Difference Between Radiotherapy and Radiodiagnosis

Difference Between Radiotherapy and Radiodiagnosis: Radiotherapy and Radiodiagnosis are different within the field of medical radiation. Radiotherapy consists of the targeted use of high-energy radiation to beat cancer by eradicating malignant cells or reducing tumour size while preserving healthy tissue integrity. On the other hand, Radiodiagnosis includes employing various imaging modalities, such as X-rays, CT scans, and nuclear medicine, to visualize internal anatomical structures for diagnostic purposes, aiding in the detection and characterization of diseases, injuries, and other medical conditions. 

Difference Between Radiotherapy and Radiodiagnosis

Radiotherapy involves high-energy radiation to treat cancer, and Radiodiagnosis uses imaging techniques like X-rays and CT scans for disease detection and diagnosis. The table below provides the differences between Radiotherapy and Radiodiagnosis.





Treats diseases, primarily cancer, by delivering targeted radiation doses to destroy or shrink tumours.

Diagnoses diseases and conditions by visualizing internal structures of the body using medical imaging techniques.

Medical Professionals

Radiation oncologists, medical physicists, and radiation therapists.

Radiologists, radiologic technologists.


Linear accelerators, brachytherapy devices, and stereotactic radiosurgery systems.

X-ray machines, CT scanners, MRI machines, ultrasound devices, nuclear medicine cameras.

Patient Preparation

Involves immobilization devices, treatment planning sessions, and contrast agents for certain treatments.

It may involve fasting before imaging scans, contrast agents administration, and specific instructions for different types of imaging.


Aims to treat or manage diseases, often to eradicate or control cancer.

Aims to accurately diagnose conditions or diseases, guiding further treatment decisions.

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What is Radiotherapy?

Radiotherapy which is also known as radiation therapy, is a medical treatment that uses high-energy radiation to destroy cancer cells or shrink tumors. It is an important part of the management of cancer and is often used as a primary treatment. 

Features of Radiotherapy

  • Targeted Treatment: Radiotherapy particularly targets cancer cells while not harming the surrounding healthy tissue, minimizing collateral damage.
  • Customised Approach: Treatment plans are different for each patient with different conditions, considering factors such as tumour type, size, location, and individual health.
  • Multidisciplinary Collaboration: Radiotherapy often involves collaboration among radiation oncologists, medical physicists, dosimetrists, and radiation therapists to ensure comprehensive care.
  • Diverse Modalities: Various techniques such as external beam radiation therapy, brachytherapy, and stereotactic radiosurgery offer flexibility in delivering radiation to tumours.

What is Radiodiagnosis?

Radiodiagnosis also known as diagnostic radiology or medical imaging, is a field of medicine focused on using various imaging techniques to diagnose diseases, injuries, and other medical conditions. It involves the interpretation of images produced by modalities such as X-rays, computed tomography (CT), magnetic resonance imaging (MRI), ultrasound, and nuclear medicine scans.

Features of Radiodiagnosis

  • Non-Invasive Imaging: Radiodiagnostic procedures are non-invasive, which means they do not require surgical intervention. This reduces patient discomfort and the risk of complications associated with invasive procedures.
  • Visualization of Internal Structures: Radiodiagnosis allows healthcare professionals to visualize internal anatomical structures, organs, and tissues, providing valuable insights into the presence, location, and extent of diseases, injuries, or abnormalities.
  • Diverse Imaging Modalities: Radiodiagnostic techniques include X-rays, computed tomography (CT), magnetic resonance imaging (MRI), ultrasound, and nuclear medicine scans, each offering unique advantages in terms of resolution, contrast, and application.
  • Diagnostic Accuracy: Radiodiagnosis helps in getting accurate and timely diagnoses, which provides appropriate treatment planning and patient management.

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Similarities between Radiotherapy and Radiodiagnosis

  • Ionizing Radiation: Both Radiotherapy and Radiodiagnosis use ionizing radiation. This includes X-rays, gamma rays, and other high-energy particles.
  • Medical Imaging: Both Radiotherapy and Radiodiagnosis use medical imaging techniques to visualize the internal structures of the body. Whereas Radiotherapy uses imaging to precisely target tumours and determine treatment plans, Radiodiagnosis employs imaging to diagnose diseases and conditions.
  • Equipment: Both fields use similar machines such as X-ray machines, CT scanners, and MRI machines. These machines are essential for generating images of the body's internal structures.

In summary, while both Radiotherapy and Radiodiagnosis involve the use of radiation, they offer different purposes. Radiotherapy is primarily used for cancer treatment, aiming to destroy cancer cells, while Radiodiagnosis is used for diagnostic purposes, aiming to visualize internal structures and identify diseases or abnormalities.


What is Radiotherapy?

Radiotherapy, also known as radiation therapy, is a medical treatment that uses ionizing radiation to target and destroy cancer cells.

What is Radiodiagnosis?

Radiodiagnosis is the use of medical imaging techniques, such as X-rays, CT scans, and MRI scans, to diagnose diseases and conditions by visualizing internal structures of the body.

How does Radiotherapy work?

Radiotherapy works by delivering targeted doses of radiation to the tumour site. This radiation damages the DNA of cancer cells, causing them to die or become unable to multiply.

What are the common types of Radiotherapy?

Common types of Radiotherapy include external beam radiation therapy (EBRT), brachytherapy, and stereotactic radiosurgery (SRS).

What conditions can be treated with Radiotherapy?

Radiotherapy is commonly used to treat various types of cancer, including but not limited to breast cancer, lung cancer, prostate cancer, and brain tumours.