Grade Sheet – 600.145 HW #2Name 1: __________________Email/Phone: ______________Role/contribution: ___________ __________________________

Name 2: __________________Email/Phone: ______________

Role/contribution: ___________ __________________________

I/we have adhered to the rules on this homework assignment:

___________________________ ___________________________

(signature) (date) (signature) (date)

Problem 1 10

Problem 2.1 20

Problem 2.2.a 10

Problem 2.2.b 10

Problem 2.2.c 10

Problem 3 20

Problem 4 20

Problem 5 20

Totals 120

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

Image-guided prostate biopsy

• 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.

Problem: Plan in MRI, Execute in CT• 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

intraoperative

Computed

Notation & Formula Example

prostate

MRI images

biopsy target

MRI scanner

pelvis

MRI,ImF

Im,TargF

Im,ProstateF

Im,PelvisF

Measured

Suppose that we plan to pick out biopsy targets on MRI images

Computed

Notation & Formula Example

prostate

MRI images

biopsy target

MRI scanner

pelvis

MRI,ImF

Im,TargF

Im,ProstateF

Im,PelvisF

MRI,TargF

Pelvis,ProstateFPelvis,,TargF

Measured

MRI,Targ

Pelvis,Prostate

Pelvis,Targ

F ?

F ?

F ?

Computed

Notation & Formula Example

prostate

MRI images

biopsy target

MRI scanner

pelvis

MRI,ImF

Im,TargF

Im,ProstateF

Im,PelvisF

MRI,TargF

Pelvis,ProstateFPelvis,,TargF

Measured

MRI,Targ

Pelvis,Prostate

Pelvis,Targ

F ?

F ?

F ?

Computed

Notation & Formula Example

prostate

MRI images

biopsy target

MRI scanner

pelvis

MRI,ImF

Im,TargF

Im,ProstateFIm,PelvisF

MRI,TargF

Pelvis,ProstateFPelvis,,TargF

Measured

MRI,Targ MRI,Im Im,Target

Pelvis,Prostate

Pelvis,Targ

F F F

F ?

F ?

Computed

Notation & Formula Example

prostate

MRI images

biopsy target

MRI scanner

pelvis

MRI,ImF

Im,TargF

Im,ProstateFIm,PelvisF

MRI,TargF

Pelvis,ProstateFPelvis,,TargF

Measured

MRI,Targ MRI,Im Im,Target

Pelvis,Prostate

Pelvis,Targ

F F F

F ?

F ?

Computed

Notation & Formula Example

prostate

MRI images

biopsy target

MRI scanner

pelvis

MRI,ImF

Im,TargF

Im,ProstateF

Im,PelvisF

MRI,TargF

Pelvis,ProstateFPelvis,,TargF

Measured

MRI,Targ MRI,Im Im,Target

1Pelvis,Prostate Im,Pelvis Im,Prostate

Pelvis,Targ

F F F

F F F

F ?

Computed

Notation & Formula Example

prostate

MRI images

biopsy target

MRI scanner

pelvis

MRI,ImF

Im,TargF

Im,ProstateF

Im,PelvisF

MRI,TargF

Pelvis,ProstateFPelvis,,TargF

Measured

MRI,Targ MRI,Im Im,Target

1Pelvis,Prostate Im,Pelvis Im,Prostate

1Pelvis,Targ Im,Pelvis Im,Prostate

F F F

F F F

F F F

Computed

Notation & Formula Example (modified)

biopsy target

Measured

prostate

MRI images

MRI scanner

pelvis

MRI,ImF

Prostate,TargF

Im,ProstateF

Im,PelvisF

MRI,TargFIm,TargF

Suppose that we plan to use standard biopsy positions defined with respect to the prostate, instead of picking the targets out with respect to the MRI Image

Computed

Notation & Formula Example (modified)

biopsy target

Measured

MRI,Targ MRI,Im Im,Prostate Prostate,Targ F F F F

prostate

MRI images

MRI scanner

pelvis

MRI,ImF

Prostate,TargF

Im,ProstateF

Im,PelvisF

MRI,TargF

Problem 1

• Assume that the surgeon wants to use a standard biopsy pattern defined with respect to the prostate, but wants to know the target coordinates with respect to the pelvis.

• Draw a diagram similar to the examples (including use of a green multi-segment arrow) showing how this calculation can be performed

• Give the corresponding formula for FPelvis,Targ

Pelvis,Targ F ?

Problem : 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

Copyright © CISST ERC, 2001 Engineering Research Center for Computer Integrated Surgical Systems and Technology

Schematic drawing of the prototype system

DICOM images

CT table

CT computer &DICOM server

Planning & control computer

RobotPatient

Surgeon

CT gantry

Problem 2: CT-guided Biopsy

• Some of the pertinent coordinate systems are shown below. There may be others.

patient

prostate

other anatomy

cancer

MRI images biopsy targets

patient

prostate

other anatomy

cancer CT scanner

robot base

robot needleholder

CT images

needle tip

preoperative

biopsy targets

intraoperative

MRI scanner

Problem 2 (con’d)

Question 2.1: 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 2.2

Problem 1 (continued)Question 2.2: 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).

a) Explain how these relationships will be determined and identify the steps in the procedure that will be used to determine them.

b) 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.

c) 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 •…

Problem 3: Ultrasound Guidance

Question 3: 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

2.1 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.

Problem 5: Comparison

Question 5: Compare the systems described in your answers to questions 1 and 2, using criteria similar to those you used in Homework #1.

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?