DICOM PS3.17 2024e - Explanatory Information |
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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derived from protocol documents previously published by the AAPM, some values here were modified and are likely out of date.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/
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
(24726-2, LN, "CT HEAD WITHOUT THEN WITH IV CONTRAST") , |
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Suspected acute intracranial hemorrhage\ Immediate postoperative evaluation following brain surgery\ Suspected shunt malfunctions, or shunt revisions\ Increased intracranial pressure\ Evaluating psychiatric disorders\ When magnetic resonance imaging (MRI) imaging is unavailable or contraindicated, or if the supervising physician deems CT to be most appropriate. |
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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 calcifications in the brain and related structures\ |
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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. 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. |
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"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." |
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"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." |
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DICOM PS3.17 2024e - Explanatory Information |
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