Optimization of 201Tl Dosage in a Simultaneous Acquisition Rest 99mTc/Stress 201Tl Dual-Isotope Myocardial Perfusion Single-Photon Emission Computed Tomography with Semiconductor Gamma Camera.

Background: The use of 201Tl in myocardial perfusion single-photon emission computed tomography (SPECT) is predominantly not recommended because of the higher radiation exposure of 201Tl compared to 99mTc agent. However, the advent of new gamma cameras with semiconductor detectors has made it possible to reduce the 201Tl dose and lower radiation exposure. In our hospital, the dose of 201Tl is adjusted according to the patient's body mass index (BMI), with 50 MBq for BMI<25 and 74 MBq for BMI≥25. The dose of 201Tl during simultaneous acquisition dual-isotope myocardial perfusion SPECT (MPS; stress 201Tl and rest 99mTc agent) exceeds 9 mSv/examination when 74 MBq of 201Tl is administered. In order to further reduce the radiation dose, optimization of the 201Tl dose was investigated. Methods: Two hundred and eighty consecutive patients who underwent stress MPS using simultaneous acquisition dual-isotope protocol (SDI protocol) for the estimation of ischemic heart disease were included. Patients with prior myocardial infarction were excluded. Correlations between BMI and acquisition time were determined in patients receiving 50 MBq (n=154) or 74 MBq (n=126) of 201Tl. In addition, linear regression analysis was used to determine the slope and intercept to derive a linear functional equation, and the theoretically optimal 201Tl dose was evaluated. Results: The correlation coefficient between BMI and acquisition time in the 201Tl 50 MBq group was 0.532 (P< 0.00001) and in the 201Tl 74 MBq group was 0.478 (P<0.00001), both showing a positive correlation. Linear regression analysis yielded two equations: y=0.52x-0.32 (201Tl 50 MBq group) and y=0.41x-0.69 (201Tl 74 MBq group). Linear function equation results indicated that patients with BMI between 25 and 30 could be examined within approximately 15 minutes with 50 MBq of 201Tl. Conclusion: Considering examination efficiency, a single acquisition time of less than 15 minutes is ideal. Theoretically, patients with BMI less than 30 could be examined within approximately 15 minutes with 50 MBq of 201Tl.

Effect of Atorvastatin on Microcirculation Evaluated by Vascular Occlusion Test with Peripheral Near-Infrared Spectroscopy.

The vascular occlusion test (VOT) with peripheral near-infrared spectroscopy (NIRS) is a non-invasive method to evaluate peripheral microcirculation. Statin therapy is widely used for patients with dyslipidaemia and contributes to reducing low-density lipoprotein cholesterol (LDL-C) levels and adverse cardiovascular events. However, it is not yet clear whether statin treatment improves peripheral microcirculation assessed by VOT with NIRS. In the present study, using VOT with NIRS, we evaluated the effect of statin therapy on peripheral microcirculation in patients with dyslipidaemia before and after statin therapy. METHODS: A total of six consecutive patients with dyslipidaemia who had not received statin therapy (6 males, mean age 71.8 ± 7.4 years) were enrolled. All patients were administered atorvastatin and their peripheral microcirculation assessed using VOT with NIRS (NIRO-200NX, Hamamatsu Photonics K.K., Japan) before and after statin therapy. The NIRS probe was attached to the right thenar eminence and brachial artery blood flow was blocked for 3 min at 50 mmHg above the resting systolic blood pressure. Maximum and minimum values of NIRS parameters after the VOT were used to determine concentration changes for total haemoglobin (ΔcHb), oxyhaemoglobin (ΔO2Hb), deoxyhaemoglobin (ΔHHb), and tissue oxygenation index (ΔTOI). RESULTS: During the follow-up period (mean 30.3 ± 6.5 days), LDL-C level decreased from 129.7 ± 26.3 to 67.5 ± 20.2 mg/dL (p-value = 0.031), ΔTOI increased from 24.0 ± 5.3 to 33.7 ± 6.3% (p-value = 0.023), and ΔO2Hb increased from 16.4 ± 5.3 to 20.0 ± 6.6 µmol/L (p-value = 0.007). ΔcHb and ΔHHb did not change significantly. CONCLUSION: ΔO2Hb and ΔTOI were significantly increased during the follow-up period. These findings suggest that ΔO2Hb and ΔTOI could assess the improvement of peripheral microcirculation by statin therapy. Compared to ΔTOI, ΔO2Hb seems to be a more useful parameter to evaluate peripheral microcirculation.

Clinical Validation of Japanese Normal Myocardial Perfusion Imaging Databases Using Semi-conductor Gamma Camera (D-SPECT): Japanese Society of Nuclear Cardiology Working Group Reports.

Objective: A working group (WG) of the Japanese Society of Nuclear Cardiology (JSNC) determined Japanese normal databases of myocardial perfusion single-photon emission computed tomography (SPECT) on semi-conductor gamma camera (D-SPECT), and the aim of this study was to validate its clinical utility. Materials and methods: The normal myocardial perfusion SPECT (MPS) databases of Japanese patients in the 201Tl stress/redistribution protocol (201Tl protocol), 99mTc stress/rest or rest/stress protocol (99mTc protocol), and rest 99mTc/stress 201Tl simultaneous acquisition dual-isotope protocol (SDI protocol) were created by JSNC WG. The WG collected clinical cases for the 201Tl protocol (male/female [m/f], 8/8), 99mTc protocol (m/f, 9/7), and SDI protocol (m/f, 10/10) from WG participating hospitals. Four WG members read those clinical cases on a 17-segment and 5-point scale (0-4). Using the most frequent values as the score for each segment, weighted κ values were calculated with the scores obtained from quantitative perfusion software (QPS). Results: Weighted κ values were as follows; 201Tl stress/female, 0.77; 201Tl rest/female, 0.74; 201Tl stress/male, 0.81; 201Tl rest/male, 0.68; 99mTc stress/female, 0.77; 99mTc rest/female, 0.62; 99mTc stress/male, 0.77; 99mTc rest/male, 0.75; SDI stress/female, 0.87; SDI rest/female, 0.82; SDI stress/male, 0.87; SDI rest/male, 0.85. Conclusions: The diagnostic accuracy of Japanese MPS normal databases on D-SPECT were comparable with nuclear cardiology expert reading and further clinical applications are expected.

Relationship Among Coronary Artery Calcium Score, Myocardial Perfusion SPECT and Risk Stratification of Coronary Artery Disease.

Since Agatston et al. first reported quantification of the coronary artery calcification score (CACS) in 1990, discussion of its clinical significance and use in diagnostic management has continued. Recent papers have reported the relationship between CACS and myocardial perfusion single photon emission computed tomography (SPECT: MPS) and its combined diagnostic value. When interpreting CACS results, it should be noted that the frequency of significant ischemia detected by MPS, likelihood of coronary artery disease (CAD), and event rate gradually increased from mild to moderate CACS (1-400). At present, high CACS is considered to be moderately consistent with abnormal MPS, and abnormal CACS in normal MPS may contribute to CAD risk stratification. However, it should be noted that CACS=0 does not completely exclude CAD, which is particularly important when using CACS as a gatekeeper for MPS. Both stand-alone computed tomography (CT) scanner and hybrid SPECT-CT scanner are available for combined risk stratification of CACS and MPS in addition to improvement of image quality with attenuation correction.

Clinical Utility of a Slow 201Tl Washout Rate in the Detection of Multi-Vessel Coronary Artery Disease Using a Simultaneous Acquisition Rest 99 mTc/Stress 201Tl Protocol and a Semiconducting Gamma Camera.

BACKGROUND: The diagnostic accuracy of stress myocardial perfusion single-photon emission computed tomography (SPECT) to detect coronary artery disease (CAD) is reduced by the balanced reduction of myocardial perfusion in patients with multi-vessel or left main trunk CAD (multi-vessel group). This study investigated the diagnostic performance of a simultaneous acquisition rest 99 mTc/stress 201Tl dual-isotope protocol for myocardial perfusion SPECT (MPS) in a multi-vessel group by examining the assessment of a slow 201Tl washout rate (WR) finding in comparison to the accuracy of perfusion assessments.Methods and Results: This study enrolled 91 patients who had undergone angiography within 3 months after MPS. The diagnostic performances of perfusion assessments and a slow 201Tl WR parameter were compared using the area under the curve (AUC) in a multi-vessel group of patients with mild ischemia (2≤summed difference score [SDS]≤7). The AUC of a slow WR parameter was significantly larger compared with that for perfusion assessments, in patients with mild ischemia, (AUC, 0.736 vs. 0.504-0.558, P value: <0.01-0.05). CONCLUSIONS: Among patients with mild ischemia, a slow 201Tl WR parameter improved the detection of CAD in a multi-vessel group.

Venovenous extracorporeal membrane oxygenation for acute respiratory distress syndrome due to an acute type B aortic dissection: a case report.

Acute type B aortic dissection is sometimes complicated by acute respiratory failure requiring mechanical ventilation. Herein, we describe our experience in a rare acute type B aortic dissection-associated respiratory failure case culminating in acute respiratory distress syndrome. The patient was a 45-year-old man admitted with a complaint of sudden chest pain radiating to his back. On computed tomography, an acute type B aortic dissection was diagnosed. He had no dyspnea on admission, but his respiratory function subsequently deteriorated, and severe acute respiratory distress syndrome was diagnosed on Day 4. Venovenous extracorporeal membrane oxygenation with anticoagulation plus continuous renal replacement therapy for oliguria improved the oxygenation, and the patient was weaned from the extracorporeal membrane oxygenation on Day 8. This patient fully recovered without worsening the aortic dissection, using venovenous extracorporeal membrane oxygenation with anticoagulation plus a continuous renal replacement therapy.

Application of Peripheral Near Infrared Spectroscopy to Assess Risk Factors in Patient with Coronary Artery Disease: Part 1.

Obesity, a risk factor of coronary artery disease, is known to cause peripheral microcirculatory disturbances. This study evaluated the relationship between the degree of obesity and peripheral microcirculatory disturbances, using peripheral near infrared spectroscopy (NIRS) with a vascular occlusion test (VOT). We compared correlations between the NIRS parameter changes induced by VOT and body mass index (BMI) in patients with and without statin therapy. A NIRS probe was set on the right thenar eminence, brachial artery blood flow was blocked for 3 min, and then released. Although total hemoglobin (ΔcHb), deoxyhemoglobin (ΔHHb) and tissue oxygenation index (ΔTOI) were not correlated with BMI, a significant negative correlation was found between oxyhemoglobin (ΔO2Hb) and BMI in the overall study population (r = -0.255, p-value 0.02). In addition, a significant negative correlation was found between ΔO2Hb and BMI in patients without statin therapy (r = -0.353, p-value 0.02) but not in patients with statin therapy (r = -0.181, p-value 0.27). These findings suggest that ΔO2Hb may be a useful indicator to assess peripheral microcirculation.

Application of Peripheral Near Infrared Spectroscopy to Assess Risk Factors in Patient with Coronary Artery Disease: Part 2.

Epicardial adipose tissue (EAT) is associated with visceral fat and various cardiac disorders, such as atrial fibrillation and adverse cardiovascular events. Therefore, it is important to develop a simple and non-invasive inspection method to assess EAT, to prevent unfavorable cardiac events. This study assessed correlations between near-infrared spectroscopy (NIRS) changes induced by a vascular occlusion test (VOT) and EAT volume measured by cardiac computed tomography (CCT) in patients with suspected coronary artery disease. We also assessed correlations between body mass index (BMI) and EAT volume in the same population. In addition, these correlations were compared in patients treated with statin therapy and in those without statin therapy. A NIRS probe was set on the right thenar eminence, and brachial artery blood flow was blocked for 3 min before being released. A negative correlation was found between oxyhemoglobin (ΔO2Hb) and EAT volume in the overall study population (r = -0.236, p = 0.03). Interestingly, although a strong correlation was observed in patients without statin therapy (r = -0.488, p < 0.001), this correlation was not observed in patients with statin therapy (r = 0.157, p = 0.34). These findings suggest that NIRS measurements with VOT may be a useful method to identify patients with high EAT volume and high cardiovascular risks.