Data-driven respiratory gating for ventilation/perfusion lung scan.

BACKGROUND: Ventilation/perfusion lung scan is subject to blur due to respiratory motion whether with planar acquisition or single photon emission computed tomography (SPECT). We propose a data-driven gating method for extracting different respiratory phases from lung scan list-mode or dynamic data. METHODS: The algorithm derives a surrogate respiratory signal from an automatically detected diaphragmatic region of interest. The time activity curve generated is then filtered using a Savitzky-Golay filter. We tested this method on an oscillating phantom in order to evaluate motion blur decrease and on one lung SPECT. RESULTS: Our algorithm reduced motion blur on phantom acquisition: mean full width at half maximum 8.1 pixels on non-gated acquisition versus 5.3 pixels on gated acquisition and 4.1 pixels on reference image. Automated detection of the diaphragmatic region and time-activity curves generation were successful on patient acquisition. CONCLUSIONS: This algorithm is compatible with a clinical use considering its runtime. Further studies will be needed in order to validate this method.

Preoperative 18F-FDG PET/CT in Patients with Presumed Localized Colon Cancer: A Prospective Study with Long-Term Follow-Up.

We analyzed whether preoperative 18F-FDG PET/CT adds to conventional primary staging in patients with presumed non-metastatic colonic cancer (CC). The prognostic role of 18F-FDG uptake in the primary tumor was evaluated after a mean follow-up of 15 years. Patients with a new diagnosis of presumed localized CC were prospectively enrolled and underwent presurgical 18F-FDG PET/CT. For each colon lesion, SUVmax, SUVpeak, TLG, and MTV were assessed and tested as prognostic factors. Forty-eight patients were included. Post-surgery pathology identified a total of 103 colon lesions, including 58 invasive adenocarcinomas, 4 in situ adenocarcinomas, 3 adenomas with high-grade dysplasia, and 38 adenomas with low-grade dysplasia. Per lesion sensitivity, specificity, positive (PPVs) and negative predictive values (NPVs) for colonic primary tumor detection were 78%, 97%, 98%, and 73% for conventional workup, and 94%, 87%, 92%, and 89% for 18F-FDG PET/CT. Only sensitivity was significantly different between 18F-FDG PET/CT and conventional workup. PET detected an additional ten pathological colonic lesions in seven patients. SUVmax, SUVpeak, and TLG showed significant differences between invasive adenocarcinomas, in situ adenocarcinomas, and high-grade dysplasia compared to low-grade dysplasia. There was a statistically significant difference between pT1-pT2 and pT3-pT4 adenocarcinomas. On patient-based analysis, sensitivity, specificity, PPV, and NPV for nodal staging were 22%, 84%, 44%, and 65% for CECT, and 33%, 90%, 67%, and 70% for 18F-FDG PET/CT, without a statistically significant difference. PET/CT also identified unknown metastatic spread and one synchronous lung cancer in four patients. Overall, 18F-FDG PETCT had an additional diagnostic value in 11 out of 48 patients (23%). 18F-FDG uptake of the primary tumor did not predict nodal or distant metastases. The difference in disease-free survival categorized by median SUVmax, SUVpeak, TLG, and MTV was not significant. Finally, preoperative 18F-FDG PET/CT is valuable in detecting potential colon lesions not visualized by conventional workups, especially in cases of incomplete colonoscopy. It effectively highlights distant metastases but exhibits limitations for N staging. Mainly due to the relatively small sample size, the quantitative analysis of 18F-FDG uptake in the primary tumor did not reveal any association with recurrence or disease-free survival, adding no significant prognostic information.

Comparison of FDG-PET/CT and MR with diffusion-weighted imaging for assessing peritoneal carcinomatosis from gastrointestinal malignancy.

OBJECTIVES: To assess the accuracy of FDG-PET/CT and MR with diffusion-weighted imaging (MR-DWI) for diagnosing peritoneal carcinomatosis (PC) from gastrointestinal malignancies. METHODS: Thirty consecutive patients referred for staging of gastrointestinal malignancy underwent FDG-PET/CT and MR-DWI in this retrospective study. Extent of PC was characterised by dividing the peritoneal cavity into three sites in each patient: right and left supramesocolic areas and inframesocolic level (total 90 sites). Presence of PC was confirmed either by surgery (18/30) or by follow-up (12/30). RESULTS: PC was confirmed in 19 patients (19/30). At a total of 90 sites, 27 showed proven PC. On a patient-based analysis, sensitivity, specificity, PPV, NPV and accuracy were respectively 84%, 73%, 84%, 73% and 80% for PET/CT and 84%, 82%, 89%, 75% and 83% for MR-DWI. On a site-based analysis, overall sensitivity and specificity of PET/CT (63%, 90%) and MR-DWI (74%, 97%) were not statistically different (P = 0.27). In the supramesocolic area, MR-DWI detected more sites involved than PET/CT (7/9 vs. 4/9). The sensitivities of PET and MR were lower for subcentimetre tumour implants (42%, 50%). Interobserver agreement was very good for PET/CT and good for MR-DWI. CONCLUSIONS: FDG-PET/CT and MR-DWI showed similar high accuracy in diagnosing PC. Both techniques underestimated the real extent of PC because of decreased sensitivity for subcentimetre lesions. KEY POINTS: FDG-PET/CT and MR-DWI showed similar high accuracy for diagnosing peritoneal carcinomatosis. • In the supramesocolic area, MR-DWI could be more sensitive than PET/CT. • Both techniques showed lower sensitivity for subcentimetre lesions. • Interobserver agreement was very good for PET/CT and good for MR-DWI.

Vertebra segmentation based on two-step refinement.

Knowledge of vertebra location, shape, and orientation is crucial in many medical applications such as orthopedics or interventional procedures. Computed tomography (CT) offers a high contrast between bone and soft tissues, but automatic vertebra segmentation remains difficult. Hence, the wide range of shapes, aging, and degenerative joint disease alterations as well as the variety of pathological cases encountered in an aging population make automatic segmentation sometimes challenging. Besides, daily practice implies a need for affordable computation time. This paper aims to present a new automated vertebra segmentation method (using a first bounding box for initialization) for CT 3D data which tackles these problems. This method is based on two consecutive steps. The first one is a new coarse-to-fine method efficiently reducing the data amount to obtain a coarse shape of the vertebra. The second step consists in a hidden Markov chain (HMC) segmentation using a specific volume transformation within a Bayesian framework. Our method does not introduce any prior on the expected shape of the vertebra within the bounding box and thus deals with the most frequent pathological cases encountered in daily practice. We experiment this method on a set of standard lumbar, thoracic, and cervical vertebrae and on a public dataset, on pathological cases, and in a simple integration example. Quantitative and qualitative results show that our method is robust to changes in shapes and luminance and provides correct segmentation with respect to pathological cases.

18F-fluorodihydroxyphenylalanine PET/CT in patients with neuroendocrine tumors of unknown origin: relation to tumor origin and differentiation.

UNLABELLED: This work was performed to evaluate the performance of (18)F-fluorodihydroxyphenylalanine ((18)F-FDOPA) PET/CT in detecting primary neuroendocrine tumors (NETs) occult on morphologic and functional imaging, in relation to tumor origin and differentiation. METHODS: A retrospective study of NET patients who were investigated with (18)F-FDOPA PET/CT imaging in 2 academic endocrine tumor centers was conducted. Only patients with negative conventional and somatostatin receptor scintigraphy (SRS) results were studied. RESULTS: Twenty-seven patients were evaluated with (18)F-FDOPA PET/CT, 23 at their initial staging and 4 during their follow-up. The primary occult NET was localized by (18)F-FDOPA PET/CT in 12 patients (overall sensitivity, 44%; 52% in patients evaluated at initial diagnosis), leading to tumor resection in all cases. The primary tumors were distributed and graded as follows: 1 duodenum G2 lesion, 7 ileum G2 lesions, 2 terminal ileum G1 lesions, 1 pancreas G2 lesion, and 1 gallbladder G3 lesion. Patients with positive (18)F-FDOPA PET/CT results had higher values of serum chromogranin A (100% vs. 20%, P = 0.0003), serotonin, or urinary 5-hydroxyindolacetic acid (83% vs. 20%, P = 0.003). Two false-negative results were related to poorly differentiated duodenal and prostatic NETs (G3). (18)F-FDOPA PET/CT showed more metastatic anatomic regions than SRS in 17 patients. CONCLUSION: (18)F-FDOPA PET appears to be a sensitive functional imaging tool for the detection of primary NETs occult on SRS, especially tumors with a well-differentiated pattern and serotonin secretion.

18F-fluorocholine uptake in a case of adrenal incidentaloma: possible diagnostic pitfall or potential tool for adrenocortical tumors characterization?

The understanding of radiotracer's physiological biodistribution as well as the potential source of false-positive results is crucial for an accurate diagnostic interpretation of (18)F-fluorocholine PET/CT examination in patients with prostate cancer. We illustrate the results of whole-body (18)F-fluorocholine PET/CT in a 79-year-old man with biochemical suspicion of prostate adenocarcinoma relapse. PET/CT study showed a focally increased (18)F-fluorocholine uptake, characterizing an incidentally found adrenocortical adenoma. Finally, we draw oncologists' attention to the possible false-positive results of (18)F-fluorocholine PET related to benign and unsuspected adrenocortical lesions in patients with a history of prostate malignancy.

FDG-PET/CT findings of atypical (bizarre/symplastic) uterine leiomyoma in a patient with abdominal leiomyosarcoma.

Atypical (bizarre) leiomyoma is a benign uterine smooth-muscle tumor characterized by a) a significant number of cells with dense eosinophilic cytoplasm and enlarged, bizarre single/multiple hyperchromatic or multiple nuclei without tumor necrosis and b) poor mitotic activity. We report the case of an atypical (bizarre) leiomyoma revealed by focal fluoro-deoxyglucose (FDG) uptake during a PET-CT in a patient with relapsing abdominal and retroperitoneal leiomyosarcoma.

The rim sign: FDG-PET/CT pattern of pulmonary infarction.

OBJECTIVE: We aimed to describe a pattern of rim uptake observed in lung infarction on FDG-PET/CT, called the "rim sign." It was defined as a continuous slight FDG uptake along the border of a subpleural consolidation without uptake within the consolidation. METHODS: We retrospectively reviewed the FDG-PET/CT studies of 400 patients referred for thoracic oncological workup from November 2010 to July 2011. The rim sign was observed in six patients who had confirmed pulmonary infarction (PI) on MDCT showing acute pulmonary embolism (n = 4) or tumoral arterial obstruction (n = 2). RESULTS: Eight PIs in the six patients exhibited the rim sign with slight uptake (median SUV(max): 3.6, 2.2-6.8) and median size of 48.5 mm (30-74). On MDCT, central lucencies, triangular shape and vessel sign were observed in 5/8, 4/8 and 1/8 cases, respectively. Two out of the eight PIs exhibited only the rim sign and none the suggestive MDCT sign. CONCLUSION: The rim sign is easily recognisable at FDG-PET/CT and is strongly suggestive of PI. This pattern can be observed even in the absence of suggestive findings on MDCT. Recognition of this sign should prompt investigations for pulmonary embolism. MAIN MESSAGES: • The rim sign is a slight FDG uptake around an area of subpleural consolidation • The rim sign is strongly suggestive of pulmonary infarction • Recognition of the rim sign should prompt investigations for pulmonary embolism.

Terminal ileum neuroendocrine incidentaloma in a patient with sporadic medullary thyroid carcinoma: findings from 18F-FDOPA PET/CT investigation.

An incidentaloma is a mass lesion incidentally found, of uncertain significance, and clinically inert. Although incidentaloma is commonly referred to designate an adrenal lesion, it can denote any incidental lesion of other organs. We describe the unexpected finding of an ileum neuroendocrine incidentaloma detected by 6-L-(18F)-fluorodihydroxyphenylalanine (FDOPA) PET/CT performed in an asymptomatic patient with history of sporadic medullary thyroid carcinoma and biochemical suspicion of recurrent disease. This report underlines the high FDOPA PET/CT sensitivity for neuroendocrine tumor detection and the need of complementary diagnostic investigations elucidating the significance of extraphysiological FDOPA intestinal uptake, even in patients with unrelated primary cancer.

Nuclear medicine imaging of gastro-entero-pancreatic neuroendocrine tumors. The key role of cellular differentiation and tumor grade: from theory to clinical practice.

Nuclear medicine imaging is a powerful diagnostic tool for the management of patients with gastro-entero-pancreatic neuroendocrine tumors, mainly developed considering some cellular characteristics that are specific to the neuroendocrine phenotype. Hence, overexpression of specific trans membrane receptors as well as the cellular ability to take up, accumulate, and decarboxylate amine precursors have been considered for diagnostic radiotracer development. Moreover, the glycolytic metabolism, which is not a specific energetic pathway of neuroendocrine tumors, has been proposed for radionuclide imaging of neuroendocrine tumors. The results of scintigraphic examinations reflect the pathologic features and tumor metabolic properties, allowing the in vivo characterization of the disease. In this article, the influence of both cellular differentiation and tumor grade in the scintigraphic pattern is reviewed according to the literature data. The relationship between nuclear imaging results and prognosis is also discussed. Despite the existence of a relationship between the results of scintigraphic imaging and cellular differentiation, tumor grade and patient outcome, the mechanism explaining the variability of the results needs further investigation.