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%.

Brain SPECT artifacts in patients having metallic cranioplasty.

OBJECTIVE: Over the past few years, we have performed several brain SPECT studies on patients who have had previous head trauma that required metallic cranioplasty. Transaxial images showed clearly defined photon-deficient areas extending from the brain tissue into the area of the scalp. To investigate the extent and pattern of this type of artifact, SPECT brain phantom studies were performed and compared with the patient studies. METHODS: SPECT brain phantom studies were performed using various metallic sheets to simulate metallic plates that were used for cranioplasty. RESULTS: Phantom studies using lead to represent tantalum plates were similar to our patient studies; that is, the photon-deficient area in normal brain tissue extended into the area where normal scalp activity would be. There was also increased tracer activity at the periphery of the photon-deficient area that extended to where normal scalp activity would be. This was similar to the patient studies and was not present on the phantom studies done without any metallic sheets present. CONCLUSION: One would expect photon-deficient artifacts caused by radiopaque metallic plates in brain SPECT studies. The patient and phantom studies demonstrate that an increased tracer activity artifact is also present at the periphery of the photon-deficient area that extends into the area of the scalp. Knowing the appearance of this type of artifact caused by radiopaque metallic plates in brain SPECT studies could be beneficial, especially in cases with poor patient history and lacking radiographic correlation.

A simple solution to prevent the loss of radioactive spot markers.

OBJECTIVE: Most nuclear medicine technologists have experienced the misplacing and/or the loss of a radioactive spot marker. We report on a simple solution to prevent or at least minimize the loss of radioactive spot markers. METHODS: One end of a metallic beaded chain was attached to the side of 57Co spot marker using repair putty. The other end of the beaded chain was attached to a lead shield that housed the radioactive source when not in use. RESULTS: This design has allowed easy, unobstructed use of the 57Co spot marker for marking the right or left side and anatomical position during imaging while preventing its loss. CONCLUSION: A radioactive spot marker that is attached to a lead shield by a beaded chain is a simple way to prevent its loss while allowing it to be used easily during imaging.

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.

Myositis ossificans demonstrated by positive gallium-67 and technetium-99m-HMDP bone imaging but negative technetium-99m-MIBI imaging.

Gallium-67-citrate and 99mTc-diphosphate bone imaging agents are localized in myositis ossificans, a tumor-like benign soft-tissue mass that makes it impossible to differentiate between malignant tumor and the infection/inflammatory process. We present such a myositis ossificans patient whose bone and 67Ga-citrate imagings showed increased uptake in the left thigh and two foci of the right gluteal region leading to inconclusive results. Technetium-99m-MIBI imaging showed the absence of substantial uptake in these regions. ACT scan confirmed myositis ossificans. The lack of 99mTc-MIBI uptake in myositis ossificans means that 99mTc-MIBI imaging may be useful in the differential diagnosis.

Detecting strontium-89 removable contamination using a sodium iodide well counter.

UNLABELLED: Monitoring for 89Sr removable contamination is required for incoming DOT-labeled packages and work areas containing radioactivity. However, few nuclear medicine departments are equipped for liquid scintillation counting, which is the preferred method for detecting beta emitters. We investigated using a sodium iodide well counter to detect 89Sr through its bremsstrahlung photon production. METHODS: We used a manufacturer's 89Sr-chloride solution of known concentration and tested various parameters: type of tube, access of tube contents to air, volume of sample, type of wipe material and counting geometry. Liquid scintillation samples also were obtained. RESULTS: Initial counting efficiencies were 0.10-0.14 cpm/dpm for small volume (10-microliter) samples. The various parameters tested had either positive or negative effects on the system's efficiency to detect 89Sr. One set of samples, counted over time, demonstrated a calculated mean half-life of 50.8 days, which is similar to the 89Sr reported half-life of 50.5 days. Liquid scintillation samples demonstrated efficiencies of almost 1.0 cpm/dpm and a calculated mean half-life of 50.8 days, both as expected. CONCLUSION: This study demonstrates that 89Sr removable contamination can be detected sensitively using a sodium iodide well counter, but special considerations must be made when determining the system's counting efficiency.

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.

Hepatic vein dilatation as seen on single photon emission computed tomography (SPECT) of the liver.

An area of photon deficiency in both planar and single photon emission computed tomography (SPECT) images of the liver using 99mTc-Sulfur Colloid was found to be due to a dilated hepatic vein.