Timothy S. Burke

Pitfall to modified in vivo method of technetium-/sub 99m/ red blood cell labeling. Iodinated contrast media

Suboptimal labeling of red blood cells with Tc–99m, using the modified in vivo technique, was observed in three patients in whom labeling was attempted following IV administration of iodinated contrast media in the previous 24 hours. The mechanism is not understood, but it may represent a change in either stannous ion distribution or redox potential. It is recommended that studies employing Tc–99m RBC labeling using this technique be performed prior to administration of iodinated contrast media. This effect should be kept in mind in gastrointestinal bleeding studies performed using Tc–99m RBC, as well as in cardiac imaging studies.

Accumulation of Tc-99m MDP in amyloidosis involving the tongue.

Radionuclide bone imaging using Tc-99m phosphates may show accumulation of activity in amyloid deposits. While many sites of amyloidosis have been detected with bone imaging, many reports center on cardiac amyloidosis. The case reported here demonstrates accumulation of Tc-99m MDP in amyloidosis involving the skin and muscle, including the tongue.

Radionuclide detection of abnormal ventricular filling patterns in rejecting human allografts.

Parameters of systolic and diastolic function obtained from radionuclide ventriculography (RNV) were evaluated in nine cardiac allograft recipients. In 25 examinations, left end-diastolic volume (LEDV), cardiac output (CO), left ejection fraction (LEF), right ejection fraction (REF), heart rate (HR), peak filling rate (PFR), time to peak filling rate (TPFR), peak ejection rate (PER), and average filling rate for the first half of diastole (DFRH) were determined. Endomyocardial blopsy was obtained within 48 hours. Biopsies were divided into three treatment classes (0 = normal; 1 = rejection but not requiring supplemental therapy; and 2 = rejection requiring supplemental immunotherapy). Two independent variables of diastolic function proved to be significant (DFRH P > 0.00001, and PFR P > 0.002) predictors of the dependent variable class when regression analysis was applied to the data. Alterations in diastolic function associated with acute rejection are detectable on RNV and simulate changes anticipated in a primary restrictive cardiomyopathy.

Determinants of diagnostic accuracy in pulmonary scintigraphy for pulmonary capillary protein leak associated with adult respiratory distress syndrome (ARDS): A technical note

Radionuclide assessment of pulmonary capillary protein leak using [99mTc] human serum albumin (99mTc-HSA) was first reported from our laboratory. In this study we investigated the impact of 1) sampling time post tracer injection, and 2) lung region assignment, on diagnostic accuracy between 2 groups (controln=20 and ARDSn=20). Each patient received 370 MBq99mTc-HSA i.v. and was imaged for 45 min. The slope index (SI) [change in lung: heart activity ratio/min] was calculated from 11 computer assigned lung regions for intervals of 5–15 (early [E]) and 15–45 (late [L]) min. The diagnostic accuracy of E vs L SI calculations for the 11 regions was evaluated by stepwise logistic regression. E SI data and L SI data from the lower 1/3 of the lung did not achieve significance for inclusion in the discriminant model (P<0.05). In the nine remaining regions L SI was significant. Optimal discrimination was achieved from L SI data obtained from a region confined to the lateral half of the mid 3rd of the lung field (sensitivity 81%, specificity 85%, accuracy 83%). The results confirm that: 1) a late (15–45 min) sampling period and 2) proper region assignment are necessary to maximize accuracy of this technique.

Artifactual focal accumulation of Tc-99m bone imaging tracer in the chest. Technical note (bone imaging artifact).

Four patients undergoing routine bone imaging with a Tc-99m bone imaging agent were observed to have multiple focal areas of increased uptake in the lungs. Delayed or repeat examination demonstrated resolution of the areas. The authors conclude that this was an isolated and bizarre case of aggregate formation.

Tl-201 uptake in pulmonary mycobacterium avium complex infection

Primary lung cancers are well known causes of increased pulmonary Tl-201 uptake that may be detected during myocardial perfusion scintigraphy. Other cancers and various benign conditions may also show increased Tl-201 accumulation and may be initially detected as incidental findings during myocardial perfusion scintigraphy. This report demonstrates Tl-201 uptake in a patient with pulmonary Mycobacterlum avium complex infection.

Significance of alteration in biodistribution of labeled lymphocytes exposed to stannous ion

The biodistribution patterns of 99mTc (99mTc-lymph) and 111In-lymphocytes with [111In-(Sn)-lymph] or without (111In-lymph) stannous ion treatment was compared in Lewis rats. Syngeneic lymphocytes were labeled with either 125 μCi (4.63 MBq) 99mTc or 5 uCi (1985 kBq) 111In per 2×107 cells. Mean labeling efficiency for 99mTc and 111In was 68.61%±3.90% (SEM) and 87.22%±2.01% (SEM) respectively. 99mTc-lymph (n=4), 111In-lymph (n=6) and 111In-(Sn)-lymph (n=6) rats received 2x107 cells and were killed 18 h later. While 99mTc-lymph demonstrated significantly less localization in spleen, lymph nodes, and blood (P(F)0.01) as compared with 111In-lymph, 111In-(Sn)lymph also demonstrated a significant difference (P[F]=0.0001) in lymph node accumulation when compared to 111In-lymph. As the activity levels utilized are not associated with cell radiation damage, these alterations in biodistribution do not reflect viability or chromosomal damage, but appear related to stannous ion exposure.

Relative decreased splenic uptake of Tc-99m-sulfur colloid in patients with pancreatic carcinoma

Relative spleen/liver activity ratio was determined from posterior projection images using a photodensitometric method. Ratios from scans of 22 patients with proven pancreatic carcinoma (12 from rectilinear scans and 10 from scintillation camera images) were determined and compared to studies from patients documented as normal and to randomly selected liver/spleen imaging studies which had been previously interpreted as normal. The mean ratio from the pancreatic carcinoma group was significantly lower than the means of the respective normal groups (p[t] < .0001 for rectilinear scans and p[t] < .001 for scintigrams). There was no significant difference between the means of the proven normal and randomly selected normal groups or between the two pancreatic carcinoma groups. Splenic vascular alteration is discussed as a possible reason for decreased splenic distribution of Tc-99m-sulfur colloid in this patient group.

Discordant findings in technetium-99m pertechnetate and iodine-123 thyroid imaging caused by vascular retention in the superior vena cava

This report demonstrates superior vena cava (SVC) retention of Tc-99m pertechnetate as a cause of discordant findings in thyroid imaging performed with Tc-99m pertechnetate and l-123.

Hepatic infarction detected on Tc-99m sulfur colloid imaging.

Hepatic infarctions are rarely encountered, and scintigraphic findings are reported even less frequently in this entity. A patient who developed a left hepatic lobe infarct after surgical resection of a celiac axis aneurysm is described and a brief review of hepatic infarction is presented.