In tumor response monitoring studies with 18F-FDG PET, maximum standardized uptake value (SUVmax) is commonly applied as a quantitative metric. Although it has several advantages due to its simplicity of determination, concerns about the influence of image noise on single-pixel SUVmax persist. In this study, we measured aspects of bias and reproducibility associated with SUVmax and the closely related peak SUV (SUVpeak) using real patient data to provide a realistic noise context. Methods List-mode 3-dimensional PET data were acquired for 15 min over a single bed position in twenty 18F-FDG oncology patients. For each patient, data were sorted so as to form 2 sets of images: respiration-gated images such that each image had statistical quality comparable to a 3 min/bed position scan, and 5 statistically independent (ungated) images of different durations (1, 2, 3, 4, and 5 min). Tumor SUVmax and SUVpeak (12-mm-diameter spheric region of interest positioned so as to maximize the enclosed average) were analyzed in terms of reproducibility and bias. The component of reproducibility due to statistical noise (independent of physiologic and other variables) was measured using paired SUVs from 2 comparable respiration-gated images. Bias was measured as a function of scan duration. Results Replicate tumor SUV measurements had a within-patient SD of 5.6% ± 0.9% for SUVmax and 2.5% ± 0.4% for SUVpeak. SUVmax had average positive biases of 30%, 18%, 12%, 4%, and 5% for the 1-, 2-, 3-, 4-, and 5-min images, respectively. SUVpeak was also biased but to a lesser extent: 11%, 8%, 5%, 1%, and 4% for the 1-, 2-, 3-, 4-, and 5-min images, respectively. Conclusion The advantages of SUVmax are best exploited when PET images have a high statistical quality. For images with noise properties typically associated with clinical whole-body studies, SUVpeak provides a slightly more robust alternative for assessing the most metabolically active region of tumor.

Purple urine bag syndrome (PUBS) is a unique disease entity characterized by an alarming purple discoloration of the urine secondary to recurrent urinary tract infections with indigo- and indirubin-producing bacteria. It is usually associated with prolonged urinary catheterization and chronic debilitated states. We hereby present a concise review of this rare phenomenon with historic perspectives, epidemiology, emphasizing on current concepts of etiology, pathogenesis, relevant clinical associations, treatment modalities, prognosis, and future directions in PUBS. In addition, we highlight an interesting occurrence of this intriguing phenomenon in a 39-year-old gentleman at our institution.

Purpose Although previous studies have demonstrated the prognostic value of positron emission tomography (PET) parameters in other malignancies, the role of PET in pancreatic cancer has yet to be well established. We analyzed the prognostic utility of PET for patients with locally advanced pancreatic cancer (LAPC) undergoing fractionated stereotactic body radiation therapy (SBRT). Materials and Methods Thirty-two patients with LAPC in a prospective clinical trial received up to 3 doses of gemcitabine, followed by 33 Gy in 5 fractions of 6.6 Gy, using SBRT. All patients received a baseline PET scan prior to SBRT (pre-SBRT PET). Metabolic tumor volume (MTV), total lesion glycolysis (TLG), and maximum and peak standardized uptake values (SUVmax and SUVpeak) on pre-SBRT PET scans were calculated using custom-designed software. Disease was measured at a threshold based on the liver SUV, using the equation Livermean + [2 × Liversd]. Median values of PET parameters were used as cutoffs when assessing their prognostic potential through Cox regression analyses. Results Of the 32 patients, the majority were male (n = 19, 59%), 65 years or older (n = 21, 66%), and had tumors located in the pancreatic head (n = 27, 84%). Twenty-seven patients (84%) received induction gemcitabine prior to SBRT. Median overall survival for the entire cohort was 18.8months (95% confidence interval [CI], 15.7–22.0). An MTV of 26.8 cm3 or greater (hazard ratio [HR] 4.46, 95% CI 1.64–5.88, P<.003) and TLG of 70.9 or greater (HR3.08,95%CI 1.18–8.02,P<.021) on pre-SBRT PET scan were associated with inferior overall survival on univariate analysis. Both pre-SBRT MTV (HR 5.13, 95% CI 1.19–22.21, P = .029) and TLG (HR 3.34, 95% CI 1.07–10.48, P = .038) remained independently associated with overall survival in separate multivariate analyses. Conclusions Pre-SBRT MTV and TLG are potential predictive factors for overall survival in patients with LAPC and may assist in tailoring therapy.

The coronary slow flow phenomenon (CSFP) is a disease entity characterized by slow progression of angiographic contrast in the coronary arteries in the absence of stenosis in the epicardial vessels. CSFP has a diverse presentation from mild chest discomfort to ST-segment elevation myocardial infarction. It can also have severe morbidity and mortality implications and can significantly hamper the quality of life of those affected. In this paper we present two patients with CSFP highlighting the diverse spectrum of presentation. A concise review of the literature is also provided emphasizing the epidemiology, pathogenesis, diagnostic parameters, treatment modalities, and clinical significance of this phenomenon.

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Age, SUVmax, peak SUV, and total lesion glycolysis (i.e., tumor glycolytic activity) of the primary tumor are associated with PFS, and tumor glycolytic activity is associated with OS in patients with pancreatic adenocarcinoma.

18 F-FDG PET/CT has shown increased accuracy, compared with morphologic imaging, in differentiating malignant peripheral nerve sheath tumors (MPNSTs) from benign neurofibromas (BNFs) in patients with neurofibromatosis type 1 (NF1). Delayed 18 F-FDG PET imaging typically enhances malignant tumor to background. Our goal was to compare the effectiveness of early (1-h) and delayed (4-h) 18 F-FDG PET/CT imaging in differentiating MPNSTs from BNFs in patients with NF1, with and without liver activity normalization. Methods: NF1 patients presenting new symptoms or enlarging lesions were clinically evaluated with early and delayed 18 F-FDG PET/CT imaging. SUL max (maximum standardized uptake value derived for lean body) and SUL max/liver (lesion uptake adjusted to mean liver activity) were obtained for all sites identified with abnormal metabolic activity. Qualitative and quantitative evaluations, including receiver-operating-characteristic (ROC) comparison of early and delayed imaging sessions, were performed. Histopathology and clinical follow-up (1-9 y) were considered as a gold standard. Results: Forty-one NF1 patients with early and delayed 18 F-FDG PET/CT scans were identified, and 93 lesions were retrospectively analyzed, representing 24 MPNSTs (all histologically confirmed) and 69 BNFs (26 histologically confirmed). Qualitative evaluation on early imaging showed sensitivity, specificity, positive predictive value, and negative predictive value for separating MPNSTs from BNFs of 91%, 84%, 67%, and 96% versus 91%, 81%, 63%, and 96%, respectively, on 4-h delayed imaging. The mean SUL max was significantly higher for MPNSTs than BNFs on both early scans (6.5 vs. 2.0, P , 0.01) and delayed imaging (8.3 vs. 2.3, P , 0.02). However, SUL max overlap between benign and malignant lesions persisted even after normalization to mean liver activity. ROC-derived best SUL max cutoffs were 3.2 on early (area under the curve, 0.973) and 4.1 on delayed scans (area under the curve, 0.978). ROC analysis for SUL max/liver improved test specificity (94% vs. 87%, P , 0.05) on early and (93% vs. 88%, P , 0.05) on delayed imaging. Conclusion: Qualitative interpretation of 18 F-FDG PET/CT discriminates MPNSTs from BNFs in NF1 patients with similar accuracy on both early and delayed imaging. Quantitative data showed better sensitivity on delayed acquisition and best test specificity with lesion SUL max normalization to liver activity, more so than with delayed imaging at 4 h.

Multi-Bed FDG PETtCT as applied to oncologic imaging is currently widely and routinely used for assessment of localized and metastatic disease involvement. In the past, based on conventional (single-bed) dynamic PET imaging, standard tracer kinetic modeling techniques have been developed to estimate the FDG uptake rate Kj. However, routine clinical multi-bed FDG PET imaging commonly involves a single time frame per bed, i.e. static imaging, and the standardized uptake value (SDV), a surrogate of metabolic activity, is employed to estimate the uptake rate Kj• The accuracy depends on two conditions:(i) in the voxel or region of interest, contribution of non-phosphorylated FDG is negligible relative to phosphorylated FDG, and (ii) time integral of plasma FDG concentration is proportional to injected dose divided by lean body mass, which can fail in clinical FDG PET imaging and pose problems in differentiating malignant from benign tumors. The objective of the proposed work is to facilitate, for the fist time, a transition from static to dynamic multi-bed FDG PETtCT imaging in clinically feasible times where, given the challenge of sparse tem poral sampling at each bed, novel dynamic acquisition schemes should be employed to yield quantitative whole-body imaging of FDG uptake. Thus, a set of novel dynamic multi-bed PET image acquisition schemes have been modeled, using Monte Carlo simulations, to quantitatively evaluate the clinical feasibility of the method and optimize the number of passes per bed and the total study duration. It has been determined that a data acquisition scheme consisting of 6 whole-body passes and constant time frames of 45sec produces parametric images with the optimal noise vs. bias performance. Finally, clinical whole-body patient data have been acquired dynamically and results demonstrate the potential of the proposed method in enhancing treatment response monitoring capabilities of clinical PET studies.