A theoretical investigation of the imaging of extended objects is presented using a Fresnel zone plate as a coded aperture with coherent-optical image reconstruction. Faithful images are obtained only for small objects; artifacts are introduced in the images of large objects. Attempts to increase image fidelity are shown to be only moderately successful.
The feasibility of using multilayered transducers for variable frequency interstitial ultrasound thermal therapy was investigated. KLM calculations and experimental measurements evaluated the ability to transmit high intensity ultrasound at multiple frequencies from a single transducer. Heating simulations demonstrated the improved control over lesion depth with this design. Using a quarter wavelength PZT front "mismatching" layer, two transmission bands at 3.5 and 7.5 MHz were possible, resulting in the ability to control the lesion depth by a factor of 1.5 in tissue.
ADVERTISEMENT RETURN TO ISSUEPREVArticleRadiolytic yields of hydrated electrons at 30 to 1000 picoseconds after energy absorptionJohn W. Hunt, R. K. Wolff, M. J. Bronskill, Charles D. Jonah, E. J. Hart, and Max S. MathesonCite this: J. Phys. Chem. 1973, 77, 3, 425–426Publication Date (Print):February 1, 1973Publication History Published online1 May 2002Published inissue 1 February 1973https://pubs.acs.org/doi/10.1021/j100622a025https://doi.org/10.1021/j100622a025research-articleACS PublicationsRequest reuse permissionsArticle Views72Altmetric-Citations30LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts
Magnetic resonance (MR) imaging of the spinal cord frequently demonstrates, especially on sagittal sections, a central stripe that mimics a true syrinx. This syrinx-like manifestation of a truncation artifact occurs in objects having a width of only a few pixels and was demonstrated by calculations verified with phantom MR images. Healthy volunteers and two patients with a syrinx and cervical spondylosis, respectively, underwent MR imaging. By increasing the number of phase-encoding steps, decreasing the field of view, and switching phase- and frequency-encoding axes, the syrinx-like artifact can be eliminated.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSubnanosecond observations of the solvated electronM. J. Bronskill, R. K. Wolff, and John W. HuntCite this: J. Phys. Chem. 1969, 73, 4, 1175–1176Publication Date (Print):April 1, 1969Publication History Published online1 May 2002Published inissue 1 April 1969https://pubs.acs.org/doi/10.1021/j100724a083https://doi.org/10.1021/j100724a083research-articleACS PublicationsRequest reuse permissionsArticle Views49Altmetric-Citations34LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts
An evaluation was made of 1030 computed tomography (CT) scans performed on cancer patients. Seventy percent of the scans taken were of the pelvis, abdomen, or thorax. Both referring clinicians and radiologists rated the diagnostic and management efficacy of each scan using a simple scale of values. Over 50% of the scans provided unique diagnostic information: 39% resulted in a change in diagnosis or in known extent of disease; and 14% led to a change in patient management. The fraction of abnormal results was not a reliable measure of efficacy. Specific groups of patients were identified, which demonstrated that both diagnostic and management efficacy should be measured in assessing the value of CT as a diagnostic modality.
To characterize changes in the MR parameters of tissues due to thermal coagulation, a series of T(1), T(2), diffusion, and magnetization transfer measurements were performed on a variety of ex vivo tissues: murine slow twitch skeletal muscle, murine cardiac muscle, murine cerebral hemisphere, bovine white matter, murine liver tissue, bovine retroperitoneal adipose tissue, hen egg white, human prostate and human blood. Standardized heat treatments were performed for each tissue type, over the temperature range from 37 degrees C to 90 degrees C. For all tissues, changes in each MR measurement resulting from thermal coagulation were observed above a threshold temperature of approximately 60 degrees C. These changes are explained based on biophysical knowledge of thermal damage mechanisms and the MR properties of normal tissues, and are particularly relevant for interpreting the changes in image contrast that are observed when MRI is used to guide and monitor thermal coagulation therapy procedures. Magn Reson Med 42:1061-1071, 1999.
