Biomedical subjects

I N Weinberg

Publications and source records attributed to I N Weinberg.

7 recordsLinked to original sources

PubMed1997

Segmentation algorithms for detecting microcalcifications in mammograms.

The presence of microcalcification clusters in mammograms contributes evidence for the diagnosis of early stages of breast cancer. In many cases, microcalcifications are subtle and their detection can benefit from an automated system serving as a diagnostic aid. The potential contribution of such a system may become more significant as the number of mammograms screened increases to levels that challenge the capacity of radiology clinics. Many techniques for detecting microcalcifications start with a segmentation algorithm that indicates all candidate structures for the subsequent phases. Most algorithms used to segment microcalcifications have aspects that might raise operational difficulties, such as thresholds or windows that must be selected, or parametric models of the data. We present a new segmentation algorithm and compare it to two other algorithms: the multi-tolerance region growing algorithm that operates without the aspects mentioned above, and the active contour model that has not been applied previously to segment microcalcifications. The new algorithm operates without threshold or window selection, or parametric data models, and it is more than an order of magnitude faster than the other two.

Algorithms↗

PubMed1994

Feasibility study for positron emission mammography.

A feasibility study is presented for a small, low-cost, dedicated device for positron emission mammography. Two detector arrays above and below the breast would be placed in a conventional mammography unit. These detectors are sensitive to positron annihilation radiation, and are connected to a coincidence circuit and a multiplane image memory. Images of the distribution of positron-emitting isotope are obtained in real time by incrementing the memory location at the intersection of each line of response. Monte Carlo simulations of a breast phantom are compared with actual scans of this phantom in a conventional PET scanner. The simulations and experimental data are used to predict the performance of the proposed system. Spatial resolution experiments using very narrow bismuth germanate BGO crystals suggest that spatial resolutions of about 2 mm should be possible. The efficiency of the proposed device is about ten times that of a conventional brain scanner. The scatter fraction is greater, but the scattered radiation has a very flat distribution. By designing the device to fit in an existing mammography unit, conventional mammograms can be taken after the injection of the radio-pharmaceutical allowing exact registration of the emission and conventional mammographic images.

Biophysical Phenomena↗

PubMed1989

The C15O2 build-up technique to measure regional cerebral blood flow and volume of distribution of water.

A new method to measure regional CBF (rCBF) and volume of distribution of water is presented. It centres on recording the tissue build-up and retention of 15O-labelled water during the continuous inhalation of 15O-labelled carbon dioxide. Simultaneously, the arterial concentration is continuously monitored, and corrections for delay and dispersion in the recorded response are made by curve fitting. The values for the volume of distribution of water obtained in four normal subjects were close to reported in vitro values. Using the same fixed distribution volumes for both build-up and steady-state studies resulted in comparable rCBF values for both techniques.

Adult↗

PubMed1988

Validation of PET-acquired input functions for cardiac studies.

To validate the determination of the arterial input function by noninvasive dynamic PET imaging, measurements of blood-pool activity in canine LV by PET were compared to beta probe measurements of arterial blood withdrawn directly from the LV. PET scans were done during intravenous bolus injections of [13N]ammonia or 82Rb, while the activity of blood withdrawn continuously from a catheter inserted in the LV was measured with a beta probe. PET determinations of LV blood-pool activity were compared with dispersion-corrected beta probe time-activity curves. In 15 experiments involving four dogs under a wide range of physiologic conditions, LV time-activity curves obtained with PET matched well in shape with those obtained with the beta probe. Linear regression yielded slopes within 10% of unity (95% confidence interval) and high correlation (r greater than 0.968, p less than 0.001). We conclude that noninvasive measurement of the arterial input function by dynamic PET imaging is valid.

Ammonia↗

PubMedDate not supplied

99mTc MIBI scintimammography with a high resolution single tube gamma camera: preliminary study.

99mTc MIBI scintimammography is a sensitive and specific diagnostic technique for breast cancer detection when cancers more than 1 cm sized are considered. However the sensitivity falls in the case of submillimetric lesions. We developed a new Small Field of View, High Resolution Detector, able to image the breast in similar conditions of x-ray mammography: it allows the performance of Single Photon Emission Mammography (SPEM) studies. Seven patients with suspicion of malignant lesions were comparatively submitted to a Prone Scintimammography (PSM) by Anger camera and to a cranio-caudal view SPEM. The final diagnosis was reached by histopathology. Four malignant lesions were identified by SPEM but not by PSM, which that failed to image two submillimetric cancers. Both the cameras gave normal findings for benign lesions, confirming the high sensitivity of this technique. The results allow us to consider the SPEM camera as promising to improve scintimammographic sensitivity, even when small-sized tumors are examined.

Breast Diseases↗

PubMedDate not supplied

The role of Compton background and breast compression on cancer detection in scintimammography.

99mTc MIBI scintimammography is a promising diagnostic technique for cancer detection. Using a dedicated Small Field Of View Gamma Camera (SFOVGC) with the high spatial resolution recently developed, it is possible to improve the sensitivity and to achieve images in projections similar to mammography with the breast under moderate compression. This new technique is called Single Photon Emission Mammography (SPEM). Several factors affect the imaging of small cancers; breast thickness, tumor-collimator distance and body activity. A phantom study was performed to assess the role of breast compression in scintimammography. In this work we analyze the intensity and the energy distribution of Compton scattering affecting the breast scintigraphy, by a Germanium detector and by SFOVCG. Five patients with 7 to 18 mm sized cancer were studied. The intensity of Compton scattering resulted from 4 to 10 times greater than true events. The fundamental role played by breast compression to improve the scintimammographic sensitivity is discussed.

Breast↗

PubMedDate not supplied

Single tube gamma camera for scintimammography.

The development of large area Position Sensitive Photo Multiplier Tubes (PSPMT) by Hamamatsu is opening new imaging possibilities in Nuclear Medicine. In particular the realization of the 8" PSPMT prototype represents the first important technological advantage since the discovery of the Anger Camera. PSPMT virtually integrates in one hundreds PMT allowing the creation of dedicated detectors. A Single Tube Gamma Camera based on a 5" PSPMT dedicated to scintimammography is presented and discussed in this work. To optimize gamma camera response two different scintillating arrays were tested: YAP:Ce and CsI (Tl). Their overall size cover all photocathode active area, and crystal pixel size was 2 mm x 2 mm. The detection efficiency was comparable to that of Anger Camera. The best result was obtained by CsI (Tl) scintillating: an intrinsic spatial resolution of 1.6 mm FWHM and a relative energy resolution of 17% FWHM. New image possibilities in scintimammography are offered by Single Tube Gamma Camera operating in the same radiological projection of RX mammography.

Breast Neoplasms↗