MRI IN UROLOGY

MRI in Urology
Dept of Urology
Govt Royapettah Hospital and Kilpauk Medical College
Chennai

Moderators:
Professors:
• Prof. Dr. G. Sivasankar, M.S., M.Ch.,
• Prof. Dr. A. Senthilvel, M.S., M.Ch.,
Asst Professors:
• Dr. J. Sivabalan, M.S., M.Ch.,
• Dr. R. Bhargavi, M.S., M.Ch.,
• Dr. S. Raju, M.S., M.Ch.,
• Dr. K. Muthurathinam, M.S., M.Ch.,
• Dr. D. Tamilselvan, M.S., M.Ch.,
• Dr. K. Senthilkumar, M.S., M.Ch.
Dept of Urology, GRH and KMC, Chennai. 2

Introduction
• Magnetic resonance imaging is one of the most remarkable diagnostic
technologies available today.
• The images of the human bodies obtained by this modality are far
superior to all the other methods of imaging.
• MRI resembles C.T. equipment but working principles differ.
3
Dept of Urology, GRH and KMC, Chennai.

Magnetic Strength
• The field strength of the magnets used for MR is measured in units of
Tesla
• One Tesla is equal to 10,000 Gauss
• Magnetic field of the earth is approximately 0.5 Gauss
• MAGNETIC STRENTH USED IN MRI : 0.5 - 3.0 T (5000 – 30,000 G )
4

Principle
• The laws of electromagnetism state that a magnetic field is created
when a charged particle moves.
• The Hydrogen nucleus is the MR active nucleus used in clinical MRI.
• Other potential nuclei are phosphorus and sodium.
• Hydrogen is used because it is very abundant in the human body.
5

• The hydrogen nucleus contains one positively charged proton that
spins.
• Spinning proton has its own magnetic field with a north and south
pole of its own.
• The north/south axis of each nucleus is represented by a magnetic
moment.
6

Principle
7

Steps in Creating an MRI image
• Application of External Magnetic field
• Application of Radiofrequency Pulse
• Observing the electric signal produced
8

MRI Set UP
9

Precession
• The protons being little magnets align themselves like a compass
needle in the external magnetic field like a compass needle.
• Most of them align Parallel to the applied field and some are aligned
antiparallel.
10

Precession and Precessional Frequency
• The aligned protons move
around in a certain way like a
‘spinning top’ and this type of
movement is called PRECESSION.
• The speed of the precession is
called as PRECESSIONAL
FREQUENCY, which is directly
proportional to the external
magnetic field strength.
11

Longitudinal and Transverse Magnetisation
12

RadioFrequency Pulse
• After the application of external magnetic field, a short burst of
electro magnetic waves is applied.
• It is called a Radio Frequency Pulse or RF pulse.
• Some protons absorb the radio frequency pulse and change their
alignment in the external magnetic field.
• This change in alignment causes longitudinal magnetization to
decrease and establishes a new transversal magnetization.
13

Resonance
• The protons can pick some energy from the Radio wave only when
the frequency of the externally applied RF pulse is equal to the
protons precessional frequency.
• This phenomenon is called Resonance.
14

Pulse Cycle
It is a repeating unit, which is composed of a series of one or more RF
pulses, with a measurement of one or more MR signals.
A pulse sequence is a series of pulse cycles.
15

TR and TE
• TR (Time to Repeat) is a time interval between two successive pulse
cycles
• TE (time to echo) is the time interval from one pulse to the
measurements of MR signals
16

Relaxation
• It is the process that occurs after terminating the RF pulse.
• The physical changes that were caused by the RF pulse are reversed
back, by two processes.
17

T1 and T2 Relaxation time constants
When the RF pulse is switched off,
longitudinal magnetization increases again, this longitudinal
relaxation is described by a time constant T1 – the longitudinal
relaxation time.
Transverse magnetization decreases and disappears; this transverse
relaxation is described by time constant T2 – the transverse
relaxation time.
18

T1 Weighted Image
• T1 weighted image is the one in which the intensity contrast between
any two tissues in an image is mainly due to the T1 relaxation
properties of the tissues.
• For a T1 Weighting: Short TR & Short TE is used
19

T2 Weighted Image
• T2 Weighted image is the one in which the intensity contrast
between any two tissues in an image is mainly due to T2 relaxation
properties of the tissues.
• For a T2 weighting: Long TR & Long TE is used
20

T1 Weighted Image
• Better delineation of anatomy ( anatomical imaging).
• Simple fluid is hypointense ( black)
• Fat is hyperintense ( brighter)
• Better for characterising infiltration of disease processes into adjacent
fat plane
21

T2 Weighted Image
Bright
• Increased water (edema, tumor, infarction, inflammation, infection,
subdural collection)
• Methemoglobin (extracellular) in subacute hemorrhage
22

T2 Weighted Image
Dark
• Low proton density, calcification, fibrous tissue
• Paramagnetic substances: deoxyhemoglobin, methemoglobin
(intracellular), iron, ferritin, hemosiderin, melanin
• Protein-rich fluid
23

Contrast Agents
• Paramagnetic contrast agents can be used to modify the T1
relaxation process in tissues
• GADOLINIUM, GADOPENTETATE, GADODIAMIDE, GADOTERIDOL
• Unchanged GADOLINIUM ion is highly toxic
• It must be chelated to a harmless carrier that speeds its removal from
the body by Glomerular filtration.
• They don’t produce contrast by the themselves.
• They reduce T1 relaxation of the tissues in which they are in.
24

Gadolinium Contrast
• Non Radioactive
• Anaphylactoid reactions - 0.03 – 0.1 %
• Nephrogenic systemic fibrosis (GADODIAMIDE)
• CKD
• Severe painful condition
• Excessive fibrous tissue growth in eyes, joints, skin and internal
organs
25

MRI-Advantages
• Excellent spatial resolution, So better tissue characterization
• Direct multiplanar imaging
• No ionizing radiation – useful in children, pregnancy and follow up.
26

MRI-Disadvantages
• Claustrophobia
• Longer Procedure time
• Sedation- esp in children
• Contra indications:
• Pace makers
• Aneurysm clips & coilings
• Metallic foreign bodies in eyes
• Cochlear implants
27

MRI Prostate
• MR imaging of the prostate - available since the late 1980’s, initially
using the body coil and then in the 1990’s with an endorectal coil
• It is accepted as the best imaging modality to display the anatomical
details of the prostate
28

T1 WI- Normal Prostate
Normal prostate gland demonstrates
homogeneous intermediate to
low signal intensity.
However it has insufficient soft‐tissue
contrast resolution for visualizing the
intraprostatic anatomy or abnormality
29

T2 WI-Normal Prostate
• The zonal anatomy of the prostate gland
is best depicted on high‐resolution
T2‐weighted images
• Normal peripheral zone demonstrates a
high signal intensity
• The signal intensities in the central and
transition zones are lower than those in
the peripheral zone
• The anterior fibromuscular stroma has
low signal intensity
30

MRI in Prostate Carcinoma
• It is the most accurate non‐invasive method for staging, local extent
of prostate Ca
• It has become the definitive test for determining treatment options
(e.g. surgery vs radiotherapy)
• Development of the endorectal coil has increased the accuracy of
detection to 82% (compared to 66‐69% using the body coil)
31

MR in Prostate Cancer-Aims
1. To characterize focal abnormalities and all tissues within the gland
and detect cancer
2. To provide loco-regional staging information
32

MRI in Prostate Carcinoma
• Multi parametric MRI is being used in the identification of Prostatic
carcinoma.
• It consists of :
• T2-weighted imaging,
• diffusion imaging,
• perfusion (dynamic contrast-enhanced imaging) and
• spectroscopic imaging (Not used nowadays)
33

Advantages over Other Modalities
• It does not use ionizing radiation.
• It can obtain images in sagittal, coronal, axial, and/or oblique planes
• It provides more soft tissue contrast than other radiological
techniques
34

PIRADS
• Prostate Imaging and Reporting Archiving Data System scoring system
• It is the standardized scoring system to avoid the subjective variations
in reporting of mp-MRI.
35

PIRADS- Peripheral zone-DWI
36

PIRADS-Transitional zone-T2WI
37

PIRADS
38

T2WI
• T2-WI is the workhorse of prostate MRI. It
• Provides high spatial resolution and defines the zonal anatomy.
• The neurovascular bundles are also outlined on T2WI.
• The peripheral zone has high signal intensity on T2WI, reflecting its
higher water content, and cancer in the peripheral zone appears as an
area of lower signal.
• However, low T2 signal in the peripheral zone may also be seen in
benign abnormalities, including prostatitis, fibrosis, scar tissue, post-
biopsy hemorrhage or post-irradiation.
39

T2WI shows the normal hyperintense T2 signal in the peripheral zone
with cancer appearing as an area of low signal on T2WI. Apparent
diffusion coefficient map at the same level showing low signal from the
restricted diffusion at the site of cancer
40

Cancer in Transitional zone-T2 WI
• “Erased charcoal” appearance
• Indistinct margins of the nodule,
• Extension of low signal into peripheral zone,
• Lenticular shape,
• Extension to fibromuscular stroma and local invasion
41

Transitional zone-Erased charcoal
42

Imaging sequence
Standard sequences
• Axial T1‐weighted pelvis
• Axial T2‐weighted pelvis
• Sagital T2‐weighted pelvis
• Coronal T2‐weighted prostate
Others:
• Diffusion‐weighted imaging
• Dynamic contrast enhancement
• MR Spectroscopy of selected volumes of the prostate
43

T2WI Limitations
• Cancer and normal tissues both
have low densities in transitional
and central zone.
• Mucinous carcinoma can cause
high intensity lesion in
Peripheral zone.
• Some non cancerous causes also
can cause low signal intensity
lesions in peripheral zones.
• It includes:
biopsy-related hemorrhage
post-radiation therapy fibrosis
changes after hormonal ablation.
44

MRI Prostate-Uses
• Cancer detection
• Staging
• MR guided prostate biopsy
• MR guided cancer treatment
45

Extracapsular extension in MRI Prostate
• Irregular bulging of the prostatic outline
• Breach of the capsule with extracapsular spread
• Asymmetry of the neurovascular bundles (NVB )
• Loss of the rectoprostatic angle (RPA )
46

T2-weighted sagittal MR image, the fat plane between the
seminal vesicle and the urinary bladder is obliterated
47

Breach of the capsule with direct tumor extension and
involvement of the neurovascular bundle 48

T2- weighted axial and sagittal MR images demonstrate
diffuse tumor invasion of the prostate gland with direct
tumor (T) extension to anterior rectal wall (white arrow)
49

Asymmetry of the neurovascular bundles
50

Obliteration of the rectoprostatic angle
51

Functional MRI in Prostate
• Magnetic resonance spectroscopic imaging (MRSI)
- provide metabolic information
• Diffusion-weighted MRI (DW-MRI)
- allows in vivo measurement of diffusion
coefficients of biological tissues
• Dynamic contrast-enhanced MRI (DCE-MRI)
- enables noninvasive visualization of tissue vascularity
52

MR Spectroscopy of Prostate
• This technique produces an array of MR spectra showing the relative
concentrations of metabolites within voxels
• The metabolic data from MRSI are superimposed onto MR images to
help identify and localize Prostate Carcinoma.
53

MRS Prostate Principle
• Based on cellular composition of disease process (esp malignancy)
• Citrate is normally found in prostate
• Choline present is present bound to cell membrane
• Malignancy because of high cell turnover→ breakdown products of
cell membrane → choline is increased
• Malignant cells→ reduced synthesis of citrate
54

• The metabolites measured by MRSI are citrate, creatine, choline, and
polyamines.
• Prostatic Carcinoma is identified on MRSI by an increased ratio of
choline plus polyamines plus creatine to citrate.
• The ratio of choline and creatine to citrate in normally healthy
prostatic tissue has been established as 0.22 +/‐ 0.13
55

(a) MRSI grid superimposed on transverse T2-weighted MRI
(b) low signal intensity in the left peripheral zone MRSI grid
showing all spectra with voxel suspicious for cancer
MRS Prostate
56

Prostate Spectroscopy
57

Diffusion Weighted MRI
• The motion of water molecules in extra- and intracellular spaces
contributes to the net water displacement measured by DW-MRI
• DW-MRI yields
qualitative
quantitative information
• Reflecting tissue cellularity and cell membrane integrity and thus the
morphologic information obtained with conventional MRI
58

• The degree of H2O diffusion in biologic tissue is inversely correlated
to the tissue cellularity and the integrity of cell membranes
• Motion of water molecules is more restricted in tissues with a high
cellular density and intact cell membranes
59

DWI-Method
• 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.
• Tumors demonstrate early and high-amplitude enhancement
followed by rapid washout in some cases compared with normal
tissue.
60

• Qualitative (visual) assessment of relative tissue signal attenuation at
DW-MRI is used for tumor detection and tumor characterization
• The quantitative analysis of DWMRI is achieved by calculation of the
apparent diffusion coefficient (ADC)
• The ADC is calculated for each pixel of the image and is displayed as a
parametric map (ADC map)
61

DWI shows decreased diffusion of water molecules
in this region
62

T2-weighted axial image acquired without endorectal coil shows
confluent area of hypointense signal in the left peripheral zone
(arrows)
The corresponding diffusion-weighted image shows restricted
diffusion in the same area, most consistent with prostate cancer
63

Dynamic Contrast Enhanced MRI
• DCE-MRI is based on repetitive acquisition of sequential images
during the passage of a contrast agent within a tissue of interest
• Based on tumor angiogenesis
• Malignancy → Rapid wash in and rapid wash out
• DCE-MRI enables the visualization of lesion vasculature and
permeability
• plays a role in tumor detection and therapy monitoring
64

DCE- RAPID WASH IN & WASHOUT
65

MR Perfusion Imaging
• Based on micro vascular permeability
• Malignant tumor → high vascular density and porous
microvasculature
• MR perfusion is increased in malignancy
66

MR PERFUSION MAP - PROSTATE
67

MRI in Kidneys and Ureters
68

MRI Normal Kidney
• MRI permits separate visualization of renal cortex and medulla on
both T1 and T2 weighted images
• On T1WI, renal cortex appears brighter than medulla.
• Calyces are not generally well visualized on MRI.
• Visualisation of cortex, medulla and renal pelvis enhanced by contrast
agents like Gd-DTPA.
• Renal sinus fat is observed as high intensity structure in both T1 and
T2 weighted images.
• Paraaortic lymphnodes are visualized if they are >1cm.
69

MR Urography-Use cases
• Patients with a history of iodinated contrast allergy
• Patients with a compromised renal function
• Women of child-bearing age
• Patients being considered for nephron-sparing surgery
• Surveillance in patients at high risk for RCC
• Patients with a prior history of renal neoplasia who require
surveillance
70

MR Urography-techniques
Most common MR urographic techniques for displaying the urinary
tract can be divided into two categories:
1. Static-fluid MR urography (T2- weighted MR urography)
2. Excretory MR urography (T1-weighted MR urography)
71

Static Fluid MR Urography
• Static-fluid MR urography makes use of heavily T2- weighted
sequences to image the urinary tract as a static collection of fluid
• Can be repeated sequentially to better demonstrate the ureters in
their entirety and to confirm the presence of fixed stenosis
• Most successful in patients with dilated or obstructed collecting
systems
72

Static fluid MR urography
73

Excretory MR Urogaphy
• Performed during the excretory phase of enhancement after i.v
administration of gadolinium-based contrast medium
• The patient must have sufficient renal function to allow the excretion
and even distribution.
• Diuretic administration can better demonstrate nondilated systems
74

Excretory MR Urography
75

Calculi appearing as signal voids in MR Urography
76

MR Urography- Limitations
• Relative insensitivity for renal calculi
• Relatively long imaging times
• Lower spatial resolution compared with CT and radiography
77

MRI Protocols in Renal Neoplasms
• T2 HASTE
• It is rapidly acquired.
• It provides good anatomy overview.
• Fluid-containing structures are bright.
• T1 gradient echo
• Fat is bright (AML and myelolipomas are conspicuous).
• Complex fluid (eg, hemorrhage) is also bright.
• Adenopathy is easily visualized.
• T1 gradient echo with fat saturation
• Fat-containing structures become dark.
• Complex fluid remains bright
78

• T1 gradient echo 3D dynamic sequence (after intravenous
administration of gadolinium)
• Enhancement within any portions of a mass or cyst is consistent with a
neoplasm
• Vessels enhance
• MR angiography and MR venography
• Vessels enhance, allowing for detection of renal vein and IVC involvement
• Vascular anatomy can be mapped
79

RCC in MRI
• Imaging characteristics of tumor correlate well with gross pathology
• T1WI is usually isointense (same signal as kidney) or hypointense
(dark), but highly variable because of signal from necrosis or
hemorrhage
• T2WI is variable, but usually slightly hyperintense (bright)
80

T1-weighted axial MRI shows
hypointense (dark) right midpole renal mass
T2-weighted axial image shows
hyperintense (bright) renal mass
81

T1-weighted coronal MRI shows
hypointense right midpole renal mass
T1-weighted postgadolinium coronal
image shows enhancing renal mass
82

• With gadolinium, tumor enhances, but less than normal renal
parenchyma
• Enhancement represents viable tumor
• Lack of enhancement suggests necrosis or cystic formation
83

Diffusion Weighted Imaging
• Traditionally been used in imaging stroke victims, as it is very sensitive
in detecting acute ischemia
• Studies showing good correlation between GFR and ADC (Apparent
Diffusion Coefficient) values, highlighting the potential role for
evaluating renal dysfunction in native kidneys
84

Diffusion Weighted Imaging Kidney
85

MR Renography
• It is one application of dynamic contrast-enhanced (DCE) MRI,
specifically, the use of Gd-based contrast agents for measuring GFR.
• Most Gd chelates have favorable renal properties: freely filtered at
the glomeruli without tubular secretion or resorption.
• Transit of the bolus of contrast from the artery to the renal cortex
estimate renal perfusion;
• Transit from cortex to medulla reflects glomerular filtration; and
finally from the medulla into the collecting system reflects tubular
function.
86

BOLD MRI
• Blood Oxygen Level Dependent MRI depends on T2 relaxation time.
• Can be used for noninvasive but direct measurement of renal
oxygenation
• Exploits the paramagnetic effect of deoxyhemoglobin for acquisition
of images sensitive to local oxygen concentration
• Application in the context of renal artery stenosis, renal allograft
dysfunction, diabetic nephropathy
87

MRI Penis and Scrotum
• Traditionally, owing to its low cost, ready availability, and proved
diagnostic accuracy, ultrasonography (US) has been the primary
modality for imaging of the penis and scrotum.
USG-Limitations:
• Small field of view
• Operator dependence
• Lack of tissue characterisation
88

MRI Normal Penis anatomy
The corpus spongiosum and the corpora cavernosa
• hyperintense onT2-weighted images
• intermediate signal intensity onT1-weighted images.
The tunica albuginea appears hypointense on bothT1- andT2-weighted
images.
The intravenous administration of gadolinium-based contrast agents,
both the corpus spongiosumand corpora cavernosa enhance.
89

T2-weighted MR image
• showing the corpora cavernosa
and corpus spongiosum with
high signal intensity (black
arrow) and the surrounding
tunica albuginea with low signal
intensity (white arrow).
90

• Penile trauma - Sagittal T2-
weighted MR image shows a
focal region of low signal
intensity in the
left corpus cavernosum (black
arrow) without disruption of
the T1- and T2-hypointense
tunica albuginea fibrous band
(white arrow), findings that
are consistent with penile
contusion
91

• Sagittal T2-weighted MR image
showing - focal disruption of the
hypointense tunica albuginea of the
left corpus cavernosum (black
arrow) associated with a large
hematocele (white arrow)
92

Normal penile anatomy.
• Sagittal T2- weighted MR
images showing the corpora
cavernosa and corpus
spongiosum with high signal
intensity (black arrow) and
the surrounding tunica
albuginea with low signal
intensity (white arrow).
93

Penile carcinoma
• Can be useful in the T staging
of penile carcinoma.
• T2 WI shows heterogeneous
intense lesion in the shaft of
the penis.
94

Penile Carcinoma-LN MRI
• Allows the characterization of lymphnodes to detect nodal
micrometastasis.
• Performed with Ferumoxtran 10, consists of USPIO Ultra small
paramagnetic iron oxide particles.
• Normal lymphnodes contain macrophages, which engulf the iron
oxide nanoparticles –appear dark
• Malignant lymph nodes lack the phagocytic cells needed to take up
the nanoparticles-appear bright.
95

LN MRI
96

MRI Penis
• Peyronies disease showing
thickening of tunica
albugenia plaque.
97

MRI Scrotum
• USG has proved inconclusive in up to 5% of cases of suspected scrotal
disease, with MR imaging providing additional value in many of
scrotal diseases
• The performance of MR imaging following inconclusive USG is cost
effective.
• Specifically, MR imaging can help differentiate between benign and
malignant lesions seen at USG.
98

Normal Scrotal Anatomy
• Coronal T2-weighted MR image
showing homogeneously
hyperintense testes (black
arrow) beneath the more
hypointense epididymis
(arrowhead). The scrotal sac
(white arrow) is hypointense, a
normal finding on both T1- and
T2-weighted images.
99

• Coronal T2-weighted MR
image showing a large,
complex fluid collection with
classic hypointense signal in
the scrotum (arrow), a
finding that is consistent with
blood products
100

MRI –Undescended Testis
101

Thank you
102

MRI IN UROLOGY

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