sodium was measured twice, before operation and before RAI therapy.Hyponatremia was detected in only 3 patients (0.9%) before operation, but in 15 patients (4.6%) before RAI therapy. None of the patients had severe hyponatremia after preparation for RAI therapy. Pre-RAI therapy serum sodium was correlated with the method of thyrotropin stimulation (TWH vs recombinant human thyroid stimulating hormone, P = 0.014) and duration of LID (r = -0.131, P = 0.018); however, the preparation of RAI therapy, THW and LID, did not affect the development of hyponatremia in logistic regression analysis. Preoperative serum sodium was a significant risk factor for hyponatremia during preparation for RAI therapy.Preparation for RAI therapy by THW or LID is not a risk factor for the development of hyponatremia in patients with thyroid cancer. The development of hyponatremia was neither frequent nor severe during preparation for RAI therapy. Physicians should not be greatly concerned about rare life-threatening hyponatremia during preparation for RAI therapy.

Usefulness of 3-dimensional stereotactic surface projection FDG PET images for the diagnosis of dementia

To compare diagnostic performance and confidence of a standard visual reading and combined 3-dimensional stereotactic surface projection (3D-SSP) results to discriminate between Alzheimer disease (AD)/mild cognitive impairment (MCI), dementia with Lewy bodies (DLB), and frontotemporal dementia (FTD).[F]fluorodeoxyglucose (FDG) PET brain images were obtained from 120 patients (64 AD/MCI, 38 DLB, and 18 FTD) who were clinically confirmed over 2 years follow-up. Three nuclear medicine physicians performed the diagnosis and rated diagnostic confidence twice; once by standard visual methods, and once by adding of 3D-SSP. Diagnostic performance and confidence were compared between the 2 methods.3D-SSP showed higher sensitivity, specificity, accuracy, positive, and negative predictive values to discriminate different types of dementia compared with the visual method alone, except for AD/MCI specificity and FTD sensitivity. Correction of misdiagnosis after adding 3D-SSP images was greatest for AD/MCI (56%), followed by DLB (13%) and FTD (11%). Diagnostic confidence also increased in DLB (visual: 3.2; 3D-SSP: 4.1; P < 0.001), followed by AD/MCI (visual: 3.1; 3D-SSP: 3.8; P = 0.002) and FTD (visual: 3.5; 3D-SSP: 4.2; P = 0.022). Overall, 154/360 (43%) cases had a corrected misdiagnosis or improved diagnostic confidence for the correct diagnosis.The addition of 3D-SSP images to visual analysis helped to discriminate different types of dementia in FDG PET scans, by correcting misdiagnoses and enhancing diagnostic confidence in the correct diagnosis. Improvement of diagnostic accuracy and confidence by 3D-SSP images might help to determine the cause of dementia and appropriate treatment.

Giant Cell Tumor with Secondary Aneurysmal Bone Cyst Shows Heterogeneous Metabolic Pattern on 18F-FDG PET/CT: A Case Report

Giant cell tumor (GCT) is a generally benign bone tumor accounting for approximately 5 % of all primary bone neoplasms. Cystic components in GCTs that indicate secondary aneurysmal bone cysts (ABCs) are reported in 14 % of GCTs. Although both of them have been described separately in previous reports that may show considerable fluorodeoxyglucose (FDG) uptake despite their benign nature, the findings of GCT with secondary ABC on ¹⁸F-FDG positron emission tomography/computed tomography (PET/CT) have not been well-known. We report a case of GCT with secondary ABC in a 26-year-old woman. ¹⁸F-FDG PET/CT revealed a heterogeneous hypermetabolic lesion in the left proximal femur with the maximum standardized uptake value of 4.7. The solid components of the tumor showed higher FDG uptake than the cystic components. These observations suggest that the ABC components in GCTs show heterogeneous metabolic patterns on ¹⁸F-FDG PET/CT.

Abscess of Native Kidney Caused by Carbapenem-Resistant Acinetobacter baumannii (CRAB) in Renal Transplantation: A Case Report

BACKGROUND

Abscess of native kidney is a rare postoperative event after renal transplantation. This report describes a case of back pain, fever and pyuria caused by carbapenem-resistant Acinetobacter baumannii (CRAB) in a patient who underwent renal-transplantation.

CASE REPORT

A 40-year-old man, presenting with hypertension and renal failure, underwent renal transplantation 1 month previously. He developed sudden intense back pain and fever (39°C). There was normal blood flow in graft kidney but there were the swelling and cyst of right native kidney. We aspirated the pus in native kidney and performed the native nephrectomy. The carbapenem-resistant Acinetobacter baumannii (CRAB) was isolated as in pus and native kidney. We performed the tigecyline monotherapy during 3 weeks. He recovered without complication after treatment.

CONCLUSIONS

To our knowledge, no report in the literature to date describes abscess in native kidney secondary to CRAB in a renal transplant. Infections caused by CRAB have become critical for immunosuppressed patients. The presence of complication greater risk, by an organism whose pathogenicity and virulence are not yet elucidated should determine an aggressive empirical antimicrobial therapy.

Iodine Uptake Patterns on Post-ablation Whole Body Scans are Related to Elevated Serum Thyroglobulin Levels After Radioactive Iodine Therapy in Patients with Papillary Thyroid Carcinoma

PURPOSE

Serum thyroglobulin (Tg) level is frequently elevated shortly after radioactive iodine (RAI) ablation therapy. The authors studied the relationship between the elevation of serum Tg after RAI therapy and iodine uptake pattern on post-ablation whole body scans (RxWBSs) in patients with papillary thyroid carcinoma (PTC).

MATERIALS AND METHODS

The study subjects were patients with PTC that had undergone first RAI therapy with thyroid hormone withdrawal after total thyroidectomy. Patients with a high level of serum anti-Tg antibody (TgAb, ≥ 60 U/mL), possible regional or distant metastasis as determined by pre-ablation or post-ablation studies, and negative iodine uptake of the anterior neck on RxWBS were excluded. Serum Tg was checked twice, that is, 7 days after (post-ablation Tg) and on the day of RAI therapy (pre-ablation Tg). Ratio of pre-ablation Tg to post-ablation Tg (Tg ratio) was used to assess changes in serum Tg levels after RAI therapy. Patients were classified into two groups according to the presence of midline uptake above the thyroidectomy bed on RxWBS (negative (group 1) or positive (group 2) midline uptake). Variables were subjected to analysis to identify differences between the two groups.

RESULTS

Two hundred and fifty patients were enrolled in this study; 101 in group 1 and 149 in group 2. Based on univariate analysis, post-ablation Tg (8.12 ± 11.05 vs. 34.12 ± 54.31; P < 0.001) and Tg ratio (7.81 ± 8.98 vs. 20.01 ± 19.84; P < 0.001) were significantly higher in group 2. On the other hand, gender, tumor (T) stage, lymph node (N) stage, size, multiplicity or bilaterality of primary tumor, dose of ¹³¹I, serum TgAb and thyroid-stimulating hormone (TSH) level (before or after RAI therapy) were not significantly different in the two groups. Variables with P values of < 0.25 by univariate analysis were subjected to multivariate analysis, which showed post-ablation Tg (OR 1.060, 95 % CI = 1.028-1.092; P < 0.001) and Tg ratio (OR 1.059, 95 % CI = 1.028-1.092; P = 0.001) were significantly higher in group 2.

CONCLUSION

Serum Tg level after RAI therapy was significantly higher in patients with midline uptake on RxWBS, compared with patients without midline uptake on RxWBS. Further investigations are needed to reveal the correlation between serum Tg elevation and clinical outcome according to the presence of midline uptake.

Open-Mouth Bone Scintigraphy Is Better than Closed-Mouth Bone Scintigraphy in the Diagnosis of Temporomandibular Osteoarthritis

PURPOSE

Closed-mouth bone scintigraphy (CM scan) and closed-mouth single-photon emission computed tomography (CM SPECT) are used for conventional evaluation of osteoarthritis of the temporomandibular joint (TMJ). However, the adequacy of open-mouth bone scintigraphy (OM scan) has not yet been evaluated. Therefore, the purpose of this study was to compare the diagnostic performance of CM scan, CM SPECT, and OM scan.

METHODS

Thirty-six patients with suspicion of an abnormality of the TMJ and who underwent a (99m)Tc-HDP CM scan, CM SPECT, and an OM scan were enrolled. The scans were assessed visually for the presence of positive focal uptake in the TMJ. Osteoarthritis was defined as arthralgia plus crepitus or radiologic signs of arthrosis.

RESULTS

Of 72 TMJs, 21 (29.2 %) were diagnosed with osteoarthritis. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 90.5 %, 49.0 %, 42.2 %, 92.6 % and 61.1 % for the CM scan, 81.0 %, 58.8 %, 44.7 %, 88.2 % and 65.3 % for CM SPECT, and 81.0 %, 82.4 %, 65.4 %, 91.3 % and 81.9 % for the OM scan, respectively. The accuracy of the OM scan was higher than that of CM SPECT and the CM scans (p = 0.004 and p < 0.001, respectively).

CONCLUSIONS

The OM scan was more accurate than the conventional CM scan and even CM SPECT for diagnosing TMJ osteoarthritis.

Oral administration of Lactobacillus casei variety rhamnosus partially alleviates TMA-induced atopic dermatitis in mice through improving intestinal microbiota

AIMS

The purpose of this study was to investigate the effect of Lactobacillus casei variety rhamnosus (LCR35) on Atopic dermatitis (AD)-like symptoms in mice.

METHODS AND RESULTS

AD-like skin lesions in BALB/C mice were induced by sensitization and subsequent repeated challenges with trimellitic anhydride (TMA) for 10 days. LCR35 was orally administered to the mice once daily throughout the study. In the TMA-induced AD model, orally administered LCR35 suppressed significantly irritant-related scratching behaviour and skin dehydration as well as apparent severity of AD. LCR35 also significantly decreased serum levels of IgE and IL-4, but not IFN-γ, implying the restoration of TMA-induced disruption of Th1/Th2 balance. Quantitative real-time PCR targeting hypervariable regions of 16S rDNA gene of faecal microbiota indicated that the LCR35 treatment increased the population of Bifidobacterium, Lactobacilli, Enterococcus and Bacteroides fragilis group, but decreased those of Clostridium coccoides group.

CONCLUSIONS

LCR35 has the ability to suppress the development of AD in mice, possibly through the modulation of Th1/Th2 balance and gut microbiota.

SIGNIFICANCE AND IMPACT OF THE STUDY

LCR35 has a strong potential as a probiotic for preventing AD.

Stimulated Serum Thyroglobulin Level at the Time of First Dose of Radioactive Iodine Therapy Is the Most Predictive Factor for Therapeutic Failure in Patients With Papillary Thyroid Carcinoma

PURPOSE

To investigate the clinical importance of serum thyroglobulin (Tg) levels just before high-dose I-131 ablation therapy (preablation Tg) for predicting therapeutic failure in patients with papillary thyroid carcinoma (PTC).

METHODS

Patients with PTC (n = 132) undergoing total thyroidectomy followed by the first high-dose I-131 ablation therapy (HI-Rx) were included in this retrospective review. Just before HI-Rx, preablation Tg, anti-Tg antibody, and TSH were measured. The patients were followed up for a mean period of 7 months (range 6-23 months) by I-123 whole-body scans (f/u IWBS) and stimulated Tg (f/u Tg). Therapeutic failure was defined by positive f/u IWBS or f/u Tg >2 ng/ml. We classified patients into three groups according to the value of preablation Tg (group 1, <1 ng/ml; group 2, ≥1 and <10 ng/ml; group 3, ≥10 ng/ml) and compared clinical variables to therapeutic response.

RESULTS

Therapeutic failure was noted in 39 patients (29.5 %). On univariate analysis, T stage, tumor size, and preablation Tg were the statistically significant factors that could predict therapeutic failure. After multivariate analysis, preablation Tg was the only independent predictor of therapeutic failure (P < 0.001). The therapeutic failure rate was significantly increased as the preablation Tg level increased (11.3 %, 33.3 %, and 87.5 % in groups 1, 2, and 3, respectively; P < 0.001). Individuals with preablation Tg levels ≥10 ng/ml had 25.5 times greater chance of therapeutic failure than those with levels <10 ng/ml (95 % CI = 5.43-119.60; P < 0.001).

CONCLUSIONS

A high preablation Tg level is the most significant predictor of therapeutic failure at the time of first HI-Rx in patients with PTC.

Effect of Post-Reconstruction Gaussian Filtering on Image Quality and Myocardial Blood Flow Measurement with N-13 Ammonia PET

OBJECTIVES

In order to evaluate the effect of post-reconstruction Gaussian filtering on image quality and myocardial blood flow (MBF) measurement by dynamic N-13 ammonia positron emission tomography (PET), we compared various reconstruction and filtering methods with image characteristics.

METHODS

Dynamic PET images of three patients with coronary artery disease (male-female ratio of 2:1; age: 57, 53, and 76 years) were reconstructed, using filtered back projection (FBP) and ordered subset expectation maximization (OSEM) methods. OSEM reconstruction consisted of OSEM_2I, OSEM_4I, and OSEM_6I with 2, 4, and 6 iterations, respectively. The images, reconstructed and filtered by Gaussian filters of 5, 10, and 15 mm, were obtained, as well as non-filtered images. Visual analysis of image quality (IQ) was performed using a 3-grade scoring system by 2 independent readers, blinded to the reconstruction and filtering methods of stress images. Then, signal-to-noise ratio (SNR) was calculated by noise and contrast recovery (CR). Stress and rest MBF and coronary flow reserve (CFR) were obtained for each method. IQ scores, stress and rest MBF, and CFR were compared between the methods, using Chi-square and Kruskal-Wallis tests.

RESULTS

In the visual analysis, IQ was significantly higher by 10 mm Gaussian filtering, compared to other sizes of filter (P<0.001 for both readers). However, no significant difference of IQ was found between FBP and various numbers of iteration in OSEM (P=0.923 and 0.855 for readers 1 and 2, respectively). SNR was significantly higher in 10 mm Gaussian filter. There was a significant difference in stress and rest MBF between several vascular territories. However CFR was not significantly different according to various filtering methods.

CONCLUSION

Post-reconstruction Gaussian filtering with a filter size of 10 mm significantly enhances the IQ of N-13 ammonia PET-CT, without changing the results of CFR calculation.

Intratumoral Metabolic Heterogeneity for Prediction of Disease Progression After Concurrent Chemoradiotherapy in Patients with Inoperable Stage III Non-Small-Cell Lung Cancer

PURPOSE

We evaluated the value of variable (18)F-FDG PET/CT parameters for the prediction of disease progression after concurrent chemoradiotherapy (CCRT) in patients with inoperable stage III non-small-cell lung cancer (NSCLC).

METHODS

One hundred sixteen pretreatment FDG PET/CT scans of inoperable stage III NSCLC were retrospectively reviewed (stage IIIA: 51; stage IIIB: 65). The volume of interest was automatically drawn for each primary lung tumor, and PET parameters were assessed as follows: maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV) using the boundaries presenting SUV intensity exceeding 3.0, and the area under the curve of the cumulative SUV-volume histograms (AUC-CSH), which is known to reflect the tumor heterogeneity. Progression-free survival (PFS), locoregional recurrence-free survival (LRFS), and distant metastasis-free survival (DMFS) were compared with each PET and clinical parameters by univariate and multivariate survival analysis.

RESULTS

In the ROC analysis, the optimal cutoff values of SUVmax, MTV (cm(3)), and AUC-CSH for prediction of PFS were determined as 21.5, 27.7, and 4,800, respectively. In univariate analysis, PFS was statistically significantly reduced in those with AUC-CSH < 4,800 (p = 0.004). In multivariate analysis, AUC-CSH and SUVmax were statistically significant independent prognostic factors (HR 3.35, 95 % CI 1.79-6.28, p < 0.001; HR 0.25, 95 % CI 0.09-0.70, p = 0.008, respectively). Multivariate analysis showed that AUC-CSH was the most significant independent prognostic factor for LRFS and DMFS (HR 3.27, 95 % CI 1.54-6.94, p = 0.002; HR 2.79, 95 % CI 1.42-5.50, p = 0.003).

CONCLUSIONS

Intratumoral metabolic heterogeneity of primary lung tumor in (18)F-FDG PET/CT can predict disease progression after CCRT in inoperable stage III NSCLC.

Indirect Radionuclide Coronary Angiography to Evaluate Gradients of Myocardial Blood Flow and Flow Reserve Through Coronary Stenosis Using N-13 Ammonia PET/CT

Although quantitative evaluation of myocardial blood flow (MBF) and myocardial flow reserve (MFR) has been perceived as an attractive advantage of positron emission tomography (PET) over other cardiac imaging technologies, application of the information to specific coronary lesions is a difficult task for nuclear cardiologists. We hypothesized that changes in MBF and MFR over a coronary lesion could be identified by use of a hybrid technology of CT coronary angiography (CTCA) and N-13 ammonia PET. To evaluate this hypothesis, we measured the gradient of MBF and MFR through coronary stenosis in seven patients (M:F=3:4, median age 56 years) with coronary artery disease who underwent N-13 ammonia PET, CTCA, and interventional coronary angiography. Two patients had proximal left anterior descending (LAD) coronary artery disease and five patients had mid to distal LAD disease. Mean global stress and rest MBF were 2.62±0.58 and 1.03±0.19 ml/min/g, respectively. Mean global MFR was 2.6±0.73. Regional stress and rest MBF in the LAD territory were 2.36±0.75 and 0.96±0.21 ml/min/g, respectively. Regional MFR in the LAD territory was 2.55±0.83 ml/min/g. Stress MBF changed dramatically according to the location of coronary stenosis. It dropped acutely in proximal lesions, whereas it diminished gradually in mid to distal lesions. In conclusion, by use of a hybrid technology of CTCA and PET, it was feasible to make a direct correlation of coronary lesions with the gradient of MFR and CFR through coronary stenosis, which indicated the severity of the coronary lesion. We named this technique indirect radionuclide coronary angiography.