Diagnosis of Fungal Infection (Candida albicans) After Heart Transplantation in a Pediatric Case with Fever of Unknown Origin: Role of 99mTc‑UBI SPECT/CT and 18F‑FDG PET/CT / 대한핵의학회잡지

The diagnosis of patients with fever of unknown origin (FUO) in pediatric heart transplantation is a challenging medical problem. The physician should differentiate between rejections, infections, malignancy, adrenal insufficiency, and drug fever. Immunosuppressive therapy in these patients exposes them to a high risk of developing a post-transplantation fungal infection. In this case, we discuss the diagnostic contribution of the 99mTc-UBI scan and 18F-FDG PET scan for diagnosis of fungal infection causing FUO in these patients.

Extensive Venous Tumor Thrombi in a Case of Malignant Melanoma: Role of 18F FDG PET/CT / 대한핵의학회잡지

The 18F-FDG PET/CT imaging is a non-invasive modality for diagnosis and staging of metastatic melanoma. Venous thromboembolism (VTE) is a common complication of cancers, which needs anticoagulant therapy. Tumor thrombosis (TT), on the other hand, is an infrequent complication of solid malignancies that may need aggressive management. Accurate diagnosis of TT and its differentiation from VTE may change patient management and avoid unnecessary anticoagulation treatment. The objective of this case is to introduce a patient with malignant melanoma presenting with extensive venous tumor thrombi with intense FDG uptake.

Diagnostic accuracy assessment of ST-segment displacements, chest pain and stress myocardial perfusion imaging exercise test in coronary stenosis compared with angiography findings

Nowadays, myocardial perfusion imaging [MPI] plays an important role in the early diagnosis of patients with coronary artery disease [CAD]. This study sought to assess the performance of MPI alongside chest paint and ST-segment changes during the stress test by comparison with angiography in the diagnosis of coronary artery stenosis. To that end, the accuracy of these modalities in terms of sensitivity and specificity and the degree of greement between their results in the diagnosis of coronary artery stenosis were evaluated. The study population, selected from those with known or suspected CAD, was comprised of 85 patients [67 males] at a mean age of 53.7 +/- 9.6 years. All the patients were subjected to SPECT imaging of the blood supply to the heart muscle during a two-day state of stress [either pharmacologically with Dipyridamole or through exercise test] and during rest via the injection of 99m Tc - MIBI. ST-segment changes during stress as well as clinical symptoms were recorded. All the patients underwent coronary angiography within two weeks, and coronary artery stenosis >50% was considered positive. Finally, the results of chest pain, ECG changes, and MPI for the evaluation of coronary artery involvement were compared with those of angiography as the gold standard. Of the 85 patients, who underwent angiography, 10 patients had normal coronary angiography, 22 single-vessel disease, 28 two-vessel disease, and 25 three-vessel disease. ST- segment depression and ST-segment elevation were observed in 40 and 6 patients, respectively. The ECG had sensitivity of 57% and specificity of 70% in the diagnosis of coronary artery stenosis. Fifteen patients had chest pain during stress; all of them had coronary involvement according to angiography. Of the 70 patients with no chest pain, coronary angiography was positive in 62 cases; accordingly, chest pain had sensitivity of 20% and specificity of 100% in the diagnosis of coronary artery stenosis. There were 80 patients with abnormal MPI, including 387 fixed and reversible defects. Therefore, MPI had sensitivity of 79%, specificity of 70%, and diagnostic accuracy of 76% in the diagnosis of coronary artery stenosis. MPI enjoyed higher diagnostic accuracy and agreement coefficient than did chest pain and ST-segment changes in the diagnosis of coronary artery stenosis. Given the acceptable results of MPI in the diagnosis of coronary artery stenosis, this modality could be valuable in the management of CAD patients

Respiratory Motion Detection and Correction in ECG-Gated SPECT: a New Approach

OBJECTIVE: Gated myocardial perfusion single-photon emission computed tomography (GSPECT) has been established as an accurate and reproducible diagnostic and prognostic technique for the assessment of myocardial perfusion and function. Respiratory motion is among the major factors that may affect the quality of myocardial perfusion imaging (MPI) and consequently the accuracy of the examination. In this study, we have proposed a new approach for the tracking of respiratory motion and the correction of unwanted respiratory motion by the use of respiratory-cardiac gated-SPECT (RC-GSPECT). In addition, we have evaluated the use of RC-GSPECT for quantitative and visual assessment of myocardial perfusion and function. MATERIALS AND METHODS: Twenty-six patients with known or suspected coronary artery disease (CAD)-underwent two-day stress and rest (99m)Tc-Tetrofosmin myocardial scintigraphy using both conventional GSPECT and RC-GSPECT methods. The respiratory signals were induced by use of a CT real-time position management (RPM) respiratory gating interface. A PIO-D144 card, which is transistor-transistor logic (TTL) compatible, was used as the input interface for simultaneous detection of both ECG and respiration signals. RESULTS: A total of 26 patients with known or suspected CAD were examined in this study. Stress and rest myocardial respiratory motion in the vertical direction was 8.8-16.6 mm (mean, 12.4 +/- 2.9 mm) and 7.8-11.8 mm (mean, 9.5 +/- 1.6 mm), respectively. The percentages of tracer intensity in the inferior, inferoseptal and septal walls as well as the inferior to lateral (I/L) uptake ratio was significantly higher with the use of RC-GSPECT as compared to the use of GSPECT (p < 0.01). In a left ventricular ejection fraction (LVEF) correlation analysis between the use of rest GSPECT and RC-GSPECT with echocardiography, better correlation was noted between RC-GSPECT and echocardiography as compared with the use of GSPECT (y = 0.9654x + 1.6514; r = 0.93, p < 0.001 versus y = 0.8046x + 5.1704; r = 0.89, p < 0.001). Nineteen (19/26) patients (73.1%) showed abnormal myocardial perfusion scans with reversible regional myocardial defects; of the 19 patients, 14 (14/26) patients underwent coronary angiography. CONCLUSION: Respiratory induced motion can be successfully corrected simultaneously with the use of ECG-gated SPECT in MPI studies using this proposed technique. Moreover, the use of ECG-gated SPECT improved image quality, especially in the inferior and septal regions that are mostly affected by diaphragmatic attenuation. However, the effect of respiratory correction depends mainly on the patient respiratory pattern and may be clinically relevant in certain cases.

[Energy window setting for optimum Tl-201 cardiac imaging]

Poor sensitivity and poor signal to noise ratio because of low injected thallium dose and presence of scattered photons are the main problems in using thallium in scintigraphic imaging of the heart. Scattered photons are the main cause of degrading the contrast and resolution in SPECT imaging that result in error in quantification. Thallium decay is very complicated and photons are emitted in a wide range of energies of 68-82 keV. It seems possible to achieve better primary to scattered radiation ratio and better image sensitivity simultaneously if the energy window setting is carefully selected. This investigation was performed in three steps: Monte Carlo simulation, phantom experiment and clinical study. In simulation step, the new 4D digital NCAT phantom was used to simulate the distribution of activity [201Tl] in patient torso organs. The same phantom was used to simulate the attenuation coefficient of different organs of the typical patient's body. Two small defects on different parts of left ventricle also were generated for further quantitative and qualitative analysis. The simulations were performed using the SimSET simulator to generate images of such patient. The emissions arising from Tl-201 decay were simulated in four steps using the energies and relative abundances. Energy spectra for primary and scatter photons were calculated. Changing the center and width of energy windows, optimum energy window characteristics were determined. In next step jaszczak phantom was prepared and used for SPECT imaging in different energy windows. In last step SPECT images of 7 patients who had angiographic data were acquired in different energy windows. All of these images were compared qualitatively by four nuclear medicine physicians independently. The optimum energy window was determined as a wider asymmetric window [77keV?30%] that its center is not placed on photo-peak of energy spectrum. This window increased the primary counts rate and PTSR considerably as compared with the conventional symmetric energy window [67keV%]. In a comparison which performed between clinical images acquired in suggested 77-30% window with conventional 67-20% window, a considerable increase was found in myocardial to defect contrast [1.541 +/- 0.368] and myocardial to cavity contrast [1.171 +/- 0.099]. A negligible increase was also found in total counts of images using this window. We found that conventional symmetric energy window [67keV +/- 10%] couldn't be a suitable choice for thallium heart imaging; furthermore three energy windows, 73keV-30%, 75keV-30% and 77keV-30%, were determined as optimum window options. For further analysis the images from such windows were compared in each three steps of this investigation. In all steps conventional symmetric energy window [67keV-20%] was introduced as the worst case and the asymmetric 77keV-30% was determined as the most suitable