dcmodify(1) OFFIS DCMTK dcmodify(1) NAME dcmodify - Modify DICOM files SYNOPSIS dcmodify [options] dcmfile-in... DESCRIPTION dcmodify is a tool that allows one to modify, insert and delete tags and items in DICOM files. Sequences and tags with a value multiplicity > 1 are also supported. Metaheader information and the tag's VR can not be modified directly by dcmodify at this time. In addition to tag modifications, dcmod- ify makes available some input options - forcing dcmodify to handle its in- put files as the user specifies - and output options to control the output format of the resulting files. In case multiple modifications have to be performed, dcmodify does the mod- ifications in the same order as they appear on the command line. Please note that dcmodify does not check whether a given value matches its value representation (VR). Usually, an error message is printed but generally the user should take care of the right VR usage. If dcmodify doesn't know the tag it should insert, then the tag's VR is set to UN and the value provided on command line is interpreted as being a se- ries of hexadecimal numbers (like they are provided for VR=OB). Please in- sert these tags into the dictionary to avoid this behavior. Also, specify- ing the -iun option, it is possible to force dcmodify to leave UN values untouched. Using option -u lets dcmodify saving all VR=UN attributes as OB. dcmodify is able to work with so-called tag paths to access tags in se- quences. The (pseudo-formalized) syntax is {sequence[item-no].}*element where 'sequence' is a sequence tag like (0008,1111) or a dictionary name for a tag. 'item-no' describes the item number to be accessed (counting from zero). 'element' defines the target tag to work on. A tag can either be specified directly as (0010,0010) or through the corresponding dictio- nary name 'PatientName'. The '*' denotes that you can repeat sequence statements to access deeper levels in DICOM files (see EXAMPLES section). For 'item-no', also a wildcard character '*' can be used selecting all items in surrounding sequence (see section WILDCARDS below). When inserting tag paths consisting of multiple nodes (i.e. not a single element) using the -i option, any missing path elements (items, sequences, leaf elements) are inserted automatically when missing. That does not work for item wildcards: When no single item exists in the surrounding sequence dcmodify of course can't decide, how many items should be generated. How- ever, if specifying an item number like '5', all 6 items (counted from zero) can be (and are) automatically generated in insert mode. If already 2 items would exist, the rest (4) would be inserted. dcmodify does not work on directories, i.e. the parameter dcmfile-in... must not include directory names. Please note that there are some issues concerning the modification of pri- vate tags (see PRIVATE TAGS section) and for changing UIDs (CHANGING UIDs section). PARAMETERS dcmfile-in DICOM input filename(s) to be modified ("-" for stdin/stdout) OPTIONS general options -h --help print this help text and exit --version print version information and exit --arguments print expanded command line arguments -q --quiet quiet mode, print no warnings and errors -v --verbose verbose mode, print processing details -d --debug debug mode, print debug information -ll --log-level [l]evel: string constant (fatal, error, warn, info, debug, trace) use level l for the logger -lc --log-config [f]ilename: string use config file f for the logger input options input file format: +f --read-file read file format or data set (default) +fo --read-file-only read file format only -f --read-dataset read data set without file meta information +fc --create-file create file format if file does not exist input transfer syntax: -t= --read-xfer-auto use TS recognition (default) -td --read-xfer-detect ignore TS specified in the file meta header -te --read-xfer-little read with explicit VR little endian TS -tb --read-xfer-big read with explicit VR big endian TS -ti --read-xfer-implicit read with implicit VR little endian TS parsing of odd-length attributes: +ao --accept-odd-length accept odd length attributes (default) +ae --assume-even-length assume real length is one byte larger automatic data correction: +dc --enable-correction enable automatic data correction (default) -dc --disable-correction disable automatic data correction bitstream format of deflated input: +bd --bitstream-deflated expect deflated bitstream (default) +bz --bitstream-zlib expect deflated zlib bitstream processing options backup input files: --backup backup files before modifying (default) -nb --no-backup don't backup files (DANGEROUS) insert mode: -i --insert "[t]ag-path=[v]alue" insert (or overwrite) path at position t with value v -if --insert-from-file "[t]ag-path=[f]ilename" insert (or overwrite) path at position t with value from file f -nrc --no-reserv-check do not check private reservations modify mode: -m --modify "[t]ag-path=[v]alue" modify tag at position t to value v -mf --modify-from-file "[t]ag-path=[f]ilename" modify tag at position t to value from file f -ma --modify-all "[t]ag=[v]alue" modify ALL matching tags t in file to value v erase mode: -e --erase "[t]ag-path" erase tag/item at position t -ea --erase-all "[t]ag" erase ALL matching tags t in file -ep --erase-private erase ALL private data from file unique identifier: -gst --gen-stud-uid generate new Study Instance UID -gse --gen-ser-uid generate new Series Instance UID -gin --gen-inst-uid generate new SOP Instance UID -nmu --no-meta-uid do not update metaheader UIDs if related UIDs in the dataset are modified error handling: -ie --ignore-errors continue with file, if modify error occurs -imt --ignore-missing-tags treat 'tag not found' as success when modifying or erasing in files -iun --ignore-un-values do not try writing any values to elements having a VR of UN output options output file format: +F --write-file write file format (default) -F --write-dataset write data set without file meta information output transfer syntax: +t= --write-xfer-same write with same TS as input (default) +te --write-xfer-little write with explicit VR little endian TS +tb --write-xfer-big write with explicit VR big endian TS +ti --write-xfer-implicit write with implicit VR little endian TS post-1993 value representations: +u --enable-new-vr enable support for new VRs (UN/UT) (default) -u --disable-new-vr disable support for new VRs, convert to OB group length encoding: +g= --group-length-recalc recalculate group lengths if present (default) +g --group-length-create always write with group length elements -g --group-length-remove always write without group length elements length encoding in sequences and items: +le --length-explicit write with explicit lengths (default) -le --length-undefined write with undefined lengths data set trailing padding (not with --write-dataset): -p= --padding-retain do not change padding (default if not --write-dataset) -p --padding-off no padding (implicit if --write-dataset) +p --padding-create [f]ile-pad [i]tem-pad: integer align file on multiple of f bytes and items on multiple of i bytes PRIVATE TAGS There are some issues you have to consider when working with private tags. However, the insertion or modification of a reservation tag (gggg,00xx) should always work. Insertions If you wish to insert a private tag (not a reservation with gggg,00xx), be sure, that you've listed it in your dictionary (see <docdir>/datadict.txt for details). If it's not listed, dcmodify will insert it with VR=UN. Also, for some cases insertion may even fail for some values. If you've got your private tag in the dictionary, dcmodify acts as follows: When it finds a reservation in the tag's enclosing dataset, whose private creator matches, insertion is done with the VR found in the dictionary and the value given on command line. But if the private creator doesn't match or none is set, dcmodify will return with an error. If a private tag should be inserted regardless whether a reservation does not exist, the option -nrc can be used, forcing an insertion. However, the VR is set to UN then, because the tag then cannot be found in the dictionary. See description above how inserting values into elements with unknown VR are handled. Modifications If you modify a private tags value, dcmodify won't check its VR against the dictionary. So please be careful to enter only values that match the tag's VR. If you wish to change a private tags value and VR, because you just added this tag to your dictionary, you can delete it with dcmodify and re-insert it. Then dcmodify uses your dictionary entry to determine the right VR (also see subsection insertions). Also, see description above how inserting values into elements with unknown VR are handled. Deletions When you use dcmodify to delete a private reservation tag, please note that dcmodify won't touch the private tags that are under this reservation. The user is forced to handle the consistency between reservations and their as- sociated private tags. For the deletion of private non-reservation tags there are no special is- sues. CHANGING UIDS dcmodify will automatically correct 'Media Storage SOP Class UID' and 'Me- dia Storage SOP Instance UID' in the metaheader, if you make changes to the related tags in the dataset ('SOP Class UID' and 'SOP Instance UID') via insert or modify mode options. You can disable this behavior by using the -nmu option. If you generate new UID's with -gst, -gse or -gin, this will only affect the UID you chose to generate. So if you use -gst to generate a new 'Study Instance UID', then 'Series Instance UID' and 'SOP Instance UID' will not be affected! This gives you the possibility to generate each value sepa- rately. Normally, you would also modify the 'underlying' UIDs. As a disad- vantage of this flexibility, the user has to assure, that when creating 'new' DICOM files with new UIDs with dcmodify, other UIDs have to be up- dated by the user as necessary. When choosing the -gin option, the related metaheader tag ('Media Storage SOP Instance UID') is updated automatically. This behavior cannot be dis- abled. When working on multiple input files, dcmodify processes each file in iso- lated fashion, i.e. it will generate UIDs for each single file. For exam- ple, when using the -gst option, dcmodify will insert a different Study In- stance UID into each file instead of generating a single one and writing it to each file that is being processed. CREATING NEW FILES Option --create-file lets dcmodify create a file if it does not already ex- ist on disk. This can be used in order to create files from scratch by per- forming consecutive insertions with options like --insert. This might espe- cially become handy when creating query files for tools like findscu or movescu. In case no specific output transfer syntax is defined, dcmodify chooses Little Endian Explicit Uncompressed for output. Files that are newly created are always written as DICOM file format, i.e. option --write- dataset is not permitted together with --create. This way, at least the metaheader is written and no file with zero byte length is created in a case where no insertions are performed in the dcmodify call. ELEMENT VALUES FROM FILE In order to read the element value from a file instead of specifying it on the command line, option -mf and -if can be used. Please note that for OW elements, the data is expected to be little endian ordered and will be swapped if necessary. The file size should always be an even number of bytes, i.e. no automatic padding is performed. WILDCARDS dcmodify also permits the usage of a wildcard character '*' for item num- bers in path expressions, e.g. 'ContentSequence[*].CodeValue' selects all 'Code Value' attributes in all items of the ContentSequence. Using a wild- card is possible for all basic operations, i.e. modifying -m, inserting -i and -e options which makes it, together with the automatic creation of in- termediate path nodes a powerful tool for construction and processing com- plex datasets. The options -ma and -ea for modifying or deleting all occurrences of a DI- COM element based on its tag do not accept any wildcards but only work on single elements (i.e. a single dictionary name or tag key). EXAMPLES -i --insert: dcmodify -i "(0010,0010)=A Name" file.dcm Inserts the PatientName tag into 'file.dcm' at 1st level. If tag already exists, -i will overwrite it! If you want to insert an element with value multiplicity > 1 (e.g. 4) you can do this with: dcmodify -i "(0018,1310)=1\2\3\4" dcmodify -i "(0008,1111)[0].PatientName=Another Name" *.dcm Inserts PatientName tag into the first item of sequence (0008,1111). Note that the use of wildcards for files is possible. You can specify longer tag paths, too (e.g. "(0008,1111)[0].(0008,1111)[1].(0010,0010)=A Third One"). If any part of the path, e.g. the sequence or the item "0" does not exist, it is automatically inserted by dcmodify. dcmodify -i "(0008,1111)[*].PatientName=Another Name" *.dcm Inserts PatientName tag into _every_ item of sequence (0008,1111). Note that the use of wildcards for files is possible. You can specify longer tag paths, too (e.g. "(0008,1111)[*].(0008,1111)[*].(0010,0010)=A Third One"). -if --insert-from-file: dcmodify -if "PixelData=pixel.raw" file.dcm Inserts the content of file 'pixel.raw' into the PixelData element of 'file.dcm'. The contents of the file will be read as is. OW data is expected to be little endian ordered and will be swapped if necessary. No checks will be made to ensure that the amount of data is reasonable in terms of other attributes such as Rows or Columns. -m --modify: dcmodify -m "(0010,0010)=A Name" file.dcm Changes tag (0010,0010) on 1st level to "A Name". This option also permits longer tag paths as demonstrated above for -i. If the leaf element or any intermediate part of the path does not exist, it is not inserted as it would be if using the '-i' option. dcmodify -m "(0010,0010)=A Name" -imt file.dcm Changes tag (0010,0010) on 1st level to "A Name". Due to the given option '-imt', success is returned instead of "tag not found", if the element/item (or any intermediate node in a longer path) does not exist. Note that for the '-m' option the last node in the path must be a leaf element, i.e. not a sequence or an item. -mf --modify-from-file: dcmodify -mf "PixelData=pixel.raw" file.dcm Does the same as -if in case there was already a PixelData element in 'file.dcm'. Otherwise nothing is changed. -ma --modify-all: dcmodify -ma "(0010,0010)=New Name" file.dcm Does the same as -m but works on all matching tags found in 'file.dcm'. Therefore, it searches the whole dataset including sequences for tag (0010,0010) and changes them to "New Name" -e --erase: dcmodify -e "(0010,0010)" *.dcm Erases tag (0010,0010) in all *.dcm files at 1st level. This option also allows longer tag paths as demonstrated above for -i. dcmodify -e "(0010,0010)" -imt *.dcm Erases tag (0010,0010) in all *.dcm files at 1st level. Due to the given option '-imt', success is returned instead of "tag not found", if the element/item (or any intermediate node in a longer path) does not exist. -ea --erase-all: dcmodify -ea "(0010,0010)" *.dcm Same as -e, but also searches in sequences and items. -ep --erase-private: dcmodify -ep *.dcm Deletes all private tags (i.e. tags having an odd group number) from all files matching *.dcm in the current directory. -gst --gen-stud-uid: dcmodify -gst file.dcm This generates a new value for the StudyInstanceUID (0020,000d). Other UIDs are not modified! -gse --gen-ser-uid: dcmodify -gse file.dcm This generates a new value for the SeriesInstanceUID (0020,000e). Other UIDs are not modified! -gin --gen-inst-uid: dcmodify -gin file.dcm This command generates a new value for the SOPInstanceUID (0008,0018). The corresponding MediaStorageSOPInstanceUID (0002,0003) is adjusted to the new value automatically. Please note that it's not possible to avoid this metaheader update via the -nmu option. -nmu --no-meta-uid: dcmodify -m "SOPInstanceUID=[UID]" -nmu *.dcm This will modify the SOPInstanceUID to the given [UID], but -nmu avoids, that dcmodify adjusts the MediaStorageSOPInstanceUID in the metaheader, too. ERROR HANDLING dcmodify tries executing each modify operation given on command line: If one returns an error, the others are being performed anyway. However in case of any error, the modified file is not saved, unless the --ignore-er- rors option is specified. If that option is selected, dcmodify also contin- ues modifying further files specified on command line; otherwise dcmodify exits after the first file that had modification errors. If the --ignore-missing-tags option is enabled, any modify or erase opera- tions (i.e. not --insert) that fails because of a non-existing tag is treated as being successful. That does make sense if someone wants to be sure that specific tags are not present in the file or that - if they exist - that they are set to a specific value. LOGGING The level of logging output of the various command line tools and underly- ing libraries can be specified by the user. By default, only errors and warnings are written to the standard error stream. Using option --verbose also informational messages like processing details are reported. Option --debug can be used to get more details on the internal activity, e.g. for debugging purposes. Other logging levels can be selected using option --log-level. In --quiet mode only fatal errors are reported. In such very severe error events, the application will usually terminate. For more de- tails on the different logging levels, see documentation of module 'oflog'. In case the logging output should be written to file (optionally with log- file rotation), to syslog (Unix) or the event log (Windows) option --log- config can be used. This configuration file also allows for directing only certain messages to a particular output stream and for filtering certain messages based on the module or application where they are generated. An example configuration file is provided in <etcdir>/logger.cfg. COMMAND LINE All command line tools use the following notation for parameters: square brackets enclose optional values (0-1), three trailing dots indicate that multiple values are allowed (1-n), a combination of both means 0 to n val- ues. Command line options are distinguished from parameters by a leading '+' or '-' sign, respectively. Usually, order and position of command line options are arbitrary (i.e. they can appear anywhere). However, if options are mu- tually exclusive the rightmost appearance is used. This behavior conforms to the standard evaluation rules of common Unix shells. In addition, one or more command files can be specified using an '@' sign as a prefix to the filename (e.g. @command.txt). Such a command argument is replaced by the content of the corresponding text file (multiple white- spaces are treated as a single separator unless they appear between two quotation marks) prior to any further evaluation. Please note that a com- mand file cannot contain another command file. This simple but effective approach allows one to summarize common combinations of options/parameters and avoids longish and confusing command lines (an example is provided in file <datadir>/dumppat.txt). ENVIRONMENT The dcmodify utility will attempt to load DICOM data dictionaries specified in the DCMDICTPATH environment variable. By default, i.e. if the DCMDICT- PATH environment variable is not set, the file <datadir>/dicom.dic will be loaded unless the dictionary is built into the application (default for Windows). The default behavior should be preferred and the DCMDICTPATH environment variable only used when alternative data dictionaries are required. The DCMDICTPATH environment variable has the same format as the Unix shell PATH variable in that a colon (':') separates entries. On Windows systems, a semicolon (';') is used as a separator. The data dictionary code will at- tempt to load each file specified in the DCMDICTPATH environment variable. It is an error if no data dictionary can be loaded. COPYRIGHT Copyright (C) 2003-2025 by OFFIS e.V., Escherweg 2, 26121 Oldenburg, Ger- many. Version 3.7.0 Mon Dec 15 2025 dcmodify(1)
NAME | SYNOPSIS | DESCRIPTION | PARAMETERS | OPTIONS | PRIVATE TAGS | CHANGING UIDS | CREATING NEW FILES | ELEMENT VALUES FROM FILE | WILDCARDS | EXAMPLES | ERROR HANDLING | LOGGING | COMMAND LINE | ENVIRONMENT | COPYRIGHT
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