 |
Brain:
Because of its
superior sensitivity compared to X-ray and CT in delineating differences
between various tissues, MRI is unsurpassed as an imaging modality for most
disease processes in the central nervous system. In many cases, the need for
arteriography will be eliminated and there will be further improvements as
magnetic resonance angiography (MRA) develops. The detection rate of most types
of brain lesions by MRI exceeds 90%, compared to 77% for CT - without the
invasiveness or risk of iodinated intravenous contrast agents or the inherent
problem of the radiation effect of X-rays. These safety features make MRI
especially advantageous for the pediatric and elderly populations.
MRI's
clinical advantage in early detection of disease
is visually demonstrated as unmistakable contrast between gray and white
matter and tumor
ischaemia/infarct, edema, MS plaques, infection/abscess
and hemorrhage. Contributing to this is MRI's inherent sensitivity as
well as its capability to
directly image in any place without reformatting,
and to be unimpeded or undistorted by bony structures that severely degrade
CT images (especially in
the posterior fossa, foramen magnum and temporal
lobe areas).
Gadolinium
contrast imaging has become the "gold standard" in the primary evaluation of
brain tumor of all types, benign or malignant; post-operative recurrences;
differentiating oedema from tumor foci; metastatic brain disease; and those
pathologies requiring the detection of very small masses.
Applications
Include:
- Primary and secondary (metastatic)
neoplasms
such as tumors of the hemispheres, the posterior fossa,
foramen magnum (craniovertebral junction), pituitary gland and cerebellopontine
angle lesion (acoustic neuromas)
- Stroke (infarction) and other vascular
lesions
such as lacunar (hypertensive, small vessel) disease, posterior
fossa-brainstem lesions, bland vs. hemorrhagic stroke, arteriovenous
malformations (AVM), multi-infarct dementia (MID)
- Seizure disorders
such as temporal lobe
epilepsy
- Traumatic injuries
such as cerebral
contusion, subdural haematoma
- Degenerative disease
such as dementia
(Alzheimer's Disease), radiation gliosis, necrosis, post-operative
changes.
- Demyelinating disease
such as multiple
sclerosis (MS), alcoholic myelinolysis, pediatric white matter disease,
leukodystrophies.
- Infectious and inflammatory disease
such
as herpes encephalitis, meningitis, abscesses, cerebral vasculitis,
granulomatous lesions (eg. sarcoidosis), AIDS - related to
meningoencephalitis.
- Hydrocephalus
communicating vs.
non-communicating
- Psychiatric disorders
MRI can investigate
underlying organic disorders or structural abnormalities associated with, for
example, psychomotor retardation, affective disorders (schizophrenia,
manic-depression, etc.), dementia.
- Temporomandibular joint (TMJ)
such as
articular disc subluxation, condylar head degeneration, impaired
motility.
[Back to Top]
Orbit and Optic
Nerves:
Selection of an imaging plane other than axial (eg. an oblique
plane along the axis of the optic nerve) allows better definitions of a lesion.
With the use of specialty surface coils, not only can subtle pathological
changes be detected, but high resolution images are achieved without the risk
of exposure to potentially cataract-inducing X-rays. Because of these
advantages, MRI provides improved reliability in determining the presence and
extent of tumor, granulomatous disease (eg. sarcoid), infection and
hemorrhage.
Applications Include:
- Tumors and other mass lesions
involving
· the globe
·
retina
·retro-orbital space
- Trauma, hemorrhage, blowout fractures
[Back to Top]
Abdomen:
The advent of
special and fast scanning techniques -breath-holding studies are now possible
-reduces motion infarct, permitting MRI to complement and, in many cases,
surpass CT.
Given that CT misses between 20 to 30% of liver metastases,
improving detections is crucial since cancer metastases to the liver is ten
times more frequent than in other organs. Therefore, MRI is an excellent
screening study for the liver because of its great sensitivity in detecting
lesions, especially metastases.
It is very specific for cavernous
hemangioma (the most common hepatic neoplasm) eliminating
the need for liver biopsy with this diagnosis. MRI
is also useful in detecting and monitoring the
progress of other diseases such as hepatitis, hemochromatosis,
the spread of intra-abdominal tumors, renal vein
thrombosis, inferior vena cava, tumor
invasion, venous flow pattern and portal vein obstruction.
MRI is gradually developing a larger role in the
diagnosis of adrenal, renal and pancreatic
masses as well as all types of retroperitoneal disease.
Applications
Include:
- Liver
primary tumors and metastases,
lymphoma, cavernous haemangioma, hepatitis, cirrhosis, hemochromatosis, portal
vein obstruction.
- Tumors, cysts, hemorrhage abscess
- adrenal gland, pancreas, spleen, renal.
- Extent or tumor into vascular
structures
(eg. vena cava and renal vein)
- Retroperitoneal lesions
- Aortic aneurysm,
dissections
(differentiation of false from true lumen)
- Lymphadenopathy,
especially periaortic
and retroperitoneal
- Trauma evaluation
[Back to
Top]
Pelvis/Genitourinary
System:
MRI offers an advantage over CT in the pelvis because of its
greater tissue sensitivity, absence of bone artifact and ability to acquire
multiplanar views. Lack of ionizing radiation makes MRI a natural tool for the
study of the reproductive organs and pelvic contents. In some instances, where
ultrasound has demonstrated a pelvic mass of indeterminate signal, MRI has
clarified its adnexal or uterine location. MRI aids in the staging of carcinoma
of the endometrium, cervix, prostate and rectum. In the differentiation of
renal masses, renal vein invasion or thrombosis, tumor extension into the
inferior vena cava, renal hilar and periaortic lymphadenopathy are
well-visualized with MRI.
Applications Include:
- Primary and metastatic neoplasm and their
extension
- Prostate cancer staging
- Rectal tumors, especially with pelvic
extension
- Gynecological disease
such as tumors and
cysts of cervix, uterus, ovaries, vaginal carcinomas, inflammatory disease,
abscess
- Renal, perirenal tumors, cysts,
abscesses
- Renal corticomedullary changes
- Renal vein invasion and thrombosis
- Bladder tumor – primary and
metastatic
[Back to Top]
Thorax and
Mediastinum:
With the use of cardiac gating and fast scanning
techniques, MRI studies of the chest have become the procedure of choice in
many instances. IN particular, MR images of the hilum, mediastinum, pericardium
and its contents have substantially improved in terms of tissue contrast,
differentiation and reslution. Because of the ability to distinguish vessels
from soft tissue masses without the use of IV contrast agents and without being
plagued by streak artifacts, MRI is proving useful in diagnosing mediastinal
and hilar masses as well as lymph node enlargement.
MRI appears to be
superior in the differential diagnosis of hilar and mediastinal vascular
lesions (eg. compression, invasion, obstruction), normal vessels, nonvascular
lesions and lymph nodes. MRI is no less capable than CT in diagnosing
abnormally enlarged mediastinal lymph nodes or mediastinal masses, but does
fall short in being able to consistently define calcifications.
Even
without cardiac gating, small hilar and mediastinal lymph nodes, the esophagus,
thymus and thyroid glands are well resolved with MRI. Clarification of pleural
thickening and effusion, obstructed lung vs. tumor extension, often can be
useful in the treatment planning of malignant disease. Gating can be useful in
suspected cases of vascular lesions, paracardiac, mediastinal or lung
masses.
Applications Include:
- Benign tumors
- Primary and metastatic
tumors
bronchogenic carcinoma, esophageal carcinoma, lymphoma,
thymoma
- Inflammatory, granulomatous
disease
sarcoidosis
- Extent of vascular involvement of
lesion
differentiation from hilar adenopathy
- Cardiac/pericardial lesion
fibroma,
myxoma, lipoma, cysts, abscess, metastases
- Obstructed lung vs. tumor extension
- Elimination of partial volume errors on CT using
multiplanar imaging
- Aortic dissections, aneurysms and
anomalies
[Back to Top]
Spine and Spinal
Cord:
MRI yields diagnostically superior images of the cervical,
thoracic and lumbosacral spine without the distortion from bone artifacts that
CT experiences. It provides clear visualization of the spinal cord, CSF spaces,
spinal nerves and roots, intra-spinal fat and ligaments, neural formina,
vertebral bodies, facet joints, vertebral marrow spaces and intervertebral
discs.
Using multiplanar imaging, a single, non-invasive MRI study for
many disorders of the spine can be substituted for a CT and myelogram (which
has the inherent risk of intraspinal contrast agents and CSF leaks). In
particular, MRI is considered to be the procedure of first choice of
myelophatic disorder at all levels of the spine to rule out, for example, intra
or extradural primary or metastatic tumors affecting the spinal cord with or
without vertebral involvement, for Chiari malformation, syringomyelia and to
investigate radiculopathies secondary to suspected disc disease at all
levels.
Gadolinium contrast imaging has had a significant impact in
increasing the conspicuity of lesions and for differentiating recurrent
herniated discs from post-operative scarring, an extremely difficult clinical
problem not screened well by CT even with iodinated contrast enhancement. MRI
should now be seen as the primary investigation for such
patients.
Applications Include:
- Cord tumors
extradural and intradural,
extramedullary and intramedullary
- Myelomalacic disorders
with or without
cord compression, spinal block or cord atrophy
- Syringomyelia
- Multiple sclerosis
- Congenital abnormalities
Arnold-Chiari
malformations, dysraphisms (eg. spinal bifida), lipoma, tethered spinal
cord.
- Spinal stenosis
- Disc disease
Herniated and fragmented
discs, degenerated discs, post operative scarring.
- Trauma
hemorrhagic and non-hemorrhagic,
oedoma, cystic or necroticatrophic changes, fractured displaced vertebral
bodies
- Osteomyelitis and discitis
[Back to Top]
Musculoskeletal System -
Extremities:
The advantage of MRI over CT and other imaging modalities
in evaluating pathological disorders of musculoskeletal tissue derives from the
superior depiction of contrast between muscle, fat, vessels, tendons,
ligaments, cartilage, synovium, cancellous bone and marrow space, all without
bone artifact or need for invasive procedures.
Disorders include bone
and soft tissue neoplasms, different stages of infection and osteomyelitis,
many types of soft tissue trauma, early bone avascular necrosis and cartilage
and ligament injuries, especially of the knee, shoulder hips and ankles. With
the use of the high resolution surface coils, fine details are revealed of the
patella, ligaments, menisci and cruciates of a diagnostic quality sufficient to
replace arthrography and focus artroscopy in most knee injury cases.
MRI
has been accepted as the procedure of choice in examining suspected cases of
aseptic/avascular necrosis of the hips, knee, ankle, shoulder, and wrist. It is
rapidly gaining a dominant role in evaluating rotator cuff injuries of the
shoulder and complex abnormalities of the hand and wrist, including triangular
cartilage injuries, avascular necrosis of lunate and scaphoid, and carpal
tunnel syndrome.
Applications Include:
- Osteonecrosis (aseptic/ischaemic
necrosis)
of the hips, knees, ankles, shoulders and wrists
- Osteomyelitis
- Soft tissues and bone neoplasms, primary and
metastatic (eg. osteosarcoma, giant cell tumors)
involvement and extent
in extremities.
- Knee joint evaluation
cruciate ligament
tears, meniscal tears, subchondral cysts effusions
- Shoulder joint evaluation
rotator cuff
tear, anterior or posterior dislocation, osteonecrosis, osteoarthritis
- Arthritis
- Bone marrow pathology
- Wrist
cartilage tears
- Elbow
nerve impingement
[Back to Top]
Head and Neck:
With
the application of improved surface coil techniques, MRI is emerging as the
preferred imaging study for many of the extracranial head and neck disease
processes that in the past required CT.
MRI surpasses CT in its ability
to show abnormal soft tissue extensions, and in its ability to differentiate
vascular from nonvascular structures or to delineate subtle differences in soft
tissue boundaries, pathological changes and tumor extensions. This improved
sensitivity, coupled with multiplanar imaging, provides the clinician with
views most appropriate for optimizing diagnosis treatment and planning, and for
carrying out and monitoring therapy (eg. choosing the appropriate surgical
approach of designing the most effective radiation ports). A more accurate
determination of tumor involvement can, for example, preserve voice function by
avoiding the need for total laryngectomy; it can rule out surgery in cases of
unresectable tumor because of spread of the tumor to adjacent
organs.
Applications Include:
- Primary and metastatic tumors
thyroid,
parathyroids, oropharynx, nasopharynx, hypopharynx, retropharynx, tongue,
larynx, salivary glands, soft tissues of neck, paranasal sinuses
- Lymphadenopathy
- Infections, abscess
- Post-radiation evaluation
- Congenital anomalies
[Back to
Top]
|
|
 |
 |
|
