DICOM

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/08/21 11:09:57」(JST)

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DICOM(ダイコム）とは、Digital Imaging and COmmunication in Medicineの略で、米国放射線学会 (ACR) と北米電子機器工業会 (NEMA) が開発した、CTやMRI、CRなどで撮影した医用画像のフォーマットと、それらの画像を扱う医用画像機器間の通信プロトコルを定義した標準規格のことである。

画像規格としてのDICOM

基本的には撮影直後の生成直後はビットマップ系のRAWフォーマットを用いる場合が多く、DICOMサーバなどへの短期保存時にはRAWフォーマットのまま、もしくはRLE圧縮やロスレスJPEGなどの劣化のない可逆フォーマットを用いる場合が多く、長期保存時にはロッシーJPEGなど非可逆フォーマットを用いる場合が多い。また、DICOMサーバからDICOMビューアへの配信時には、通信効率を上げるためにJPEG系のフォーマットを利用する場合が多く、一部ではJPEG 2000や独自フォーマットへ内包データを変換して配信している場面も見受けられる。

ただし、DICOMの仕様では、規格の特性上、画像を主とするものの、画像に限らず、ありとあらゆるデータを内包できるようになっている（コンテナフォーマット）。内包物がある場合はDICOMファイル内のタグ情報に、内包物のフォーマット名及びデータ長を記載するようになっており、加えて上記のタグ情報が複数ある場合は画像データも複数枚が内包されている状態となる。これをマルチフレームという。

以上のように、画像以外の情報も内包可能なため、超音波診断装置などでは、画像に加えて心拍などの音声データを内包している場合もある。また、この音声データと、前述のマルチフレーム等の画像データをパラパラアニメのようにし、同時再生することにより音声付き動画データとして扱うことも可能である。

通信規格としてのDICOM

DICOMの通信仕様については、RS-232などのシリアルケーブルを用いた通信など、幅広い通信手段を網羅するため、OSI参照モデルに準拠している。

しかし、1990年代中ごろからインターネットが爆発的に普及したことにより、OSI参照モデルではなく、RFC 1122（通称DARPAモデル）に準拠した製品が一般化することとなった。

この情勢の変化に対し、DICOMの最新仕様では、OSI参照モデルに準じたDICOM通信プロトコルをTCP/IPを用いてカプセル化する、という方法で大幅な仕様変更を回避している。

しかし、DICOM通信プロトコルでは、カプセル化によるオーバーヘッドが生じ、TCP/IPであればネットワークカード上のハードウェアで処理されるパケットの再構成処理などもカプセル化されたデータについてはソフトウェアで実現しなければならず、HTTPなどの純粋にTCP/IPを用いた通信プロトコルに比べ、負荷や速度などは大幅に劣る。このため、一部製品では、他社製品との通信にはDICOMに準拠するものの、自社製品間における通信は独自プロトコルを用いている場合も多く見受けられる。

その他の仕様

英語版に仕様書のリストが掲載されているので参照のこと。

印刷・データ保存に関する規定や、個人情報になりうる性質のデータである以上セキュリティに関する仕様も盛り込まれている。またDICOMフォーマットへのWebアクセスに関する規定もある。

問題点

実際の医療現場では、「DICOM準拠」をうたっているにも関わらず、実際にはメーカーによって画像フォーマットやテキストデータなどの扱いが異なっている（いわゆる「メーカー方言」が存在する）ことが多い。そのために相互運用が行えないケースも多く、病院関係者から問題視されている。

またDICOMのフォーマットは「人間の医療情報」を保存することに特化しているため、人間以外の動物の医用画像（例：競走馬のレントゲン写真など）をDICOMで管理するためには病院側での項目の読み替えなどの手間が必要になる。この点についても、動物医療に携わる人間からは改善を求める意見があり、近年ではそういったニーズに対応して動物医療向けに強引にカスタマイズされたシステムも登場してきている。ただし、DICOM規格に準拠するという意味では、DICOM規格ではプライベートタグという独自拡張を認めており、その範囲内で適用すべきである。

関連項目

• CT
• MRI
• CR
• PET
• PDI
• OsiriX

外部リンク

• DICOM Homepage
  • NEMA DICOM Homepage(英語)
• DICOM 日本語訳：
  • 社団法人 日本画像医療システム工業会(JIRA) DICOMの世界
• 解説:
  • "コニカミノルタ　DICOMについて（PDF) "

脚注

wiki en

[Wiki en表示]

Digital Imaging and Communications in Medicine (DICOM) is a standard for handling, storing, printing, and transmitting information in medical imaging. It includes a file format definition and a network communications protocol. The communication protocol is an application protocol that uses TCP/IP to communicate between systems. DICOM files can be exchanged between two entities that are capable of receiving image and patient data in DICOM format. The National Electrical Manufacturers Association (NEMA) holds the copyright to this standard. It was developed by the DICOM Standards Committee, whose members are also partly members of NEMA.

DICOM enables the integration of scanners, servers, workstations, printers, and network hardware from multiple manufacturers into a picture archiving and communication system (PACS). The different devices come with DICOM conformance statements which clearly state which DICOM classes they support. DICOM has been widely adopted by hospitals and is making inroads in smaller applications like dentists' and doctors' offices.

DICOM is known as NEMA standard PS3, and as ISO standard 12052:2006 "Health informatics -- Digital imaging and communication in medicine (DICOM) including workflow and data management".

• PS 3.20: Transformation of DICOM to and from HL7 Standards PDF (570 KB)

History

Front page of ACR/NEMA 300, version 1.0, which was released in 1985

DICOM is the First version of a standard developed by American College of Radiology (ACR) and National Electrical Manufacturers Association (NEMA).

In the beginning of the 1980s, it was very difficult for anyone other than manufacturers of computed tomography or magnetic resonance imaging devices to decode the images that the machines generated. Radiologists and medical physicists wanted to use the images for dose-planning for radiation therapy. ACR and NEMA joined forces and formed a standard committee in 1983. Their first standard, ACR/NEMA 300, was released in 1985. Very soon after its release, it became clear that improvements were needed. The text was vague and had internal contradictions.

In 1988 the second version was released. This version gained more acceptance among vendors. The image transmission was specified as over a dedicated 2 pair cable (EIA-485). The first demonstration of ACR/NEMA V2.0 interconnectivity technology was held at Georgetown University, May 21–23, 1990. Six companies participated in this event, DeJarnette Research Systems, General Electric Medical Systems, Merge Technologies, Siemens Medical Systems, Vortech (acquired by Kodak that same year) and 3M. Commercial equipment supporting ACR/NEMA 2.0 was presented at the annual meeting of the Radiological Society of North America (RSNA) in 1990 by these same vendors. Many soon realized that the second version also needed improvement. Several extensions to ACR/NEMA 2.0 were created, like Papyrus (developed by the University Hospital of Geneva, Switzerland) and SPI (Standard Product Interconnect), driven by Siemens Medical Systems and Philips Medical Systems.

The first large-scale deployment of ACR/NEMA technology was made in 1992 by the US Army and Air Force, as part of the MDIS (Medical Diagnostic Imaging Support) program based at f Ft. Detrick, Maryland. Loral Aerospace and Siemens Medical Systems led a consortium of companies in deploying the first US military PACS (Picture Archiving and Communications System) at all major Army and Air Force medical treatment facilities and teleradiology nodes at a large number of US military clinics. DeJarnette Research Systems and Merge Technologies provided the modality gateway interfaces from third party imaging modalities to the Siemens SPI network. The Veterans Administration and the Navy also purchased systems off this contract.

In 1993 the third version of the standard was released. Its name was then changed to "DICOM" so as to improve the possibility of international acceptance as a standard. New service classes were defined, network support added and the Conformance Statement was introduced. Officially, the latest version of the standard is still 3.0. However, it has been constantly updated and extended since 1993. Instead of using the version number, the standard is often version-numbered using the release year, like "the 2007 version of DICOM".

While the DICOM standard has achieved a near universal level of acceptance amongst medical imaging equipment vendors and healthcare IT organizations, the standard has its limitations. DICOM is a standard directed at addressing technical interoperability issues in medical imaging. It is not a framework or architecture for achieving a useful clinical workflow. RSNA's Integrating the Healthcare Enterprise (IHE) initiative layered on top of DICOM (and HL-7) provides this final piece of the medical imaging interoperability puzzle.

Derivations

There are some derivations from the DICOM standard into other application areas. These include:

• DICONDE - Digital Imaging and Communication in Nondestructive Evaluation, was established in 2004 as a way for nondestructive testing manufacturers and users to share image data.
• DICOS - Digital Imaging and Communication in Security was established in 2009 to be used for image sharing in airport security.

Data format

DICOM differs from some, but not all, data formats in that it groups information into data sets. That means that a file of a chest x-ray image, for example, actually contains the patient ID within the file, so that the image can never be separated from this information by mistake. This is similar to the way that image formats such as JPEG can also have embedded tags to identify and otherwise describe the image.

A DICOM data object consists of a number of attributes, including items such as name, ID, etc., and also one special attribute containing the image pixel data (i.e. logically, the main object has no "header" as such: merely a list of attributes, including the pixel data). A single DICOM object can have only one attribute containing pixel data. For many modalities, this corresponds to a single image. But note that the attribute may contain multiple "frames", allowing storage of cine loops or other multi-frame data. Another example is NM data, where an NM image, by definition, is a multi-dimensional multi-frame image. In these cases, three- or four-dimensional data can be encapsulated in a single DICOM object. Pixel data can be compressed using a variety of standards, including JPEG, JPEG Lossless, JPEG 2000, and Run-length encoding (RLE). LZW (zip) compression can be used for the whole data set (not just the pixel data), but this has rarely been implemented.

DICOM uses three different Data Element encoding schemes. With Explicit Value Representation (VR) Data Elements, for VRs that are not OB, OW, OF, SQ, UT, or UN, the format for each Data Element is: GROUP (2 bytes) ELEMENT (2 bytes) VR (2 bytes) LengthInByte (2 bytes) Data (variable length). For the other Explicit Data Elements or Implicit Data Elements, see section 7.1 of Part 5 of the DICOM Standard.

The same basic format is used for all applications, including network and file usage, but when written to a file, usually a true "header" (containing copies of a few key attributes and details of the application which wrote it) is added.

Image display

To promote identical grayscale image display on different monitors and consistent hard-copy images from various printers, the DICOM committee developed a lookup table to display digitally assigned pixel values. To use the DICOM grayscale standard display function (GSDF), images must be viewed (or printed) on devices that have this lookup curve or on devices that have been calibrated to the GSDF curve.

Value representations

Extracted from Chapter 6.2 of PS 3.5-2007: Data Structure and Encoding PDF (1.43 MiB)

Value Representation	Description
AE	Application Entity
AS	Age String
AT	Attribute Tag
CS	Code String
DA	Date
DS	Decimal String
DT	Date/Time
FL	Floating Point Single (4 bytes)
FD	Floating Point Double (8 bytes)
IS	Integer String
LO	Long String
LT	Long Text
OB	Other Byte
OF	Other Float
OW	Other Word
PN	Person Name
SH	Short String
SL	Signed Long
SQ	Sequence of Items
SS	Signed Short
ST	Short Text
TM	Time
UI	Unique Identifier
UL	Unsigned Long
UN	Unknown
US	Unsigned Short
UT	Unlimited Text

In addition to a Value Representation, each attribute also has a Value Multiplicity to indicate the number of data elements contained in the attribute. For character string value representations, if more than one data element is being encoded, the successive data elements are separated by the backslash character "\".

Services

DICOM consists of many different services, most of which involve transmission of data over a network, and the file format below is a later and relatively minor addition to the standard.

Store

The DICOM Store service is used to send images or other persistent objects (structured reports, etc.) to a picture archiving and communication system (PACS) or workstation.

Storage commitment

The DICOM storage commitment service is used to confirm that an image has been permanently stored by a device (either on redundant disks or on backup media, e.g. burnt to a CD). The Service Class User (SCU: similar to a client), a modality or workstation, etc., uses the confirmation from the Service Class Provider (SCP: similar to a server), an archive station for instance, to make sure that it is safe to delete the images locally.

Query/Retrieve

This enables a workstation to find lists of images or other such objects and then retrieve them from a picture archiving and communication system.

Modality worklist

This enables a piece of imaging equipment (a modality) to obtain details of patients and scheduled examinations electronically, avoiding the need to type such information multiple times (and the mistakes caused by retyping).

Modality performed procedure step

A complementary service to Modality Worklist, this enables the modality to send a report about a performed examination including data about the images acquired, beginning time, end time, and duration of a study, dose delivered, etc. It helps give the radiology department a more precise handle on resource (acquisition station) use. Also known as MPPS, this service allows a modality to better coordinate with image storage servers by giving the server a list of objects to send before or while actually sending such objects.

Printing

The DICOM Printing service is used to send images to a DICOM Printer, normally to print an "X-Ray" film. There is a standard calibration (defined in DICOM Part 14) to help ensure consistency between various display devices, including hard copy printout.

Off-line media (files)

The off-line media files correspond to Part 10 of the DICOM standard. It describes how to store medical imaging information on removable media. Except for the data set containing, for example, an image and demography, it's also mandatory to include the File Meta Information.

DICOM restricts the filenames on DICOM media to 8 characters (some systems wrongly use 8.3, but this does not conform to the standard). No information must be extracted from these names (PS3.10 Section 6.2.3.2). This is a common source of problems with media created by developers who did not read the specifications carefully. This is a historical requirement to maintain compatibility with older existing systems. It also mandates the presence of a media directory, the DICOMDIR file, which provides index and summary information for all the DICOM files on the media. The DICOMDIR information provides substantially greater information about each file than any filename could, so there is less need for meaningful file names.

DICOM files typically have a .dcm file extension if they are not part of a DICOM media (which requires them to be without extension).

The MIME type for DICOM files is defined by RFC 3240 as application/dicom.

The Uniform Type Identifier type for DICOM files is org.nema.dicom.

There is also an ongoing media exchange test and "connectathon" process for CD media and network operation that is organized by the IHE organization. MicroDicom is free Windows software for reading DICOM data.

Application areas

Extracted from Chapter C.7.3.1.1.1 of PS 3.3-2011: Information Object Definitions PDF (6.51 MiB)

Modality	Description	Status
AS	Modality of type Angioscopy	Retired
BI	Modality of type Biomagnetic Imaging
CD	Modality of type Color Flow Doppler	Retired 2008
CF	Modality of type Cinefluorography	Retired
CP	Modality of type Colposcopy	Retired
CR	Modality of type Computed Radiography
CS	Modality of type Cystoscopy	Retired
CT	Modality of type Computed Tomography
DD	Modality of type Duplex Doppler	Retired 2008
DG	Modality of type Diaphanography
DM	Modality of type Digital Microscopy	Retired
DS	Modality of type Digital Subtraction Angiography	Retired
DX	Modality of type Digital Radiography
EC	Modality of type Echocardiography	Retired
ECG	Modality of type Electrocardiograms
EM	Modality of type Electron Microscope
ES	Modality of type Endoscopy
FA	Modality of type Fluorescein Angiography	Retired
FS	Modality of type Fundoscopy	Retired
GM	Modality of type General Microscopy
HC	Modality of type Hard Copy
IO	Modality of type Intra-oral Radiography
LP	Modality of type Laparoscopy	Retired
LS	Modality of type Laser Surface Scan
MA	Modality of type Magnetic Resonance Angiography	Retired
MG	Modality of type Mammography
MR	Modality of type Magnetic Resonance
MS	Modality of type Magnetic Resonance Spectroscopy	Retired
NM	Modality of type Nuclear Medicine
OP	Modality of type Ophthalmic Photography
OPM	Modality of type Ophthalmic Mapping
OPR	Modality of type Ophthalmic Refraction
OPV	Modality of type Ophthalmic Visual Field
OT	Modality of type Other
PT	Modality of type Positron Emission Tomography (PET)
PX	Modality of type Panoramic X-Ray
RD	Modality of type Radiotherapy Dose (a.k.a. RTDOSE)
RF	Modality of type Radio Fluoroscopy
RG	Modality of type Radiographic Imaging (conventional film screen)
RTIMAG	Modality of type Radiotherapy Image
RP	Modality of type Radiotherapy Plan (a.k.a. RTPLAN)
RS	Modality of type Radiotherapy Structure Set (a.k.a. RTSTRUCT)
RT	Modality of type Radiation Therapy
SM	Modality of type Slide Microscopy
SR	Modality of type Structured Reporting
ST	Modality of type Single-Photon Emission Computed Tomography	Retired 2008
TG	Modality of type Thermography
US	Modality of type Ultrasound
VF	Modality of type Videofluorography	Retired
VL	Modality of type Visible Light
XA	Modality of type X-Ray Angiography
XC	Modality of type External Camera (Photography)

Port numbers over IP

DICOM have reserved the following TCP and UDP port numbers by the Internet Assigned Numbers Authority (IANA):

• 104 well-known port for DICOM over Transmission Control Protocol (TCP) or User Datagram Protocol (UDP). Since 104 is in the reserved subset, many operating systems require special privileges to use it.
• 2761 registered port for DICOM using Integrated Secure Communication Layer (ISCL) over TCP or UDP
• 2762 registered port for DICOM using Transport Layer Security (TLS) over TCP or UDP
• 11112 registered port for DICOM using standard, open communication over TCP or UDP

The standard recommends but does not require the use of these port numbers.

Disadvantages

According to a paper presented at an international symposium in 2008, the DICOM standard has problems related to data entry. "A major disadvantage of the DICOM Standard is the possibility for entering probably too many optional fields. This disadvantage is mostly showing in inconsistency of filling all the fields with the data. Some image objects are often incomplete because some fields are left blank and some are filled with incorrect data."

HL7

DICOM is a standard for handling, storing, printing, and transmitting information in medical imaging. The communication protocol is an application protocol that uses TCP/IP to communicate between systems. DICOM files can be exchanged between two entities that are capable of receiving image and patient data in DICOM format. The National Electrical Manufacturers Association (NEMA) holds the copyright to this standard. It was developed by the DICOM Standards Committee, whose members are also partly members of NEMA.

Health Level Seven (HL7), is a non-profit organization involved in the development of international healthcare informatics interoperability standards.[1] "HL7" also refers to some of the specific standards created by the organization (e.g., HL7 v2.x, v3.0, HL7 RIM). The HL7 Strategic Initiatives document is a business plan for our products and services and was designed specifically to meet the business needs of its members and stakeholders. Derived from collaborative efforts with its members, government and non-government agencies and other standards development organizations, the Strategic Initiatives are five high-level organizational strategies that are supported by a detailed tactical plan with clearly defined objectives, milestones, and metrics for success.

Both of the standards are focused on the data exchange and the data compatibility. Among many standards for the syntax, HL7 and DICOM are most successful. However, everything could not be handled by HL7 solely. DICOM is good for radiology images, but, other clinical images are already handled by other ‘lighter’ data formats like JPEG, TIFF. So, it is not realistic to use only one standard for every area of clinical information.

Opening the HL7 and DICOM standards in order to foster the integrated use of persistent health information objects is proposed as a step towards the creation of the health information infrastructure.

IHE

Integrating the Healthcare Enterprise (IHE) was founded in 1997 by members of the Radiological Society of North America (RSNA) and the Healthcare Information and Management Systems Society for the purpose of improving interoperability between information systems. The IHE initiative was charged with the task of using existing standards of health care data communication such as DICOM and HL7 to improve exchange of medical information beyond the radiology department at the hospital level or health systems level. Just as radiologists were confronted in the past with imaging connectivity incompatibilities, entire health systems are continually faced with the task of connecting multiple disparate information systems in which the only reliable communications pathway is the paper printout.

The IHE working group is a panel made up of industry representatives from medical informatics and imaging vendors as well as medical professionals. Their primary focus is to develop a common information model of medical information exchange. The devised IHE technical framework consists of a common lexicon that defines specific medical information transactions using the existing standards of medical information exchange (DICOM and HL7). The specifics of these transactions have been worked out in great detail so that vendors have been free to independently develop solutions to meet the goals of the technical framework. In the year 2001 to 2002, 30 companies took part in the testing and implementation of the IHE demonstrations.

See also

DICOM Software

• 3DSlicer - a free, open source software package for image analysis and scientific visualization, with the integrated support of components of DICOM standard
• GDCM - Grassroots DICOM library for medical files
  GDCM sample as PNG
• Ginkgo CADx Cross-platform DICOM viewer
• MicroDicom - DICOM viewer for Windows
• OsiriX - Image processing application dedicated to DICOM images
• Orthanc - Lightweight, RESTful DICOM store
• XnView - supports .dic / .dicom for MIME type application/dicom

Medical Records Standards Initiatives, Standards and Organizations

• Health Level 7, a non-profit organization involved in the development of international healthcare informatics interoperability standards
• Integrating the Healthcare Enterprise (IHE), an industry sponsored non-profit organization based in the US state of Illinois

References

External links

• DICOM standard, NEMA.
• Brief introduction to DICOM
• Medical Image FAQ part 2 - Standard formats including DICOM.
• Medical Image FAQ part 8 - Contains a long list DICOM software.
• DICOM Tutorial - DICOM is Easy.

UpToDate Contents

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• 1. 産婦人科における超音波検査 ultrasound examination in obstetrics and gynecology

English Journal

• Medical data sheet in safe havens - A tri-layer cryptic solution.

• Praveenkumar P1, Amirtharajan R2, Thenmozhi K3, Balaguru Rayappan JB4.
• Computers in biology and medicine.Comput Biol Med.2015 Jul 1;62:264-76. doi: 10.1016/j.compbiomed.2015.04.031. Epub 2015 Apr 28.
• Secured sharing of the diagnostic reports and scan images of patients among doctors with complementary expertise for collaborative treatment will help to provide maximum care through faster and decisive decisions. In this context, a tri-layer cryptic solution has been proposed and implemented on Dig
• PMID 25966921

• Computer-assisted interpretation of planar whole-body bone scintigraphy in patients with newly diagnosed prostate cancer.

• Petersen LJ1, Mortensen JC, Bertelsen H, Zacho HD.
• Nuclear medicine communications.Nucl Med Commun.2015 Jul;36(7):679-85. doi: 10.1097/MNM.0000000000000307.
• PURPOSE: The aim of this study was to compare the diagnostic properties of EXINI Bone in newly diagnosed prostate cancer in comparison with expert reading.MATERIALS AND METHODS: Bone scintigraphy was performed in consecutive patients referred for staging at three clinics (342 patients with DICOM fil
• PMID 25757196

Japanese Journal

• 生理検査システム (特集 検査システムの更新に備える)

• 三浦 純子
• 臨床検査 59(3), 232-237, 2015-03
• NAID 40020369534

• 医用画像の特徴を利用したボリュームレンダリング高速化に関する研究 (MEとバイオサイバネティックス)

• 笠井 康希,濱本 和彦
• 電子情報通信学会技術研究報告 = IEICE technical report : 信学技報 114(408), 127-130, 2015-01-22
• NAID 40020366151

Related Links

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DICOMについての基礎知識を紹介しています。DICOMとは英語Digital Imaging and Communications in Medicineの略称で、医用画像の画像規格及び通信プロトコルを決める全世界共通仕様です。医療に関する画像データの管理・転送・保存 ...

• 一般社団法人 日本画像医療システム工業会【JIRA ...

2016/7/22 オブジェクト識別子（DICOM-UID）を新たに追加発行しました。 2016/5/24 オブジェクト識別子（DICOM-UID）を新たに追加発行しました。 2016/3/14 オブジェクト識別子（DICOM-UID）を新たに追加発行しました。 2016/1/11 ...

Related Pictures

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★リンクテーブル★

リンク元	「医用画像規格」
関連記事	「DIC」

「医用画像規格」

　　[★]

英

standard for medical images

関

DICOM ダイコム, JPEG ジェーペグ

「DIC」

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