Human ; Radionuclide Imaging ; Nuclear Medicine

BACKGROUND: Coronary microcirculation impairment with sequential decrease in cardiac function is reflected by abnormal left ventricular ejection fraction reserve (LVEFR),which precedes diagnostic evidence of myocardial insult. However, prognostic utility of LVEFR is less, if not least explored. The aim of this study was to evaluate the clinical utility of LVEFR in predicting major cardiac events (MACE) among patients with and suspected coronary artery disease (CAD).
MATERIALS AND METHODS: A retrospective cohort study of 245 patients who underwent stress thallium-201 myocardial perfusion scan (MPS) was conducted. The patients were categorized as having normal or abnormal perfusion scan. Each group was subdivided into normal and abnormal LVEFR groups. All subjects were followed up for any major adverse cardiac events 36 months after MPS through review of hospital records.
RESULTS: There was an overall increase in the likelihood of cardiac events with abnormal LVEFR (i.e., odds ratio of 2.99,p=<0.01). Majority of subjects with abnormal MPS also had abnormal LVEFR showing a significantly lower mean LVEFR (1.17± 7.30 vs. 3.02 ± 7.36p =<0.01).
CONCLUSION: Abnormal LVEFR can be used as an independent predictor of cardiac events which can be observed in subjects with normal and abnormal perfusion scans alike.

Human ; Male ; Female ; Middle Aged ; Adult ; Coronary Artery Disease ; Thallium ; Omega-chloroacetophenone ; Microcirculation ; Stroke Volume ; Heart ; Thallium Radioisotopes ; Myocardium ; Perfusion Imaging

BACKGROUND: Coronary microcirculation impairment with sequential decrease in cardiac function is reflected by abnormal left ventricular ejection fraction reserve (LVEFR),which precedes diagnostic evidence of myocardial insult. However, prognostic utility of LVEFR is less, if not least explored. The aim of this study was to evaluate the clinical utility of LVEFR in predicting major cardiac events (MACE) among patients with and suspected coronary artery disease (CAD).
MATERIALS AND METHODS: A retrospective cohort study of 245 patients who underwent stress thallium-201 myocardial perfusion scan (MPS) was conducted. The patients were categorized as having normal or abnormal perfusion scan. Each group was subdivided into normal and abnormal LVEFR groups. All subjects were followed up for any major adverse cardiac events 36 months after MPS through review of hospital records.
RESULTS: There was an overall increase in the likelihood of cardiac events with abnormal LVEFR (i.e., odds ratio of 2.99,p=<0.01). Majority of subjects with abnormal MPS also had abnormal LVEFR showing a significantly lower mean LVEFR (1.17± 7.30 vs. 3.02 ± 7.36p =<0.01).
CONCLUSION: Abnormal LVEFR can be used as an independent predictor of cardiac events which can be observed in subjects with normal and abnormal perfusion scans alike.

Human ; Male ; Female ; Middle Aged ; Adult ; Coronary Artery Disease ; Thallium ; Omega-chloroacetophenone ; Microcirculation ; Stroke Volume ; Heart ; Thallium Radioisotopes ; Myocardium ; Perfusion Imaging

BACKGROUND: Blunting of coronary flow reserve (CFR) may precede overt ischemia. The study aimed to correlate CFR with perfusion findings and risk factors for coronary artery disease (CAD).
METHODS: Fifty-four consecutive patients underwent dipyridamole-rest technetium-99m sestamibi single photon emission computed tomography (SPECT) on two separate days. CFR was computed as the quotient of myocardial blood flow (MBF= global tissue perfusion divided by arterial input function) at stress and at rest.
RESULTS: CFR was significantly lower in patients with abnormal perfusion vs normals (p=0.005). Reduced CFR was noted in 83% of patients with normal SPECT. Lower CFR was seen in hypertensive patients with left ventricular hypertrophy (LVH) compared to those without LVH (p=0.029); likewise in DM vs no DM (p=0.121). Independent predictors of reduced CFR were age and extent of ischemia.
CONCLUSION: Abnormal perfusion is associated with reduced CFR. In those with normal perfusion, there is a high prevalence of reduced CFR, which may be attributed to the presence of risk factors for CAD and LVH.

Human ; Male ; Female ; Arteries ; Coronary Artery Disease ; Dipyridamole ; Hypertrophy, Left Ventricular ; Risk Factors ; Technetium Tc 99m Sestamibi ; Tomography, Emission-computed, Single-photon

Patients with LV dysfunction are known to have a high risk for future coronary events. This study aimed to determine the incremental prognostic value of perfusion defects in patients with scintigraphic evidence of LV dysfunction. Patients showing either transient ischemic dilatation or Tl-201 lung:heart ratio of >0.5 on exercise or dipyridamole SPECT Tl- 201 myocardial perfusion scan were included in the study. Perfusion defects were scored semiquantitatively using a 17 -segment, 5-point scale (0 = normal, 4 = absent uptake). The extent and severity of defects were quantified using number of abnormal segments (NAS) and the summed stress score (SSS). Defect reversibility was quantified using the summed difference score (SDS) between stress and rest defects. Patients were followed up for the development of coronary events over a period of 12 - 30 months. There were 6 cardiac deaths and 7 myocardial infarctions in the 65 patients included in the study (20% overall event rate). ROC curve analysis of the scores revealed the following suggested cut-off values for predicting cardiac event: NAS ~ 7 (85% sensitivity, 56% specificity), SSS ~ 19 (77% sensitivity, 67% specificity) and SDS ~ 7 (31 % sensitivity, 60% specificity). ,Event rate was significantly higher above the cut-off value in SSS «19 = 9%, >19 = 32%,p = 0.04). With NAS, the event rate was higher above the cut-off value, with the difference approaching significance (NAS 7 = 26%, P = 0.06). There was no statistically significant difference in the event rate with high or low SDS (SDS 7 = 16%, P = 0.32). The odds ratios for NAS and SSS (5.8,4.9, respectively) were higher compared with SDS (0.56). The extent and severity of stress perfusion defects provided incremental prognostic information in patients with LV dysfunction. Our data suggest that the degree of defect reversibility showed no prognostic value in this subset of patients.

Human ; Male ; Female ; Aged ; Middle Aged ; Adult ; Dilatation ; Dipyridamole ; Myocardial Infarction ; Tomography, Emission-computed, Single-photon ; Myocardial Perfusion Imaging ; Thallium ; Radionuclide Imaging ; Diagnosis ; Cardiac Imaging Techniques

Left ventricular mass (LV mass) is an independent prognostic indicator of cardiovascular complications, and its regression due to therapy translates to positive clinical outcomes. Good correlation of LV mass between qualitative ECG-gated SPECT (OGS) and echocardiography has been reported, and this study aims to verify if such relationship applies in the local setting. Forty-five consecutive patients with normal myocardial perfusion SPECT and recent plain echocardiograms done in the same institution were retrospectively analyzed. Results show a significant correlation (y = 0.296x + 75.962, r = 0.491, p = 0.001) between the LV mass of the two imaging modalities, which was also observed in the TI-201  group (y= 0.256x + 80.325, r_=_0.442, p = 0.006), but not in the Tc-99m sestamibi group (y= 0.402x + 63.456, r_=_0.443, p = 0.272). The mean LV mass by OGS (122.0 ± 26.9) is significantly smaller compared with the mean LV mass by echo cardiography (155.5 ± 44.6), and the difference between the two procedures (mean ± SD: 39.7 ± 32.6, p<0.001) are significantly different among all subiects, and in the TI-201 and Tc-99m sestamibi groups. In conclusion, the LV mass generated by OGS correlates with echocardiographic estimations, but are statistically different, with OGS significantly underestimating the echo cardiographic values. Age, sex and BMI do not influence the LV mass discrepancy between the two imaging modalities, but the presence of soft tissue attenuation artifacts tend to decrease the LV mass generated by OGS, contributing to further LV mass disparity.

Human ; Male ; Female ; Aged ; Middle Aged ; Artifacts ; Body Mass Index ; Echocardiography ; Electrocardiography ; Heart Diseases ; Retrospective Studies ; Technetium Tc 99m Sestamibi ; Tomography, Emission-computed, Single-photon

BACKGROUND/OBJECTIVE: Direct measurement of gland uptake function is done by determining radioactive iodine uptake (RAID) values. Scintigraphic parameters in 99mTc0-4 thyroid scan have been shown to be moderately correlated with FT4 levels. This study aims to correlate these scintigrahic parameters with RAIU values and determine the cutoff that will predict increased gland uptake function.
METHODOLOGY: Patients referred for thyroid scan and RAI uptake at the Philippine Heart Center were included in the study. RAW. values were correlated with thyroid salivary gland ratio, thyroid to background ratio, thyroid count and acquision time. These values were obtained by drawing appropriate regions of interest in the thyroid, salivary gland and the background.
RESULTS: The four parameters were strongly correlated with RAI uptake values. The cut-off for the thyroid salivary gland ratio, thyroid to background ratio, total thyroid count and acquisition time that best predicts increased gland uptake were > 9.3, > 9.8, > 108134 counts, and < 203 seconds, respectively.
CONCLUSION: The four scrim/graphic parameters can be used in determining the activity of the gland using thyroid imaging alone in the absence of RA1U values.

Human ; Male ; Female ; Aged ; Middle Aged ; Adult ; Thyroid Gland ; Iodine ; Salivary Glands ; Viscera

OBJECTIVES: Impairment of coronary flow reserve (CFR) precedes preclinical atherosclerosis. However, data are lacking regarding its prognostic utility using SPECT imaging. Thus, this study aimed to determine the clinical utility of CFR by sestamibi imaging in predicting future cardiac events in patients with normal and abnormal myocardial perfusion scan (MPS).

METHODS: This was a prospective cohort study of 54 consecutive adult patients with suspected coronary artery disease referred to Nuclear Medicine Division, Philippine Heart Center for dipyridamole technetium-99m sestamibi SPECT MPS from August 2012 to September 2013. Patients with normal (summed stress score, SSS <3) and abnormal (SSS> 4) perfusion scans were further subdivided based on their CFR whether normal (CFR> 2) or abnormal (CFR < 2). Using a validated 2-day protocol, estimated CFR was computed from the ratio of dipyridamole myocardial blood flow (MBE) to resting MBF. MBF was obtained by dividing the global myocardial counts with the arterial input function. Global myocardial counts were derived from the average of the mean counts/pixel of two representative short-axis tomograms at the mediobasal and medioapical views. For the arterial input function, first-pass analysis of the pulmonary artery was performed to generate the time-activity curve (TAC). The mean counts/pixel of the area under the curve represented the input junction. Patients were monitored for major adverse cardiac events (MACE) through phone contact by patient and by review of hospital and physician's record six months after scintigraphy (mean follow-up 9+3 months). Major cardiac events include cardiac death, acute coronary syndrome, unstable angina, and revascularization.

RESULTS: A prospective cohort of 54 consecutive patients with no known CAD, were enrolled in the study. Abnormal MPI revealed significantly lower CFR (1.64 + 0.47 vs. 1.19 + 0.36, p=0.005). The annual cardiac event rate increased in the presence of reduced CFR in spite of a normal MPI (from 0% to 6.9%), and was even higher when both MPI and CFR were abnormal (from 0% to 34.7%). In Kaplan-Meier analysis, patients with abnormal perfusion revealed-significantly higher incidence of cardiac events compared with normal perfusion (chi-square 4.93, p=0.027). There was a trend towards increased incidence of cardiac events in patients with abnormal CFR; however, this did not reach statistical significance (chi-square 0.61, p=0.434).

CONCLUSION: A low CFR was associated with an increased incidence of MACE, particularly in the presence of abnormal perfusion findings.

Human ; Male ; Female ; Adult ; Technetium Tc 99m Sestamibi ; Dipyridamole ; Acute Coronary Syndrome ; Kaplan-meier Estimate ; Heart ; Angina, Unstable ; Myocardium

BACKGROUND: Serum thyroglobulin assays and I-131 imaging and routinely employed for the detection of remaining functioning thyroid tissue after surgery and radioiodine therapy. However, the sensitivity of I-131 is suboptimal resulting in cases of positive thyroglobulin test but negative I-131 imaging, potentially creating a dilemma in subsequent therapeutic management. Other radiopharmaceuticals, such as TI-201 may offer better sensitivity, although it is not clear whether this contributes to the decision-making for subsequent I-131therapy. This prospective cohort study aimed to determine if Tl-201 imaging identified thyroid tissues that will take up therapeutic I-131, and to help define its clinical utility.
METHODS: Fourteen consecutive patients who underwent surgery for well-differentiated thyroid cancer, had I-131 therapy at least eight months previously, and with elevated thyroglobulin (>10 ng/mL) but negative pre-therapy (111 MBq) I-131 whole body scan (WBS), were enrolled in the study. WBS was done using 56.74 MBq of Tl-201. All patients had repeat I-131 ablation (3.7-7.4GBq) one to two months after Tl-201 imaging. Post-therapy WBS was done four to seven days after.
RESULTS: All 14 patients had papillary thyroid carcinoma. Ten patients had a positive Tl-201 scan. Of the 14 subjects, only two had a positive post-therapy I-131 WBS, both whom had a positive Tl-201 scan. Thallium-201 scanning showed a fairly high sensitivity (71%) in demonstrating thyroid remnants or metastases using a thyroglobulin level of >10 ng/mL as standard. However, a positivel Tl-201 scan only has a predictive value of 20% for subsequent uptake of therapeutic I-131 as shown in the post-therapy scan.
CONCLUSION: Thallium-201 uptake correlates poorly with therapeutic I-131 uptake in thyroglobulin-positive, but I-131 scan-negative, differentiated thyroid cancer patients. Results of this study suggest that the presence of thyroid remnants and metastases on Tl-201 imaging is inappropriate as a basis for subsequent I-131 therapy.

Human ; Male ; Female ; Middle Aged ; Adult ; Thyroglobulin ; Thyroid Cancer, Papillary ; Radiopharmaceuticals ; Iodine Radioisotopes ; Thallium ; Thyroid Neoplasms ; Carcinoma ; Neoplasms, Second Primary ; Thallium Radioisotopes

INTRODUCTION: Patients with well-differentiated thyroid carcinoma (WDTC) may require more than one session of radioactive iodine therapy (RAIT). This study was conducted to determine if post-therapy whole body scintigraphy (PTWBS) can identify patients who will require repeat RAIT due to persistent disease.

METHOD: The records of patients with WDTC who were referred to the Philippine General Hospital for RAIT from 2005-2007 were reviewed in this retrospective cohort study. PTWBS results (number of remnants, area of remnants, and presence of metastasis) of patients who had repeat RAIT (based on laboratory and clinical evidence of persistent disease) were compared with those of patients who did not have repeat RAIT. Multiple logistic regression analysis was done.

RESULTS: Forty-five of 99 patients in the study [45%, 95% Confidence Interval (CI): 35 had repeat RAIT. Thirty-six of 38 patients (95%) with metastases on PTWBS required repeat RAIT, while only 9 of 61 patients (15%) with no scan evidence of metastases required subsequent therapy. Controlling for age group (age), the odds ratio was 102 (95% CI: 20 . Positive and negative predictive values were 95 and 85% respectively. The same results were obtained using metastases alone as a predictor. Twenty-six patients had extra-cervical metastases by PTWBS and all required repeat RAIT. The number and aggregate size of thyroid remnants by PTWBS, however, were not found to be predictive of the need for repeat therapy.

CONCLUSION: The presence of functioning metastases seen on PTWBS was highly predictive of the need for repeat RAIT.

Human ; Male ; Female ; Middle Aged ; Adult ; Hospitals, General ; Philippines ; Whole Body Imaging ; Thyroid Neoplasms ; Carcinoma ; Radionuclide Imaging ; Iodine