Details of mpMRI of prostate is given.

3. o Magnetic Resonance Imaging (MRI) has been used for
noninvasive assessment of the prostate gland and surrounding
structures since the 1980s.
o Initially, prostate MRI was based solely on morphologic
assessment using T1‐weighted and T2‐weighted pulse sequences,
and its role was primarily for locoregional staging in patients with
biopsy proven cancer.
o However, it provided limited capability to distinguish benign
pathological tissue and clinically insignificant prostate cancer from
significant cancer.

4. Advances in technology have led to the development of
multiparametric MRI (mpMRI), which combines
o Anatomic T2W with
o Functional and physiologic assessment, including
diffusion‐weighted imaging (DWI) and its derivative
apparent‐diffusion coefficient (ADC) maps,
o Dynamic contrast‐enhanced (DCE) MRI, and
o Sometimes other techniques such as MRS.

5. 1. Magnetic Field Strength
 The fundamental advantage of 3T compared with 1.5T lies
in an increased signal‐to‐noise ratio (SNR), which
theoretically increases linearly with the static magnetic
field.
 1.5T and 3.0T can provide adequate and reliable
diagnostic exams when acquisition parameters are
optimized and appropriate contemporary technology is
employed.

6.  Although prostate MRI at both 1.5 T and 3T has
been well established, most members of the
PI‐RADS Steering Committee prefer, use, and
recommend 3T for prostate MRI.
 1.5T should be considered when a patient has an
implanted device that has been determined to be
MR conditional at 1.5T, but not at 3T.

7. 2. Endorectal Coil (ERC)
 When integrated with external (surface) phased array coils,
endorectal coils (ERCs) increase SNR in the prostate at any magnetic
field strength.
 ERCs can also be advantageous for larger patients where the SNR in
the prostate may be compromised using only external phased array
RF coils.

8.  At 3T without use of an ERC, image quality can be
comparable with that obtained at 1.5T with an
ERC.
 However, use of an ERC may increase the cost and
time of the examination, deform the gland, and
introduce artifacts. In addition, it may be
uncomfortable for patients and increase their
reluctance to undergo MRI.

10. 3.Computer-Aided Evaluation (CAE) Technology
 Computer‐aided evaluation (CAE) technology using
specialized software or a dedicated workstation is not
required for prostate mpMRI interpretation.
 However, CAE may improve workflow (display, analysis,
interpretation, reporting, and communication), provide
quantitative pharmacodynamic data, and enhance lesion
detection and discrimination performance for some
radiologists, especially those with less experience
interpreting mpMRI exams.

11. A.Normal Anatomy
From superior to inferior,
the prostate consists of
The base (just below the
urinary bladder),
The midgland, and
The apex.

16. A. Normal Anatomy
It is divided into four histologic zones:
a) The anterior fibromuscular
stroma, contains no glandular
tissue;
b) The transition zone (TZ),
surrounding the urethra proximal
to the verumontanum, contains
5% of the glandular tissue
c) The central zone (CZ), surrounding
the ejaculatory ducts, contains
about 20% of the glandular tissue;
and
(d) The outer peripheral zone (PZ),
contains 70%‐80% of the
glandular tissue.

17. • Base has 6 sectors on each side:
• AS: anterior fibromuscular stroma
• TZ: anterior and posterior transition zone
• PZ: anterior and posterior zone
• CZ: central zone around the ejaculatory ducts
• Midportion also has 6 sectors on each side:
• AS: anterior fibromuscular stroma
• TZ: anterior and posterior transition zone
• PZ: anterior, posteromedial and posterolateral peripheral zone
• Apex also has 6 sectors on each side:
• AS: anterior fibromuscular stroma
• TZ: anterior and posterior transition zone
• PZ: anterior, posteromedial and posterolateral peripheral zone

19. oApproximately 70%‐75% of prostate
cancers originate in the PZ and 20%‐30% in
the TZ.
o Cancers originating in the CZ are
uncommon, and the cancers that occur in
the CZ are usually secondary to invasion by
PZ tumors.
o When benign prostatic hyperplasia (BPH)
develops, the TZ will account for an
increasing percentage of the gland volume.

20. Coronal image of the prostate illustrates the
central zone (CZ) and peripheral zone (PZ).
Note that CZ has the shape of an inverted
cone with its base oriented towards the base
of the gland and is homogeneously
hypointense as it contains more stroma than
glandular tissue. CZ is well seen in younger
patients; however age‐related expansion of
the transition zone by benign prostatic
hyperplasia (BPH) may result in compression
and displacement of the CZ leading to its poor
visibility.
oBased on location and differences in
signal intensity on T2W images, the TZ
can often be distinguished from the CZ
on MR images.
oHowever, in some patients, age‐related
expansion of the TZ by BPH may result in
compression and displacement of the CZ.
oA thin, dark rim partially surrounding
the prostate on T2W is often referred to
as the “prostate capsule.” It serves as an
important landmark for assessment of
extraprostatic extension of cancer.

21. oNerves that supply the corpora cavernosa are intimately
associated with arterial branches from the inferior vesicle artery
and accompanying veins that course posterolateral at 5 and 7
o'clock to the prostate bilaterally, and together they constitute the
neurovascular bundles.
oAt the apex and base, small nerve branches surround the
prostate periphery and penetrate through the capsule, a potential
route for extraprostatic extension (EPE) of cancer.

22. Sagittal image of the prostate shows
the urethra (U), the course of
ejaculatory duct (arrow) and the
level of verumontanum (*) where the
ejaculatory ducts merge and enter
the mid prostatic urethra.
Axial image of the apex of the
prostate, that constitutes the lower
1/3 of the prostate, shows
hypointense anterior fibromuscular
stroma (AFS) in front of the urethra
(U). Peripheral zone (PZ) makes up
most of the apex of the prostate.

23. Axial image of the prostate base, that
constitutes the upper 1/3 of the gland just
below the urinary bladder, shows the following
anatomical zones: anterior fibromuscular
stroma (AFS) containing smooth muscle, which
mixes with muscle fibers around the urethra
(U) at the bladder neck and contains no
glandular tissue, hence it is markedly
hypointense; central zone (CZ) surrounding the
ejaculatory ducts (arrows); and peripheral zone
(PZ) that covers the outer lateral and posterior
regions of the prostate.
Axial image of the midgland, that constitutes the
middle 1/3 of the prostate and includes
verumontanum in the mid prostatic urethra,
shows anterior fibromuscular stroma (AFS) and
transition zone (TZ) tissue around the urethra.
Note increasing volume of peripheral zone (PZ) in
the midgland where it occupies the outer lateral
and posterior regions of the prostate and is
homogeneously hyperintense. Arrow points to
converging ejaculatory ducts as they enter the
mid prostatic urethra at verumontanum.

24. Sagittal image of the prostate shows
measurement of maximal length of
the gland
Axial image of the prostate shows
measurements of maximal width
(transverse) and height (anterior-
posterior) of the gland
Measurements of the prostate on T2‐weighted images used for
volume assessment with the prostate ellipsoid formula (length
x width x height x 0.52).

25. Multiparametric MRI technique
oCurrently, mp-MRI is regarded as the reference standard imaging
modality for prostate cancer because a single MRI sequence cannot
adequately detect and characterize prostate cancer. The mp-MRI is
composed of
High-resolution T2WI,
DWI, and
DCEI with optional
MRSI.
oT1-weighted Imaging (T1WI) is of limited use in assessing prostate
morphology or in identifying tumor within the gland. Its main use is
in detecting post-biopsy hemorrhage.

27. Schematic diagram of the PI-RADSDCE MR time-
curve types: type 1 (progressive), type 2 (plateau), and
type 3 (wash-in and washout).

28. A 66-year-old patient, with
PSA of 19.8, Gleason 3+4 on
multiple cores, undergoing
post-biopsy staging mp-MRI.
(A) Axial T2-weighted MRI
shows a small posterior mid-
peripheral zone hyposignal
lesion; (B,C) on
multiparametric map of
apparent diffusion coefficient
(ADC) from axial diffusion-
weighted MRI, prostate
cancer shows significantly
decreased values; (D,E) axial
dynamic contrast-enhanced
imaging (DCEI) shows early
enhancement in the posterior
mid-peripheral zone; (F)
typical post-contrast wash-
in/wash-out curve of the
tumor lesion

29. A 55-year-old patient with a
PSA of 12.3, previously
diagnosed with Gleason 3+3
cancer on 12-core template
biopsy. (A) Axial T2-weighted
image shows a large
hypointense signal in right
apical peripheral zone with
capsular bulge; (B) apparent
diffusion coefficient (ADC) map
from axial diffusion-weighted
imaging (DWI) showing
hypointense signal and
restricted diffusion of the
lesion; (C,D) axial dynamic
contrast-enhanced imaging
(DCEI) showing strong early
enhancement in the right
apical peripheral zone; (E)
typical post-contrast wash-
in/wash-out curve of the tumor
lesion.

30. o In contrast to cancer in other
organs, prostate cancer presents
low signal intensity compared with
adjacent glandular tissue because
the abundant amount of water in
the normal gland demonstrates
high signal intensity on T2WI. This
signal difference between normal
and cancer tissue helps in cancer
detection in the gland-rich
peripheral zone.

31. A 55-year-old man with Gleason 7 (4 + 3)
prostate cancer. (a) Axial T2-weighted
image (T2WI) shows the normal
hyperintense T2 signal in the peripheral
zone (white arrow) from the high water
content with cancer (black arrow)
appearing as an area of low signal on
T2WI.
oOn T2W images, clinically
significant cancers in the PZ
usually appear as round or
ill‐defined hypointense focal
lesions.
oHowever, this appearance is
not specific and can be seen in
various conditions such as
prostatitis, hemorrhage,
glandular atrophy, benign
hyperplasia, biopsy related scars,
and after therapy (hormone,
ablation, etc.).

32. o As such, T2WI is considered the
dominant of all the mp-MRI sequences
for detection of cancer in the transition
zone.
Transition zone tumor. A 54-year-old
male with biopsy-confirmed
Gleason 8 prostate carcinoma. The
T2-weighted image showing a
typical “erased charcoal” (arrow)
appearance in the transition zone
o The T2W features of TZ tumors include
non‐circumscribed homogeneous,
moderately hypointense lesions (“erased
charcoal” or “smudgy fingerprint”
appearance), spiculated margins,
lenticular shape, absence of a complete
hypointense capsule, and invasion of the
urethral sphincter and anterior
fibromuscular stroma.

33. oThe high spatial resolution of
T2WI makes the sequence also the
mainstay for local staging of
disease. Low signal intensity
extension to seminal vesicles,
obliteration of the recto–prostatic
angle and extension to
neurovascular bundles are signs of
extracapsular extension (ECE) of
tumor on T2WI.
oAddition of DWI and DCE imaging
to T2WI improved the accuracy of
pre-operative detection of ECE.
Extracapsular extension of tumor. A 64-
year-old male with biopsy-confirmed
Gleason 7 (3 + 4) prostate carcinoma.
Axial T2-weighted image obtained with
the endorectal coil shows the low signal
tumor in the left peripheral zone with
minimal extension along the left
neurovascular bundle (arrow)

34.  The Gleason score is used by pathologists to grade
prostate cancers.
 If the cancer cells and their growth patterns look
very abnormal, a grade 5 is assigned. The Gleason
score is the sum of the two most prevalent patterns:
primary and secondary patterns.

35.  These 2 grades are added to yield the Gleason score.
The highest Gleason score therefore is 10.
For example, if the Gleason score is written as 3+4=7, it means
that most of the tumor is grade 3 and the second most common
or most malignant grade is 4.
 A new pathology grading system was recently proposed by
the International Society of Urological Pathology (ISUP),
dividing the relevant Gleason scores into 5 Grade Groups to
simplify prostate cancer grading (table).

39.  Assessment categories
 A combination of imaging findings (T2W, DWI,
and DCE) predicts the probability of a cancer that is
clinically significant, which is defined as the presence of
any of the following:
 Gleason score ≥7
 volume >0.5 mL
 extraprostatic extension

40. Each lesion is assigned a score from 1 to 5 indicating the likelihood of
clinically significant cancer:
PI-RADS X: component of exam technically inadequate or not performed
PI-RADS 1: very low (clinically significant cancer is highly unlikely to be
present).
PI-RADS 2: low (clinically significant cancer is unlikely to be present).
PI-RADS 3: intermediate (the presence of clinically significant cancer is
equivocal).
PI-RADS 4: high (clinically significant cancer is likely to be present).
PI-RADS 5: very high (clinically significant cancer is highly likely to be
present).
Biopsy should be considered for PI-RADS 4 or 5 lesions, but not PI-RADS 1 or 2
lesions.

41. PI‐RADS assessment for PZ on T2‐weighted imaging.

43. PI‐RADS assessment for TZ on T2‐weighted imaging.

45. PI‐RADS assessment for PZ on DWI

47. PI‐RADS assessment for TZ on DWI

49. o DCE MRI relies on fast T1-weighted sequences before, during
and after rapid intravenous (IV) administration (2–4 mL/s) of a
bolus of a gadolinium-based contrast agent to assess tumor
angiogenesis.
o During DCE MRI, tumors demonstrate early and high-
amplitude enhancement followed by rapid washout in some
cases compared with normal tissue.

50. PI‐RADS assessment for DCE MRI.

56. Multiparametric magnetic resonance imaging (mp-MRI) detects significant
prostate cancer. This 63-year-old man had a doubling of serum PSA in less than
2 years. (A) A pseudonodular mass of the anterolateral part of the left mid-
peripheral prostate with low signal on T2-weighted imaging (T2WI) is shown;
(B) this mass is associated with low signal on the apparent diffusion coefficient
(ADC) map signifying restricted diffusion; (C) focal asymmetric early
enhancement on the arterial phase of the dynamic contrast-enhanced
perfusion imaging. Targeted biopsies of this area revealed high volume
Gleason 4+3=7 cancer

57. MRSI
oAmong the sequences which comprise the mp-MRI, proton MRSI is
the least frequently used and is mostly limited to the research
setting.
oMRSI provides information about specific metabolites within
prostatic tissue such as citrate, creatine, and choline.
oNormal prostate tissue contains an abundant supply of zinc which
inhibits aconitase and produces high levels of citrate. Citrate exhibits
a unique peak on MR spectroscopy. On the other hand, in prostate
cancer down regulation of the zinc transporters causes a decrease in
zinc levels . This reduction in zinc decreases citrate levels by inducing
oxidation.

58. o Choline levels correlate with cell turnover, as seen in
prostate cancer.
o Thus, as cancers arise, citrate is expected to decline
while choline is expected to rise. This ratio of choline to
citrate is therefore an indicator of malignancy .
o On MRSI of the prostate, the dominant peaks in the
spectra are from protons in :
 Citrate (resonates at 2.6 ppm),
 Creatine (resonates at 3.0 ppm) and
 Choline compounds (resonates at 3.2 ppm).

59. oIn cancer, choline signals are elevated while
citrate signals decrease, in comparison with
benign tissue. For image interpretation, the
choline plus creatine-to-citrate ratio is often used
as a metabolic biomarker, although it is more
reliable in the peripheral zone, which has high
citrate levels.

60. Typical graphics obtained from magnetic resonance spectroscopic imaging
(MRSI). (A) Multivoxel spectroscopic imaging on the prostate; normal
prostatic tissue: (Ch + Cr)/Ci <0.5; prostate cancer: (Ch + Cr)/Ci >0.8.

61. 1. Benign prostatic hyperplasia (BPH)
o BPH consists of a mixture of stromal and glandular hyperplasia
and may appear as band‐like areas and/or encapsulated round
nodules with circumscribed margins.
o Predominantly glandular BPH nodules and cystic atrophy exhibit
moderate‐marked T2 hyperintensity and are distinguished from
malignant tumors by their signal and capsule.
o BPH nodules may be highly vascular on DCE and can demonstrate
a range of signal intensities on DWI.

68. Conclusion
oAlthough the individual sequences are useful, T2WI
in combination with two functional sequences has been
shown to provide better characterization of tumor in the
prostate. In a diagnostic meta-analysis of seven studies,
revealed a high overall sensitivity and specificity on
accuracy of mp-MRI using T2WI, DWI and DCEI.