KLINIK UND POLIKLINIK FÜR NUKLEARMEDIZINDIREKTOR: PROF. DR. REINERS

Good practice of clinical dosimetry reporting

M. Lassmann, C. Chiesa, G. Flux, M. BardièsEANM Dosimetry Committee

EANM Dosimetry Committee

Established in 2002

8 EANM Members from 7 European Countries

1 IAEA Observer

Chair: M Lassmann (2002-2008)

M Bardiès (from 2009)

Why do we need to talk about a guidance document on“Good Practice of Clinical Dosimetry Reporting”

Publication X:“We performed dosimetry according to the MIRD formalism”

Publication Y:“Dosimetry was performed using ROI’s on planar images and OLINDA”

Good Practice of Clinical Dosimetry Reporting

Published 2010Available on-line @:www.eanm.org/scientific_info/guidelines/guidelines_intro.php?navId=54

Purpose of the Document:Recommendations to scientists and clinicians on how to document and report diagnostic, pre-therapeutic and/or peri- therapeutic clinical absorbed dose assessments.

This includes a checklist on the respective methodologies used for obtaining quantitative data, for generating and integrating activity-time-curves and for calculating absorbed doses.

Not in the scope of the document:Recommendations for optimal dosimetric methods

Good Practice of Clinical Dosimetry Reporting

- Measurement of the activity retention in the target volume- Calculation of the area under the curve (AUC) representing the total number

of decays- Multiplication of the AUC with the ‘relevant’ (patient-specific) absorbed dose

per nuclear transformation (S) value for obtaining the absorbed dose

„Simple“ Dosimetry

Pre-Treatment Uptake

0

1

2

3

4

5

6

0 24 48 72 96 120 144 168 192time p.a. (h)

Upt

ake

U (%

)

time-integrated activity coefficient

Good Practice of Clinical Dosimetry Reporting

• Equipment• Image Quantification• Biokinetics• Dosimetry Calculations• Miscellaneous

Equipment

• General remarks• Probe Measurements• Well Counters Measurements• Dose Calibrators• Gamma-cameras• Quality Control

Appendix: Documentation Checklist

Probe Measurements

Is the probe used as a simple counter?In conjunction with gamma spectroscopy?Is the probe shielded and/or collimated?Are the geometric properties of the shielding/collimation given?Is the geometry of the patient measurement given?Are the background counts without any sources present given?Are the sensitivity and the window settings documented?Is the sensitivity range of the device provided?Are the dead time characteristics of the system known?

Dosimetry in Multi-Center Trials

Probe Measurements

Vertical Positioning(Spacer bar would be removed

for measurement)

Phantom Position Relative to Probe

Appendix: Documentation Checklist

Gamma-Cameras

Gamma camera make (name of the manufacturer) and model Crystal thicknessEnergy window(s) (number + range of each)Pixel size / Matrix sizeNumber of heads used for the acquisitionSoftware versionCollimatorStopping conditions

Image Quantification

• Acquisition settings• Phantom and Calibration Measurements• Sequential Imaging• Conjugate View Method• Processing Parameters (SPECT)• Background correction• Attenuation Correction• Scatter Correction• Partial Volume Effect Correction• Dead Time Correction• PET – Correction for “dirty” Nuclides

Appendix: Documentation Checklist

Gamma-Cameras•Stopping conditions•ROI location and size•Corrections for overlapping organs•Background correction•Method of attenuation / scatter correction•Dead time correctionSPECT•Number of projections•Orbit type•Rotation parameters•Reconstruction parameters•Software used

ROI´s for Remnants

Anterior Posterior

R7: S1(ROI ∅ 5 cm, 2“)

R8: S2

R9: “inner” remnant ROIR10: “outer” remnant ROI

Posterior

Anterior

Table

Neck Cushion

CardboardBox orStyrofoam

S2 S15 cm2”

20 cm, 8”

S1

S2

View from Left Side Top View

Local data extraction and calculations

Hänscheid et al.JNM 2006

Planar Scans – Monte-Carlo-Simulation

I-131, Monte-Carlo- Simulation

Ljungberg 98

Pre-Treatment Uptake

0

1

2

3

4

5

6

0 24 48 72 96 120 144 168 192time p.a. (h)

Upt

ake

U (%

)

- Measurement of the retention in the target volume

„Simple“ Dosimetry

Biokinetics

• Number of Data Points• Fitting and integration procedures• Extrapolation• Residence times

• Compartment modelling• Direct Integration using

Trapezoidals• Least-square fit

(linear combination of exponentials)

Important: Document all assumptions and methods (include, if possible, an error assessment)

Major sources of uncertainties are−

How is the AUC taken from 0 to the first data point

−

What are the assumptions after the last measurement (physical decay?)

Calculation of the AUC

- Measurement of the retention in the target volume- Calculation of the area under the curve (AUC) representing the total number

of decays- Multiplication of the AUC with the ‘relevant’ (patient-specific) absorbed dose

per nuclear transformation (S) value for obtaining the absorbed dose

„Simple“ Dosimetry

Pre-Treatment Uptake

0

1

2

3

4

5

6

0 24 48 72 96 120 144 168 192time p.a. (h)

Upt

ake

U (%

)

time-integrated activity coefficient

Dosimetry Calculations

• Calculation Procedure• S-Values• Mass (or volume) determination• Tumour dosimetry• Absorbed Doses (Results)• Statistical Errors• Radiobiological parameters

S-Values: Tabelle OLINDA

Blood absorbed dose calculation for thyroid cancer patients

Absorbed Dose: 0.24 Gy

wt = 78kg

0.01

0.1

1

10

100

0 20 40 60 80 100

Hours after Administration

Rel

ativ

e A

ctiv

ity in

Blo

od [%

/L]

Rel

ativ

e W

hole

Bod

y A

ctiv

ity [%

]

WB

Blood

2.46% / 2^(t/7.5h) + 0.927% / 2^(t/15.7h)

95.8% / 2^(t/9.4h) + 20.0% / 2^(t/18.6h)

τtotalbody = 16.1 [h]

τl of blood = 0.44 [h]

Therapy 3.7 GBqI-131

EANM Dosimetry Committee 2008 SOP on Blood Dosimetry for the Treatment of Thyroid Cancer

Miscellaneous

• Confounding factors• External Audit• Choice of Nuclide and Radiopharmaceutical• Units

Dosimetry - Units ?

The EANM Guidance Document helps to improv e reproducibility of dosimetric procedures by showing how to report all the steps needed for dosimetry:

• Choice and QC of the Equipment• Image and Data Quantification• Determination of Biokinetics and the Corresponding

Integration of the Time-Activity Curve • Dosimetry Calculations• Miscellaneous

Conclusions

KLINIK UND POLIKLINIK FÜR NUKLEARMEDIZINDIREKTOR: PROF. DR. REINERS

Good practice of clinical dosimetry reporting

M. Lassmann, C. Chiesa, G. Flux, M. BardièsEANM Dosimetry Committee