John J. Coupal

Functional Retention of Tc-99m Mibi in Mediastinal Lymphomas As a Predictor of Chemotherapeutic Response Demonstrated by Consecutive Thoracic Spect Imaging

Tc-99m MIBI is used as a tumor imaging agent and has been proposed to measure p-glycoprotein function, which plays an important role in tumor multidrug resistance to chemotherapy. It has been reported that lung cancer and breast cancer with a high retention of Tc-99m MIBI have been more responsive to chemotherapy than tumors with low retention. Thus Tc-99m MIBI SPECT could be used as a measure of p glycoprotein function and consequently may serve as a predictor of the tumors responsiveness to chemotherapeutic agents. Described here are two patients with lymphomas, one with non-Hodgkins lymphoma and the other with Hodgkins disease, who underwent Tc-99m MIBI thoracic SPECT before and after chemotherapy. The sequential studies demonstrated a reduction in tumor size and diminished tumor uptake in one patient and disappearance of tumor uptake after a course of chemotherapy in the other patient. The data suggest that elevated Tc-99m MIBI uptake in a tumor as a result of retention by p glycoprotein not only demonstrates mediastinal involvement of lymphomas but also may be used to forecast responsiveness to chemotherapy.

Disorders of Gallbladder Function Related to Duodenogastric Reflux in Technetium-99m DISIDA Hepatobiliary Scintigraphy

Controversy exists over the relation between gallbladder dysfunction and the propensity for duodenogastric reflux. To evaluate this, Tc-99m DISIDA hepatobiliary imaging studies in 120 patients were reviewed, excluding patients who had had cholecystectomy or subtotal gastrectomy before scintigraphy. Serial images were obtained at 5, 10, 15, 30, 45, and 60 minutes and up to 24 hours, if indicated, after intravenous injection of 5–10 mCi of Tc-99m DISIDA. Normally, the liver, bile ducts, gallbladder, common bile duct, and bowel are visualized sequentially. Reversal of the normal sequence of gallbladder (GB) and bowel visualization indicates GB dysfunction; nonvisualization of the GB reflects cystic duct obstruction or absent GB function. Duodenogastric reflux is identified by radiotracer localized in the area just below or immediately adjacent to the tip of the left hepatic lobe. The intragastric location of the tracer may be verified by oral administration of 300 µCi of Tc-99m sulfur colloid. Twenty-nine patients had duodenogastric reflux between 10 and 60 minutes after injection. Of the 29 patients, 22 had a nonvisualized gallbladder, four had reversal of appearance of GB and bowel activity, and three had a normal study. GB dysfunction or nonfunction is more frequently demonstrated when duodenogastric reflux is present than with normal gallbladder function (P < 0.001). In conclusion, gallbladder malfunction is closely associated with duodenogastric reflux, an abnormality that may be diagnosed noninvasively by Tc-99m DISIDA hepatobiliary scintigraphy.

Axillary lymph node uptake of Tc-99m MIBI resulting from extravasation should not be misinterpretated as metastasis

Ipsilateral axillary lymph node visualization due to extravasation of Tc-99m MDP intravenous injection has been well documented. A patient with suspected angina underwent Tc-99m MIBI myocardial SPECT who had extravasation of Tc-99m MIBI in the antecubital region resulting in ipsilateral axillary lymph node uptake. This finding should not be misinterpreted as lymphatic nodal metastasis in a patient with breast cancer or lung cancer.

Tc-99m MIBI thoracic SPECT for the detection of intrathoracic tumor masses.

Thirty-one men (age range, 46-76 years; mean age, 64.8 years) with intrathoracic masses suggesting possible malignancy on the basis of chest radiography or CT underwent preoperative Tc-99m MIBI SPECT examinations. Diagnosis was confirmed on pathologic examinations of samples obtained either at thoracotomy, esophagectomy, or by biopsy. Twenty-five patients had primary lung cancer, including squamous cell carcinoma, large cell carcinoma, adenocarcinoma, and small cell carcinoma. Two patients had lymphomas with spread to the mediastinum, and three patients had extrathoracic primary cancers (one squamous cell carcinoma of esophagus, one squamous cell carcinoma originating from a head and neck tumor, and one metastatic mediastinal leiomyosarcoma). One patient with a tuberculoma had negative results of the Tc-99m MIBI examination. Tc-99m MIBI had a 86.7% sensitivity rate, a 0% false-positive rate, and a 100% positive predictive value to detect malignant intrathoracic masses. There was a 13% false-negative rate, however, suggesting that MIBI-SPECT may underdiagnose malignant lesions. SPECT findings of these 31 patients can be classified as 1) mass with increased uptake, n = 23; 2) ring-like appearance of increased uptake, n = 3; 3) mass with absent uptake, n = 4; and 4) photon-deficient mass, n = 1. Absent uptake in patients with mass lesions could be explained by necrosis of the lesion (caseation necrosis or massive tumor necrosis with or without bleeding). Most malignant intrathoracic masses are Tc-99m MIBI avid and may be detected with a high degree of sensitivity and with an excellent positive predictive value. A positive MIBI scan may help in the clinical diagnosis of malignancy. The use of Tc-99m MIBI could serve not only as a tumor imaging agent, but also may be used to determine the extent of spread and potentially the chemotherapeutic responsiveness of a tumor.

Diffuse and intense Tc-99m HMDP localization in the liver due to hypoxia secondary to respiratory failure.

After left lower lobe lobectomy for lung carcinoma, a patient had acute respiratory failure secondary to pneumonia and pulmonary embolism requiring a ventilator. Tc-99m HMDP bone scan showed diffuse, intense hepatic uptake. Concurrent liver enzymes indicated hepatic necrosis. Two weeks later the patient died and a limited chest autopsy confirmed acute adult onset respiratory distress syndrome. Etiologic factors of massive hepatic necrosis in relation to hepatic localization of bone imaging agent and its prognostic outcome are discussed.

Biologic Gastric Emptying Time Using Tc-99m TETA Polystyrene Resin in Various Clinical Conditions

In 82 subjects 82 gastric emptying studies using Tc-99m triethylene tetramine polystyrene resin were retrospectively evaluated. All six patients with diabetic gastroenteropathy (GE) had delayed biologic gastric emptying time (BGET) that responded well to metoclopramide (MP) injection. In 11 diabetics without GE, only two had prolonged BGET with good response to MP. All 11 patients with gastric outlet obstruction also had prolonged BGET, but no significant response to MP was found in 6 studies. Five of 7 patients with active gastric ulcer had delayed BGET. Three of ten patients with previous Billroth I or II operation had accelerated BGET, and 3 of 9 patients with previous vagotomy had delayed BGET with good response to MP. Markedly prolonged BGET with significant response to MP was also observed in 3 patients with disordered gastric motility. Delayed BGET was found in one patient with bile reflux gastritis and in 2 of 6 patients with reflux esophagitis. No prolongation of BGET was observed in 7 symptomatic patients whose radiographic and endoscopic examinations were negative. BGET studies with this agent appear to be reliable and very helpful in the management of patients with gastric symptoms and for obtaining an objective measurement of the response to therapy.

Diffuse thoracoabdominal radioactivity seen in bone imaging.

Diffusely increased radioactivity in the thoracoabdominal region (lower thorax and/or upper abdomen) occasionally has been observed when performing Tc-99m phosphonate bone studies. To assess the significance of activity in this finding, 1100 bone scintigrams were reviewed and the clinical data and other diagnostic imaging procedures were evaluated in these cases. With the exclusion of Tc-99m sulfur colloid liver-spleen scans 18 patients were found to have mild but diffuse increased radioactivity in the thoracoabdominal region either on the right or left. Clinical findings in these cases with abnormal uptakes were pleural effusions (six cases), hepatic colonic metastases (six cases), splenic metastases from bronchogenic carcinoma (one case), abdominal and peritoneal colonic metastases (one case), a massive metastatic squamous cell carcinoma (from lung) in the right lower chest (one case), and defective radiopharmaceuticals (three cases). Since the defective radiopharmaceuticals contained 5% of hydrolyzed reduced Tc-99m colloid by thin-layer chromatography, each of three patients received approximately 740 μCi of Tc-99m sulfur colloid. Factors to be considered in the interpretation of diffuse thoracoabdominal activity from a bone agent should include splenic or hepatic metastases, a Tc-99m sulfur colloid study within the previous 24 hours, pleural effusion, faulty radiopharmaceuticals, and abdominal and peritoneal colonic metastases.

I-123 hydroxyiodobenzyl propanediamine (HIPDM) cerebral blood flow imaging demonstrating transtentorial diaschisis.

To assess the clinical significance of transtentorial diaschisis (TTD) as demonstrated by 1-123 HIPDM brain imaging, SPECT and/or planar images of 35 patients with stroke, 26 patients with Alzheimers disease (AD), 2 patients with Creutzfeldt-Jakob disease (CJD), and 1 patient with a schizoaffective disorder were analyzed. TTD was observed in 21 of the 35 patients with strokes. In 13 stroke patients, TTD was associated with large infarcts in the middle cerebral artery (MCA) territory; in the remaining 8 stroke patients, TTD was associated with internal capsule and/or basal ganglia infarcts. TTD was not associated with small occipital or parietal infarcts. Despite cortical perfusion decrements, TTD was not seen in the AD patients, the CJD patients, or the patient with schizoaffective disorder. It is concluded that 1) TTD frequently occurs following cerebral infarct of the MCA territory (60% of the patients in this sample); 2) absence of TTD in the presence of a large cerebral perfusion abnormality may represent neuronal dysfunction of the cerebral cortex; and 3) the presence of TTD without a significant cortical perfusion abnormality may indicate basal ganglia and/or internal capsule infarct.

Complementary role of reticuloendothelial and hepatobiliary imaging agents in the assessment of liver disease

The merit of concomitant hepatic imaging with Tc-99m-sulfur colloid (SC) and Tc-99m-HIDA was examined in 40 patients with abnormal liver function tests. The studies were performed sequentially within a 2 to 5 day interval with 5 mCi each of SC or HIDA. Routine static images in all cases, and dynamic studies with HIDA in 15 patients, were graded and compared with the liver function tests and clinical diagnoses. Of the 40 patients, the images with SC showed an abnormality in 22 while HIDA images were abnormal in 38. Thirteen of 21 patients with hepatocellular diseases showed an abnormality of the SC images, and 20 of the same 21 patients had abnormal HIDA images. Abnormal HIDA images were more closely related to abnormal liver function tests. These results suggest that alterations of hepatic function reflected by abnormal liver function tests are better demonstrated with hepatobiliary imaging agents than with reticuloendothelial imaging agents, while either type of imaging agents will detect focal anatomic lesions.

I-123 HIPDM planar brain images demonstrating crossed cerebellar diaschisis.

I-123 HIPDM or IMP brain planar images, as well as SPECT images, have been useful in the detection of large lesion(s) of the cerebral cortex. Planar imaging may be useful not only for cerebral lesions, but also for a cerebellar abnormality and in certain clinical situations, such as phobia to a gantry or being too heavy for the imaging table, when SPECT imaging cannot be performed. The authors concur that a large cerebral lesion can be detected by planar images; in addition, cerebellar lesions, such as the presence of crossed cerebellar diaschisis (CCD), may be detectable by planar imaging using I-123 HIPDM. This article presents a patient with a large cerebral infarct detected by planar imaging whose CCD has been demonstrated by planar images.