Sylvia Magoun

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.

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.

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.

Correlation of prostate-specific antigen and technetium-99m HMDP bone imaging.

For an evaluation of the clinical utility of prostate-specific antigen (PSA), 32 prostatic carcinoma patients (ages 54-76) and 13 nonprostatic carcinoma patients (ages 60-70) underwent PSA measurements and bone imaging. At the time of bone imaging, each patients PSA value was measured by a monoclonal immunoradiometric assay. All 13 nonprostatic carcinoma patients (11 bronchogenic, 1 colon, and 1 urinary bladder) gave normal PSA values, although 6 had metastatic bone disease. The 32 prostatic cancer patients were divided into 2 groups of 16 each; PSA levels in Group 1 were abnormal (≥ng/ml): PSA levels in Group 2 were normal (< 4 ng/ml). In Group 1, bone images of 14 patients showed bone metastases; 6 of the 14 showed progression of metastases in a 6- to 12-month period. Two patients in Group 1 were negative for skeletal metastases. Twelve patients in Group 2 were negative for skeletal metastases; bone imaging in 1 showed regression of skeletal metastases; and 3 patients had unchanged bone lesion(s). The data indicate that PSA measurements may enhance bone imaging interpretation and provide valuable clinical monitoring of prostatic carcinoma. In the case of a patient with positive bone imaging and an unknown primary, PSA measurements may definitively determine if metastases originated from prostatic carcinoma.

Intense bone imaging agent uptake in the soft tissues of the lower legs and feet relating to ischemia and cold exposure

We present a patient with diffuse and intense uptake in the soft tissues of both lower legs and feet seen on 99mTc-HMDP bone scintigraphy. This finding presumably resulted from compromised blood supply to the lower legs plus a cold environment. The extraosseous bone imaging agent localization was presumably related to an existing ischemic condition that was exacerbated by cold. Differential diagnosis of the scan pattern should be differentiated from the artifact of socks contaminated by radioactive urine.

Open Rib Biopsy Guided by Radionuclide Technique

When abnormally increased radioactivity is seen in a rib or ribs by bone imaging in a patient with suspected or known malignancy, it frequently is difficult to differentiate fracture from metastatic disease. Histological examination of the lesion is crucial for diagnosis, staging, and planning of therapy. To assess the value of external localization of the site or sites of abnormal uptake in a rib as a guide for open rib biopsy, 10 patients (7 men, 3 women; age range, 34 to 68 years) with known or suspected malignancy were studied. With reference to the oscilloscope image, a cobalt 57 marker was placed on the skin overlying the focus of increased uptake, and the area of increased activity was marked on the skin as a guide to surgical resection. Of ten resected ribs, four showed metastatic disease and five had fractures. (One patient underwent two external marking procedures and two surgical procedures.) Rib biopsy was not performed in 1 patient because prior to the surgical procedure, a small subcutaneous nodule adjacent to the skin marker was excised and confirmed to be carcinoma. Appropriate courses of management (operation, irradiation, chemotherapy) were taken after the biopsies. The surgeon responsible for the biopsy should be present during the skin-marking procedure, and the area beneath the scapula and the region adjacent to the spine should be avoided. Our results indicate that the technique is a very useful aid for approaching open rib biopsies more precisely.

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.

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

Lymphescintigraphy has become a standard procperative 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.MethodsEleven 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.ResultsLinear 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.ConclusionsBecause 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%.

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 patients 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.