Introduction

Digital Imaging and Communications in Medicine (DICOM) is a standard for managing informations in medical imaging developed by American College of Radiology (ACR) and National Electrical Manufacturers Association (NEMA). It defines a file format and a communication protocol over network.

DICOM SDL is a software developed libraries for easy and quick development of an application managing DICOM formatted files. DICOM SDL is written in C++ and it allows to make programs that read, modify, write DICOM formatted files without in depth knowledge of DICOM.

DICOM SDL provides an extension module for python and you may build scripts with python.

DICOM SDL can

• read/modify/write DICOM formatted files.
• read/modify/write medical images in DICOM file, if file encodes in raw format, jpeg/jpeg2000 format.

DICOM SDL is especially optimized for reading lots of DICOM formatted files quickly, and would be very useful for scanning and processing huge numbers of DICOM files.

DICOM SDL cannot

• send/receive DICOM over network.
• read files encodes in RLE format and JPEG-LS format

Get codes

You can get sources and binaries from http://code.google.com/p/dicomsdl.

Installing

DICOM SDL needs cmake (www.cmake.org) to compile. DICOM SDL was successfully compiled and ran on following environments

• Microsoft Windows x86/x64 using Microsoft visual studio 2008,
• Linux x64 (CentOS) using gcc,
• MacOS (ppc) using xcode 3.1.2

DICOM SDL is also expected to be compiled successfully at other Linux x86/x64 and intel MacOS.

Getting Started

This short example loads a dicom file and extract some example and image.

#include "dicom.h"
#include <string>
int main()
{
        dicom::dicomfile *df;
        df = dicom::open_dicomfile("img001.dcm");
        if (df) {
                // get some informations dicom file
                std::string studydesc = df->get_dataelement("StudyDescription")->to_string();
                // shorter form
                std::string studytime = (*df)["StudyDate"];
                printf("Study Description = %sn", studydesc.c_str());
                printf("Study Time = %sn", studytime.c_str());
                // get informations of image in dicom file
                int width, height;
                int precision, signedness, ncomponents, bytes_per_pixel;
                int nframes;
                df->get_image_info(&width, &height,
                        &precision, &signedness, &ncomponents, &bytes_per_pixel,
                        &nframes);
                // get pixeldata
                char *pixeldata;
                int pixeldata_length;
                df->get_pixeldata_a(&pixeldata, &pixeldata_length);
                if (pixeldata) {
                        // do something ...
                        free(pixeldata);
                }
                delete df;
        } else {
                printf("Error message: %sn", dicom::get_error_message());
        }
}

Let's see what above codes do line by line.

dicom::dicomfile *df;

A dicom::dicomfile is an implementation of DICOM file object.

df = dicom::open_dicomfile("img001.dcm");

dicom::open_dicomfile(filename) reads, parses the file and returns a DICOM file object.

Note) Returned DICOM file object need to be deleted by user.

// get some informations dicom file
std::string studydesc = df->get_dataelement("StudyDescription")->to_string();
// shorter form
std::string studytime = df["StudyDate"];

A DICOM file consists of several items contain informations about the DICOM file. Each item in a DICOM file called 'data element' and you get a data element using get_dataelement(tagname). Item's value can be retrieved with functions like 'to_string()', 'to_int()', 'to_double_values()', according to the data type of item. You may shorten code in second form.

// get informations of image in dicom file
get_image_info(&width, &height,
        &precision, &signedness, &ncomponents, &bytes_per_pixel,
        &nframes);
// get pixeldata
df->get_pixeldata_a(&pixeldata, &pixeldata_length);

DICOM file object provide functions to extract image in the DICOM file. get_image_info(...) takes informations related to image's geometry, and get_pixeldata_a(...) extract image.

Note) The suffix  _a in the function name  get_pixeldata_a(...) means that function return a pointer that should be  free() by user, provided that the pointer is valid.

printf("Error message: %sn", dicom::get_error_message());

If an error is occured during reading/parsing a DICOM file, open_dicomfile() return NULL and you may get the error message usingdicom::get_error_message(). After calling several functions return NULL on error, dicom::get_error_message() provide informations about the error.

Python example

This is a python program does exact same thing.

import dicom
df = dicom.open_dicomfile('img001.dcm')
if df:
        # get some informations dicom file
        studydesc = df.get_dataelement('StudyDescription').to_string()
        # shorter form
        studytime = df["StudyDate"]
        print "Study Description =", studydesc
        print "Study Time =", studytime
        # get informations of image in dicom file
        ret = df.get_image_info()
        if ret:
                (width, height,
                 precision, signedness, ncomponents, bytes_per_pixel,
                 int nframes) = ret
        # get pixeldata
        pixeldata = df.get_pixeldata()
        if pixeldata:
                pass # do something ...
else:
        print "Error message:", dicom.get_error_message()