BME233_assignment11

BME233_assignment11 - BME 233 Modern Diagnostic Imaging...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
BME 233 – Modern Diagnostic Imaging Systems Spring 2011 Homework Assignment #11 Posted: April 5, 2011 Due: April 12, 2011 at the beginning of class Problem 1: (10 points) Suppose a slice-select gradient Gz = 20 mT/m is used to excite a slice which is 10mm thick. a) What is the required RF bandwidth? (5 points) b) If Gz is reduced to 5mT/m, but τ RF is unchanged, by what factor is the total number of zero crossings increased or decreased? (5 points)
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Problem 2: (30 points)
Background image of page 2
Fig: 2D spin echo. The arrow pointing downwards in the gradient table indicates that the phase encoding gradient is stepped sequentially from its most positive value to its most negative value. This would have the same effect as an upward arrow in a sequence without the Pi pulse. There is no rephrasing gradient required for the Pi pulse as a symmetric slice select gradient is self refocusing.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Assume that the phase Phi is defined such that a pi-pulse reverses the accumulated phase of all the spins: φ Æ - φ . In terms of k-space, the pi pulse is equivalent to a reflection
Background image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 6

BME233_assignment11 - BME 233 Modern Diagnostic Imaging...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online