Image-guided radiation therapy (IGRT) represents a significant advancement in cancer treatment, utilizing sophisticated imaging techniques to deliver radiation with unparalleled accuracy. As a specialized form of radiation therapy, IGRT employs powerful energy beams, such as X-rays or protons, to precisely target and eradicate cancerous cells. The hallmark of IGRT lies in its use of high-quality imaging before and sometimes during each treatment session to meticulously plan and adapt the radiation delivery.
What is Image-Guided Radiotherapy (IGRT)?
At its core, image-guided radiotherapy (IGRT) is designed to enhance the precision and accuracy of traditional radiation therapy. Before each radiation session, and potentially during the session itself, advanced imaging scans are conducted. These images are not merely for visualization; they are integral to the treatment process. They allow the radiation therapy team to pinpoint the exact location, size, and shape of the tumor with remarkable clarity.
This imaging-centric approach is crucial because tumors can shift position within the body due to various factors, including breathing, movement, or changes in organ filling. IGRT addresses this challenge by comparing the newly acquired images with the initial treatment plan images. If any movement or changes are detected, the treatment plan and the patient’s positioning are meticulously adjusted in real-time to ensure the radiation beams are precisely directed at the tumor and minimize exposure to surrounding healthy tissues.
IGRT can incorporate various imaging modalities, including:
- 2D Imaging: Utilizing X-rays or fluoroscopy for basic visualization and alignment.
- 3D Imaging: Employing CT (Computed Tomography) scans, MRI (Magnetic Resonance Imaging), or PET (Positron Emission Tomography) scans to create a three-dimensional representation of the tumor and surrounding anatomy for more detailed planning and positional verification.
- 4D Imaging: Extending 3D imaging to include the dimension of time, 4D imaging, often using specialized CT scans, captures tumor movement due to respiration or other physiological processes. This is particularly valuable for treating tumors in the chest or abdomen.
By integrating these imaging technologies, IGRT ensures that radiation is delivered exactly where it is needed, adapting to the dynamic nature of the body and tumor position.
Why is IGRT Used in Cancer Treatment?
Image-guided radiotherapy (IGRT) has become a standard of care in radiation oncology due to its numerous advantages in treating a wide spectrum of cancers. Its precision targeting offers several key benefits:
- Enhanced Tumor Control: By delivering radiation more accurately to the tumor, IGRT can facilitate the use of higher radiation doses. This dose escalation can lead to improved tumor control and a greater likelihood of successful cancer eradication.
- Reduced Side Effects: The ability to precisely target the tumor minimizes radiation exposure to healthy tissues and critical organs located nearby. This reduction in unnecessary radiation exposure translates to fewer and less severe side effects for patients.
- Treatment of Tumors in Motion: IGRT is particularly beneficial for treating tumors that are prone to movement, such as those in the lungs, liver, or prostate. The real-time imaging and adaptive capabilities of IGRT ensure accurate radiation delivery despite tumor motion.
- Treatment of Tumors Near Sensitive Structures: For cancers located close to vital organs or sensitive structures like the spinal cord, optic nerves, or heart, IGRT’s precision is paramount. It allows radiation oncologists to deliver therapeutic doses to the tumor while minimizing the risk of damage to these critical areas.
- Shorter Treatment Schedules: In some cases, the increased effectiveness of IGRT may allow for shorter overall treatment schedules, improving patient convenience and reducing the duration of treatment-related side effects.
IGRT is employed to treat virtually all types of cancer and is sometimes used to manage benign tumors as well. Its adaptability and precision make it a versatile tool in modern radiation oncology.
Understanding the Risks and Side Effects of IGRT
While image-guided radiotherapy (IGRT) is designed to minimize side effects compared to traditional radiation therapy, some side effects are still possible. The specific risks and side effects depend on the location of the treatment and the radiation dose administered.
| Part of body being treated | Common side effects |
|---|---|
| Any part | Hair loss at the treatment site (which can be permanent), skin irritation at the treatment site, fatigue |
| Head and neck | Dry mouth, thickened saliva, difficulty swallowing, sore throat, changes in taste, nausea, mouth sores, tooth decay |
| Chest | Difficulty swallowing, cough, shortness of breath |
| Abdomen | Nausea, vomiting, diarrhea |
| Pelvis | Diarrhea, bladder irritation, frequent urination, changes in sexual function |
It’s important to note that many side effects are manageable during treatment and often subside after the completion of therapy. However, some late side effects can develop months or years after treatment. In very rare instances, radiation therapy may contribute to the development of a secondary cancer later in life. Patients should have open discussions with their radiation oncology team about potential short-term and long-term side effects relevant to their individual treatment plan.
Preparing for Image-Guided Radiotherapy (IGRT)
The journey to image-guided radiotherapy (IGRT) begins with a consultation with a radiation oncologist, a doctor specializing in using radiation to treat cancer. During this initial meeting, the radiation oncologist will evaluate your case, discuss whether IGRT is appropriate for your specific cancer type and stage, and answer any questions you may have.
If IGRT is determined to be the right course of treatment, a meticulous planning process will commence. The radiation therapy team, including dosimetrists and radiation therapists, will work collaboratively to develop a personalized treatment plan. This planning phase involves:
- Imaging for Treatment Planning: The team will select the most suitable imaging techniques (2D, 3D, or 4D) to precisely delineate the tumor and surrounding healthy tissues. These images serve as the blueprint for radiation delivery.
- Simulation Session: You will undergo a simulation session, which is a mock setup of your actual treatment. During simulation, you will be positioned on the treatment table, and immobilization devices (like masks or molds) may be created to ensure consistent positioning during each treatment session. The imaging scans for treatment planning are typically acquired during the simulation.
- Treatment Plan Development: Using sophisticated software, the radiation oncology team will design a detailed treatment plan. This plan specifies the radiation dose, beam angles, and techniques to maximize radiation to the tumor while minimizing exposure to healthy tissues.
This comprehensive preparation phase is crucial to ensure the safe and effective delivery of IGRT.
What to Expect During Your IGRT Sessions
During each image-guided radiotherapy (IGRT) treatment session, you can expect a similar process. Upon arrival for your appointment, you will be positioned on the treatment table, often using the immobilization devices created during simulation to ensure accurate and reproducible positioning.
Before the radiation is delivered, imaging scans will be performed. These on-treatment images are then compared to the planning images to verify the tumor’s position. This comparison allows the radiation therapy team to:
- Verify Patient Positioning: Confirm that you are positioned identically to the simulation setup.
- Assess Tumor Position: Determine if the tumor has shifted or moved since the initial planning scans.
- Make Real-time Adjustments: If any discrepancies are detected, the team will make minute adjustments to your position and/or the treatment plan to ensure the radiation beams are precisely targeted at the tumor.
The actual radiation delivery is typically painless and lasts only a few minutes. You will be alone in the treatment room during radiation delivery, but you can communicate with the radiation therapists via intercom at any time. The entire session, including imaging and setup, usually takes between 15 to 30 minutes.
Results and Follow-up After IGRT
Following image-guided radiotherapy (IGRT), your radiation oncology team will monitor your progress and assess the effectiveness of the treatment. Follow-up appointments are typically scheduled regularly to:
- Monitor for Treatment Response: Imaging tests, such as CT scans, MRI scans, or PET scans, will be used to evaluate whether the tumor is shrinking and responding to the radiation therapy.
- Manage Side Effects: The team will assess and manage any side effects you may be experiencing.
- Assess Overall Health: Your general health and well-being will be monitored.
The timeline for seeing the results of IGRT can vary. In some cases, tumors may respond quickly, while in others, it may take weeks or months to observe a noticeable response. Your radiation oncologist will discuss the expected timeline and follow-up plan based on your individual situation. Long-term follow-up care is essential to monitor for any late side effects and ensure your continued well-being after treatment.
References:
- Tepper JE, et al., eds. Intensity-modulated and image-guided radiotherapy. In: Gunderson & Tepper’s Clinical Radiation Oncology. 5th ed. Elsevier; 2021. https://www.clinicalkey.com. Accessed Jan. 16, 2023.
- Image-guided radiation therapy (IGRT). RadiologyInfo.org. https://www.radiologyinfo.org/en/info/igrt. Accessed Jan. 16, 2023.
- Accredited facility search. American College of Radiology. https://www.acraccreditation.org/accredited-facility-search. Accessed Jan. 16, 2023.
- Nguyen H. Allscripts EPSi. Mayo Clinic. May 5, 2022.
- Radiation therapy and you: Support for people with cancer. National Cancer Institute. https://www.cancer.gov/publications/patient-education/radiation-therapy-and-you. Accessed Nov. 6, 2024.
- Mitin T. Radiation therapy techniques in cancer treatment. https://www.uptodate.com/contents/search. Accessed Nov. 6, 2024.
