Simulation and Imaging

imaging for treatment planning and imaging for guidance and verification

What are the two categories of imaging in radiation therapy?

imaging for treatment planning

What type of imaging is used to define targets and OARs, it is also used to select dosimetric geometric parameters such as isocenter location and treatment beam angles

conventional and three-dimensional

What imaging modalities are used for treatment planning?

conventional

_____________ imaging includes general radiography and fluoroscopy

conventional simulator

a _____________________ is a device that mechanically simulates the behavior of a linac; they have a gantry and a couch

False, conventional simulators being used for simulation has almost completely disappeared

T/F: Conventional simulators are very common during simulation

three dimensional imaging

What type of imaging includes anatomical imaging and functional imaging?

anatomical

_____________ imaging shows anatomy the best and allows us to see soft tissues; we use this to outline soft tissues so we can view OAR and tumor margins where we are treating

-MRI

-Ultrasound

-CT

-4DCT

What types of scans are involved with anatomical imaging?

functional

_____________ imaging displays physiology such as glucose metabolism and allows you to see the functionality of certain organs

-PET

-SPECT

-fMRI

What types of scans are involved with functional imaging?

spatial resolution

refers to the ability to display separate images of objects that are close together

True

T/F: 3D imaging options provide the spatial resolution necessary to discriminate between various types of soft tissues as well as bone and air cavities

MRI

_____ provides the highest spatial resolution and is widely used as an adjunct to CT in localizing treatment volumes, particularly in the brain

ultrasound

_______________ imaging is based on the propagation and reflection properties of sound at tissue interfaces

treatment planning for prostate brachytherapy implants and for position verification (primarily external beam prostate therapy)

What is ultrasound imaging used for?

CT

__________ is most commonly used for treatment planning; they are spatially accurate and are not subject for treatment planning

False, CT displays a high resolution compared to PET

T/F: CT display a low resolution, compared the PET

density

The electron _________ can be derived from the CT number, provided that calibration is applied

electron density is essential in calculating Compton scattering and it allows us to figure out how the beam will interact with the tissue

Why do we care about knowing electron density?

Compton Scattering

What is the dominant photon interaction at megavoltage therapy energies?

4D CT

refers to three dimensions plus a time dimension and is used to track anatomical motion associated with respiration

accurately delineate target volumes and to reduce the amount of normal tissue treated

What is the goal of 4D CT?

-prospective gating imaging

-retrospective correlation imaging

What are the two types of 4D imaging?

patients chest

Where is the monitor placed on the patient during 4D imaging?

prospective gated imaging

_______________________ scans require the patient to hold their breath at either maximum inspiration or maximum expiration while an axial scan is acquired; the patient resumes breathing and the couch is moved in, the patient then holds their breath again until the scan is complete

retrospective correlation

during _________________ imaging, the patient breathes freely during a slow scan while the patient moves through the scanner; this allows the imaging of all portions of the anatomy through several respiratory cycles

bins

During retrospective correlation imaging the respiratory cycle is divided into ______

phase binning

_______________ divides the respiratory cycle into equal intervals or amplitudes of time during retrospective correlation imaging

True

T/F: CT slices are arranged in groups according to their bin, with each bin representing a different phase of the patient's breath cycle

functional

_____________ imaging shows the location and strength of physiological activity at the cellular and molecular levels

-improve disease detection

-cancer staging

-treatment planning to avoid higher functioning areas of OAR

-response to therapy

-early detection of recurrence

There are numerous ways that functional imaging can be used in planning and diagnosis, what are they?

Digitally Reconstructed Radiographs (DRRs)

a plane film radiograph, such as produced with a conventional simulator, provides a beam's eye view but not 3D-information

False, CT provides axial slices but NOT a beams eye view

T/F: CT provides axial slices and a beam's eye view

voxel

In a DRR, the data contained in the CT record has information on the linear attenuation coefficient of each _______

True

T/F: After receiving data containing linear attenuation coefficients of each voxel, it is possible to reconstruct a beam's eye view projection for any treatment port

DRR

A ________ is constructed from digital CT data and is a simulated radiograph used for comparison of port films

-dosimetric accuracy

-positional accuracy

What two factors must be considered to ensure RT is delivered efficaciously?

positional accuracy

What type of accuracy is assessed with imaging on the treatment machine?

-Portal images

-IGRT

-CBCT

-OBI

What modalities are used to assure positional accuracy?

portal images

_________________ are projection images made using MV beams projected onto either film or electronic portal imaging devices

targeting

Portal images are compared with DRR's to verify ____________

-bony anatomy

-air cavities

What are used to establish landmarks for comparison in portal images?

orthogonal pair

What type of image can be used to assure location in 3 dimensions?

False, MV image quality if poor compared to KV

T/F: KV imaging is poor compared to MV image quality

IGRT

__________________ uses KV energy to image soft tissue or implanted markers for positioning

IGRT

____________________ provides 3 dimensional target data not captured with conventional MV imaging and the location of the target can be compared with the expected location, the patient can be moved to align directly to the target as well

CBCT

_________________ is a 3D imaging technique used with an OBI, a device on a linear accelerator for IGRT

OBI

_______ can be used for fluoroscopic imaging and single shot imaging (orthopair)

simulation

______________ is the process of positioning a patient for a scan in the most practical and reproducible way possible; during this we obtain imaging for treatment planning

to gather all relevant planning data and to create a patient position that is reproducible on the treatment unit

What is the goal of SIM?

True

T/F: The more reproducible the SIM setup, the greater the likelihood that this position is reproduced daily on the treatment machine and the higher the likelihood that daily treatment will accurately represent the dosimetric planning

this ensures that targets receive the prescribed dose and the organs at risk do not exceed their dose limits

Why is it important that daily treatment is accurately represented in the dosimetric planning?

accurate

____________ treatment begins with quality simulation

before, patient anatomy

Proper alignment _________ simulation is important for daily pt set up and reproducibility. This can be done initially using ___________ ___________

positioning

____________ aids facilitate the consistent setup of the pt but don't necessarily immobilize the pt

thorax, breast, and belly board, head rests, knee cusion

What are some examples of positioning aids?

immobilization

____________ devices help establish and maintain position and keep the pt from moving during tx

thermoplastic mold, bite block, alpha cradle, vac-lock

What are some examples of immobilization devices?

comfort

patient __________ helps to aid in reproducibility, ensuring consistent daily set up and limiting movement during tx

smaller

the more accurate the setup, the _________ the expansion margins required during GTV/CTV expansion to PTV

4DCT, breath hold

___________ and ________ _______ devices can account for the internal motion of a pt during tx

SDX and ABC

What are two devices and software that facilitate breath hold tx?

inhalation

breath hold limits the treatment to a single phase of the breath cycle, typically the ___________ phase

alignment

seed markers can be surgically implanted in the target before simulation as an _____________ tool with daily imaging

radiofrequency beacons

there are processes in which ____________ ___________ are implanted into the target and are used to ensure daily tx accuracy

True

T/F: Radiofrequency beacons are located by the hardware, and the software controls when the beam turns based on the location determined by the location of target beams

conventional

_____________ simulation is the process of creating a tx plan without the use of modern 3D imaging techniques

isodose plan

conventional simulation involves the use of fluoroscopy and radiographs as well as creating manual contours of the pt's external anatomy to create an _________ _______

inhomogeneity

With conventional simulations, the dose ______________ that occurs due to difference in pt's external anatomy can not be accounted for

water

for dose calculation with conventional simulation, the patient was treated as a homogeneous _________ density equivalent

lungs

With using a dose calculation as a homogeneous water density equivalent, this means the ________ were treated as having the same density as the pelvic bone

aquaplast, wire outline, pantograph, and pin frame

What are some options to recreate the patient's external surface?