PET imaging

An understanding of how drugs are transferred between mother and fetus during the gestational period is an important medical issue of relevance to both therapeutic drugs and drugs of abuse. Though there are several in vitro and in vivo methods to examine this issue, all have limitations. Furthermore, ethical and safety considerations generally preclude such studies in pregnant humans. PET and appropriately labeled compounds have the ability to provide information on both maternal-fetal drug pharmacokinetics and pharmacodynamics. We present here a nonhuman primate animal model and the methodology for combining PET and MRI to identify fetal organs and to measure maternal and fetal isotope distribution using (18)F-FDG and a whole-body imaging protocol to demonstrate proof-of-principle.

To study the impact of fused (18)F-fluoro-deoxy-D-glucose (FDG)-hybrid positron emission tomography (PET) and computed tomography (CT) images on conformal radiation therapy (CRT) planning for patients with esophageal carcinoma. Thirty-four patients with esophageal carcinoma were referred for concomitant radiotherapy and chemotherapy with radical intent. Each patient underwent CT and FDG-hybrid PET for simulation treatment in the same radiation treatment position. PET-images were coregistered using five fiducial markers. Target delineation was initially performed on CT images and the corresponding PET data were subsequently used as an overlay to CT data to define the target volume. FDG-PET identified previously undetected distant metastatic disease in 2 patients, making them ineligible for curative CRT. The Gross Tumor Volume (GTV) was decreased by CT and FDG image fusion in 12 patients (35%) and was increased in 7 patients (20.5%). The GTV reduction was >or=25% in 4 patients due ...

Whole-body positron emission tomography (PET) has been shown to be a highly sensitive method for detecting malignancy not imaged by conventional modalities. We have adapted a hand-held gamma-ray-sensitive probe to detect the radiation emission from the [(18)F]fluorodeoxyglucose (FDG) used in PET imaging. This pilot study was devised to examine the feasibility of using a hand-held probe to intraoperatively differentiate normal from tumor-bearing tissue. A commercially available gamma probe was adapted to detect the radioactivity released from FDG and examined to determine the in vitro sensitivity for localization of a FDG point source. Eight consecutive patients underwent resection of metastatic colon cancer or melanoma; each received a preoperative injection of 7--10 mCi of FDG. The gamma probe was used to determine radioactive counts per second from tumor and normal tissue, and ratios of tumor to adjacent normal background were calculated. In vitro studies with a FDG point source demonstrated the probe could identify the source with a 50% reduction in maximum counts 1.7 +/- 0.1 cm from the source (full-width half-maximum measurement). Based on the results of their preoperative PET scans 17 tumors were identified from the 8 patients. Of the 17 tumors assessed the in vivo tumor-to-background ratios varied from 1.16:1 to 4.67:1 for the melanoma patients (13 tumors) and from 1.19:1 to 7.92:1 for colon cancer patients (4 tumors). Thirteen tumors were resected; four (2 patients) were unresectable. This study demonstrates the use of a hand-held gamma-ray-sensitive probe to intraoperatively differentiate the radioactivity released from FDG from tumor-bearing and adjacent normal tissue. While further studies are necessary for us to optimize the use of this probe, the intraoperative detection of FDG-avid malignancies may ultimately improve our ability to completely resect patients with metastatic disease.

Rationale Several lines of evidence suggest that altered serotonin (5-HT) function persists after recovery from anorexia nervosa (AN) and bulimia nervosa (BN). Objectives We compared 11 subjects who recovered (>1 year normal weight, regular menstrual cycles, no bingeing or purging) from restricting-type AN (REC RAN), 7 who recovered from bulimia-type AN (REC BAN), 9 who recovered from BN (REC BN), and 10 healthy control women (CW). Materials and methods Positron emission tomography (PET) imaging with [11C]McN5652 was used to assess the 5-HT transporter (5-HTT). For [11C]McN5652, distribution volume (DV) values were determined using a two-compartment, three-parameter tracer kinetic model, and specific binding was assessed using the binding potential (BP, BP = DVregion of interest/DVcerebellum − 1). Results After correction for multiple comparisons, the four groups showed significant (p < 0.05) differences for [11C]McN5652 BP values for the dorsal raphe and antero-ventral striatum (AVS). Post-hoc analysis revealed that REC RAN had significantly increased [11C]McN5652 BP compared to REC BAN in these regions. Conclusions Divergent 5-HTT activity in subtypes of eating disorder subjects may provide important insights as to why these groups have differences in affective regulation and impulse control.

Approximately 10% of the pheochromocytomas and 20% of the paragangliomas are malignant with poor survival. As the biological behaviour of these tumours cannot be predicted with certainty from pathology the diagnosis of malignancy is difficult. Genetic testing is gaining impact as mutations in the tumour suppressor gene Von Hippel-Lindau and the mitochondrial succinate dehydrogenase enzyme complex subunit B (SDHB) are associated with malignancy. Excess release of catecholamines is characteristic for pheochromocytomas. High levels of chromogranin A, that is co-stored and co-secreted with catecholamines, may indicate tumour mass and malignancy and can be used to monitor response and relapse. The secretory and non-secretory tumours can be visualised with functional (specific and non-specific) imaging as SPECT and PET using ¹²³I-MIBG, somatostatin analogues, ¹⁸F-DOPA, and ¹⁸F-FDG. These modalities are recommended in patients with extra-adrenal and suspected metastatic/malignant disease, in case of distorted post-operative anatomy, and when suspected recurrence. The sensitivities of ¹²³I-MIBG scintigraphy or ¹⁸F-DOPA PET are relatively low in SDHB mutated tumours, but high using ¹⁸F-FDG. Specific PET imaging with somatostatin analogues generally has high sensitivity in malignant disease. There are no curative therapeutic options for malignant, metastatic pheochromocytomas/paragangliomas, wherefore consolidation of quality of life is essential. Adjuvant radionuclide treatment with beta-emitting isotopes coupled to MIBG or somatostatin analogues have shown response in approximately 30%. Chemotherapy is restricted to patients not accessible for surgery and resistant to radionuclide therapy. Novel targeted therapies, which mainly through a cytostatic effect interfere with specific targeted molecules needed for carcinogenesis and tumour growth show encouraging results.

In oncology, positron emission computed tomography (PET/CT) has become an essential tool for initial staging, response evaluation and follow-up of cancer patients. Most of the frequent tumors (lung, breast, esophagus, and lymphomas) are highly avid for 18F-fluorodeoxyglucose (18FDG), but prostate cancer has not demonstrated significant uptake of FDG. The development of new tracers labeled with 18F such as choline analogs allowed already to obtain interesting results particularly in patients with biological relapse and inconclusive conventional imaging work-up. The impact of 18F-flurocholine PET/CT on patient management needs to be validated in large studies, but many centers use already this examination in order to guide further management, including radiotherapy planning.

Purpose: To explore the prognostic value of metabolic tumor volume measured on postradiation ¹F-fluorodeoxyglucose positron emission tomography (PET) imaging in patients with head-and-neck cancer. Methods and Materials: Forty-seven patients with head-and-neck cancer who received pretreatment and posttreatment PET/computed tomography (CT) imaging along with definitive chemoradiotherapy were included in this study. The PET/CT parameters evaluated include the maximum standardized uptake value,

Image degradation due to motion is a known problem in Positron Emission Tomography (PET). To reduce motion artifacts in PET, gating based techniques were found applicable. In pure respiratory gated PET, each gate still contains cardiac motion. Analogously, pure cardiac gated PET images still contain respiratory motion. Hence, we make use of dual (joint respiratory and cardiac) gating to further