Difference Between Bone Scan and MRI

Disease diagnosing can be tedious if we didn’t have access to amazing diagnostic tests/ scans like CT scans, MRI, Bone Scan, etc. But some of these can baffle us and create confusion about which one to go. One such uncertainty is caused by Bone Scans and MRI. People often tend to assume that they are the same but they are not. 

Bone Scan vs MRI  

The main difference between Bone Scan and MRI is that Bone Scan is majorly focused on bone diseases or conditions like bone cancer, bone infections, or minute fractures which are not perceived in the X-Ray, while MRI helps in deep diagnosis by producing images of bone as well as the internal anatomy like the tendons, ligaments surrounding the bone.   

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Bone Scan or Bone Scintigraphy involves nuclear medicine imaging methodology wherein a radioactive material is injected into the body which produces gamma rays, which in turn are captured by an imaging device(camera) thus generating images or scintigrams. Bone Scan usually produces two-dimensional (2D) images.   

MRI, on the other hand, stands for Magnetic Resonance Imaging. It involves 3-dimensional (3D) imaging using strong magnetic fields. MRI scanners generate detailed and deep images of the physiology and anatomy of any internal organ, thus providing a precise and deep diagnosis of any disease or infection. MRI is generally considered as safer than any other tests/ scans.  

Comparison Table Between Bone Scan and MRI  

Parameters of Comparison    Bone Scan    MRI     
Rays/ Fields used    Radioactive-gamma rays  Strong Magnetic Fields, Radio Waves  
Image Generated    2-dimensional    3-dimensional and 2-dimensional   
Invented By  George De Hevesy (1930s)  Raymond Damadian (1970s-1980s)  
Risk Factor    For pregnant and breastfeeding women    No threat to pregnant women  
Specificity    Peculiarly Bone   Any anatomical internal organ    

What is a Bone Scan?  

As mentioned above, a Bone Scan is a scan specifically targeted to understand and know bone-related infections and diseases. It is popularly known as skeletal scintigraphy. Diagnosis of bone scan may assist in treating numerous disorders like bone cancer and metastasis, osteoblasts, minute fractures which are not visible under normal X-ray, osteoporosis, arthritis, etc.   

Under Bone Scan patients are administered with radioactive substances like radiopharmaceutical or radiotracer which in turn produce gamma rays which are then processed into images by the imaging device. These images are labeled scintigrams. These scintigrams highlight the fragment where the radioactive substance is accumulated.   

Usually, in absence of bone disorder, the radioactive substance should be distributed evenly in the entire body. But in presence of disease, these scintigrams highlight dark/ hot spots thus locating the affected segment of the bone.   

Bone Scan usually helps in the early detection of the disorder as it pinpoints one particular area. Patients with medications, allergy or vitamin supplements are advised to consult their physician. After the scan patients are usually advised to drink plenty of fluids to flush out the radioactive toxins from the body. Patients are usually asked to wait after injecting the radiotracer before undergoing the scan. Bone scan to date emerges to be one of the safest options of scan leaving no side effects or risks.   

If the ailment is not identified on the first go, physicians generally advise the bone scan to be redone. In some cases, a bone scan is followed by SPECT (Single-photon emission computed tomography), SPECT provides 3-Dimensional images thus enhancing the results of bone scan.  

What is MRI?   

MRI or Magnetic Resonance Imaging is an imaging technique used to generate images depicting the physiology of deep internal organs. MRI helps in the timely detection and diagnosis of massive disorders involving every part of the body. It is no incision high-level analysis test that is considered to be the safest option.  

MRI can be of numerous types like with or without contrast medium, closed MRI, open MRI, standing or sitting MRI. The one with the contrast medium (usually gadolinium) guarantees better results and images compared to the no-contrast medium. MRI is never specific; it assists in diagnosing ailments from the entire body encompassing any muscle, tissue, ligament, etc.   

The only specific MRI is the fMRI- Functional Magnetic Resonance Imaging, which equips in detecting brain-related disorders as they produce images from any part of the brain. Often, they also detect Alzheimer’s. MRI usually does not involve ionizing radiations thus distinguishing it from other diagnostic tests.   

Patients undergoing MRI are appealed to lay down on the tube-like magnetic machine. The magnetic and radio waves track and trace the water or hydrogen molecules in the body and these atoms, in turn, produce light/ faint waves or signals which are processed into cross-sectional images. MRI also produces 3-dimensional images.   

MRI is considered the safest, the exception being that there should be not a single piece of metal attached to your body due to the presence of strong and mighty magnets. MRI is painless and carries zero side effects.  

Main Differences Between Bone Scan and MRI  

  1. Bone Scan or Bone Scintigraphy is a specific diagnostic test targeted particularly for the bone, whereas MRI or Magnetic Resonance Imaging is a complete body diagnostic test.   
  2. Bone Scan typically generates 2-dimensional images, on the other hand, MRI can generate both 2-dimensional as well as 3-dimensional images.  
  3. Bone Scan involves radioactive imaging while MRI involves magnetic imaging.  
  4. Bone Scans can detect osteoporosis, osteoblasts, bone cancer, bone fever, on contrast MRI can detect congenital heart disease, prostate and breast cancer, soft tissue tumors, etc.  
  5. Pregnant women are advised to consult doctors before undergoing a Bone Scan, while MRI possess no threats to pregnant or breastfeeding women.   
  6. Bone Scan involves the injection of radiotracer while MRI does not involve the injection of any radioactive substance.   

Conclusion 

From the above-mentioned points, it is clear that even though both Bone Scans and MRI appear the same they are intrinsically different. A bone Scan is a bone-targeted test while MRI is a full-body test. Bone Scan detects bone infections while MRI can detect any infection even related to bones of the spinal cord or CNS. Thus, MRI is more accurate than Bone Scan.   

MRI does not carry the radioactive side-effects while Bone Scintigraphy can sometimes lead to minor side-effects like headache, dizziness especially in pregnant women. Nevertheless, both Bone Scan and MRI have manifested to be the safest and best test options in modern times.   

References  

  1. https://www.sciencedirect.com/science/article/pii/S0001299811000961  
  2. http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.829.7053&rep=rep1&type=pdf  
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