The aim of this study was to demonstrate the potential of a wireless pixelated β+-sensitive intracerebral probe (PIXSIC) for in vivo positron emission tomographic (PET) radiopharmacology in awake and ...freely moving rodents. The binding of 11Craclopride to D2 dopamine receptors was measured in anesthetized and awake rats following injection of the radiotracer. Competitive binding was assessed with a cold raclopride injection 20 minutes later. The device can accurately monitor binding of PET ligands in freely moving rodents with a high spatiotemporal resolution. Reproducible time-activity curves were obtained for pixels throughout the striatum and cerebellum. A significantly lower 11Craclopride tracer-specific binding was observed in awake animals. These first results pave the way for PET tracer pharmacokinetics measurements in freely moving rodents.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Presents a computerized method for automated detection of the boundary of the os calcis on in vivo ultrasound parametric images, using an active dynamic contour model. The initial contour, defined ...without user interaction, is an iso-contour extracted from the textural feature space. The contour is deformed through the action of internal and external forces, until stability is reached. The external forces, which characterize image features, are a combination of gray-level information and second-order textural features arising from local cooccurrence matrices. The broadband ultrasound attenuation (BUA) value is then averaged within the contour obtained. The method was applied to 381 clinical images. The contour was correctly detected in the great majority of the cases. For the short-term reproducibility study, the mean coefficient of variation was equal to 1.81% for BUA values and 4.95% for areas in the detected region. Women with osteoporosis had a lower BUA than age-matched controls (p=0.0005). In healthy women, the age-related decline was -0.45 dB/MHz/yr. In the group of healthy post-menopausal women, years since menopause, weight and age were significant predictors of BUA. These results are comparable to those obtained when averaging BUA values in a small region of interest.
The aim of this study was to compare the effectiveness of a hand-held preoperative compact imager (POCI) camera with conventional lymphoscintigraphy using a γ-camera for sentinel lymph node (SLN) ...detection in breast cancer.
The main objective was to demonstrate the noninferiority of the POCI relative to conventional lymphoscintigraphy and to compare the number of SLNs detected by the 2 imaging devices. Our study, a clinical prospective, double-blind, noninferiority study, planned to include 200 patients with early breast cancer and started in January 2006. A standard SLN protocol (4 periareolar injections of 37 MBq of (99m)Tc-nanocolloids, 2 h before lymphoscintigraphy) was performed preoperatively using a conventional γ-camera and then the POCI camera. Scans were obtained by 2 different nuclear medicine physicians unaware of each other's results. The day after, in the operating room, the surgeon, after receiving the previous results, used the counting probe for surgical SLN biopsy. The number and localization of axillary SLNs obtained by lymphoscintigraphy and the POCI and the duration of the whole procedure were determined.
Among the 162 patients included, 138 were evaluable. The POCI detected more SLNs than did lymphoscintigraphy in 50 patients (36%), the same number of in 54 patients (39%), and fewer SLNs in 34 patients (25%), representing 84 (61%) discordant pairs. The noninferiority of preoperative compact imaging of axillary SLNs numbers was found to be statistically significant (95% confidence interval, 30%-52%, P = 0.025) using the McNemar test. The duration of acquisition was shorter using the POCI (<10 min in 84% n = 117 of patients; mean, 7.5 ± 3.3 min) than lymphoscintigraphy (13% n = 18 of patients; mean, 15.7 ± 3.4 min), with P < 0.001 using the McNemar test for paired proportions.
Preoperative compact imaging using a hand-held camera was able to predict the number and localization of breast cancer SLNs and was not inferior to conventional lymphoscintigraphy in this study. Further studies will determine whether preoperative compact imaging could replace lymphoscintigraphy, especially in surgical centers without an on-site nuclear medicine department.
This paper presents a computerized method for the automated segmentation of individual microcalcifications in a region of interest (ROI) known to contain a cluster in digital mammograms. Mammographic ...parenchyma caj be accurately modeled with the fractal approach, but not areas with microcalcifications. The digitized image is divided into 16 x 16-pixel overlapping windows and those accurately modeled by the fractal model are eliminated. The next steps include local thresholding of the ROIs using an iterative method, the elimination of some of the artifacts and identification of the clustered microcalcifications using a clustering algorithm. The evaluation was performed on 81 simulated clusters superimposed on normal mammographic backgrounds and on a representative database of 408 real mammograms. Microcalcification locations were identified by two radiologists independently. These locations were compared to those found by the computer algorithm. An average of 59% of the simulated microcalcifications and 69% of the microcalcifications common to both radiologists were detected. The algorithm described provides a fully automated method for the segmentation of individual microcalcifications in an area of the mammogram known to contain a cluster.
For absorptiometry measurements, soft tissue may have an impact on quantitative ultrasound (QUS) measurements. In the present study, we focused primarily on the quantification of measurement error on ...speed of sound (SOS) caused by surrounding soft tissue. The relevant soft tissue parameters affecting the inherent SOS inaccuracies are thickness and sound velocity. To meet our goal, SOS measurements were taken at the right heel using a QUS imaging device in 21 healthy subjects. Site-matched measurements of soft tissue thickness (STT) and bone width were performed using magnetic resonance imaging of the heel. Several bone velocities were calculated either by accounting for bone width (SOSBW) only or by taking into account the exact path lengths of all major components traversed by ultrasound V(b)). Given that soft tissue composition is difficult to determine in vivo, we chose to estimate lower and upper error bounds on bone velocity (V(b lower) and V(b upper)) by spanning the full range of available values in the literature. The mean BW was 30.7 +/- 2.7 mm and the mean medial and external STTs were 8.8 +/- 1.7 and 8.5 +/- 1.5 mm, respectively. Accounting for true BW only resulted in no significant difference between SOS (1533 +/- 37) and SOSBW (1531 +/- 33). By contrast, accounting for both true BW and surrounding soft tissue resulted in an increase in the calculated bone velocity and statistically significant differences between SOS and V(b upper) (1568 +/- 36) and V(b lower) (1542 +/- 34). Root mean square errors between SOS and the calculated velocities were 0.34, 2. 32, and 0.70% for SOSBW, V(b upper), and V(b lower), respectively. We report here measurement errors caused by soft tissue to be 3 to 20 times higher than the SOS short-term precision (SOS coefficient of variation of 0.1%). Our results suggest that inaccuracies in SOS measurement caused by overlying soft tissue cannot be neglected. Overlying soft tissues may influence outcomes of longitudinal studies, especially if variations in tissue thickness and composition occur during the longitudinal follow-up. A practical way of minimizing the measurement error could be to perform an adequate correction for the overlying soft tissue. However, ideally, this should require knowing both the thickness and sound velocity in soft tissue. One might preferably conduct experimental investigations that directly control soft tissue thickness and composition to resolve this problem.
Three-dimensional (3D) high-resolution ultrasonography has proved to be useful for
in vitro assessment of cartilage remodeling due to osteoarthritis. The diagnosis is performed by computation of the ...mean thickness of the cartilage, which reveals hypertrophy or thinning, and by 3D reconstruction of the data, which provides essential information about the size, extent, and localization of the lesion. In both cases, preliminary segmention of the cartilage is necessary. This article proposes an algorithm for automatic segmentation of the cartilage from 3D ultrasonic acquisitions of the rat patella, which includes the detection of the cartilage surface and the cartilage/bone interface. The method was designed on the assumption of regularity and smoothness of the interfaces. The use of a global threshold was sufficient to separate the patella area from the background. The cartilage/bone interface was detected by selection of regions of interest (ROIs) encompassing the interface, followed by the detection of the interface within these ROIs using the graph theory. The method was applied to 162 samples. The detection accuracy was judged to be very good or good in 99% of the cases for the cartilage surface and in 86% of the cases for the cartilage/bone interface. The mean cartilage thickness value in the central part of the patella obtained from the automatic detection method was compared to that obtained manually. The coefficient of correlation between the two measurements was 0.92. These results show that our method is reliable. Thus, fast processing of a large number of acquisitions and a more complete analysis of the cartilage surface become possible.
The precise delineation and excision of brain tumor extent allows to improve survival outcome and quality of life of surgically treated patients. In order to refine the resection of gliomas, we are ...developing a novel intraoperative probe specifically dedicated to the localization of residual tumor after the bulk has been excised. The probe, built around clear and plastic scintillating fibers, was designed to detect positrons emitted from radiolabeled brain tissue in order to discriminate more specifically neoplastic from normal tissues. The probe was also built to be directly coupled to the excision tool leading to simultaneous detection and removal of tumor. We report here performances of the first radio-isotopic configuration of the intraoperative probe which consists of a detection head composed of eight detection elements held around the excision tool in a closed packed annular arrangement. This head is coupled to an optic fiber bundle that exports the scintillating light to a multi-channel photomultiplier tube. The gamma ray background generated by the annihilation of beta + in tissues is eliminated by a real-time subtraction method. The detector exhibits a beta sensitivity of 139 cps/kBq and a gamma ray rejection efficiency of 99.5%. The ability of the probe to detect residual lesions was evaluated with a realistic brain phantom representing the surgical cavity and the boundaries of the tumor. We showed that lesions as small as 5 mm in diameter can be detected for tumor to normal tissue uptake ratios of fluorinated tracers greater than 3.5. This ratio is achieved with radiopharmaceuticals like 18 F-FET or 18 F-choline. These promising results suggest that the features of our system are compatible with in situ localization of residual radiolabeled tumors.
The ability of computerized parameters to discriminate benign from malignant breast nodules from digitized ultrasonic acquisitions has been assessed. The images of 75 lesions, including 19 lesions ...proved to be malignant at histology and 56 found to be benign, were digitized and characterized by morphometric and texture parameters. The texture parameters, derived from first-order statistics, run-length matrices and co-occurrence matrices, were computed in the entire lesion and in a ring-shape region surrounding the contour of the lesion. The strongest features were found to be issued from the second region. Further investigations confirmed that the discriminant information was contained in the external part of the lesion and, to a lesser extent, in the neighboring tissue. A linear discriminant analysis using three features yielded a sensitivity of 94.7% for a specificity of 80.4% and the “leave-one-out” technique confirmed the results. Comparison with the classifications given by radiologists let us assume that information revealed by texture features is able to help the physician in reducing the number of unnecessary biopsies.
The aim of this study was to compare the effectiveness of a hand-held preoperative compact imager (POCI) camera with conventional lymphoscintigraphy using a γ-camera for sentinel lymph node (SLN) ...detection in breast cancer. Methods: The main objective was to demonstrate the noninferiority of the POCI relative to conventional lymphoscintigraphy and to compare the number of SLNs detected by the 2 imaging devices. Our study, a clinical prospective, double-blind, noninferiority study, planned to include 200 patients with early breast cancer and started in January 2006. A standard SLN protocol (4 periareoiar injections of 37 MBq of ^sup 99m^Tc-nanocolloids, 2 h before lymphoscintigraphy) was performed preoperatively using a conventional γ-camera and then the POCI camera. Scans were obtained by 2 different nuclear medicine physicians unaware of each other's results. The day after, in the operating room, the surgeon, after receiving the previous results, used the counting probe for surgical SLN biopsy. The number and localization of axillary SLNs obtained by lymphoscintigraphy and the POCI and the duration of the whole procedure were determined. Results: Among the 162 patients included, 138 were evaluable. The POCI detected more SLNs than did lymphoscintigraphy in 50 patients (36%), the same number of in 54 patients (39%), and fewer SLNs in 34 patients (25%), representing 84 (61%) discordant pairs. The non-inferiority of preoperative compact imaging of axillary SLNs numbers was found to be statistically significant (95% confidence interval, 30%-52%, P = 0.025) using the McNemar test. The duration of acquisition was shorter using the POCI (<10 min in 84% n = 117 of patients; mean, 7.5 ± 3.3 min) than lymphoscintigraphy (13% n = 18 of patients; mean, 15.7 ± 3.4 min), with P < 0.001 using the McNemar test for paired proportions. Conclusion: Preoperative compact imaging using a hand-held camera was able to predict the number and localization of breast cancer SLNs and was not inferior to conventional lymphoscintigraphy in this study. Further studies will determine whether preoperative compact imaging could replace lymphoscintigraphy, especially in surgical centers without an on-site nuclear medicine department. PUBLICATION ABSTRACT
The beta-microprobe is a simple and versatile technique complementary to small animal positron emission tomography (PET). It relies on local measurements of the concentration of positron-labeled ...molecules. So far, it has been successfully used in anesthetized rats for pharmacokinetics experiments and for the study of brain energetic metabolism. However, the ability of the technique to provide accurate quantitative measurements using (18)F, (11)C and (15)O tracers is likely to suffer from the contribution of 511 keV gamma rays background to the signal and from the contribution of positrons from brain loci surrounding the locus of interest. The aim of the present paper is to provide a method of evaluating several parameters, which are supposed to affect the quantification of recordings performed in vivo with this methodology. We have developed realistic voxelized phantoms of the rat whole body and brain, and used them as input geometries for Monte Carlo simulations of previous beta-microprobe reports. In the context of realistic experiments (binding of (11)C-Raclopride to D2 dopaminergic receptors in the striatum; local glucose metabolic rate measurement with (18)F-FDG and H(2)O(15) blood flow measurements in the somatosensory cortex), we have calculated the detection efficiencies and corresponding contribution of 511 keV gammas from peripheral organs accumulation. We confirmed that the 511 keV gammas background does not impair quantification. To evaluate the contribution of positrons from adjacent structures, we have developed beta-Assistant, a program based on a rat brain voxelized atlas and matrices of local detection efficiencies calculated by Monte Carlo simulations for several probe geometries. This program was used to calculate the 'apparent sensitivity' of the probe for each brain structure included in the detection volume. For a given localization of a probe within the brain, this allows us to quantify the different sources of beta signal. Finally, since stereotaxic accuracy is crucial for quantification in most microprobe studies, the influence of stereotaxic positioning error was studied for several realistic experiments in favorable and unfavorable experimental situations (binding of (11)C-Raclopride to D2 dopaminergic receptors in the striatum; binding of (18)F-MPPF to 5HT1A receptors in the dorsal raphe nucleus).
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