Distribution of artifactual gas on post-mortem multidetector computed tomography (MDCT).

PURPOSE: We investigated the incidence and distribution of post-mortem gas detected with multidetector computed tomography (MDCT) to identify factors that could distinguish artifactual gas from cardiac air embolism. MATERIAL AND METHODS: MDCT data of 119 cadavers were retrospectively examined. Gas was semiquantitatively assessed in selected blood vessels, organs, and body spaces (82 total sites). RESULTS: Seventy-four of the 119 cadavers displayed gas (62.2%; CI 95% 52.8-70.9), and 56 (75.7%) displayed gas in the heart. Most gas was detected in the hepatic parenchyma (40%), right heart (38% ventricle, 35% atrium), inferior vena cava (30% infrarenally, 26% suprarenally), hepatic veins (26% left, 29% middle, 22% right), and portal spaces (29%). Male cadavers displayed gas more frequently than female cadavers. Gas was detected 5-84 hours after death; therefore, the post-mortem interval could not reliably predict gas distribution (rho = 0.719, p < 0.0001). We found that a large amount of putrefaction-generated gas in the right heart was associated with aggregated gas bubbles in the hepatic parenchyma (sensitivity = 100%, specificity = 89.7%). In contrast, gas in the left heart (sensitivity = 41.7%, specificity = 100%) or in periumbilical subcutaneous tissues (sensitivity = 50%, specificity = 96.3%) could not predict gas due to putrefaction. CONCLUSION: This study is the first to show that the appearance of post-mortem gas follows a specific distribution pattern. An association between intracardiac gas and hepatic parenchymal gas could distinguish between post-mortem-generated gas and vital air embolism. We propose that this finding provides a key for diagnosing death due to cardiac air embolism.

Intérêt de la tomographie par émission de positons couplée à la scanographie (TEP/TDM) dans les cancers urologiques [Value of positron emission tomography and computer tomography (PET/CT) for urologic malignancies].

Positron emission tomography is a functional imaging technique that allows the detection of the regional metabolic rate, and is often coupled with other morphological imaging technique such as computed tomography. The rationale for its use is based on the clearly demonstrated fact that functional changes in tumor processes happen before morphological changes. Its introduction to the clinical practice added a new dimension in conventional imaging techniques. This review presents the current and proposed indications of the use of positron emission/computed tomography for prostate, bladder and testes, and the potential role of this exam in radiotherapy planning.

Dépistage du cancer pulmonaire par scanner thoracique [Computed tomography screening for lung cancer].

Lung cancer screening has been the focus of intense interest since the publication in 2011 of the NLST trial (National Lung Screening Trial) showing a mortality reduction in smokers undergoing 3-year screening by chest computed tomography. Although these data appear promising, many issues remain to be resolved, such as high rate of false positive cases, risk of overdiagnosis, optimal intervals between screens, duration of the screening process, feasibility, and cost. Structured screening programs appear crucial to guarantee patient information, technical quality, and multidisciplinary management. Despite these uncertainties, several guidelines already state that screening should be performed in patients at risk, whereas investigators stress that more data are needed. How should the primary care physician deal with individual patients requests? This review provides some clues on this complex issue.

Added prognostic value of myocardial blood flow quantitation in rubidium-82 positron emission tomography imaging

Les maladies cardiovasculaires restent la cause de mortalité la plus élevée dans le monde occidental. Il s'agit d'un processus long et complexe, dont l'infarctus du myocarde et la mort cardiaque ne sont que la fin d'un spectrum. La perfusion myocardique joue un rôle central dans l'évolution de la maladie et survient chronologiquement en amont de la dysfonction diastolique et systolique, ainsi que de l'infarctus du myocarde. Une meilleure compréhension de la Physiopathologie sous-jacente est cruciale dans le diagnostique et la prise en charge du patient. Dans ce sens, ce travail tente d'évaluer l'apport de l'évaluation de la perfusion myocardique évaluée par la tomographic à émission de positron (PET/CT) quant à la prédiction d'événements cardiovasculaires. De plus, l'apport de l'évaluation quantitative par rapport à l'évaluation qualitative a été démontré dans ce travail. Nous avons utilisé un radiotraceur unique au regard de ses caractéristiques. En effet, Le Rubidium-82 est un traceur qui ne nécessite pas d'un cyclotron pour sa fabrication, dès lors qu'il est produit par un générateur, rendant ainsi sa disponibilité un atout et un avantage potentiel lors de futurs implémentations à plus grande échelle. Ce travail démontre la supériorité de l'analyse de perfusion myocardique quantitative par rapport à l'analyse traditionnelle qualitative, ce qui n'était pas encore confirmé avec le Rubidium-82. Les résultats montrent une démarcation significative entre les différentes valeurs de perfusion quantitative/absolue, permettant de distinguer différentes populations plus ou moins à risque en terme de prédiction d'événements cardiaques futurs. Il est intéressant de noter que dans un modèle combinant l'analyse qualitative et quantitative proposé dans ce travail, l'inclusion des résultats les plus ischémiques obtenus par l'analyse qualitative avec les résultats de perfusion les plus bas en terme de flux myocardique absolu (analyse quantitative) démarque une population à très bas risque d'événements cardiovasculaires majeurs, une prédiction pouvant être observée surplus de 1'000 jours. Ces résultats forment un ajout significatif quant à l'évaluation de la perfusion myocardique par la médecine nucléaire, notamment par ce model intégratif proposé, lequel permet une prédiction précise et contributive dans le cadre de futurs événements cardiovasculaires majeurs.

Iterative image reconstruction techniques: cardiothoracic computed tomography applications.

Iterative image reconstruction algorithms provide significant improvements over traditional filtered back projection in computed tomography (CT). Clinically available through recent advances in modern CT technology, iterative reconstruction enhances image quality through cyclical image calculation, suppressing image noise and artifacts, particularly blooming artifacts. The advantages of iterative reconstruction are apparent in traditionally challenging cases-for example, in obese patients, those with significant artery calcification, or those with coronary artery stents. In addition, as clinical use of CT has grown, so have concerns over ionizing radiation associated with CT examinations. Through noise reduction, iterative reconstruction has been shown to permit radiation dose reduction while preserving diagnostic image quality. This approach is becoming increasingly attractive as the routine use of CT for pediatric and repeated follow-up evaluation grows ever more common. Cardiovascular CT in particular, with its focus on detailed structural and functional analyses, stands to benefit greatly from the promising iterative solutions that are readily available.

Micropapillary pattern in lung adenocarcinoma: aspect on 18F-fluorodeoxyglucose positron emission tomography/computed tomography imaging.

We diagnosed a non-small cell lung carcinoma in a 49-year-old female patient with the histopathological diagnosis of stage IIIB mixed bronchioloalveolar and papillary adenocarcinoma with extensive micropapillary feature, which was not visualized on the preoperative multimodality imaging with positron emission tomography (PET) and computed tomography (CT). The micropapillary component characterized by a unique growth pattern with particular morphological features can be observed in all subtypes of lung adenocarcinoma. Micropapillary component is increasingly recognized as a distinct entity associated with higher aggressiveness. Even the most modern multimodality PET/CT imaging technology may fail to adequately visualize this important component with highly relevant prognostic implications. Thus, the pathologist needs to consciously look for a micropapillary component in the surgical specimen or in preoperative biopsies or cytology. This may have potential future treatment implications, as adjuvant or neoadjuvant chemotherapy may be of relevance, even in the early stages of the disease.

18F-fluorodeoxyglucose positron emission tomography/computed tomography and magnetic resonance imaging in patients with liver metastases from uveal melanoma: results from a pilot study.

PURPOSE: F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) and MRI are used for detecting liver metastases from uveal melanoma. The introduction of new treatment options in clinical trials might benefit from early response assessment. Here, we determine the value of FDG-PET/CT with respect to MRI at diagnosis and its potential for monitoring therapy. MATERIAL AND METHODS: Ten patients with biopsy-proven liver metastases of uveal melanoma enrolled in a randomized phase III trial (NCT00110123) underwent both FDG-PET coupled with unenhanced CT and gadolinium-diethylene triamine pentaacetic acid-enhanced liver MRI within 4 weeks. FDG-PET and MRI were evaluated blindly and then compared using the ratio of lesion to normal liver parenchyma PET-derived standardized uptake value (SUV). The influence of lesion size and response to chemotherapy were studied. RESULTS: Overall, 108 liver lesions were seen: 34 (31%) on both modalities (1-18 lesions/patient), four (4%) by PET/CT only, and 70 (65%) by MRI only. SUV correlated with MRI lesion size (r=0.81, P<0.0001). PET/CT detected 26 of 33 (79%) MRI lesions of more than or equal to 1.2 cm, whereas it detected only eight of 71 (11%) lesions of less than 1.2 cm (P<0.0001). MRI lesions without PET correspondence were small (0.6±0.2 vs. 2.1±1.1 cm, P<0.0001). During follow-up (six patients, 30 lesions), the ratio lesion-to-normal-liver SUV diminished in size-stable lesions (1.90±0.64-1.46±0.50, P<0.0001), whereas it increased in enlarging lesions (1.56±0.40-1.99±0.56, P=0.032). CONCLUSION: MRI outweighs PET/CT for detecting small liver metastases. However, PET/CT detected at least one liver metastasis per patient and changes in FDG uptake not related to size change, suggesting a role in assessing early therapy response.

FIB-SEM tomography in biology.

Three-dimensional information is much easier to understand than a set of two-dimensional images. Therefore a layman is thrilled by the pseudo-3D image taken in a scanning electron microscope (SEM) while, when seeing a transmission electron micrograph, his imagination is challenged. First approaches to gain insight in the third dimension were to make serial microtome sections of a region of interest (ROI) and then building a model of the object. Serial microtome sectioning is a tedious and skill-demanding work and therefore seldom done. In the last two decades with the increase of computer power, sophisticated display options, and the development of new instruments, an SEM with a built-in microtome as well as a focused ion beam scanning electron microscope (FIB-SEM), serial sectioning, and 3D analysis has become far easier and faster.Due to the relief like topology of the microtome trimmed block face of resin-embedded tissue, the ROI can be searched in the secondary electron mode, and at the selected spot, the ROI is prepared with the ion beam for 3D analysis. For FIB-SEM tomography, a thin slice is removed with the ion beam and the newly exposed face is imaged with the electron beam, usually by recording the backscattered electrons. The process, also called "slice and view," is repeated until the desired volume is imaged.As FIB-SEM allows 3D imaging of biological fine structure at high resolution of only small volumes, it is crucial to perform slice and view at carefully selected spots. Finding the region of interest is therefore a prerequisite for meaningful imaging. Thin layer plastification of biofilms offers direct access to the original sample surface and allows the selection of an ROI for site-specific FIB-SEM tomography just by its pronounced topographic features.

The Four Different Types of Internal Hernia Occurring After Laparascopic Roux-en-Y Gastric Bypass Performed for Morbid Obesity: Are There Any Multidetector Computed Tomography (MDCT) Features Permitting Their Distinction?

BACKGROUND: Four different types of internal hernias (IH) are known to occur after laparoscopic Roux-en-Y gastric bypass (LRYGBP) performed for morbid obesity. We evaluate multidetector row helical computed tomography (MDCT) features for their differentiation. METHODS: From a prospectively collected database including 349 patients with LRYGBP, 34 acutely symptomatic patients (28 women, mean age 32.6), operated on for IH immediately after undergoing MDCT, were selected. Surgery confirmed 4 (11.6%) patients with transmesocolic, 10 (29.4%) with Petersen's, 15 (44.2%) with mesojejunal, and 5 (14.8%) with jejunojejunal IH. In consensus, 2 radiologists analyzed 13 MDCT features to distinguish the four types of IH. Statistical significance was calculated (p < 0.05, Fisher's exact test, chi-square test). RESULTS: MDCT features of small bowel obstruction (SBO) (n = 25, 73.5%), volvulus (n = 22, 64.7%), or a cluster of small bowel loops (SBL) (n = 27, 79.4%) were inconsistently present and overlapped between the four IH. The following features allowed for IH differentiation: left upper quadrant clustered small bowel loops (p < 0.0001) and a mesocolic hernial orifice (p = 0.0003) suggested transmesocolic IH. SBL abutting onto the left abdominal wall (p = 0.0021) and left abdominal shift of the superior mesenteric vessels (SMV) (p = 0.0045) suggested Petersen's hernia. The SMV predominantly shifted towards the right anterior abdominal wall in mesojejunal hernia (p = 0.0033). Location of the hernial orifice near the distal anastomosis (p = 0.0431) and jejunojejunal suture widening (p = 0.0005) indicated jejunojejunal hernia. CONCLUSIONS: None of the four IH seems associated with a higher risk of SBO. Certain MDCT features, such as the position of clustered SBL and hernial orifice, help distinguish between the four IH and may permit straightforward surgery.

Intracellular nanomanipulation by a photonic-force microscope with real-time acquisition of a 3D stiffness matrix.

A traditional photonic-force microscope (PFM) results in huge sets of data, which requires tedious numerical analysis. In this paper, we propose instead an analog signal processor to attain real-time capabilities while retaining the richness of the traditional PFM data. Our system is devoted to intracellular measurements and is fully interactive through the use of a haptic joystick. Using our specialized analog hardware along with a dedicated algorithm, we can extract the full 3D stiffness matrix of the optical trap in real time, including the off-diagonal cross-terms. Our system is also capable of simultaneously recording data for subsequent offline analysis. This allows us to check that a good correlation exists between the classical analysis of stiffness and our real-time measurements. We monitor the PFM beads using an optical microscope. The force-feedback mechanism of the haptic joystick helps us in interactively guiding the bead inside living cells and collecting information from its (possibly anisotropic) environment. The instantaneous stiffness measurements are also displayed in real time on a graphical user interface. The whole system has been built and is operational; here we present early results that confirm the consistency of the real-time measurements with offline computations.

Value of positron emission tomography in full-thickness chest wall resections for malignancies

Rapport de synthèse : Les tumeurs de la paroi thoracique sont des pathologies graves dont le traitement principal consiste en une résection chirurgicale. L'enjeu majeur de cette intervention ontologique est de réséquer la totalité de la tumeur, ce qui nécessite une planification préopératoire minutieuse. Classiquement, l'identification et la localisation de la tumeur se fait à l'aide de la tomodensitométrie (computed tomography, CT) ou de l'imagerie par résonnance magnétique (1RM). Actuellement, l'imagerie nucléaire fonctionnelle par tomographie par émission de positons (positron emission tomography, PET) qui peut être couplée au CT (PET/CT) est de plus en plus appliquée aux patients présentant une tumeur maligne. Son efficacité a fréquemment été démontrée. Le but de la présente étude est d'évaluer la valeur du PET dans la planification de la résection des tumeurs de la paroi thoracique. Une analyse rétrospective de dix-huit patients opérés entre 2004 et 2006 a été réalisée; Dans ce groupe de patient, la taille de la tumeur mesurée sur la pièce opératoire réséquée a été comparée à la taille de la tumeur mesurée sur le CT et le PET. Les résultats démontrent que le CT surestimait de manière consistante la taille réelle de la tumeur par rapport au PET (+64% par rapport à +1%, P<0.001). De plus, le PET s'est avéré particulièrement performant pour prédire la taille des tumeurs de plus de 5.5 cm de diamètre par rapport au CT (valeur prédictive positive 80% par rapport à 44% et spécificité 93% par apport à 64%, respectivement). Cette étude démontre que le PET permettrait de mesurer la taille des tumeurs de la paroi thoracique de manière plus précise que le CT. Cette nouvelle modalité diagnostique s'avèrerait donc utile pour planifier les résections chirurgicales de telles tumeurs. A notre connaissance, aucune publication ne décrit la valeur du PET dans ce domaine. Les performances accrues du PET permettraient une meilleure délimitation des tumeurs ce qui améliorerait la précision de la résection chirurgicale. En conclusion, cette étude préliminaire rétrospective démontre la faisabilité du PET pour les tumeurs de la paroi thoracique. Ces résultats devraient être confirmés par une étude prospective incluant un plus grand nombre de patients avec la perspective de juger l'impact clinique réel du PET sur la prise en charge thérapeutique des patients.

Diagnostic Performance of Magnetic Resonance Imaging and Computed Tomography for Advanced Retinoblastoma: A Systematic Review and Meta-analysis.

PURPOSE: To determine and compare the diagnostic performance of magnetic resonance imaging (MRI) and computed tomography (CT) for the diagnosis of tumor extent in advanced retinoblastoma, using histopathologic analysis as the reference standard. DESIGN: Systematic review and meta-analysis. PARTICIPANTS: Patients with advanced retinoblastoma who underwent MRI, CT, or both for the detection of tumor extent from published diagnostic accuracy studies. METHODS: Medline and Embase were searched for literature published through April 2013 assessing the diagnostic performance of MRI, CT, or both in detecting intraorbital and extraorbital tumor extension of retinoblastoma. Diagnostic accuracy data were extracted from included studies. Summary estimates were based on a random effects model. Intrastudy and interstudy heterogeneity were analyzed. MAIN OUTCOME MEASURES: Sensitivity and specificity of MRI and CT in detecting tumor extent. RESULTS: Data of the following tumor-extent parameters were extracted: anterior eye segment involvement and ciliary body, optic nerve, choroidal, and (extra)scleral invasion. Articles on MRI reported results of 591 eyes from 14 studies, and articles on CT yielded 257 eyes from 4 studies. The summary estimates with their 95% confidence intervals (CIs) of the diagnostic accuracy of conventional MRI at detecting postlaminar optic nerve, choroidal, and scleral invasion showed sensitivities of 59% (95% CI, 37%-78%), 74% (95% CI, 52%-88%), and 88% (95% CI, 20%-100%), respectively, and specificities of 94% (95% CI, 84%-98%), 72% (95% CI, 31%-94%), and 99% (95% CI, 86%-100%), respectively. Magnetic resonance imaging with a high (versus a low) image quality showed higher diagnostic accuracies for detection of prelaminar optic nerve and choroidal invasion, but these differences were not statistically significant. Studies reporting the diagnostic accuracy of CT did not provide enough data to perform any meta-analyses. CONCLUSIONS: Magnetic resonance imaging is an important diagnostic tool for the detection of local tumor extent in advanced retinoblastoma, although its diagnostic accuracy shows room for improvement, especially with regard to sensitivity. With only a few-mostly old-studies, there is very little evidence on the diagnostic accuracy of CT, and generally these studies show low diagnostic accuracy. Future studies assessing the role of MRI in clinical decision making in terms of prognostic value for advanced retinoblastoma are needed.

Increase of [(18)F]FLT tumor uptake in vivo mediated by FdUrd: toward improving cell proliferation positron emission tomography.

PURPOSE: 3'-deoxy-3'-[(18)F]fluorothymidine ([(18)F]FLT), a cell proliferation positron emission tomography (PET) tracer, has been shown in numerous tumors to be more specific than 2-deoxy-2-[(18)F]fluoro-D-glucose ([(18)F]FDG) but less sensitive. We studied the capacity of a nontoxic concentration of 5-fluoro-2'-deoxyuridine (FdUrd), a thymidine synthesis inhibitor, to increase uptake of [(18)F]FLT in tumor xenografts. METHODS: The duration of the FdUrd effect in vivo on tumor cell cycling and thymidine analogue uptake was studied by varying FdUrd pretreatment timing and holding constant the timing of subsequent flow cytometry and 5-[(125)I]iodo-2'-deoxyuridine biodistribution measurements. In [(18)F]FLT studies, FdUrd pretreatment was generally performed 1 h before radiotracer injection. [(18)F]FLT biodistributions were measured 1 to 3 h after radiotracer injection of mice grafted with five different human tumors and pretreated or not with FdUrd and compared with [(18)F]FDG tumor uptake. Using microPET, the dynamic distribution of [(18)F]FLT was followed for 1.5 h in FdUrd pretreated mice. High-field T2-weighted magnetic resonance imaging (MRI) and histology were used comparatively in assessing tumor viability and proliferation. RESULTS: FdUrd induced an immediate increase in tumor uptake of 5-[(125)I]iodo-2'-deoxyuridine, that vanished after 6 h, as also confirmed by flow cytometry. Biodistribution measurements showed that FdUrd pretreatment increased [(18)F]FLT uptake in all tumors by factors of 3.2 to 7.8 compared with controls, while [(18)F]FDG tumor uptake was about fourfold and sixfold lower in breast cancers and lymphoma. Dynamic PET in FdUrd pretreated mice showed that [(18)F]FLT uptake in all tumors increased steadily up to 1.5 h. MRI showed a well-vascularized homogenous lymphoma with high [(18)F]FLT uptake, while in breast cancer, a central necrosis shown by MRI was inactive in PET, consistent with the histomorphological analysis. CONCLUSION: We showed a reliable and significant uptake increase of [(18)F]FLT in different tumor xenografts after low-dose FdUrd pretreatment. These results show promise for a clinical application of FdUrd aimed at increasing the sensitivity of [(18)F]FLT PET.

Optimisation des doses en tomographie computérisée pédiatrique [Patient dose optimization in pediatric computerized tomography]

The development of CT applications might become a public health problem if no effort is made on the justification and the optimisation of the examinations. This paper presents some hints to assure that the risk-benefit compromise remains in favour of the patient, especially when one deals with the examinations of young patients. In this context a particular attention has to be made on the justification of the examination. When performing the acquisition one needs to optimise the extension of the volume investigated together with the number of acquisition sequences used. Finally, the use of automatic exposure systems, now available on all the units, and the use of the Diagnostic Reference Levels (DRL) should allow help radiologists to control the exposure of their patients.