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.

18-F Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography of a Large Inflammatory-Hepatocellular Adenoma.

We report a case of an 81-year-old male evaluated for a liver space-occupying lesion. US-guided biopsy and immunohistochemistry were suggestive of hepatocellular adenoma (HCA)-inflammatory (with telangiectasia). Serial 18-F fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography scans revealed a heterogeneously enhancing hypermetabolic mass in the right lobe of the liver, remaining stable for a span of 3 years. This case highlights that benign rare tumors of the liver such as HCA can be intensely FDG avid and that uptake cannot conclude its malignant transformation.

Posterior Reversible Encephalopathy Syndrome: Pattern on 18F-Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography Correlated with Magnetic Resonance Imaging in Pediatric Hypertensive Encephalopathy.

Posterior reversible encephalopathy syndrome (PRES) is characterized clinically by headache, seizures, vomiting, altered mental status, and blurred vision. However, with overlapping and atypical clinical symptoms, PRES becomes a diagnostic challenge. We describe the imaging findings of PRES in magnetic resonance imaging and 18F-fluorodeoxyglucose positron emission tomography-computed tomography in an 11-year-old child who presented with features of hypertensive encephalopathy.

Prospective evaluation of 68Ga-DOTANOC positron emission tomography/computed tomography and 131I-meta-iodobenzylguanidine single-photon emission computed tomography/computed tomography in extra-adrenal paragangliomas, including uncommon primary sites and to define their diagnostic roles in current scenario.

AIM: To evaluate Ga-DOTANOC positron emission tomography/computed tomography (PET/CT) and I-meta-iodobenzylguanidine single-photon emission computed tomography/computed tomography (131I-MIBG SPECT/CT) in patients with paragangliomas, including uncommon primaries. METHODS: Ninety patients were prospectively enrolled, and both scans were done within 2 weeks of each other. Lesions were grouped as Head/neck, abdominal, uncommon primary paraganglioma, and metastatic lesions. In most histopathology was used as reference standard. RESULTS: PET/CT had sensitivity, specificity, positive predictive value, negative predictive value and accuracy of 97%, 94%, 99%,88%,97% respectively on patient wise analysis (90) and 98%, 94%, 99%, 85% and 97% respectively on lesion wise analysis (149). Comparison with MIBG SPECT/CT: Significant difference in sensitivities noted (PET/CT-98%, I-131 MIBG -39%) (P < 0.001), however, no significant difference in specificities (94% and 100%, respectively). Group-wise analysis: Head/Neck: Significant difference noted between PET/CT (sensitivity 100%) and I-131 MIBG SPECT/CT (sensitivity 22%) (P = 0.001). Abdominal: No significant difference noted in sensitivities and specificities of PET/CT and I-131 MIBG SPECT/CT. Uncommon paraganglioma: PET/CT detected 10 of 11, while I-131 MIBG detected only 2 of 11 uncommon paraganglioma. Metastatic sites: Significant difference noted between PET/CT (sensitivity 97%) and I-131 MIBG SPECT/CT (sensitivity 33%) (P < 0.0001). CONCLUSION: The study demonstrates high diagnostic accuracy of Ga-DOTANOC PET/CT and superiority over I MIBG SPECT/CT for evaluation of extra-adrenal paraganglioma. The current diagnostic role of I-131 MIBG seems limited to abdominal paragangliomas and for theranostic purpose.

Scar arcoidosis on 18F-FDG PET/CT.

18F-labeled fluoro-2-deoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) is an important imaging modality in the clinical workup of patients with chronic inflammatory disorders which present quite often with a fever of unknown origin. Sarcoidosis is a multisystem chronic inflammatory disorder with a wide clinical spectrum that can involve different organs. The diagnosis of sarcoidosis is usually based on the observation of noncaseating granulomas in biopsy specimens and exclusion of other granulomatous diseases. Skin involvement can occur in 20-25% of sarcoidosis cases. However, scar involvement in sarcoidosis is a rare condition. Herein, we present a case of multisystem sarcoidosis in a 45-year-old woman, who was previously treated with steroids and was in remission for 8 months. The patient presented with multiple skin nodules on the chest and back, a history of intermittent fever, headache, and mild itching at the abdominal scar site for 3 months. Blood investigations revealed elevated serum angiotensin-converting enzyme levels. The 18F-FDG PET/CT revealed a metabolically active involvement of the cutaneous tissue (posthysterectomy scar), apart from other sites of involvement. Biopsy of the scar site revealed multiple epithelioid cell granulomas with giant cells surrounding the collagenous fibers of the scar tissue.

Tracer Accumulation in Relation to Venous Thrombus on 18F-DOPA PET/CT in a Case of Persistent Hyperinsulinemic Hypoglycemia of Infancy.

18F-DOPA PET/CT is commonly done in patients with persistent hyperinsulinemic hypoglycemia of infancy (PHHI) to look for any focal lesion in the pancreas. We present the findings in a 20-day-old neonate with PHHI who underwent 18F-DOPA PET/CT. The scan showed diffuse uptake in the pancreas with no focal lesion, physiologic excretion into the genito-urinary system, and interestingly tracer accumulation was seen in the inferior vena cava and ilio-femoral veins which is a non-physiological site for tracer accumulation. The uptake corresponded to a large venous thrombus which was confirmed by a venous Doppler.

Malignant Peripheral Nerve Sheath Tumor With Bilateral Adrenal Metastases: Role of 18F-FDG PET/CT in Response Assessment to Tyrosine Kinase Inhibitor and Liposomal Doxorubicin.

MPNSTs (malignant peripheral nerve sheath tumors) are a highly malignant group of soft tissue sarcomas and carry a very poor prognosis. Metastasis to bilateral adrenal glands is very rare in such group of neoplasms. We discuss a case of 85-year-old man who was diagnosed with MPNST from prevertebral mass with metastases to bilateral adrenal glands and bone marrow from the beginning and role of serial F-FDG PET/CT scans in response assessment first to sunitinib (tyrosine kinase inhibitor) and then to liposomal doxorubicin.

Comparison of the renal dynamic scan performed with 99mTc-L,L-EC and 99mTc-MAG3 in children with pelviureteric junction obstruction.

The aim was to compare the renal dynamic scan (RDS) performed with technetium-99-L,L-ethylene dicysteine (Tc-L,L-EC) and technetium-99-mercaptoacetyltriglycine (Tc-MAG3) in children with pelviureteric junction (PUJ) obstruction. A retrospective study was carried out and children with PUJ obstruction who had RDS performed with both Tc-L,L-EC and Tc-MAG3. Children with any intervention in between the two scans or a gap of more than 2 months in between renal scans were excluded. The dose of each radiotracer used was 0.1 mCi/kg (3.7 MBq/kg), with a minimum dose of 1 mCi (37 MBq). RDS was performed using the F+0 protocol. The differential renal function, Tmax, T1/2, drainage pattern, and hepatic uptake of the radiotracer were recorded and compared. A Bland-Altman plot was used to assess agreement between the two radiotracers. Sixteen children were included in the study. A total of 18 obstructed and 14 normal renal units were available to us for study. The values of differential renal function as well as Tmax and T1/2 of the two radiotracers were in agreement. In three obstructed kidneys in which T1/2 on Tc-MAG3 was greater than 20 min, Tc-L,L-EC showed T1/2 values of 13.3 min or less. Tc-L,L-EC showed nonobstructive drainage in three patients who had shown partial obstruction on Tc-MAG3 scan. The hepatic uptake of Tc-L,L-EC was also lower compared with Tc-MAG3. To conclude Tc-L,L-EC is a useful radiotracer for the evaluation of children with PUJ obstruction, with better assessment of drainage and lower hepatic uptake compared with Tc-MAG3.

Can Early Dynamic Positron Emission Tomography/Computed Tomography Obviate the Need for Postdiuresis Image in 68Ga-PSMA-HBED-CC Scan for Evaluation of Prostate Adenocarcinoma?

INTRODUCTION: Forced diuresis technique is often adopted to wash out the high amount of urinary radioactivity that masks the foci of abnormal uptake in the pelvic region on 68Ga-PSMA-HBED-CC positron emission tomography/computed tomography (PET/CT) scan in prostate cancer (PC) patients. However, this method is time-consuming, makes the patient non/less compliant, and is not feasible in patients with renal dysfunction. We hypothesized that early dynamic imaging can obviate the need for a postdiuresis view as the urinary activity is expected to be low at the time. MATERIALS AND METHODS: A total of 20 biopsy-proven PC patients who were referred to our department for a 68Ga-PSMA PET/CT for staging/restaging were prospectively studied. Dynamic PET/CT was done with on table intravenous (i.v.) injection of 2-3 mCi (74-111 MBq) of the radiotracer. Dynamic images were acquired over the pelvis with a frame time of 1 min for 10 min. Static images of 2 min/bed position were acquired between 45 and 60 min p.i. The patients were then administered i.v. furosemide and encouraged water intake and frequent urination. A static view of pelvic region was acquired at 5 min/bed at 120 min p.i. A three-dimensional volume of interest (3D-VOI) was plotted on the primary lesion, bladder, involved nodes if any, pelvic bones at involved and uninvolved sites, gluteal muscles, and artery. The sentence seems fine. This was to generate the Time activity curve for analysis. RESULTS: Nine patients were referred for staging and 11 for restaging. Mean age of 20 patients was 64.6 years, and median prostate-specific antigen level was 21.4 ng/ml (range: 0.05-2180). Prostatic lesion was present in 20 patients, nodal involvement in 8, and bone involvement in 10 patients. Median maximum standardized uptake value (SUVmax) of the prostatic lesion (P) showed an ascending trend: 5.31 at 5 min, 10.65 at 60 min, and 10.52 at 120 min p.i. At the same time, median SUVmax of the bladder (B) also progressed steeply and then decreased postdiuresis: 1.01 at 5 min, 24.6 at 60 min, and 6.88 at 120 min. Despite forced diuresis, the bladder activity remained higher than that during early dynamic imaging. Median prostate-to-bladder (P/B) ratio was highest during early dynamic imaging at 5 min p.i. was 5.17, while at 60 min, P/B ratio was 0.42 (P = 0.002) and, at 120 min, it was 1.27 (P = 0.009). Further, all the nodal and bone lesions were clearly visualized on early dynamic images. CONCLUSION: The study results suggest that early dynamic imaging performs better than a postdiuresis view in terms of delineation of prostatic and regional lesions on 68Ga-PSMA scan. Further, it saves time and the patients are more compliant to this technique.

Incidental Detection of Parathyroid Adenoma on Somatostatin Receptor PET/CT and Incremental Role of 18F-Fluorocholine PET/CT in MEN1 Syndrome.

Multiple endocrine neoplasia type 1 (MEN1) syndrome is characterized by combined occurrence of tumors of endocrine glands including the parathyroid, the pancreatic islet cells, and the anterior pituitary gland. Parathyroid involvement is the most common manifestation and usually the first clinical involvement in MEN1 syndrome, followed by gastroentero-pancreatic neuroendocrine tumors (NETs). Here we present a case where the patient initially presented with metastatic gastric NET and a single parathyroid adenoma was detected incidentally on 68Ga-DOTANOC PET/CT done as part of post 177Lu-DOTATATE therapy (PRRT) follow-up. Further 18F-fluorocholine PET/CT showed four adenomas for which the patient subsequently underwent subtotal parathyroidectomy.

Somatostatin Receptor PET/CT Features of Carcinoid Heart Disease.

We present the case of a 35-year-old woman with metastatic neuroendocrine tumor undergoing treatment with long-acting octreotide and Lu-DOTATATE therapy. We present features of carcinoid heart disease on Ga-DOTANOC PET/CT, which revealed dilated right atrium, pericardial effusion, ascites, and congestive hepatopathy apart from the metastatic lesions in the liver. The scan cardiac findings were confirmed by echocardiography. This highlights the significance of identifying such patients early because additional management is required for carcinoid heart disease per se and a cautious approach is needed in administering amino acid infusion during PRRT that can result in fluid overload.

Prostate-Specific Membrane Antigen Expression in Adrenocortical Carcinoma on 68Ga-Prostate-Specific Membrane Antigen PET/CT.

We present here a case of metastatic adrenocortical carcinoma with bilateral lung nodules. The patient had been treated with mitotane therapy initially and then was later referred for chemotherapy. There was progression of disease noted on the F-FDG PET/CT. Ga prostate-specific membrane antigen (PSMA) PET/CT was planned to explore the possibility of future treatment with Lu-DKFZ-PSMA-617. It revealed peripheral increased uptake of Ga-HBED-CC-PSMA equal to liver uptake.

68Ga-Prostate-Specific Membrane Antigen PET/CT in Triple-Negative Breast Cancer.

The prostate-specific membrane antigen (PSMA) is a transmembrane protein with elevated expression in prostate cancer cells. Breast cancer also shows PSMA expression. We present the case of a 30-year-old woman with triple-negative bilateral breast carcinoma who underwent bilateral mastectomy, chemotherapy, and radiotherapy. She developed a left chest wall and liver recurrence after primary therapy. Her recurrent disease was also triple-negative. In view of the known poor prognosis and very limited therapeutic options, we performed Ga-PSMA PET/CT scan to explore the possibility of PSMA-based therapy as a future option after exhausting standard-of-care treatments.

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.