Lymphoscintigraphy of melanoma: lymphatic channel activity guides localization of sentinel lymph nodes, and gamma camera imaging/counting confirms presence of radiotracer in excised nodes.

UNLABELLED: Lymphoscintigraphy has become a standard preoperative procedure to map the cutaneous lymphatic channel for progression of nodal metastasis of melanoma of the skin. Lymphoscintigraphy was employed to visualize lymphatic channels as a guide to identify sentinel lymph nodes (SLNs). Excised tissue was imaged with a gamma camera to verify the findings of presurgical lymphoscintigraphy. Percent counts of SLN(s) among the total counts of the excised melanoma tumor or scar tissue and SLN(s) were calculated. METHODS: Eleven patients with cutaneous melanoma received four to ten intradermal injections of Tc-99m sulfur colloid at elual distances around the melanoma site. Images were made immediately after injection: 1 minute per image for 15 min; and then 5 minutes or 1,000,000 counts per image for 30 min. After surgery, the excised melanoma tumor or scar and SLN(s) were imaged/counted with a gamma camera. Percent counts of SLNs among the total counts of the excised melanoma tumor or scar tissue and SLNs were calculated. To validate the specimen count accuracy, an experimental phantom study was done. RESULTS: Linear lymphatic channels were identified between the injected sites and the SLNs in each patient. Gamma camera images demonstrated radioactivity in the SLNs of all patients, verifying the lymphoscintigraphy findings. Uptake in the SLNs of ten of the eleven patients ranged from 0.4 to 7.2% (mean 2.2%) of the total counts in excised tissue. We noted that a node with lower uptake should not be ignored because a lower percent of SLN activity does not necessarily rule out existing metastasis. In two of eleven patients, histopathologic showed metastases. One patient's melanoma on the middle back had lymphatic channel activity directed to both axillae. The results of the phantom study validated accuracy of our specimen counts. CONCLUSIONS: Because linear lymphatic channels existed between lymph nodes and the injected sites in all eleven patients, these lymphatic channels could be used as a guide for localizing SLNs. The SLNs indicated by presurgical lymphoscintigraphy were verified by postoperative gamma camera imaging, and radiotracer localization in the SLNs averaged 2.2%.

Localization of (99m)Tc HMDP in an extraskeletal myxoid chondrosarcoma: a case report.

Extraskeletal myxoid chondrosarcoma of the lower extremity is rare, and slowly progressive. The authors of this article present the case of a man with progressive enlargement of the right thigh that underwent bone scintigraphy. The bone images showed a diffuse, moderate increase in uptake in the swollen right thigh. Despite chemotherapy, the patient died 28 mo later. At autopsy, it was confirmed that he had extraskeletal myxoid chondrosarcoma of the right thigh, which had metastasized to the upper arms, left scapula, lungs, pleurae, and right lower quadrant of the abdomen. The myxoid chondroid matrix, a major feature of the extraskeletal myxoid chondrosarcoma, is thought to account for the localization of the bone-imaging agent.

Radioactive contamination of packing materials from a xenon-133 shipment.

OBJECTIVE: We report on radioactive contamination of packing materials from a 133Xe shipment. METHODS: A 2-vial 133Xe shipment was monitored using a survey meter before opening. Both vials were immediately assayed in a dose calibrator. The packing materials were monitored and contamination was detected. RESULTS: The maximum surface reading of the shipment was 7.0 microSv/h. This was higher than previous shipments (1.1 +/- 0.3 microSv/h). One vial was 544 MBq while the other vial was only 474 MBq. Previous shipments were 565 +/- 13 MBq/vial. Monitoring and imaging revealed 133Xe contamination within the packing materials. Xenon-133 escaped from the packing materials over time. The lower activity vial continued to leak 133Xe over time. CONCLUSION: Careful monitoring of 133Xe shipments before and after opening along with assaying vials on receipt can indicate vial leakage and radioactive contamination so steps can be taken to minimize radiation exposure to the staff.

Axillary lymph node uptake of Tc-99m MIBI resulting from extravasation should not be misinterpreted 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.

Normal variants of a photon-deficient area in the lower sternum demonstrated by bone SPECT.

PURPOSE: A highly variable normal appearance of the sternal area makes interpretation difficult on planar bone imaging. These normal variants occur especially in the area above the xiphoid process of the sternum in which an oval photopenic area on anterior planar images may be seen. This finding is most likely caused by localized incomplete fusion. METHODS: Of a group of 188 patients, 35 patients (33 men, 2 women; age range, 30 to 85 years; mean age, 57 years) were examined with sternal SPECT and planar bone imaging. These patients, who had no history of sternal trauma, surgery, radiation, or infection, were referred for bone scan for metastatic work-up (n = 20), back pain (n = 6), and other conditions (n = 9). Thus 11 of 35 (31%) patients had a SPECT study that showed a photopenic area in the lower sternum. RESULTS: The incidence of this normal variant was higher than the 2% to 7.7% previously reported, indicating improved detection by SPECT. The normal variant appears to be less apparent on planar bone images and is seen more clearly on SPECT images. CONCLUSION: Differentiation from malignancy appears to be related to lesion symmetry, location, midline, and evenly distributed radioactivity surrounding the edge of the photopenic area.

Bone agent localization in hepatic metastases.

We present the bone scintigrams of two patients, which demonstrate diffuse extraosseous uptake of a bone agent in metastatic masses in the liver, one from a primary lung tumor and one from a primary breast tumor. The bone imaging agent did not localize in the brain metastases in these patients. CTs of the abdomen in both patients showed massive metastases in the liver with multiple areas of tumor necrosis. The CT of the abdomen of the breast cancer patient showed multiple small hepatic calcifications. Autopsy revealed massive tumor necrosis with calcifications in the enlarged liver. In routine bone scintigraphy, diffuse uptake of bone agents in the liver of a patient with a known malignancy should be considered suggestive of massive hepatic metastases.

Localization of a bone imaging agent in a calcified hematoma.

A patient with chronic renal failure and secondary hyperparathyroidism had iliac bone biopsy. The procedure was complicated by a soft-tissue hematoma, which had calcified. A 3-4-cm palpable mass was visible in the lower left abdominal wall. Intense uptake of 99mTc-HMDP corresponded with the location of the calcified hematoma in this patient.

Detection of abscesses with Tc-99m HMPAO leukocyte scintigraphy depends on their stage and location.

Two abscesses were shown on CT in a 72-year-old man: one in the left hip and one in the left pelvic region that resulted from a motor vehicle collision that occurred 8 months earlier. Bone scintigraphy showed increased uptake in the left hip area. On Tc-99m HMPAO leukocyte imaging, the hip area appeared to be photopenic, and the abscess of the left pelvis was not identified. Incidental uptake in the left lung base appeared to be an active acute inflammatory process as evidenced by an infiltrating lesion in the left lower lung on a chest radiograph. Because leukocyte scintigraphy cannot detect the presence of a chronic inflammatory process in the absence of acute inflammatory cells, the patient's abscesses in the left hip and the left pelvis did not localize Tc-99m HMPAO-labeled neutrophils. The cold lesion in the left hip area was most likely caused by the lesion in the reticuloendothelial system (bone marrow); the unidentifiable pelvic lesion was related to the area(s) outside the reticuloendothelial system. In interpreting a labeled leukocyte image, clinicians should be alert to the stage (chronic or acute) and location (regardless of whether in the reticuloendothelial system) of infectious lesion(s). In this patient, a wide spectrum of manifestations was evident on leukocyte scintigraphy.

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.

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 tumor's responsiveness to chemotherapeutic agents. Described here are two patients with lymphomas, one with non-Hodgkin's lymphoma and the other with Hodgkin's 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.

An unusual case of a tibial metastasis as the clinical presentation of bronchogenic adenocarcinoma.

A patient with initial complaints of leg pain and difficulty walking was found to have a large right tibial metastatic tumor and poorly differentiated adenocarcinoma of the lung. Findings from total-body bone scintigraphy include a large area of increased uptake in the proximal half of the right tibia with a photon-deficient area medially, and focal areas of uptake in a right rib, in the femoral neck and the left ileum. An irregular area of increased uptake in the left lung mass was shown by thoracic bone SPECT. This is an unusual case of a tibial metastasis as the first clinical presentation of bronchogenic adenocarcinoma.

Nonuniformity intrinsic flood artifact caused by point-source syringe needle.

UNLABELLED: The purpose of this study was to investigate the cause of a nonuniformity artifact seen on an intrinsic flood. METHODS: Intrinsic floods were acquired on three different cameras using a point source in a 1-cc syringe, with and without a needle attached. Floods were obtained with the syringe placed perpendicular and parallel to the camera face. RESULTS: A nonuniformity artifact was evident if a syringe with a needle was placed perpendicular to the crystal face. CONCLUSION: If a syringe is used as a point source during the acquisition of an intrinsic quality control flood, the needle should not be placed perpendicular to the camera face.

A normal technetium-99m-DTPA renogram in renal cell carcinoma: a case report.

A 64-yr-old man with a renal mass had a preoperative 99mTc-DTPA renal flow study and renogram. An area of minimally relative increase in flow in the upper half of the right kidney was thought to reflect the high vascularity of the renal mass. A subsequent renogram showed no mass defect in the area of relatively high flow of the right kidney. The patient had a right nephrectomy. The removed kidney showed an extrarenal mass measuring 6 x 5.5 x 5 cm at the upper pole of the kidney. The mass was confirmed to be a renal cell carcinoma, clear cell type. There was no renal tissue invasion. These finding suggest an extrarenal mass pattern may be difficult to identify with a normal appearing renogram.

A mural thrombus of an infrarenal aortic aneurysm demonstrated as photon deficiency in a radionuclide study.

Radionuclide angiogram (RNA) and aortogram may underestimate external aneurysmal diameter. Photon deficient areas are not uncommon along the abdominal aortic aneurysm (AAA) on RNA. To determine whether or not photon deficient areas along the aneurysm could represent a large thrombus, we studied radionuclide aortic angiography in thirty-eight patients during a preoperative cardiac gated study. All the patients (men, ages from 60 to 78) had CT, US, and/or aortogram for comparison. The presence of a thrombus was determined by CT, US, and/or surgical findings. Twelve of 38 (32%) patients' RNA and blood pool images showed photon deficient areas along the aneurysmal walls having a large concentric or eccentric thrombus of the AAA. A large photon deficient area could be detected along the narrowing calibre of the aorta lumen. This finding results from a large mural thrombus being interposed between the left or right bowel/mesentery activity and the activity of the aneurysms functioning patent lumen. We concluded that a photon deficient area along an inferorenal aortic aneurysm may indicate a large thrombus of either eccentric or concentric type within an AAA.

Medullary thyroid carcinoma imaged by Tc-99m MIBI SPECT and Tl-201 chloride/Tc-99m pertechnetate subtraction SPECT.

A 61-year-old man with medullary thyroid carcinoma and local invasion of the left lobe of the thyroid had Tc-99m MIBI SPECT and Tl-201 chloride/Tc-99m pertechnetate subtraction SPECT after left lobectomy of the thyroid, using a triple-headed gamma camera. Tl-201 chloride/Tc-99m pertechnetate subtraction demonstrated a large mass with high Tl-201 uptake in the left neck. Although there was intense uptake in the tumor in the left thyroid bed on Tc-99m MIBI neck SPECT, there was also uptake in both salivary glands and the right lobe of the thyroid gland. Thus, uptake in the right lobe of the thyroid gland and the salivary glands might not be differentiated from tumor invasion or metastasis from medullary cell carcinoma. Compared with MIBI SPECT, Tl-201 chloride/Tc-99m pertechnetate subtraction SPECT shows more apparent delineation of tumor uptake and may be a preferable technique.