CT vs. MRI

Computed Tomography (CT)

Computed tomography (CT) is a modern imaging tool that combines X-rays with computer technology to produce a more detailed, cross-sectional image of your body. A CT scan lets your doctor see the size, shape, and position of structures that are deep inside your body, such as organs, tissues, or tumors.

Magnetic Resonance Imaging (MRI)

Magnetic resonance imaging (MRI) is another modern diagnostic imaging technique that produces cross-sectional images of your body. Unlike CT scans, MRI works without radiation. The MRI uses magnetic fields and a sophisticated computer to take high-resolution pictures of your bones and soft tissues. 

The table below outlines which image modality MRI or CT may be considered depending on what your physician is looking for.

Head / Brain

MRI

Arteriovenous malformations

Encephalomalacia

Epilepsy and adult onset seizures

Hemangiomas

Hydrocephalus

Infection / Inflammation

Infratentorial tumors

Lacunar infarcts

Lyme disease

Meningiomas

Multiple sclerosis

Orbit and optic nerve disease

Pituitary dysfunction

Posterior fossa abnormalities (acoustic neuroma and skull base pathology)

Space occupying lesions

Stroke—(Use diffusion-weighted MR imaging)

Supratentorial tumors

Syringomyelia and Chiari malformations

Vascular/congenital abnormalities

White matter disease

ENT

MRI

Disease of the larynx (staging)

Paranasal sinus diseases (soft tissue masses, CA staging)

TMJ meniscal and soft tissue evaluations

Sensorineural hearing loss

CT

Cholesteatoma

Conductive hearing loss

Evaluation of the oro-, hypo-, and nasopharynx

Facial bone trauma

Orbital trauma

Ossicular or vestibulocochlear deformities

Otosclerosis/otospongiosis continuum

Sinusitis

Salivary gland disease

TMJ – bone destruction or arthritis

Spine

MRI

CT

Post discography to assess the morphology of an intervertebral disc

Scoliosis (CT best for bone detail)

Vertebral fractures – all levels

Chest 

MRI

Assessment of cardiac function

Brachial plexus and axillary pathology

Congenital heart lesions or cardiac abnormalities

Great vessel anomalies

Intracardiac or pericardial masses

Mediastinal masses

Vascular structures of the mediastinum and chest

Valvular disease

CT

Aortic dissection

Hilar and parenchymal nodules

Lung disease

Abdomen

MRI

Evaluation of renal vasculature (MRA)

MRCP recommended when

Diagnostic component needed before therapeutic ERCP

When ERCP is impossible

Patients who have failed ERCP

Patients who only require a diagnostic study

To exclude sclerosing cholangitis, pancreatic neoplasm or chronic pancreatitis

Tumor invasion of vena cava

CT

Abdominal aortic aneurysm

Benign and malignant disease of the liver

Diagnosis and staging of non-hepatic intra-abdominal infections and tumors

Screening examination for symptoms when detail of the liver, spleen, kidneys or pancreas is needed

Pelvis

MRI

Bladder carcinoma staging

Prostate carcinoma staging

Uterine carcinoma staging

Seminal vesical tumor invasion

CT

Nodal assessment

Pelvic Mass (useful, but ultrasound still preferred)

Pelvic pain

MUSCULOSKELETAL

MRI

Achilles tendon injury

Ankle – ligamentous injuries

Avascular necrosis

Bone and soft tissue tumors

Knee injury including meniscal, cartilaginous and tendinous

Metastatic disease of bone

Occult fractures not apparent on plain films

Osteoarthritis of hip, knee, shoulder and ankle

Osteochondritis dissecans

Osteomyelitis

Rotator cuff injuries

Tendon injuries of the elbow 

CT

Complex fractures (3-D CT reconstruction)