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This study was designed to evaluate whether subjects with amyloid beta (Aβ) pathology, detected using florbetapir positron emission tomorgraphy (PET), demonstrated greater cognitive decline than subjects without Aβ pathology. Sixty-nine cognitively normal (CN) controls, 52 with recently diagnosed mild cognitive impairment (MCI) and 31 with probable Alzheimer's disease (AD) dementia were included in the study. PET images obtained in these subjects were visually rated as positive (Aβ+) or negative (Aβ-), blind to diagnosis. Fourteen percent (10/69) of CN, 37% (19/52) of MCI and 68% (21/31) of AD were Aβ+. The primary outcome was change in ADAS-Cog score in MCI subjects after 36 months; however, additional outcomes included change on measures of cognition, function and diagnostic status. Aβ+ MCI subjects demonstrated greater worsening compared with Aβ- subjects on the ADAS-Cog over 36 months (5.66 ± 1.47 vs -0.71 ± 1.09, P = 0.0014) as well as on the mini-mental state exam (MMSE), digit symbol substitution (DSS) test, and a verbal fluency test (P0.05). Similar to MCI subjects, Aβ+ CN subjects showed greater decline on the ADAS-Cog, digit-symbol-substitution test and verbal fluency (P0.05), whereas Aβ+ AD patients showed greater declines in verbal fluency and the MMSE (P0.05). Aβ+ subjects in all diagnostic groups also showed greater decline on the CDR-SB (P0.04), a global clinical assessment. Aβ+ subjects did not show significantly greater declines on the ADCS-ADL or Wechsler Memory Scale. Overall, these findings suggest that in CN, MCI and AD subjects, florbetapir PET Aβ+ subjects show greater cognitive and global deterioration over a 3-year follow-up than Aβ- subjects do.

This study seeks to assess the impact of dedicated brain positron emission tomography (PET) with 2-deoxy-2-[(18)F]fluoro-D-glucose on intended management of patients with primary and metastatic brain tumors.We analyzed demographic characteristics and evaluated change in intended management after PET, using previously described metrics, for patients in the National Oncologic PET Registry (NOPR) undergoing dedicated brain PET. For cases of primary brain tumors, comparisons to the overall NOPR cohort were made. PATIENT PROFILE: Between December 2006 and April 2009, 509 dedicated brain PET scans were done on 479 patients--367 (72.1%) for suspected or proven primary brain tumors and 142 (27.9%) for brain metastases. Compared with the overall NOPR cohort, subjects in the dedicated brain cohort were younger (41.3% less than 65 years vs. 10.5% overall, p0.0001) and more frequently had functional limitations from their cancers (78.6% vs. 62.3% overall; odds ratio (OR) 2.2, 95% CI 1.8-2.8).The pre-PET patient management plans in the primary brain tumor and metastasis subgroups were similar. A pre-PET plan of tissue biopsy was slightly more frequent than one of the treatments (31.3% vs. 28.6%) in the primary brain tumor subgroup and was more common than in the overall NOPR cohort (14.2%; OR 2.8, 95% CI 2.2-3.5). Changes from treatment to non-treatment also were more frequent than in the overall NOPR cohort (13.4% vs. 7.7%; OR 1.9, 95% CI 1.3-2.5).Among NOPR patients, dedicated brain PET was associated with similar net changes in intended management as in the overall NOPR cohort. However, brain PET patients were younger, more likely to be symptomatic, and less likely to have a change in management from non-treatment to treatment as a post-PET plan.

Positron emission tomography (PET) imaging at more than 1 h after 2-deoxy-2-[18F]fluoro-d-glucose (FDG) administration may result in less blood pool activity and possibly decreased normal FDG uptake in tissues such as liver. Lower normal background activity could be an important component of improved image contrast on delayed imaging. Increasing FDG uptake in normal organs, however, may mitigate the beneficial effects of blood pool clearance. The purpose of this study is to determine the normal tissue and blood pool FDG uptake at 1 and 3 h after injection. Ninety-nine patients with known or suspected malignancy referred for FDG-PET–computed tomography (CT) were retrospectively evaluated. PET imaging was performed at either 1 h (60 ± 15 min; n = 50) or at 3 h (180 ± 15 min; n = 49) after FDG administration. Normal tissue FDG uptake without involvement by malignancy or influenced by artifact (misregistration, “brown fat,” focal muscle uptake, focal atherosclerotic disease) was confirmed by inspection of both the PET and CT scans. Aortic blood pool, adipose tissue, bone marrow, cerebellum, liver, lungs, muscle, and spleen were quantitatively evaluated by CT-guided region of interest analysis in three contiguous slices. Mean standardized uptake values (SUVs) were analyzed using one-way analysis of variance. Mean SUVs on the 3- versus 1-h images were significantly lower for aortic blood pool 13% (p

The presence of contrast materials on computed tomography (CT) images can cause problems in the attenuation correction of positron emission tomography (PET) images. These are because of errors converting the CT attenuation of contrast to 511-keV attenuation and by the change in tissue enhancement over the duration of the PET emission scan. Newer CT-based attenuation correction (CTAC) algorithms have been developed to reduce these errors. To evaluate the effectiveness of the modified CTAC technique, we performed a retrospective analysis on 20 patients, comparing PET images using unenhanced and contrast-enhanced CT scans for attenuation correction. A phantom study was performed to simulate the effects of contrast on radiotracer concentration measurements. There was a maximum difference in calculated radiotracer concentrations of 5.9% within the retrospective data and 7% within the phantom data. Using a CTAC algorithm that de-emphasizes high-density areas, contrast-enhanced CT can be used for attenuation mapping without significant errors in quantitation.

The accumulation of 3′-deoxy-3′-[F-18]fluorothymidine (FLT) on positron emission tomography (PET) images in patients with glioblastoma multiforme was evaluated and correlated with gadopentetate dimeglumine (Gd-DTPA) enhancement in magnetic resonance images (MRIs). FLT studies in 10 patients with recurrent glioblastoma multiforme were retrospectively investigated. Dynamic emission data were acquired for 60 minutes immediately after injection of FLT. The standardized uptake value (SUV) for tumor and reference tissue (contralateral hemisphere and ipsilateral cerebellum) was calculated. The volumes of the metabolically active part of the tumor (V PET) and that of the Gd-DTPA enhancing part of the tumor (V MR) were calculated. FLT uptake in tumors peaked before 5 minutes and sometimes as early as 0.5 minutes, and reached a constant level at approximately 10 minutes after injection. The reference tissue time–activity curves had an early peak and reached a constant low background level. All tumors had increased FLT uptake and showed Gd-DTPA enhancement. The SUV in tumor was significantly higher than that in the reference tissue (P

Previous studies have demonstrated alterations in brain response to rectal distension in patients with irritable bowel syndrome (IBS) compared to controls. Our aim was to compare regional brain activity in response to rectal balloon distension in patients with IBS and healthy controls. We studied six patients with IBS and six healthy controls. Positron emission tomography scans were obtained during rectal balloon distensions. Statistical parametric mapping and region of interest analysis were performed to identify and compare differences in regional cerebral blood flow (CBF) for each distension pressure within and between the groups of interest. In post-hoc analyses, patients with a history of sexual or physical abuse were compared to patients without abuse. In response to rectal distension, controls exhibit a greater increase in anterior cingulate cortex (ACC) activity compared to the IBS group (Z = 3.2, P = 0.001). Thalamic activity was higher in the IBS patients relative to the control group (Z = 3.3, P < 0.001). Increased ACC activity was observed in IBS patients with no history of abuse (Z = 5.2, P < 0.001) similar to controls, whereas no such increased activity was noticed in the abused group. In conclusion, this study replicates previous findings showing alterations in brain response to rectal distension in patients with IBS. The observations on the effect of abuse suggest a possible modulating role of abuse history on this brain response.

This study examined the effect that 18-fluorodeoxyglucose positron emission tomography ((18)FDG-PET) imaging had on the clinical management of patients with suspected periampullary malignancy.Fifty-four patients with suspected pancreatic neoplasms underwent both whole-body (18)FDG-PET and abdominal computed tomography (CT). Malignant or benign disease was confirmed pathologically in 47 patients.Of the 41 patients with malignancy, (18)FDG-PET failed to identify the primary tumor in 5 patients. (18)FDG-PET demonstrated increased uptake suggesting primary malignancy in 37 patients. Malignant pathology was confirmed in 36 cases. (18)FDG-PET identified malignant locoregional lymph node metastases in six of ten patients. All nodes identified before surgery by (18)FDG-PET were also seen on preoperative CT. Six patients who were thought to have resectable disease by CT were found to have distant metastasis at laparotomy. (18)FDG-PET did not detect metastasis in any of these cases. Before surgery, (18)FDG-PET identified distant metastases that were not detected by CT in one patient.Despite high sensitivity and specificity in diagnosing periampullary malignancy, (18)FDG-PET did not change clinical management in the vast majority of patients previously evaluated by CT. In addition, (18)FDG-PET missed10% of periampullary malignancies and did not provide the anatomical detail necessary to define unresectabilty.

The purpose of this study was to compare the incremental value of clinical information, electrocardiographic data, myocardial perfusion imaging, and radionuclide angiography for predicting severe coronary artery disease at a single testing interval. Clinical information, treadmill exercise studies, radionuclide angiography, and myocardial perfusion imaging are important predictors of severe coronary artery disease. However, the relative and absolute diagnostic importance of each of these methods has not been addressed at a single testing interval. A same-day rest/treadmill exercise perfusion and function study was performed in 167 patients within 90 days of coronary angiography. A multivariable regression model was used to assess the independent informational content of these predictors. Clinical and electrocardiographic data were related strongly to the presence of severe coronary artery disease (χ2=12.2 and p

Although several modeling strategies have been developed and validated for quantification of myocardial blood flow (MBF) from 13N-labeled ammonia positron emission tomographic data, a comparison of noise characteristics of the various techniques in serial studies is lacking. Dynamic 13N-labeled ammonia positron emission tomographic imaging was performed at baseline and after pharmacologic stress in (1) single studies of four dogs with concomitant measurement of microsphere blood flow and (2) initial and follow-up studies of eight normal volunteers. Data were obtained from short-axis images for the blood pool and myocardial regions corresponding to the three arterial vascular territories. Indexes of MBF were obtained by four distinct techniques: (1) University of California, Los Angeles, twocompartment model, (2) Michigan two-compartment model, and (3) a one-compartment model with variable blood volume term. Coronary flow reserve (CFR) was measured as the ratio of stress/rest MBF. The estimated standard deviation of the measurement error for the relative change between studies of rest and stress MBF and CFR was determined for each technique. Estimates of MBF from all techniques showed good correlation with microsphere blood flow (r=0.95 to 0.96) in canine myocardium. In human studies, similar mean estimates of MBF were found with all techniques. Techniques 1 and 3 showed the smallest interstudy variability in MBF and CFR. The estimated standard deviations for these techniques were approximately 20%, 30%, and 27% for rest MBF, stress MBF, and CFR, respectively. Noninvasive quantification of MBF and CFR from dynamic 13N-labeled ammonia positron emission tomography is most reproducible with technique 1 or 3. The ability to account for differences in myocardial partial volume gives preference to technique 3. However, substantial interstudy variability in regional MBF remains, suggesting the importance of procedural factors or real temporal fluctuations in MBF.

The kinetics of para-[18F]fluorobenzylguanidine ([18F]PFBG) were investigated in a canine coronary artery occlusion model. Five dogs were imaged by positron emission tomography (PET) before and after complete surgical ligation of the left anterior descending coronary artery. PET studies included a 10-minute dynamic [13N]NH3 perfusion scan, followed 1 hour later by 3-hour dynamic [18F]PFBG scanning. [18F]PFBG and [13N]NH3 images demonstrated homogeneous myocardial uptake/perfusion before infarction. One hundred eighty minutes after [18F]PFBG administration, myocardial accumulation was decreased by 60% (day, 2, 0.0065% ±0.0015% injected dose/ml) and 58% (day 16, 0.0069%±0.003% injected dose/ml) compared with a similar myocardial region of interest from the preinfarction (0.016%±0.005% injected dose/ml) study. Myocardial accumulation of [13N]NH3 at 9 minutes showed a 52% (day 2) and 7% (day 16) decrease compared with the preinfarction study. The accumulation of [18F]PFBG in the infarction was decreased significantly at 120 and 180 minutes on all postinfarction studies (p=0.01). In three dogs a significant decrease in the myocardial norepinephrine concentration was documented in the area of infarction (237±94 ng/gm) versus the noninfarcted (1018±48 ng/gm) myocardium (p=0.001). A decreased accumulation of [18F]PFBG was observed in the area of myocardial infarct in this canine model. The magnitude of the decrease in [18F]PFBG was larger than that seen with [13N]NH3 on day 16 after infarction suggesting reperfusion and persistent sympathetic neuronal dysfunction.