imaging technology- imaging sensors, CT, nuclear medicine Flashcards
What is imaging in radiotherapy often called?
Image-Guided Radiotherapy
What is Image-Guided Radiotherapy?
A technique used in cancer treatment that integrates imaging technologies with radiation therapy to improve the precision and accuracy of radiation delivery
How does IGRT help clinicians target tumors more accurately, minimize radiation exposure to healhty tissues and adapt treatment plans based o changes in tumour size or position during treatment?
By obtaining real-time or near-real time images of a patient’s tumour and surrounding anatomy
What are the common imaging modalities used in IGRT?
Computed tomography (CT), magnetic resonance imaging (MRI), and X-ray imaging
The simulation/planning CT
The patient is first positioned on a CT scanner table.
Immobilization devices, such as headrests, masks or body molds are used to immobilize the patient during the CT simulation
A CT scan is obtained, capturing the tumor and surrounding anatomical structures
Which step of the radiotherapy treatment plan does the Simulation/ CT planning take part in?
Planning stage
target delineation
Using the CT scans, the radiation oncologist outlines the Gross Tumor Volume and the Clinical Target volume + delineate critical organs and healthy tissues Organs at Risk, to minimize radiation exposure to these structures
What is the difference between the Gross Tumor Volume and the Clinical Target Volume?
The gross tumor volume is the target tumor volume
Clinical target volume is the areas that are at risk for microscopic disease spread
What are the 3 delineations taking place in target delineation?
gross volume target delineation
clinical volume target delineation
organs at risk delineation
PET Imaging
used for tumor delineation (gross tumor volume)
How can PET images help the radiation oncologists?
accurately define the tumor’s boundaries, Gross Tumor Volume
and identify potential areas of microscopic disease spread, Clinical target volume
and identify potential regions of high-risk within the tumor, such as hypoxic regions
What is a hypoxic regions?
regions within the tumor which are high-risk
How can PET imaging be used to identify hypoxic regions within tumors?
by employing specific radiotracers that selectively accumulate in hypoxic tissues. The treatment plan can then be designed to deliver a higher radiation dose to these hypoxic regions (regions of higher risk of microscopic disease spread within the tumor), while maintaining a standard dose for well-oxygenated regions.
Different imaging techniques to diagnose tumors
X-ray, CT, MRI, PET, Ultrasound
How do x-rays help in diagnostic imaging?
the first imaging test performed when cancer is suspected. Uses ionizing radiation to create 2D images of the body’s internal structures
How does CT help in diagnosis of cancer?
diagnose the stage of many types of cancer, and help guide biopsies and monitor the response to treatment
How is MRI useful for diagnosis of cancers?
Diagnosing and staging cancers in areas with complex anatomy, such as brain, spinal chord, prostate, and breast cancer
How is PET useful for diagnosis of cancer?
Due to the fact that cancer cells often have higher metabolic rates than normal cells, PET scans are used for diagnosing and staging various types of cancers
How is ultrasound helpful in diagnosing and staging cancers?
useful to diagnose and stage cancers in organs such as the liver, pancreas and kidneys. Can also help guide biopsies and monitor treatment response
What is fractionation?
Dividing radiation therapy into smaller doses, called fractions, which are delivered over a period of time
Why is fractionation an essential aspect of radiotherapy treatment planning?
it allows for the delivery of a high total radiation dose to the tumour while minimizing damage to surrounding healthy tissues.
What is the rationale behind fractionation?
Based on the different responses of cancer cells and normal cells to radiation, allowing for the preferential killing of cancer cells while giving normal tissues time to recover between fractions.
What happens in conventional fractionation?
The total radiation dose is divided into small fractions, typically ranging from 1.8 - 2 Gy/ fraction, delivered daily over several weeks
What does the number of fractions and thte total treatment duration depend on?
The type and stage of cancer, as well as the patient’s overall health
What is the main concept of radiotherapy delivery and related imaging?
Radiotherapeutic dose can be delivered via many routes, generally categorized in internal or external radiotherapy.
What is internal radiotherapy?
a radioactive material is placed directly into or near the tumour
How is interal radiotherapy useful?
Allows for the delivery of high radiation doses to the cancer cells while minimizing exposure to surrounding healthy tissues
What imaging technique is typically used in internal radiotherapy/ brachytherapy?
ultrasound imaging
How is ultrasound imaging used in internal radiotherapy, or brachytherapy?
used to guide the placement of the radioactive seeds, particularly for prostate and gynecological brachytherapy
What is external radiotherapy?
a form of cancer treatment in which radiation is directed from an external machine towards the tumour within the patient
In conventional therapy, how is the radiation in external radiotherpy generated?
A machine: linear accelerator, which produces high-energy X-rays or particles
What do most LINAC come with?
Kilovoltage and megavoltage imaging for patient positioning
Why is KV x-ray imaging used before treatment delivery?
To verify patient positioning and ensure accurate radiation targeting (part of the treatment planning)
What does kV imaging typically involve?
Acquiring 2D or 3D images, such as planar radiographs or cone-beam CT scans
What are the planar radiographs or cone-beam CT scans compared to?
the reference images obtained during the plannig phase
How does kV imaging help the treatment team?
Make any necessary adjustments to the patient’s position or treatment plan to account for changes in tumor size or shape or patient anatom
What is MV imaging?
Another modality used during external radiotherapy to verify patient positioning and monitor treatment accuracy.
What does MV imaging use?
The treatment beam itself to generate images, by acquiring planar radiographs or volumetric images
What are the images obtained in MV imaging vs those obtained in kV X-ray imaging ?
kV: planar radiographs or cone beam CT scans
MV: planar radiographs or volumetric images
what is MV imaging particularly useful for?
monitoring the treatment of deep-seated tumors or when kV imaging is not available or sufficient for accurate patient positioning
Advantage of MV over kV
MV can be used when kV imaging is not availbale or sufficient for accurate patient positioning
Disadvantage of MV
Due to proton physics property at MeV, it is generally of poor quality
What is surface guided imaging?
A modern external radiation therapy technique that uses non-invasive, real time surface imaging to monitor the patient’s external surface during treatment
How is surface guided imaging useful?
It improves patient positioning accuracy, ensures proper alignment, and verifies motion management during radiotherapy
What does surface guided imaging ultimately enhance?
The precision of radiation delivery to the target tumor, while minimizing the dose to surrounding healthy tissue
What does surface guided imaging use?
3D camera systems and advanced software to capture patient’s external surface.
Camera systems use optical, non-ionizing radiation to create a 3D surface map
What is the 3D map produced during surface guided imaging compared to ?
the patient’s reference surface obtained during the simulation phase, via CT, PET, Ultrasound, X-ray (all the different imaging modalities)
What is a gamma knife?
A form of stereotactic radiosurgery that utilises highly focused gamma radiation to treat brain tumors
What type of treatment option does gamma knife provide?
non-invasive
What are the properties of the dose of radiation delivered by a gamma knife?
A high dose of radiation to a precise target within the brain while minimizing exposure to surrounding healthy tissue.
What plays a crucial role in Gamma Knife treatment?
Imaging
How does imaging play a crucial role in Gamma Knife treatment?
it helps define the target volume (gross target volume, clinical target volume ), plan the treatment, and ensure accurate radiation delivery
How is in-treatment imaging avoided in Gamma-Knife stereotactic surgery?
through the use of a stereotactic frame attached to the patient’s head using local anesthesia.
What does the stereotactic frame attached to the patient’s head with local anesthesia help provide?
A fixed reference system that allows for precise localization and targeting of the lesion during treatment.
What happens after the stereotactic frame is placed on the patient’s head?
the patient undergoes imaging studies with the frame visible in the images. The images are then used for treatment planning.
