Pre-clinical Positron Emission Tomography Reconstruction Algorithm Effect on Cu-64 ATSM Lesion Hypoxia.

OBJECTIVE: Application of distinct positron emission tomography (PET) scan reconstruction algorithms can lead to statistically significant differences in measuring lesion functional properties. We looked at the influence of two-dimensional filtered back projection (2D FBP), two-dimensional ordered subset expectation maximization (2D OSEM), three-dimensional ordered subset expectation maximization (3D OSEM) without 3D maximum a posteriori and with (3D OSEM MAP) on lesion hypoxia tracer uptake using a pre-clinical PET scanner. METHODS: Reconstructed images of a rodent tumor model bearing P22 carcinosarcoma injected with hypoxia tracer Copper-64-Diacetyl-bis (N4-methylthiosemicarbazone) (i.e. Cu-64 ATSM) were analyzed at 10 minute intervals till 60 minute post injection. Lesion maximum standardized uptake values (SUVmax) and SUVmax/background SUVmean (T/B) were recorded and investigated after application of multiple algorithm and reconstruction parameters to assess their influence on Cu-64 ATSM measurements and associated trends over time. RESULTS: SUVmax exhibited convergence for OSEM reconstructions while ANOVA results showed a significant difference in SUVmax or T/B between 2D FBP, 2D OSEM, 3D OSEM and 3D OSEM MAP reconstructions across all time frames. SUVmax and T/B were greatest in magnitude for 2D OSEM followed by 3D OSEM MAP, 3D OSEM and then 2D FBP at all time frames respectively. Similarly SUVmax and T/B standard deviations (SD) were lowest for 2D OSEM in comparison with other algorithms. CONCLUSION: Significantly higher magnitude lesion SUVmax and T/B combined with lower SD were observed using 2D OSEM reconstruction in comparison with 2D FBP, 3D OSEM and 3D OSEM MAP algorithms at all time frames. Results are consistent with other published studies however more specimens are required for full validation.

FLT PET-CT in evaluation of treatment response.

PURPOSE: Review published studies to investigate the value of clinical 3-deoxy-3-(18)F-fluorothymidine (FLT) positron emission tomography (PET) in predicting response to treatment. MATERIALS AND METHODS: Interrogate databases to identify suitable publications between 2007 and 2013 with a minimum of five patients. Articles within the inclusion criteria were reviewed with major findings reported leading to a descriptive analysis of FLT PET in therapy response. RESULTS: Lesions investigated included glioma, head and neck, esophageal, lung, breast, gastric, renal, rectal, sarcomas, germ cell, lymphomas, leukemia, and melanoma resulting in a total of 34 studies analyzed. A variety of therapies were applied and dissimilar PET protocols were widespread making direct comparison between studies challenging. Though baseline, early and late therapy scans were popular particularly in chemotherapy regimes. Most studies investigated showed significantly reduced FLT uptake during or after therapy compared with pretreatment scans. CONCLUSION: Current evidence suggests FLT PET has a positive role to play in predicting therapy response especially in brain, lung, and breast cancers where good correlation with Ki-67 is observed. However, careful attention must be placed in undertaking larger clinical trials where harmonization of scanning and analysis protocols are strictly adhered to fully assess the true potential of FLT PET in predicting response to treatment.

Co-existent Paget's Disease of the Bone, Prostate Carcinoma Skeletal Metastases and Fracture on Skeletal Scintigraphy-Lessons to be Learned.

UNLABELLED: Bone scintigraphy, despite being non-specific, is a very sensitive and simple investigation for patients with active Paget's disease of the bone. Skeletal metastases and Paget's disease may co-exist in the elderly patients as both conditions are commonly seen in this age group. Clinical and radiological correlation may help to improve the diagnostic specificity of a bone scintigram. We report a patient in whom concurrent Paget's disease and a rib fracture became evident only on repeat scintigraphy following successful treatment of prostate carcinoma skeletal metastases. CONFLICT OF INTEREST: None declared.

Oesophageal conduit - a cause of diffuse mediastinal uptake on thyroid scintigraphy.

UNLABELLED: 99mTc-pertechnetate scintigraphy plays an essential role in the management of a variety of thyroid and parathyroid disorders. The authors report an unusual case of mediastinal tracer distribution of 99mTc-pertechnetate and 99mTc-MIBI in relation to an oesophageal conduit following oesophago-gastrectomy and reconstructive surgery on thyroid scintigraphy. This is a rare but important cause of diffuse mediastinal uptake on thyroid scintigraphy. An awareness of abnormal anatomy as well as altered physiological tracer uptake would help to avoid any diagnostic pitfall. CONFLICT OF INTEREST: None declared.

FDG injection site extravasation: potential pitfall of misinterpretation and missing metastases.

18F-FDG PET/CT plays an important role in the management of non-small-cell lung cancers (NSCLC). The treatment options for NSCLC depend upon the initial staging of the disease. The authors report a case with a potential pitfall of overlooking a site of FDG uptake as radiopharmaceutical extravasation at an injection site. The PET/CT demonstrated a T2a N2 bronchial carcinoma, with a solitary focus of FDG uptake at the left antecubital fossa where FDG was administered. Careful interpretation of the images reveals a solitary skeletal metastasis in the left proximal ulna, which makes the disease stage IV rather than IIIA, leading to a significant difference in treatment.

Both native and ectopically transplanted hearts shown on FDG PET/CT in a PTLD patient.

Posttransplant lymphoproliferative disorder (PTLD) is one of the unfortunate complications of immunosuppression after allograft transplantation. 18F-FDG PET/CT plays an important role in the diagnosis and management of PTLD. The authors report a PET/CT scan of a young woman who received a heterotopic cardiac transplant, demonstrating 2 functional hearts in the thorax. The scan also demonstrates a small-volume mediastinal lymphadenopathy caused by the PTLD/B-cell lymphoma, subsequently proven by mediastinoscopic biopsy.

Unexpected Significantly Reduced FDG Uptake in the Cerebrum Compared Against Normal Liver Uptake in a Dying Patient.

UNLABELLED: F-18 FDG PET-CT scanning plays an important role in the management of fever of unknown origin (FUO). Some elderly patients with FUO can be in their terminal stage of life. An elderly woman was referred for a PET-CT scan to find the etiology of FUO. The scan was inconclusive but showed significantly reduced FDG uptake in the brain and heart, despite normal physiological uptake in the liver and bowel. The patient deceased within the hour post scan. Contrary to common belief, we have shown that cerebral glucose metabolism via cerebral perfusion may be compromised before hepatic and bowel perfusion in a dying patient. CONFLICT OF INTEREST: None declared.

Clinical significance of scintigraphic rapid gastric emptying.

OBJECTIVES: To analyse our results of gastric-emptying scintigraphy in relation to presenting symptoms, and examine in detail the clinical significance of rapid gastric emptying (RGE). MATERIALS AND METHODS: Results of 642 consecutive patients who underwent a solid gastric-emptying scintigraphy in our department over an 11-year period were retrospectively reviewed with particular emphasis to the presenting symptoms and the clinical profile of patients, especially of those who showed an accelerated pattern of emptying. RESULTS: Seventy (11%) patients were clinically suspected to have a RGE and 572 (89%) patients had presumed gastroparesis. Gastric emptying was found to be normal in 290 (45%), rapid in 182 (28%) and delayed in 170 (27%) patients. Normal, rapid and delayed gastric emptying were seen, respectively, in 17 (24%), 48 (69%) and five (7%) patients with the clinical suspicion of dumping and 273 (48%), 134 (23%) and 165 (29%) patients with suspected gastroparesis. The positive predictive value of clinical suspicion for RGE was 62%, whereas the positive predictive value of delayed gastric emptying was 29%. Of the 182 patients with RGE, 144 (79%) were found to have no obvious explanation for this result; reactive hypoglycaemia was present in a quarter of these patients, but diarrhoea was seen only in 3%. CONCLUSION: Upper gastrointestinal symptoms have a poor clinical specificity to the actual rate of gastric emptying on scintigraphy. Diarrhoea as a symptom does not appear to be associated frequently with RGE, but our results confirm its relationship with hypoglycaemia. The majority of patients with a rapid emptying on gastric-emptying scintigraphy have no identifiable cause for an accelerated motility. Scintigraphic gastric-emptying studies provide a reliable and noninvasive method of investigation in patients where conventional investigations have failed to establish the cause of upper gastrointestinal dysfunction.

Detection of extensive melorheostosis on bone scintigram performed for suspected metastases.

Melorheostosis is a rare but benign disorder characterized by asymmetric osteosclerotic dysplasia. Radiographic appearances are characteristic and described as "melting wax flowing down a candle." This disorder may involve more than one bone contiguously across the joints following a sclerotomal distribution. It is often asymptomatic but occasionally presents with pain and contractures. The authors report accidental detection of bilateral upper and lower limb melorheostosis in an elderly woman with the history of breast cancer and recent onset of low back pain, which was referred for a bone scintigram for suspected metastases. The images showed bilateral femoral and tibial melorheostosis, which was subsequently confirmed on plain radiograph and by clinical follow-up.

Solitary phalangeal metastasis of renal cell carcinoma on bone scintigram.

Renal cell carcinoma is known to cause lytic metastasis at various sites including axial and appendicular skeleton. However, it is unusual to find an isolated metastasis of renal cell carcinoma in the distal extremity on bone scintigraphy. A 70-year-old woman with renal cell carcinoma was referred to the Nuclear Medicine Department for a bone scintigram to exclude metastasis. The whole-body planar images were unremarkable, but the local views of the hands demonstrated a solitary metastasis in the middle phalanx of the finger. This rare experience illustrates the need for including local views of extremities in a standard whole-body study.

What is the significance of solitary bony abnormalities on bone scintigrams of children with malignancy?

This investigation was undertaken to evaluate the significance of solitary bony abnormalities on bone scintigrams of children with known or suspected malignancy. A total of 215 bone scans were performed in 183 children in order to look for possible metastasis over a 10-year period. Forty-nine scans (22.8%) were found to have single lesions, of which 18 were due to uptake at the primary site and were excluded from further consideration. Of the remaining 31 lesions, 13 (41.9%) were confirmed as metastases, 17 lesions were proved to be benign, and 1 indeterminate. Solitary hot spots in children with known or suspected malignancy are common and therefore have to be taken seriously due to their higher malignant potential.