When do RM and when CT? Advantages and disadvantages

Diagnosing or confirming certain conditions involves performing some additional investigations of blood, ultrasound or radiographs, such as Computed Tomography (CT) or Magnetic Resonance (RM). These are two diagnostic modalities that use different techniques for imaging acquisition: X-ray for Computed Tomography and magnetic field for Magnetic Resonance.

In some affections one of these ways is preferred, sometimes they are complementary. Each has advantages and disadvantages, taking into account the information needed for diagnosis, investigation costs and patient comfort.

The current trend in advanced countries is to gradually give up irradiation investigation methods (such as computerized tomography) in favor of magnetic resonance imaging. "It should be borne in mind that the type of imaging investigation indicated to the patient is chosen according to the known or suspected pathology. Sometimes CT is recommended, sometimes RM, and in some cases they are complementary. Therefore, close collaboration between the radiologist and the doctors is very important for choosing the optimal imaging method for each patient. Thus, CT is the first exam in traumatic affections (bone fractures, intracranial hematoma) and chest exploration. instead, RM is preferred in neurological, vascular and musculoskeletal pathology, with a triple plus trials, "says Gina Zaharia, radiologist at the Provita Medical Center for Diagnosis and Treatment.

Computed Tomography (CT)

It is an irradiating method using X-rays. It is cheaper, faster and easier to tolerate by the patient. With computerized tomography we can get images of any part of the human body, from the brain to the extremities. Strengths include: bone fracture, calcification (intra-articular calcification or renal lithiasis), haemorrhage and pulmonary parenchyma assessment. Sometimes, especially in the assessment of blood vessels or internal organs, it is necessary to administer an intravenous contrast substance based on iodine that is excreted in the kidney.

Therefore, before carrying out the investigations, it is necessary to perform some laboratory tests demonstrating good kidney function (urea and serum creatinine). These analyzes should not be older than 10 days.

The main inconvenience of CT is that it is an irradiating method; therefore it is contraindicated to pregnant women and caution is recommended when performing tomographies of children or young people. In addition, computed tomography is contraindicated in patients with renal insufficiency and those with allergic reactions to the contrast substance. Last but not least, computerized tomography has a lower tissue contrast than Magnetic Resonance. Regime for abdominal and / or pelvic CT: do not eat 6 hours before the investigation.

Magnetic Resonance (RM)

It is a non-irradiating method that uses a magnetic field and radiofrequency pulses to obtain images. It has an increased sensitivity of tissue constraint (the ability to distinguish between several tissue categories and, implicitly, superior detection of lesions compared to other imaging techniques) and allows to obtain detailed images in various planes, which allows precise localization of lesions, very useful in planning surgery.

With Magnetic Resonance, we can investigate pathologies from the cerebral, vertebro-medullar, musculoskeletal, cardiovascular and abdominal-pelvic stages. RM is the imaging modal for the detection of joint injuries, being the only non-invasive examination that provides a detailed picture of structures such as meniscus (knee), ligaments or tendons. For mammary gland examinations, complementary to mammary ultrasound and mammography, a RM exam can be performed that can sometimes differentiate between malignant or benign lesions and can detect multifocal lesions.

Sometimes Gadolinium-based intravenous contrast agent is needed, but the risk and severity of allergic reactions are much lower compared to those developed with iodinated contrast substance.

Patients were required to perform urea and serum creatinine (blood) tests not older than 30 days. This analysis is important in order to be able to administer the contrast substance (the radiologist decides if it is necessary to administer it).

Being a non-irritant method, it can be done by pregnant women in the last two trimesters of pregnancy, especially for any fetal malformations highlighted in the ultrasound exam.

The RM exam is contraindicated for: persons with pacemaker, implantable cardiac defibrillator, old type prosthetic dentures, soft parts of the soft parts, joint metal prostheses or osteosynthesis materials, aneurysm clips or certain vascular stents, cochlear implants and severe renal failure. in addition, is not indicated in the first trimester of pregnancy.

The regime for RM of the abdomen and / or pelvis is as follows:

The day before the investigation:

  • Until 10:00 A.M. - 4 DULCOLAX pills - all at once
  • After 10:00 o'clock in the hour, 2 ESPUMISAN pills (approximately 15 pills).
  • No food that balloons (eg fruits, vegetables, dairy products, acidic beverages).
  • From 20:00 - without food;
  • Starting at 21:00 - without any liquid - if the exam is done the next day until 14:00.

The morning of the investigation does not eat or drink anything (if you have a schedule until 14:00).

If the exam is after 14:00 the following day:

  • In the morning of the investigation, take 3 Espumisan pills.
  • you can eat up to 6 hours before and drink fluids up to 3 hours before the investigation.

VERY IMPORTANT: Diabetic patients are exceptions to diet and should do the treatment recommended by the physician for not having hypo / hyperglycemia problems.It is recommended not to chew gum.

FOR MEN - Minimum 5 days of sexual intercourse;

FEMALE: Do not be during menstruation.

If there are patients who say they can not keep this diet for medical reasons (eg, cancer patients or the very elderly) will hold only Espumisan regime and diet and health will be announced in this turn.

Patients who do not comply with this regime will not be able to investigate.


The incidence of breast cancer has increased in recent years, with 1 in 6 cases occurring in women aged 40-49 years.

Digital mammography with tomosynthesis is the most advanced diagnostic method for women starting at age 40 for the early detection of breast cancer.

Online Programming