Calculate the dwell time for the acquisition

MRES7100 Assignment 2 Semester 1 2018

Assignment 2 will be marked out of 20 as below, and then scaled to 16. Q1. (10 marks) Examine the images A and B acquired at 7T below. For each image, discuss the origin of the contrast observed in the CSF, white matter (WM) and grey matter (GM). As part of your answer:

a. state the type of weightings in each image and give brief reasoning (4 marks) b. suggest a sequence that could produce this weighting for each image ( 2 marks) c. suggest possible range of TE, TR, and TI (if appropriate) values that might

produce these images given the following properties: • average T1 at 7T: CSF 4sec, WM 1.4sec and GM 2sec • approx. T2: CSF 500ms, WM 40ms and GM 50ms (4 marks)

A B

Q2. (10 marks) Image B above was acquired with the following acquisition parameters: FOV 23cm x 23cm, receiver BW 78,080Hz, pixel size 0.72mm x 0.72mm.

a. Draw a representative sequence diagram for this pulse sequence. (5 marks) (Do not copy and paste a graphic from a text or the web – draw by freehand if necessary and insert a scan or photograph.) Include:

• All necessary RF pulses • All gradient pulses • Echo signals • Indicate TR and TE and other critical parameters if appropriate • Label each line of the sequence

b. Calculate the dwell time for the acquisition (1 mark) c. Calculate the read gradient strength used in mT/m (3 marks) d. Calculate the image matrix size (1 mark)

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