Lecture 1 Notes

Three important factors affect the choice of

Info icon This preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: (ZT) is ~15 times greater than Z of tissue (ZL) –  Placing crystal directly over skin would result a large amount of energy be reflected back from the boundary »  R= |(ZL-ZT)/(ZL+ZT)| ~1 Matching layer –  layer Zl = ZT Z L = λ/4 thickness –  ZI = √(ZTZL) –  Maximize energy transfer into the body –  Show as a homework(*) Problems: Finding material with exact Zl value Transducer   - Doppler Therapy and bandwidth. Three important factors affect the choice of frequency: 1) tissue attenuation, 2) required depth of penetration, and 3) system dynamic range. There is no strict rule for equating these variables and arriving at an optimum frequency. Generally, the highest frequency that provides adequate penetration is selected; this optimizes the lateral resolution [cf. (1)] . The pulse bandwidth needed to obtain good axial resolution poses an altogether different problem. Here, the tendency is to select the widest bandwidth (shortest pulse) because this provides the best axial resolution in water. Unfortunately, wide bandwidth sometimes leads to reduced sensitivity and loss of lateral resolution at depth in attenuating media [16]. The latter effect results from the selective attenuation of the higher Array types a)  b )  c)  d )  e)   Linear Sequential (switched) ~1 cm × 10-15 cm, up to 512 elements Curvilinear similar to (a), wider field of view Linear Phased up to 128 elements, small footprint → cardiac imaging 1.5D Array 3-9 elements in elevation allow for focusing 2D Phased Focusing, steering in both dimensions Homework   Reading:   Problems: –  Prince and Links, Medical Imaging Signals and Systems, Chap. 10 (Sec. 10.5 not required),11.2,11.3 –  –  –  –  –  –  –  P10.1 P10.3 P10.6 P10.8 P10.12 P10.13 Considering the (λ/4) matching layer in a transducer. Show that the transmitted energy into the tissue is maximized with an impedance of √(ZTZL) Z l = ZT Z L...
View Full Document

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern