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.

Association of coronary flow reserve by dipyridamole technetium-99m sestamibi single photon emission computed tomography with perfusion findings and risk factors for coronary artery disease

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.