Margarita Núñez

Thyroid imaging with Tc-99m MIBI in patients with solitary cold single nodules on pertechnetate imaging

Thyroid imaging was performed in 30 patients with the standard pertechnetate technique, as well as with Tc-99m MIBI using a double-phase acquisition protocol. All patients had normal thyroid function confirmed by hormone measurements and cold solitary thyroid nodules, which were evaluated by pertechnetate scanning. Tc-99m MIBI scans were reported as showing cold (N = 14), warm (N = 7), or hot (N = 9) nodules. Nodule classification was made according to fine needle aspiration biopsy findings in 20 patients. The remaining 10 proceeded to surgery and had histopathologic confirmation of their lesions. Although all cold nodules with Tc-99m MIBI were cystic, six of the warm nodules were benign lesions. No histologically proven benign nodule was hot with Tc-99m MIBI. Of the hot nodules, seven were suspicious for follicular carcinoma with fine needle aspiration biopsy (N = 3), or had histologically proven papillary carcinoma (N = 4). Delayed images in five of seven of these lesions showed nodular retention of the radiopharmaceutical. In conclusion, double-phase Tc-99m MIBI scanning of the thyroid gland could be helpful in the preoperative assessment of patients with cold solitary thyroid nodules in order to evaluate the malignancy probability of these lesions.

Scintigraphic evaluation of malignant melanoma lesions with Tc-99m tetrofosmin

Two cases of malignant melanoma (primary and metastatic lesions) imaged with Tc-99m tetrofosmin are reported. One patient showed intense uptake in a primary skin lesion of the thorax, and the other patient had accumulation in skin, cerebellum, breast, and lymph node metastases. Like Tc-99m MIBI, Tc-99m tetrofosmin imaging may be of clinical relevance in the evaluation of suspicious skin lesions and in patients with known cutaneous malignant melanoma in the assessment of recurrent disease during follow-up evaluation.

Attenuation correction for lung SPECT: evidence of need and validation of an attenuation map derived from the emission data

PurposeThe aim of our study was to investigate the importance of attenuation correction (AC) in reconstructed and reprojected images on lung SPECT studies.MethodsSimulation studies were undertaken to evaluate the influence of AC on defect-to-normal ratios (D/N), to demonstrate the influence of errors in the correction map values and to detect lung boundaries used for AC. The use of a synthetic map (SM) for AC of the clinical data was also evaluated and the results compared with those obtained with data derived from CT (CTM). Additionally, the role of AC in reprojected SPECT data was assessed and level of noise on the ‘planar-like’ images was measured.ResultsPhantom studies showed that AC markedly affects the D/N ratio. However, variations in µ values typical of those found in clinical studies resulted in relatively small changes in results. Eroded and dilated conditions did not cause any significant effect on D/N. The level of noise in the reprojected images is reduced in comparison with real planar data. Clinical SPECT/CT data reconstructed with AC using CTM and SM showed an excellent correlation between the two methods.ConclusionAC improves D/N in lung SPECT studies, thus potentially enhancing the diagnostic capability of the method. The use of a synthetic map for AC is feasible, avoiding the need for an additional procedure and the increased radiation dose involved. Planar-like images generated from reprojected SPECT data are well matched to normal planar images provided AC is performed and attenuation included in the reprojection.

Evaluation of Patients with Head and Neck Cancer by Means of 99mTc-Glucarate

Preliminary findings have suggested that 99mTc-glucarate has tumor-seeking properties. The purpose of this study was to explore the potential of this tracer to evaluate malignant head and neck tumors by means of SPECT/CT software fusion imaging. Methods: Eleven male patients with advanced head and neck carcinoma were included in the study: 9 with locally advanced disease and 2 with clinical suspicion of local relapse. Scanning started 3–6 h after the injection of 1,110 MBq of 99mTc-glucarate. Planar and SPECT images of the head, neck, and thorax were acquired. Three-dimensional images were also coregistered with CT. Results: We found 99mTc-glucarate uptake in all suspected lesions. SPECT/CT fusion imaging was helpful in all cases for topographically localizing the tracer foci. Conclusion: 99mTc-glucarate can be considered a potential tracer for the evaluation of patients with head and neck tumors.

Tc-99m hynic octreotide SPECT-MRI in brain metastasis of thyroid papillary-insular cancer.

Tc-99m somatostatin analogues are a relatively new imaging tool for different tumors including thyroid carcinoma. We present a case of a papillary and insular thyroid cancer with a I-131 whole body scan suggestive of having clavicle and skull metastasis. Bone scanning confirmed the clavicle lesion but excluded skull metastases leading to the interpretation of a possible radioiodine head contamination. However, Tc-99m octreotide images fused with head MRI allowed us to diagnose and evaluate the extension of a brain metastasis in a patient with no signs or symptoms of endocranial hypertension.

Double-phase scanning of the thyroid gland with Tc-99m MIBI in a patient with a malignant nodule. A case of tracer redistribution?

The authors report on a patient with a malignant papillary thyroid nodule that was cold with Tc-99m pertechnetate and evaluated by double-phase thyroid scintigraphy with Tc-99m sestamibi (MIBI). The images were taken at 15 minutes and 2 hours postinjection. Although nodular MIBI uptake on the early scan was present, it was less intense than the extranodular thyroid tissue. The delayed image showed an inverse relation of uptake, being more intense in the nodular lesion. This scintigraphic pattern could be explained by a slower washout rate of the malignant lesion. However, delayed tracer accumulation cannot be excluded.