Alan D. Waxman

A new technique for assessing right ventricular ejection fraction using rapid multiple-gated equilibrium cardiac blood pool scintigraphy. Description, validation and findings in chronic coronary artery disease.

A reproducible, noninvasive technique for determining right ventricular ejection fraction (RVEF) was developed using multiple-gated equilibrium blood pool scintigraphy, which allows serial rapid measurements without reinjection of radioactivity. Studies were obtained using in vitro labeled technetium- 99m red blood cells, gamma camera and computer. In 20 patients, RVEF determined by multiple-gated equilibrium imaging in the left anterior oblique view was compared with RVEF measured by first-pass scintigraphy. For both types of imaging, multiple regions of interest (ROIs) were used for RVEF. The accuracy of RVEF using equilibrium scintigraphy was also evaluated using a single ROI. In 20 additional patients, rapid (2-minute) equilibrium scintigraphy for RVEF was compared with standard (6-minute) imaging. Excellent correlation (r = 0.94) for RVEF was found between multiple-gated equilibrium scintigraphy and the first-pass technique when multiple ROIs were used. Inter- and intraobserver variations for the equilibrium method were small (r = 0.91 and r = 0.98, respectively). RVEF with the 2-minute equilibrium technique correlated well with the 6-minute method (r = 0.98). In contrast to the high correlation when multiple ROIs were used, analysis of equilibrium scintigraphy by single ROI severely underestimated first-pass RVEF and showed poor correlation (r = 0.60).In 15 normal subjects and 21 patients with significant coronary artery disease and different degrees of right coronary artery stenosis, simultaneous left ventricular ejection fraction (LVEF) and RVEF were measured. RVEF was less than LVEF in normal subjects (0.48 ± 0.05 vs 0.63 ± 0.08, mean ± SD). In patients with coronary artery disease, RVEF was not significantly different from that in the normal group, regardless of the degree of stenosis of the right coronary artery. We conclude that 1) multiple-gated equilibrium scintigraphy is a very accurate and reproducible new technique for determining RVEF; 2) the technique may be performed rapidly, and is therefore well suited to serial assessment of right ventricular function during exercise; 3) multiple ROIs are necessary for accurate measurement with this technique; and 4) RVEF is normally less than LVEF and is not significantly affected at rest by right coronary artery disease.

Transient ischemic dilation of the left ventricle on stress thallium-201 scintigraphy: a marker of severe and extensive coronary artery disease.

On exercise thallium-201 scintigraphy, it has been noted that the size of the left ventricle is sometimes larger on the immediate poststress image than on the 4 hour redistribution image; this phenomenon has been termed transient ischemic dilation of the left ventricle. The angiographic correlates of this finding were assessed in 89 consecutive patients who underwent both stress-redistribution thallium-201 scintigraphy and coronary arteriography. A transient dilation ratio was determined by dividing the computer-derived left ventricular area of the immediate postexercise anterior image by the area of the 4 hour redistribution image. In patients with a normal coronary arteriogram or nonsignificant coronary stenoses (less than 50%), the transient dilation ratio was 1.02 +/- 0.05 and, therefore, an abnormal transient dilation ratio was defined as greater than 1.12 (mean + 2SD). The transient dilation ratio was insignificantly elevated in patients with noncritical coronary artery disease (50 to 89% stenosis) (1.05 +/- 0.05) and in patients with critical stenosis (greater than or equal to 90%) of only one coronary artery (1.05 +/- 0.05). In contrast, in patients with critical stenoses in two or three vessels, the transient dilation ratio was significantly elevated (1.12 +/- 0.08 and 1.17 +/- 0.09, respectively; p less than 0.05 compared with all other patient groups). An abnormal transient dilation ratio had a sensitivity of 60% and a specificity of 95% for identifying patients with multivessel critical stenosis and was more specific (p less than 0.05) than were other known markers of severe and extensive coronary artery disease, such as the presence of multiple perfusion defects or washout abnormalities, or both.(ABSTRACT TRUNCATED AT 250 WORDS)

Time to completed redistribution of thallium-201 in exercise myocardial scintigraphy: relationship to the degree of coronary artery stenosis.

The relationship between the severity of coronary artery stenosis and the time to completed redistribution of thallium 201 (TI-201) defects following maximal exercise was investigated in 59 patients undergoing stress-redistribution TI-201 scintigraphy, coronary angiography, and contrast ventriculography. Multiple view TI-201 scintigrams were obtained, beginning 6 minutes (immediately post stress), less than 1 hour (early), 3 to 5 hours (average), and 18 to 24 hours (late) following intravenous TI-201 injection at peak exercise. Angiographic lesions were grouped into five levels of severity by percent stenosis. In the 107 defects which were seen on the immediate post stress images, early redistribution was noted in 15 (14%) and late redistribution was found in 23 (21%). In addition, there was a correlation (r = 0.56) between the time to completed redistribution and the severity of the coronary artery stenosis (p = 0.001). In comparison to defects with early and average redistribution, the segments contralateral to those with defects showing late redistribution more often had a critical stenosis supplying that segment. The frequency of myocardial infarction on ECG and the number of segments with akinetic and dyskinetic wall motion were less in defects undergoing late rather than no redistribution. Thus the time to completed TI-201 redistribution following stress appears to be related to the severity of stenosis in the coronary artery supplying the defect. Also, late redistribution is associated with the presence and early redistribution with the absence of a significant stenosis in the coronary artery to the contralateral segment.

Right ventricular ejection fraction during exercise in normal subjects and in coronary artery disease patients: assessment by multiple-gated equilibrium scintigraphy.

SUMMARYThe response of right ventricular ejection fraction (RVEF) during exercise and its relationship to the location and extent of coronary artery disease are not fully understood. We have recently developed and validated a new method for scintigraphic evaluation of RVEF using rapid multiple-gated equilibrium scintigraphy and multiple right ventricular regions of interest. The technique has been applied during upright bicycle exercise in 10 normal subjects and 20 patients with coronary artery disease. Resting RVEF was not significantly different between the groups (0.49 ± 0.04 vs 0.47 ± 0.09, respectively, mean ± SD). In all 10 normal subjects RVEF rose (0.49 ± 0.04 to 0.66 ± 0.08, p < 0.01) at peak exercise. At peak exercise in coronary artery disease patients, the group RVEF remained unchanged (0.47 ± 0.09 to 0.50 + 0.11, p = NS), but the individual responses varied. In the coronary artery disease patients, the relationship between RVEF response to exercise and exercise left ventricular function, septal motion and right coronary artery stenosis were studied. Significant statistical association was found only between exercise RVEF and right coronary artery stenosis. RVEF rose during exercise in seven of seven patients without right coronary artery stenosis (0.42 ± 0.06 to 0.58 ± 0.08, p = 0.001) and was unchanged or fell in 12 of 13 patients with right coronary artery stenosis (0.50 + 0.09 to 0.45 ± 0.10, p = NS). We conclude that (1) in normal subjects RVEF increases during upright exercise and (2) although RVEF at rest is not necessarily affected by coronary artery disease, failure of RVEF to increase during exercise, in the absence of chronic obstructive pulmonary disease or valvular heart disease, may be related to the presence of significant right coronary artery stenosis. The possibility that severe left ventricular dysfunction in the absence of proximal right coronary artery obstruction may cause abnormal RVEF response to stress requires further evaluation in a larger, more varied patient population.

The Effectiveness of Radioactive Iodine for Treatment of Low-Risk Thyroid Cancer: A Systematic Analysis of the Peer-Reviewed Literature from 1966 to April 2008

BACKGROUND Radioactive iodine (RAI) remnant ablation has been used to eliminate normal thyroid tissue and may also facilitate monitoring for persistent or recurrent thyroid carcinoma. The use of RAI for low-risk patients who we define as those under age 45 with stage I disease or over age 45 with stage I or II disease based on American Joint Committee on Cancer (AJCC) 6th edition, or low risk under the metastases, age, completeness of resection, invasion, size (MACIS) staging system (value <6) is controversial. In this extensive literature review, we sought to analyze the evidence for use of RAI treatment to improve mortality and survival and to reduce recurrence in patients of various stages and disease risk, particularly for those patients who are at low risk for recurrence and death from thyroid cancer. METHODS A MEDLINE search was conducted for studies published between January 1966 and April 2008 that compared the effectiveness of administering versus not administering RAI for treatment of differentiated thyroid cancer (DTC). Studies were grouped A through D based on their methodological rigor (best to worst). An analysis, focused on group A studies, was performed to determine whether treatment with RAI for DTC results in decreased recurrences and improved survival rates. RESULTS The majority of studies did not find a statistically significant improvement in mortality or disease-specific survival in those low-risk patients treated with RAI, whereas improved survival was confirmed for high-risk (AJCC stages III and IV) patients. Evidence for RAI decreasing recurrence was mixed with half of the studies showing a significant relationship and half showing no relationship. CONCLUSIONS We propose a management guideline based on a patients risk-very low, low, moderate, and high-for clinicians to use when delineating those patients who should undergo RAI treatment for initial postoperative management of DTC. A majority of very low-risk and low-risk patients, as well as select cases of patients with moderate risk do not demonstrate survival or disease-free survival benefit from postoperative RAI treatment, and therefore we recommend against postoperative RAI in these cases.

The use of gallium-67 in pulmonary disorders

Imaging of the chest cage with gallium-67 (67Ga) citrate is relatively easier to perform and interpret than imaging of the abdomen, because normally pulmonary concentration is low after 48 hr and physiologic accumulation in bones and breast can be recognized by its distribution. Modern scintillation detectors, particularly large field cameras with multiple pulse-height analyzers, give substantially better gallium images than those available in the past. Because of the nonspecific affinity of gallium through neoplastic and inflammatory processes, its value in the differential diagnosis of pulmonary diseases is limited. However, based on the literature and our own observations in over 1100 patients with established diagnosis of a variety of pulmonary diseases, we feel that the judicious use of 67Ga in selected patients is helpful in answering specific questions. These include preoperative evaluation of hilar and mediastinal involvement in pulmonary neoplasms, differential diagnosis of pulmonary infarctions and bacterial pneumonias, evaluation of pulmonary infiltrates regarding infectious etiology, follow-up of sarcoidosis on corticosteroid treatment, assessment of inflammatory activity in interstitial fibrosis and, in selected cases, early detection of neoplastic and inflammatory diseases before radiography becomes abnormal, such as diffuse carcinomatosis and Pneumocystis carinii infection. Potential large-scale application of pulmonary gallium imaging could be found in the screening of subjects exposed occupationally to noxious dust and in long-term serial follow-up of pulmonary tuberculosis patients for treatment response and reactivation. However, it remains to be seen whether gallium imaging statistically provides essential additional information in these indications when compared to cheaper conventional techniques.

The SNMMI Practice Guideline for Therapy of Thyroid Disease with 131I 3.0

1UC Health University Hospital, Cincinnati, Ohio; 2Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania; 3Beaumont Health System, Royal Oak, Michigan; 4Guy’s Hospital, London, United Kingdom; 5Columbia University Medical Center, New York, New York; 6Cincinnati Children’s Medical Center, Cincinnati, Ohio; 7New York–Presbyterian/Weill Cornell Medical Center, New York, New York; 8University of Southern California, Los Angeles, California; 9University of California at Los Angeles, Los Angeles, California; 10Vanderbilt University Medical Center, Nashville, Tennessee; 11Beth Israel Deaconess Medical Center, Boston, Massachusetts; 12Mallinckrodt Institute of Radiology, St. Louis, Missouri; 13Jacobi Medical Center, Bronx, New York; 14Vanderbilt University, Nashville, Tennessee; and 15Cedars-Sinai Medical Center, Los Angeles, California

Usefulness of 123I-MIBG Scintigraphy in the Evaluation of Patients with Known or Suspected Primary or Metastatic Pheochromocytoma or Paraganglioma: Results from a Prospective Multicenter Trial

Although 123I-MIBG has been in clinical use for the imaging of pheochromocytoma for many years, a large multicenter evaluation of this agent has never been performed. The present study was designed to provide a prospective confirmation of the performance of 123I-MIBG scintigraphy for the evaluation of patients with known or suspected primary or metastatic pheochromocytoma or paraganglioma. Methods: A total of 81 patients with a prior history of primary or metastatic pheochromocytoma or paraganglioma and 69 with suspected pheochromocytoma or paraganglioma based on symptoms of catecholamine excess, CT or MRI findings, or elevated catecholamine or metanephrine levels underwent whole-body planar and selected SPECT 24 h after the administration of 123I-MIBG. Images were independently interpreted by 3 masked readers, with consensus requiring agreement of at least 2 readers. Final diagnoses were based on histopathology, correlative imaging, catecholamine or metanephrine measurements, and clinical follow-up. Results: Among 140 patients with definitive diagnoses (91, disease present; 49, disease absent), 123I-MIBG planar scintigraphy had a sensitivity and specificity of 82%. For patients evaluated for suspected disease, sensitivity and specificity were 88% and 84%, respectively. For the subpopulations of adrenal (pheochromocytoma) and extraadrenal (paraganglioma) tumors, sensitivities were 88% and 67%, respectively. The addition of SPECT increased reader confidence but minimally affected sensitivity and specificity. Conclusion: This prospective study demonstrated a sensitivity of 82%−88% and specificity of 82%−84% for 123I-MIBG imaging used in the diagnostic assessment of primary or metastatic pheochromocytoma or paraganglioma.

Reevaluation of the impact of a stringent low-iodine diet on ablation rates in radioiodine treatment of thyroid carcinoma.

Prior analyses of the impact of stringent, preablative low-iodine diets (LIDs) on ablation in patients with differentiated thyroid cancer postthyroidectomy are dated. We retrospectively reviewed first-time, short-term ablation rates for 44 LID patients and 50 patients following a regular diet (RD) who were verbally instructed to avoid salt, seafood, and multivitamins containing iodine. Patients who had undergone ablation were given between 100 and 200 mCi of 131I, depending on the presence of metastases. We found a 68.2% ablation rate for LID patients, compared to a 62.0% rate for RD patients, a nonsignificant difference (p = 0.53). We observed a dose-response relationship for both patient groups, with higher ablation rates corresponding to higher doses of radioiodine administered. We also measured iodine levels in spot urine samples from 7 matched LID patients and 7 matched RD adherents (healthy volunteers) prediet and postdiet as well as 39 healthy volunteers. LID patients had a lower mean urinary iodine level postdiet (173.9 microg/L; range, 45-1,217 microg/L; standard deviation [SD] = 127.7) than the RD patients (mean, 381.4 microg/L; range, 140-630 microg/L; SD = 196.3) or the 39 normal controls (444.0 microg/L; range, 50-1,690 microg/L; SD = 413.4). Whereas the LID lowered urinary iodine levels by 69.4% from prediet values, the RD reduced urinary iodine by 23.6%. Although differences in the reduction of urinary iodine levels between the LID and the RD were substantial, both groups experienced equivalent outcomes. The level of iodine in the American diet has progressively decreased, and may be much lower now than when prior LID studies were conducted. We suggest that prescribing a refined, less stringent diet that avoids high-iodine-containing foods would offer equivalent outcomes with increased patient convenience.

False-positive iodine-131 body scan caused by a large renal cyst.

Focal I-131 accumulation is generally a reliable indicator of functioning thyroid tissue or a differentiated thyroid cancer metastasis. Normal accumulation of activity may be seen in areas such as the intestinal tract, liver, and salivary glands. This report describes a patient with significant accumulation of I-131 in the right upper quadrant of the abdomen. The abnormality, first thought to represent metastastic thyroid carcinoma, was subsequently proven to be accumulation within a large renal cyst.