Regan Butterfield

Comparison of Whole-Body PET/CT, Dedicated High-Resolution Head and Neck PET/CT, and Contrast-Enhanced CT in Preoperative Staging of Clinically M0 Squamous Cell Carcinoma of the Head and Neck

The purpose of this study was to compare optimized whole-body (WB) and dedicated high-resolution contrast-enhanced PET/CT protocols and contrast enhanced CT in the preoperative staging of primary squamous cell carcinoma of the head and neck. Methods: A total of 44 patients with clinically M0 squamous cell carcinoma of the head and neck underwent primary tumor resection and neck dissection within 6 wk of diagnostic imaging. Imaging consisted of a standard WB PET/CT protocol without intravenous contrast enhancement, followed by a high-resolution dedicated head and neck (HN) PET/CT protocol, which included diagnostic-quality contrast-enhanced CT (CECT). Imaging results were compared with histopathology. A 5-point scale was used to designate primary tumor localization and the presence of lymph node metastasis on a per-patient and per-level basis. For cervical nodes, receiver-operating-characteristic curves were generated to determine the differences in performance between the WB and HN PET/CT protocols and CECT. Sensitivity, specificity, positive and negative predictive values, and accuracy were calculated for primary tumor and cervical nodes. Results: No statistical difference was observed between WB and HN PET/CT protocols, both of which significantly outperformed CECT, in the evaluation of the primary tumor. The performance of the HN PET/CT protocol was superior to that of the WB PET/CT in the detection of cervical node metastases, achieving statistical significance on a per-level basis and approaching significance on a per-patient basis, with the greatest advantage in the detection of small positive lymph nodes (<15 mm). No significant difference was observed between the WB PET/CT protocol and CECT in nodal staging, either on a per-patient or on a per-level basis. Conclusion: The primary advantage of the dedicated HN PET/CT protocol over the WB protocol or CECT in the staging of head and neck cancer is in the detection of small lymph node metastases.

Estimating myocardial perfusion from dynamic contrast-enhanced CMR with a model-independent deconvolution method

BackgroundModel-independent analysis with B-spline regularization has been used to quantify myocardial blood flow (perfusion) in dynamic contrast-enhanced cardiovascular magnetic resonance (CMR) studies. However, the model-independent approach has not been extensively evaluated to determine how the contrast-to-noise ratio between blood and tissue enhancement affects estimates of myocardial perfusion and the degree to which the regularization is dependent on the noise in the measured enhancement data. We investigated these questions with a model-independent analysis method that uses iterative minimization and a temporal smoothness regularizer. Perfusion estimates using this method were compared to results from dynamic 13N-ammonia PET.ResultsAn iterative model-independent analysis method was developed and tested to estimate regional and pixelwise myocardial perfusion in five normal subjects imaged with a saturation recovery turboFLASH sequence at 3 T CMR. Estimates of myocardial perfusion using model-independent analysis are dependent on the choice of the regularization weight parameter, which increases nonlinearly to handle large decreases in the contrast-to-noise ratio of the measured tissue enhancement data. Quantitative perfusion estimates in five subjects imaged with 3 T CMR were 1.1 ± 0.8 ml/min/g at rest and 3.1 ± 1.7 ml/min/g at adenosine stress. The perfusion estimates correlated with dynamic 13N-ammonia PET (y = 0.90x + 0.24, r = 0.85) and were similar to results from other validated CMR studies.ConclusionThis work shows that a model-independent analysis method that uses iterative minimization and temporal regularization can be used to quantify myocardial perfusion with dynamic contrast-enhanced perfusion CMR. Results from this method are robust to choices in the regularization weight parameter over relatively large ranges in the contrast-to-noise ratio of the tissue enhancement data.

Comparison of 18F-fluorodeoxyglucose and 18F- fluorothymidine PET in differentiating radiation necrosis from recurrent glioma

Purpose The objective was to compare 18F-fluorodeoxyglucose (FDG) and 18F-fluorothymidine (FLT) PET in differentiating radiation necrosis from recurrent glioma. Materials and Methods Visual and quantitative analyses were derived from static FDG PET and static and dynamic FLT PET in 15 patients with suspected recurrence of treated grade 2 glioma or worse with a new focus of Gd contrast enhancement on MRI. For FDG PET, SUVmax and the ratio of lesion SUVmax to the SUVmean of contralateral white matter were measured. For FLT PET, SUVmax and Patlak-derived metabolic flux parameter Kimax were measured for the same locus. A 5-point visual confidence scale was applied to FDG PET and FLT PET. Receiver operating curve analysis was applied to visual and quantitative results. Differences between recurrent tumor and radiation necrosis were tested by Kruskal-Wallis analysis. On the basis of follow-up Gd-enhanced MRI, lesion-specific recurrent tumor was defined as a definitive increase in size of the lesion, and radiation necrosis was defined as stability or regression. Results For FDG SUVmax, the FDG ratio of lesion–white matter, and FLT Kimax, there was a significant difference between mean values for recurrent tumor and radiation necrosis. Recurrent tumor was best identified by the FDG ratio of lesion–contralateral normal white matter (area under the curve of 0.98, confidence interval of 0.91 to 1.00, sensitivity of 100%, and specificity of 75% for an optimized cutoff value of 1.82). Conclusions Both quantitative and visual determinations allow accurate differentiation between recurrent glioma and radiation necrosis by both FDG and FLT PET. In this small series, FLT PET offers no advantage over FDG PET.

18F-FDG PET in the Evaluation of Acuity of Deep Vein Thrombosis

Purpose 18F-FDG PET has been used for vascular disease, but its role in deep vein thrombosis (DVT) remains prospectively unexplored. Patients and Methods Whole-body 18F-FDG PET/CT scans were performed in patients 1 to 10 weeks after onset of symptomatic DVT (n = 12) and in control subjects without DVT (n = 24). The metabolic activity (SUVmax) of thrombosed and contralateral nonthrombosed vein segments was determined. The sensitivity and specificity of 18F-FDG PET/CT for the diagnosis of DVT were determined by receiver operating characteristic curve analyses. In 2 patients with DVT, changes in the metabolic activity of thrombosed vein segments in serial 18F-FDG PET scans. Results The metabolic activity in thrombosed veins [SUVmax, 2.41 (0.75)] was visually appreciable and significantly higher than in nonthrombosed veins in either the contralateral extremity of patients with DVT [SUVmax, 1.09 (0.25), P = 0.007] or control subjects [1.21 (0.22), P < 0.001]. The area under the receiver operating characteristic curve for SUVmax was 0.9773 (P < 0.001), indicating excellent accuracy. An SUVmax threshold of greater than 1.645 was 87.5% sensitive and 100% specific for DVT. Metabolic activity in thrombosed veins correlated significantly with time from DVT symptom onset (decrease in SUVmax of 0.02/d, P < 0.05). Best-fit-line analyses suggested that approximately 84 to 91 days after acute DVT, the maximum metabolic activity of thrombosed veins would return to normal levels. Conclusions 18F-FDG PET/CT is accurate for detecting acute symptomatic, proximal DVT. Metabolic activity in thrombosed veins decreases with time, suggesting that 18F-FDG PET may be helpful in assessing the age of the clot.

Amyloid Deposition and Cognition in Older Adults: The Effects of Premorbid Intellect

Although amyloid deposition remains a marker of the development of Alzheimers disease, results linking amyloid and cognition have been equivocal. Twenty-five community-dwelling non-demented older adults were examined with (18)F-flutemetamol, an amyloid imaging agent, and a cognitive battery, including an estimate of premorbid intellect and the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). In the first model, (18)F-flutemetamol uptake significantly correlated with the Delayed Memory Index of the RBANS (r = -.51, p = .02) and premorbid intellect (r = .43, p = .03). In the second model, the relationship between (18)F-flutemetamol and cognition was notably stronger when controlling for premorbid intellect (e.g., three of the five RBANS Indexes and its Total score significantly correlated with (18)F-flutemetamol, rs = -.41 to -.58). Associations were found between amyloid-binding (18)F-flutemetamol and cognitive functioning in non-demented older adults. These associations were greatest with delayed memory and stronger when premorbid intellect was considered, suggesting that cognitive reserve partly compensates for the symptomatic expression of amyloid pathology in community-dwelling elderly.