18F-FDG-PET-MRI for the assessment of acute intestinal graft-versus-host-disease (GvHD).

BACKGROUND: Graft versus host disease (GvHD) is a frequent complication of allogeneic stem cell transplantation (alloSCT), significantly increasing mortality. Previous imaging studies focused on the assessment of intestinal GvHD with contrast-enhanced MRI/CT or 18F-FDG-PET imaging alone. The objective of this retrospective study was to elucidate the diagnostic value of a combined 18F-FDG-PET-MRI protocol in patients with acute intestinal GvHD. METHODS: Between 2/2015 and 8/2019, 21 patients with acute intestinal GvHD underwent 18F-FDG-PET-MRI. PET, MRI and PET-MRI datasets were independently reviewed. Readers assessed the number of affected segments of the lower gastrointestinal tract and the reliability of the diagnosis on a 5-point Likert scale and quantitative PET (SUVmax, SUVpeak, metabolic volume (MV)) and MRI parameter (wall thickness), were correlated to clinical staging of acute intestinal GvHD. RESULTS: The detection rate for acute intestinal GvHD was 56.8% for PET, 61.4% for MRI and 100% for PET-MRI. PET-MRI (median Likert-scale value: 5; range: 4-5) offers a significantly higher reliability of the diagnosis compared to PET (median: 4; range: 2-5; p = 0.01) and MRI alone (median: 4; range: 3-5; p = 0.03). The number of affected segments in PET-MRI (rs = 0.677; p <  0.001) and the MV (rs = 0.703; p <  0.001) correlated significantly with the clinical stage. SUVmax (rs = 0.345; p = 0.14), SUVpeak (rs = 0.276; p = 0.24) and wall thickening (rs = 0.174; p = 0.17) did not show a significant correlation to clinical stage. CONCLUSION: 18F-FDG-PET-MRI allows for highly reliable assessment of acute intestinal GvHD and adds information indicating clinical severity.

Longitudinal assessment of amyloid-beta deposition in initially amyloid-negative non-demented individuals with [11C]-PIB PET imaging.

ABSTRACT: This study aimed to assess the longitudinal changes in amyloid beta (Aß) deposition in cortical regions with [11C]-PIB PET in initially amyloid-negative non-demented subjects and evaluate whether amyloid-negative subjects convert to amyloid-positive.Sixteen cognitively normal (CN) and 7 mild cognitive impairment (MCI) subjects (aged 60-75 years), who were amyloid-negative at baseline, underwent 60-minute dynamic [11C]-PIB PET and cognitive assessment over 5.0 to 9.4 years of a long follow-up, and the apolipoprotein-E (APOE) genotype was assessed. Regions of interest were defined in the bilateral cortex on coregistered MRI. Quantitative analysis of [11C]-PIB was performed using the distribution value ratio (DVR). Longitudinal changes in global and regional PIB DVRs were evaluated in the same regions, and the annual rate of change in the PIB DVR was calculated.Seven (30.4%) of 23 initially amyloid-negative non-demented subjects converted to globally amyloid-positive (global PIB DVR ≥1.40) over a follow-up of 6.5 ±â€Š1.4 years (converter). The global PIB DVR in converters increased from 1.22 ±â€Š0.07 at baseline to 1.63 ±â€Š0.15 (n = 7, P < .01) at last follow-up, and an annual increase of global PIB DVR was 0.057 ±â€Š0.019/year (n = 7, P < .01). In contrast, the global PIB DVR in the remaining 16 subjects was 1.15 ±â€Š0.07 at baseline and did not change over a follow-up period (stable). The APOE ε4 allele was present in 4 (57.1%) of the 7 converters, differing from 2 (12.5%) of 16 stable subjects (Fisher's exact test, P < .05). Three amyloid-negative MCI subjects had an annual increase in global PIB DVR above 0.061/year and became positive at 2.8 ±â€Š0.5 years of follow-up, which was faster than 5.0 ±â€Š2.0 years in 4 CN subjects. The regional PIB DVR that increased early above the regional positivity threshold was most frequently found in the right lateral temporal cortex (71.4%), followed by the left frontal cortex (41.8%).Our results suggest that the initially amyloid-negative CN and MCI subjects, especially with APOE ε4, can become globally amyloid-positive over a longer time, based on early regional Aß deposition in the lateral temporal cortex and/or frontal cortex.

(An overview of) Synergistic reconstruction for multimodality/multichannel imaging methods.

Imaging is omnipresent in modern society with imaging devices based on a zoo of physical principles, probing a specimen across different wavelengths, energies and time. Recent years have seen a change in the imaging landscape with more and more imaging devices combining that which previously was used separately. Motivated by these hardware developments, an ever increasing set of mathematical ideas is appearing regarding how data from different imaging modalities or channels can be synergistically combined in the image reconstruction process, exploiting structural and/or functional correlations between the multiple images. Here we review these developments, give pointers to important challenges and provide an outlook as to how the field may develop in the forthcoming years. This article is part of the theme issue 'Synergistic tomographic image reconstruction: part 1'.

Early stopping in clinical PET studies: How to reduce expense and exposure.

Clinical positron emission tomography (PET) research is costly and entails exposing participants to radioactivity. Researchers should therefore aim to include just the number of subjects needed to fulfill the purpose of the study. In this tutorial we show how to apply sequential Bayes Factor testing in order to stop the recruitment of subjects in a clinical PET study as soon as enough data have been collected to make a conclusion. By using simulations, we demonstrate that it is possible to stop a study early, while keeping the number of erroneous conclusions low. We then apply sequential Bayes Factor testing to a real PET data set and show that it is possible to obtain support in favor of an effect while simultaneously reducing the sample size with 30%. Using this procedure allows researchers to reduce expense and radioactivity exposure for a range of effect sizes relevant for PET research.

Postoperative Surveillance in Older Adults With T1N0M0 Low-risk Papillary Thyroid Cancer.

BACKGROUND: The frequency and cost of postoperative surveillance for older adults (>65 y) with T1N0M0 low-risk papillary thyroid cancer (PTC) have not been well studied. METHODS: Using the SEER-Medicare (2006-2013) database, frequency and cost of surveillance concordant with American Thyroid Association (ATA) guidelines (defined as an office visit, ≥1 thyroglobulin measurement, and ultrasound 6- to 24-month postoperatively) were analyzed for the overall cohort of single-surgery T1N0M0 low-risk PTC, stratified by lobectomy versus total thyroidectomy. RESULTS: Majority of 2097 patients in the study were white (86.7%) and female (77.5%). Median age and tumor size were 72 y (interquartile range 68-76) and 0.6 cm (interquartile range 0.3-1.1 cm), respectively; 72.9% of patients underwent total thyroidectomy. Approximately 77.5% of patients had a postoperative surveillance visit; however, only 15.9% of patients received ATA-concordant surveillance. Patients who underwent total thyroidectomy as compared with lobectomy were more likely to undergo surveillance testing, thyroglobulin (61.7% versus 24.8%) and ultrasound (37.5% versus 29.2%) (all P < 0.01), and receive ATA-concordant surveillance (18.5% versus 9.0%, P < 0.001). Total surveillance cost during the study period was $621,099. Diagnostic radioactive iodine, ablation, and advanced imaging (such as positron emission tomography scans) accounted for 55.5% of costs ($344,692), whereas ATA-concordant care accounted for 44.5% of costs. After multivariate adjustment, patients who underwent total thyroidectomy as compared with lobectomy were twice as likely to receive ATA-concordant surveillance (adjusted odds ratio 2.0, 95% confidence interval: 1.5-2.8, P < 0.001). CONCLUSIONS: Majority of older adults with T1N0M0 low-risk PTC do not receive ATA-concordant surveillance; discordant care was costly. Total thyroidectomy was the strongest predictor of receiving ATA-concordant care.

Assessing the downstream value of first-line cardiac positron emission tomography (PET) imaging using real world Medicare fee-for-service claims data.

BACKGROUND: Higher imaging quality makes cardiac positron emission tomography (PET) desirable for evaluation of suspected coronary artery disease (CAD). High cost of PET imaging may be offset by reduced utilization and/or improved outcomes. METHODS: This retrospective observational study utilized Medicare fee-for-service dataset. Study participants had no CAD diagnosis within 1 year prior to initial imaging. The PET group (PET imaging) and propensity score matched comparison group (single photon emission computed tomography or stress echocardiography) underwent index imaging between January 2014 and December 2016. Outcomes were analyzed using generalized linear models. RESULTS: Among 144,503 study subjects, 4619 (3.2%) had PET and 139,884 (96.8%) had conventional imaging. After matching, each group had 4619 patients (mean age 74 years, 59% female). The PET group had lower radiation exposure (3.8 milliSievert less per year, 95% CI - 3.96 to - 3.64, P < .0001) and unstable coronary syndrome (incidence rate ratio (IRR) 0.77, 95% CI 0.64-0.94, P = .008). The PET group experienced more hospital admissions (IRR 1.10, 95% CI 1.06-1.15, P < .0001), more use of percutaneous coronary intervention (IRR 1.24, 95% CI 1.02-1.50, P = 0.03), while similar mortality rate (hazard ratio 0.95, 95% CI 0.78-1.14, P = 0.55). The PET group had higher medical spending ($2358.2 vs $1774.3, difference = $583.9 per patient per month, P < .0001). CONCLUSIONS: First-line PET imaging was not associated with reduced levels of utilization and spending. Clinical outcomes were mostly similar.

Performance evaluation of developed dedicated breast PET scanner and improvement of the spatial resolution by wobbling: a Monte Carlo study.

PURPOSE: Molecular imaging, particularly PET scanning, has become an important cancer diagnostic tool. Whole-body PET is not effective for local staging of cancer because of their declining efficiency in detecting small lesions. The preliminary results of the performance evaluation of designed dedicated breast PET scanner presented. METHODS AND MATERIALS: A new scanner is based on LYSO crystals coupled with SiPM, and it consists of 14 compact modules with a transaxial FOV of 180 mm in diameter. In this study, initial GATE simulation studies were performed to predict the spatial resolution, absolute sensitivity, noise equivalent count rate (NECR) and scatter fraction (SF) of the new design. Spatial wobbling acquisitions were also implemented. Finally, the obtained projections were reconstructed using analytical and iterative algorithms. RESULTS: The simulation results indicate that absolute sensitivity is 1.42% which is appropriate than other commercial breast PET systems. The calculated SF and NECR in our design are 20.6% and 21.8 kcps. The initial simulation results demonstrate the potential of this design for breast cancer detection. A small wobble motion to improve spatial resolution and contrast. CONCLUSION: The performance of the dedicated breast PET scanner is considered to be reasonable enough to support its use in breast cancer imaging.

Simultaneous confidence corridors for mean functions in functional data analysis of imaging data.

Motivated by recent work involving the analysis of biomedical imaging data, we present a novel procedure for constructing simultaneous confidence corridors for the mean of imaging data. We propose to use flexible bivariate splines over triangulations to handle an irregular domain of the images that is common in brain imaging studies and in other biomedical imaging applications. The proposed spline estimators of the mean functions are shown to be consistent and asymptotically normal under some regularity conditions. We also provide a computationally efficient estimator of the covariance function and derive its uniform consistency. The procedure is also extended to the two-sample case in which we focus on comparing the mean functions from two populations of imaging data. Through Monte Carlo simulation studies, we examine the finite sample performance of the proposed method. Finally, the proposed method is applied to analyze brain positron emission tomography data in two different studies. One data set used in preparation of this article was obtained from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database.

The quantitative assessment of interstitial lung disease with positron emission tomography scanning in systemic sclerosis patients.

OBJECTIVES: The reversibility of interstitial lung disease (ILD) in SSc is difficult to assess by current diagnostic modalities and there is clinical need for imaging techniques that allow for treatment stratification and monitoring. 18F-Fluorodeoxyglucose (FDG) PET/CT scanning may be of interest for this purpose by detection of metabolic activity in lung tissue. This study aimed to investigate the potential role of 18F-FDG PET/CT scanning for the quantitative assessment of SSc-related active ILD. METHODS: 18F-FDG PET/CT scans and high resolution CT scans of eight SSc patients, including five with ILD, were analysed. For comparison, reference groups were included: eight SLE patients and four primary Sjögren's syndrome (pSS) patients, all without ILD. A total of 22 regions of interest were drawn in each patient at apical, medial and dorsobasal lung levels. 18F-FDG uptake was measured as mean standardized uptake value (SUVmean) in each region of interest. Subsequently, basal/apical (B/A) and medial/apical (M/A) ratios were calculated at patient level (B/A-p and M/A-p) and at tissue level (B/A-t and M/A-t). RESULTS: SUVmean values in dorsobasal ROIs and B/A-p ratios were increased in SSc with ILD compared with SSc without ILD (P = 0.04 and P = 0.07, respectively), SLE (P = 0.003 and P = 0.002, respectively) and pSS (P = 0.03 and P = 0.02, respectively). Increased uptake in the dorsobasal lungs and increased B/A-t ratios corresponded to both ground glass and reticulation on high resolution CT. CONCLUSION: Semi-quantitative assessment of 18F-FDG PET/CT is able to distinguish ILD from non-affected lung tissue in SSc, suggesting that it may be used as a new biomarker for SSc-ILD disease activity.

The Impact of the Choosing Wisely Campaign in Urology.

OBJECTIVE: To determine if 3 of the Canadian Urological Association's Choosing Wisely recommendations (released in 2013-2014) related to urologic care altered physician and patient behavior. METHODS: Administrative data from Ontario, Canada between 2008 and 2017 was used. We identified 3 cohorts: First, we determined how many men >66 years of age had a serum testosterone level before starting testosterone therapy. Second, we determined how many boys undergoing an orchiopexy underwent abdominal imaging before their surgery. Third, we determined how many men with low risk prostate cancer underwent a Bone Scan after diagnosis. Piece-wise linear regression was used to evaluate for a significant change after Choosing Wisely. RESULTS: We identified 13,113 men who had their initial prescription for testosterone filled. Serum testosterone measurement increased over time, from approximately 43% to 68%. There were 9319 boys who underwent an orchiopexy. The use of pre-orchiopexy ultrasound was generally stable (approximately 55%). We identified 27,174 men with low risk prostate cancer. The use of bone scans after diagnosis decreased over time from approximately 24% to 20%. In all 3 of these groups, there was no significant change after Choosing Wisely (P = .74, P = .70, P = .72 respectively). CONCLUSION: In Ontario, there was no evidence of a significant change in 3 practice patterns that were featured in Choosing Wisely Urology recommendations. Further thought may be needed on how to translate these and future recommendations into behavior change.

Variation in the use of advanced imaging at the time of breast cancer diagnosis in a statewide registry.

BACKGROUND: Although national guidelines do not recommend extent of disease imaging for patients with newly diagnosed early stage breast cancer given that the harm outweighs the benefits, high rates of testing have been documented. The 2012 Choosing Wisely guidelines specifically addressed this issue. We examined the change over time in imaging use across a statewide collaborative, as well as the reasons for performing imaging and the impact on cost of care. METHODS: Clinicopathologic data and use of advanced imaging tests (positron emission tomography, computed tomography, and bone scan) were abstracted from the medical records of patients treated at 25 participating sites in the Michigan Breast Oncology Quality Initiative (MiBOQI). For patients diagnosed in 2014 and 2015, reasons for testing were abstracted from the medical record. RESULTS: Of the 34,078 patients diagnosed with stage 0-II breast cancer between 2008 and 2015 in MiBOQI, 6853 (20.1%) underwent testing with at least 1 imaging modality in the 90 days after diagnosis. There was considerable variability in rates of testing across the 25 sites for all stages of disease. Between 2008 and 2015, testing decreased over time for patients with stage 0-IIA disease (all P < .001) and remained stable for stage IIB disease (P = .10). This decrease in testing over time resulted in a cost savings, especially for patients with stage I disease. CONCLUSION: Use of advanced imaging at the time of diagnosis decreased over time in a large statewide collaborative. Additional interventions are warranted to further reduce rates of unnecessary imaging to improve quality of care for patients with breast cancer. Cancer 2017;123:2975-83. © 2017 American Cancer Society.

Introduction of positron emission tomography into the Western Norwegian Health Region: Regional balance in resource utilization from 2009 to 2014.

BACKGROUND: The aim was to compare resource utilization across the four health trusts within the Western Norway Regional Health Authority since the establishment of positron emission tomography (PET) at Haukeland University Hospital in Bergen in 2009. METHODS: Metadata from all PET examinations from 2009 to 2014 were automatically imported from the PET centre's central production database into a custom-developed database system, MDCake. A PET examination was defined as a procedure based on a single injection of radioactive tracer. The patients' place of residence and tentative diagnosis were coded based on the available clinical information. RESULTS: The total number of PET examinations increased from 293 in 2009 to 1616 in 2014. The number of PET examinations per year increased across all diagnostic groups, but plateaued for lung cancer, gastrointestinal cancer and malignant melanoma since 2013. The number of examinations per capita was evenly distributed between the three northern health trusts with an average of 1260 PET studies per million inhabitants in 2014. However, patients residing in the most southerly health trust received between 44% (2010) and 27% (2014; P<0·001, repeated measures ANOVA) fewer examinations per capita per year. CONCLUSION: Centralized PET in the Western Norwegian health region meets the current clinical demand for patients residing in the three northern health trusts while patients from the most southern health trust receive approximately 30% fewer PET examinations. Access to specialized health care should be monitored routinely in order to identify inequalities in referral patterns and resource utilization.

Validation of Bayesian analysis of compartmental kinetic models in medical imaging.

INTRODUCTION: Kinetic compartmental analysis is frequently used to compute physiologically relevant quantitative values from time series of images. In this paper, a new approach based on Bayesian analysis to obtain information about these parameters is presented and validated. MATERIALS AND METHODS: The closed-form of the posterior distribution of kinetic parameters is derived with a hierarchical prior to model the standard deviation of normally distributed noise. Markov chain Monte Carlo methods are used for numerical estimation of the posterior distribution. Computer simulations of the kinetics of F18-fluorodeoxyglucose (FDG) are used to demonstrate drawing statistical inferences about kinetic parameters and to validate the theory and implementation. Additionally, point estimates of kinetic parameters and covariance of those estimates are determined using the classical non-linear least squares approach. RESULTS AND DISCUSSION: Posteriors obtained using methods proposed in this work are accurate as no significant deviation from the expected shape of the posterior was found (one-sided P>0.08). It is demonstrated that the results obtained by the standard non-linear least-square methods fail to provide accurate estimation of uncertainty for the same data set (P<0.0001). CONCLUSIONS: The results of this work validate new methods for a computer simulations of FDG kinetics. Results show that in situations where the classical approach fails in accurate estimation of uncertainty, Bayesian estimation provides an accurate information about the uncertainties in the parameters. Although a particular example of FDG kinetics was used in the paper, the methods can be extended for different pharmaceuticals and imaging modalities.

Pattern of Imaging after Lung Cancer Resection. 1992-2005.

RATIONALE: Imaging intensity after lung cancer resection performed with curative intent is unknown. OBJECTIVES: To describe the pattern and trends in the use of computed tomography (CT) and positron emission tomography (PET) scans in patients after resection of early-stage lung cancer. METHODS: Retrospective analysis of the linked Surveillance, Epidemiology and End Results (SEER)-Medicare database. Subjects included 8,621 Medicare beneficiaries (age, ≥66 yr) who underwent lung cancer resection with curative intent between 1992 and 2005. A surveillance CT or PET examination was defined as CT or PET imaging performed in an outpatient setting on patients who did not undergo chest radiography in the preceding 30 days. MEASUREMENTS AND MAIN RESULTS: Overall, imaging use was higher within the first 2 years versus Years 3-5 after surgical resection. Use of surveillance CT scans increased sharply from 13.7 to 57.3% of those diagnosed in 1996-1997 and 2004-2005, respectively. PET scan use increased threefold, from 6.2% in 2000-2001 to 19.6% in 2004-2005. In multivariable analyses, we observed a 32% increase in the odds of undergoing surveillance CT or PET imaging for every year of diagnosis between 1998 and 2005. There was no substantial decline in the odds of having a surveillance CT or PET scan during each successive follow-up period, suggesting no change in the intensity of surveillance over the first 5 years after surgical resection. The proportion of surveillance CT imaging performed at freestanding imaging centers increased from 18.0% in 1998-1999 to 30.6% in 2004-2005. CONCLUSIONS: The use of CT and PET imaging for surveillance after curative-intent surgical resection of early-stage lung cancer increased sharply in the United States between 1997-1998 and 2005. In the absence of evidence demonstrating favorable outcomes, this practice was likely driven by prevailing expert opinion embedded in clinical practice guidelines made available during that time. Research is clearly needed to determine the role and optimal approach to surveillance thoracic imaging after surgical resection of lung cancer.

Comparison between 18F-FDG PET/MRI and MDCT for the assessment of preoperative staging and resectability of gastric cancer.

PURPOSE: To investigate if 18F-FDG PET/MRI can improve the diagnostic performance of TNM staging and help make an accurate decision for resectability in patients with gastric cancer compared to MDCT. MATERIALS AND METHODS: Forty-two patients with histologically confirmed gastric cancers underwent preoperative MDCT and 18F-FDG PET/MRI. M-staging and resectability was assessed in all patients, and T- and N-staging was evaluated in 30 of 42 patients who underwent curative gastrectomy. Two abdominal radiologists independently assessed their MDCT images and 18F-FDG PET/MRI and determined preoperative TNM staging and resectability of gastric cancers. Diagnostic performance with MDCT and 18F-FDG PET/MRI were compared using McNemar's test and receiver operating characteristic analysis. RESULTS: Diagnostic accuracies for T and N staging were not significantly different between MDCT and 18F-FDG PET/MRI in both readers. However, 18F-FDG PET/MRI showed significantly improved diagnostic accuracy for M staging in one reader (P=0.008) and marginal improvement in the other reader (P=0.063) compared to MDCT. Regarding the resectability of gastric cancers, diagnostic accuracy (92.9% for both readers) of 18F-FDG PET/MRI was significantly higher than that (76.2% for reader 1 and 64.3% for reader 2) of MDCT in both readers (P<0.05). CONCLUSION: 18F-FDG PET/MRI may improve diagnostic accuracy for preoperative M staging as well as resectability of gastric cancers compared to MDCT.

Contribution of (18)F-FDG PET in the diagnostic assessment of fever of unknown origin (FUO): a stratification-based meta-analysis.

PURPOSE: The aim of this study was to quantify the contribution of FDG PET to the diagnostic assessment of fever of unknown origin (FUO), taking into account the diagnostic limitations resulting from the composite nature of this entity. METHODS: The PubMed/MEDLINE database was searched from 2000 to September 2015. Original articles fulfilling the following criteria were included: (1) FUO as the initial diagnosis, (2) no immunosuppressed or nosocomial condition, (3) final diagnosis not based on PET, (4) a follow-up period specified, (5) adult population, and (6) availability of adapted data for calculation of odds ratios (ORs). ORs were computed for each study and then pooled using a random effects model. Stratification-based sensitivity analyses were finally performed using the following prespecified criteria: (a) study design, (b) PET device, (c) geographic area, and (d) follow-up period. RESULTS: A meta-analysis of the 14 included studies showed that normal PET findings led to an increase in the absolute final diagnostic rate of 36 % abnormal PET findings to an increase of 83 %, corresponding to a pooled OR of 8.94 (95 % CI 4.18 - 19.12, Z = 5.65; p < 0.00001). The design of the studies influenced the results (OR 2.92, 95 % CI 1.00 - 8.53 for prospective studies; OR 18,57, 95 % CI 7.57 - 45.59 for retrospective studies; p = 0.01), whereas devices (dedicated or hybrid), geographic area and follow-up period did not. CONCLUSION: Abnormal PET findings are associated with a substantially increased final diagnostic rate in FUO. Consequently, FDG PET could be considered for inclusion in the first-line diagnostic work-up of FUO. Further randomized prospective studies with standardized FDG PET procedures are warranted to confirm this first-line position.

Predictive prognostic value of local and distant recurrence of F-fluorodeoxyglucose positron emission tomography for pancreatic neuroendocrine tumors with reference to World Health Organization classifications (2004, 2010). Case series study.

BACKGROUND: F-flurodeoxyglucose positron emission tomography (FDG-PET) have been claimed to be an important prognostic tool in different malignancies. However, its predictive prognostic value on pancreatic neuroendocrine tumors (PNETs) is still under investigation. AIM: We study the prognostic impact of FDG-PET scan in neuroendocrine pancreatic tumors. METHODOLOGY: Between 2007 and 2012, 26 patients with no metastastatic histologically confirmed PNETs (mean age: 57 years) were examined with FDG-PET. We studied its captation in relation with the well established hystopathological prognostic markers assessed in the tumoral resected specimen according to the WHO 2004 and ENETS/WHO 2010 classification. RESULTS: FDG-PET captation was positive in 17 cases (65.4%). The median follow-up period was 34.4 months and recurrences occurred in 4 cases (15.4%). We found a significant correlation between this captation and Ki 67 index (p = 0.032), mitotic index (p = 0.002), tumor grade (p = 0.017) and tumor size (p = 0.01). CONCLUSIONS: FDG-PET provides a good prognostic value for PNETs. Present results must be further validated with larger sample studies.

Use of Positron Emission Tomography to Detect Recurrence and Associations With Survival in Patients With Lung and Esophageal Cancers.

BACKGROUND: Positron emission tomography (PET) scans are often used in cancer patients for staging, restaging, and monitoring for treatment response. These scans are also often used to detect recurrence in asymptomatic patients, despite a lack of evidence demonstrating improved survival. We sought to evaluate utilization of PET for this purpose and relationships with survival for patients with lung and esophageal cancers. METHODS: Using national Surveillance, Epidemiology, and End Results (SEER) and Medicare-linked data, we identified incident patient cases from 2005 to 2009, with follow-up through 2011. We identified cohorts with primary lung (n = 97 152) and esophageal (n = 4446) cancers. Patient and tumor characteristics were used to calculate risk-adjusted two-year overall survival. Using Medicare claims, we examined PET utilization in person-years (to account for variable time in cohorts), excluding scans for staging and for follow-up of CT findings. We then stratified hospitals by quintiles of PET utilization for adjusted two-year survival analysis. All statistical tests were two-sided. RESULTS: There was statistically significant variation in utilization of PET. Lowest vs highest utilizing hospitals performed .05 (SD = 0.04) vs 0.70 (SD = 0.44) scans per person-year for lung cancer and 0.12 (SD = 0.06) vs 0.97 (SD = 0.29) scans per person-year for esophageal cancer. Despite this, for those undergoing PET, lowest vs highest utilizing hospitals had an adjusted two-year survival of 29.0% (SD = 12.1%) vs 28.8% (SD = 7.2%) for lung cancer (P = .66) and 28.4% (SD = 7.2%) vs 30.3% (SD = 5.9%) for esophageal cancer (P = .55). CONCLUSIONS: Despite statistically significant variation in use of PET to detect tumor recurrence, there was no association with improved two-year survival. These findings suggest possible overuse of PET for recurrence detection, which current Medicare policy would not appear to substantially affect.

On the assessment of spatial resolution of PET systems with iterative image reconstruction.

Spatial resolution is an important metric for performance characterization in PET systems. Measuring spatial resolution is straightforward with a linear reconstruction algorithm, such as filtered backprojection, and can be performed by reconstructing a point source scan and calculating the full-width-at-half-maximum (FWHM) along the principal directions. With the widespread adoption of iterative reconstruction methods, it is desirable to quantify the spatial resolution using an iterative reconstruction algorithm. However, the task can be difficult because the reconstruction algorithms are nonlinear and the non-negativity constraint can artificially enhance the apparent spatial resolution if a point source image is reconstructed without any background. Thus, it was recommended that a background should be added to the point source data before reconstruction for resolution measurement. However, there has been no detailed study on the effect of the point source contrast on the measured spatial resolution. Here we use point source scans from a preclinical PET scanner to investigate the relationship between measured spatial resolution and the point source contrast. We also evaluate whether the reconstruction of an isolated point source is predictive of the ability of the system to resolve two adjacent point sources. Our results indicate that when the point source contrast is below a certain threshold, the measured FWHM remains stable. Once the contrast is above the threshold, the measured FWHM monotonically decreases with increasing point source contrast. In addition, the measured FWHM also monotonically decreases with iteration number for maximum likelihood estimate. Therefore, when measuring system resolution with an iterative reconstruction algorithm, we recommend using a low-contrast point source and a fixed number of iterations.

Value analysis of postoperative staging imaging for asymptomatic, early-stage breast cancer: implications of clinical variation on utility and cost.

BACKGROUND: Routine staging imaging for early-stage breast cancer is not recommended. Despite this, there is clinical practice variation with imaging studies obtained for asymptomatic patients with a positive sentinel node (SN+). We characterize the utility, cost, and clinical implications of imaging studies obtained in asymptomatic SN+ patients. METHODS: A retrospective review was performed of asymptomatic, clinically node-negative patients who were found to have a positive sentinel node after surgery. The type of imaging, subsequent tests/interventions, frequency of additional malignancy detected, and costs were recorded. RESULTS: From April 2009 to April 2013, a total of 50 of 113 (44%) asymptomatic patients underwent staging imaging for a positive sentinel node; 11 (22%) patients had at least 1 subsequent imaging study or diagnostic intervention. No instance of metastatic breast cancer was identified, with a total cost of imaging calculated at $116,905. CONCLUSIONS: Staging imaging for asymptomatic SN+ breast cancer demonstrates clinical variation. These tests were associated with low utility, increased costs, and frequent false positives leading to subsequent testing/intervention. Evidence-based standardization may help increase quality by decreasing unnecessary variation and cost.