Value of (18)F-FDG-PET/CT in patients with fever of unknown origin and unexplained prolonged inflammatory syndrome: a single centre analysis experience.

OBJECTIVE: The aim of our study was to evaluate the diagnostic contribution of (18)F-fluoro-deoxyglucose ((18)F-FDG)-positron emission tomography (PET)/computed tomography (CT) in patients with fever of unknown origin (FUO) or unexplained prolonged inflammatory syndrome (UPIS) in real life. PATIENTS AND METHODS: We performed a retrospective study including 14 patients with FUO or UPIS hospitalised in our institution (Strasbourg University Hospital, France) between January 2005 and July 2006. (18)F-FDG-PET/CT was considered helpful when abnormal results allowed an accurate diagnosis. RESULTS: (18)F-FDG-PET/CT was helpful in half the patients (7/14) for final diagnosis. A diagnosis was reached in 87.5% of the patients (7/8) with an abnormal (18)F-FDG-PET/CT but only in 50% of the patients (3/6) with a normal (18)F-FDG-PET/CT. Conventional chest and abdominal CT was performed in 13 patients before ordering (18)F-FDG-PET/CT. We considered that (18)F-FDG-PET/CT was essential to establish the final diagnosis in only 23% of the patients (3/13) since neither chest nor abdominal CT identified abnormalities consistent with the final diagnosis. However, among the three patients, two were diagnosed with large vessel vasculitis and one patient with local prosthetic infection. CONCLUSIONS: Our study supports the potential interest of (18)F-FDG-PET/CT in the diagnostic workup of FUO and UPIS as it helped establish a fine diagnosis in half of the cases. However, (18)F-FDG-PET/CT appeared to be essential to the final diagnosis in only 23% of the cases. In our opinion, this protocol should be performed as a second level test, especially when conventional CT is normal or is unable to discriminate between active and silent lesions.

Dedicated low-field MRI in mice.

The rationale of this work is to point out the relevance of in vivo MR images of mice obtained using a dedicated low-field system. For this purpose a small 0.1 T water-cooled electro-magnet and solenoidal radio frequency (RF) transmit-receive coils were used. All MR images were acquired in three-dimensional (3D) mode. An isolation cell was designed allowing easy placement of the RF coils and simple delivery of gaseous anesthesia as well as warming of the animal. Images with and without contrast agent were obtained in total acquisition times on the order of half an hour to four hours on normal mice as well as on animals bearing tumors. Typical in plane pixel dimensions range from 200 x 200 to 500 x 500 microm(2) with slice thicknesses ranging between 0.65 and 1.50 mm. This work shows that, besides light installation and low cost, dedicated low-field MR systems are suitable for small rodents imaging, opening this technique even to small research units.

[Value of left atrial dilation in the diagnosis of silent myocardial ischemia in diabetes mellitus patients]. / Facteurs prédictifs de l'existence d'une ischémie myocardique silencieuse chez le patient diabétique. Intérêt de l'évaluation de la surface de l'oreillette gauche.

BACKGROUND: Accelerated atherothrombosis is a common feature in diabetes mellitus patients (DM), which can be related to abnormalities in vascular cell apoptosis and activation leading to the release of procoagulant microparticles (MPs). In DM patients, we hypothesized that circulating levels of biomarkers involved in atherothrombosis processes as well as cardiac and carotid echocardiography variables could be useful in the detection of silent myocardial diagnosed by myocardial perfusion imaging. METHODS AND RESULTS: We investigated, in 55 patients with diabetes (mean age 62+/-10 years) and 15 nondiabetics (46+/-14 years) patients the prevalence of silent myocardial ischemia (SMI) detected by a treadmill exercise or dipyridamole (99m)Tc-sestamibi stress test. Echocardiographic and -carotid variables were obtained using standardized methods. Biomarkers assessing endothelial apoptosis or activation (CD31+-MPs, CD62+-MPs, VCAM-1), inflammatory status (CD11a +/- MPs, MCP-1, CRP), platelet activation (GPIb+/-MPs, CD40-L, P-selectin, GPV) ventricular stretch (BNP) were measured in the plasma. SMI was diagnosed in 23/55 (42%) diabetics patients and in 3/15 (20%) nondiabetics patients. Enhanced inflammatory status and leukocyte damage (CD11a+-MPs) were evidenced in diabetic patients. Within the diabetic population, biomarkers levels of atherothrombosis were not significantly associated to the detection of SMI. In multivariable analyses adjusted for LV hypertophy, left atrial surface (LA) remained independent predictor of silent myocardial ischemia (OR 4.14; IC [1.7-16.13]; P=0.039). CONCLUSIONS: In diabetes mellitus patients, LA surface independently predicted silent myocardial ischemia after adjustment for established echocardiographic, and inflammatory risk factors. This simple measure of LA dilation could be helpful in the identification of diabetes mellitus patients at heightened cardiovascular risk.

Fiber tracking in q-ball fields using regularized particle trajectories.

Most of the approaches dedicated to fiber tracking from diffusion-weighted MR data rely on a tensor model. However, the tensor model can only resolve a single fiber orientation within each imaging voxel. New emerging approaches have been proposed to obtain a better representation of the diffusion process occurring in fiber crossing. In this paper, we adapt a tracking algorithm to the q-ball representation, which results from a spherical Radon transform of high angular resolution data. This algorithm is based on a Monte-Carlo strategy, using regularized particle trajectories to sample the white matter geometry. The method is validated using a phantom of bundle crossing made up of haemodialysis fibers. The method is also applied to the detection of the auditory tract in three human subjects.

Potential applications of laser polarised xenon for CBF measurements by NMR.

Laser polarised (hyperpolarised) 129Xe offers a new potential way for assessment of cerebral blood flow (CBF) by nuclear magnetic resonance (NMR). We present the basic physical principles underlying noble gases'laser polarisation. Distinguishing characteristics of 129Xe NMR properties as well as theoretical basis for CBF measurement using laser polarised 129Xe are emphasized. Recent results are briefly presented and potential applications as well as current limitations of 129Xe in CBF studies are discussed.

Evaluation of the use of six diagnostic X-ray spectra computer codes.

A knowledge of photon energy spectra emitted from X-ray tubes in radiology is crucial for many research domains in the medical field. Since spectrometry is difficult because of high photon fluence rates, a convenient solution is to use computational models. This paper describes the use of six computer codes based on semiempirical or empirical models. The use of the codes was assessed, notably by comparing theoretical half value layers and air kerma with measurements on five different X-ray tubes used in a research hospital. It was found that three out of the six computer codes give relative spectra very close to those produced by X-ray units equipped with constant potential generators: the mean difference between measured and modelled half value layer was less than 3% with a standard deviation of 3.6% whatever the tube and the applied voltage. Absolute output is less accurate: for four computer codes, the mean difference between the measured and modelled air kerma was between 18% and 36%, with a standard deviation of 9% whatever the tube (except for the single phase generator) and the applied voltage. One of the codes gives a good output and beam quality for X-ray units equipped with 100% ripple voltage generators. The use of computational codes as described in this paper provides a means of modelling relative diagnostic X-ray spectra, the usefulness of the tube output data depending on the accuracy required by the end user.

Feasibility of a semiconductor dosimeter to monitor skin dose in interventional radiology.

The design and preliminary test results of a semiconductor silicon dosimeter are presented in this article. Use of this dosimeter is foreseen for real-time skin dose control in interventional radiology. The strong energy dependence of this kind of radiation detector is well overcome by filtering the silicon diode. Here, the optimal filter features have been calculated by numerical Monte Carlo simulations. A prototype has been built and tested in a radiological facility. The first experimental results show a good match between the filtered semiconductor diode response and an ionization chamber response, within 2% fluctuation in a 2.2 to 4.1 mm Al half-value layer (HVL) energy range. Moreover, the semiconductor sensor response is linear from 0.02 Gy/min to at least 6.5 Gy/min, covering the whole dose rate range found in interventional radiology. The results show that a semiconductor dosimeter could be used to monitor skin dose during the majority of procedures using x-rays below 150 keV. The use of this device may assist in avoiding radiation-induced skin injuries and lower radiation levels during interventional procedures.

Xenon-129 MR imaging and spectroscopy of rat brain using arterial delivery of hyperpolarized xenon in a lipid emulsion.

Hyperpolarized (129)Xe dissolved in a lipid emulsion constitutes an NMR tracer that can be injected into the blood stream, enabling blood-flow measurement and perfusion imaging. A small volume (0.15 ml) of this tracer was injected in 1.5 s in rat carotid and (129)Xe MR spectra and images were acquired at 2.35 T to evaluate the potential of this approach for cerebral studies. Xenon spectra consistently showed two resonances, at 194.5 ppm and 199.0 ppm relative to the gas peak. The signal-to-noise ratio (SNR) obtained for the two peaks was sufficient (ranging from 12 to 90) to follow their time courses. 2D transverse-projection xenon images were obtained with an in-plane resolution of 900 microm per pixel (SNR range 8-15). Histological analysis revealed no brain damage except in two rats that had received three injections.

Myocardial flow reserve parametric map, assessed by first-pass MRI compartmental analysis at the chronic stage of infarction.

Regional myocardial flow and flow reserve (MFR) were assessed by compartmental analysis of Gd-enhanced MRI first-pass data in 7 patients with atypical chest pain, and in 15 patients with previous transmural myocardial infarction. The FE product (Flow x Extraction coefficient), derived from the modified Kety equation, was measured in regions corresponding to the Tetrofosmine-SPECT fixed defect and in remote normal regions. The FE product at rest and hyperemic FE product were similar in healed revascularized tissues (70.5 +/- 15.6 and 112.5 +/- 19.5 ml/mn/100 g, respectively) and in normal myocardium (76.2 +/- 18.3 and 142.2 +/- 33.0, respectively). In contrast, the FE index (48.8 +/- 15.2 and 60.7 +/- 18.0, respectively, P < 0.01 versus the two previous groups) and the MFR (1.27 +/- 0.20 vs. 1.91 +/- 0.29 in normal regions) were reduced in healed fibrotic tissues when the infarct-related artery remained occluded. Myocardial flow reserve maps allowed correct identification of regions corresponding to an occluded infarct-related artery.

[Anemia caused by vitamin B 12 deficiency in subjects aged over 75 years: new hypotheses. A study of 20 cases]. / Anémies par carence en vitamine B12 chez le sujet âgé de plus de 75 ans: nouveaux concepts. A propos de 20 observations.

PURPOSE: New hypotheses have recently been developed on vitamin B12 deficiency and the frequently observed occurrence in the elderly subject of food cobalamin malabsorption, i.e., the non-dissociation of B12 and its carrier protein (ND B12), and the possibility of rectifying this imbalance by oral crystalline B12 supplementation. The aim of this study was therefore to confirm these hypotheses in a series of patients aged over 75 years with anemia due to B12 deficiency. METHODS: A retrospective study was carried out over a 5-year period on patients aged over 75 years presenting with megaloblastic anemia (hemoglobin [Hb] < 12 g/dL) and vitamin B12/cobalamin deficiency (B12 < 160 pg/mL). RESULTS: Twenty cases were analyzed. The average age of the patient population was 82.5 +/- 6 years, and the F/M sex ratio was 1:2. Mean Hb levels were 7.9 +/- 2.4 g/dL, mean serum B12 levels were 83 +/- 24 pg/mL, and mean homocysteinemic levels were 35 +/- 27 mumol/L. The diagnosis was as follows: food cobalamin malabsorption/ND B12 (n = 10), Biermer's disease/pernicious anemia (n = 5), malabsorption due to pancreatic insufficiency (n = 1), and low dietary B12 levels (n = 1). Disorders associated with ND B12 were: atrophic gastritis and Helicobacter pylori infection (n = 6), antacid or biguanide intake (n = 3), alcohol abuse (n = 2), or idiopathic syndrome (n = 2). In the patients who were followed up (n = 10), i.m. (n = 5) or oral (n = 5) administration of crystalline B12 resulted in the correction of hematological abnormalities. CONCLUSION: In the elderly subject, food cobalamin/ND B12 malabsorption appears to be the main cause of B12 deficiency, and is frequently associated with atrophic gastritis. In these cases, administration of oral crystalline B12 may be an efficient means of treating this disorder.

In vivo 129Xe NMR in rat brain during intra-arterial injection of hyperpolarized 129Xe dissolved in a lipid emulsion.

Hyperpolarized 129Xe was dissolved in a lipid emulsion and administered to anaesthetized rats by manual injections into the carotid (approximately 1-1.5 mL in a maximum time of 30 s). During injection, 129Xe NMR brain spectra at 2.35 T were recorded over 51 s, with a repetition time of 253 ms. Two peaks assigned to dissolved 129Xe were observed (the larger at 194 +/- 1 ppm assigned to intravascular xenon and the smaller at 199 +/- 1 ppm to xenon dissolved in the brain tissue). Their kinetics revealed a rapid intensity increase, followed by a plateau (approximately 15 s duration) and then a decrease over 5 s. This behaviour was attributed to combined influences of the T1 relaxation of the tracer, of radiofrequency sampling, and of the tracer perfusion rate in rat brain. Similar kinetics were observed in experiments carried out on a simple micro-vessel phantom. An identical experimental set-up was used to acquire a series of 2D projection 129Xe images on the phantom and the rat brain.

[Cartography of absolute myocardial perfusion with magnetic resonance imaging. Methods and results]. / Cartographie de la perfusion myocardique absolue avec imagerie par résonance magnétique. Méthodes et résultats.

Ultra-rapid dynamic MRI (one image per heart beat) can follow the progression of the intra-myocardial signal during the first passage of diffusable gadolinium chelates injected as a bolus through a peripheral vein. A quantitative evaluation of myocardial perfusion is possible using a compartmental model of analysis. Absolute myocardial flow can be measured at rest and during hyperaemia induced by dipyridamole. It is possible to associate functional mapping, corresponding to parametric images of the flow indices, to the global evaluation. The ratio between the values obtained during hyperaemia and under basal conditions correspond to the myocardial reserve. The principles, results and limitations of this method are discussed in the light of published results, underlining the advantages of absolute flow measurement and of the differences between the results of MRI and myocardial scintigraphy.

[Subareolar injection of 99m-Tc sulfur colloid for sentinel nodes identification in multifocal invasive breast cancer]. / Injection sous-aréolaire de sulfocolloïdes technétiés pour l'identification des ganglions sentinelles dans les cancers du sein invasifs à foyers multiples.

The objective were to study the relevance of the subareolar injection for sentinel node [SN] detection in multiple foci breast cancer. Seventy-nine patients with infiltrative breast carcinoma (diagnosed pre-operatively by core biopsy) and a mean age of 55 (31-78) years were enrolled. All patients were free of previous homolateral surgery, chemotherapy, locoregional radiotherapy or prevalent axillary lymph node. Using four 0.1 ml injections of 1.8 MBq, the technetium-99m 100 nm filtered sulfur colloid was injected by subareolar way (group I) in 16 cases of radiologically cancer with multiple invasive foci and 31 cases of radiologically unifocal cancer, and by peritumoral way (group II) in 32 cases of radiologically unifocal cancer. Scintigrams were obtained 2 to 4 hours after the injections and radioactive nodes were detected peroperatively 18 hours after the injection by intraoperative detection probe. Individual removal of all radioactive nodes was followed by axillary dissection at levels I and II of Berg including Rotter area control. All sentinel nodes were submitted to standard histopathological analysis on serial sections at 500 mu intervals completed by immunohistochemistry for cytokeratin on negative SN. SN were detected by scintigrams in 85% and 88% of the cases of group I and group II respectively, but in 98% and 97% of the cases of respectively both groups by intraoperative probe. Group I was composed of 69% ductal, 22% lobular and 9% tubular carcinomas, and group II of 87% ductal, 10% lobular and 3% tubular carcinomas. Seven and 5 radiologically unifocal tumors were in fact with multiple invasive foci at histology in groups I and II respectively. The complete scintigraphic procedure permitted the detection of a mean number of 2.7 (1-7) SN in group I and 2.3 (1-4) in group II (NS). In group I, the SN were metastatic in 22 patients (48%), 15 of them with the metastases being restricted to the SN, whereas in group II, the SN were metastatic in 9 patients (28%), 5 of them with the positivity restricted to the SN. No false negative result (SN negative and other axillary nodes positive) was observed in group I and only one false negative result in group II which was related to a cancer with histological multiple invasive foci. Sensitivities were 100% and 90%, and negative predictive values were 100% and 95%, for groups I and II respectively. Subareolar injection of radiocolloid allows identification of SN in cases of unifocal and multiple cancer. The mean number of SN detected by the subareolar method is not significantly different, although higher, to that detected by peritumoral injection.

Ex vivo high resolution MR imaging of the human lip with a dedicated low field system.

Histological correlations of the human lip with corresponding magnetic resonance (MR) images obtained ex vivo are presented. MR images were acquired with a dedicated low-field (0.1 T) MR system, with a resolution of 100 x 100 micron2 and a slice thickness of 1 mm using 3D-FLASH sequences. The outermost tissues visible on images are of high signal intensity, while the innermost connective tissues are of low signal intensity, both for skin and oral mucosa. It is possible to use a low-field system to obtain high resolution images of small biological samples.

Low-field dedicated magnetic resonance imaging: a potential tool for assisting perinatal autopsy.

Although the practice of perinatal autopsy has increased in recent years, examination of the fetus and especially of the fetal brain during the first trimester or the beginning of the second trimester remains difficult. Postmortem high-resolution images of the brain of a normal and an abnormal fetus of the same gestational age (22 weeks) were obtained with a low-field (0.1 T) dedicated magnetic resonance imaging (MRI) system. We demonstrated that a small MRI machine supplemented data from classical necropsy and may help in the interpretation of in utero ultrasound and magnetic resonance images for the antenatal diagnosis of fetal malformations.