Is a CT Scan or an MRI the better choice for you?

Over the last 40-50 years, CT scans and MRI machines have tremendously advanced the non- invasive imaging of the body’s internal organs. Since they became commercially available, the CT scan in 1973 and the MRI in the early 80s, their imaging capabilities have improved by leaps and bounds.
A question that often arises in the patient’s (and doctor’s) mind is, “Would a CT scan or an MRI be the better investigative tool for me (the patient)?”.

The CT scan machine reconstructs its images by layering a number of narrow beams of x-rays that traverse a targeted area of the patient’s body circumferentially; the machine’s computer captures the images. Such images are often referred to as slices.

The MRI machine creates a powerful magnetic field around the patient. This causes the patient’s hydrogen atoms to align. Radio waves are then sent from the MRI machine into the patient, which results in the atoms being moved out of alignment. When these radio waves are turned off, the atoms revert to their aligned position. This movement emits radio signals, which are recorded by the MRI’s computer, ultimately constructing an image of the area of the body undergoing study.

MRI (1.5T) vs. CT Scan (128 slice) for Specific Areas and Organs

Head:  CT scans are preferred in emergency settings, when looking for foreign bodies, and in identifying bone fractures – e.g. at the base of the skull. In all other situations (e.g. suspected brain tumour, stroke, bleed, swelling, trauma, developmental abnormalities, unruptured aneurysms, encephalitis, cyst, multiple sclerosis, Alzheimer’s, etc) the MRI is preferred.

Paranasal sinuses: MRI is preferred in identifying pathology arising within the sinuses.

Ear: MRI is preferred for assessing the inner ear and vestibulocochlear nerve.

Neck: In assessing the soft-tissue the MRI is preferred.
Spine (neck to lower back): MRI is the gold standard for detecting the most common pathologies of the cervical, thoracic, and lumbar spine. The CT scan is preferred in detecting bone fractures.

Lungs: CT scan is a more valuable tool for spotting or monitoring pathology that may be found in the lungs.
Breast: MRI mammography is increasingly being used to screen for breast cancer in high risk women, women who have the BRCa 1 and or 2 gene, and those with very dense breasts.

Heart: CT angiography is a better tool for assessing the heart’s coronary arteries.

Abdomen: For acute abdominal pain a CT scan is preferred.
Colon: CT scan is a well established modality of assessing the colon.

Urinary tract: CT scan is often preferred for uncovering and assessing kidney, ureter and bladder pathology.

Liver: An MRI is superior to a CT scan when identifying and defining pathology in the liver.

Pancreas: The MRI edges out the CT scan for its overall diagnostic accuracy.

Gallbladder and bile ducts: The MRI’s sharp images provide a more accurate appreciation of any pathology of the gallbladder and the biliary ducts.

Adrenal glands: CT scan is preferred for imaging adrenal glands.

Spleen: CT scan is preferred when assessing the spleen. If micro-abscesses are suspected a MRI is recommended.

Prostate: MRI of the prostate is preferred for detecting prostate malignancies and local spread.

Uterus: The MRI is preferred when it comes to providing detailed uterine imaging.

Ovaries: The MRI’s excellent specificity and sensitivity in detecting ovarian cancer places it ahead of the CT scan (and PET Scan).

Extremities (arms or legs): The MRI is superior to a CT scan when it comes to differentiating soft tissue pathology in the limbs – i.e. muscle, cartilage, ligaments, tendons, fat, nerves. Bone tumours and the bone marrow is best evaluated by MRI. A CT scan is better at identifying and assessing fractures.

General Points on CT scans and MRIs

•  To ensure the best quality images the MRI machine should be a 1.5T (Tesla) – considered state-of-the-art, and the CT scan should be a 128 slice machine or greater.
•  CT scans are less expensive.
• MRI soft-tissue images are more detailed than the CT scan’s.
• CT scan’s ionising radiation may marginally increase the risk of developing cancer in the future.
• MRIs are not advisable for anyone with metal (especially iron) implants – e.g. pacemakers, cochlear implants, implantable defibrillators, artificial joints, aneurysm clips, plated bones, (some) IUDs
• CT scans are faster.
• When detailed images of soft tissues, ligaments, or organs, are critical, the MRI is the better option.
• CT scans are preferred in emergencies, or when lung, kidney, bowel, adrenal, spleen, or heart pathology, or bone fracture, is suspected.
• Those with claustrophobia often have challenges undergoing MRIs.
• MRIs are preferred to CT scans for children, expectant mothers, and patients requiring multiple radiological examinations.
•  MRI contrast agent (dye) is much less likely to induce an allergic reaction when compared to the CT scan’s.

Author: Dr. C. Malcolm Grant – Family Physician, Family Care Clinic, Arnos Vale.
Former tutor in the Faculty of Medical Sciences, University of the West Indies, Cave Hill, Barbados.
For appointments: clinic@familycaresvg.com, 1(784)570-9300 (Office), 1(784)455-0376 (WhatsApp).
Disclaimer: The information provided in the above article is for educational purposes only and does not substitute for professional medical advice. Please consult a medical professional or healthcare provider if you are seeking medical advice, diagnoses, or treatment.
Dr. C. Malcolm Grant, Family Care Clinic or The Searchlight Newspaper or their associates, respectively, are not liable for risks or
issues associated with using or acting upon the information provided above.