Savita Puri

Dual radionuclide study of myocardial infarction. Relationships between myocardial uptake of potassium-43, technetium-99m stannous pyrophosphate, regional myocardial blood flow and creatine phosphokinase depletion.

The dual radionuclide myocardial distributions of imaging agents potassium43 (43K) and technetium-99m stannous pyrophosphate (99mTc-PYP) were studied in a 24-hour closed chest canine infarct preparation. In multiple myocardial biopsies in 20 dogs, tissue levels of both radionuclides were compared to either an index of tissue viability (myocardial creatine phosphokinase [CPK] depletion), or to estimates of regional myocardial blood flow as measured by the microsphere technique.Myocardial 4K uptake in the ischemic and infarcted zone correlated well with both CPK depletion (r = 0.73) and microsphere estimates of relative blood flow. The correlation with microspheres was excellent in the transmural sample (r = 0.93) as well as endocardial (r = 0.97) and epicardial (r = 0.86) portions.On the other hand, 99mTc-PYP myocardial uptake did not correlate with the extent of CPK depletion. Maximal uptake was frequently noted in border zones with only moderate CPK depletion, while lesser degrees of 99mTc-PYP uptake were noted in the central infarct zone where CPK activity was lowest. The relationship of 99mTcPYP uptake to microsphere regional flow estimates demonstrated that 99mTc-PYP uptake was maximal at flows of 0.3 to 0.4 of normal. At lower flows, 99mTc-PYP uptake fell toward normal levels. A similar relationship was noted between the distributions of 99mTc-PYP and 43K. In relatively high flow border segments (. 0.80 of normal), abnormal 99mTc-PYP uptake of five to six times normal persisted. The transmural distribution of 99mTcPYP demonstrated that in low flow regions 99mTc-PYP uptake was primarily epicardial, while in the higher flow ischemic periphery of the infarct endocardial uptake predominated. Thus, while there is a direct correlation between cationic 43K myocardial uptake and regional myocardial viability and blood flow, no such direct relationship exists for 99mTc-PYP. This is in part based on the necessity for delivery of the radioactive tracer to the infarct zone.

Role of coronary artery disease and collateral circulation in redistribution of thallium-201.

A total of 19 patients had myocardial perfusion imaging with thallium-201 thallous chloride (Tl-201) immediately after maximal treadmill exercise and 4–6 hours later (redistribution). They also were given rest–stress EKGs and coronary angiograms as part of an evaluation of coronary artery disease. Twenty-six defects were seen on initial postexercise scans in the 19 patients. Of these, 20 were in the region of noninfarcted myocardium and six were in zones of previous myocardial infarction (diagnosis based on the resting EKG). Of the 20 defects in noninfarcted myocardium, 12 were associated with significant obstruction (> 75%) of regional coronary vessels. The remaining eight had normal coronary arteries or ≤ 75% occlusion. Of the 12 defects with significant disease of coronary vessels, eight showed redistribution of Tl-201; there were functional collaterals to the involved vessels in all of these defects. Of the six defects in the region of prior myocardial infarction, no redistribution of Tl-201 was seen in five (one showed only partial redistribution). In this group, the incidence of collateral circulation was similar to that in noninfarcted myocardial cases. A significant association exists between redistribution of Tl-201 and absence of severe obstruction, or the presence of vessel disease, but with functional collaterals to the involved areas in patients with transient myocardial ischemia. Collaterals do not appear to influence redistribution of Tl-201 in zones of myocardial infarction.

FDG PET/CT Manifestations of Hematopoietic Malignancies of the Breast

Hematopoietic malignancies that can be encountered in the breast include lymphoma, leukemia, and multiple myeloma/plasmacytoma. These are readily imaged via [18]F-fluorodeoxyglucose position emission tomography (PET)/computed tomography (CT) and can manifest as unilateral, bilateral, single, multiple, round/oval masses, or diffuse. These malignancies can occasionally mimic primary breast cancers. Conversely, benign conditions, such as the lactating breast can resemble hematopoietic malignancies of the breast. Although uncommon, familiarity with hematopoietic malignancies of the breast is important for proper interpretation of PET/CT. In this pictorial review, the PET/CT imaging features of patients with hematopoietic malignancies of the breast will be described, including pathology-proven cases of acute myelogenous leukemia, diffuse B-cell lymphoma, follicular lymphoma, acute myeloid leukemia with neutropenic granulocytic) sarcoma, and plasmacytoma. In addition, potential pitfalls will be discussed.

FDG-PET on the trail of an unsuspected primary malignancy in the breast.

Proper identification of the primary malignancy can radically alter clinical management for the patients benefit. This is a report of an unsuspected primary breast cancer in a patient being worked up for presumptive lymphoma. Prior investigation of lymphedema in the left lower extremity found widespread lymphadenopathy on computed tomography imaging, leading to initial biopsy revealing adenocarcinoma of unknown primary. F-18 fluorodeoxyglucose PET/computed tomography altered management by localizing an F-18 fluorodeoxyglucose avid breast nodule, directing breast biopsy with specific immunohistochemical analysis for breast cancer lineage in metastatic adenocarcinoma. The patient responded well to breast cancer-targeted chemotherapy.