Background

Radiotherapy is a directed treatment that targets a specific volume (three dimensional shape) in the body. According to Burnet et al., 2004: “There are three main volumes in radiotherapy planning. The first is the position and extent of gross tumour, i.e. what can be seen, palpated or imaged; this is known as the gross tumour volume (GTV)… The second volume contains the GTV, plus a margin for sub-clinical disease spread which therefore cannot be fully imaged; this is known as the clinical target volume (CTV)… The CTV is important because this volume must be adequately treated to achieve cure. The third volume, the planning target volume (PTV), allows for uncertainties in planning or treatment delivery. It is a geometric concept designed to ensure that the radiotherapy dose is actually delivered to the CTV. Radiotherapy planning must always consider critical normal tissue structures, known as organs at risk (ORs). In some specific circumstances, it is necessary to add a margin analogous to the PTV margin around an OR to ensure that the organ cannot receive a higher-than-safe dose; this gives a planning organ at risk volume. This applies to an organ such as the spinal cord, where damage to a small amount of normal tissue would produce a severe clinical manifestation.”

Usage

This profile describes the concepts of GTV, CTV, PTV and OARs in terms of a BodyStructure resource. Using a stand-alone resource to describe a radiotherapy volume has several benefits:

1. It uses an existing FHIR Resource, and avoids creation of a complex extension.
2. It permits reuse of the same body volume in planning, executing, and reporting a radiotherapy treatment, as opposed to repeating the same elements in multiple places.
3. There is a single source of truth for a radiotherapy volume.
4. The use of BodyStructure fits the intended purpose of the BodyStructure resource and allows attachment of images and other textual and coded information that could be needed to fully describe a radiotherapy volume.

The disadvantage of separating the radiotherapy volume is that it is not in the same resource as the modality, technique, and dose information, but overall, the above advantages are felt to outweigh this disadvantage.

Limitations

A known limitation of the RadiotherapyVolume is that it accepts only one coded location. This limitation stems from the base BodyStructure resource. As a result, a compound volume (such as prostate plus seminal vesicles) cannot be represented. If this presents a serious limitation in practice, an extension with additional pairs (location, location qualifiers) will be required.

Conformance

Procedure resources whose morphology has a code from the value set RadiotherapyVolumeTypeVS MUST conform to this profile. Beyond this requirement, a producer of resources SHOULD ensure that any resource instance associated with an mCODE patient that would reasonably be expected to conform to this profile SHOULD be published in this form. Any resource intended to conform to this profile SHOULD populate meta.profile accordingly.

• Text Summary
• Differential Table
• Snapshot Table
• Snapshot Table (Must Support)
• All

This structure is derived from BodyStructure

Name	Flags	Card.	Type	Description & Constraints
BodyStructure	I	0..*	BodyStructure	Specific and identified anatomical structure mcode-description-or-id-required: One of description or identifier MUST be present
identifier	S	0..*	Identifier	Volume Identifier
morphology	S	0..1	CodeableConcept	Type of Radiotherapy Volume Binding: Radiotherapy Volume Type Value Set (extensible)
location	S	0..1	CodeableConcept	Body Location Code. Binding: Radiotherapy Treatment Location Value Set (required)
locationQualifier	S	0..*	CodeableConcept	Body site modifier Binding: Radiotherapy Treatment Location Qualifier Value Set (extensible)
description	S	0..1	string	Volume Description
patient	S	1..1	Reference(Patient)	Who this is about
Documentation for this format

Name	Flags	Card.	Type	Description & Constraints
BodyStructure	I	0..*	BodyStructure	Specific and identified anatomical structure mcode-description-or-id-required: One of description or identifier MUST be present
id	Σ	0..1	string	Logical id of this artifact
meta	Σ	0..1	Meta	Metadata about the resource
implicitRules	?!Σ	0..1	uri	A set of rules under which this content was created
language		0..1	code	Language of the resource content Binding: CommonLanguages (preferred) Max Binding: AllLanguages: A human language.
text		0..1	Narrative	Text summary of the resource, for human interpretation
contained		0..*	Resource	Contained, inline Resources
extension		0..*	Extension	Additional content defined by implementations
modifierExtension	?!	0..*	Extension	Extensions that cannot be ignored
identifier	SΣ	0..*	Identifier	Volume Identifier
active	?!Σ	0..1	boolean	Whether this record is in active use
morphology	SΣ	0..1	CodeableConcept	Type of Radiotherapy Volume Binding: Radiotherapy Volume Type Value Set (extensible)
location	SΣ	0..1	CodeableConcept	Body Location Code. Binding: Radiotherapy Treatment Location Value Set (required)
locationQualifier	S	0..*	CodeableConcept	Body site modifier Binding: Radiotherapy Treatment Location Qualifier Value Set (extensible)
description	SΣ	0..1	string	Volume Description
image		0..*	Attachment	Attached images
patient	SΣ	1..1	Reference(Patient)	Who this is about
Documentation for this format

Name	Flags	Card.	Type	Description & Constraints
BodyStructure	I	0..*	BodyStructure	Specific and identified anatomical structure mcode-description-or-id-required: One of description or identifier MUST be present
identifier	Σ	0..*	Identifier	Volume Identifier
morphology	Σ	0..1	CodeableConcept	Type of Radiotherapy Volume Binding: Radiotherapy Volume Type Value Set (extensible)
location	Σ	0..1	CodeableConcept	Body Location Code. Binding: Radiotherapy Treatment Location Value Set (required)
locationQualifier		0..*	CodeableConcept	Body site modifier Binding: Radiotherapy Treatment Location Qualifier Value Set (extensible)
description	Σ	0..1	string	Volume Description
patient	Σ	1..1	Reference(Patient)	Who this is about
Documentation for this format

This structure is derived from BodyStructure

Summary

Must-Support: 6 elements

Differential View

This structure is derived from BodyStructure

Name	Flags	Card.	Type	Description & Constraints
BodyStructure	I	0..*	BodyStructure	Specific and identified anatomical structure mcode-description-or-id-required: One of description or identifier MUST be present
identifier	S	0..*	Identifier	Volume Identifier
morphology	S	0..1	CodeableConcept	Type of Radiotherapy Volume Binding: Radiotherapy Volume Type Value Set (extensible)
location	S	0..1	CodeableConcept	Body Location Code. Binding: Radiotherapy Treatment Location Value Set (required)
locationQualifier	S	0..*	CodeableConcept	Body site modifier Binding: Radiotherapy Treatment Location Qualifier Value Set (extensible)
description	S	0..1	string	Volume Description
patient	S	1..1	Reference(Patient)	Who this is about
Documentation for this format

Snapshot View

Name	Flags	Card.	Type	Description & Constraints
BodyStructure	I	0..*	BodyStructure	Specific and identified anatomical structure mcode-description-or-id-required: One of description or identifier MUST be present
id	Σ	0..1	string	Logical id of this artifact
meta	Σ	0..1	Meta	Metadata about the resource
implicitRules	?!Σ	0..1	uri	A set of rules under which this content was created
language		0..1	code	Language of the resource content Binding: CommonLanguages (preferred) Max Binding: AllLanguages: A human language.
text		0..1	Narrative	Text summary of the resource, for human interpretation
contained		0..*	Resource	Contained, inline Resources
extension		0..*	Extension	Additional content defined by implementations
modifierExtension	?!	0..*	Extension	Extensions that cannot be ignored
identifier	SΣ	0..*	Identifier	Volume Identifier
active	?!Σ	0..1	boolean	Whether this record is in active use
morphology	SΣ	0..1	CodeableConcept	Type of Radiotherapy Volume Binding: Radiotherapy Volume Type Value Set (extensible)
location	SΣ	0..1	CodeableConcept	Body Location Code. Binding: Radiotherapy Treatment Location Value Set (required)
locationQualifier	S	0..*	CodeableConcept	Body site modifier Binding: Radiotherapy Treatment Location Qualifier Value Set (extensible)
description	SΣ	0..1	string	Volume Description
image		0..*	Attachment	Attached images
patient	SΣ	1..1	Reference(Patient)	Who this is about
Documentation for this format