27 research outputs found
Testing the performances of different image representations for mass classification in digital mammograms
No full textThe classification of tumoral masses and normal breast tissue is targeted. A mass detection algorithm which does not refer explicitly to shape, border, size, contrast or texture of mammographic suspicious regions is evaluated. In the present approach, classification features are embodied by the image representation used to encode suspicious regions. Classification is performed by means of a support vector machine (SVM) classifier. To investigate whether improvements can be achieved with respect to a previously proposed overcomplete wavelet image representation, a pixel and a discrete wavelet image representations are developed and tested. Evaluation is performed by extracting 6000 suspicious regions from the digital database for screening mammography (DDSM) collected by the University of South Florida (USF). More specifically, 1000 regions representing
biopsy-proven tumoral masses (either benign or malignant) and 5000 regions representing normal breast tissue are extracted. Results demonstrate very high performance levels.
The area Az under the receiver operating characteristic (ROC) curve reaches values of 0.973 +/- 0.002, 0.948 +/- 0.004 and 0.956 +/- 0.003 for the pixel, discrete wavelet and overcomplete wavelet image representations, respectively. In particular, the improvement in the Az value with the pixel image representation is statistically significant compared to that obtained with the discrete wavelet and overcomplete wavelet image representations (two-tailed p-value < 0.0001). Additionally, 90% true positive fraction (TPF) values are achieved with false positive fraction (FPF) values of 6%, 11% and 7%, respectively
Tomographic approach to single-photon breast cancer imaging with a dedicated dual-head camera with VAOR (SPEMT): Detector characterization
No full textWe have developed a compact Single Photon Emission MammoTomography (SPEMT) scanner capable of imaging the breast for the detection of small size (T1b) tumors. The scanner has a vertical-axis-of-rotation (VAOR) geometry, in which two gamma cameras orbit around a pendulous breast of a prone patient. The SPECT system is rotating around the vicinity of the breast in order to achieve high spatial resolution. The system field-of-view is 147 mm diameter and 41.6 mm height. Each head is made up of one pixilated Nal(TI) crystal matrix with 2.2 mm pitch and 6 mm thickness coupled to three Hamamatsu H8500 64-anodes PMT's. The measured performance confirm that the system could overcome the present clinical sensitivity limit (about 1 cm diameter) for the detection of small size tumors
Looking for unliked ADPKD families in a sample of affected kindreds from Central and Southern Italy
No full textA single photon emission computer tomograph for breast cancer imaging
No full textWe have developed a tomograph for single photon emission imaging (SPECT) of the breast for the detection of small size tumors. The SPECT is mounted on a ring that is rotating around the breast with the patient in prone position. The breast will be imaged by two opposing detector heads of approximately 5 x 15 cm(2) each, with a field of view about 13 cm wide. Each head is made up of one pixilated NaI crystal matrix coupled to three Hamamatsu H8500 PMTs. A "general purpose" lead collimator is positioned in front of the crystal. Detailed simulations have been made for the optimization and the evaluation of the detector performances. Monte Carlo results indicate that tumors of 8 mm diameter are detectable with a tumor/background uptake ratio of 5:1. The experimental characterization of the detector head is presented. The rotating ring is now being assembled. (C) 2007 Elsevier B.V. All rights reserved
SPEMT imaging with a dedicated VAoR dual-head camera: preliminary results
No full textWe have developed a SPEMT (Single Photon Emission MammoTomography) scanner that is made up of two cameras rotating around the pendulous breast of the prone patient, in Vertical Axis of Rotation (VAoR) geometry. Monte Carlo simulations indicate that the device should be able to detect tumours of 8 mm diameter with a tumour/background uptake ratio of 5:1. The scanner field of view is 41.6 mm height and 147 mm in diameter. Each head is composed of one pixilated NaI(Tl) crystal matrix coupled to three Hamamatsu H8500 64-anodes PMT’s read out via resistive networks. A dedicated software has been developed to combine data from different PMT’s, thus recovering the dead areas between adjacent tubes. A single head has been fully characterized in stationary configuration both in active and dead areas using a point-like source in order to verify the effectiveness of the readout method in recovering the dead regions. The scanner has been installed at the Nuclear Medicine Division of the University of Pisa for its validation using breast phantoms.
The very first tomographic images of a breast phantom show a good agreement with Monte Carlo simulation results
Optimization of the acquisition parameters for a SPET system dedicated to breast imaging
No full textThis work is developed within the framework of a larger project, which aims to develop a multimodal CT-SPET system dedicated to breast imaging. The goal of this paper is to optimize the choice of the various parameters involved in the design of a SPET system dedicated to breast imaging. In particular, we simulated different collimators, different tumor to background (T/B) ratios for two different spherical tumors with diameters of 5 mm and 8 mm. The performance of the explored cameras were analyzed in terms of SNR and image contrast (IC) values, calculated on the reconstructed images. In addition, we investigated the visibility limits of the system, by modifying the tumor size, the T/B value, and the diameter of the breast phantom (8 cm, 10 cm, and 13 cm). As a general tendency, we found out that a high-resolution camera is preferable, in terms of image contrast On the other hand, the General Purpose collimator seems to give a smoother image, giving rise to SNR values comparable to those obtained with the High-Resolution collimator, even with a reduced contrast. High-sensitivity collimators seem to give a worse response on the reconstructed images. The 8 mm tumor is clearly visible for all the simulated conditions, even if it could be very close to the visibility limit for the High-Sensitivity collimator. The 5 mm tumor is close to the visibility limit for General Purpose and High-Resolution collimators, for a T/B ratio equal to 10:1 and is not visible with High-Sensitivity collimator. The smaller tumor is almost obscured by the background with the thickest breast (13 cm diameter)
SPEMT imaging with a dedicated VAoR dual-head camera: preliminary results
No full textWe have developed a SPEMT (Single Photon Emission MammoTomography) scanner that is made up of two cameras rotating around the pendulous breast of the prone patient, in Vertical Axis of Rotation (VAoR) geometry. Monte Carlo simulations indicate that the device should be able to detect tumours of 8 mm diameter with a tumour/background uptake ratio of 5:1. The scanner field of view is 41.6 mm height and 147 mm in diameter. Each head is composed of one pixilated NaI(Tl) crystal matrix coupled to three Hamamatsu H8500 64-anodes PMT's read out via resistive networks. A dedicated software has been developed to combine data from different PMT's, thus recovering the dead areas between adjacent tubes. A single head has been fully characterized in stationary configuration both in active and dead areas using a point-like source in order to verify the effectiveness of the readout method in recovering the dead regions. The scanner has been installed at the Nuclear Medicine Division of the University of Pisa for its validation using breast phantoms. The very first tomographic images of a breast phantom show a good agreement with Monte Carlo simulation results
Dna markers in diagnosis of adult dominant polycystic kidney disease.
No full textWe report the results of a biological and molecular study carried out on 11 Italian families, with a total of 111 individuals in which adult dominant polycystic kidney disease segregates. A restriction fragment length polymorphism analysis was performed. Two families have shown a genetic heterogeneity even if not phenotypically different from the other ones: they resulted unlinked to 16p markers. A prenatal diagnosis has been performed in a family of the linked type
GW231123:a binary black hole merger with total mass 190–265 <i>M</i><sub>⊙</sub>
No full textOn 2023 November 23, the two LIGO observatories both detected GW231123, a gravitational-wave signal consistent with the merger of two black holes with masses 137+23-18 M⊙ and 101+22-50 M⊙ (90% credible intervals), at a luminosity distance of 0.7–4.1 Gpc, a redshift of 0.40+0.27-0.25, and with a network signal-to-noise ratio of ∼20.7. Both black holes exhibit high spins— 0.90+0.10-0.19 and 0.80+0.20-0.52, respectively. A massive black hole remnant is supported by an independent ringdown analysis. Some properties of GW231123 are subject to large systematic uncertainties, as indicated by differences in the inferred parameters between signal models. The primary black hole lies within or above the theorized mass gap where black holes between 60–130 M⊙ should be rare, due to pair-instability mechanisms, while the secondary spans the gap. The observation of GW231123 therefore suggests the formation of black holes from channels beyond standard stellar collapse and that intermediate-mass black holes of mass ∼200 M⊙ form through gravitational-wave-driven mergers
