What is the difference between 2D, 3DCRT, IMRT, and IGRT?

Depending on the specific type of cancer a patient is diagnosed with, they can choose from several types of cancer treatments. Radiotherapy, also known as radiation therapy, is one such treatment. This treatment uses high-intensity radiation to kill cancer cells by breaking down their genetic material. Although radiation therapy can damage healthy cells, they can repair themselves better than cancer cells. The treatment may take several days or weeks to inflict enough damage to the DNA to effectively kill the cancer cells.

A variety of radiation treatments are available, including 2D Radiation Therapy (2D), 3D conformal radiation therapy (3DCRT), Intensity-modulated radiation therapy (IMRT), and Image-guided radiation therapy (IGRT). These types of radiation are typically used to treat cancers that affect organs near the surface. While these therapies share the same goal, there are significant distinctions among them. Let’s explore the differences in radiation treatments.

2D radiation therapy

2D radiation therapy is rooted in traditional methods. It is a type of radiation therapy in which treatments are scheduled based on a finite number of beams, with the parameters being determined by the patient’s orthogonal X-rays. CT scans don’t provide 3D imaging, so they cannot be used to plan this kind of treatment. This type of treatment is suitable for emergency situations. 2D radiotherapy employs square or rectangular radiotherapy beams due to the challenges involved in shaping the beam.

How does it work?

The 2D radiation treatment process can be completed in a relatively short amount of time. The fluoroscopic simulator is a device used for this treatment, utilising X-rays to identify the location of the patient’s bones. These bones are then used as reference points to determine the tumour’s location, aiding in locating the radiation beams required for the treatment. The size and structure of the tumour can be visualised on 2D X-ray films, which are subsequently used during the treatment.

3D Conformal Radiation Therapy (3DCRT)

3D conformal radiation is a form of radiotherapy that employs CT scans and computer technology to generate a 3D scan of the tumour. The machine then utilises the 3D model as a guide to direct radiation beams at the cancer site, minimising the impact on surrounding tissue. Through the use of 3D scans, 3DCRT accurately measures the size and structure of the tumour, achieving precise alignment with the tumour. This treatment has demonstrated success in treating various cancers, including those in the brain, head, and neck, providing a precise match to the tumour.

How does it work?

Patients typically undergo a Comprehensive Care (CT) scan to generate a 3D image, which is subsequently used to formulate their radiotherapy plan. Additionally, they might undergo a Magnetic Resonance Imaging (MRI) or a PET scan. The data from these scans is directly input into a radiotherapy planning computer, enabling the treatment team to design the treatment area in three dimensions. The computer program then generates radiation beams that closely follow the tumour’s contours, ensuring its full coverage within the radiotherapy field, while minimising the exposure of healthy tissue. This approach reduces the risk of adverse side effects. The radiation beams consist of small metal leaves arranged to conform to the tumour’s shape.

Intensity-modulated radiation therapy (IMRT)

This form of radiation is typically employed when the tumour is located in close proximity to surrounding normal tissues. It involves delivering multiple beams of radiation to target the tumour. This approach is suitable when the tumour is in close proximity to adjacent healthy tissues. Physicians use special planning software to minimise the radiation dose to the surrounding tissues. IMRT is a more sophisticated form of radiation treatment that uses a higher dose of radiation to target the tumour and a lower dose to target healthy tissue.

How does it work?

An individual can receive Intensity-Modulated Radiation Therapy (IMRT) using a conventional radiotherapy machine known as a Linear Accelerator (LINAC). The machine is equipped with a multilayered collimator, composed of thin layers of lead that can be independently moved. When these lead layers are in motion, the machine rotates around the patient and directs a radiation beam precisely at the tumour. Each radiotherapy beam is made up of numerous small beamlets, which can have their intensity adjusted to deliver varying doses of radiation across the tumour.

Image-guided radiation therapy (IGRT)

IGRT is a type of External Beam Radiation Therapy (EBRT) where the radiation machine acquires a low-dose X-ray or mini CT scan before each treatment. This scan aids in aligning the treatment site, resulting in more precise radiation delivery. This radiation treatment is employed to treat cancers in organs and tissues that experience movement. It detects the tumour’s presence or implanted markers during the radiation treatment. Cancers affecting the prostate, liver, lung, pancreas, as well as those occurring in tissues and vital organs, can all be treated using this method.

How does it work?

Patients receive these scans while seated on a radiotherapy couch before the start of their treatment. Radiographers may adjust the design or position of the radiotherapy couch after reviewing the X-rays and scans to ensure that the patient is positioned within a millimetre of the planning scan. In some instances, an X-ray or scan is conducted immediately after the treatment. X-rays reveal bones in the treated area, while scans display the size, contour, and location of the cancer, as well as the surrounding tissues and bones.

What is the difference between 2D, 3DCRT, IMRT, and IGRT?

In the past, 2D radiation was administered in two or four directions, and most of the patients who recovered experienced dry mouths. Additionally, the spinal cord and jawbone were subject to various adverse reactions. To address these issues, 3D CRT was developed, reducing the dose to only a fraction of the pre-existing parotid gland and other important organs. The smaller beams sent in different directions enabled this alteration, and the preparation for both treatments was meticulous.

3DCRT significantly reduced the adverse effects on the parotid gland, spinal cord, and jawbone. IMRT, a computerised and automated technique, enabled concavity, in which more than 100 beams were delivered during the prescribed treatment. When a critical organ was in the path of radiation, the computer turned off the radiation.

In IMRT, two frontal X-rays and a side X-ray are taken, respectively, and the table is adjusted to a precise position before administering the treatment while the patient is asleep on the table. In IGRT, a CT scan is obtained using the treatment machine, and the position is corrected to a precise level before the treatment is performed. The purpose of this CT scan is to accurately position the patient and detect important details; it is not intended to evaluate subtle changes in cancer response.

IMRT/IGRT is administered through devices such as Tomotherapy, TrueBeam (STx), or VMAT (Volumetric Modulated Arc Therapy), significantly reducing the adverse reactions associated with these types of treatments

3DCRT has several distinct features compared to IMRT/IGRT, while IMRT or IGRT only have a few differences. Apollo Cancer Centre stands as the new destination for world-class cancer treatment, offering a multi-disciplinary approach, cutting-edge technology, and top-notch expertise. Our oncology team comprises a select group of the most highly-regarded Cancer Care specialists. The doctors at Apollo Hospitals Karnataka examine the patient’s medical history, pathology reports, and imaging studies to determine the most suitable radiation treatment. Since each treatment plan is tailored to the individual patient, it is essential to consult the doctor regarding the specific radiation treatment options before commencing treatment.