Το Πρότυπο DICOM και η εφαρμογή του στην Διαχείριση Ιατρικών Εικόνων

Transcript

1 Το Πρότυπο DICOM και η εφαρμογή του στην Διαχείριση Ιατρικών Εικόνων Digital Imaging & Communication in Medicine Βαγγέλης Σακκαλής

2 Τι είναι το DICOM; Πρότυπο για τη μεταφορά ψηφιακών εικόνων Επιτρέπει στους χρήστες την ανάκτηση εικόνων και σχετιζομένων πληροφοριών από απεικονιστικά μηχανήματα με προτυποποιημένο τρόπο που θα είναι ο ίδιος για όλα τα μηχανήματα, ανεξαρτήτως κατασκευαστή. Αποτελείται από μια σειρά κειμένων (12 κύρια μέρη) Κάθε ένα από αυτά να περιγράφει κάποια τμήματα του προτύπου. Το κάθε τμήμα καθορίζεται από τον τίτλο του και έναν αριθμό της μορφής «PS«3.X-YYYY YYYY», όπου το Χ αναφέρεται στον αριθμό του τμήματος και ΥΥΥΥ είναι το έτος δημοσίευσής του. Για παράδειγμα, το τμήμα 2 του προτύπου ονομάζεται «Συμμόρφωση» (Conformance( Conformance) ) και ο αριθμός του είναι PS Vangelis Sakkalis 2

3 Συσχέτιση των Τμήματων του προτύπου Vangelis Sakkalis 3

4 DICOM History ACR- NEMA 1.0 and 2.0 in Το πρότυπο αυτό αναφερόταν σε συνδέσεις από σημείο σε σημείο (point-to-point). DICOM (3.0) first parts in 1993 Continuous Development on DICOM (also with HL7) Το πρότυπο επανασχεδιάστηκε παίρνοντας υπόψη υπάρχοντα πρότυπα δικτύωσης. Αρχικά το πρότυπο αναφερόταν σε ακτινολογικές εικόνες, λόγω όμως του γεγονότος ότι είναι εύκολα προσαρμόσιμο, γρήγορα άρχισε να χρησιμοποιείται και για εικόνες από άλλες απεικονιστικές συσκευές. DICOM (3.0) improvements w. r. t. ACR- NEMA 2.0: Networking and Connection Negotiation More than only Image Transfer Formal Conformance Statements More Complete/ More Acceptance Vangelis Sakkalis 4

5 DICOM History (2) Είναι Standard? Σήμερα, το DICOM είναι εξαιρετικά διαδεδομένο και οι περισσότεροι κατασκευαστές ιατρικών συσκευών το υποστηρίζουν. Δεν είναι ANSI standard (το( το HL7 είναι) Δεν υπάρχει κάποιο εναλλακτικό πρότυπο To DICOM βρίσκεται αυτή τη στιγμή στην έκδοση 3.0. Ανανεώνεται ανά δύο μήνες περίπου! Vangelis Sakkalis 5

6 Τι είναι το DICOM; ; (2) Digital Image Format (Pixel Data + MetaData) Network Image Transfer (Object sending and retrieval, e.g. Images) Open Media Interchange (Common file format) Cross-Vendor Compatibility (SIEMENS, GE, ATL, PHILIPS etc.) Vangelis Sakkalis 6

7 Χαρακτηριστικά του DICOM DICOM domain is communications for imaging-based care DICOM is an Object-based based standard Persistent objects Inter-object referential capability Binary tagged data element format Objects are hierarchically organized Patient / Study / Series (modality) folders DICOM: Persistent Object workflow services over TCP/IP Generally in client-server architecture Object transfer, storage, storage commitment, query and retrieval Media-Interchange (CD, DVD, Floppy, etc.) with clinical directory. Network Archiving Departmental workflow management (worklist( worklist,, performed steps) Broadly used and accepted world-wide wide for many years. Vangelis Sakkalis 7

8 Πώς μοιάζει; Vangelis Sakkalis 8

9 Ορολογία HIS: Hospital Information System RIS: Radiology Information System PACS: Picture Archiving & Communications System Vangelis Sakkalis 9

10 Τυπικό παράδειγμα τοπολογίας συσκευών σε ένα δίκτυο DICOM Vangelis Sakkalis 10

11 Συστήματα Διαχείρισης Ιατρικών Εικόνων (PACS) Acquisition Computer Print Server DICOM Network PACS Central Node (Image Server) Display Workstation Vangelis Sakkalis 11

12 PACS

13 Προϋποθέσεις Επικοινωνία Κοινή Γλώσσα / Πρωτόκολλο DICOM, HL7 Archive/Storage Short Term (RAID) Long Term (DVD-R Tapes Library) Vangelis Sakkalis 13

14 Ιδιαιτερότητες Ιατρικής Εικόνας Multimedia Data 16-bit Grayscale (MR, CT) 8-bit Video Sequences (US, ES) Color Video (Doppler US, ES) Compression Lossless (no data loss) Lossy (data loss) Vangelis Sakkalis 14

15 Ιδιαιτερότητες Ιατρικής Εικόνας (2) Review Station A4 portrait Display One or more in a raw High Resolution (2-4Mpixel) Increased Contrast Luminosity Handling (photo detectors) Soft Copy (Monitor) Dynamic Range (Windowing) Hard Copy (Films) Better Resolution Vangelis Sakkalis 15

16 Communication DICOM Digital Imaging & Communication in Medicine HL7 Health Level 7 Vangelis Sakkalis 16

17 Healthcare Communication Standards (HL7 DICOM) Η Θέση του DICOM σε ένα περιβάλλον Νοσοκομείου Vangelis Sakkalis 17

18 Αλληλεπιδράσεις με εξωτερικό περιβάλλον HL7 RIS HIS PACS DICOM Vangelis Sakkalis 18

19 Τα διάφορα πεδία-περιοχές περιοχές στην Ακτινολογία Το πρότυπο DICOM καλύπτει κύρια τις περιοχές: Modality Acquisition Viewing/Processing Archiving Vangelis Sakkalis 19

20 Τυπικό παράδειγμα λειτουργικότητας Vangelis Sakkalis 20

21 Scenario Hospital Workflow Vangelis Sakkalis 21

22 IHE Scheduled Workflow Patient Registration/Update Order Management (HL7) Worklist Modality Worklist RIS Procedure Scheduled (HL7) Store Images PACS & Archive Storage Commitment List of Images Storage Commitment Modality Performed Procedure Step Performed Step: Status = Completed Performed CT Head Pat Name/ID, Dose, Accession #, Study UID Complete List of Images A Closed Loop Update IS Scheduling Match Procedure with Order Support Billing Based on MPPS Avoid Reading incomplete Procedures Vangelis Sakkalis 22

23 35: Charge Posted Pt Registration: 1 Pt Update: 12 Order Filler ADT 2: Placer Order Management 3: Filler Order Management 36: Account Management 1: Pt registration 12: Pt Update Order Placer 34: Record Audit Event Charge Processor Audit Report Repository 34: Record Audit Event 6: Modality PPS in Progress 7: Modality PPS Completed 20: Creator PPS in Progress 21: Creator PPS Completed 4: Procedure Scheduled 11: Image Availability Query 12: Patient Update 13: Procedure Update Image Display Enterprise Archiving of 20: Creator PPS in Progress 21: Creator PPS Completed Performed Procedure Step Manager Storage Commitment: 10 14: Query Images 15: Query GSPS 16: Retrieve Images 17: Retrieve GSPS 30: Query Key Image Notes 31: Retrieve Key Image Notes Images and Waveforms 6: Modality PPS in Progress 7: Modality PPS Completed 20: Creator PPS in Progress 21: Creator PPS Completed 5: Modality Worklist Provided Storage Commitment: 10 6: Modality PPS in Progress 7: Modality PPS Completed Print Composer Performed Work Status Update: 42 23: Print Request with presentation LUT Image Manager Image Creator Acquisition Modality Print Server 18: Creator Image Stored 19: Creator GSPS Stored 29: Key Image Notes Stored Image Archive 8: Modality Image Stored 9: Modality GSPS Stored 29: Key Image Notes Stored Report Creator Report Manager Report Repository Report Reader 37: GP Worklist Provided 38: GP Workitem Claimed 39: GP Workitem Completed 40: GP PPS In Progress 41: GP PPS Completed 24: Report Submission 25: Report Issuing 26: Query Reports 27: Retrieve Reports Post-Processing Manager Secure Node 32: Authenticate Node Secure Node Time Server Structured Report Export: 28 Enterprise Report Repository External Report Repository Access 33: Maintain Time 26: Query Reports 27: Retrieve Reports

24 Τα τμήματα του DICOM PS 3.1 Introduction and Overview Εισαγωγή Βασικές Έννοιες Συσχετίσεις τμημάτων PS 3.2 Conformance Περιγραφή «Δυνατοτήτων» κάθε συμβατής με DICOM συσκευής Δυνατότητες διασύνδεσης PS 3.3 Information Object Definitions π.χ. Images, Scheduling Lists PS 3.4 Service Class Specifications Ορισμός όλων των υπηρεσιών (Service Classes) π.χ. Αποστολή Εικόνας σε Εκτυπωτή PS 3.5 Data Structures and Encoding Value Representations Vangelis Sakkalis 24

25 Τα τμήματα του DICOM (2) PS 3.6 Data Dictionary Λίστα των Attributes που διαμορφώνουν τα DICOM objects PS 3.7 Message Exchange Εντολές πραγματοποίησης των DICOM Services PS 3.8 Network Communication Support for Message Exchange Ακριβής περιγραφή επικοινωνίας σύμφωνα με το πρωτόκωλο TCP/IP PS 3.9 Point-to to-point Communication Support for Message Exchange Αποσύρθηκε PS 3.10 Media Storage and File Format for Data Interchange File Format Directory Structure (DICOMDIR) Vangelis Sakkalis 25

26 Τα τμήματα του DICOM (3) PS 3.11 Media Storage Application Profiles Περιγραφή ιδιαίτερων χαρακτηριστικών κωδικοποιήσεων ανά απεικοντστικό μοντέλο π.χ. Καρδιολογία, Υπέρηχο PS 3.12 Media Formats and Physical Media for Data Interchange π.χ. Τα υποστηριζόμενα Format των DVD PS 3.13 Print Management Point-to to-point Communication Support Αποσύρθηκε PS 3.14 Grayscale Display Function Standard Maps the pixel values into a standard rage of luminance values for f softcopy display and density values for hardcopy (films) PS 3.15 Security Profiles Διαφορετικά Επίπεδα Ασφάλειας PS 3.16 Content Mapping Resource Templates to facilitate interoperability when using structured reportsr Vangelis Sakkalis 26

27 Συσχέτιση των Τμημάτων του προτύπου Vangelis Sakkalis 27

28 Εξέλιξη Τμημάτων του προτύπου Vangelis Sakkalis 28

29 To DICOM σαν πρότυπο επικοινωνίας Περιγράφει προσυμφωνημένους κανόνες επικοινωνίας (κοινή γλώσσα) Πρωταρχική Χρήση Αποστολή Αναζήτηση και Εκτύπωση εικόνων εξετάσεων Επιπλέον Δυνατότητες Διαχείριση δεδομένων π.χ. Storage Commitment Vangelis Sakkalis 29

30 To DICOM σαν πρότυπο επικοινωνίας (2) Διαδικασία δύο βημάτων Negotiation Process (Association) Τι είδος δεδομένων θα μεταφερθούν Exchange Μεταφορά Έμμεσος Τρόπος καθορισμού έκδοσης (Version) Κάθε μήνυμα συνοδεύεται και από μήνυμα επιβεβαίωσης (acknowledgment) Vangelis Sakkalis 30

31 Many Dimensions of DICOM 1 st level Verification Presence of the other side Storage Services Exchanging Objects (images) Provides the mechanism The Actual Content doesn t matter Vangelis Sakkalis 31

32 Many Dimensions of DICOM (2) 2 nd level Image and Patient Information Management Services Πρόβλημα Τυπογραφικά Λάθη Ορφανές Εικόνες Λύση Κεντρική Εισαγωγή Στοιχείων (HIS)( DICOM Modality Worklist (MWL) Scheduling Modality Performed Procedure Step (MPPS) Enable changes + Status etc Storage Commitment Safe Removal Key Images Vangelis Sakkalis 32

33 Many Dimensions of DICOM (3) 3 rd level Image Quality Πρόβλημα Consistency Presentation State Λύση DICOM Grayscale Standard DICOM Presentation State Service Vangelis Sakkalis 33

34 Many Dimensions of DICOM (3) 4 th level Workflow Management Πρόβλημα Avoid Duplicate Reading Λύση Lock DICOM general-purpose Worklist Vangelis Sakkalis 34

35 Many Dimensions of DICOM (3) 5 th level Security Mechanisms Πρόβλημα Authorized Access Λύση Encryption Electronic Signatures Vangelis Sakkalis 35

36 DICOM workflow Vangelis Sakkalis 36

37 DICOM scenario 1. Select Patient Information (Modality Worklist) 2. Retrieve Prior Images Query/ Retrieve Service 3. Start Procedure MPPS Service 4. Send Images Storage Service 5. Update with exam complete status MPPS Service 6. Read Study General Purpose WL Service 7. Make Images available for Physician Grayscale Standard Presentation State Service 8. Create hardcopy Query/ Retrieve + Print 9. Make Images available for Primary care Physician Security Vangelis Sakkalis 37

38 DICOM scenario (2) Δεν είναι αναγκαία η χρήση όλων των services Πολλές φορές δεν είναι και εφικτή Τα services μπορούν να προσαρμοστούν στις ανάγκες των χρηστών / οργανισμών Υπάρχουν τρόποι να διατηρηθεί το workflow και στις περιπτώσεις που δεν είναι υλοποιημένα κάποια services Vangelis Sakkalis 38

39 DICOM internals Vangelis Sakkalis 39

40 Μοντελοποίηση του κόσμου της Ακτινολογίας στο DICOM (Simplified) Vangelis Sakkalis 40

41 Μοντελοποίηση του κόσμου της Ακτινολογίας στο DICOM Vangelis Sakkalis 41

42 DICOM Attributes Vangelis Sakkalis 42

43 DICOM Information Objects Information Entity (IE) + Information Entity (IE) + Information Entity (IE) Information Information Object Object Definition Definition (IOD) (IOD) Vangelis Sakkalis 43

44 Composite IOD & Normalized IOD Vangelis Sakkalis 44

45 Composite Image IOD Vangelis Sakkalis 45

46 Data Elements Data Organization (GROUP, ELEMENT) 0008,0020 -> > Study Date 0008,0030 -> > Study Time 0010,0010 -> > Patient s Name 0008,0020 -> > Patient ID Data Element Type TYPE 1/ 1C REQUIRED/ CONDITIONAL DATA ELEMENTS TYPE 2/ 2C REQUIRED/ CONDITIONAL DATA ELEMENTS Can be zero length TYPE 3 OPTIONAL DATA ELEMENTS Vangelis Sakkalis 46

47 H έννοια DICOM Service Class Image Storage Sevice Classes Storage Service Class (C-STORE) Query/Retrieve Service Class (C-FIND, C-MOVE, C C-GET) C Management Service Classes Print Management Service Class Basic Worklist Management Verification Service Class C-ECHO Vangelis Sakkalis 47

48 Η έννοια SOP Class Examples: Storage SOP Class : CT Image Storage, MR Image Storage, Study Root Query/Retrieve SOP Class Vangelis Sakkalis 48

49 Η έννοια SOP Class (2) DIMSE IOD (Object) + (Command - Operation) e.g. store, print SOP class + Specific Image Data e.g. MR, CT SOP instance Vangelis Sakkalis 49

50 Μοντέλο επικοινωνίας DICOM εφαρμογών Vangelis Sakkalis 50

51 Μοντέλο επικοινωνίας DICOM εφαρμογών - Ρόλοι Vangelis Sakkalis 51

52 Μοντέλο επικοινωνίας DICOM εφαρμογών - Ρόλοι Vangelis Sakkalis 52

53 Αρχικοποίηση επικοινωνίας DICOM εφαρμογών Vangelis Sakkalis 53

54 Αρχικοποίηση επικοινωνίας DICOM εφαρμογών Vangelis Sakkalis 54

55 DICOM most used Services Vangelis Sakkalis 55

56 Verification Service (C-ECHO) Scope The Verification Service Class defines a service which verifies application level communication between peer DICOM AEs. This verification is accomplished on an established Association using the C-ECHO DIMSE-C service. Use The C-ECHO DIMSE-C service shall be the mechanism used to verify communications between peer DICOM AEs. VERIFICATION SOP CLASS The Verification SOP Class consists of the C- ECHO DIMSE-C service. No associated Information Object Definition is defined. The SOP Class UID shall be " ". Vangelis Sakkalis 56

57 STORAGE SERVICE CLASS (C-STORE) Scope The Storage Service Class defines an application-level class-of-service which facilitates the simple transfer of images in a manner functionally similar to ACR- NEMA It allows one DICOM AE to send images to another. Use Use The C-STORE DIMSE-C Service shall be the mechanism used to transfer SOP Instances between peer DICOM AEs. Vangelis Sakkalis 57

58 STORAGE SERVICE CLASS (2) Vangelis Sakkalis 58

59 STORAGE SERVICE CLASS (3) Storage Considerations COPY not MOVE No indication of long or short term storage Image Storage Types Single Frame US, X-RayX Multi Frame (Single Header) US, NM, XA Vangelis Sakkalis 59

60 STORAGE SERVICE CLASS (4) Conformance Levels Level 0 (Local Conformance) Only a user-defined subset is stored Level 1 (Base Conformance) At least all Required (Type 1 & 2) attributes will be stored Level 2 (Full Conformance) All attributes will be kept Coercion Is used to fill in attributes when the original values are missing Vangelis Sakkalis 60

61 STORAGE SERVICE CLASS (5) Great Specificity Example CR (Computerized) vs DR (Digital) Radiography DR has mandatory attributes describing the so-called hanging protocol Flip, Rotate Invert Grayscale etc. DX (Digital X-ray) X Except from general X-rays, X support is provided for Intra-Oral, Panoramic etc. Vangelis Sakkalis 61

62 STORAGE SERVICE CLASS (6) Not only images can be exchanged, but also objects with no pixel data Structured Reports DICOM Waveforms SC (Secondary Capture) Scanned text Radiation Therapy Plan Vangelis Sakkalis 62

63 Συναλλαγή C-STORESTORE <--- SENT ASSOCIATE-RQ ---> RECEIVED ASSOCIATE-AC <--- SENT C-STORE-RQ ---> RECEIVED C-STORE-RSP <--- SENT RELEASE-RQ ---> RECEIVED RELEASE-RP 1 η Εικόνα <--- SENT ASSOCIATE-RQ ---> RECEIVED ASSOCIATE-AC <--- SENT C-STORE-RQ ---> RECEIVED C-STORE-RSP <--- SENT RELEASE-RQ ---> RECEIVED RELEASE-RP 2 η Εικόνα Vangelis Sakkalis 63

64 Συναλλαγή C-STORE <--- SENT ASSOCIATE-RQ ---> RECEIVED ASSOCIATE-AC <--- SENT C-STORE-RQ ---> RECEIVED C-STORE-RSP 1 η Εικόνα <--- SENT C-STORE-RQ ---> RECEIVED C-STORE-RSP <--- SENT C-STORE-RQ ---> RECEIVED C-STORE-RSP <--- SENT C-STORE-RQ ---> RECEIVED C-STORE-RSP <--- SENT RELEASE-RQ 2 η Εικόνα 3 η Εικόνα 4 η Εικόνα ---> RECEIVED RELEASE-RP Vangelis Sakkalis 64

65 QUERY/RETRIEVE SERVICE CLASS Scope / Use This Service is no intended to provide a comprehensive generalized database query mechanism. The Query/Retrieve Service Class is focused towards basic composite object instance information queries using a small set of common Key Attributes. Messages (DIMCE-C) C) C-FIND, C-MOVE, C-GET services Vangelis Sakkalis 65

66 QUERY/RETRIEVE SERVICE CLASS (2) Both SCU/ SCP Firewall Implementation Attributes U = Unique Key Attribute R = Required Key Attribute Not in C-MOVE, C C-GETC O = Optional Key Attribute Not in C-MOVE, C C-GETC Vangelis Sakkalis 66

67 Query/Retrieve Information Model SOP Class Query/Retrieve Level Patient Root Query/Retrieve (FIND-MOVE-GET) Study Root Query/Retrieve (FIND-MOVE-GET) Patient Study Series Patient Level Study Level Series Level Image Image Level Vangelis Sakkalis 67

68 QUERY/RETRIEVE SERVICE CLASS (3) Patient Root Info about the patient must be provided e.g PatientID, Name, Study Root Info about the study must be provided e.g. Accession ID, Study Date, Only one Root would achieve poor performance Vangelis Sakkalis 68

69 QUERY/RETRIEVE SERVICE CLASS (4) Patient Level Vangelis Sakkalis 69

70 QUERY/RETRIEVE SERVICE CLASS (5) Study Level Vangelis Sakkalis 70

71 QUERY/RETRIEVE SERVICE CLASS (6) Study Root Vangelis Sakkalis 71

72 QUERY/RETRIEVE SERVICE CLASS (7) Search Keys Single Value Matching e.g. provide all Study ID s for SAKKALIS List of UID Matching Use of \ Universal Value Matching zero length = return all matches Wild Card Matching Special characters control the matching ( *,? ) e.g. SA*LIS Range Matching Date/Time matching e.g.<datetime1>-<datetime2> <DateTime2> e.g.<datetime1>- Vangelis Sakkalis 72

73 QUERY/RETRIEVE SERVICE CLASS (8) C-MOVE The C-MOVE operation allows an application to instruct another application entity to transfer stored SOP Instances to another application entity using the C- STORE operation. C-GET GET The C-GET operation allows an application entity to instruct another application entity to transfer stored SOP Instances to the initiating application entity using the C-STORE operation. Vangelis Sakkalis 73

74 Modality Worklist DICOM Modality Worklist makes patient demographic information from RIS available at a modality Dual data entry is eliminated Data Integrity is guaranteed Vangelis Sakkalis 74

75 Modality Worklist (2) Same structure as the Query/ Retrieve SOP class C-FIND is used, filled with specific attributes Examples A worklist consisting of Scheduled Procedure Steps that have been scheduled for a certain time (e.g. today) for the particular modality for a particular referring physician for a particular patient Vangelis Sakkalis 75

76 Modality Worklist (3) Two Different Implementations Real time information retrieval Pressing a button Frequent Updates Polling the IS at regular intervals Offers caching If the interval is too long there may be a cancellation! Too much overload Vangelis Sakkalis 76

77 Modality Worklist (4) Vangelis Sakkalis 77

78 Modality Performed Procedure Step Scope / Use The DICOM Modality Performed Procedure Step actually closes the loop between the IS, PACS and modality. Services N-CREATE Used initially to tell the receiving device that a procedure has started N-SET Used to update the information e.g. Status, results update Vangelis Sakkalis 78

79 Modality Performed Procedure Step (2) Applications Eliminate studies from the Worklist Update the IS, since the study performed can be different than the one scheduled (20-40% depends on the findings) Informs the IS about the status of the exam Can inform on the dose, in case of X-raysX Can indicate the billing price Vangelis Sakkalis 79

80 Storage Commitment Scope / Use Scope / Use The Storage Commitment Service Class enables an Application Entity (AE) acting as an SCU to request another AE acting as an SCP to make the commitment for the safekeeping of the SOP Instances Vangelis Sakkalis 80

81 Storage Commitment (2) Vangelis Sakkalis 81

82 DICOM conformance & Use Profiles Vangelis Sakkalis 82

83 Use Profiles Basic Use Profile Modality Push The modality shall push images for softcopy display or storage. Roles Modality = SCU Archive = SCP Command C-STORE Vangelis Sakkalis 83

84 Use Profiles (2) Extended Use Profile Basic Use Profile + PACS Push The PACS shall push review images for softcopy display to the Modality. Roles Modality = SCP PACS = SCU Command C-STORE Vangelis Sakkalis 84

85 Use Profiles (3) Extended Use Profile (2) Modality Pull The modality shall query the PACS regarding previous performed on a patient. After the modality user finds and selects the appropriate patient-identifying identifying information, the modality will retrieve the study. Roles Modality = SCU PACS = SCP Command DICOM query/retrieve service C-FIND C-MOVE Vangelis Sakkalis 85

86 Use Profiles (4) Extended Use Profile (3) PACS Pull The modality shall answer the PACS query for availability of additional images, series and/or studies in case they were not (yet) sent to the PACS. There are two important reasons for this requirement. May need to recover images when the link between the modality and the PACS has been down for some reason, an event that is not uncommon. Roles Modality = SCP PACS = SCU Command DICOM query/retrieve service C-FIND C-MOVE Vangelis Sakkalis 86

87 Use Profiles (5) Extended Use Profile (4) PACS takes Control The PACS shall take responsibility for images that are sent from the modality to the PACS; as soon as the PACS identifies that the images are committed to be stored, the modality can delete them from its temporary storage. The modality shall provide the DICOM storage commitment service as an SCU to request the guaranteed storage of images within the PACS system. Roles Modality = SCU PACS = SCP Command DICOM storage commitment service N-ACTION N-EVENTREPORT Vangelis Sakkalis 87

88 Use Profiles (6) The Patient Schedule and Procedure Status Profile Exchange Scheduling Information The modality shall retrieve schedule information and patient demographic information so that technologists do not have to re-enter enter this information. The schedule shall be retrieved using, as a minimum, the following keys: modality and/or physical location (room), accession number, patient name and patient ID. Roles Modality = SCU IS = SCP Command DICOM Modality Work List service C-FIND Vangelis Sakkalis 88

89 Use Profiles (7) The Patient Schedule and Procedure Status Profile (2) Exchange Modality status information Roles The modality shall indicate the start of image acquisition and the completion or cancellation of the procedure (end of image acquisition). This information can be used by the IS to prevent other modalities from starting the same procedure. The complete message could be used to indicate that the procedure is eligible for removal from the work list. A list of images that are acquired is exchanged, which could signal the PACS to check whether it received all images that belong to a particular procedure, and take action if all images are not present. Modality = SCU IS = SCP Command DICOM modality performed procedure step service N-CREATE N-SET Vangelis Sakkalis 89

90 DICOM Conformance The Scope and Field of Application PS 3.2 defines principles that implementations claiming conformance to the Standard shall follow. PS 3.2 specifies: the minimum general conformance requirements that must be met by any implementation claiming conformance to the DICOM Standard. Additional conformance requirements for particular features, Service Classes, Information Objects, and communications protocols may be found in the conformance sections of other Parts of the DICOM Standard; PS 3.2 provides : a framework by which conformance information can be placed into a Conformance Statement as dictated by the conformance sections of other Parts of the DICOM Standard. The DICOM Standard does not specify: testing or validation procedures to assess an implementation's conformance to the Standard; testing or validation procedures to assess whether an implementation matches to its Conformance Statement; what optional features, Service Classes, or Information Objects should be supported for a given type of device. Vangelis Sakkalis 90

91 DICOM Conformance (2) Κάθε Συσκευή που υποστηρίζει ότι είναι συμβατή με το DICOM θα πρέπει να παρέχει ένα conformance statement που να περιγράφει: το συντακτικό επικοινωνίας Transfer Syntaxes τον τύπο πληροφορίας που διαχειρίζεται SOP classes πληροφορίες που αφορούν τον τρόπο και τις δυνατότητες διασύνδεσης Όλα τα conformance statements έχουν την ίδια δομή Ο βαθμός λεπτομέρειας όμως διαφέρει από κατασκευαστή σε κατασκευαστή. Vangelis Sakkalis 91

92 DICOM Conformance (3)( To find out if two devices can communicate using DICOM, the two conformance statements must match. Seven steps to compare them: Check and compare the application descriptions Match up the DICOM SOPs Match up the User/ Provider roles Check the number of simultaneous associations Compare the presentation contexts Compare the communication profiles Check for any special object attribute requirements Vangelis Sakkalis 92

93 DICOM Conformance (4) 1 st Step Check and compare the application descriptions What is the type of the Modality? Check Application Data Flow Diagram it illustrates the interaction between the DICOM process in the device and the outside world. Vangelis Sakkalis 93

94 DICOM Conformance (5) Application Entities An Application Entity (AE) is a DICOM process. An AE must have defined: AE title (must be unique) CT_Emergency_Room Network Address (IP) Network Address (IP) Port 104 A modality may have two AE for performing different operations CT_Store CT_Verification Vangelis Sakkalis 94

95 DICOM Conformance (6) 2 nd Step Match up the DICOM SOPs SOP UIDs matching 3 rd Step Similar SOP classes BUT different versions Match up the User/ Provider roles Who talks? Who listens? SCU - SCP Vangelis Sakkalis 95

96 DICOM Conformance (7) 4 th th Step Check the number of simultaneous associations How many simultaneous discussions may be handled? Workflow Implications Performance Implications Example Simultaneous SEND of the same study (images) to the Physicians Workstation & the Archive. If not supported the studies must be sent TWICE in a queue. (SCU case) PRINT many studies from different workstations (SCP case) Vangelis Sakkalis 96

97 DICOM Conformance (8) 5 th Step Match the presentation contexts How the information is encoded? Transfer Syntax Byte Ordering Why? There is a default (Implicit VR, Little Endian) ) = There is also a JPEG compression transfer syntax 6 th Step Compare the communication profiles Which networking standard is used? TCP/IP, ATM, Ethernet etc. What if a hospital has an ATM backbone and want to use Ethernet? There are interconnectors Bridges / Routers Vangelis Sakkalis 97

98 DICOM Conformance (9) Vangelis Sakkalis 98

99 DICOM Conformance (10) Value Representations (VR) VR are DICOM element definitions PN = Patient Name Vangelis^Sakkalis Sakkalis^Vangelis family name complex ^ given name complex ^ middle name ^ name prefix ^ name suffix Example Susan Morrison-Jones, Ph.D., Chief Executive Officer Morrison-Jones^Susan^^^Ph.D., Chief Executive Officer [Two family names; one given name; no middle name; no prefix; two suffixes.] DA = Date A string of characters of the format yyyymmdd Example: = August 22, 1993 Vangelis Sakkalis 99

100 DICOM Conformance (11) Transfer Syntaxes Two Encodings Explicit VR Will include the VR info (0010,0010) PN 17 Sakkalis^Vangelis Implicit VR The VR type must be inferred 0010,0010) 17 Sakkalis^Vangelis ( Vangelis Sakkalis 100

101 DICOM Conformance (12) Transfer Syntaxes (2) Two Representations BYTE ordering Little Endian (W)Intel FIRST = Least Significant Byte A B A B Big Endian Motorola FIRST = Most Significant Byte B A B A Vangelis Sakkalis 101

102 DICOM Conformance (13) 7 th Step Check for any additional/ unusual or special object attribute requirements How certain attributes are used? Example 3D reconstruction may fail if certain attributes are missing! Simple Viewing may have issues if the series information is not provided! If PatientID is not supplied there may be rejection from the archive! DICOM can even allow for private attributes Vangelis Sakkalis 102

103 DICOM Performance Some say DICOM is inherently slow Can be, if poorly implemented and not properly tuned Some implementers make no effort to optimize for the deployment environment & underlying TCP stack Consider different bandwidth/fragmentation LAN with switched 10/100/1000 Ethernet WAN over cable or DSL Dial-up modem Satellite DICOM can approach the speed of raw sockets, just as ftp and http can, if properly implemented Vangelis Sakkalis 103

104 DICOM Performance (2) Don t open a new association for each image Avoids TCP/IP connection establishment delay Avoids association negotiation Consider maintaining an open pool of associations with timeouts Don t negotiate more SOP Classes/Transfer Syntaxes than you need to transfer Do avoid buffer copying and user/kernel context switches, try memory mapped files. Consider lossless compression tradeoff between reduction in transfer time (fewer bits) vs. additional decompression time on client server-side compression avoided if already stored in (same) compressed form; also reduces disk bandwidth required Choose transfer syntax with fastest possible and least resource intensive decompression times Compare JPEG lossless, JPEG-LS and J2K in this regard Vangelis Sakkalis 104

105 DICOM Compression Schemes Supported RLE JPEG lossless and lossy JPEG-LS more efficient, fast lossless JPEG 2000 progressive Deflate (zip/ gzip) for non-image objects Vangelis Sakkalis 105

106 DICOM Compression (2) In practice Lossless JPEG for cardiac angio multi-frame 512x512x8, 1024x1024x10 CT/MR mostly on media rather than over network 256x256 to 1024x1024, bits RLE/lossless/lossy JPEG for Ultrasound 640x480 single and multiframe 8 bits gray/rgb, text Vangelis Sakkalis 106

107 Bibliography - Resources Internet sites for DICOM Official site of DICOM: :// Diploma Thesis με θέμα το DICOM (στα( Γερμανικά): ://cui.unige.ch/~muellerh/dicom/diplom.html DICOM Cook Book, Bas Revet,, PHILIPS, 1997 (ftp://ftp.philips.com/pub/ms/dicom/dicom_information/cookbook.p df) PACS Picture Archiving and Communication Systems in Biomedical Imaging,, H.K Huang,, 1996, VHC Publishers Inc.. (ISBN ) PACSView: ://www- ang.kfunigraz kfunigraz.ac.at/~ /~zeilinge/pacsview/download.html Osiris Viewer: :// Java Applet Viewer: ://wwwusers.imaginet.fr/~sderhy/dicomapplet.html DICOM toolkit: :// Vangelis Sakkalis 107