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Paige B Clark,
Michael J Plaza, Jonathan Kraas,
Nicole Burbank,
Allen W Elster,
Pradeep Garg,
Sudha Garg,
H Donald Gage,
Jorge Calles-Escandon,
Janice D Wagner,
Kathryn Morton
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ABSTRACT: Pancreatic neuronal changes associated with beta cell loss in type 1 diabetes mellitus are complex, involving, in part, parasympathetic mechanisms to compensate for preclinical hyperglycemia. The parasympathetic neurotransmitter acetylcholine (ACh) mediates insulin release via M3 muscarinic receptors on islet beta cells. The vesicular ACh transporter (VAChT) receptor has been shown to be a useful marker of cholinergic activity in vivo. The positron emission tomography (PET) radiotracer (+)-4-[(18)F]fluorobenzyltrozamicol ([(18)F]FBT) binds to the VAChT receptor on presynaptic cholinergic neurons and can be quantified by PET. The compound 4-diphenylacetoxy-N-methylpiperidine (4-DAMP), available in a tritiated form, binds to M3 muscarinic receptors on beta cells and is a potential target for assessing pancreatic beta cell mass. In this study, we investigate the feasibility of dual radiotracer analysis in identifying neurofunctional changes that may signify type 1 diabetes mellitus in its early preclinical state.
Ex vivo determinations of pancreatic uptake were performed in prediabetic nonobese diabetic mice and controls after intravenous injection of [(18)F]FBT or 4-[(3)H]DAMP. Beta cell loss in prediabetic mice was confirmed using immunohistochemical methods.
[(18)F]FBT uptake was significantly higher in prediabetic pancreata than controls: 3.22 +/- 0.81 and 2.51 +/- 1.04, respectively (P < 0.03). 4-[(3)H]DAMP uptake was significantly lower in prediabetic pancreata than controls: 0.612 +/- 0.161 and 0.968 +/- 0.364, respectively (P = 0.01).
These data suggest that a combination of radiotracer imaging agents that bind to neuronal elements intimately involved in insulin production may be an effective method of evaluating changes associated with early beta cell loss using PET.
Diabetes Technology & Therapeutics 02/2009; 11(2):107-11. · 1.93 Impact Factor
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ABSTRACT: Joubert syndrome (JS) is characterized by absence of decussation of both corticospinal tracts and superior cerebellar peduncles (SCP). Our hypothesis was that evidence for absence of SCP decussation may be found on routine brain MRI studies. Midsagittal T1-weighted images from 20 JS patients and 30 age-matched controls were retrospectively reviewed. An ill-defined area of lower T1 signal in the inferior midbrain was considered the sign of SCP decussation, and its presence or absence was noted. Fractional anisotropy (FA) maps were obtained in three JS patients and four controls. The SCP decussation was not visualized in any subject under 30 months of age. In subjects above 30 months of age the sign of the SCP decussation was absent in all 6 JS patients and present in all 16 controls. FA maps confirmed the absence of the SCP decussation in the JS patients. The SCP decussation is well seen on routine brain MRI studies in controls older than 30 months of age and absent in all JS patients, confirming the proposed lack of commissural fibers in JS, and accounting in part for the molar tooth sign.
American Journal of Medical Genetics Part A 07/2008; 146A(11):1389-94. · 2.39 Impact Factor
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ABSTRACT: OBJECTIVE: The purpose of this article is to discuss and show examples of the PET appearance of common brain abnormalities that radiologists encounter when interpreting whole-body 18F-FDG PET examinations of cancer patients. CONCLUSION: Knowledge of the PET appearance of various brain abnormalities can yield diagnostically relevant information in cancer patients. Detection of brain abnormalities on whole-body PET often requires adjusting window settings to reduce the intensity of normal brain FDG activity. Often, close correlation of PET/CT and MRI with clinical history offers the most complete radiologic diagnosis.
American Journal of Roentgenology 04/2007; 188(3):866-73. · 2.78 Impact Factor
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Seminars in Roentgenology 04/2007; 42(2):92-101. · 0.66 Impact Factor
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ABSTRACT: Evaluation of newly diagnosed patients with melanoma for metastasis is requisite to treatment planning. The reported diagnostic yield of whole-body conventional radiological imaging in initial staging of patients with melanoma is low. However, the diagnostic yield of positron emission tomography (PET) for distant metastases is unclear.
There is no utility of PET as part of a routine metastatic survey in patients with T2 to T4 melanoma.
Retrospective review of a cohort study between December 1998 and July 2004.
University hospital tertiary care center. Patients and
There were 64 patients with T2 to T4 melanomas who underwent PET for detection of occult metastases at our institution. All patients underwent surgical excision of the primary lesion and sentinel lymph node dissection. Data included were pathologic findings of the primary lesion and sentinel lymph nodes, laboratory data, and radiological reports. None of the patients had clinically suspected regional or distant metastases prior to PET. The diagnostic yield of PET was evaluated through retrospective analysis. Positive scans were then correlated for accuracy with follow-up imaging, biopsy, and clinical information when available.
Positron emission tomography did not reveal occult distant metastases in any of the patients. Positron emission tomographic scans showed no abnormalities in 94% of these patients. In 2 patients (3%), false-positive findings were reported on PET (muscular activity and intranodal melanocytic nevocellular inclusion). Further, PET was not useful in predicting regional lymph node metastases. Nineteen of 64 patients had positive sentinel lymph nodes, and only 2 (11%) were identified on PET. Overall, PET did not change clinical management in any of the patients.
This study suggests no utility for PET in the detection of occult metastases in patients at initial diagnosis of melanoma. Omission of PET imaging from preoperative evaluations for patients with melanoma is recommended.
Archives of Surgery 04/2006; 141(3):284-8. · 4.24 Impact Factor
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ABSTRACT: Approximately 5 to 10% of parathyroid adenomas are located within the thin, fibrous capsule of the thyroid gland. These subcapsular adenomas can complicate minimally invasive parathyroidectomy. The small incision used in this procedure limits the view of the surgical bed. Palpation is less sensitive when the adenoma is covered by the thyroid capsule. If a subcapsular parathyroid adenoma can be identified on preoperative parathyroid scintigraphy, nuclear medicine physicians can recommend exploration of the thyroid capsule early, leading to an easier, more efficient operation. The objective of this observational study was to identify the scintigraphic appearance of subcapsular parathyroid adenomas.
A total of 109 patients with primary hyperparathyroidism underwent preoperative dual-phase Tc-99m sestamibi parathyroid scintigraphy at our tertiary care center from October 2002 to March 2004. Tc-99m pertechnetate was used as a supplemental technique when deemed necessary for optimal interpretation. Retrospective chart review identified 16 surgically proved subcapsular parathyroid adenomas. Parathyroid scintigraphy was reviewed.
Subcapsular parathyroid adenomas tend to conform to the expected shape of the thyroid gland. In this small series, subcapsular parathyroid adenomas followed 1 of 3 patterns on lateral images: (1) focal convex distortion of the posterior wall of the thyroid, (2) polar lentiform configuration, and (3) compression of the posterior thyroid parenchyma.
Subcapsular parathyroid adenomas often have a distinct appearance on scintigraphy. Preoperative identification of this type of parathyroid adenoma can direct a subcapsular surgical approach, optimizing the efficiency of the minimally invasive parathyroidectomy.
Clinical Nuclear Medicine 05/2005; 30(4):213-7. · 3.67 Impact Factor
