DICOM and HL7which HL7 field becomes which DICOM attribute
Hospital systems speak HL7, scanners and PACS speak DICOM, and something has to turn one into the other. Neither standard defines that mapping. The one most radiology sites follow comes from IHE, and this page lays it out in tables.
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Which HL7 message does what
The IHE transactions that carry HL7 in the radiology workflow. Every message is acknowledged with an HL7 ACK. "Option" means the HL7 v2.5.1 option of IHE, which a system supports in addition to the HL7 v2.3.1 version.
| Transaction | From and to | HL7 v2.3.1 | HL7 v2.5.1 option | What it carries |
|---|---|---|---|---|
| RAD-1 Patient Registration | ADT system to order placer and department scheduler | ADT^A01 admit in-patient, A04 register outpatient, A05 pre-admit | ADT, the same events | Patient and visit data in PID and PV1. |
| RAD-12 Patient Update | Same | ADT^A02, A03, A06, A07, A08, A40 | ADT, the same events | Visit changes, patient updates (A08) and merges (A40). |
| RAD-2 Placer Order Management | Order placer to scheduler (order filler) | ORM^O01. ORC-1: NW new, CA cancel, DC discontinue | OMG^O19. Adds XO change order | The order: ORC and OBR with PID and PV1. |
| RAD-3 Filler Order Management | Scheduler (order filler) to order placer | ORM^O01. ORC-1: SN new order from the filler, OC cancelled by the filler, SC status update. Reply ORR (NA) | OMG^O19. Adds XX change order. Reply ORG | The filler's own orders and the order status (see the status table). |
| RAD-4 Procedure Scheduled | Scheduler to image manager and report manager | ORM^O01 with a ZDS segment. ORC-1 NW, ORC-5 SC | OMI^O23 with TQ1 and IPC segments | One message per requested procedure, with the accession number, procedure and Study Instance UID. |
| RAD-13 Procedure Update | Scheduler to image manager | ORM | OMI | Changes to procedure information that is already scheduled. |
No rows match the filter in this table.
The scheduler is the "Department System Scheduler/Order Filler": in many sites that is the RIS. A PACS that receives RAD-4 acts as the image manager.
HL7 order fields in a DICOM worklist entry (IHE Appendix B)
Where the values of a modality worklist response come from when the order arrives from the placer as an ORM (v2.3.1) or OMG (v2.5.1), plus the ADT fields marked below. The field is the same in both versions unless stated.
| DICOM attribute | Tag | HL7 field | Notes |
|---|---|---|---|
| Patient's Name | (0010,0010) | PID-5 | Components map by name, see the conversions table. |
| Patient ID | (0010,0020) | PID-3.1 | First component of the patient identifier list. IHE Appendix D discusses merge cases. |
| Issuer of Patient ID | (0010,0021) | PID-3.4 | The assigning authority of the identifier. |
| Patient's Birth Date | (0010,0030) | PID-7 | First component of the date/time. |
| Patient's Sex | (0010,0040) | PID-8 | DICOM allows M, F, O or empty. |
| Patient's Weight | (0010,1030) | OBX-5 | From the OBX that identifies "Body Weight", in kg. IHE shows it coming from an ADT message. |
| Patient's Size | (0010,1020) | OBX-5 | From the OBX that identifies "Body Height", in m. IHE shows it coming from an ADT message. |
| Referring Physician's Name | (0008,0090) | PV1-8 | Referring Doctor. |
| Requesting Physician | (0032,1032) | OBR-16 | Ordering Provider. |
| Admission ID | (0038,0010) | PV1-19 | Visit Number. If it is empty the value comes from PID-18, the account number. |
| Current Patient Location | (0038,0300) | PV1-3 | Assigned Patient Location. |
| Pregnancy Status | (0010,21C0) | PV1-15 | Ambulatory Status. The value B6 maps to 3, definitely pregnant. |
| Medical Alerts | (0010,2000) | OBR-13 | Relevant Clinical Info. |
| Contrast Allergies | (0010,2110) | AL1-3 | Allergy code, from an ADT message. |
| Confidentiality constraint on patient data | (0040,3001) | PV1-16 | VIP Indicator. |
| Requested Procedure Priority | (0040,1003) | ORC-7.6 (v2.3.1), TQ1-9 (v2.5.1) | Mapped as in the conversions table. |
| Reason for the Requested Procedure | (0040,1002) | OBR-31 | Reason for Study. The code sequence (0040,100A) comes from the same field. |
| Patient Transport Arrangements | (0040,1004) | OBR-30 | Transportation Mode. |
| Placer Order Number, Imaging Service Request | (0040,2016) | ORC-2 | Issuer and number. |
| Filler Order Number, Imaging Service Request | (0040,2017) | ORC-3 | Issuer and number. |
| Scheduled Performing Physician's Name | (0040,0006) | OBR-34 | Technician. Only the first component of the first repetition is used. |
| Specific Character Set | (0008,0005) | MSH-18 | The character set of the message. |
| Accession Number, Requested Procedure ID, Study Instance UID, Requested Procedure Description and Code, Scheduled Procedure Step ID, start date and time, station AE title, Modality | (0008,0050), (0040,1001), (0020,000D), (0032,1060), (0032,1064), (0040,0009), (0040,0002), (0040,0003), (0040,0001), (0008,0060) | None: generated | Generated by the department system scheduler, not taken from the order. The scheduler decides the modality from the content of the order. |
No rows match the filter in this table.
The order carries information about the order, not about scheduling or resources: those belong to the department scheduler. This appendix does not apply to the Procedure Scheduled transaction, which is the next table.
Procedure Scheduled (RAD-4): where the identifiers travel
The scheduler hands what it generated to the image manager (the PACS). The same values then appear in the worklist, the images and the MPPS. The two columns are the two versions of the same message.
| DICOM attribute | ORM^O01 (v2.3.1) | OMI^O23 (v2.5.1 option) | Notes |
|---|---|---|---|
Accession Number (0008,0050) | OBR-18 (Placer Field 1) | IPC-1 (Accession Identifier) | At most 16 characters. In the v2.5.1 message every IPC segment has the same value. |
Requested Procedure ID (0040,1001) | OBR-19 (Placer Field 2) | IPC-2 | In the v2.3.1 message all OBR segments have the same value. |
Study Instance UID (0020,000D) | ZDS-1 | IPC-3 | ZDS is a custom IHE segment. In ZDS-1 component 1 is the UID, component 3 is "Application" and component 4 is "DICOM". |
Scheduled Procedure Step ID (0040,0009) | OBR-20 (Filler Field 1) | IPC-4 | May repeat when a step has several protocol codes. |
Modality (0008,0060) | OBR-24 (Diagnostic Service Section ID) | IPC-5 | DICOM defined terms, such as CT. |
Scheduled Protocol Code (0040,0008) | OBR-4, components 4 to 6 | IPC-6 | Components 1 to 3 of OBR-4 hold the code of the order. |
Requested Procedure Code (0032,1064) | OBR-44 | OBR-44 | Components 1 to 3 are the code. Component 5 may hold the description. |
Laterality, appended to the Requested Procedure Description (0032,1060) | OBR-15 (Specimen Source) | OBR-46 (Placer Supplemental Service Information) | Only when the code in OBR-4 does not already say left or right. In v2.5.1 OBR-15 must not be present. |
| Scheduled start date and time | ORC-7.4 and OBR-27.4 | TQ1-7 | In v2.5.1 ORC-7 and OBR-27 are not populated. |
Placer Order Number (0040,2016) | ORC-2, OBR-2 | ORC-2, OBR-2 | Empty if the scheduler schedules a procedure for an unidentified patient without an order. |
Filler Order Number (0040,2017) | ORC-3, OBR-3 | ORC-3, OBR-3 | Generated by the scheduler. Different from the accession number. |
| Order control and status | ORC-1 = NW, ORC-5 = SC | ORC-1 = NW, ORC-5 = SC | New order, status scheduled. |
| Patient and visit data | PID, PV1 | PID, PV1, AL1, OBX | The image manager takes the patient demographics from this message. |
No rows match the filter in this table.
Segments in the v2.3.1 message: MSH, PID, PV1, ORC and OBR (repeating) and ZDS. In the v2.5.1 option: MSH, PID, PV1, optional AL1, ORC, TQ1, OBR, optional OBX and IPC. Scheduler and image manager must agree which version they use.
Value conversions to watch
Places where the HL7 value and the DICOM value are not the same thing.
| Item | HL7 side | DICOM side | Rule |
|---|---|---|---|
| Patient name | PID-5: family, given, middle, suffix, prefix, degree | Patient's Name: family, given, middle, prefix, suffix | IHE maps the components by name, unchanged. The degree is absorbed into the suffix. The positions of suffix and prefix are swapped between the two formats, so map by name, not by position. |
| Sex | PID-8: M, F, O, U ... | M, F, O or an empty value | HL7 U (unknown) becomes empty. Any other value must be mapped or left empty, because other DICOM values are illegal. |
| Priority | ORC-7.6 or TQ1-9: S, A, R, P, C, T | STAT, HIGH, ROUTINE, MEDIUM | S gives STAT; A, P and C give HIGH; R gives ROUTINE; T gives MEDIUM. |
| Weight and height | OBX-5 with text "Body Weight" or "Body Height" | Patient's Weight in kg, Patient's Size in m | IHE specifies no coding scheme, only the text and the units. Example: OBX||ST|^BODY WEIGHT||62|kg|||||F. |
| Admission ID | PV1-19, otherwise PID-18 | (0038,0010) and its issuer (0038,0011) | The visit number wins when it is valued. This only works if visit numbers are unique across all account numbers. |
| Patient ID and issuer | PID-3, the Patient Identifier List, which can repeat | Patient ID and Issuer of Patient ID | Components 1 and 4 of PID-3. The older PID-2 and PID-4 are kept only for backward compatibility. |
| Accession number length | OBR-18 or IPC-1 | AccessionNumber | At most 16 characters, which is the limit of the DICOM value representation. |
No rows match the filter in this table.
Order status: from the exam back to HL7
The scheduler tells the order placer how the order is going with a status update (ORM or OMG with ORC-1 `SC`). The status is in ORC-5.
| Status | ORC-5 | When the scheduler sends it |
|---|---|---|
| In progress | IP | After it has processed the first Modality Procedure Step In Progress (an MPPS N-CREATE) for the order. It lets the placer know the exam has started, so it does not cancel it. |
| Completed | CM | When the complete, verified report for the order is available, not when the MPPS is completed. At least one such message is sent, and not before the final verified report of all procedures of the order. |
| Discontinued | DC | When a cancellation arrives after the order is in progress. It is handled as a discontinuation instead. |
No rows match the filter in this table.
A status update cannot be used to request an action such as cancelling an order. A cancel request goes from the placer to the scheduler as a RAD-2 message.
Attributes the modality copies from the worklist
IHE Appendix A lists the attributes that must travel unchanged from the worklist response into the images and the MPPS. If the technologist types them instead, order and study no longer match.
| Attribute | Tag | In the images and the MPPS |
|---|---|---|
| Study Instance UID | (0020,000D) | Copied. The worklist also carries it in the Referenced Study Sequence (0008,1110), which is copied as well. |
| Accession Number | (0008,0050) | Copied. |
| Requested Procedure ID | (0040,1001) | Copied. In the images it is inside the Request Attributes Sequence (0040,0275). |
| Requested Procedure Description | (0032,1060) | Copied. |
| Scheduled Procedure Step ID and Description | (0040,0009), (0040,0007) | Copied. |
| Scheduled Protocol Code Sequence | (0040,0008) | Copied. |
No rows match the filter in this table.
In the MPPS the scheduled values sit inside the Scheduled Step Attributes Sequence (0040,0270). The performed values, such as the Performed Procedure Step ID, are generated by the modality.
Glossary
- HL7 v2
- The standard for text messages between hospital systems. A message is made of segments (PID, ORC, OBR), a segment of fields separated by `|`, and a field of components separated by `^`.
- Segment and field
- PID-5 means field 5 of the PID segment. PID-3.1 means component 1 of field 3.
- Order placer
- The system where an order is entered, usually the EHR. It sends the order and cancels it if needed.
- Order filler, department system scheduler
- The system that carries out the order and schedules the exam, usually the RIS. It creates the accession number, the requested procedure ID and the Study Instance UID.
- Image manager
- The IHE role of the PACS that stores the images and receives the scheduled procedure from the scheduler.
- ORC-1, order control
- The code that says what an order message does: `NW` new order, `CA` cancel, `DC` discontinue, `XO` change, `SC` status change, and others.
- ZDS and IPC
- Two segments that carry the Study Instance UID to the image manager. ZDS is a custom IHE segment for HL7 v2.3.1. IPC is the HL7 v2.5.1 Imaging Procedure Control segment.
- IHE
- Integrating the Healthcare Enterprise. It publishes profiles that say exactly how DICOM and HL7 are used together. The mapping on this page is the IHE one.
Summary
- DICOM and HL7 define no mapping to each other. In radiology the usual one is the IHE Radiology Technical Framework, and sites can deviate from it.
- Orders go from the placer to the scheduler as
ORM^O01(v2.3.1) orOMG^O19(v2.5.1 option). The scheduler sends the scheduled procedure to the PACS asORM^O01withZDS, orOMI^O23withIPC. - The accession number is in
OBR-18(v2.3.1) orIPC-1(v2.5.1), at most 16 characters. The Study Instance UID is inZDS-1orIPC-3. Both are generated by the scheduler, not by the order placer. - Patient data comes from
PIDandPV1:PID-3andPID-5give the patient ID and name. Map name components by name, and map sexUto empty. - Order status comes back as
ORC-5IPafter the first MPPS, andCMonly when the verified report is available.
Common questions
Where does the accession number go in an HL7 order message?
In the IHE Procedure Scheduled message that goes to the PACS it is in OBR-18 (Placer Field 1) for HL7 v2.3.1, and in IPC-1 (Accession Identifier) for the HL7 v2.5.1 option, at most 16 characters. The Filler Order Number in OBR-3 and ORC-3 is a different number. Some interfaces are configured differently, so always check the interface specification of the two systems.
Where does the Study Instance UID travel in HL7?
In the IHE Procedure Scheduled message it is in ZDS-1 for HL7 v2.3.1 and in IPC-3 for the v2.5.1 option. ZDS is a custom segment defined by IHE because HL7 v2.3.1 has no field for it. The scheduler generates the UID, the PACS and the modality use it, and the images carry the same value.
Why are the accession number and Study UID "generated by the scheduler" and not taken from the order?
Because the order placer only knows about the order. The department system scheduler is the order filler: it decides which requested procedures fill the order, schedules them and generates the identifiers for them. It then sends them on in the Procedure Scheduled message and provides them in the modality worklist.
When is it ORM, OMG or OMI?
Under IHE, the order from the placer to the scheduler is ORM^O01 in HL7 v2.3.1 and OMG^O19 in the v2.5.1 option. The scheduled procedure that goes from the scheduler to the PACS is ORM^O01 with a ZDS segment in v2.3.1 and OMI^O23 with TQ1 and IPC segments in the v2.5.1 option. Systems that do not follow IHE may use other messages.
Does an MPPS completed set the order to completed in HL7?
No, not in the IHE mapping. The first MPPS in progress leads to an order status update with ORC-5 IP. The status CM, completed, is only sent when the complete, verified report for the order is available. A completed exam is therefore not a completed order.
Can an HL7 update change the patient ID?
No. IHE says an ADT A08 is the way to update demographic and visit data, but the Patient ID cannot be updated with it. A merge, ADT A40, is how identifiers are combined. An A08 also has to re-send all required values, and a value that is left out keeps its old value.
Is this mapping part of the HL7 or DICOM standard?
No. HL7 and DICOM each define their own format and say nothing about each other. The mapping on this page comes from the IHE Radiology Technical Framework, Volume 2, which is a profile of how to use both. Your own interface may differ, so use the interface specification of the systems involved as the final word.