Optimization of Ordered Subset Expectation Maximization Parameters for Image Reconstruction in Tc-99m Methoxyisobutylisonitrile Myocardial Perfusion SPECT and Comparison with Corresponding Filtered Back Projection-Reconstructed Images.

PURPOSE OF THE STUDY: To establish the most appropriate ordered subset expectation maximization (OSEM) parameters for image reconstruction in Tc-99m methoxyisobutylisonitrile (MIBI) myocardial perfusion SPECT (MPS) and comparison with corresponding filtered back projection (FBP)-reconstructed images. METHODS: A total of 99 stress-rest MPS studies (47 normal and 52 abnormal) were retrospectively analyzed using 16 different combinations of iterations and subsets. Images were reconstructed both with and without postreconstruction Butterworth filter (cutoff frequency and order for stress: 0.4 and 10 and for rest: 0.52 and 5, respectively) for each combination. A total of 3168 images were evaluated qualitatively by two nuclear medicine physicians on a scoring scale of 1-4. Best visual quality image iteration-subset combination was determined for each patient both with and without Butterworth filter and was further compared with FBP-reconstructed image. The interobserver agreement was obtained using kappa statistics. RESULTS: The best quality images were obtained using a combination of four iterations and six subsets for both with and without Butterworth filter. The value of kappa for interobserver agreement for OSEM images with Butterworth filter was 0.570 and for OSEM images without Butterworth filter was 0.857. On comparison, FBP images were better than OSEM-reconstructed images without Butterworth filter (P < 0.0001 calculated using Fisher's exact test) with substantial agreement (kappa = 0.628). However, OSEM-reconstructed images with Butterworth filter were better than FBP images and showed moderate agreement (kappa = 0.486). CONCLUSION: The most appropriate OSEM reconstruction parameter in Tc-99m MIBI MPS is 4-iteration and 6-subset combination. FBP-reconstructed images were better than the images reconstructed with OSEM without postreconstruction Butterworth filter. However, OSEM-reconstructed image with Butterworth filter was better than FBP images.

Unusual Presentation of Rare Cardiac Tumor: The Role of F-18-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography.

Primary cardiac tumors are rare with angiosarcoma being the most common among malignant cardiac tumor. We present a case of 30-year-old female patient in whom F-18-fluorodeoxyglucose positron emission tomography/computed tomography demonstrated a necrotic mass in right atrium with multiple fluorodeoxyglucose avid lesions in both upper and lower alveolus, liver, multiple bones, and bilateral lungs. Patient underwent biopsy from gum swelling which revealed metastatic angiosarcoma.

Role of (18)F-FDG PET-CT in Monitoring the Cyclophosphamide Induced Pulmonary Toxicity in Patients with Breast Cancer - 2 Case Reports.

Drug induced pulmonary toxicity is not uncommon with the use of various chemotherapeutic agents. Cyclophosphamide is a widely used chemotherapeutic drug in the treatment of breast cancer. Although rare, lung toxicity has been reported with cyclophosphamide use. Detection of bleomycin induced pulmonary toxicity and pattern of (18)F-fluorodeoxyglucose ((18)F-FDG) uptake in lungs on fluorodeoxyglucose positron emission tomography-computed tomography ((18)F-FDG PET-CT) has been elicited in literature in relation to lymphoma. However, limited data is available regarding the role of (18)F-FDG PET-CT in monitoring drug induced pulmonary toxicity in breast cancer. We here present two cases of cyclophosphamide induced drug toxicity. Interim (18)F-FDG PET-CT demonstrated diffusely increased tracer uptake in bilateral lung fields in both these patients. Subsequently there was resolution of lung uptake on (18)F-FDG PET-CT scan post completion of chemotherapy. These patients did not develop significant respiratory symptoms during chemotherapy treatment and in follow up.

PSMA Expression in Papillary Thyroid Carcinoma: Opening a New Horizon in Management of Thyroid Cancer?

Prostate-specific membrane antigen (PSMA) is a type 2 transmembrane protein highly expressed in prostate cancer cells. We present the case of a 50-year-old man with metastatic papillary carcinoma of the thyroid, with rising thyroglobulin level and negative whole-body radioiodine scan after total thyroidectomy. Considering the limited treatment options available, it was decided to perform Ga-PSMA-HBED-CC PET/CT scan. It revealed intense radiotracer uptake in mediastinal and left supraclavicular lymph nodes, brain metastases, bilateral lung nodules, and skeletal sites. Patient also underwent F-FDG PET/CT. It demonstrated similar findings; however, the number of lesions detected in brain was less compared with Ga-PSMA PET/CT.

Radioiodine therapy under rhTSH for follicular thyroid carcinoma with sellar metastasis and non-rising TSH.

Metastasis to the pituitary gland/sella turcica is an uncommon complication of thyroid cancer. Treating this condition is a challenge in the setting of pituitary insufficiency due to this lesion, and recombinant human thyroid-stimulating hormone (rhTSH) stimulation becomes critically essential. We present a rare case of an 82-year-old female patient with follicular carcinoma of the thyroid with metastasis to the sella turcica in addition to multiple skeletal and lung metastases. MRI of the brain showed a hypointense suprasellar lesion on T 1 weighted images. The thyroid-stimulating hormone level remained persistently low even 4 weeks after thyroidectomy. A whole-body pertechnetate scan could not localize any abnormal tracer uptake and radioactive iodine uptake was also persistently low. The patient did not have symptoms related to pituitary involvement but TSH and early morning adrenocorticotrophic hormone levels were low. After thorough discussion with the neurosurgeon and radiotherapist, it was decided to start the patient on high-dose radioiodine treatment. Persistently low TSH level was a concern for starting radioiodine therapy. In view of this clinical context, rhTSH stimulation was used to achieve adequate TSH levels prior to radioiodine therapy. Subsequently, the patient was treated with 3.7 GBq (100 mci) of high-dose radioiodine. A post-therapy scan demonstrated radioiodine concentration in the thyroid bed remnant, multiple skeletal lesions and the sellar region. Thus, the use of rhTSH was critical in the management of this patient. It helped in radioiodine treatment by stimulating radioiodine uptake in the remnant and at the metastatic sites.