Hoffmeister: Research

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My main areas of research are the following:

Ultrasonic Backscatter for Clinical Bone Assessment
Ultrasound is being used increasingly as a diagnostic tool for bone diseases such as osteoporosis. Commercial ultrasonic devices use through transmission techniques that require two ultrasonic transducers to be placed on either side of the bone. This severely restricts areas accessible to ultrasonic interrogation. We are developing backscatter techniques that require only a single transducer. We have found that high frequency (5-10 MHz) backscatter correlates significantly with bone mineral density and mechanical properties of bone.

Effect of Medical Implants on Magnetically Induced Currents in the Body
Patients who receive MRI scans are exposed to electrical currents that are induced in their bodies by the rapidly switched gradient magnetic fields. These currents are believed to be too weak to cause serious problems such as cardiac stimulation. However the effect of plastic and metal implants on these currents is not known. We have developed an experimental apparatus to study these effects. We have found that that plastic implants can have a very large effect, and we are focusing our attention on this because (unlike metal implants) no one else is considering it. We also have developed a theoretical model based on Coulomb′s Law and Faraday′s law that agrees well with our experiments.

Ultrasonic Characterization of the Curing Process of Cement
Ultrasound is well known for its nondestructive testing (NDT) applications. We are using ultrasonic techniques to characterize the curing process of various types of cement. This has included bone cement, and structural cement modified with fly ash (a waste product of coal powered electrical plants). Ultrasonic speed of sound and attenuation (measured as a function of time during curing) have proven very sensitive to changes in the properties of these cements as they cure.

Many students have contributed significantly to my research, and I am grateful to them for their hard work.  These students are listed below along with brief descriptions of their contributions.

David Johnson ’07- David performed ultrasonic backscatter measurements of human cancellous bone in the frequency range 0.6-15 MHz

John Janeski ’07- John performed ultrasonic backscatter measurements of human cancellous bone in the frequency range 5-10 MHz

Brian Steinert ’06- Brian mechanically tested specimens of human bone used in ultrasonic studies.

Daniel Keedy ’06- Daniel performed ultrasonic backscatter measurements of human cancellous bone in the frequency range 0.6-15 MHz.

Taylor Whaley’05 and Chip Hartigan ’05- Taylor and Chip analyzed videos of surgically exposed heart to study how the heart responded mechanically to weak AC electrical stimuli
 
Garney Caldwell ’05- Chad performed ultrasonic backscatter measurements of cancellous bone in the frequency range 2.5-7.5 MHz. 
 
Drew Shores ’05- Drew developed an experimental and theoretical model to describe how weak electrical currents induced in the body during MRI scans interact with plastic medical implants.

John Sexton ’04- John measured the area and wall thickness of the left ventricle of the heart during weak AC electrical stimuli.

Stu Johnston ’03- Stu processed ultrasound images of the heart during weak electrical stimulation.
 
Chad Jones ’03- Chad performed ultrasonic backscatter measurements of cancellous bone in the frequency range 2.5-7.5 MHz. 
 
Tom O’Hara ’03- Tom analyzed ultrasound “M-mode” images of the heart during weak AC electrical stimulation.  He also developed a computer model to simulate M-mode data.

Julie Auwarter ’01-Julie worked on two main projects.  The first involved monitoring the curing process of bone cement with ultrasound.  The second involved ultrasonic measurements of bone before and after the marrow was removed.

Andy Whitten ’00- Andy performed ultrasonic measurements of cancellous bone in the frequency range 1-3 MHz. 
 
Steve Smith ’00- Steve studied ultrasound images of the heart during electrical defibrillation shocks.
 
Will McKinney ’00- Will studied ultrasound images of the heart during weak electrical stimulation.