Icru 58 36x1a
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ICRU-58 RECOMMENDATIONS FOR DOSE REPORTING
BY PRATISHTHA SHARMA ALKA KATARIA SALONI CHAWLA
INTERSTITIAL IMPLANTS
Temporary Implant
Radioactive source is removed from the tissue after the treatment. • Total time of implantation depends upon the no. of sources , their strength and pattern. • Dose distribution can be changed by the manipulation of dwell time. •
Permanent Implant
• Radioactive source remain in the tissue. • No. of sources depends upon their initial strength. •No possibility of change in the dose distribution.
Source Specification Total Reference Air Kerma : Sum of the product of reference air Kerma rate and irradiation time for each source where reference air Kerma rate is Kerma rate in air at reference distance 1 m and corrected for air attenuation and scattering. Units: μ Gy/hr at 1 m
The simple determination of the total reference air Kerma does not, however, allow one to derive, even approximately, the absorbed dose in the immediate vicinity of the sources ( in the tumor or target volume).
VOLUMES VOLUMES
GTV (Gross Tumor Volume)
Gross palpable or visible extent and location of malignant growth.
CTV (Clinical Target Volume) • Tissue volume which contains GTV and microscopic malignant disease. • This volume should be treated adequately in order to achieve the aim of therapy.
PTV (Planning Target Volume)
In interstitial brachy therapy PTV is in general identical to CTV with very few exceptions.
TV (Treated Volume) That Volume which is encomed by an isodose surface appropriate to achieve the purpose of treatment.
DESCRIPTION OF SOURCE PATTERNS
Essentially all implants are volume implants so it could not be used to describe the specific implant . A single plane implant An implant containing two or more sources which lie in the same plane. In some instances, the sources lie in a single curved surface. A two plane implant Two planes which are generally parallel to each other. Larger implants can often be described according to the number of planes of sources used. If the implant is not formed in recognizable planes, the location of the sources relative to a plane ing through the center of the implant or by a specific geometrical configuration (e.g., sphere or cylinder).
Planes
Central plane: Plane perpendicular to the direction of the source lines.(where, source lines are straight , parallel and of equal length.)
LINEAR SOURCES WITH PARALLEL IMPLANTATION LINEAR SOURCES WITH NON PARALLEL IMPLANTATION COMPLEX IMPLANT
DOSE DISTRIBUTION 1) 2)
One plane :Central plane of implant is chosen Dose distribution in other areas: Multiple planes for isodose calculation either Parallel OR Perpendicular to the central plane.
DESCRIPTION OF DOSE DISTRIBUTION Non-homogenous Steep dose gradients Regions of high dose surrounding each source. Within the volume of the implant, there are regions where the dose gradient approximates a plateau. PLATEAU REGION The regions of plateau dose are equidistant between adjacent neighbouring sources, for sources of identical linear activity. They are regions of local minimum doses. Variations in the dose between the different plateau doses can be used t o describe the dose uniformity of an implant. A region of plateau dose is the place where the dose can be calculated most reproducibly and compared easily by different departments.
Prescribed Dose :
Dose defined at the time of planning by the team of radiation oncologist and medical physicist.
Minimum Target Dose (MTD) : Minimum dose at the periphery of the CTV. It should be adequate to treat CTV. It defines the treatment volume and should entirely encom the clinical target volume. MINIMUM PERIPHERAL DOSE : AMERICAN CENTRES (MISNOMER) 90% of the Prescibed dose ( Manchester System For Interstitial Therapy.) The MTD is known as the reference dose in the PARIS system.
Mean Central Dose(MCD) :
It is taken to be the arithmetic mean of the local minimum doses b/w sources in the central plane OR central planes
MEAN CENTRAL DOSE
Implant in more than one plane
Complex Implants
Arithmetic mean of the local minimum doses b/w each set of three adjacent source lines. • The minimum dose lies at the intersection of perpendicular bisector of sides of triangles.(GEOMETRIC AND EQUIDSITANT )
•Single plane may not include all the sources. •Sub divide the volume. •Then choose a separate central plane for each sub volume.
Implant in one plane
• MCD
is in the central plane • Arithmetic mean of the doses at mid distance b/w each pair of adjacent source lines.
•
Three practical methods are acceptable for determining mean central dose. 1. Implants with Parallel Lines :
Evaluation of dose profiles: Calculate dose profiles for one or more axes through the center of the implant expected to through as many local minima as possible. Determine, by inspection, the local minimum doses. The mean of these local minimum values is the mean central dose 3:Inspection of dose distribution: Plot the dose distribution in the central plane. Isodose lines varying by 5% (at most 10%) of the local dose in the central region, the local minima can be determined by inspection 2.
Correlation between radiation dose with late effects and recurrence
HIGH DOSE VOLUME
Volume encomed by the isodose corresponding to 150% of MCD around the source in any plane parallel to the central plane. • To correlate radiation late damage ,the high dose volume around sources should be assessed.
•DIMENSIONS
LOW DOSE VOLUME
• It is defined as the volume within
the CTV ,encomed by an isodose corresponding to 90% of the prescribed dose. • If the CTV is not covered by the minimum target isodose ,there’ll be low dose region & local recurrence.
Time and Dose rate for temporary implants DOSE
TIME Irradiation time
• Time during which the radioactive source is present in the patient.
Overall treatment time
• Total time elapsed from the beginning of the first irradiation to the end of last one.
Instantaneous dose rate
Avg. overall treatment dose rate
• It is the quotient of the dose and the irradiation time , for a given fraction or pulse.
• It is the quotient of the total dose and the overall treatment time. • It is useful for continuous LDR irradiation with or without interruption.
Time Dose Pattern for Temporary Implants
Continuous Irradiation
• The overall treatment time is equal to the irradiation time.
Non-Continuous Irradiation
• The overall treatment time is greater than the irradiation time due to the planned short interruption during the treatment .
Fractionated Irradiation
• Irradiation time is sub-divided into multiple fractions . • The overall treatment time is much greater than the total irradiation time.
Pulsed Irradiation • • A single high dose source is used to give a sequence of short irradiation(pulses ) to simulate continuous LDR. • Time interval is shorter than few hours.
Hyperfractionated Irradiation :
When two or more fractions are given per day. When the time interval between short high dose rate irradiation reaches or exceeds four hours, irradiation should be considered as hyperfractionated. If the time interval is equal to one or several days then it should be considered as fractionated irradiation.
RECOMMENDATION FOR RECORDING AND REPORTING
DESCRIPTION OF VOLUME
Description should as a minimum include as a minimum gross tumor volume , clinical target volume , treated volume
Description of Sources
Radionuclide used (with or without filtration). Type of source used : wires , seeds ,seed ribbons ,hairpin , needle etc. Length of each line source. Reference air kerma rate of each source and source line. The distribution of strength within the source should be described (uniform or differential loading).
DESCRIPTION OF TECHNIQUE AND SOURCE PATTERN
No. Of sources used. Separation between source lines and plane. Geometric pattern form by the sources with the central plane of implant(e.g.triangles , squares ). The surfaces in which the implant lies i.e ; planes or curved surfaces. Crossing sources are placed at one or more ends. The material used to carry the radioactive substance (flexible and rigid). Type of remote after loading if used.
DESCRIPTION OF TIME PATTERN The description of the time pattern should include the type of irradiation with the necessary data on treatment and irradiation times. The information on dose and time should provide the necessary data to calculate instantaneous and average dose rates. Continuous irradiation- the overall treatment time should be recorded. Non-continuous irradiation-both the overall treatment time and the total irradiation time should be recorded, together with information about lengths of gaps. Fractionated and hyperfractionated irradiation the irradiation time of each fraction or pulse, the interval between fractions and the overall treatment time should be recorded. When the irradiation times of the different sourcesare not identical, they should be recorded.Moving sources: (i) Stepping sources (ii) Oscillating sources
DESCRIPTION OF DOSE DISTRIBUTION
PRESCRIBED DOSE MINIMUM TARGET DOSE MEAN CENTRAL DOSE Additional information such as : Dimension of high dose volume Dimension of low dose volume Any dose uniformity data
BY PRATISHTHA SHARMA ALKA KATARIA SALONI CHAWLA
INTERSTITIAL IMPLANTS
Temporary Implant
Radioactive source is removed from the tissue after the treatment. • Total time of implantation depends upon the no. of sources , their strength and pattern. • Dose distribution can be changed by the manipulation of dwell time. •
Permanent Implant
• Radioactive source remain in the tissue. • No. of sources depends upon their initial strength. •No possibility of change in the dose distribution.
Source Specification Total Reference Air Kerma : Sum of the product of reference air Kerma rate and irradiation time for each source where reference air Kerma rate is Kerma rate in air at reference distance 1 m and corrected for air attenuation and scattering. Units: μ Gy/hr at 1 m
The simple determination of the total reference air Kerma does not, however, allow one to derive, even approximately, the absorbed dose in the immediate vicinity of the sources ( in the tumor or target volume).
VOLUMES VOLUMES
GTV (Gross Tumor Volume)
Gross palpable or visible extent and location of malignant growth.
CTV (Clinical Target Volume) • Tissue volume which contains GTV and microscopic malignant disease. • This volume should be treated adequately in order to achieve the aim of therapy.
PTV (Planning Target Volume)
In interstitial brachy therapy PTV is in general identical to CTV with very few exceptions.
TV (Treated Volume) That Volume which is encomed by an isodose surface appropriate to achieve the purpose of treatment.
DESCRIPTION OF SOURCE PATTERNS
Essentially all implants are volume implants so it could not be used to describe the specific implant . A single plane implant An implant containing two or more sources which lie in the same plane. In some instances, the sources lie in a single curved surface. A two plane implant Two planes which are generally parallel to each other. Larger implants can often be described according to the number of planes of sources used. If the implant is not formed in recognizable planes, the location of the sources relative to a plane ing through the center of the implant or by a specific geometrical configuration (e.g., sphere or cylinder).
Planes
Central plane: Plane perpendicular to the direction of the source lines.(where, source lines are straight , parallel and of equal length.)
LINEAR SOURCES WITH PARALLEL IMPLANTATION LINEAR SOURCES WITH NON PARALLEL IMPLANTATION COMPLEX IMPLANT
DOSE DISTRIBUTION 1) 2)
One plane :Central plane of implant is chosen Dose distribution in other areas: Multiple planes for isodose calculation either Parallel OR Perpendicular to the central plane.
DESCRIPTION OF DOSE DISTRIBUTION Non-homogenous Steep dose gradients Regions of high dose surrounding each source. Within the volume of the implant, there are regions where the dose gradient approximates a plateau. PLATEAU REGION The regions of plateau dose are equidistant between adjacent neighbouring sources, for sources of identical linear activity. They are regions of local minimum doses. Variations in the dose between the different plateau doses can be used t o describe the dose uniformity of an implant. A region of plateau dose is the place where the dose can be calculated most reproducibly and compared easily by different departments.
Prescribed Dose :
Dose defined at the time of planning by the team of radiation oncologist and medical physicist.
Minimum Target Dose (MTD) : Minimum dose at the periphery of the CTV. It should be adequate to treat CTV. It defines the treatment volume and should entirely encom the clinical target volume. MINIMUM PERIPHERAL DOSE : AMERICAN CENTRES (MISNOMER) 90% of the Prescibed dose ( Manchester System For Interstitial Therapy.) The MTD is known as the reference dose in the PARIS system.
Mean Central Dose(MCD) :
It is taken to be the arithmetic mean of the local minimum doses b/w sources in the central plane OR central planes
MEAN CENTRAL DOSE
Implant in more than one plane
Complex Implants
Arithmetic mean of the local minimum doses b/w each set of three adjacent source lines. • The minimum dose lies at the intersection of perpendicular bisector of sides of triangles.(GEOMETRIC AND EQUIDSITANT )
•Single plane may not include all the sources. •Sub divide the volume. •Then choose a separate central plane for each sub volume.
Implant in one plane
• MCD
is in the central plane • Arithmetic mean of the doses at mid distance b/w each pair of adjacent source lines.
•
Three practical methods are acceptable for determining mean central dose. 1. Implants with Parallel Lines :
Evaluation of dose profiles: Calculate dose profiles for one or more axes through the center of the implant expected to through as many local minima as possible. Determine, by inspection, the local minimum doses. The mean of these local minimum values is the mean central dose 3:Inspection of dose distribution: Plot the dose distribution in the central plane. Isodose lines varying by 5% (at most 10%) of the local dose in the central region, the local minima can be determined by inspection 2.
Correlation between radiation dose with late effects and recurrence
HIGH DOSE VOLUME
Volume encomed by the isodose corresponding to 150% of MCD around the source in any plane parallel to the central plane. • To correlate radiation late damage ,the high dose volume around sources should be assessed.
•DIMENSIONS
LOW DOSE VOLUME
• It is defined as the volume within
the CTV ,encomed by an isodose corresponding to 90% of the prescribed dose. • If the CTV is not covered by the minimum target isodose ,there’ll be low dose region & local recurrence.
Time and Dose rate for temporary implants DOSE
TIME Irradiation time
• Time during which the radioactive source is present in the patient.
Overall treatment time
• Total time elapsed from the beginning of the first irradiation to the end of last one.
Instantaneous dose rate
Avg. overall treatment dose rate
• It is the quotient of the dose and the irradiation time , for a given fraction or pulse.
• It is the quotient of the total dose and the overall treatment time. • It is useful for continuous LDR irradiation with or without interruption.
Time Dose Pattern for Temporary Implants
Continuous Irradiation
• The overall treatment time is equal to the irradiation time.
Non-Continuous Irradiation
• The overall treatment time is greater than the irradiation time due to the planned short interruption during the treatment .
Fractionated Irradiation
• Irradiation time is sub-divided into multiple fractions . • The overall treatment time is much greater than the total irradiation time.
Pulsed Irradiation • • A single high dose source is used to give a sequence of short irradiation(pulses ) to simulate continuous LDR. • Time interval is shorter than few hours.
Hyperfractionated Irradiation :
When two or more fractions are given per day. When the time interval between short high dose rate irradiation reaches or exceeds four hours, irradiation should be considered as hyperfractionated. If the time interval is equal to one or several days then it should be considered as fractionated irradiation.
RECOMMENDATION FOR RECORDING AND REPORTING
DESCRIPTION OF VOLUME
Description should as a minimum include as a minimum gross tumor volume , clinical target volume , treated volume
Description of Sources
Radionuclide used (with or without filtration). Type of source used : wires , seeds ,seed ribbons ,hairpin , needle etc. Length of each line source. Reference air kerma rate of each source and source line. The distribution of strength within the source should be described (uniform or differential loading).
DESCRIPTION OF TECHNIQUE AND SOURCE PATTERN
No. Of sources used. Separation between source lines and plane. Geometric pattern form by the sources with the central plane of implant(e.g.triangles , squares ). The surfaces in which the implant lies i.e ; planes or curved surfaces. Crossing sources are placed at one or more ends. The material used to carry the radioactive substance (flexible and rigid). Type of remote after loading if used.
DESCRIPTION OF TIME PATTERN The description of the time pattern should include the type of irradiation with the necessary data on treatment and irradiation times. The information on dose and time should provide the necessary data to calculate instantaneous and average dose rates. Continuous irradiation- the overall treatment time should be recorded. Non-continuous irradiation-both the overall treatment time and the total irradiation time should be recorded, together with information about lengths of gaps. Fractionated and hyperfractionated irradiation the irradiation time of each fraction or pulse, the interval between fractions and the overall treatment time should be recorded. When the irradiation times of the different sourcesare not identical, they should be recorded.Moving sources: (i) Stepping sources (ii) Oscillating sources
DESCRIPTION OF DOSE DISTRIBUTION
PRESCRIBED DOSE MINIMUM TARGET DOSE MEAN CENTRAL DOSE Additional information such as : Dimension of high dose volume Dimension of low dose volume Any dose uniformity data
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