Role of Combined 68Ga-DOTATOC and 18F-FDG Positron Emission Tomography/Computed Tomography in the Diagnostic Workup of Pancreas Neuroendocrine Tumors: Implications for Managing Surgical Decisions.

OBJECTIVES: Ga-DOTATOC (Ga) positron emission tomography (PET)/computed tomography (CT) is recommended in the workup of pancreas neuroendocrine tumors (PanNETs); evidence suggests that F-FDG (F) PET/CT can also provide prognostic information. Aims of this study were to assess the role of combined Ga- and F-PET/CT in the evaluation of grade (G) 1-2 PanNETs and to test the correlation between F-PET/CT positivity and tumor grade. METHODS: Preoperative Ga- and F-PET/CT of 35 patients with surgically resected G1-2 PanNETs were evaluated. For grading, the 2010 World Health Organization Classification was used; an ancillary analysis with Ki67 cutoffs at 5% to 20% was conducted. Correlation between F-PET/CT positivity (SUVmax > 3.5) and grade was assessed. RESULTS: Of 35 PanNETs, 28.6% and 71.4% were G1 and G2 as per World Health Organization. Ga-PET/CT showed high sensitivity (94.3%) in detecting G1-2 PanNETs. F-PET/CT was positive in 20% and 76% G1 and G2 tumors (P = 0.002). F-PET/CT identified G2 PanNETs with high positive predictive value (PPV, 90.5%). F-PET/CT correlated with tumor grade also in the ancillary analysis (P = 0.009). CONCLUSIONS: The high sensitivity of Ga-PET/CT in NET detection is known. The high PPV of F-PET/CT in the identification of G2 forms suggests its potential role in PanNETs prognostication and risk stratification.

Impact of 18F-Choline PET/CT in the Decision-Making Strategy of Treatment Volumes in Definitive Prostate Cancer Volumetric Modulated Radiation Therapy.

INTRODUCTION: Aim of the study is to evaluate the impact of Cho-PET/CT in decision-making strategy of patients with localized prostate cancer (PC) eligible to definitive radiotherapy (RT). MATERIALS AND METHODS: Sixty patients Cho-PET/CT before RT were prospectively enrolled. All patients were treated with volumetric modulated arc therapy with simultaneous integrated boost in 28 fractions. Androgen deprivation therapy was prescribed according to National Comprehensive Cancer Network (NCCN) risk classification. Therapeutic strategy based on the Cho-PET/CT evaluation was compared with the strategy that would have been proposed in case of PET not available and/or not strictly indicated, according to international and national PC guidelines. RESULTS: Cho-PET/CT was positive in 57 cases (95%): T in 45 (79%); T in combination with N in 8 (14%); and M (bone) in combination with T or N, or both, in 4 (7%). After Cho-PET/CT, patients were stratified as follows: 26 (43%) low risk, 10 (16%) intermediate risk, and 24 (41%) high risk. Cho-PET/CT shifted treatment indication in 13 cases (21%). The changes regarding radiation treatment volumes were as follows: 6 intermediate risk (10%) shifted to high risk and consequently were irradiated on prostate, seminal vesicles, and pelvic nodes PTVs; in 7 high risk (11%), the Cho-PET/CT showed bone and/or N uptake, and consequently, a simultaneous integrated boost on PET positive sites was prescribed. CONCLUSIONS: Cho-PET/CT seems to be a promising diagnostic tool in patients who are candidates for radical RT and supporting the decision making in treatment planning, in particular in intermediate-high risk.

The effect of 18F-FDG-PET/CT respiratory gating on detected metabolic activity in lung lesions.

OBJECTIVE: Respiratory gated PET/CT (positron emission tomography/computed tomography) of the lung is expected to increase the accuracy of quantitative determinations in lesional activities, regardless of the gating method used; reasonably, respiratory gating should increase standard uptake value (SUV; and possibly decrease lesional size), on the basis of the reduction of the "smearing effect." However, literature data are very limited, particularly for in vivo studies. The objective of this article is to test the SUV variations in a large group of lung lesion studies. METHODS: A group of 26 consecutive positive studies (21 men, 5 women, age 36-84, mean 68), performed on patients referred to our institution for known or suspected lung cancer, are examined. All studies were performed both with conventional PET/CT total body scan and with Real-Time Position Management (RPM) triggered selective gated study of the thorax. Four studies were considered technically unsatisfactory and were discarded; the remaining 22 studies are the object of this work. Max lesional SUVs were evaluated in both settings by semi-automated algorithms; for the gated studies, both values of the bin that showed more relevant variations from the clinical routinary study ("best bin") and an average value that was calculated over all bins were determined. Results were compared on a one-to-one basis. RESULTS: In conventional, SUV showed a mean +/- standard deviation (SD) value of 9.2 +/- 6.9 (range 0.9-26). In the averaged gated studies, the mean +/- SD value was 13.4 +/- 11.7 (range 1.4-47); in the "best bin" dataset the mean +/- SD was 14.9 +/- 12.9, ranging from 1.6 to 53.1. In general, the use of respiratory trigger induced rather variable but overall consistent increases in SUV. If the percentage variations in the average trigger dataset are considered, there is an average increase of +60%, SD +/- 97 (P < 0.05). Similar results are found in the "best bin" dataset, the average percentage increase in SUV values being +77.2% (SD +/- 04.6). CONCLUSIONS: In lung cancer, triggering procedures increase the signal to noise ratio. The increase in SUV determined by gating is very variable, but generally relevant. This could lead to an SUV values cut-off revision, and may have an impact on smaller lesions detection.

Pre-therapy hyperfunctioning follicular thyroid carcinoma evaluation with I-131 whole-body scan and with F-18 FDG PET/CT.

We describe a patient with persistent hyperthyroidism after total thyroidectomy for toxic multinodular goiter and without therapy with levothyroxine evaluated with I-131 whole-body scan and with F-18 FDG PET/CT scan. Scintigraphy performed 48 hours after radiopharmaceutical administration showed many areas of focal radioiodine uptake. A week later we performed a PET/CT scan to better localize the anatomic site of the iodine-positive lesions. Both scans, performed after methimazole withdrawal, visualized the same lesions, and these results were used as a guide for biopsy. Histologic examination was consistent with metastatic follicular thyroid carcinoma.

Cerebellar vermis relative hypermetabolism: an almost constant PET finding in an injured brain.

Cortical alterations of brain metabolism, as seen in PET, obviously depend on the nature of the damage (either mechanical, toxic, anoxic, or other). However, some subcortical abnormalities seem to occur rather frequently regardless of the extension, position and cause of the damage. In particular, relative cerebellar vermis activation seems to be frequently encountered. The aim of this work was to determine the incidence of this pattern in a heterogeneous population of brain trauma, and to compare it on a quantitative basis with a group of age-sex matched controls. The case records of this study consist of 58 consecutive patients, 44 males, 14 females, age 14-69 (median 34) 44 traumatic, 8 anoxic, 4 vascular and 2 toxic injuries. In the trauma group, the visualization of the cerebellar vermis was readily appreciable as a consistent majority of cases. In particular, the mean vermis/cerebellum ratio (calculated by appropriate ROI positioning) was 1.26 +/- 0.17 SD (range 0.92-1.82); in the control group the same parameters showed much less dispersion: average 0.92 +/- 0.06, range 0.80-1.10 (P < 0.005). If, on the basis of the normal group data, a cut-off value of 1 is accepted for the v/c ratio, it is noted that 54/57 trauma patients (95%) showed a ratio above this value. In conclusion, a hypermetabolic cerebellar vermis is a common finding in a damaged brain, regardless of the nature of the trauma (probably due to the relative preservation compared with other structures of alternative metabolic pathways), and seems to be the hallmark of the injured brain.