Материал: part03

Equipment preparation instructions would typically be limited to phantom imaging or other calibration procedures related to the indi-​ vidual patient scan. Phantom Imaging and/or Calibration to be performed as general QA/qualification (i.e., not associated with the​ individual patient scan) shall not be described in this Module.​

Activities that are associated with the protocol but which are not typically performed in the scanning room, such as the need to obtain​ creatinine values within 7 days before performing the Protocol, or to premedicate the patient with Benadryl 1 hour before performing​ the Protocol, are described in the Protocol Planning Information (0018,990F) rather than in this Module.​

C.34.8 Patient Positioning Module​

Table C.34.8-1 contains details about the positioning of the patient before and during the imaging procedure.​

Table C.34.8-1. Patient Positioning Module Attributes​

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C.34.8.1 Positioning Targets​

The specific method by which the referenced localizer images, photos of patient skin marks, landmarks, or frames of reference are​ usedtopositionthepatient,iscommunicatedbyreferencingtheassociatedcodeinthePositioningMethodCodeSequence(0018,991C).​

C.34.8.2 Anatomic Region & Primary Anatomic Structure​

Primary Anatomic Structure Sequence (0008,2228) shall identify the specific organ or structure that is the focus of the procedure​ describedbytheProtocolandwillgenerallycorrelatewiththeReasonforStudyandtheProcedureCode.AnatomicRegionSequence​ (0008,2218) shall identify the region of the body spanned by the images produced by the Protocol. For example, a Protocol might​ identify the Primary Anatomic Structure as "liver" and the Anatomic Region as "abdomen".​

The contents of the Anatomic Region Sequence (0008,2218) is not necessarily a precise description of the full extent of the scan or​ the reconstructed slices. "Chest" may refer to a scan that spans only part of the chest, the whole chest, or includes parts of regions​ beyond the chest. For a more precise description of the extent of the acquisition or reconstructed slices, refer to the Acquisition Start​ LocationSequence(0018,9931)andAcquisitionEndLocationSequence(0018,9932)ortheReconstructionStartLocationSequence​ (0018,993B) and Reconstruction End Location Sequence (0018,993C).​

For Protocols that could be used in a variety of anatomic regions, such as one designed for a certain type of metastasis or biopsy,​ the Primary Anatomic Structure Sequence might contain a generic code like (49755003, SCT, "Morphologically abnormal structure")​ andtheAnatomicRegionSequencemaybeemptyinthe(non-patient-specific)DefinedProtocol,butcouldbepopulatedinthePerformed​ Protocol. In such cases, the Protocol Context Module may describe a list of anatomic regions for which the Protocol is intended/ap-​ propriate.​

Note​

It is expected that the modality will migrate these codes, as appropriate, into the resulting images to facilitate the selection​ of hanging protocols and report templates appropriate to the primary anatomic structure or future searches for anatomically​ relevant priors.​

C.34.9 Defined CT Acquisition Module​

Table C.34.9-1 contains a specification of acceptable values and ranges of acquisition parameters for an imaging procedure.​

Table C.34.9-1. Defined CT Acquisition Module Attributes​

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>>IncludeTable10.25-1“AttributeValueConstraintMacro​OnlyAttributesdefinedinTableC.34.10-1(i.e.,intheAcquisitionProtocol​ Attributes”​ ElementSequence(0018,9920)inthePerformedCTAcquisitionModule)​

and Private Data Elements associated with this acquisition protocol​ element may be specified as Selector Attributes.​

The Performed CT Acquisition Module in the CT Performed Procedure Protocol will generally be "fully populated". The​ Defined CT Acquisition Module in the CT Defined Procedure Protocol Object may be "sparsely populated" (i.e., contains​ only the Attributes the system that is specifying the protocol "cares about").​

Attributes that might commonly be specified here include:​

•​KVP (0018,0060)​

•​X-Ray Tube Current in mA (0018,9330)​

•​Revolution Time (0018,9305)​

•​Single Collimation Width (0018,9306)​

•​Total Collimation Width (0018,9307)​

•​Spiral Pitch Factor (0018,9311)​

•​Exposure Modulation Type (0018,9323)​

•​CTDIvol Notification Trigger (0018,9942) (See Section C.34.9.2)​

•​DLP Notification Trigger (0018,9943)​

•​CTDIvol (0018,9345)​

C.34.9.1 Acquisition Protocol Elements​

ACTProtocolusuallyincludesmorethanoneAcquisitionProtocolElement.Forexample,achestProtocolmightincludethreeelements​ in total: two localizer CT radiographs (AP and Lateral), and a single helical scan.​

Since all parameters will be nested inside an Acquisition Protocol Element Sequence (0018,9920) and some of the parameters will​ be further nested inside a CT X-Ray Details Sequence (0018,9325), close attention must be paid to the use of the Selector Sequence​ Pointer (0072,0052) in the Attribute Value Constraint Macro. Illustrative examples are provided in Table C.34.9-2.​

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Table C.34.9-2. Example Usage of Selector Macro Attributes for Acquisition Constraints​

Element Sequence (0018,9920)​

C.34.9.2 Dose Related Attributes in Parameter Specification Sequence​

If CTDIvol Notification Trigger (0018,9942) or DLP Notification Trigger (0018,9943) are present in a parameter specification for an​ Acquisition Protocol Element, each is intended to communicate a Dose Check (NEMA XR-25-2010) threshold value associated with​ that Acquisition Protocol Element. As such, a Constraint Type (0082,0032) of EQUAL would be the most appropriate.​

If CTDIvol (0018,9345) is present in a parameter specification for an Acquisition Protocol Element, the value is intended to commu-​ nicate an estimate of the CTDIvol for that Acquisition Protocol Element. It is expected that the value would either be a single CTDIvol​ that represents a typical value given the parameter constraints and defaults provided, or a range that represents the expected value​ range if the parameters are varied within the defined constraints. The value of CTDIvol is not itself a constraint on the execution of​ theProtocol,butratheranestimatetohelptheradiologist,technologistand/orphysicistwhenreviewingandmanagingsetsofProtocols.​ Constraints and associated behaviors are provided by the CTDIvol Notification Trigger, the DLP Notification Trigger and the NEMA​ XR-25 Dose Check standard.​

Note​

It should be recognized that the formulae and methods used by any given scanner model to estimate CTDIvol may evolve​ over time. When such changes occur, devices that generate CT Defined Procedure Protocol instances, are advised to gen-​ erate new instances using the revised estimation methods.​

C.34.9.3 Attribute Value Constraint Macro​

The CT Defined Procedure Protocol SOP Class assigns the following significance to the values of Constraint Violation Significance​ (0082,0036) :​

•​FAILURE - Violating the constraint is a violation of the Protocol and requires supervisory permission and auditing.​

•​WARNING - Violating the constraint is a violation of the Protocol and requires operator confirmation and auditing.​

•​INFORMATIVE - Violating the constraint is not a violation of the Protocol. The constraint represents a guideline. Violation of the​ guideline may be recorded or shown to the operator.​

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