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What is the difference between an X-ray, CT scan, MRI and ultrasound?

Imaging exams are important as they assist the clinician in better understanding what is happening within the patient's body. They serve to rule out serious changes, such as malignancies, and can also reveal fractures, anatomical variations, tissue alterations, inflammations, and may even influence chiropractic treatment plans. Each exam has a sensitivity for a specific type of tissue, and usually a request protocol is followed to avoid unnecessary exposure to ionizing radiation, for instance, or to prevent unnecessary expenses on a more expensive exam when a simpler and more affordable one would suffice.


One of the most basic exams used, it involves a certain degree of ionizing radiation. It is used to observe bone structures, such as fractures (and their subsequent healing process), helps assess angulation, severity, and progression of scoliosis, can reveal joint instability, measure leg/thigh length (known as scannometry), and even provide an estimate of the patient's bone density (as a darker spinal X-ray indicates calcium loss in those bones). It may be necessary to conduct a bone density scan (densitometry) to confirm this.

Normal pelvis radiograph, cortesy of Dr Bruno Di Muzio,, rID: 38402.

CT Scan

Computed tomography is an imaging procedure that uses X-rays to create images of sectional segments, meaning body slices. It is a more advanced examination than X-rays and is accomplished through computer-generated image reconstructions, offering high precision and even the ability to display 3D images. It is used to observe bone fractures, blood vessels, and with the use of contrast, it can identify various types of lesions. It involves ionizing radiation in a higher dose compared to X-rays.

Pelvic 3D Computed Tomography. Courtesy of Dr. Varun Babu rID: 57318


It uses sound frequencies to generate images through the reflection of sound on tissues. It is an inexpensive exam and does not involve ionizing radiation, but it has some limitations and is less precise than other imaging exams. It cannot visualize bone marrow or bone tumors, but it can be used to observe muscles and superficial structures of the body. Additionally, it is a low-cost exam.

Ultrasonography of the metatarsophalangeal joint. Courtesy case by Dr. Maulik S Patel rID: 32235


It is a high-definition imaging exam that uses a magnetic field to temporarily "align" the electrons in the human body, creating a precise image of the organism. It is non-ionizing. It cannot be performed on pregnant individuals due to the movement of the fetus, which disrupts the electron "alignment" and hinders image formation. Metallic objects should be avoided, and the presence of metallic objects, plates, pins, jewelry, etc., should always be informed. It is excellent for observing meniscus injuries, herniated discs, and ruptures of tendons and ligaments.

Existem diversas modificações e alterações de contraste, saturação e carga radiológica que pode ser modificada de acordo com o que se está buscando com os exames além de diversos outros que podem ser solicitados. No Brasil os quiropraxistas tem autonomia para requerem esses exames, mas somente quando o paciente paga de forma particular. Os planos de saúde ainda não aceitam solicitações de quiropraxistas brasileiros, e acaba se sugerindo que o paciente peça ao seu médico de confiança essas solicitações, de modo que consiga usufruir dos benefícios do plano, como valores mais baixos ou até a isenção do pagamento de exames de imagem.

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