Optimal diagnosis by using two-marker studies.
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Central Nervous System Neoplasms↗
Biomedical subjects
Gary T Smith
Publications and source records attributed to Gary T Smith.
Minimally invasive parathyroidectomy: how effective is preoperative sestamibi scanning?
Minimally invasive parathyroidectomy (MIP) guided by preoperative sestamibi scanning has been shown to reduce operative time, hospital stay, and cost in treating primary hyperparathyroidism. However, controversy exists over routine preoperative sestamibi scanning. The purpose of this study was to determine the utility of sestamibi scanning at our institution as part of the MIP protocol and to analyze calcium and parathyroid hormone levels as possible predictors of successful sestamibi scanning. Charts of 37 consecutive patients undergoing MIP at our institution were reviewed, and age, sex, preoperative calcium, and parathyroid (PTH) levels, invasiveness of procedure, and pathologic diagnosis were recorded. Sestamibi scans were reviewed and scored by 4 nuclear medicine faculty based on the level of suspicion for parathyroid adenoma. Neither calcium nor PTH correlated significantly with sestamibi scan score (Spearman coefficient, r = 0.075, P = 0.67 and r = 0.277, P = 0.10, respectively). Receiver-operating-characteristic (ROC) analysis showed sestamibi scanning to have sensitivity and specificity in predicting MIP completion (87% and 68%). Logistic regression showed only sestamibi scan (P = 0.038), not calcium or PTH (P = 0.977 and P = 0.767) to be predictive of MIP completion. In conclusion, sestamibi scanning effectively predicted the ability to perform MIP. However, preoperative calcium and PTH predicted neither sestamibi scan results nor completion of MIP.
Adenoma↗
Optimizing imaging time for improved performance in oncology PET studies.
PURPOSE: The potential for improving the diagnostic performance of static positron imaging tomography (PET) by judiciously choosing optimum post-injection imaging times is investigated. PROCEDURES: Dynamic and whole-body scan data, from 2-deoxy-2-[18F]fluoro-D-glucose (FDG) oncological studies, are analyzed for changing standardized uptake value (SUV) behavior with increasing post-injection times at either single- or multiple-bed positions. Model-based interpretations address d(SUV)/dt, shown to correlate with SUV, and the contrast ratio for a tumor and its surroundings. A method for correcting measurements to a standardized time is given. RESULTS: Both data and model-based equations suggest that starting data acquisition later than the average 55 +/- 15 (SD) minutes post-injection reported in the FDG literature can improve contrast ratios. Considerations for choosing an optimum time from a clinical standpoint are listed. CONCLUSIONS: It is concluded that the appropriate time for each particular protocol can be found with the aid of the information presented here. True optimization, however, remains a complex issue.
Journal Article↗
Characterization of uptake of 2-deoxy-2-[18F] fluoro-D-glucose by fungal-associated inflammation: the standardized uptake value is greater for lesions of blastomycosis than for lymphoma in dogs with naturally occurring disease.
PURPOSE: Based on limited reports, fungal lesions can have remarkably high intensity uptake of 2-deoxy-2-[18F]fluoro-D-glucose (FDG) on positron emission tomography (PET) images. The purpose of this investigation was to compare the standardized uptake value (SUV) of naturally occurring lesions of blastomycosis with the SUV of naturally occurring lymphoma in a series of dogs. PROCEDURES: Five dogs with naturally occurring blastomycosis and three dogs with lymphoma underwent whole-body FDG-PET prior to receiving any treatment for their disease. RESULTS: The (mean +/- SD) SUV for 13 blastomycosis lesions was 7.7 +/- 2.0 versus a mean for 17 lymphomas of 4.8 +/- 1.8. These values were significantly different (P = 0.0537). There was overlap between the SUV of Blastomyces-associated lesions versus lymphomas, but a cut-off SUV of 7.0 was 100% specific for Blastomyces lesions. Numerous sites of disease were detected on the FDG-PET images that were not detected clinically. CONCLUSIONS: FDG-PET is useful for determining the extent of disease in dogs with blastomycosis. The SUV for Blastomyces-associated lesions are as high or higher than for malignant lymphoma. Due to the similarities in canine and human blastomycosis and lymphomas, similar results would be predicted in human patients. In regions where blastomycosis is endemic, Blastomyces granulomas should be considered a differential diagnosis for lesions with high intensity uptake of FDG.
Journal Article↗
Characterization of uptake of 2-deoxy-2-[18F]fluoro-D-glucose by fungal-associated inflammation: the differential uptake ratio for blastomyces-associated lesions is as high as for lymphoma and higher than for turpentine abscesses in experimentally induced lesions in rats.
PURPOSE: The objective of this investigation was to determine the biologic basis and the significance of uptake of 2-deoxy-2-[18F]fluoro-D-glucose (FDG) using experimentally created fungal lesions in rats. PROCEDURES: Uptake of FDG by experimentally induced Blastomyces granulomas was compared with uptake by turpentine abscesses (Group 1) and by lymphomas (Group 2) using the differential uptake ratio (DUR) measured one hour after administration of 2 mCi FDG intravenously. Frozen tissue sections of Blastomyces lesions and turpentine abscesses were placed in contact with radiographic film for macroautoradiography. RESULTS: In rats in Group 1, the median (range) DUR for the Blastomyces granulomas was 1.9 (1.1-2.6) and was significantly higher than the DUR for turpentine abscesses 0.9 (0.6-1.4) and muscle 0.2 (0.1-0.5; P < 0.001). In Group 2, the median (range) DUR for the Blastomyces granulomas, lymphomas, and muscle from the rats in Group 2 were 1.8 (1.2-3.4), 1.9 (1.0-4.0), and 0.2 (0.1-0.3), respectively. There was no significant difference between the DUR of Blastomyces granulomas and lymphomas. Macroautoradiographs of the Blastomyces granulomas revealed intense uptake of FDG in the region occupied by the yeast organisms and the granulomatous inflammation. CONCLUSIONS: Blastomyces granulomas typically have high uptake of FDG associated with the region composed of the granulomatous inflammatory reaction and Blastomyces yeast organisms.
Journal Article↗
Improved treatment planning for boron neutron capture therapy for glioblastoma multiforme using fluorine-18 labeled boronophenylalanine and positron emission tomography.
Boron neutron capture therapy (BNCT) is a cancer brachytherapy based upon the thermal neutron reaction: 10B(n,alpha)7Li. The efficacy of the treatment depends primarily upon two conditions being met: (a) the preferential concentration of a boronated compound in the neoplasm and (b) an adequate fluence of thermal neutrons delivered to the neoplasm. The boronated amino acid, para-boronophenylalanine (BPA), is the agent widely used in clinical trials to deliver 10B to the malignancy. Positron emission tomography (PET) can be used to generate in vivo boron distribution maps by labeling BPA with the positron emitting nuclide fluorine-18. The incorporation of the PET-derived boron distribution maps into current treatment planning protocols is shown to provide improved treatment plans. Using previously established protocols, six patients with glioblastoma had 18BPA PET scans. The PET distribution maps obtained were used in the conventional BNCT treatment codes. The isodose curves derived from the PET data are shown to differ both qualitatively and quantitatively from the conventional isodose curves that were derived from calculations based upon the assumption of uniform uptake of the pharmaceutical in tumor and normal brain regions. The clinical course of each of the patients who eventually received BNCT (five of the six patients) was compared using both sets of isodose calculations. The isodose contours based upon PET derived distribution data appear to be more consistent with the patients' clinical course.
Boron Compounds↗
The use of positron emission tomography to develop boron neutron capture therapy treatment plans for metastatic malignant melanoma.
Centers in Japan and the United States are extending boron neutron capture therapy (BNCT) to the treatment of malignant melanoma (MM). Positron emission tomography (PET) has been used to image glioblastoma multiforme with 18F-boronophenylalanine (18F-BPA) for the purpose of generating 10B distribution maps. These distribution maps can be used to improve the BNCT treatment planning. 18F-BPA was given to a patient with widely metastatic MM involving the thorax and brain. 18F-BPA PET scans of the chest and the head were obtained and compared to the computed tomograms (CT) and magnetic resonance (MR) images. The lung metastases seen on the chest CT images and intracranial metastases seen on CT and MR images were correlated with the PET images. The PET images clearly identified a brain lesion that was difficult to identify on MR and CT images. The 18F-BPA lung and peri-oral mucous gland activity was intense indicating a relatively high concentration of BPA. The intensity seen in the peri-oral mucous glands is consistent with the experiences in the BNCT clinical trials. These results have implications in the use of BNCT outside of the cranium. The PET images allow the generation of treatment plans that are consistent with the clinical findings. PET imaging with 18F-BPA can be used to identify potential tumors that may be amenable to BNCT and to improve treatment plans prior to BNCT.
Boron Compounds↗
2-deoxy-2-[F-18]fluoro-D-glucose-positron emission tomography sensitivity to serum glucose: a survey and diagnostic applications.
OBJECTIVE: The positron emission tomography (PET) clinical utility of the sensitivity (gamma) of uptake (Q) to a change in plasma glucose concentration (C) is investigated. METHODS: Gamma is obtained from data as [ln(Q (2)/Q (1))] / [ln(C(2)/C(1))], using previously published intrapatient studies varying C within a single patient and some interpatient ones. It can be theoretically related to the half-saturation constant in the Michaelis-Menten quantification of competitive uptake. One of its uses is making uptake corrections for desired vs. actual C using Q(2) = Q(1) (C(2)/C(1))(gamma). RESULTS: Intrapatient studies proved to be preferable to interpatient ones, and a 2-deoxy-2-[F-18]fluoro-D-glucose (FDG)-PET survey with analyses for gamma yielded the following result: usually the gamma values of tumors and brain tissues were near -1, whereas those of other noncerebral tissues were near 0. Regarding correcting uptakes for C, instead of a universally assumed and applied gamma = -1, corrections should be for a single tissue using its known gamma. An advantageous use of gamma is predicting how C affects image contrast, including where glucose loading is sometimes preferable to fasting. CONCLUSIONS: A potentially useful quantifier of uptake sensitivity to plasma glucose has been defined and values obtained. Correcting uptakes to some standard C requires special care. gamma can help PET clinicians select fasting or loading to achieve glucose levels for optimum contrast.
Blood Glucose↗
A weight index for the standardized uptake value in 2-deoxy-2-[F-18]fluoro-D-glucose-positron emission tomography.
INTRODUCTION: Known errors in the standardized uptake value (SUV) caused by variations in subject weights W encountered can be corrected by lean body mass or body surface area (bsa) algorithms replacing W in calculations. However this is infrequently done. The aims of the work here are: quantify sensitivity to W, encourage SUV correction with an approach minimally differing from tradition, and show what improvements in the SUV coefficient of variation (cv) for a population can be expected. METHODS: Selected for analyses were 2-deoxy-2-[F-18]fluoro-D-glucose (FDG) SUV data from positron emission tomography (PET) and PET/computed tomography (CT) scans at the University of Tennessee as well as from the literature. A weight sensitivity index was defined as -n=slope of ln(SUV/W) vs. lnW. The portion of the SUV variability due to this trend is removed by using the defined [formula: see text], or a virtually equal SUVm using [formula: see text], with Q and ID being tissue specific-activity and injected dose. [formula: see text] measures performance. Adapting to animal studies' tradition, [formula: see text] is preferred over the conventional [formula: see text]. RESULTS: For FDG in adults [formula: see text] from averaging over most tissues. In children, however, [formula: see text]. Tissues have the same index if their influx constants are independent of W. Suggested, therefore, is a very simplified [formula: see text], which is dimensionless and keeps the same population averages as traditional SUVs. It achieves [formula: see text]. Hence, for cv's of SUVs below approximately 1/3 improvements over tradition are possible, leading to F's<0.95. Accounting additionally for height, as in SUVbsa, gives very little improvement over the simplified approach here and gives essentially the same F's as SUVm. CONCLUSIONS: Introduced here is a weight index useful in reducing variability and further understanding the SUV. Addressing weight sensitivity is appropriate where the cv of the SUVs is below about 1/3. Proposed is the very simple approach of using an average of an adult patient's weight and approximately 70 kg for FDG SUV calculations. Unlike other approaches the dimensionless population average of SUVms is unchanged from tradition.
Adult↗