aapm tg 53 quality assurance fro clinical radiotherapy treatment planning

AAPM Task Group 53:

Quality assurance for clinical

radiotherapy treatment planning

SAMIR LAOUI, Ph.D.

Pre-Acceptance

The physicist need to investigate the clinical

needs in a TPS (Treatment Planning System)

Based on the procedures

The calculation algorithm required

Imaging

Compatibility with existing modalities

Acceptance Testing

Series of tests performed to confirm that the

TPS and hardware perform according to its

specifications

It is a way to confirm that institution received what

intended to purchase

Acceptance test is based on vendor’s data, not

institution data

It is common that it is vendor’s responsibility to

prepare TPS for acceptance testing

Acceptance Testing

1. CT input data

Ensure that CT data from CT simulator and

other software can be imported and exported

Ensure that information is completely transferred

Ensure that CT data dimension and quality is not

compromised in the transfer process

Ensure that data is not corrupted

Anatomical Description

TPS contouring capabilities and options

Using known test object, ensure the accuracy of

Hounsfield units, resolution, contrast,

dimensions, etc.

Verify that contours and correctly transferred

between TPS and other Software (example,

Eclipse and MIM)

Anatomic Description

Beam Description

Verify that all beam technique functions work,

using a standard beam description provided by

the vendor.

Verify that library of available machines and

beams is correct.

Verify that availability of machine and beam-

specific accessories, such as electron cones or

wedge is correct.

Photon Beam Dose Calculations

Photon Beam Dose Calculations: Perform dose

calculations for a standard photon beam dataset. Tests

should include:

various open fields

different SSDs

blocked fields

asymmetric jaw fields

MLC-shaped fields

wedged fields

inhomogeneity test cases

multi-beam plans

Electron Beam Dose Calculations

Perform a set of dose calculations for a standard

electron beam dataset. Tests should include:

open fields

different SSDs

shaped fields

surface irregularities

inhomogeneity test cases

Brachytherapy Dose Calculations

Brachytherapy Dose Calculations: Perform dose

calculations for single sources of each type, as

well as several multi-source implant calculations.

Tests examples include:

standard implant techniques such as a GYN

insertion with tandem and ovoid

Two-plane breast implant

prostate seed implant

Brachytherapy Dose Calculations

Dose Display, DVH

2-D Dose Displays: Verify

Isodose lines (IDLs) are correctly located.

Color wash display lines up correctly with IDLs and

agrees with point dose displays

Isodose Surfaces: Verify

Surfaces are displayed correctly.

Surfaces are consistent with isodose lines on planes.

Dose Display, DVH

Hardcopy Output

Ensure that the documentation is printed

correctly.

Commissioning

Acceptance testing does not mean treatment

planning is ready for clinical use

Commissioning is mandatory prior to clinical

use

In house data has to be used to verify the

vendor’s claims

Baselines are established and subsequently used

for future quality assurance

Immobilization devices should be investigated

prior to clinical use

Positioning and simulation: Accuracy of patient

position has to be investigated

Imaging: Image QA and Data transfer. Imaging

parameters

Nondosimetric Commissioning


Plan Implementation and verification

Coordinate system verification: TPS vs. treatment

unit

Data transfer: from RTP to treatment machine

Blocks and modifiers verification


Beam geometry: ISO center location; table position; G-angle; T-angle; C-

angle

Geometric accuracy: Location and accuracy of each beam in the plan should

much the real situation

Field shape design and entry: Rectangular collimators, shaped focused blocks,…field

shape entry should be defined

Wedges Orientation; display in the plan; display in the room

Dose Calculation Commissioning

Calculation verification

Compare calculated and measured doses

External beam calculation verification

Establish tolerances, required accuracy

Photon calculation verification tests

PDD

Output factors


Absolute dose output and plan normalization

Verify the output using sample clinical plans

For both electron and photon beams

For all energies

PDD, Beam profiles, TMR for all energies and

for all possible field sizes. For photons and

electrons

Depth Dose

One of the most critical and basic tests of any

dose calculation algorithm is the ability to

accurately predict the depth dose for standard

open field situations

Use test plans for verification

Use test plans for verification

Courtesy of Dr. J D

End-to-end Verification

Several anthropomorphic phantom tests can be

used for a final complete test of the entire

calculation algorithm

Phantom is treated as a real patient

Imaging, CT data transfer, target contouring,

planning, plan export, radiation delivery, dose

verification

This process is intended to identify any glitch

previously missed

Periodic quality assurance testing

Confirm the integrity and security of the RTP

data files

Verify the correct functioning and accuracy of

input devices

Check the integrity of the actual RTP system

software

Confirm the function and accuracy of output

devices

Treatment planning verification

When possible, verification and validation of

TPS should be performed by an external entity

using their own instrumentation

Routine VMAT/ IMRT QA can be used to

monitor the TPS performance

Periodic QA Testing: External Beam

TPS

Check CT display and conversion of Hounsfield

to electron density values

Verification of accuracy of electromagnetic

digitizer input and output

Verification of accuracy of printout dimensions

and geometric figures

Verification of reproducibility of structures on

DRR/BEV

aapm tg 53 quality assurance fro clinical radiotherapy treatment planning

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