Luke I. Sonoda

Clinical significance of scintigraphic rapid gastric emptying.

ObjectivesTo 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 methodsResults 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. ResultsSeventy (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 in170 (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%. ConclusionUpper 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.

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.

I-123 Mibg Uptake in a Gastrointestinal Stromal Tumor (gist)

Abstract: I-123 metaiodobenzylguanidine (MIBG) scintigraphy is the examination of choice for visualizing tumor sites of pheochromocytoma. We report a middle-aged woman with incomplete Carneys Triad (association of pheochromocytoma/paraganglioma, gastrointestinal stromal tumor [GIST], and pulmonary chondromas) in whom a GIST was identified on the basis of its MIBG uptake. She had undergone surgical resection of a pheochromocytoma and postoperatively developed a mass in the epigastrium, which was thought to be recurrence. The lesion was MIBG-positive. However, following surgery, histologic examination of the specimen revealed findings suggestive of GIST.

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.

18F-FDG PET/CT appearances of adult pulmonary blastoma.

(18)F-FDG PET/CT scanning plays an important role in the management of thoracic malignancy. The authors would like to present FDG PET/CT images of a rare thoracic malignancy, pulmonary blastoma in adulthood. The patient had recurrent metastatic disease of previously resected primary pulmonary blastoma. The foci of recurrent metastases in lung, mediastinum, and subcutaneous tissue are intensely FDG-avid.

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.

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.

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: SUVmaxSUVmax or T/B between 2D FBP, 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 SUVmax or T/B between 2D FBP, consistent with other published studies however more specimens are required for full validation.

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

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.

Changes in 18F-FDG PET-CT Appearances of Treated Malignant Melanoma Metastases within the Right Atrium

18F-FDG PET-CT plays an important role in the management of malignant melanoma. Cardiac metastases of melanoma are relatively uncommon, but when present they often manifest with cardiac arrhythmia and cardiac failure. Once treated successfully, lesions in the heart reduce in size and FDG-uptake, while signs of cardiac arrhythmia and cardiac failure may resolve. With a background of normal physiological FDG-uptake in cardiac muscle, a careful observation is required when cardiac metastases are clinically suspected. We report a patient with right atrial metastases of melanoma who presented with new onset atrial fibrillation, and in whom the cardiac lesion reduced in size and FDG-uptake following appropriate treatment, and signs of cardiac arrhythmia spontaneously resolved. The authors believe this is the first set of PET-CT appearances of pretreatment and treated cardiac metastases of melanoma in the literature.