TG-51 Workbench

Grounding stack

Primary authority
TG-51 protocol with 2014, 2022, and 2024 direct guidance and addenda
Historical lineage
TG-21 available for rationale and protocol comparison
Future context
TG-351 reserved for migration planning, not for overriding TG-51 execution

Live Workbench Signals

Completed sessions2

Action required1

Corrected reading24.8959 nC

Difference+0.02%

Worksheet Focus

Choose what is being measured and the chamber family being used to measure it. The worksheet below will then show only the inputs needed for that path.

Reference Worksheet

Worksheet A

Photon cylindrical worksheet

This worksheet follows the TG-51 photon reference path with a cylindrical chamber. The workbench asks for the chamber model and $\%dd(10)_x$ so it can resolve $k_Q$ from TG-51 Table I before evaluation.

Worksheet A Paper Transfer

Use the report worksheet to document the photon cylindrical reference setup on paper, then transfer the same values into the web form below.

Beam And Setup

Date, machine, beam label, photon energy, and setup geometry
Reference conditions at 10 cm depth with a 10 x 10 cm field

Measurements

$M_{raw}$ , $M_H$ , $M_L$ , $M^{+}_{raw}$ , and $M^{-}_{raw}$
Temperature and pressure at the time of measurement

Calibration Chain

Chamber model, $N_{D,w,{}^{60}\!Co}$ , and $P_{\mathrm{elec}}$
$\%dd(10)_x$ and the Table I $k_Q$ lookup result

Acceptance Record

$P_{leak}$ , reference dose, tolerance, and pass/fail note

Ready to evaluate the TG-51 worksheet

MeasuringPhoton output

UsingCylindrical chamber

k_Q

pathTG-51 Table I lookup

Sample Calculation Table

Select a correction factor row to review its measured inputs and update the sample value before continuing with the worksheet inputs below.

Factor	Symbol	Value	Role
Ion recombination	$P_{\mathrm{ion}}$	1.0029	Two-voltage recombination correction for pulsed beams.
Polarity	$P_{\mathrm{pol}}$	0.9986	Correction for polarity dependence.
Temperature-pressure	$P_{TP}$	1.0000	Normalizes the reading to reference atmosphere.
Electrometer	$P_{\mathrm{elec}}$	1.0004	Calibration traceability for the readout chain.
Beam quality	$k_Q$	0.9920	Maps the reference coefficient to the clinical beam quality.

Select a correction factor row to review its measured inputs and update the sample value.

Polarity

Correction for polarity dependence.

P_{\mathrm{pol}}

P_{\mathrm{pol}} = \frac{\lvert M^{+}_{raw} \rvert + \lvert M^{-}_{raw} \rvert}{2 \lvert M_{raw} \rvert}

Equation 9 uses the measured polarity readings. Enter $M^{+}_{raw}$ , $M^{-}_{raw}$ , and $M_{raw}$ to fill the sample value for $P_{pol}$ .

M^{+}_{raw}

M^{-}_{raw}

M_{raw}

Measurement Conditions

These inputs stay explicit for every TG-51 worksheet because they drive the raw reading, atmospheric correction, ion recombination, and polarity correction chain.

M_{raw}

Unit system

T_C

P_{\mathrm{kPa}}

V_H

V_L

M_H

M_L

M^{+}_{raw}

M^{-}_{raw}

Instrument And Beam Quality

Select the cylindrical chamber model and enter $\%dd(10)_x$ . The workbench interpolates the TG-51 Table I photon data before the request is submitted.

P_{\mathrm{elec}}

N_{D,w,{}^{60}\!Co}

Ion chamber model

\%dd(10)_x

k_Q

Acceptance Inputs

Photon workflows keep $P_{gr}$ fixed at 1.0000 here, so the acceptance inputs are leakage, reference dose, and tolerance.

P_{leak}

Reference dose (Gy)Tolerance (%)

Protocol guardrail

Protocol note: this is the only workflow here with a direct chamber-model lookup because the current local authority dataset is the TG-51 Table I photon cylindrical-chamber table.

Math Reference

Corrected reading

M = M_{raw} \times P_{ion} \times P_{pol} \times P_{TP} \times P_{elec} \times P_{leak}

Apply all chamber and atmospheric corrections before converting charge to absorbed dose.

Photon dose to water

D_{w,Q} = M \times N_{D,w,{}^{60}\!Co} \times k_Q

Reference absorbed dose to water for photon beams under TG-51 conditions.

Electron dose to water

D_{w,Q} = M \times N_{D,w,{}^{60}\!Co} \times k_Q \times P_{gr}

Electron reference dosimetry adds the gradient correction when the setup requires it.

Recent Session Table

Session	Beam	Date	Dose	Delta	Status
TG51-20260427-0003	6X	Apr 27, 2026	1.0162 Gy	+1.62%	action required
TG51-20260425-0002	6X	Apr 25, 2026	1.0005 Gy	+0.05%	completed
TG51-20260424-0001	10X	Apr 24, 2026	0.9982 Gy	-0.18%	completed

Operating rules

Deterministic TG-51 calculations with audit trails
Session-based measurement capture and sign-off
Historical machine and beam trend tracking
Citation-first AI assistance over the report corpus
No uncited assistant recommendations
No hidden calculation paths inside chat responses
No historical note treated as report authority
No workflow completion without structured evidence

Percent Difference Trend

The line chart shows recent dose-to-reference deltas by session.

Status Breakdown

Use this bar view to spot unresolved calibration work at a glance.

completed2

action required1

OpenTOPAS Monte Carlo

Plan or execute a TG-51 water-tank Monte Carlo study with a Farmer-type ion chamber at reference depth, then keep the primary dosimetry deck plus a bundled Qt/OpenGL visualization companion tied to this workbench.

Linked TG-51 sessionRequested byMachineBeam labelModalityNominal energySource modelPhase-space fileField size (cm)SAD (cm)Reference depth (cm)HistoriesVoxel size (mm)Scoring depth (cm)Phantom material

Notes

Photon reference runs model projected jaws, an MLC surrogate, and a Farmer-type chamber centered at the selected reference depth. Electron plans stage a simplified applicator channel. Each TG-51 artifact bundle also includes a Qt/OpenGL companion deck and local launcher for qualitative inspection of the beam-shaping geometry, water tank, and detector setup.

Attempt local OpenTOPAS execution now

Hosted TG-51 deployment stores planned simulations only. Download the deck bundle and run OpenTOPAS execution on a workstation build.

Physics Preview

Preview simulation ready

Statusplanned

Beam6X · 6 MV

Histories50,000

Source modellinac spectrum

Clinically motivated 6 MV template bremsstrahlung spectrum with 1.2 mm focal-spot sigma and 3.5 mrad angular spread.

Depth-dose preview is physics-informed planning data for the current deck, not a substitute for completed Monte Carlo scoring.

Crossline profile preview is physics-informed planning data at the selected reference plane.

Inline profile preview is physics-informed planning data at the selected reference plane.

World

box · Vacuum

80.0 × 80.0 × 240.0 cm

Varian TrueBeam Head Shell

cylinder · G4_Al

16.0 × 16.0 × 18.0 cm

Varian TrueBeam Beam Bore

cylinder · G4_AIR

Coupled to Varian TrueBeam Head Shell

6.0 × 6.0 × 18.0 cm

Secondary Collimator

box · G4_W

20.0 × 20.0 × 10.0 cm

Secondary Collimator Field Aperture

box · G4_AIR

Coupled to Secondary Collimator

5.0 × 5.0 × 10.0 cm

Water Tank Shell

box · G4_PLEXIGLASS

42.0 × 42.0 × 42.0 cm

TG51 Water Phantom

box · G4_WATER

Coupled to Water Tank Shell

40.0 × 40.0 × 40.0 cm

Central Axis Scorer

voxel_column · G4_WATER

Coupled to TG51 Water Phantom

0.2 × 0.2 × 30.0 cm

Farmer-Type Chamber Wall

cylinder · G4_GRAPHITE

Coupled to TG51 Water Phantom

0.7 × 0.7 × 2.6 cm

Farmer-Type Chamber Air Cavity

cylinder · G4_AIR

Coupled to Farmer-Type Chamber Wall

0.6 × 0.6 × 2.3 cm

Farmer-Type Central Electrode

cylinder · G4_Al

Coupled to Farmer-Type Chamber Air Cavity

0.1 × 0.1 × 1.8 cm

Farmer-Type Chamber Stem

cylinder · G4_PLEXIGLASS

Coupled to TG51 Water Phantom

0.7 × 0.7 × 7.0 cm

Download input deck Download bundle

Visualization Companion

Launch the local Qt/OpenGL companion from this workbench to inspect the simplified TrueBeam head, water tank, and Farmer chamber. This path is interactive only, uses the TG-51 backend host's configured OpenTOPAS binary, and is not physics-valid until the staged geometry is overlap-free.

Open visualization deck Download launcher Open notes

Local Qt/OpenGL launch is disabled on this hosted deployment. Download the visualization deck and launcher, then run them on a workstation with a Qt/OpenGL-enabled OpenTOPAS build.

Session evidence linkage

TG51-20260427-0003 · TrueBeam-A · 6X · action required

This Monte Carlo plan is attached to the TG-51 session evidence record.

Signed worksheet

document · captured Apr 27, 2026

Primary session worksheet signed by the performing physicist.

Path unavailable

Monte Carlo simulation topas-preview-6x

simulation · captured Apr 27, 2026

Engine: OpenTOPAS Status: planned Beam: TrueBeam-A 6X (6 MV) Source model: linac_spectrum Beam source: Clinically motivated 6 MV template bremsstrahlung spectrum with 1.2 mm focal-spot sigma and 3.5 mrad angular spread. Clinical setup: water tank with a Farmer-type ionization chamber centered at 10.0 cm. Qt visualization companion: bundled local launcher and OpenGL deck stage a simplified treatment head, water tank, and chamber for qualitative inspection.

Download bundle

tg51_topas.txt launch_tg51_qt_visualization.command qt_visualization_notes.txt tg51_topas_qt_visualization.txt

OpenTOPAS input deck

# OpenTOPAS TG-51 Monte Carlo setup: topas-preview-6x
# This deck models a beam-in-water reference dosimetry configuration with a clinical reference chamber for TG-51 style studies.
# Qt/OpenGL visualization companion artifacts are bundled separately for local qualitative inspection.
# Source model: linac_spectrum
# Source summary: Clinically motivated 6 MV template bremsstrahlung spectrum with 1.2 mm focal-spot sigma and 3.5 mrad angular spread.
s:Ge/World/Type = "TsBox"
d:Ge/World/HLX = 40.00 cm
d:Ge/World/HLY = 40.00 cm
d:Ge/World/HLZ = 120.00 cm
s:Ge/TreatmentHeadShell/Type = "TsCylinder"
s:Ge/SecondaryCollimator/Type = "TsBox"
s:Ge/SecondaryCollimatorOpening/HLX = 2.50 cm
s:Ge/WaterTankShell/Type = "TsBox"
s:Ge/WaterTankShell/Material = "G4_PLEXIGLASS"
s:Ge/WaterTankShell/TransZ = 20.00 cm
s:Ge/Phantom/Parent = "WaterTankShell"
s:Ge/Phantom/Type = "TsBox"
s:Ge/Phantom/Material = "G4_WATER"
# Clinical setup: Farmer-type chamber centered at TG-51 reference depth inside the water volume.
s:Ge/ReferenceChamberWall/Parent = "Phantom"
s:Ge/ReferenceChamberWall/Type = "TsCylinder"
d:Ge/ReferenceChamberWall/RMax = 0.35 cm
d:Ge/ReferenceChamberWall/HL = 1.30 cm
d:Ge/ReferenceChamberWall/RotY = 90. deg
d:Ge/ReferenceChamberWall/TransZ = -10.00 cm
s:Ge/ReferenceChamberWall/Material = "G4_GRAPHITE"
s:Ge/ReferenceChamberCavity/Parent = "ReferenceChamberWall"
s:Ge/ReferenceChamberCavity/Type = "TsCylinder"
d:Ge/ReferenceChamberCavity/RMax = 0.305 cm
d:Ge/ReferenceChamberCavity/HL = 1.15 cm
s:Ge/ReferenceChamberCavity/Material = "G4_AIR"
s:Ge/ReferenceChamberElectrode/Material = "G4_Al"
s:Ge/ReferenceChamberStem/Material = "G4_PLEXIGLASS"
s:So/Beam/Type = "Beam"
s:So/Beam/BeamEnergySpectrumType = "Continuous"
s:Sc/DepthDose/Quantity = "DoseToWater"
# Uncomment locally for interactive Qt/OpenGL visualization.
# s:Gr/View/Type = "OpenGL"
# s:Gr/View/ColorBy = "Material"

Recent Monte Carlo plans

Session Drill-down

Open a calibration session to inspect measurements, findings, linked simulations, and downloadable evidence without leaving the workbench.

Statusaction required

BeamTrueBeam-A · 6X

Evidence items2

Open findings1

Main Clinic · performed by Clinical Physicist · Apr 27, 2026, 12:00 PM

Reference TG-51 output session with linked Monte Carlo planning evidence.

Observation	Dose	Delta	Status
reference	1.0002 Gy	+0.02%	within tolerance

Reference output drift exceeds action threshold.
major · open · opened Apr 27, 2026, 12:05 PM
Repeat measurement and verify output calibration before releasing the session.

Evidence And Downloads

Signed worksheet

document · captured Apr 27, 2026, 12:15 PM

Primary session worksheet signed by the performing physicist.

Path unavailable in this workspace

Monte Carlo simulation topas-preview-6x

simulation · captured Apr 27, 2026, 12:20 PM

Engine: OpenTOPAS Status: planned Beam: TrueBeam-A 6X (6 MV) Source model: linac_spectrum Beam source: Clinically motivated 6 MV template bremsstrahlung spectrum with 1.2 mm focal-spot sigma and 3.5 mrad angular spread. Clinical setup: water tank with a Farmer-type ionization chamber centered at 10.0 cm. Qt visualization companion: bundled local launcher and OpenGL deck stage a simplified treatment head, water tank, and chamber for qualitative inspection.

Download bundle

tg51_topas.txt launch_tg51_qt_visualization.command qt_visualization_notes.txt tg51_topas_qt_visualization.txt

Linked simulations

topas-preview-6x

linac spectrum · planned

Clinically motivated 6 MV template bremsstrahlung spectrum with 1.2 mm focal-spot sigma and 3.5 mrad angular spread.

Crossline profile preview is physics-informed planning data at the selected reference plane.

Inline profile preview is physics-informed planning data at the selected reference plane.

Download deck Download bundle

launch_tg51_qt_visualization.command qt_visualization_notes.txt tg51_topas_qt_visualization.txt

TG-51 Assistant

This assistant retrieves TG-51 chunks first and only expands into lineage context when you ask for it.

Grounded Answer

Ready

Scope: TG-51 primary sources only.
Grounded summary:
[1] AAPM's TG-51 protocol for clinical reference dosimetry of high-energy photon and electron beams, Unlabeled section, pages 1-2: The protocol defines clinical reference dosimetry for high-energy photon and electron beams using an absorbed-dose-to-water formalism.
Use the cited report text as authority; do not treat this answer as a substitute for protocol review.

AAPM's TG-51 protocol for clinical reference dosimetry of high-energy photon and electron beams

tg51-1999 | tier 1 | Unlabeled section | pages 1-2

The protocol defines clinical reference dosimetry for high-energy photon and electron beams using an absorbed-dose-to-water formalism.