1. Grade Sheet – 600.145 HW #2 Problem 1.1 20 Problem 1.2.a 10
Name 1: __________________ /Phone: ______________
Role/contribution: ___________ __________________________
Name 2: __________________ /Phone: ______________
Role/contribution: ___________ __________________________
Problem 1.1 20
Problem 1.2.a 10
Problem 1.2.b
Problem 1.2.c
Problem 2
Problem 3
Problem 4
Totals
110
I/we have adhered to the rules on this homework assignment:
___________________________ ___________________________
(signature) (date) (signature) (date)

2. Homework groundrules Work in groups of at most 2 people
Do not work with other groups on homework
Do not refer to previous years’ homework
Include the cover sheet on the homework
Both students should sign the honor pledge
You should state what each of you did

3. Image-guided prostate brachytherapy
Consider the problem of prostate biopsy under image guidance.
Currently, we are exploring several possible guidance scenarios for this problem:
trans-rectal ultrasound guidance
in-scanner CT guidance
in-scanner MRI guidance
Of these modalities:
Ultrasound enables you to see the outline of the prostate and urethra. It does not show cancer directly. Seeds and needles are visible, though rather fuzzily. Bone is visible, but borders are poor.
CT shows bone really well and the outline of the prostate very poorly. It does not show cancer directly. Seeds and needles show up well.
MRI shows prostate and cancer well, but shows bone poorly. Needles and seeds can show up as loss-of-signal areas. Ferromagnetic materials or large metal pieces or coils can cause great imaging problems.

4. Problem 1: CT-guided Biopsy
For the CT guided system, we will assume that a preoperative MR scan is available showing the suspected cancer lesions.
The intraoperative system resembles the in-scanner system shown in class
preoperative
patient
other anatomy
prostate
cancer
MRI images
biopsy targets
patient
other anatomy
CT images
cancer
CT scanner
biopsy targets
prostate
robot needle holder
robot base
intraoperative
needle tip

5. Problem : CT guidance
For the CT guided system, we will assume that a preoperative MR scan is available showing the suspected cancer lesions.
The intraoperative system resembles the in-scanner system shown in class

6. Problem 1: CT-guided Biopsy
preoperative
patient
Some of the pertinent coordinate systems are shown below. There may be others.
other anatomy
prostate
cancer
MRI scanner
MRI images
biopsy targets
patient
other anatomy
CT images
cancer
CT scanner
biopsy targets
prostate
robot needle holder
robot base
intraoperative
needle tip

7. Problem 1 (con’d)
Question 1.1: Describe a procedure for targeted biopsy of prostate cancer lesions based on the use of preoperative MRI images and intraoperative CT. Your answer should include a discussion of what steps need to be done preoperatively and what steps need to be done intraoperatively. It should include a discussion of the information developed in each step and of how that information will be used in subsequent steps. It should also include a brief discussion of how this information relates to concepts such as “segmentation” and “registration” discussed in class.
Hint: A good way to do this is to develop a flow chart and then include a discussion of each step. It also sometimes helps to make a sketch showing the patient, equipment, etc. at key steps. Finally, consider this answer in concert with the answer to question 1.2

8. Problem 1 (continued)
Question 1.2: Using a graphical method similar to that developed in class, show the key relationships between the various coordinate systems needed to perform this procedure. Assign a symbolic name to each relationship (e.g., Frobot,needle-holder).
Explain how these relationships will be determined and identify the steps in the procedure that will be used to determine them.
At each step in the procedure, use a graphical means to illustrate what is known and what is not yet known. A preferred way to do this is to use colors or heavy vs thin lines. Please follow the convention from class that dashed lines mean things that change over time and solid lines mean things that are assumed not to change.
Using the method shown in class, give an expression for Frobot,needle-holder that will place the needle tip on a desired biopsy target. E.g., Frobot,needle-holder=Fa,b •Fc,b-1 •…

9. Problem 2: Ultrasound Guidance
Question 2: Suppose now that the CT system has been replaced with a trans-rectal ultrasound system, and that the robot has been modified to work with this system.
Explain how you would modify your procedure from question 1.1 to enable you to use it in this context. Again, words like “segmentation” and “registration” are likely to be part of the answer.
Show a modified relationship graph for key steps
Hint: pay attention to what shows up well in both MRI and Ultrasound.

10. Problem 3: Comparison
Question 3: Compare the systems described in your answers to questions 1 and 2, using criteria similar to those you used in Homework #1.

11. Problem 4: No preop MRI
Question 4: Suppose that there is no preoperative MRI. I.e., we have decided that this patient is a candidate for biopsy based on elevated PSA levels. How would this affect your biopsy procedure and system?