Applications of CT Scan and MRI scan

A CT scan is most beneficial for observing bone structure, and is less useful for scanning soft tissues in the body. To scan these tissues more effectively, a doctor will usually suggest an MRI scan. MRI stands for Magnetic Resonance Imaging. Rather than using radiation, this procedure exposes the body to a strong magnetic field, which affects the molecules in the body in such a way that a detailed picture can then be produced.

AttributeCT ScanMRI scan
AboutCT Scan or Computed tomography is a medical imaging obtained using X-rays. The radiation is passed through the body and received by a detector and then integrated by a computer to obtain a cross sectional image that is displayed on the screenMagnetic resonance imaging (MRI) is a medical imaging technique most commonly used in radiology to visualize detailed internal structure of the body.,because of better soft tissue resolution.
EffectsDespite being small, CT can pose the risk of irradiation.No biological hazards have been reported with the use of the MRI.
Principal used for imagingUses X-rays for imagingUses radio waves and magnetic field
Time taken for complete scanUsually completed in 5 minsUsually completed in 20 mins
Types of ScannersMultislice scanners offer reduced examination times and more importantly employ thin sections and improved resolution. Advanced applications can be done only on Multislice scanner.1.5 Tesla MRI-Higher magnetic field strength contributes high quality images, thinner slice thickness and potentially earlier and better detection of pathology. Advanced applications improves diagnosis.
Advanced ApplicationsCardiac CT, Denta Scan, Multiphasic Liver scan, Angiographies, 3 D imaging of bones,High resolution scan of thorax.Spectroscopy,Diffusion tensor imaging,Breast MRI,Non contrast Angio,MRI Urography ,MRCP & Cardiac Imaging


Clinical ProblemPreferred ModalityContrastComments
Head injury: SDH/ EDH/ SAH/FracturesCTNoFaster imaging technique.
Diffuse axonal injuryMRINoDeep seated, microhemorrhages are detected.
StrokeMRI > CTNoMRI detects infarcts in the hyperacute stage before it can be seen by any other modality. Angiography provides additional information about the thrombosis of the vessel involved
TumorsMRIYesMultiplanar imaging-Better delineation of the extent and spread. MR spectroscopy- provides details about the metabolite contents of lesion ,which may help in differentiating infection from neoplasm.
SeizuresMRI Provides better details of brain structure than any other modality. Images are helpful for identifying areas of scar tissue, abnormal development (dysplasia), and also changes in the brain white matter.
HeadacheMRI with ANGIO and VENOGRAM Additional information is obtained like venogram and angiogram and that too without contrast.
CNS InfectionsMRIYes 
Dementia/ Neurodegenerative DisordersMRI+/- 
Pituitary lesionsMRIYesDynamic contrast evaluation helps in detecting small pituitary microadenomas


Clinical ProblemPreferred studyContrastComments
Herniated Disc, Cervical or ThoracicMRINoThe disc, nerves and spinal cord can be seen clearly and in multiple planes.
Herniated Disc, LumbarMRIIf previous surgery, contrastContrast essential to distinguish scar from recurrent disc prolapse after surgery
Canal StenosisMRI >> CTNo 
Metastasis: Bone Epidural IntraspinalMRIYes 
Benign Fracture v/s Pathological FractureMRI/CT+/-MRI allows evaluation of bone marrow, CT for operative planning.
Cord DiseaseMRIYesDemyelination, Syrinx,Vascular abnormalities can be easily appreciated
Cord tumorMRIYes

Neck, Skull base, Orbit

Clinical Problem:Preferred studyContrastComments
SinusitisCTNoCT defines ostial obstruction, bone changes
Neck massMRI > CTYesTongue and perineural skull base disease better on MRI
Hearing loss, conductiveCTNoMastoid, middle ear,ossicles are better seen on CT.
Hearing loss, sensorineuralMRIYesCranial nerves are well delineated.
Skull baseMRI = CTYesCT sometimes necessary to better show bony detail.
Vocal cord paralysisMRI >> CTYesEvaluating focal lesions from skull base to carina.
Orbit—ProptosisCT or MRIYesNo contrast for graves’ disease.
Optic nerves pathologyMRI >> CTYesMRI – optic neuritis.
Cavernous sinus pathologyMRIYesMRI brain/sella
Cranial nerves pathologyMRIYes 
Facial traumaCTNoBony detail better appreciated
Salivary glandMRI/CTYesCalcification and microcalculi better seen on CT MRI for ductal abnormalities, tumors, infections

Breast Imaging

Clinical ProblemPreferred studyContrastComments
Screening in high risk patientsMRIYesLesion detection is far more superior in patients with negative or nonspecific findings on mammography
Staging of Breast CancerMRIYesTo know the extent and infiltration.


Clinical ProblemPreferred studyContrastComments
Pulmonary embolusCT angiographyYes 
Nodule, Mass, infiltrate.CTYesLung Parenchyma better evaluated on CT.
Interstitial Lung DiseaseHigh resolu­tion CTNoThin slices help in identifying distribution of smallest of the nodules
Mediastinal/ Vascular PathologyMRI / CTYes 


Clinical ProblemPreferred studyContrastComments
Joint ImagingMRINoExcellent details of intra-articular structures like cartilage and ligaments.
FracturesCT / MRINo 
Spinal TraumaMRI preferred for spinal cord evaluation.NoFracture fragments better depicted on CT.
Bone TumorsMRIYesThe tumors are well delineated and the extent of bone marrow involvement is better seen.


Clinical ProblemPreferred studyContrastComments
Non-focal painMRI = CT+/-Contrast for solid organ disease.
Focal organ pathologyMRI / CT abdomen+/-Multiphasic scan suggested for liver lesions.
Gall Bladder/ Pancreatic PathologyMRI+/-Biliary tree can be evaluated without contrast for any stones or strictures
Appendicitis, Diverticulitis.CT abdomen and pelvisOral contrast, +/- I.V contrast 
Painful HematuriaCT abdomen and pelvis+/-Detection of ureteric calculus. CT IVP to evaluate renal function.
Painless HematuriaCT/MRI abdomen+/- 
Renal massMRI/ CT abdomenYes 
Cancer patient/Metastasis screeningWhole body metastasis screening by MRI.+/- 
Adrenal glandMRI > CT Contrast only if non-contrast study is inconclusive
Staging of gynaecological malignancies

For prostate and other pelvic pathologies



Benign lesions of pelvis including fibroids, dermoids and endometriosis can be well evaluated due to excellent soft tissue differentiation on MRI.

MRI is now the examination of choice for staging mostmalignancies owing to its multiplanar capability.