Guang-Uei Hung

Value of delayed 18F-FDG-PET imaging in the detection of hepatocellular carcinoma.

Background18F-Fluorodeoxyglucose-positron emission tomography (18F-FDG-PET) is a very useful imaging technique and is the best modality for the evaluation of many kinds of tumour. However, in the evaluation of hepatocellular carcinoma (HCC), the diagnostic accuracy of routine 60 min static imaging is not satisfactory. Some authors have suggested that delayed 2 h imaging is a better 18F-FDG-PET protocol for tumour detection. However, the value of delayed 3 h imaging has not been clarified. In this study, we performed delayed 2 h and 3 h imaging on patients with HCC and compared their diagnostic accuracy with standard 60 min imaging. MethodsTwelve patients with HCC were enrolled in this study. Of these 12 patients, four had not been treated and eight had received transcatheter arterial embolization (TAE) therapy for more than 4 months before the PET study. One hour after injection of 18F-FDG, a whole-body scan was performed. In addition, delayed imaging focusing on the liver was also performed 2 h and 3 h after the injection. The standard uptake value (SUV) was calculated for the tumours in each image. ResultsThe twelve patients had 16 HCCs. Of the 16 HCCs, nine were detected by 18F-FDG-PET scans based on the 1 h images, whereas 10 HCCs were detected based on the 2 or 3 h images. The diagnostic sensitivity increased from 56.3% on the 1 h image to 62.5% on the 2 and 3 h images. In addition, the mean SUV increased from 3.63 at 1 h to 3.86 at 2 h and 3.99 at 3 h after the injection of 18F-FDG. On the other hand, the mean SUV in the normal liver tissue decreased slightly from 2.38 at 1 h to 2.33 at 2 h and 2.31 at 3 h. The tumour to normal liver tissue (T/N) ratio increased from 1.56 at 1 h to 1.68 at 2 h and 1.75 at 3 h. ConclusionIn the evaluation of HCC, delayed 2 and 3 h imaging can detect more lesions than standard 1 h imaging. Imaging at 3 h has a better T/N ratio than imaging at 2 h, but does not increase the diagnostic sensitivity.

SPECT myocardial blood flow quantitation toward clinical use: a comparative study with 13N-Ammonia PET myocardial blood flow quantitation

ObjectivesThe aim of this study was to evaluate the accuracy of myocardial blood flow (MBF) quantitation of 99mTc-Sestamibi (MIBI) single photon emission computed tomography (SPECT) compared with 13N-Ammonia (NH3) position emission tomography (PET) on the same cohorts.BackgroundRecent advances of SPECT technologies have been applied to develop MBF quantitation as a promising tool to diagnose coronary artery disease (CAD) for areas where PET MBF quantitation is not available. However, whether the SPECT approach can achieve the same level of accuracy as the PET approach for clinical use still needs further investigations.MethodsTwelve healthy volunteers (HVT) and 16 clinical patients with CAD received both MIBI SPECT and NH3 PET flow scans. Dynamic SPECT images acquired with high temporary resolution were fully corrected for physical factors and processed to quantify K1 using the standard compartmental modeling. Human MIBI tracer extraction fraction (EF) was determined by comparing MIBI K1 and NH3 flow on the HVT group and then used to convert flow values from K1 for all subjects. MIBI and NH3 flow values were systematically compared to validate the SPECT approach.ResultsThe human MIBI EF was determined as [1.0-0.816*exp(−0.267/MBF)]. Global and regional MBF and myocardial flow reserve (MFR) of MIBI SPECT and NH3 PET were highly correlated for all subjects (global R2: MBF = 0.92, MFR = 0.78; regional R2: MBF ≥ 0.88, MFR ≥ 0.71). No significant differences for rest flow, stress flow, and MFR between these two approaches were observed (All p ≥ 0.088). Bland-Altman plots overall revealed small bias between MIBI SPECT and NH3 PET (global: ΔMBF = −0.03Lml/min/g, ΔMFR = 0.07; regional: ΔMBF = −0.07 − 0.06 , ΔMFR = −0.02 − 0.22).ConclusionsQuantitation with SPECT technologies can be accurate to measure myocardial blood flow as PET quantitation while comprehensive imaging factors of SPECT to derive the variability between these two approaches were fully addressed and corrected.

Left-ventricular dyssynchrony evaluated by Tl-201 gated SPECT myocardial perfusion imaging: a comparison with Tc-99m sestamibi

Background and purposePhase analysis of gated single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) has been validated as a reliable tool to assess left-ventricular (LV) mechanical dyssynchrony. The initial results were all confirmed from studies using technetium-99m (Tc-99m) sestamibi or tetrofosmin as the radiotracers. The purpose of this study was to evaluate the feasibility of phase analysis in thallium-201 (Tl-201) gated SPECT MPI. Materials and methodsSeventeen patients referred from a cardiology clinic for evaluation of coronary artery disease were studied. All patients underwent both Tl-201 and Tc-99m sestamibi gated SPECT MPI within 1 week. An additional 34 patients with Tl-201 gated SPECT and 22 patients with Tc-99m sestamibi gated SPECT, who had a low likelihood of coronary artery disease, normal LV function, and normal perfusion on MPI, were used as normal controls. LV dyssynchrony parameters, including phase standard deviation (PSD) and phase histogram bandwidth (PHB), were measured using a standard phase analysis tool and compared between Tl-201 and Tc-99m sestamibi images. ResultsThe LV dyssynchrony parameters correlated well (r=0.93 for PSD and r=0.84 for PHB) between Tl-201 and Tc-99m sestamibi images. The dyssynchrony parameters of Tl-201 were significantly larger than those of Tc-99m sestamibi (PSD: 24.5±12.0 vs. 17.4±9.7, P<0.001; PHB: 74.7±35.5 vs. 50.6±25.0, P<0.001). In comparison with normal controls, Tl-201 and Tc-99m sestamibi images showed concordant results. ConclusionLV dyssynchrony parameters correlated well between Tl-201 and Tc-99m sestamibi images, even though the values were significantly larger for Tl-201 than for Tc-99m sestamibi. Tl-201 images showed results similar to those of Tc-99m sestamibi in the diagnosis of LV dyssynchrony.

Impact of right-ventricular apical pacing on the optimal left-ventricular lead positions measured by phase analysis of SPECT myocardial perfusion imaging

PurposeThe use of SPECT phase analysis to optimize left-ventricular (LV) lead positions for cardiac resynchronization therapy (CRT) was performed at baseline, but CRT works as simultaneous right ventricular (RV) and LV pacing. The aim of this study was to assess the impact of RV apical (RVA) pacing on optimal LV lead positions measured by SPECT phase analysis.MethodsThis study prospectively enrolled 46 patients. Two SPECT myocardial perfusion scans were acquired under sinus rhythm with complete left bundle branch block and RVA pacing, respectively, following a single injection of 99mTc-sestamibi. LV dyssynchrony parameters and optimal LV lead positions were measured by the phase analysis technique and then compared between the two scans.ResultsThe LV dyssynchrony parameters were significantly larger with RVA pacing than with sinus rhythm (p ~0.01). In 39 of the 46 patients, the optimal LV lead positions were the same between RVA pacing and sinus rhythm (kappa = 0.861). In 6 of the remaining 7 patients, the optimal LV lead positions were along the same radial direction, but RVA pacing shifted the optimal LV lead positions toward the base.ConclusionThe optimal LV lead positions measured by SPECT phase analysis were consistent, no matter whether the SPECT images were acquired under sinus rhythm or RVA pacing. In some patients, RVA pacing shifted the optimal LV lead positions toward the base. This study supports the use of baseline SPECT myocardial perfusion imaging to optimize LV lead positions to increase CRT efficacy.

Ictal and interictal 99mTc-HMPAO brain SPECT of a MELAS case presented with epilepsy-like visual hallucination.

A 55-year-old woman was diagnosed with the syndrome of mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). She was referred for Tc-HMPAO brain SPECT because of visual hallucinations, which were suspected to be related to epileptic seizures. Ictal SPECT images showed remarkable hyperperfusion in the left occipital cortex, which returned to near-normal status on the interictal SPECT images after treatment with anticonvulsants. It is very rare to see such an ictal SPECT image of epileptic or epilepsy-like disorders, especially in the setting of MELAS syndrome with visual hallucination.

LV Dyssynchrony Is Helpful in Predicting Ventricular Arrhythmia in Ischemic Cardiomyopathy After Cardiac Resynchronization Therapy: A Preliminary Study.

AbstractFor patients with coronary artery disease, larger scar burdens are associated with higher risk of ventricular arrhythmia. Left ventricular (LV) dyssynchrony is associated with increased risk of sudden cardiac death in patients with heart failure. The purpose of this study was to assess the values of LV dyssynchrony and myocardial scar assessed by myocardial perfusion SPECT (MPS) in predicting the development of ventricular arrhythmia in ischemic cardiomyopathy.Twenty-two patients (16 males, mean age: 66 ± 13) with irreversible ischemic cardiomyopathy received cardiac resynchronization therapy (CRT) for at least 12 months were enrolled for MPS. Quantitative parameters, including LV dyssynchrony with phase standard deviation (phase SD) and bandwidth, left ventricular ejection fraction (LVEF), and scar (% of total areas), were generated by Emory Cardiac Toolbox. Ventricular tachycardia (VT) and ventricular fibrillation (VF) recorded in the CRT device during follow-up were used as the reference standard of diagnosing ventricular arrhythmia. Stepwise logistic regression analysis was performed for determining the independent predictors of VT/VF and receiver operating characteristic (ROC) curve analysis was used for generating the optimal cut-off values for predicting VT/VF.Nine (41%) of the 22 patients developed VT/VF during the follow-up periods. Patients with VT/VF had significantly lower LVEF, larger scar, larger phase SD, and larger bandwidth (all P < 0.05). Logistic regression analysis showed LVEF and bandwidth were independent predictors of VT/VF. ROC curve analysis showed the areas under the curves were 0.71 and 0.83 for LVEF and bandwidth, respectively. The optimal cut-off values were <36% and > 139° for LVEF and bandwidth, respectively. The sensitivity, specificity, positive predictive value, and negative predictive value were 100%, 39%, 53%, and 100%, respectively, for LVEF; and were 78%, 92%, 88%, and 86%, respectively, for bandwidth.LV dyssynchrony as assessed by phase analysis of MPS is helpful for predicting ventricular arrhythmia in ischemic cardiomyopathy after CRT. Further implantation of defibrillator may be considered for those patients with bandwidth >139°.

New Trends in Radionuclide Myocardial Perfusion Imaging

UNLABELLED Radionuclide myocardial perfusion imaging (MPI) with single photon emission computed tomography (SPECT) has been widely used clinically as one of the major functional imaging modalities for patients with coronary artery disease (CAD) for decades. Ample evidence has supported the use of MPI as a useful and important tool in the diagnosis, risk stratification and treatment planning for CAD. Although popular in the United States, MPI has become the most frequently used imaging modality among all nuclear medicine tests in Taiwan. However, it should be acknowledged that MPI SPECT does have its limitations. These include false-positive results due to certain artifacts, false-negative due to balanced ischemia, complexity and adverse reaction arising from current pharmacological stressors, time consuming nature of the imaging procedure, no blood flow quantitation and relatively high radiation exposure. The purpose of this article was to review the recent trends in nuclear cardiology, including the utilization of positron emission tomography (PET) for MPI, new stressor, new SPECT camera with higher resolution and higher sensitivity, dynamic SPECT protocol for blood flow quantitation, new software of phase analysis for evaluation of LV dyssynchrony, and measures utilized for reducing radiation exposure of MPI. KEY WORDS Coronary artery disease • Myocardial flow reserve • Myocardial perfusion imaging • Phase analysis • PET • SPECT.

Reducing renal uptake of111In-DOTATOC: A comparison among various basic amino acids

Purpose: Several studies have reported significant renal toxicity after the use of a high dose of90Y-DOTATOC. Thus, renal protection is necessary in treatments with90Y-DOTA Tyr3-octroetide (DOTATOC). The infusion of certain positively charged amino acids has been shown to effectively reduce renal uptake of DOTATOC. In this study, we compared the effectiveness of three kinds of amino acids, D-lysine (lysine),L-arginine (arginine) and histidine, on renal protection in healthy rats and tried to determine which one was the most effective.Methods: Twenty SD healthy male rats were divided into 4 groups: lysine, histidine, arginine, and control. The rats were injected with a dose of 400 mg/kg of amono acid or 2 ml of phosphate-buffered saline (PBS) (as control) intraperitoneally. All rats were sacrificed at 4 hrs after the injection of 1 MBq111In-DOTATOC. Samples of the kidney were taken and weighed carefully. The counts of radioactivity were measured by a gamma counter and renal concentrations were calculated and expressed as percent injected dose per gram (% ID/g).Results: The renal uptake of111In-DOTATOC was significantly lower for all three kinds of amino acids when compared to the control group. The renal uptake of111In-DOTATOC in the lysine group was significantly lower than those in the histidine and arginine groups. The renal uptake of111In-DOTATOC in the histidine group was lower than that in the arginine group, but no statistical difference was noted.Conclusion: Among these three amino acids, lysine had the best reduction rate of renal uptake of DOTATOC. Histidine was more effective than arginine but no statistical difference was noted.

Asymptomatic port-site metastasis following video-assisted thoracoscopic surgery detected by FDG-PET/CT.

We reported a 59-year-old man who had been treated for a rectal adenocarcinoma in May 2005 and also received wedge resection of a solitary metastasis in the left upper lung by video-assisted thoracoscopic surgery (VATS) in September 2008. He underwent FDG-PET/CT scanning in August 2009 due to elevating tumor markers. An FDG-avid lesion was found in the muscles of the left lateral chest wall. Physical examination revealed a palpable nodule just beneath the port-site of VATS. Excisional biopsy confirmed this lesion to be metastatic adenocarcinoma of colorectal origin, considered secondary to tumor cell implantation during previous VATS excision of a metastasis.

Faster radioiodine washout in the treatment of pulmonary metastases of papillary thyroid cancer prepared with recombinant human thyroid-stimulating hormone.

Abstract:Although recombinant human thyroid-stimulating hormone (rhTSH) has been approved officially as an adjunct to the diagnostic approach of thyroid cancer and ablation of thyroid remnants, its application in treatment of persistent or metastatic disease is still under investigation. We present