MRI Atlas of Renal Pathology - PowerPoint PPT Presentation

Loading...

PPT – MRI Atlas of Renal Pathology PowerPoint presentation | free to download - id: 49d8e9-OGI2Y



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

MRI Atlas of Renal Pathology

Description:

MRI Atlas of Renal Pathology Mary Kitazono Patrick M Colletti MD University of Southern California Keck School of Medicine Start kitazono_at_usc.edu, colletti_at_usc.edu – PowerPoint PPT presentation

Number of Views:505
Avg rating:3.0/5.0
Slides: 123
Provided by: Prince82
Learn more at: http://rsna2004.rsna.org
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: MRI Atlas of Renal Pathology


1
MRI Atlas of Renal Pathology
  • Mary Kitazono
  • Patrick M Colletti MD

University of Southern California Keck School of
Medicine
Start
kitazono_at_usc.edu, colletti_at_usc.edu
2
Table of Contents
  • Renal MRI Technical Considerations
  • Indications for Renal MRI
  • MRI Atlas of Normal Renal Anatomy
  • MRI Atlas of Renal Pathology
  • Vascular Disorders
  • Diseases of the Renal Parenchyma
  • Obstructive Uropathy
  • References
  • MRI Tutorial
  • Proton MR Tutorial
  • Pulse Sequences
  • MR Angiography
  • MRI Imaging Strategies

3
Renal MRI Technical Considerations
  • Select a Pulse Sequence and Protocol
  • Set Parameters
  • TR (repetition time) determines T1 and
    T2-weighting
  • TE (echo time) determines T2-weighting
  • Flip angle determines T1-weighting in gradient
    echo sequences
  • Maximize image quality
  • Voxel size smaller improved resolution
  • Acquisition time faster better temporal
    resolution
  • Reduce Motion Artifacts
  • Paramagnetic Contrast Enhancement
  • Renal MR Angiography
  • MR Urography

4
Basic Renal Imaging Protocol
  • Localizer HASTE/ssFSE/ssTSE
  • Coronal plane, 8 mm slices, breath held
  • In-phase and opposed-phase T1 Dual echo spoiled
    gradient echo
  • To characterize fat-containing lesions axial
    plane, 6-8 mm slices, breath held
  • Include a precontrast fat-suppressed T1 to
    differentiate fat from blood
  • Fat-suppressed T2 Fast/TurboSE or GE
  • To characterize lesion, lymphadenopathy, and
    fluid axial plane, 6-8 mm slices, respiratory
    triggering
  • Dynamic Gd-enhanced T1 2D or 3D spoiled GE
  • Contrast enhanced MRA to characterize
    vascularity axial plane, 6-8 mm slices, breath
    held
  • Non-contrast MRA
  • To evaluate renal vein and IVC for patients with
    renal cell carcinoma
  • MR Urography
  • To evaluate the collecting system

5
Motion Artifact Reduction
  • Causes of physiologic motion artifact
  • respiration
  • cardiovascular pulsation
  • bowel peristalsis
  • Due to the posterior location of the kidneys,
    there is much less artifact as compared to liver
    imaging, however various methods for reducing
    motion artifact can be employed.

6
Motion Artifact Reduction
  • Ways to reduce motion artifact
  • antero-posterior phase encoding for axial imaging
    (since artifacts develop in the direction of the
    phase encoding)
  • cranio-caudal phase encoding combined with
    foldover suppression for coronal imaging
  • breath-holding, with or without retrospective
    averaging of individual breath-holds
  • single-shot and fast imaging pulse sequences
  • fat-suppression techniques
  • intermittent sampling of data using respiratory
    ordered-phase encoding, respiratory gating, or
    respiratory triggering (though not usually
    required)
  • wrapping an elastic garment around the patients
    abdomen to minimize anatomic movement during
    respiration

7
Gadolinium
  • Chelates of Gadolinium (e.g. Gd-DTPA)
  • commonly used paramagnetic contrast agents
  • completely filtered in the kidney, making it
    useful for examining excretory kinetics
  • provides excellent corticomedullary delineation
    in the early perfusion phase (10-20 seconds after
    injection) and in the early excretory phase
    (50-90 seconds after injection)
  • safe (approved by the FDA)
  • MR imaging with Gd-DTPA is the appropriate choice
    for all children and women of childbearing age,
    patients with iodinated contrast allergy, renal
    insufficiency and solitary kidney, and for
    following the progression of disease over time.

8
Paramagnetic Contrast Enhancement
  • How they work Paramagnetic contrast agents have
    unpaired electrons, which create small local
    magnetic fields in the surrounding tissue
  • Main effect proton relaxation enhancement, or
    shortening of the T1 relaxation time in the
    surrounding tissues, increasing the signal
    intensity and tissue contrast
  • Requirements blood flow and a compromised
    capillary basement membrane
  • Use to assess the function of renal vessels and
    to enhance lesions for diagnosis, especially
    vascularized tumors

9
Renal MR Angiography
  • Advantages of MRA over conventional angiography
  • Gadolinium chelates are safe, even for patients
    with renal insufficiency, whereas iodinated
    contrast agent can cause allergic reactions and
    nephrotoxicity.
  • MRA is a non-invasive procedure, not requiring
    local anesthesia or recovery time.
  • 3D MRA allows a more accurate assessment of
    lesions, particularly atheromatous plaques.
  • MRA can usually demonstrate accessory renal
    vessels.
  • MRA can elucidate the significance of stenosis by
    depicting the presence of poststenotic
    dilatation, delayed renal enhancement, and/or
    reduced renal mass.
  • Incidental renal pathology can be detected.
  • Phase contrast flow MRA can provide a
    quantitative measurement of renal perfusion.

10
Renal MR Angiography
  • Disadvantages of MRA
  • MRA requires precise timing and calculation of
    the rate of contrast flow. Inaccuracies can
    result in signal loss if image acquisition begins
    too late, or venous enhancement, instead of
    arterial enhancement, if acquisition is begun too
    early.
  • MRA requires the patient to hold his or her
    breath and remain motionless for a considerable
    amount of time.
  • As with all forms of MR imaging, MRA can not be
    performed on patients with pace-makers or
    implanted ferromagnetic devices.

11
MR Urography
  • Clinical Application
  • to evaluate ureteral obstruction and congenital
    urinary tract abnormalities

12
MR Urography
  • Static MR Urography
  • Technique Heavily T2-weighted sequence similar
    to MRCP
  • Works best for dilated collecting systems
  • Can even be used in patients with severe renal
    insufficiency
  • No imaging delay or IV contrast necessary, but
    overlapping fluid-filled structures can interfere
  • Tip imaging nondilated ureters can be enhanced
    by hydrating the patient and administed a low
    dose of furosemide before the exam
  • Excretory MR Urography
  • Technique T1-weighted 3D gradient echo sequence
    after IV contrast administration
  • Can demonstrate nondilated as well as dilated
    ureters
  • No interference by overlapping fluid-filled
    structures
  • Cannot be used in patients with severe renal
    insufficiency

13
Indication for Renal MRI
  • Detection, localization, and characterization of
    renal masses (due to its multiplanar capability)
  • Staging renal cell carcinoma
  • Detection and differentiation between renal
    cysts, hematomas and angiomyolipomas
  • Assessment of kidney function using dynamic
    imaging
  • Visualization of the renal arteries using MR
    Angiography
  • Preoperative planning and postoperative evaluation

14
Renal Cysts
  • The Bosniak classification system, which is based
    on imaging findings, can be used to differentiate
    benign renal cysts from angiomyolipomas and renal
    cell carcinomas

15
Staging Renal Cell Carcinoma
  • MRI is the imaging modality of choice for staging
    renal cell carcinoma
  • multiplanar capability
  • superior soft tissue contrast
  • ability to depict tumor extension and invasion
  • ability to detect enlarged lymph nodes

16
Renal Transplantation
  • MRI is useful for both preoperative planning and
    post-transplant evaluation of the caliber of the
    collecting system and vasculature
  • Peritransplant fluid collections, which may cause
    urinary tract obstruction, or regions of
    infarction (best seen with contrast) can be
    detected in the postoperative period

17
Utility of Dynamic Contrast-Enhanced MRI
  • In addition to providing exceptional anatomical
    detail, dynamic contrast-enhanced MR can provide
    a wealth of information about renal function
    including perfusion and glomerular filtration
    rates, giving MR imaging a clear advantage over
    real time ultrasonography and radionuclide
    renography.

Excretory Function
Spatial Resolution
Blood Flow
Real time ultrasonography
with color doppler
Radionuclide renography
Dynamic contrast-enhanced functional MRI
18
Normal Renal Anatomy
T1-Weighted Image
Kidneys are surrounded by high-signal
retroperitoneal fat, which is contained by the
low-signal perirenal fascia
Liver
Spleen
T2-Weighted Image
19
Normal Renal Anatomy
  • T1- weighted images allow corticomedullary
    differentiation between the intermediate-signal
    cortex and the low-signal medullary pyramids
  • The absence of a distinct corticomedullary
    differentiation on T1-weighted images is a
    sensitive, though nonspecific, indication of
    renal parenchymal disease

20
Normal Renal Anatomy
T1-Weighted Image
T2-Weighted Image
  • The renal pelvis, calyces, and infundibuli can
    normally be seen because of their water content,
    appearing as hypointense on T1-weighted images
    and hyperintense on T2-weighted images
  • Low-signal ureters extend obliquely, inferiorly,
    and medially

21
Variant Anatomy Pancake kidney
Movie
22
Normal Renal Anatomy
a
  • This MR angiogram demonstrates the renal arteries
    () extending from the abdominal aorta (a) in the
    axial oblique (top) and coronal views (bottom).

a
a
  • Renal vessels are linear or tortuous areas of
    signal void
  • Renal arteries extend horizontally from the aorta
    to the kidneys renal veins extend obliquely
    towards the IVC

23
Vascular Disorders that cause Renal Pathology
  • Pre-renal vascular disorders
  • Aortic dissection
  • Arteritis (ie Takayasu Arteritis)
  • Renal artery stenosis
  • Renal artery aneurysm
  • Renal vascular disorders
  • Renal AVM
  • Polyarteritis nodosa
  • Hematomas
  • Post-renal vascular disorders
  • Renal vein or IVC thrombosis

24
Aortic Dissection
First Pass
Second Pass
Delayed
25
Takayasu Arteritis
  • Takayasu arteritis is a granulomatous vasculitis
    of medium and large-sized arteries
  • Classic clinical syndrome ocular disturbances
    and marked weakening of the pulse in the upper
    extremities (pulseless disease) due to fibrous
    thickening of the aortic arch and narrowing of
    the great vessels arising in the arch
  • One third of cases also have involvement of the
    remainder of the aorta and its branches,
    including the renal arteries

26
Renal Artery Stenosis
  • Best visualized with 3D contrast enhanced MRA
  • Proximal lesions are the easiest to visualize
  • Post-stenotic dilatation
  • Small, smooth kidney
  • Arterial collaterals occasionally noted

27
Renal Artery Stenosis
28
25 y/o, 8 weeks pregnant, BP 220/140
fetus
29
Renal Artery Aneurysm
  • Classified morphologically as saccular or
    fusiform
  • Annular calcification is common, especially in
    atherosclerotic aneurysms
  • A large aneurysm may produce a concave deformity
    on the adjacent pelvocalyceal system
  • Occasionally an aneurysm appears as a soft tissue
    mass accentuated by surrounding sinus fat
  • Rapid contrast enhancement, with delayed washout
    of the aneurysm
  • Look for pulsation artifact

Calcified Renal Artery Aneurysm
30
Renal AVM
  • AVM usually occurs in the medulla and may cause a
    mass effect on the collecting system
  • Peripheral, curvilinear calcification may be
    present in a cavernous AVM
  • An enlarged feeding artery and draining vein may
    be seen
  • The entire mass enhances with contrast

31
Renal AVM
46 y/o man with hematuria. There is a large left
upper pole AVM with massive IVC dilatation
32
Polyarteritis Nodosa
  • Polyarteritis nodosa is a systemic vasculitis
    resulting from non-infectious transmural
    necrotizing inflammation of small or medium-sized
    muscular arteries
  • Only the classic form, in which
    intermediate-sized arteries (the arcuate
    arteries) are affected, is seen in the kidneys
  • It often results in irregular arterial dilation,
    nodularity, obstruction, and less commonly,
    infarction

33
Polyarteritis Nodosa
infarcts
  • Multiple aneurysms in the arcuate arteries
  • The aneurysms are 2 mm- 3mm and sharply defined
  • Arterial involvement is focal, random, and
    episodic
  • Infarcts are also common
  • Because small vessels are spared,
    glomerulonephritis is not seen

34
Polyarteritis Nodosa
  • Although the kidney is the organ that is most
    commonly involved, polyarteritis nodosa (PAN) is
    a systemic disease that can infect any organ or
    system, including the central nervous system as
    shown below

PAN in the brain (a)
a
PAN in the spinal cord (b, c, d)
b
c
d
35
Chronic Subcapsular Hematoma
  • Homogenous collection of hypodense fluid (a) that
    is bright on T1 (b, c) and T2 images (d)

36
Renal Vein Tumor Thrombosis
  • T1-weighted MR images or MRA are best for
    depicting renal vein thrombosis

37
Diseases of the Renal Parenchyma
  • Introduction
  • Glomerular Diseases
  • Glomerulonephritis
  • Glomerular lesions associated with systemic
    disease
  • Tubular and Interstitial Diseases
  • Acute Tubular Necrosis
  • Tubulointerstitial Nephritis
  • Acute and Chronic Pyelonephritis
  • Cystic Diseases
  • Neoplasms
  • Angiomyolipoma
  • Renal cell carcinoma
  • Wilms Tumor

38
Imaging the Renal Parenchyma
  • The renal parenchyma is often evaluated using a
    breath-hold fat suppressed T1-weighted spoiled
    GRE sequence in the axial plane, performed before
    and approximately 3-5 minutes after contrast
    administration.
  • The coronal plane is particularly useful in
    evaluating lesions at the poles of the kidneys as
    well as lesions that extend outside the renal
    parenchyma.
  • To characterize cystic lesions, a breath-hold
    T2-weighted half-Fourier single-shot turbo spin
    echo sequence in the coronal plane is often
    performed. Gadolinium enhancement and fat
    suppression methods can be used to further
    characterize the cystic components.

39
Irregular Renal Contour
  • The renal capsule is normally smooth. There are
    many causes of an irregular renal contour

3. Papillary necrosis
40
Renal Scar
  • Differential Diagnosis
  • Unilateral
  • Reflux nephropathy
  • Previous renal surgery
  • Bilateral
  • With Normal Calyces
  • Renal Infarcts
  • With Abnormal Calyces
  • Analgesic nephropathy
  • Reflux nephropathy

Chronic pyelonephritis
41
Renal Scar
  • Differential Diagnosis
  • Unilateral
  • Reflux nephropathy
  • Previous renal surgery
  • Bilateral
  • With Normal Calyces
  • Renal Infarcts
  • With Abnormal Calyces
  • Analgesic nephropathy
  • Reflux nephropathy

c
c
Cortical infarcts
42
Glomerulonephritis
  • Acute glomerulonephritis nonspecific, dense
    collection of inflammatory edema
  • Chronic glomerulonephritis
  • marked, symmetric reduction in the size of both
    kidneys
  • smooth contours with normal calyces and papillae
  • abundant peripelvic fat
  • calcification of the renal cortex may be seen

Chronic Glomerulonephritis with iron loading
43
Siderotic Nodules
  • Iron overload caused by genetic hemochromatosis
    or secondary hemochromatosis can result in the
    deposition of iron deposits in the kidneys and,
    if severe, the formation of siderotic nodules.

44
Myoglobinuria
  • Coronal T1-weighted images in a patient with iron
    overload. Note the low signal renal parenchyma
    and loss of the corticomedullary distinction due
    to the very short longitudinal relaxation times
    of the iron in myoglobin.

(b) postcontrast administration note the
medullary enhancement
(a) precontrast
45
Acute Tubular Necrosis
  • Acute, reversible renal failure due to severe
    ischemia or toxin exposure
  • Clinical symptoms include oliguria (or anuria)
    and proteinuria
  • Both kidneys are smooth and globally enlarged due
    to interstitial edema

46
Acute Tubular Necrosis
  • Immediate contrast enhancement following an
    intravenous bolus injection of Gd-DTPA
  • Contrast enhancement persists (often longer than
    24 hours), with little opacification of the
    pelvocalyceal system due to tubular blockage by
    debris

A T1-weighted GE sequence depicts persistent
contrast enhancement characteristic of ATN
47
Pyelonephritis
  • Acute Pyelonephritis
  • Characteristic features renal enlargement,
    increased water content, fascial thickening, and
    striated wedge-shaped enhancement
  • T1 loss of corticomedullary distinction and dark
    striations
  • T2 high signal intensity perinephric fluid
  • Emphysematous Pyelonephritis air within
    the renal parenchyma appears as tiny focal areas
    of markedly decreased signal on both T1- and T2-
    weighted images
  • Chronic Pyelonephritis calyceal
    dilatation, focal loss, and cortical attenuation

Xanthogranulomatous pyelonephritis- note
low-signal intensity striations
48
Xanthogranulomatous Pyelonephritis
  • Chronic suppurative bacterial infection in the
    collecting system due to a partial obstruction
  • Calculi, especially staghorn calculi composed of
    struvite, are seen in the pelvis in 75
  • Characteristic MR findings
  • low-signal intensity striations
  • renal fascia thickening
  • scarred pelvis
  • dilated calyces
  • chronic inflammation
  • Extra-renal extension of the inflammatory process
    is common

49
Xanthogranulomatous Pyelonephritis
a
50
Xanthogranulomatous Pyelonephritis
pre-contrast
  • Marked enhancement is seen surrounding the
    dilated calyces following IV contrast
    administration (caused by the inflammatory
    infiltrate).
  • (a) pre-contrast (b, c, d) post-contrast

a
b
c
d
51
Cystic Kidney Diseases
  • Simple Renal Cysts
  • thin, imperceptible wall that forms an acute
    angle with the rest of the renal parenchyma
    (beak sign)
  • nonenhancing
  • sharp margin
  • calcification, if present, must be thin, linear,
    and confined to the wall (Bosniak Category I or
    II cysts only)
  • Simple cysts have a homogenous signal of similar
    intensity as the nearby CSF (dark on T1-weighted
    images, and bright on T2-weighted images)
  • Hemorrhagic cysts range from very dark to bright
    on both T1 and T2-weighted images
  • Polycystic Kidney Disease
  • Medullary Cystic Disease
  • Acquired Cystic Disease
  • Cystic Neoplasm

52
Simple Renal Cyst
B
A
A
(A) T1-weighted image (B) Proton density
image (C) T2-weighted image
C
C
53
Renal Cysts
  • The Bosniak classification system, which is based
    on imaging findings, can be used to differentiate
    benign renal cysts from angiomyolipomas and renal
    cell carcinomas

54
Cystic Kidney Diseases
  • Simple Renal Cysts
  • Polycystic Kidney Disease
  • multiple expanding cysts that may massively
    enlarge both kidneys
  • autosomal dominant disorder seen in adults is
    most common autosomal recessive form seen in
    children is rare
  • cysts can be serous or hemorrhagic
  • expanding cysts ultimately destroy the renal
    parenchyma, resulting in chronic renal failure
  • Medullary Cystic Disease
  • Acquired Cystic Disease
  • Cystic Neoplasm

55
Adult Polycystic Kidney Disease
Note the enormous kidneys filled with both serous
and hemorrhagic cysts
56
Polycystic Kidney Disease
Biliary obstructing stones Polycystic kidney and
liver cysts
57
Polycystic Kidney Disease
MRCP with biliary obstructing stones Polycystic
kidneys and liver cysts
Movie
58
Acquired Cystic Disease
  • This patient has Acquired Cystic Disease
    related to prolonged dialysis

59
Cystic Kidney Diseases
  • Simple Renal Cysts
  • Polycystic Kidney Disease
  • Medullary Cystic Disease
  • Acquired Cystic Disease
  • Cystic Neoplasm
  • thickened walls
  • nodular calcification
  • irregular borders
  • non-uniform signal

60
Multicystic Dysplastic Kidney
  • Seven percent of patients with Acquired Cystic
    Disease develop renal cell carcinoma in the walls
    of these cysts after 10 years of dialysis

61
Benign Neoplasms
  • Renal Papillary Adenoma
  • small, incidental adenomas arising from the renal
    tubules
  • Renal Fibroma
  • small foci of collagenous tissue found within the
    pyramids
  • Renal Oncocytoma
  • appears as a well-encapsulated area of uniform
    signal (hypointense on T1, variable on T2) that
    may become very large (up to 12 cm)
  • frequently shows a central star-shaped scar or
    area of necrosis
  • Angiomyolipoma
  • benign, unifocal, expanding mass composed of an
    abundance of fat, smooth muscle, and
    neovascularity with a tendency to form aneurysms
  • occurs in a bilateral, multifocal form in
    patients with tuberous sclerosis

62
Angiomyolipoma
  • most are clinically silent and found
    incidentally, but they can become large and
    project into the perirenal space, forming a
    palpable mass
  • MRI is the imaging modality of choice in
    assessing these lesions due to the importance of
    tissue composition for diagnosis. A
    fat-containing renal tumor is highly specifc for
    angiomyolipoma.

63
Angiomyolipoma
CT w/contrast
T1-MR w/gad
  • Methods for diagnosis
  • Fat within the tumor is bright on
    non-fat-suppressed T1-weighted images and dark on
    fat-suppressed images. In contrast, focal
    hemorrhage appears bright regardless of fat
    suppression.
  • use chemical-shift imaging techniques
    angiomyolipomas show the characteristic India ink
    artifact (a rim of low signal intensity at the
    interface between the tumor and renal parenchyma)
    on T1 -weighted out-of-phase images.
  • Contrast enhancement is heterogenous and spares
    fatty areas.

64
Malignant Neoplasms
  • Wilms Tumor
  • occurs in children, usually between the ages of 2
    and 5
  • usually appears as a large, solitary,
    well-circumscribed mass with occasional foci of
    hemorrhage, cyst formation, and necrosis
  • Renal Cell Carcinoma
  • most characteristic finding spherical mass of
    signal intensity different from adjacent normal
    renal parenchyma due to frequent hemorrhage and
    necrosis
  • commonly arise in the poles of the kidney
  • clear cell type is unifocal and large (3 to 15 cm
    in diameter)
  • papillary type is usually bilateral and
    multifocal

65
Wilms Tumor
  • this large tumor may markedly displace the entire
    kidney
  • a mixture of attenuation values is seen, due to
    the combination of blastemic, stromal, and
    epithelial tissue with occasional foci of
    hemorrhage and necrosis
  • usually demonstrates moderate vascularity

66
Renal Cell Carcinoma
  • MRI features
  • Spherical shape
  • Fails criteria of a simple cyst (thickened,
    irregular walls with significant septation and
    non-peripheral calcification)
  • Lacks internal fat
  • Enhances with contrast

67
Renal Cell Carcinoma
  • The diagnosis of renal cell carcinoma relies on
    contrast enhancement. Solid malignant tumors may
    immediately enhance in density to the level of
    the surrounding normal renal parenchyma, but the
    density quickly decreases. Foci of old
    hemorrhage, necrosis, or cyst formation do not
    enhance and maintain a low signal intensity.

68
Renal Cell Carcinoma
T2
T1
  • T1-weighted images regions of necrosis have
    decreased signal while regions of recent
    hemorrhage have increased signal intensity due to
    the paramagnetic effect of methemoglobin
  • T2-weighted images heterogeneous, hyperintense
    mass

69
Renal Cell Carcinoma
thick, irregular border
non-peripheral calcification
  • all sequences show an alteration of renal contour
    with an irregular, thickened, or nodular border
  • non-peripheral calcification (approximately 90
    of all masses containing calcium in a
    non-peripheral location are carcinomas, whereas a
    thin rim of peripheral calcification is
    characteristic of a cyst)
  • ureteral notching, due to the development of
    collateral veins following tumor invasion of the
    main renal vein, may also be seen

70
Renal Cell Carcinoma
MRA
early
late
  • Most renal cell carcinomas are very vascular,
    showing an enlarged renal artery, chaotically
    distributed intrarenal vessels, small aneurysms,
    arteriovenous fistulas, and lakes of contrast
    material that clear slowly
  • dilated capsular arteries and veins may be seen
    within the perirenal fat

71
Tumor Renal Vein Invasion
  • T1-weighted MR images or MRA are best for
    depicting renal vein thrombosis

72
Renal Cell Cancer IVC Invasion
  • Both renal cell carcinoma and Wilms tumor have a
    tendency to invade the renal vein, the IVC, and
    even the right atrium

t
t tumor i IVC a aorta
i
t
a
i
t
73
Renal Cell Cancer Invasion of IVC Level 2
  • filling defects in the renal vein or IVC can be
    either due to metastatic spread of the tumor or a
    propagated tumor thrombus
  • linear striated capillary staining of tumor in
    the renal vein is occasionally seen

74
Renal Cell Cancer Invasion of IVC Level 3
Movie
75
Staging Renal Cell Carcinoma
  • MRI is the imaging modality of choice for staging
    renal cell carcinoma
  • multiplanar capability
  • superior soft tissue contrast
  • ability to depict tumor extension and invasion
  • ability to detect enlarged lymph nodes

76
Obstructive Uropathy
  • Common causes of urinary tract obstruction
  • congenital anomalies
  • calculi
  • tumors
  • urethral stricture
  • inflammation sloughed papillae
  • benign prostatic hypertrophy
  • pregnancy

Cervical cancer
MR urogram
77
Hematuria
T1
T2
Bleeding diathesis
78
Hematuria
right
T2
left
Bleeding Diathesis (iatrogenic)
79
Pregnancy
  • Common causes of urinary tract obstruction
  • congenital anomalies
  • calculi
  • tumors
  • urethral stricture
  • inflammation sloughed papillae
  • benign prostatic hypertrophy
  • pregnancy

18 weeks gestation
80
Pregnancy
MRCP
81
Obstructive Uropathy
  • Common causes of urinary tract obstruction
  • congenital anomalies
  • calculi
  • tumors
  • urethral stricture
  • inflammation sloughed papillae
  • benign prostatic hypertrophy
  • pregnancy

82
Renal Stone
  • Calculi appear as focal areas of decreased signal
    intensity on all sequences

83
Acute Ureteric Stone
84
Congenital Obstruction of the Ureteropelvic
Junction
  • Characteristic MR findings of Obstructive
    Uropathy (best seen in the
    coronal plane)
  • Hydronephrosis dilation of the renal pelvis,
    calyces, and infundibuli associated with
    progressive cortical loss and atrophy. Large
    calyces appear as focal areas of decreased signal
    intensity on both T1- and T2- weighted images.

85
Obstructed Duplication
  • Congenital ureteropelvic duplication may cause
    focal hydronephrosis in children
  • A duplicated obstructed ureter filled with urine
    (having the same density as water) may also be
    seen

86
References
  • Colletti P. M., Magre, G., Tyszka, J. M.
    Magnetic Resonance Imaging. Textbook of
    Nephrology, 1803-1817.
  • Cotran, R. S., Kumar, V., Collins, T. The
    Kidney Pathologic Basis of Disease, 6th ed. W.
    B. Saunders Company, Philadelphia, 1999.
  • Davidson, A. J., Hartman, D. S. Radiology of
    the Kidney and Urinary Tract. W. B. Saunders
    Company, Philadelphia, 1994.
  • Fang, Y. C., Siegelman, E. S. Complications of
    renal transplantation MR findings. Journal of
    Computer Assisted Tomography 25 (6), 836-842.
  • Grattan-Smith, JD., et al. MR imaging of the
    kidneys functional evaluation using F-15
    perfusion imaging. Pediatric Radiology 33
    293-304, 2003.
  • Grenier, N., Basseau, F. Ries, M., Tyndal, B.,
    Jones, R., Moonen, C. Functional MRI of the
    kidney. Abdominal Imaging 28 164-175, 2003.
  • Ho, V.B. and Choyke, P.L. MR Evaluation of Solid
    Renal Masses. Magnetic Resonance Imaging Clinics
    of North America 12 (3), 413- 428, Aug 2004.

87
References (cont.)
  • Huang, A.J. Lee, V.S., and Rusinek, H.
    Functional Renal MR Imaging. Magnetic Resonance
    Imaging Clinics of North America 12 (3),
    469-486, Aug 2004.
  • Huang, A.J. Lee, V.S., and Rusinek, H. MR
    Imaging of Renal Function. Radiologic Clinics of
    North America 41 (5), 1001-1018, Sept 2003.
  • Israel, G.M. and Bosniak, M.A. MR Imaging of
    Cystic Renal Masses. Magnetic Resonance Imaging
    Clinics of North America 12 (3), 403-412, Aug
    2004.
  • Israel, G. M., Bosniak, M. A. Renal imaging for
    diagnosis and staging of renal cell carcinoma.
    Urologic Clinics of North America 30, 499-514,
    2003.
  • Israel, G. M. and Krinsky, G. A. MR imaging of
    the kidneys and adrenal glands. Radiologic
    Clinics of North America 41 145-159, 2003.
  • Krestin, G. P. Morphologic and Functional MR of
    the Kidneys and Adrenal Glands. Field and Wood
    Medical Publishers, Inc., New York, 1991.

88
References (cont.)
  • Leyendecker, J.R. and Brown, J.J. Practical
    Guide to Abdominal and Pelvic MRI. Lippincott
    Williams Williams, New York, 1994.
  • Schild, H. H. MRI made easy (well almost).
    Berlex Laboratories, Inc., NJ 1992.
  • Schoenberg, S. O., et al. Morphologic and
    functional magnetic resonance imaging of renal
    artery stenosis A multireader tricenter study.
    Journal of the American Society of Nephrology 13
    158-169, 2002.
  • Sohaib, S. A., et al. Assessment of tumor
    invasion of the vena caval wall in renal cell
    carcinoma cases by magnetic resonance imaging.
    The Journal of Urology 167 1271-1275, 2002.
  • Zagoria, R. J., Tung G. A. Genitourinary
    Radiology The Requisites. Mosby-Year Book, Inc.,
    1997.
  • Zhang, H. and Prince, M.R. Magnetic Resonance
    Imaging Clinics of North America 12 (3),
    487-504, Aug 2004.
  • Zhang, J., Pedrosa, I., and Rofsky, N.M. MR
    Techniques for Renal Imaging. Radiologic Clinics
    of North America 41 (5), 877-908, Sept 2003.

89
References (cont.)
  • Semelka, R.C., Ascher, S.M., and Reinhold, C.
    General considerations for performing MR studies
    of the abdomen and pelvis. MRI of the Abdomen and
    Pelvis, Wiley-Liss, Inc., 1-18, 1997.
  • Semelka, R.C. and Kelekis, N.L. Kidneys. MRI of
    the Abdomen and Pelvis, Wiley-Liss, Inc.,
    389-470, 1997.

90
The End
Thank You
91
MRI Tutorial
  • Proton MR Tutorial
  • Proton MR Basics
  • Longitudinal Relaxation
  • Transverse Relaxation
  • MR Signal Characteristics of Different Tissues
  • Pulse Sequences
  • Conventional Spin Echo
  • Fast Spin Echo
  • Gradient Echo
  • Fat Saturation and Chemical Shift
  • Inversion Recovery
  • MR Angiography
  • MR Urography

92
Proton MR Tutorial
  • Atoms whose nuclei contain an odd number of
    protons possess angular momentum and act as
    dipoles (tiny bar magnets)
  • The most commonly used atom in MR imaging is the
    hydrogen atom, which has a single proton

N
S
Proton Spin
93
Proton MR Tutorial
  • When placed in a strong magnetic field
  • Protons align themselves along the longitudinal
    plane of the external magnetic field in either a
    parallel or an antiparallel way
  • The parallel state, which requires less energy
    and is preferred, results in a small net magnetic
    moment in the direction of the main magnetic
    vector

Net
94
Proton MR Tutorial
  • When placed in a strong magnetic field
  • Protons also precess (wobble) at a specific
    frequency around the magnetic field lines, in the
    net direction and orientation of the magnetic
    field
  • The stronger the magnetic field, the higher the
    precession frequency, according to the Larmor
    Equation

N
s
95
The Larmor equation ?0 ?B0
  • ?0 is the precession frequency (in Hz or MHz)
  • B0 is the strength of the magnetic field, in
    Tesla (T)
  • ? is the gyro-magnetic ratio, which is specific
    for each atomic nucleus (the gyro-magnetic ratio
    for protons is 42.5 MHz/T)
  • SUM The stronger the magnetic field, the higher
    the precession frequency of the proton

96
Proton MR Tutorial
  • A radiofrequency (RF) pulse is applied by a loop
    of coils in the magnet, which displaces the net
    magnetic vector from its longitudinal (resting)
    state onto the transverse plane

97
Proton MR Tutorial
  • The energy supplied by the RF pulse causes more
    protons to align in a higher energy antiparallel
    way, decreasing the longitudinal magnetization

98
Proton MR Tutorial
  • The RF pulse also forces the majority of the
    protons to precess together, or in phase,
    temporarily establishing a new transverse
    magnetization

99
Proton MR Tutorial
  • The time (in milliseconds) required for the net
    magnetic vector to recover 63 of its
    longitudinal magnetization is called the tissues
    T1 relaxation time

Longitudinal Magnetization
Signal
63
T1
Time
100
Proton MR Tutorial
  • The time (in milliseconds) required for the
    tissues transverse magnetization to decrease to
    37 of its peak value after the RF pulse is
    called the tissues T2 relaxation time

101
Proton MR Tutorial
  • T1 Relaxation Time
  • T1 varies with the magnetic field strength it is
    longer in stronger magnetic fields. T1 also
    depends on the tissue structure, composition, and
    precession frequency.
  • Water has a long T1 because the precession
    frequency of water molecules are faster than the
    Larmor frequency, which makes energy transfer
    slow.
  • Fat has a short T1 because the carbon bonds at
    the ends of the fatty acids have frequencies near
    the Larmor frequency, facilitating energy
    transfer.

Longitudinal Relaxation
Signal
63
T1Fat
T1Water
Time
102
Proton MR Tutorial
  • T2 Relaxation Time
  • T2 depends on the inhomogeneities of both the
    external magnetic field and the local magnetic
    fields within the tissues.
  • Pure water is a homogenous mixture of
    rapidly-moving water molecules which create a
    relatively uniform internal magnetic field.
    Protons stay in phase longer and therefore have a
    long T2.
  • Impure liquids contain larger molecules which
    move slowly, have larger differences in
    precession frequencies, and have greater
    variations in the local magnetic field. Protons
    get out of phase more easily, resulting in a
    short T2.

Transverse Relaxation
Signal
37
T2- impure liquids
T2 - pure water
Time
103
Proton MR Tutorial
  • Different tissues in the body are recognized by
    their distinct signal characteristics on
    T1-weighted and T2-weighted sequences

104
Proton MR Tutorial
  • By applying a weak magnetic field gradient
    superimposed on the uniform strong magnetic
    field, the precessional frequency of spins are
    increased or decreased in a linear fashion. This
    linear spectrum of precession frequencies can be
    used to select an imaging plane and to localize
    the protons position in space.
  • The RF energy returned (the spin echo or
    gradient echo, depending on the technique) is
    received by a computer and transformed into a
    visual representation of the volume of interest.

105
Pulse Sequences
  • Proton MR
  • Conventional Spin Echo Pulse Sequence
  • Fast Spin Echo Pulse Sequences
  • Gradient Echo Pulse Sequence
  • Fat Saturation and Chemical Shift Sequences
  • Inversion Recovery

106
Conventional Spin Echo
The conventional spin echo technique 1) 90
degree RF pulse displaces the longitudinal
magnetization into the transverse plane 2) 180
degree RF pulse rephases the vectors in the
transverse plane and neutralizes the external
magnetic field inhomogeneities (RF
refocusing) 3) The RF energy returned, the spin
echo, is detected by a receiver coil TR
repetition time (in milliseconds), or the time
between 2 successive RF pulses TE echo time (in
milliseconds), or the time between the 90 degree
RF pulse and the time the spin echo is generated
107
Conventional Spin Echo
  • T1 and T2 signal intensity curves can be combined
    in order to determine what TR and TE should be
    used to achieve a certain signal intensity for a
    tissue
  • The pulse sequence timing can be adjusted to give
    T1-weighted, T2-weighted images, or proton
    density images

Longitudinal Magnetization
Signal
Transverse Magnetization
TE
TR
Time
RF Pulse
RF Pulse
108
Conventional Spin Echo
  • T1-weighted sequences use a short TR (less than
    500 msec) and a short TE to exploit the
    difference in T1 longitudinal relaxation times
    found in different tissues. With a short TR, the
    time between successive RF pulses does not allow
    the tissues with slow T1 relaxation times to
    fully recover, yielding a variable spectrum of
    signal intensities for all tissues according to
    their unique T1 relaxation times.

Longitudinal Magnetization
Signal
Transverse Magnetization
TE
TR
Time
RF Pulse
RF Pulse
109
Conventional Spin Echo
  • T2-weighted sequences use a long TE (greater than
    80 msec) and a long TR to exploit the difference
    in T2 transversal relaxation times found in
    different tissues. A long TE provides sufficient
    time for protons with fast T2 relaxation times to
    lose phase coherence, while protons with slow T2
    times will still be in phase, causing a
    pronounced difference in signal intensity and
    contrast.

110
Conventional Spin Echo
  • Proton density images use a long TR (greater than
    1500 msec) and a short TE (less then 30 msec).
    The density of protons within a given tissue
    influences tissue contrast, with a greater proton
    density yielding a stronger, brighter signal.

Longitudinal Magnetization
Signal
Transverse Magnetization
TE
TR
Time
RF Pulse
RF Pulse
111
Fast Imaging Pulse Sequences
  • There are a variety of newer fast scan
    techniques, including the Fast Spin Echo (FSE)
    and Gradient Echo techniques.
  • The main method for increasing imaging speed is
    to shorten the TR, the most time-consuming
    parameter.
  • The fast imaging techniques differ in the way
    they overcome the lower signal/noise ratio caused
    by a short TR and in the way they refocus the
    dephasing spins in a limited amount of time.

112
Fast Spin Echo Pulse Sequence
  • The Fast Spin Echo (FSE) technique
  • similar to the conventional spin echo technique,
    however instead of a single rephasing RF pulse, a
    series of 180 degree RF pulses rephase the
    vectors in the transverse plane
  • Advantages of Fast Spin Echo over Conventional
    Spin Echo techniques
  • -increased signal/noise ratio
  • -a larger matrix conferring enhanced spatial
    resolution
  • -fat suppression techniques can be utilized

113
Gradient Echo Pulse Sequence
  • Technique
  • 1) An RF pulse displaces the longitudinal
    magnetization vector into the transverse plane by
    an amount less than 90 degrees (an ? pulse). By
    using flip angles less than 90 degrees, there
    is a residual amount of longitudinal
    magnetization which can be tilted by the next
    pulse.
  • 2) A magnetic field gradient (linear variations
    in magnetic field strength) are momentarily
    applied at specific times to rephase the
    magnetization vectors in the transverse plane
  • 3) The signal generated, the gradient echo, is
    detected by the receiver coil.
  • Flip Angle
  • larger flip angles give more T1-weighting, while
    smaller flip angles give more T2-weighting

114
Gradient Echo (GE) Pulse Sequence
  • Advantages of GE techniques over SE techniques
  • greater imaging speed (due to shorter TR and
    TEs)
  • less motion artifact (due to shorter TR and TEs)
  • better visualization of vascular structures
    (flowing blood
  • Is consistently bright)
  • Disadvantages
  • greater loss of signal from static magnetic
    field inhomogeneity
  • greater magnetic susceptibility artifacts

115
Fat Saturation and Chemical Shift Sequences
  • Technique
  • 1) A low-amplitude, long-duration RF pulse
    centered on the frequency of lipid proton
    resonance is applied to saturate the fat protons
    (Aliphatic hydrogen protons in fat precess at a
    frequency of approximately 220 Hz lower than
    water protons in a 1.5 T magnetic field).
  • 2) A spoiling gradient dephases the
    lipid-specific transverse magnetization
  • 3) A spin echo sequence is performed with signal
    reception centered on the resonance frequency of
    water before the fat protons have had enough time
    to recover. A T1-weighted image is produced.

116
Inversion Recovery Sequence
  • Technique
  • 1) A 180 degree RF pulse is applied, which
    inverts the longitudinal magnetization so that it
    is oriented in the opposite direction. This nulls
    the fat signal, while maintaining the water and
    soft tissue signals, thus this sequence can be
    used for fat suppression.
  • 2) A 90 degree RF pulse rephases the
    magnetization vectors in the transverse plane
  • 3) The signal returned depends on T1, which
    determines how fast the longitudinal
    magnetization returns
  • TI inversion time, or the time between the 180
    degree inversion pulse and the 90 degree
    rephasing pulse
  • TR repetition time, or the time between two
    successive 180 degree pulses

117
MR Angiography
  • Conventional Angiography A trans-femoral
    catheter is inserted and advanced through the
    aorta to the renal artery, where iodinated
    contrast media is injected. A fluoroscopic device
    detects the contrast, and radiographic films are
    made.
  • MR Angiography IV injection of a paramagnetic
    contrast agent such as gadolinium, followed by MR
    imaging once the contrast has reached the renal
    vessels.
  • Digital Subtraction Angiography (DSA)
    Computer-assisted subtraction of post-contrast
    images from the precontrast ones to enhance
    vessel visualization can be used with either
    conventional or MR angiography.

118
MR Angiography
  • Two main methods of MR Angiography
  • Time of flight (TOF) A continuous inflow of
    protons with unsaturated, fully relaxed spins
    yields a high signal when RF-stimulated in
    contrast to the saturated surrounding tissue. TOF
    is best for imaging vessels with fast flow, such
    as the renal veins and inferior vena cava.
  • Phase Contrast (PC) Protons with moving spins
    acquire a difference in phase as they move along
    a magnetic field gradient, in relation to their
    flow direction and velocity. This allows for
    background suppression of stationary tissue so
    that the blood flow in vessels can be visualized.
    PC is best for imaging the renal arteries.

119
MR Angiography
  • Utility of Renal MR Angiography
  • Detection of renal artery stenosis or
    arteriopathy (vasculitis, aneurysm, fibromuscular
    dysplasia, arteriovenous malformation,
    arteriovenous fistula, or hemangioma)
  • Preoperative planning for renal revascularization
    surgery
  • Palliative ablation of a hypervascular neoplasm
  • Evaluation of vascular function and morphology in
    potential transplant donors and recipients
  • Postoperative assessment of perfusion status

120
MR Urography
  • Clinical Application
  • to evaluate ureteral obstruction and congenital
    urinary tract abnormalities

121
MR Urography
  • Static MR Urography
  • Technique Heavily T2-weighted sequence similar
    to MRCP
  • Works best for dilated collecting systems
  • Can even be used in patients with severe renal
    insufficiency
  • No imaging delay or IV contrast necessary, but
    overlapping fluid-filled structures can interfere
  • Tip imaging nondilated ureters can be enhanced
    by hydrating the patient and administed a low
    dose of furosemide before the exam
  • Excretory MR Urography
  • Technique T1-weighted 3D gradient echo sequence
    after IV contrast administration
  • Can demonstrate nondilated as well as dilated
    ureters
  • No interference by overlapping fluid-filled
    structures
  • Cannot be used in patients with severe renal
    insufficiency

122
The End
Thank You
About PowerShow.com