Association of hemodynamic changes with the scan parameters of a dipyridamole-induced stress Myocardial Perfusion Scintigraphy with Technetium-99m Sestamibi in patients with suspected coronary artery disease

Introduction@#A dipyridamole induced stress myocardial perfusion scintigraphy with Tc-99m Sestamibi is utilized for diagnosing coronary artery diseases. The use of dipyridamole as form of pharmacologic stressor has expected hemodynamic changes. @*Objective@#The objective of this study was to determine the association of these changes with the scan parameters in patients with suspected coronary artery disease (CAD). @*Methodology@#A total of 101 patients, with suspected CAD, who underwent a dipyridamole-induced stress myocardial perfusion scintigraphy using Tc-99m Sestamibi from January 2019 to March 2020 were included in this study. The patient databases, monitoring sheets, and scan results were reviewed .@*Results@#The blood pressure responses had no significant association with the scan parameters and results. The normal (> 1.2) and abnormal (<1.2) heart rate ratios (HRR), which is the peak HR/baseline HR, likewise had no significant association with the scan results. However, in terms of the median HRR, the higher ratio of 1.29 (normal scan results) against the ratio of 1.25 (abnormal scan results) was determined to be significant (p-value of 0.032). The HRR also had a direct and indirect weak correlation with stress and rest Left Ventricular Ejection Fraction (LVEF) values (p-values of 0.09 and 0.011) and Summed Rest Score (p-value of 0.007), respectively. For the 12-L ECG, only the baseline normal (P-value of 0.018) and infarct findings (p-value of 0.017) were similarly associated with normal and abnormal scan results, respectively.@*Conclusion@#For patients with suspected CAD, the higher HRRs and baseline 12-L ECG of normal and infarct findings relates to the expected scan result. For scan parameters, the higher HRRs were also correlated with higher stress and rest LVEF values, and normal SRS, albeit a weak correlation. Notably, the blood pressure and post-infusion 12-L ECG changes had no significant association. In summary, the higher HRRs indicates normal scan results, normal SRS, and better LVEF values which increases the diagnostic confidence in the interpretation and management, especially in some equivocal cases.

Cost-effectiveness analysis of well-differentiated thyroid carcinoma surveillance using nuclear medicine procedures

Introduction@#Well-differentiated thyroid carcinoma (WDTC) is the most common type of thyroid cancer with a notable increasing incidence worldwide. It is prevalent among Filipino descent as compared to other nationalities. Its good prognosis and high survival rate predispose patients to lifetime surveillance with incomplete response, instead of death, as outcome measure. This eventually leads to increase in cost of care, utilization, and allocation of medical resources for the survivors of the disease. Thyroglobulin immunoradiometric assay (Tg IRMA) and I-131 diagnostic whole-body scan (dWBS) are two nuclear medicine procedures that are part of WDTC surveillance. Due to their varied availability in Asia-Pacific, most clinicians measure thyroglobulin (Tg) alone due to perceived cost-effectiveness. @*Objective@#This study aims to analyze the cost-effectiveness of two nuclear medicine procedures used in WDTC surveillance, namely thyroglobulin immunoradiometric assay and I-131 diagnostic whole-body scan, in detecting incomplete response. @*Methodology@#Three clinical guidelines on WDTC management were reviewed to identify frequency, total number and expenditure for surveillance, namely from the University of the Philippines-Philippine General Hospital in 2008 (PGH 2008), American Thyroid Association in 2015 (ATA 2015), and the Department of Health (DOH 2021). A Markov model was constructed to simulate a 36-month surveillance with complete and incomplete response to treatment as disease states. Parameter values like rate of incomplete response in WDTC patients, prognostic values per each surveillance test, and other relevant data were collected from literature search and established data. The cost of surveillance was based on the rates offered by Philippine General Hospital (PGH) Radioisotope Laboratory as of November 2022. One-way sensitivity was done to check robustness of results. @*Results@#ATA 2015 incurs the most expenses, amounting to PHP 14,600.00 to 20,450.00 ($ 254.19 – 356.04) for three years of surveillance, followed by DOH 2021 (PHP 11,700.00 – 15,600.00 or $ 203.74 – 271.65), and PGH 2008 (PHP 3,900.00 – 6,825.00 or $ 67.91 – 118.85). The thyroglobulin IRMA arm costs lower (PHP 17,784.00 or $ 309.74) than I-131 dWBS (PHP 271,875.00 or $ 4,735.13) in detecting incomplete response. I-131 dWBS should cost around PHP 570.00 (or $ 9.92) to be as cost-effective as the thyroglobulin IRMA.@*Conclusion@#This study has identified that thyroglobulin IRMA is more cost-effective than I-131 diagnostic whole-body scan in detecting incomplete response in WDTC patients. This supports the perceived cost-effectiveness of thyroglobulin measurement in surveillance, even without diagnostic whole body-scans. This study also identified that the new DOH 2021 guidelines will incur lesser expenditure in using nuclear medicine procedures for surveillance as compared to ATA 2015 guidelines. Local clinicians may also find it easier to follow as it is more suitable to the Philippine setting.

Comparison of image quality, diagnostic accuracy, and LV parameters in filtered backprojection versus iterative SPECT Reconstruction in Myocardial Perfusion Scintigraphy

Background@#Myocardial perfusion scintigraphy images with iterative reconstruction showed higher qualitative and quantitative estimates. @*Objective@#This study was conducted to compare image quality, diagnostic accuracy, and LV parameters with standard FBP versus OSEM as baseline quality assurance for the choice of reconstruction algorithm most applicable in the local setting. @*Methods@#This was a retrospective cross-sectional study of 55 Thallium-201 (Tl-201) scans and 14 Techentium-99m sestamibi (Tc-99m) images that were reprocessed with filtered backprojection (FBP) and with ordered subset expectation maximization (OSEM). The image quality, diagnostic accuracy, and LV parameters of both SPECT reconstructions were compared.@*Results@#OSEM reconstruction resulted in a significantly smooth background tracer activity as opposed to the standard FBP in both Tl-201 (p<0.01) and Tc-99m (p=0.01) scans. Distinct LV border was superiorly seen in OSEM. There was no significant difference in the diagnostic accuracy between the two reconstruction parameters despite 2 cases of interpretation discrepancies. End-diastolic volume generated by OSEM was significantly higher (117.60+55.14 vs 118.51+55.11, p<0.01 in Tl-201 and 101.07+75.58 vs 104.29+80.39, p =0.01 in Tc-99m). With Tc-99m scans the end-systolic volume and ejection fraction in OSEM were likewise significantly different from FBP (p=0.04 and p<0.01, respectively).@*Conclusion@#OSEM reconstruction offers smooth background tracer activity with comparable diagnostic accuracy to FBP. All the LV parameters in OSEM were significantly different from FBP in Tc-99m scans and only the EDV in thallium images.

Correlation of fat mass with bone mineral density and FRAX-based fracture risk among postmenopausal Filipino women

Background@#Post-menopausal women experiences changes in estrogen levels affecting body metabolism, which may lead to weight gain and obesity. Moreover, one of the most prevalent diseases among this group is osteoporosis. However, the relationship between fat mass and its protective property remains unclear. This study assesses the correlation of fat mass with bone mineral density (BM) and 10-year FRAX based fracture probability among Filipino women.@*Methods@#A cross-sectional review of records of post-menopausal Filipino women who underwent whole body bone mineral densitometry scans via dual-energy X-ray absorptiometry (DXA) between January 1, 2015, and December 31, 2018 in the Radioisotope Laboratory of the Philippine General Hospital was done. Pearson correlation and simple linear regression analyses were done to determine the correlation between the two outcomes – BMD and 10-year FRAX based fracture probability. @*Results@#A total of 258 postmenopausal women were included in the analysis. There was a weak positive correlation of fat mass with BMD of L1-L4 vertebrae (R-score of 0.318), BMD of femoral neck (R-score of 0.3937) and hips (R - score of 0.3031). The 10-year FRAX based fracture probability for both hip and osteoporotic had very weak and weak negative correlation, respectively (R-score of - 0.06752 and - 0.29017). @*Conclusion@#Despite having varying available, data on the protective effects of fat mass on fracture protection, this study showed that fat mass has a poor correlation with BMD and reduction in FRAX probability.

Correlation of left ventricular eccentricity index with other scintigraphic parameters on gated myocardial perfusion single photon emission computed tomography

Background@#Left ventricular (LV) eccentricity index (EI) is a measure of the LV shapre obtained with a commonly used quantitative software for mycardial perfusion scintigraphy (MPS). However, there are limited studies evaluating its correlation with other MPS parameters, for which this study was done. @*Methodology@#All patients who underwent 99mTc-sestamibi stress MPS from 2013 to 2015 were screened. A total of 353 patients, 228 (65%) males and 125 (35%) females, met the inclusion criteria. One hundred twenty-nine (37%) underwent exercise stress while 224 (63%) were given dipyridamole. Spearman's rho correlation was used to determine the correlation of rest and post-stress EI with the other study variables. @*Results@#Among males, rest EI showed negative correlation with summed stress score (SSS) (rs = -0.182, p<0.005), transient ischemic dilatation (TID) (rs=-0.172, p=0.009), rest LV end-diastolic volume (EDV) (rs=-0.291, p < 0.001), rest LV end-systolic volume (ESV)(rs=-0.316, p < 0.001), p0-st-streSS LVEDV (rs= -0.218, p < 0.001), and post-stress LVESV (rs= -0.331, p < 0.001). There was positive correlation with rest LV ejection fraction (EF) (rs= 0.291,p < 0.001) and post-stress LVEF (r5 = 0. 336, p < 0. 001). No sig11ifico11t relationship with any of the MPS parameters was observed among females. For both exercise and dipyridamole groups. EI exhibited negative correlation with SSS, and rest and stress LVESV; and positive cotrelation with rest and post-stress LVEF. Significant relationship with rest and stress LVEDV was only observed in the dipyridamole group.@*Conclusions@#This study shows that EI is correlated with most, if not all, of the MPS parameters with different levels of association depending on the patient's sex and the type of stress employed. More spherical LV is correlated with more severe perfusion defects, larger LV cavity volumes and poorere LV systolic function.

Clinical utility of left ventricular ejection fraction reserve by stress thallium-201 myocardial gated single photon computed tomography among patients with and suspected coronary artery disease

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=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.

Value of Tl-201 imaging in predicting therapeutic I-131 uptake in patients with thyroglobulin-positive but I-131 scan negative differentiated thyroid cancer

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.

Prognostic value of coronary flow reserve (CFR) by dipyridamole single-photon emission computed tomography (SPECT) sestamibi imaging in predicting future cardiac events

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 4) perfusion scans were further subdivided based on their CFR whether normal (CFR> 2) or abnormal (CFR 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.

Myocardial perfusion scintigraphy in transposition of the great arteries after an arterial switch operation in infants

An abnormal myocardial perfusion is not uncommon in congenital heart defects (CHD). Many case reports and prospective studies were done describing myocardial peOision scintigraphy (MPS)findings after an arterial switch operation (ASO) among transposition of the great arteries (TCA), but to the best of the authors' knowledge, none have cited MPS findings in the immediate post-operative petiod. This paper aims to show two ckfferent clinicalthuatiomts in which (MPS) was used in the assessment of myocarchalfiinction in TCA immediatelyfollowing an arterial switch operation. Two male infants; aged 2 months and 4 months; both diagnosed with transposition of the great arteries presenting with past-operative morbidities after an arterial switch operation were referred to the Department of Nuclear Medicine/or evaluation. The younger infant was ditty discharged improved with an earlier magical intervention in contrast to the other who expired Bothpatients revealed a scintigraphic picture of myocarcbal ischemia and left ventricular a54ifiniction with concomitant right ventricular hypertrophy MPS .findings and reflective clinical pictures of patients with corrected congenital disease are yet to be/illy elticidated,.from the expected natural course after the stag/Cal intervention and long term complications ofsuch cases. The two cases present an invaluable avenue of non-invasive diagnostic modality using-MPS to assess probable pathologic mechanisms that occur after an arterial switch operation, and perhaps suggest incremental value not only in the post-operative period but in the preoperative scenario in the prognostication of these patients.

Quantitative parameters in Tc-99m pertechnetate thyroid scintigraphy predict increased gland uptake function

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 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.

Comparison of Fixed versus Calculated Activity of Radioiodine for the Treatment of Graves Disease in Adults

BACKGROUND: Radioactive iodine as a treatment modality has been shown in several studies to be a safe and effective therapy for Graves disease. However, there is still no uniformity regarding optimal dosing method. The aim of this study is to compare the efficacy of calculated and fixed dosing of radioiodine for the treatment of Graves disease. METHODS: A hundred twenty-two patients diagnosed with Graves disease were randomized to receive either fixed or calculated dose of radioiodine. Those randomized to fixed activity received either low fixed activity at 9.9 mCi for thyroid gland size <40 g or high fixed activity at 14.9 mCi for thyroid gland size 40 to 80 g, and those grouped to calculated activity received 160 µCi/g of thyroid tissue adjusted for 24 hours radioiodine uptake. Thyroid function tests (free thyroxine [T4] and thyroid stimulating hormone [TSH]) were monitored at 10, 16, and 24 weeks after radioactive iodine therapy. The primary outcome, treatment failure was defined as persistently elevated free T4 and low TSH. RESULTS: Of the 122 patients randomized, 56 in the fixed dose group and 56 in the calculated dose group completed the follow-up. At the end of 6 months, the percentage of treatment failure was 37.50% in the calculated dose group versus 19.64% in the fixed dose group with a relative risk of 0.53 (95% confidence interval, 0.28 to 0.98) favoring the fixed dose group. CONCLUSION: Fixed dose radioiodine has a significantly lower incidence of persistent hyperthyroidism at 6 months post-radioactive therapy.