• The Korean Journal of Nuclear Medicine
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• v.38 no.6
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• pp.486-491
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• 2004

Purpose: factor analysis and independent component analysis (ICA) has been used for handling dynamic image sequences. Theoretical advantages of a newly suggested ICA method, ensemble ICA, leaded us to consider applying this method to the analysis of dynamic myocardial $H_2^{15}O$ PET data. In this study, we quantified patients' blood flow using the ensemble ICA method. Materials and Methods: Twenty subjects underwent $H_2^{15}O$ PET scans using ECAT EXACT 47 scanner and myocardial perfusion SPECT using Vertex scanner. After transmission scanning, dynamic emission scans were initiated simultaneously with the injection of $555{\sim}740$ MBq $H_2^{15}O$. Hidden independent components can be extracted from the observed mixed data (PET image) by means of ICA algorithms. Ensemble learning is a variational Bayesian method that provides an analytical approximation to the parameter posterior using a tractable distribution. Variational approximation forms a lower bound on the ensemble likelihood and the maximization of the lower bound is achieved through minimizing the Kullback-Leibler divergence between the true posterior and the variational posterior. In this study, posterior pdf was approximated by a rectified Gaussian distribution to incorporate non-negativity constraint, which is suitable to dynamic images in nuclear medicine. Blood flow was measured in 9 regions - apex, four areas in mid wall, and four areas in base wall. Myocardial perfusion SPECT score and angiography results were compared with the regional blood flow. Results: Major cardiac components were separated successfully by the ensemble ICA method and blood flow could be estimated in 15 among 20 patients. Mean myocardial blood flow was $1.2{\pm}0.40$ ml/min/g in rest, $1.85{\pm}1.12$ ml/min/g in stress state. Blood flow values obtained by an operator in two different occasion were highly correlated (r=0.99). In myocardium component image, the image contrast between left ventricle and myocardium was 1:2.7 in average. Perfusion reserve was significantly different between the regions with and without stenosis detected by the coronary angiography (P<0.01). In 66 segment with stenosis confirmed by angiography, the segments with reversible perfusion decrease in perfusion SPECT showed lower perfusion reserve values in $H_2^{15}O$ PET. Conclusions: Myocardial blood flow could be estimated using an ICA method with ensemble learning. We suggest that the ensemble ICA incorporating non-negative constraint is a feasible method to handle dynamic image sequence obtained by the nuclear medicine techniques.

• Nuclear Medicine and Molecular Imaging
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• v.41 no.3
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• pp.252-254
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• 2007

Image fusion is fast catching attention as Wagner pointed out in his 2006 version of the recent progress and development presented at the annual meeting of Society of Nuclear Medicine. Prototypical fusion of bone scan and radiograph was already attempted at in 1961 when Fleming et al. published an article on strontium-85 bone scan. They simply superimposed dot scan on radiograph enabling simultaneous assessment of altered bone metabolism and local bone anatomy. Indeed the parallel reading of images of bone scan and radiography, CT, MRI or ultrasonography has been practiced in nuclear medicine long since. It is fortunate that recent development of computer science and technology along with the availability of refined CT and SPECT machines has permitted us to open a new avenue to digitally produce precise fusion image so that they can readily be read, exchanged and disseminated using internet. Ten years ago fusion was performed using Bresstrahlung SPECT/CT and it is now achievable by PET/CT and SPECT/CT software and SPECT/CT hardware. The merit of image fusion is its feasibility of reliable assessment of morphological and metabolic change. It is now applicable not only to stationary organs such as brain and skeleton but also to moving organs such as the heart, lung and stomach. Recently, we could create useful fusion image of cardiac SPECT and 64-channel CT angiograph. The former provided myocardial metabolic profile and the latter vascular narrowing in two patients with coronary artery stenosis and myocardial ischemia. Arterial stenosis was severe in Case 1 and mild in Case 2.

• The Korean Journal of Nuclear Medicine
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• v.31 no.1
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• pp.73-82
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• 1997

Regional myocardial blood flow (rMBF) can be noninvasively quantified using N-13 ammonia and dynamic positron emission tomography (PET). The quantitative accuracy of the rMBF values, however, is affected by the distortion of myocardial PET images caused by finite PET image resolution and cardiac motion. Although different methods have been developed to correct the distortion typically classified as partial volume effect and spillover, the methods are too complex to employ in a routine clinical environment. We have developed a refined method incorporating a geometric model of the volume representation of a region-of-interest (ROI) into the two-compartment N-13 ammonia model. In the refined model, partial volume effect and spillover are conveniently corrected by an additional parameter in the mathematical model. To examine the accuracy of this approach, studies were performed in 9 coronary artery disease patients. Dynamic transaxial images (16 frames) were acquired with a GE $Advance^{TM}$ PET scanner simultaneous with intravenous injection of 20 mCi N-13 ammonia. rMBF was examined at rest and during pharmacologically (dipyridamole) induced coronary hyperemia. Three sectorial myocardium (septum, anterior wall and lateral wall) and blood pool time-activity curves were generated using dynamic images from manually drawn ROIs. The accuracy of rMBF values estimated by the refined method was examined by comparing to the values estimated using the conventional two-compartment model without partial volume effect correction rMBF values obtained by the refined method linearly correlated with rMBF values obtained by the conventional method (108 myocardial segments, correlation coefficient (r)=0.88). Additionally, underestimated rMBF values by the conventional method due to partial volume effect were corrected by theoretically predicted amount in the refined method (slope(m)=1.57). Spillover fraction estimated by the two methods agreed well (r=1.00, m=0.98). In conclusion, accurate rMBF values can be efficiently quantified by the refined method incorporating myocardium geometric information into the two-compartment model using N-13 ammonia and PET.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.5 no.2
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• pp.71-78
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• 2019

Nuclear imaging is one of the most powerful measures for non-invasive diagnosis of myocardial vascular disease. Radionuclide such as ¹³N, ¹⁵O, ²⁰¹Tl and ⁸²Rb is used for the measurement of cardiac blood flow. ¹³N, ¹⁵O and ²⁰¹Tl are produced in cyclotrons while ⁸²Rb is obtained from generator. Rubidium (Rb), an alkali ion, behaves biologically like potassium, and accumulates in myocardial tissue. Rb has rapid blood clearance profile which allows the use of ⁸²Rb with a short physical half-life of 75 s for non-invasive evaluation of regional myocardial perfusion. There are several advantages of ⁸²Rb over other radioisotopes. An ultra-short half-life significantly reduces the exposure of patients to radiation and allows to repeat injections for studying the effects of medical intervention. As a positron emitter, ⁸²Rb allows positron emission tomography (PET) imaging which have shown superior diagnostic performances. ⁸²Rb can be produced from generator by decay of its parent ⁸²Sr. However, the preparation of ⁸²Sr is difficult, because appropriate purity is required to meet the specification of the product. Recently reported procedure from ARRONAX research institute showed that a Chelex-100 resin is sufficient for this purpose and additional column is not necessary. Whereas Brookhaven National Laboratory (BNL) procedure contains three ion exchange resin separation, including Chelex-100 resin. Currently, since ⁸²Sr production site is non-existent in Korea, Korea Atomic Energy Research Institute (KAERI) has plan to produce ⁸²Sr within specifications. We compared ⁸²Sr purification procedures reported from ARRONAX and BNL to investigate the most suitable procedure for our conditions.

• Proceedings of the Korea Multimedia Society Conference
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• 2012.05a
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• pp.462-463
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• 2012

팍스시스템은 의료 영상을 디지탈화한 시스템이다. PACS데이터는 초창기 CR(Computed Radiography)의 경우 10MB내외의 데이터를 발생하였으나 의료장비의 발전으로 인해 DB(Digital Radiography)는 20MB이상의 데이터를 발생하였다. 또 CT(Computed Tomography)의 경우 0.5MB데이터를 100Slice내외의 데이터를 발생하였으나, 현재는 Cardiac/PET 등의 CT는 Multi Frame을 지원하며 300~5000Slice이상의 데이터를 발생하게 됨에 따라 네트워크에 상당한 트래픽이 발생하여 병원 진료 환경에 심각한 영향을 초래한다. 또한, 스마트 폰, 태블릿 pc등의 발전으로 인해 많은 사용자들은 실시간 또는 멀티미디어와 같은 데이터 표현 방식으로 팍스 데이터를 보길 원할 것이며, 팍스 시스템 또한 그러한 요구조건을 만족시키기 위해 발전하고 있다. 병원에서 사용하는 네트워크는 인터넷 서비스의 모토인 best effort방법을 일반적으로 사용한다. 이러한 데이터 전송방식은 진료에 직접적인 영향을 미치는 팍스 데이터의 전송에 영향을 미칠 수 있다. 특히 네트워크의 트래픽이 제한적인 환경에서 높은 대역폭을 요구하는 멀티미디어 팍스 데이터를 다수의 사용자들이 전송받기 원하면 지연시간으로 인해 원활한 진료진행을 방해 받을 수 있다. 이러한 문제를 해결하기 위해 네트워크 개발자들은 QoS라는 개념을 도입하였고, 여러 계층에서 QoS를 보장하기 위한 연구가 진행되였다. 일반적으로, 네트워크에서 QoS를 지원하기 위한 여러가지 형태의 연구들을 조사하고, 분산 시스템을 제어하기 위한 DDS 미들웨어에 대한 연구를 기반으로 병원 네트워크에서 적용 방안을 설계하고 시뮬레이션을 통해 검증함으로써 새로운 형태의 병원 네트워크를 제안하고자 한다.

• The Korean Journal of Nuclear Medicine Technology
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• v.14 no.1
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• pp.67-72
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• 2010

Purpose: In Asan Medical Center we perform myocardial perfusion SPECT to evaluate cardiac event risk level for non-cardiac surgery patients. In case of patients with cancer, we check tumor metastasis using whole body bone scan and whole body PET scan and then perform myocardial perfusion SPECT to reduce unnecessary exam. In case of short term in patients, we perform $^{201}Tl$ myocardial perfusion SPECT after whole body bone scan a minimum 16 hours in order to reduce hospitalization period but it is still the actual condition in which the evaluation about the affect of the crosstalk contamination due to the each other dissimilar isotope administration doesn't properly realize. So in our experiments, we try to evaluate crosstalk contamination influence on $^{201}Tl$ myocardial perfusion SPECT using anthropomorphic torso phantom and patient's data. Materials and Methods: From 2009 August to September, we analyzed 87 patients with $^{201}Tl$ myocardial perfusion SPECT. According to $^{201}Tl$ myocardial perfusion SPECT yesterday whole body bone scan possibility of carrying out, a patient was classified. The image data are obtained by using the dual energy window in $^{201}Tl$ myocardial perfusion SPECT. We analyzed $^{201}Tl$ and $^{99m}Tc$ counts ratio in each patients groups obtained image data. We utilized anthropomorphic torso phantom in our experiment and administrated $^{201}Tl$ 14.8 MBq (0.4 mCi) at myocardium and $^{99m}Tc$ 44.4 MBq (1.2 mCi) at extracardiac region. We obtained image by $^{201}Tl$ myocardial perfusion SPECT without gate method application and analyzed spatial resolution using Xeleris ver 2.0551. Results: In case of $^{201}Tl$ window and the counts rate comparison result yesterday whole body bone scan of being counted in $^{99m}Tc$ window, the difference in which a rate to 24 hours exponential-functionally notes in 1:0.114 with Ventri (GE Healthcare, Wisconsin, USA), 1:0.249 after the bone tracer injection in 12 hours in 1:0.411 with 1:0.79 with Infinia (GE healthcare, Wisconsin, USA) according to a reduction a time-out was shown (Ventri p=0.001, Infinia p=0.001). Moreover, the rate of the case in which it doesn't perform the whole body bone scan showed up as the average 1:$0.067{\pm}0.6$ of Ventri, and 1:$0.063{\pm}0.7$ of Infinia. According to the phantom after experiment spatial resolution measurement result, and an addition or no and time-out of $^{99m}Tc$ administrated, it doesn't note any change of FWHM (p=0.134). Conclusion: Through the experiments using anthropomorphic torso phantom and patients data, we found that $^{201}Tl$ myocardium perfusion SPECT image later carried out after the bone tracer injection with 16 hours this confirmed that it doesn't receive notable influence in spatial resolution by $^{99m}Tc$. But this investigation is only aimed to image quality, so it needs more investigation in patient's radiation dose and exam accuracy and precision. The exact guideline presentation about the exam interval should be made of the validation test which is exact and in which it is standardized about the affect of the crosstalk contamination according to the isotope use in which it is different later on.

• The Korean Journal of Nuclear Medicine
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• v.27 no.2
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• pp.155-160
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• 1993

The identification of viable myocardium in patients with coronary artery disease and left ventricular dysfunction is an issue of increasing clinical relavance in the current era of myocardial revascularization. There are at least two forms of reversible myocardial dysfunction. Early reperfusion does not always lead to immediate functional improvement; rather, the return of contractility in tissue salvaged by reperfusion is delayed for hours, days or even weeks, a phenomenon that has been termed "stunned myocardium". Some patients with coronary artery disease show myocardial dysfunction at rest which are associated with reduced perfusion, and which disappear after revascularization; this phenomenon has been termed "hibernating myocardium". Recently, cardiac imaging techniques that evaluate myocardial viability on the basis of perfusion-contraction mismatch and inotropic reserve have gained substantial popularity and clinical success. This review focus on the application of $^{201}TI$ and $^{99m}Tc-MIBI$ to address myocardial viability in patients with hibernating and stunned myocardium. It is clear that 4-hour redistribution images of $^{201}TI$ underestimate ischemia and overestimate scar. Delayed imaging and reinjection imaging have been developed for the assessment of viability. Among many protocols suggested, stress-redistribution-reinjection imaging gained most popularity. Although $^{99m}Tc-MIBI$ could identify myocardial viability, $^{201}TI$ reinjection technique was regarded as superior to it. In conclusion, $^{201}TI$ stress, 4-hr rest redistribution, and reinjection imaging technique may be the most preferable method for evaluation of myocardial viability.

• Journal of Veterinary Clinics
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• v.26 no.3
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• pp.212-219
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• 2009

Anticholinergics, which are commonly given as a pre-anesthetic medication to prevent adverse effects in canine anesthesia, can cause cardiac adverse effects. To determine the effects of atropine and glycopyrrolate on the balance of sympathetic nervous tone and parasympathetic nervous tone of the heart during ketamine anesthesia in beagle dogs, heart rate variability(HRV), duration of anesthesia and behavioral changes were evaluated. There were no significant temporal domain differences between atropine and glycopyrrolate. Concerning the frequency domain component, atropine and glycopyrrolate effects were significantly lower(P<0.05) than the control saline-treated group. However, the root mean square of the interval differences between consecutive R peaks(RMSSD) and the standard deviation of Poincare plot perpendicular to the line-of-identity(SD1) in atropine were significantly decreased(P<0.05) from the baseline value, and the low frequency/high frequency ratio(LF:HF ratio) in glycopyrrolate was significantly increased from baseline value(P<0.05). The change of SD1 agreed with that of the high frequency(HF) in the frequency domain component and also with those of respiratory rate and $SpO_2-R$. Our results prove that glycopyrrolate is more suitable as a pre-anesthetic anticholinergic in ketamine anesthesia of dogs with respect to safety and duration of action.