DICOM PS3.17 2024c - Explanatory Information

AAAA.2 CT Routine Adult Head Protocol

The examples in this Annex are intended to illustrate the encoding mechanisms of the DICOM CT Protocol Storage IODs, not to suggest particular values for clinical use. Further, these examples do not contain the many detailed Attributes one would expect from a fully executable defined protocol generated by a CT scanner, but they do demonstrate the usage of many common Attributes.

This section includes Defined Protocol examples of a Routine Adult Head Protocol for several different scanner models. The protocol is presented as adjusted by a fictitious Mercy Hospital from a reference protocol referenced in the Predecessor Protocol Sequence. Although the examples in this section were originally derived from protocol documents previously published by the AAPM, some values here were modified and are likely out of date. Parties interested in the current AAPM protocols are encouraged to visit http://www.aapm.org/pubs/CTProtocols/

AAAA.2.1 Common Context

Table AAAA.2-1 is basically the same for each model so it is shown here rather than duplicating it. The second half for two different scanner models is then shown below in Table AAAA.2-2 and Table AAAA.2-3.

Table AAAA.2-1. Routine Adult Head - Context




Equipment Modality



Custodial Organization Sequence


>Institution Name


Mercy Hospital

>Institution Code Sequence


Responsible Group Code Sequence


(C2183225, UMLS, "Neuroradiology")

Protocol Name


AAPM Routine Adult Head (Brain)

Potential Scheduled Protocol Code Sequence


(24725-4, LN, "CT HEAD") ,



Potential Reasons for Procedure


Acute head trauma\

Suspected acute intracranial hemorrhage\

Immediate postoperative evaluation following brain surgery\

Suspected shunt malfunctions, or shunt revisions\

Mental status change\

Increased intracranial pressure\


Acute neurologic deficits\

Suspected hydrocephalus\

Evaluating psychiatric disorders\

Brain herniation\

Drug toxicity\

Suspected mass or tumor\



Detection of calcification\

When magnetic resonance imaging (MRI) imaging is unavailable or contraindicated, or if the supervising physician deems CT to be most appropriate.

Potential Diagnostic Tasks


Detect collections of blood\

Identify brain masses\

Detect brain edema or ischemia\

Identify shift in the normal locations of the brain structures including in the cephalad or caudal directions\

Evaluate the location of shunt hardware and the size of the ventricles\

Evaluate the size of the sulci and relative changes in symmetry\

Detect abnormal collections\

Detect calcifications in the brain and related structures\

Evaluate for fractures in the calvarium (skull) \

Detect any intracranial air

Predecessor Protocol Sequence


Referenced SOP Class UID



Referenced SOP Instance UID


Content Creator's Name



Protocol Design Rationale


Tube Current Modulation (or Automatic Exposure Control) may be used, but is often turned off;

According to ACR CT Accreditation Program guidelines:

- The diagnostic reference level (in terms of volume CTDI) is 75 mGy.

- The pass/fail limit (in terms of volume CTDI) is 80 mGy.

- These values are for a routine adult head scan and may be significantly different (higher or lower) for a given patient with unique indications.

NOTE: All volume CTDI values are for the 16-cm diameter CTDI phantom.

Additional Resources

ACR-ASNR Practice Guideline For The Performance Of Computed Tomography (CT) Of The Brain, http://www.acr.org/Quality-Safety/Standards-Guidelines/Practice-Guidelines-by-Modality/CT.

ACR CT Accreditation Program information, including Clinical Image Guide and Phantom Testing Instructions, http://www.acr.org/Quality-Safety/Accreditation/CT.

Protocol Planning Information


Contrast use as indicated by radiologist

Instance Creation Date



Instance Creation Time



Instruction Sequence


>Instruction Index



>Instruction Text


"Contrast, if directed. See Instruction Description."

>Instruction Description


"Some indications require injection of intravenous or intrathecal contrast media during imaging of the brain.

Intravenous contrast administration should be performed as directed by the supervising radiologist using appropriate injection protocols and in accordance with the ACR Practice Guideline for the Use of Intravascular Contrast Media. A typical amount would be 100 cc at 300 mg/cc strength, injected at 1 cc/sec. A delay of 4 minutes between contrast injection and the start of scanning is typical."

Protocol Defined Patient Position



Patient Positioning Instruction Sequence


>Instruction Index



>Instruction Text


"Head in the head-holder whenever possible."

>Instruction Index



>Instruction Text


"Arms resting along body and support lower legs."

>Instruction Index



>Instruction Text


"Center table height so EAM is at center of gantry."

>Instruction Index



>Instruction Text


"Align scan to reduce lens exposure."

>Instruction Description


"To reduce or avoid ocular lens exposure, the scan angle should be parallel to a line created by the supraorbital ridge and the inner table of the posterior margin of the foramen magnum.

This may be accomplished by either tilting the patient's chin toward the chest ("tucked" position) or tilting the gantry. While there may be some situations where this is not possible due to scanner or patient positioning limitations, it is considered good practice to perform one or both of these maneuvers whenever possible."

Anatomic Region Sequence


(69536005, SCT, "Head")

DICOM PS3.17 2024c - Explanatory Information