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63 Cards in this Set
- Front
- Back
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IMRT
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intensity modulated radiation therapy
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OAR
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organs at risk
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As dose to treatment area increases and _____ also increase
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inducing normal tissue damage
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The process by which external beams of radiation are designed and used to selectively and exclusively irradiate only tumor bearing sites is called
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3D CRT- three-dimensional conformal radiation therapy
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a computer controlled conformal radiation therapy technique treatment of more advanced cervical ca involving paraaortic lymph nodes. where the computer controlled the mechanical aspects of tx delivery such as gantry, dose rate, and couch movements
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dynamic conformal therapy
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a radiation therapy technique that uses 3D images of the tumor so that multiple radiation beams can be shaped exactly (conform) to the contour of the tumor volume and optimizes the dose to the contour of the tumor
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Conformal radiation therapy
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a procedure to make a system as effective as possible
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optimization
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Ex of beam compensators that absorb and slow down
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wedges
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attempts to deliver the same dose throughout a defined volume of tissue through multiple tx angles and beam intensities
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homogeneous radiation beam
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role is to produce a beam shape consistent with the 3D volume of the tumor.-the beam's shape or geometry projected from the gantry head of the linear accelerator matches some irregular shape of a tumor similar to a puzzle's piece that fits snuggly into an outlined area.
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multileaf collumation
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refers to the shape that the mechanical aperture (MLC) creates during part of the total dose delivered
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segment
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uses the collimators as a physical filter to modify the beam the same way a compensator may be used in conventional radiation therapy
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MLC-IMRT
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refers to the delivery of higher than traditional doses to a tx volume
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dose escalation
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The limiting factor to achieve full tumor control in conventional treatment has been
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dose-limiting normal tissue surrounding the tumor
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delineating structures by outlining their anatomic borders is a means of defining their volume is referred to
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contouring
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seeing out of the lens of the radiation beam and implies that the target volume is visualized as it is treated in a 3D plane
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beam's eye view
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fields are defined as fields with a hinge angle of 180 degrees
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POP fields
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the angle at the isocenter of two radiation fields
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hinge angle
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PET uses metabolic information using ______ because active malignant development is indicated by an enhanced uptake of it
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F (FDG) fluorodeoxyglucose
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Because active tumor cells have a higher ___, they take up the radioactive glucose readily. This results in the enhanced imaging based on a biologic process
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metabolism
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IGRT
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image guided radiation therapy
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helped to identify positional error before the delivery of a daily prescribed dose of radiation therapy usually ___ or ____ taken before tx
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IGRT
orthogonal cone beam CT |
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Orthogonal or cone beam CT are compared to ____ and then adjustments are made
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master DRR digital reconstructive radiograph
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use of real time monitoring of the tumor location has been a useful method of improving tx delivery accuracy
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respiratory gating
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Numerous noninvasive immobilization techniques provide a higher degree of precision such as
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-thermoplastic immobilization products
-customized polyurethane cradles -extended head to shoulder/upper thorax immobilization -longer head board extending from the head to the upper thorax for additional support of the head and shoulders -vacuum cradles -plastic casts -custom made devices |
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type of trial-and-error method of treatment planning and has been used in radiation therapy for many decades
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forward planning
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provides relevant dose data in a 3D format as a function of organ or tumor volume
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DVH
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system that works with the defined target dose and programmed normal tissue tolerance doses to create a number of beam portals and beam-intensity patterns within each portal
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inverse treatment planning
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who selects the dose to the target volumes using some constraints (minimum and maximum dose to that volume) and places limits on the dose to OARs
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physician
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in terms of computing, refers to a series of repetition following a sequence of instructions in a computer program, making slight adjustments to each treatment plan until the best result is acheived according to the criteria selected by the physician and planner.
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iteration
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refers to an opening in an instrument, much like an optical instrument that lets only a certain amount of light in or out
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aperture
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used to refer to the specific beam shape for one or a few segments of a beam
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aperture based
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considered the middle ground between forward planning and full inverse planning
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ABIP aperture-based inverse planning
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refers to an intensity pattern of the IMRT beam. This may be described as the sequence and progression of dose delivered per beam, as a product of several segments
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fluence pattern
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Biologically based objective functions use a calculated radiobiologic as a measure of the merit of a plan. This type of evaluation is based on predicted biologic response via a calculation model that relates _______
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dose plus volume of irradiated tissue
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A dose-based objective function is in the form of a weighted average of differences between _____ and ____ doses for all ____ in every tissue defined in a treatment plan
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delivered and prescribed
voxels |
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A ___ for each beam serves as the beam-intensity modulator. The ____ must be changed for every field, which requires increased time to deliver the IMRT treatment depending on the number of modulators used for the treatment plan.d This technique requires the simplest QA due to the lack of moving collimators.
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compensators
compensators |
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MLC-IMRT uses the _____ as a physical filter to modify the beam the same way a compensator may be used in conventional radiation therapy
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collimators
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MLC-based IMRT can be ____ or ____ treatment
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static or dynamic
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uses conventional MLCs with leaves that are not moved while the beam is on. It does not require control of individual leaf speed, and the field dose is easily verified. It is this simple concept that has made this a very popular technique
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Static MLC-IMRT
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uses moving MLCs during active treatment while the meam is on. They continuously change the beam shape as the individual leaves move.
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DMLC -dynamic MLC
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The system is more accurate and efficient, complicated and requires leaf speed and dose rate modulation. It requires comparatively more monitor units to deliver the same intensity pattern as static
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DMLC
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technique has been investigated for clinical use in recent years as an alternative to TomoTherapy
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IMAT -intensity modulated arc therapy
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technique describes the movement of the MLC from one side of the field to the other within a narrow opening while the beam is on. This technique is used with DMLC systems to generate a continuously varying intensity profile
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sliding window
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refers to a technique describing the leaves changing position, coming to rest, then delivering a dose of radiation. The leaves move only when the beam is off
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step and shoot
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referred to as TomoTherapy, consists of spiral beam covering tx vol or may be sequential like in CT
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fan beam intensity modulation
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One system uses a conventional linear accelerator with a custom design MLC system. Tx is delivered by beam rotates around the patient. This is a sequential treatment technique
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the Peacock mutileaf intensity-modulating collimator (MIMiC), by NOMOS Corp
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Adjacent MLC leaves slide against each other via _______ design, which reduces radiation leakage
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tongue-and-groove
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A typical IMRT treatment using MLCs requires ___ times more monitor units than conventional tx due to the inefficiency of segmented tx. and potential leakage is _____
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10x
greater |
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These units house a common gantry to allow pt to be scanned in the same position imaging session
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PET/CT simulator
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this system provides both kV and mV imaging capabilities by providing a separate radiation source and imaging panel
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ART adaptive radiation therapy
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The technique used achieved a dose distribution on the moving target similar to that of conventional tx for a static target (breathing)
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Four-dimentional TomoTherapy
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IMRT works by adjusting two beam properties
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beam shape and dose delivered
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The role of multileaf collimation is to produce a beam shape consistent with the 3D volume of the _____, referred to as beam sculpting.
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tumor
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The role of IMRT is to produce a beam that varies the radiation intensity delivered to the tumor volume producing changes in dose delivered as a function of _____ within the field and tumor status. This forms the basis of the DVH.
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tissue volume
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In inverse tx planning, the planner ____ MLC settings
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does not specify
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In inverse tx planning, desired doses ___ to the tumor, as well as to normal tissues.
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are specified
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Tx portal are designed using the perspective of a:
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beams eye view
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Computer iterations are performed to establish:
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optimization
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Plan evaluation for IMRT relies on analysis of dose distribution to assess dose to designated normal tissue. One item of study includes the
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dose volume histogram
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PET is an effective modality of biologic imaging, useful for tumor delineation because
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glucose metabolism of cancer cells take up the F-flourodeoxyglucose
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The step and shoot IMRT delivery systems are of higher complexity than dynamic systems requiring complicated leaf speed and dose rate modulation T or F
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false
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A fluence pattern may also be referred to as a
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intensity profile
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