Test-retest reproducibility of 18F-MPPF PET in healthy humans: a reliability study.

The aim of this study was to assess the reliability of 2'-methoxyphenyl-(N-2'-pyridinyl)-p-18F-fluoro-benzamidoethylpiperazine (18F-MPPF) PET binding parameter's quantification via a test-retest study over a long-term period. METHODS: Ten healthy volunteers underwent 2 dynamic 18F-MPPF PET scans in an interval of 6 mo. As a methodologic control, 10 simulated datasets, including interindividual functional and anatomic variabilities, were also used to assess the measurement variations in the absence of intraindividual variability. Indices of tracer binding were computed using 2 different models: (a) the simplified reference tissue model (SRTM) and (b) the Logan graphical model. The SRTM allows computing the binding potential (BP) index and plasma-to-brain transport constants (R1, k2). The Logan model evaluates the distribution volume (DV). For both methods, cerebellum was taken as the reference region. From both models, binding indices were calculated with time-activity curves extracted from regions of interest, on one hand, and for each voxel to perform parametric images on the other hand. RESULTS: Reliability indices--that is, bias, variability, and intraclass correlation (ICC)--indicated a good reproducibility: the BP percentage change in mean between test and retest is close to 1% in rich regions and 2% in poor regions. The typical error is around 7%. Mean ICC is over 0.70. The DV percentage change in the mean is +/-2.5%, with a typical error close to 6% and an ICC over 0.60. CONCLUSION: Our results show a good reliability, with a reasonable level of intraindividual biologic variability that allows crossover studies with 18F-MPPF in which small percentage changes are expected between test and retest measurements, in group studies and for single subject assessment.     

A 18F-MPPF PET normative database of 5-HT1A receptor binding in men and women over aging.

Neurotransmission imaging studies require normative data for the statistical assessment of neurophysiologic dysfunctions. 2'-Methoxyphenyl-(N-2'-pyridinyl)-p-18F-fluoro-benzamidoethylpiperazine (18F-MPPF) is a specific serotonin 5-HT1A antagonist PET tracer recently characterized, modeled, and used for clinical research to explore abnormalities in the serotoninergic system. Our study reports, to our knowledge, the first large normative imaging database of 18F-MPPF binding potential (BP) over aging, for both males and females. METHODS: Fifty-three healthy volunteers (27 females, 26 males; age, 20-70 y) were selected to undergo structural MRI and single-injection 18F-MPPF multiframe dynamic PET. 18F-MPPF BP values were computed using a nonlinear modeling method with tissue reference. The statistical assessment of the effect of age and sex was performed both at the anatomic structure level, using regions of interest drawn manually on individual MR images, and at the voxel level, using normalized BP parametric images in different statistical parametric mapping designs. RESULTS: A negative linear correlation between age and 18F-MPPF binding (3.6% decrease by decade) was found in females but not in males and involved most of the limbic and paralimbic regions; on the other hand, males in their 30s showed decreased binding in most cerebral regions. CONCLUSION: A comparison of males and females revealed higher BP values independent of age in females in the right hemisphere and a different evolution of BP over aging. These results confirm the necessity of a database for further statistical analysis in individuals or groups with pathology.     

Rheological Changes After Stenting of a Cerebral Aneurysm: A Finite Element Modeling Approach

Hemodynamic changes in intracranial aneurysms after stent placement include the appearance of areas with stagnant flow and low shear rates. We investigated the influence of stent placement on blood flow velocity and wall shear stress of an intracranial aneurysm using a finite element modeling approach. To assess viscosity changes induced by stent placement, the rheology of blood as non-Newtonian fluid was taken into account in this model. A two-dimensional model with a parent artery, a smaller branching artery, and an aneurysm located at the bifurcation, before and after stent placement, was used for simulation. Flow velocity plots and wall shear stress before and after stent placement was calculated over the entire cardiac circle. Values for dynamic viscosity were calculated with a constitutive equation that was based on experimental studies and yielded a viscosity, which decreases as the shear rate increases. Stent placement lowered peak velocities in the main vortex of the aneurysm by a factor of at least 4 compared to peak velocities in the main artery, and it considerably decreased the wall shear stress of the aneurysm. Dynamic viscosity increases after stent placement persisted over a major part of the cardiac cycle, with a factor of up to 10, most pronounced near the dome of the aneurysm. Finite element modeling can offer insight into rheological changes induced by stent treatment of aneurysms and allows visualizing dynamic viscosity changes induced by stent placement.     

Comparison of functional MR imaging guidance to electrical cortical mapping for targeting selective motor cortex areas in neuropathic pain: a study based on intraoperative stereotactic navigation

PURPOSE: To assess the concordance between data from functional MR imaging (fMRI) guidance and the intraoperative electrical cortical mapping (iCM) in targeting selective motor cortex areas in refractory neuropathic pain. METHODS: Twenty-one patients (11 women and 10 men; mean age, 55.6 years) with refractory central (ischemic, 8 cases) and neuropathic pain (trigeminal neuropathy, 6 cases; syrinx/amputation/plexus trauma, 7 cases) underwent surgery for the implantation of an epidural electrode for chronic motor cortex stimulation (MCS) with general anesthesia and a frameless neuronavigation system used for the image-guided targeting procedure. All patients were studied by preoperative fMRI and epidural iCM with somatosensory evoked potentials and motor cortex stimulodetection. fMRI investigated systematically motor tasks of both hands and that related to the somatic area (foot or tongue) affected by pain. fMRI data were analyzed with the Statistical Parametric Mapping99 software (initial analysis threshold [AT] corresponding to P < .001), registered in the neuronavigation system and correlated intraoperatively with iCM. Matching of fMRI and iCM was specifically examined, focusing the study on hand mapping. RESULTS: Concordance between contours of fMRI activation area and iCM in precentral gyrus (mean distance, 3.8 mm) was found in 20/21 patients (95%). Because precision of iCM was suboptimal in 7 patients, concordance for more restrictive values of the AT (P < .0001) was found in only 13 of these 20 patients. Concordance was not found in one patient, as result of image distortion and residual motion artifact. CONCLUSIONS: In this study, fMRI guidance provides information that matches those of an independent functional method. These data illustrate the functional accuracy of fMRI guidance for the operative targeting of selective motor cortex areas in neuropathic pain.     

Colocolic tumoral intussusception in the adult: value of multi-slice spiral CT imaging

Colocolic intussusception in the adult, caused by a tumoral process, is a rare clinical event.

We have studied two adults clinically presenting with a mass in the right iliac fossa, which was produced in one case by a carcinoma involving the right colon and in the other case involving the sigmoid.

Multi-slice spiral CT imaging showed the presence of a colocolic intussusception—the tumoral characteristics of the lesion eliminated the possibility of a lipoma—and it allowed a satisfactory presurgical evaluation of the pathological process.     

Aortic embolism of cement: a rare complication of lumbar percutaneous vertebroplasty

An aortic embolus of cement occurred in a 72-year-old woman after lumbar percutaneous vertebroplasty for breast cancer metastasis. A CT scan during the procedure revealed cement migration into the aorta via the lumbar artery. The cement embolus in the aorta, along with the hook-shaped cement fragment in the lumbar artery, was asymptomatic. Thereafter, a CT scan 4 months later still showed the presence of cement in the aorta and the lumbar artery at the level of the vertebroplasty. The patient is free of complaints after 4 months without anticoagulant treatment. This rare complication occurred because the collateral arterial supplies to the breast metastasis and the retrograde migration of cement during the vertebroplasty were not recognized. Proper techniques can minimize the risk of arterial embolism caused by cement during the procedure.     

Thoracolumbar spine fractures in patients who have sustained severe trauma: depiction with multi-detector row CT

PURPOSE: To determine if multi-detector row computed tomography (CT) can replace conventional radiography and be performed alone in severe trauma patients for the depiction of thoracolumbar spine fractures. MATERIALS AND METHODS: One hundred consecutive severe trauma patients who underwent conventional radiography of the thoracolumbar spine as well as thoracoabdominal multi-detector row CT were prospectively identified. Conventional radiographs were reviewed independently by three radiologists and two orthopedic surgeons; CT images were reviewed by three radiologists. Reviewers were blinded both to one another's reviews and to the results of initial evaluation. Presence, location, and stability of fractures, as well as quality of reviewed images, were assessed. Statistical analysis was performed to determine sensitivity and interobserver agreement for each procedure, with results of clinical and radiologic follow-up as the standard of reference. The time to perform each examination and the radiation dose involved were evaluated. A resource cost analysis was performed. RESULTS: Sixty-seven fractured vertebrae were diagnosed in 26 patients. Twelve patients had unstable spine fractures. Mean sensitivity and interobserver agreement, respectively, for detection of unstable fractures were 97.2% and 0.951 for multi-detector row CT and 33.3% and 0.368 for conventional radiography. The median times to perform a conventional radiographic and a multi-detector row CT examination, respectively, were 33 and 40 minutes. Effective radiation doses at conventional radiography of the spine and thoracoabdominal multi-detector row CT, respectively, were 6.36 mSv and 19.42 mSv. Multi-detector row CT enabled identification of 146 associated traumatic lesions. The costs of conventional radiography and multi-detector row CT, respectively, were 145 and 880 US dollars per patient. CONCLUSION: Multi-detector row CT is a better examination for depicting spine fractures than conventional radiography. It can replace conventional radiography and be performed alone in patients who have sustained severe trauma.     

Use of <Superscript>123</Superscript>I-MIBG scintigraphy to assess the impact of carvedilol on cardiac adrenergic neuronal function in childhood dilated cardiomyopathy

Iodine-123 metaiodobenzylguanidine (MIBG) cardiac scintigraphy is a useful tool for the assessment of cardiac adrenergic neuronal function, which is impaired in children with idiopathic dilated cardiomyopathy (DCM). In adults with DCM, long-term treatment with carvedilol improves both cardiac adrenergic neuronal function and left ventricular function. The aim of this prospective study was to evaluate the impact of carvedilol on cardiac adrenergic neuronal function using ¹²³I-MIBG scintigraphy and on left ventricular function using equilibrium radionuclide angiography in children with DCM. Seventeen patients (11 female, six male; mean age 39±57 months, range 1–168 months) with DCM and left ventricular dysfunction underwent ¹²³I-MIBG cardiac scintigraphy and equilibrium radionuclide angiography before and after a 6-month period of carvedilol therapy. A static anterior view of the chest was acquired 4 h after intravenous injection of 20–75 MBq of ¹²³I-MIBG. Cardiac neuronal uptake of ¹²³I-MIBG was measured using the heart to mediastinum count ratio (HMR). Radionuclide left ventricular ejection fraction (LVEF) was assessed following a standard protocol. MIBG cardiac uptake and left ventricular function respectively increased by 38% and 65% after 6 months of treatment with carvedilol (HMR=223%±49% vs 162%±26%, P<0.0001, and LVEF=43%±17% vs 26%±11%, P<0.0001). Carvedilol can improve cardiac adrenergic neuronal and left ventricular function in children with dilated cardiomyopathy. Further studies are needed to assess the relationship between improvement in MIBG cardiac uptake and the beneficial effects of carvedilol on morbidity and mortality.     

Gadobutrol-enhanced moving-table magnetic resonance angiography in patients with peripheral vascular disease: a prospective,multi-centre blinded comparison with digital subtraction angiography

The purpose of this study was to compare moving-table three-dimensional contrast-enhanced magnetic resonance angiography (CE MRA), using 1.0-mol gadobutrol, with intra-arterial digital subtraction angiography (i.a. DSA) for evaluation of pelvic and peripheral arteries in patients with peripheral arterial occlusive disease. A total of 203 patients were examined in a prospective, multi-centre study at 1.0/1.5 T. Ten vessel segments of one leg were evaluated on-site and by three independent blinded reviewers off-site. One hundred eighty-two patients were evaluable in blinded reading. For pelvis and thigh, there was statistically significant diagnostic agreement between CE MRA and i.a. DSA on-site (94%) and off-site (86-88%). Overall, for detection of clinically significant stenoses, 93% sensitivity and 90% specificity were achieved in on-site evaluation, with 71-76 and 87-93% off-site; for detection of occlusion, sensitivity and specificity on-site were 91 and 97%, with 75-82 and 94-98% off-site. Evaluation was more sensitive on-site than off-site for detection of stenoses and occlusion, whereas specificity was similar. The CE MRA with 1.0-mol gadobutrol gave results comparable to those of i.a. DSA for the larger arteries of pelvis and thigh. Results for calf arteries were compromised by spatial resolution and technical limitations.