2. Imaging For Prostate Cancer:
David
Background
Geffen
School of
A 2011 Harvard study found that a
Medicine
quarter of men with low risk cancer
received scans they did not “need”
A number of high-risk men do not get
the scans needed to plan treatment
Newer modalities such as MRI and PET
are not widely used
3. Imaging for Prostate Cancer:
David
Considerations
Geffen
School of
Whether a man needs imaging, and
Medicine
what kind, is based on risk
PSA
Number and % of positive biopsies and
Grade of cancer on biopsy
Age and overall health
Imaging for staging benefits high risk
more than low risk
Imaging can also be used to localize
cancer within (& around) the prostate
4. Imaging Types
David
Geffen
School of
Prostate and surrounding tissue
Medicine
Color power Doppler ultrasound (PDUS)
Magnetic resonance imaging (MRI)
Shear wave ultrasound elastography
Bones and lymph nodes
Computed tomography (CT)
Radionuclide (planar) bone scan (RBS)
Positron emission tomography (PET)
MRI
6. Ultrasound
David
Geffen
School of
Regular gray-scale ultrasound can
Medicine
identify cancer, but cannot
discriminate it from benign changes
Because of the abnormal blood supply,
a Doppler signal shift is seen with
prostate cancer on PDUS
However, whether this results in increased
detection varies by institution
Ultrasound IV contrast dye increases
yield, but is not approved in the USA
8. Ultrasound Elastography
David
Geffen
School of
Elastography is the measurement of
Medicine
the stiffness of tissue
Cancers are stiffer than normal tissue
New elastographic techniques
measure the shear wave tissue
properties of ultrasound using
Young’s modulus
Biopsy detection yield improves
This may identify men who do not
need biopsies, but this is unknown
9. Prostate MRI: Why?
David
Geffen
School of
The decision to remove the prostate
Medicine surgically vs. radio/chemotherapy is
based primarily on clinical factors
PSA
Biopsy
Physical Examination
These factors cannot reliably tell if the
cancer has spread beyond the
prostate, nor on which side
Systematic biopsies can and often do
miss the most aggressive tumors
10. Background: Prostate Cancer
David
Statistics– Screening
Geffen
School of
Medicine
Breast cancer has
the mammogram
Colon cancer has
colonoscopy
Courtesy AdMeTech.org
12. What is MRI
David
Geffen
School of
Magnetic Resonance Imaging uses
Medicine
magnetic pulses to generate images of
tissue in the body
Images can be based on inherent
magnetic properties of tissue to
delineate anatomy or on functional
parameters
Blood flow
Cellular packing and disorder
Concentrations of chemicals
13. Components of MRI
David
Geffen
School of
T2-weighted imaging for anatomy
Medicine
Diffusion-weighted imaging to
evaluate cellular packing and disorder
Perfusion (dynamic contrast) imaging
for blood flow
Spectroscopic imaging to measure
levels of chemicals involved in normal
prostate function and cancer
14. For what does prostate MRI look?
David
Geffen
School of
Location and amount (and possibly
Medicine
aggressiveness) of cancer in the
prostate
Spread of prostate cancer
Seminal vesicles and neurovascular
bundle (nerves that run along prostate)
Lymph nodes
Bones
15. Prostate MRI–
David
the Holy Grail of Prostate Imaging?
Geffen
School of
Prostate MRI involves lying motionless
Medicine
on a table for about an hour
The only needles involved are an IV
and an injection of a drug for cramps
Resolution and contrast are superior
to ultrasound and CT scanning
Completely safe except in rare cases
Pacemaker
Claustrophobia
Kidney failure
16. Prostate MRI–
David
Anatomical Characterization
Geffen
School of
Conventional MRI techniques,
Medicine
combined with the optimized signal-
to-noise ratio achieved with the
endorectal coil, provides high
resolution images of the prostate
These images are used to look at the
area around the prostate for invasion
of the capsule and seminal vesicles
17. Criteria for Prostate Cancer on T2WI
David
Geffen Cancer appears dark
School of
Medicine (red arrow) against
the bright normal
gland
Extension to seminal
vesicles (gold arrow)
indicates invasion
Obliteration of the
rectoprostatic angle
(preserved, green
arrow) would
indicate
extracapsular
extension
18. Signs of Extracapsular Extension
David
Geffen
School of
Gross extension beyond the
Medicine expected prostatic capsule is
invasion outside the prostate
Other signs suggest capsular
involvement or microscopic
extension
Broad base of contact
Bulging
Blurring or irregularity
The small dots at the
rectoprostatic angle may
represent the nerve bundle
19. MRI Spectroscopy:
David
Chemical Characterization
Geffen MRI can determine the
School of
Medicine
concentration of some
chemicals, although
the resolution is less
than anatomic imaging Abnormal
High Normal
Choline is a marker of choline High
peak
cellular proliferation citrate
peak
and is increased in
cancer
Abnormal
Citrate is a normal low citrate
constituent of healthy peak
Normal
prostate cells low
“Spectra,” or line choline
peak
graphs, show the
concentration of these
chemicals
20. MRI Spectroscopy:
David
Chemical Characterization
Geffen
School of
Medicine
Anatomic image
showing bilateral
PZ dark areas
Spectra from the
patient’s right
shows abnormal
spectra consistent
with cancer
Spectra from the
left shows normal
spectra most likely
consistent with old
inflammation
21. Diffusion-Weighted MRI:
David
Cellular Density
Geffen
School of
Prostate cancer cells are more densely
Medicine packed than healthy cells
This restricts free water motion in the cells
MRI can detect motion in addition to
chemicals
MRI generates a map of free water motion
(“Brownian motion”) to localize densely
packed cells in areas of old inflammation
which are already dark
22. Diffusion-Weighted
David
MRI: Cellular Density
Geffen
School of
The peripheral zone
Medicine on the upper image
is uniformly dark,
likely from old
inflammation
The diffusion map
localizes cancer to
the patient’s right
side
23. MRI Perfusion Imaging:
David
Blood Flow Dynamics
Geffen
School of
Cancer requires a rich blood supply
Medicine
Tumors secrete chemicals that grow
new blood vessels
MRI can track contrast dye and
identify areas of abnormal blood flow
Fast imaging can generate snapshots
Complex computer models can then
generate parameters of blood flow
24. MRI Perfusion
David
Imaging
Geffen A dark area is
School of
Medicine known proven
cancer
This same area has
impaired diffusion
= densely packed
cells
Abnormal perfusion
map signifies new
blood vessels
25. Prostate MRI: Holy Grail or Yet
David
Another Drain on Health Care?
Geffen
School of
Again, not a straightforward answer
Medicine
Prostate MRI is probably neither, but
has specific uses:
Guiding biopsies
Surveillance
Presurgical staging for moderate-risk
disease and minimally-invasive therapy
Follow-up
26. Prostate MRI: Biopsy Guidance
David
Geffen
School of
In the face of a rising PSA and
Medicine negative biopsy, a “second look” is
warranted
MRI can pinpoint the most suspicious
area in the prostate
Biopsy can be done directly with MRI
or with ultrasound/MRI image fusion
under ultrasound guidance
27. Biopsies: MRI, Ultrasound, or None
David
At All!?
Geffen
School of
Currently, MRI has not been proven to
Medicine exclude significant cancer
Whether this is true is being investigated
Most ultrasound biopsies are
systematic, not based on imaging
findings
MRI-guided biopsies can target
suspicious areas directly with
confirmation
But MRI machines cost as much as 10x
as an ultrasound machine
28. Biopsies: MRI, Ultrasound, or Both!?
David
Geffen
School of
New technology can fuse MRI data
Medicine
with ultrasound
Suspicious findings from MRI can be co-
localized on ultrasound and biopsied
This can expand image-guided
biopsies to patients where MRI
biopsies are unavailable
29. Prostate MRI: Active Surveillance
David
Geffen
School of
In patients with low volume, low grade
Medicine
disease, MRI provides two advantages
Screen for missed areas suspicious for
high-grade cancer
Baseline imaging for follow-up, to look for
subtle changes
30. Prostate MRI: Therapy Planning
David
Geffen
School of
MRI provides two pieces of
Medicine
information which are useful when
planning surgical or radiation therapy
Overall size and location of the prostate
and cancer within it
Spread of tumor beyond the prostate,
especially into sensitive nerve bundles or
the bladder or rectum
MRI can also detect spread to the
lymph nodes or bones in the pelvis
31. Prostate MRI: Follow-Up Rising PSA
David
Geffen
School of
A rising PSA level after prostatectomy
Medicine suggests recurrence of cancer
MRI has been shown to be sensitive to
detect recurrent cancer
Surgical bed
Bones
Lymph nodes
MRI can also detect recurrence in the
radiation therapy field
32. The Dreaded Coil – Is It Necessary?
David
Geffen
School of
Medicine
The endorectal coil improves
image quality about 10-fold
It is only necessary to characterize
the prostate capsule for invasion
near the neurovascular bundle
It improves quality of spectroscopy
Not needed for cancer detection
For example, biopsy planning
33. Staging for Bones and Lymph Nodes
David
Geffen
School of
The use of CT and bone scans for
Medicine
prostate cancer staging primarily
benefits intermediate to high risk men
Guidelines were established over a
decade ago and remain largely
unchanged
From a 2007
article by H
Hricak in the
journal
Radiology
35. CT Scans for Staging
David
Geffen
School of
Computed Tomography is a 3D X-ray
Medicine
It is sensitive for enlarged lymph
nodes and bony abnormalities
It is not sensitive for spread of cancer to
small lymph nodes
Some bone lesions are nonspecific on CT
– they could be cancer or benign
IV and oral contrast improves
detection of lymph nodes
It does not characterize the prostate
36. Why Get a CT Scan?
David
Geffen
School of
Treatment planning
Medicine
e.g. external beam radiation therapy
Treatment monitoring
But PSA monitoring is cheaper
Confirm no obvious disease outside of
pelvis
Confirm bone scan findings
38. Radionuclide Bone Scan
David
Geffen
School of
99Tc-MDP is a radioactive compound
Medicine
taken up in areas of bone turnover
Reflects the body’s response to cancer,
not the cancer itself
Some other tumors are not “hot” on RBS
Only detects bone metastases
False positives in benign diseases, e.g.
arthritis, can be identified on X-ray
Fast, complete survey of skeleton
39. Why Get a Bone Scan?
David
Geffen
School of
Treatment planning, e.g.
Medicine
External beam radiation therapy
Samarium-153-EDTMP or Strontium-89
Treatment monitoring
But PSA monitoring is cheaper
Confirm no bone disease outside of
pelvis
Characterize pain
41. PET for Prostate Cancer
David
Geffen
School of
Conventional PET scanning can often
Medicine detect spread of higher-grade disease
However, current PET agents are less
good for prostate than other cancers
Experimental agents which show
promise have not been shown useful
in larger studies
Bone scans with 18Fluoride are also
promising
42. PET Scans With More Specific
David
Agents
Geffen
School of
Conventional PET scans use an analog
Medicine
of glucose (sugar) to highlight the
increased metabolism of cancer
Prostate cancer has cell surface
receptors for testosterone
Researchers at Sloan-Kettering at
Cornell devised a PET agent which
mimics testosterone
43. PET Scans With Testosterone-
David
Specific Agent
Geffen
School of
Comparison of testosterone (A) and
Medicine
glucose (B) labeling on PET
Some tumors are
equally well seen
Others are more
obvious on the
testosterone scan
44. PET Scans With Choline and Fluroide
David
Geffen
School of
Medicine
As seen on MRI, choline is increased in
prostate cancer
A PET compound, 18Fluorocholine, is
concentrated in high cellular turnover
18Fluoride is taken up in
most bone lesions
CT on right, PET on left
18
FCholine on top, 18F below
White arrow: benign
Black arrows: cancer
46. MRI for Lymph Nodes and Bones
David
Geffen
School of
MRI has superior sensitivity to CT for
Medicine bone metastases but only slightly
Can still be confused by benign changes
MRI is equally sensitive to CT for
lymph nodes
Costs more and takes longer to scan
Still relies on lymph node enlargement
A MRI contrast agent to detect micro-
metastases to lymph nodes was not
approved, but a new one is under
review
47. MRI Lymph Node Imaging
David
Geffen
School of
Medicine
Benign lymph node
Lymph node with
malignant
infiltration
Partial infiltration
Courtesy M Harisinghani, Mass. Gen. Hospital
48. Take Home Points
David
Geffen
School of
Medicine has many options for
Medicine
imaging prostate cancer
Which one depends on the overall risk
level and planned treatment
Some modalities are better for
evaluating the prostate itself
Others are useful for whole body
staging
