What is DICOM

A crash course in dealing with DICOM imaging data

As technology finds its way into every aspect of medicine, great advances have been made in the field of radiology. Radiology once depended on simple two-dimensional images that had to be manually developed and fixed before viewing. Now almost all forms of medical imaging have been digitized and the spectrum of radiology includes not only digital x-rays, but also CT scans, MRI, ultrasound and nuclear imaging. In order to maintain both standards and uniformity across the various types of medical imaging modalities, the concept of DICOM was introduced.

As a medical student or even a full-fledged radiologist, the prospect of dealing with so much technology can seem quite daunting. This article simply explains how to handle DICOM files and achieve their full potential.


What is DICOM in Medical Imaging?

DICOM stands for digital imaging and communication in medicine. It is an internationally recognized standard format for viewing, storing, retrieving, and sharing medical images. DICOM complies with established protocols to maintain the accuracy of the information conveyed by medical images.



Why do I need to know about DICOM files?

As a student or practicing radiologist, any medical images you see will likely be in DICOM format. DICOM medical imaging data cannot be opened by regular imaging software present on operating systems such as Windows or Mac OS. A special medical DICOM viewer must be installed to retrieve, display and access DICOM image files. Therefore, it is important to know how to use this format, which applications are relevant, and how to access the information and features it contains.


What does a DICOM Medical Image file contain?

Each DICOM medical image consists of two parts - a header and the actual image itself. The header consists of data that describes the image, the most important of which is patient data. This includes the patient's demographic information such as name, age, gender, and date of birth. The header can also give information about image properties such as acquisition parameters, pixel intensity, matrix size and dimensions of the image. When a file explorer is opened to view DICOM medical imaging data, the header can provide patient and image information. The header is usually encoded onto the picture so that the patient to whom the picture belongs can be easily identified. However, the header can sometimes be lost when the DICOM file is exported to other formats such as JPEG. Sometimes you may want to intentionally lose the header data, usually for the purpose of anonymization in research cases. This can only be done with specific software functions.


Where can I access DICOM files?

It depends on the purpose for which you need the files. If you're a patient and you've done scans, you will likely receive a CD or DVD with pictures on it. If you are a medical student and want to view DICOM images for study and study, you can download such images from online resources. If you are a radiologist and you need to access files to interpret them and identify diagnoses, you need to use a PACS server.

  • CDs / DVDs: With medical imaging, the patient usually receives a copy of the image files on CD or DVD. Such CDs usually include a DICOM Medical Imaging Viewer that can help you see the images. Some CDs may not have an actual application, but they may provide you with an Internet link to download a suitable DICOM medical viewer.

  • Online resources: If you are a college student looking for medical images to learn from, there are several resources online that can help you. Some good ones are the Dicom library, the Osirix Image library, and the Cancer Imaging Archives.

  • PACS server: PACS stands for Picture Archiving and Communications System. This is basically a database that stores all of the medical images. A PACS server must have adequate disk space because DICOM files, which are high quality, tend to take up a lot of space. Each hospital usually has its own PACS server. Every medical image that is taken within a hospital is automatically saved on this PACS server.


A DICOM workstation must be available so that a radiologist can access DICOM medical image files for diagnostic and interpretation purposes. This is usually a software application that can be fully integrated with the PACS server: the application must be able to access DICOM images from the PACS server and retrieve them from the PACS server, as well as viewing and editing and then subsequent To enable saving of edited images again on the PACS server.


How can I view a DICOM file?

Special software is required to display DICOM medical images. There are basically two types of software for displaying DICOM imaging data: proprietary software and third-party software. Proprietary software comes with the medical imaging hardware and is usually made by the same manufacturer. Once the CT or MRI scan has been captured by the machine, the images can be viewed at the same workstation via the DICOM imaging viewer. Proprietary software enables users to dynamically display sequential images and also enables those images to be reconstructed. A major disadvantage is that these image files can only be viewed in the same location as the hardware. The images can only be transferred to portable storage devices or other computers on the network by compressing the images (see below). However, once images have been exported, the ability to view and edit the original image is usually lost.

Third party software for DICOM image viewing is becoming more and more common. These are stand-alone applications that can open DICOM files from any source - the Internet, a CD or DVD, or a PACS server. The market today is awash with DICOM viewing applications, with both free and paid options. Each DICOM Medical Image Viewer has its own functions and you can choose from among them according to your specific requirements.

What can I do with a DICOM file in addition to simply displaying the image?

Today's DICOM Medical Imaging viewers can do more than just view DICOM images. Some applications are sophisticated enough to improve image quality and generate additional data from the captured images that can help with diagnosis. Some of the functions that you can perform in addition to simply viewing the image include

  • To improve the image quality: You can increase or decrease the brightness of the picture. Changing the contrast will help you distinguish between radio-dense and radio-reducing areas of an image. You can also enlarge the area of ​​interest. A special method of improving the image quality in the area of ​​interest involves projecting with maximum and minimum intensity. This helps isolate areas that have absorbed maximum or minimum radiation and differentiate them from the surrounding areas.

  • Reconstruction of images: The initial DICOM data set contains a series of two-dimensional images taken in all three planes - axial, coronal and sagittal. These images can be reconstructed to give a three-dimensional view of the anatomical area. This is known as 3D rendering. Another technique, called Multiplanar Reconstruction (MPR), involves making fresh slices from the 3D reconstructed images. This enables the radiologist to view different anatomical levels or angulations from the originally acquired discs.

  • Perform measurements: Some DICOM medical viewers allow you to take linear or even volumetric measurements of anatomical structures. This can be useful in planning treatment and assessing the effectiveness of the treatment. For example, in the event of a traumatic injury to the bone tract, a volumetric analysis and a comparison of the injured orbit with the unaffected person can help in planning the reconstruction of the orbital tract.

  • Comparison and combination of medical images: Medical applications of DICOM allow the radiologist to compare two different images at the same time. This is useful in assessing disease progression over time or the effectiveness of treatment. Two different medical imaging modalities can also be combined with certain DICOM applications. By combining PET and CT images, it can be ensured, for example, that areas with high metabolic activity (with PET) are assigned to certain anatomical locations (by means of a CT scan). This enables the doctor to extract the benefits of both types of imaging modalities at the same time.


How can I share and export DICOM files?

A single patient's DICOM medical file is made up of multiple images, all of which are high resolution. Therefore, the file size can be quite large (e.g. a single CT scan can run up to 35MB). Therefore, these files must be compressed before they can be shared and transferred.

There are two ways that files can be compressed: lossless and lossy. At lossless compressioneven though the file itself is compressed, there is no loss of information. Therefore, the original file can be restored at any time. However, this type of compression requires a lot of processing and so lossless files are slow to open and slow to save. Significant compression cannot be achieved with this method. On the other hand, allows lossy compression a reduction in file size by removing actual data. Usually only redundant data is removed. However, sometimes, when excessive compression is performed, the image quality can be degraded. This method allows files to be compressed into sizes much smaller than the original file.

The compressed file can be exported in various formats. The most common image formats include JPEG, TIFF, PNG, and GIF.

  • JPEG (Joint Photographic Experts Group): The JPEG format supports both lossless and lossy compression. Standard JPEG uses lossy compression. The operator can specify how much compression to apply and thus control how much data is lost. Another version, JPEG 2000, supports lossless compression. This application allows users to identify certain areas of the image as "regions of interest". Only these areas are compressed without loss, while other parts of the image are lossy. JPEG is useful for easily sharing pictures between computers. It can be used for uploading images to websites and for standard PowerPoint presentations. On the downside, the quality of the images may not be good enough for paper publishing.

  • TIFF (Tagged Image File Format): The TIFF format can support both lossy and lossless compression. TIFF provides higher quality images and is therefore the preferred format for several magazines for publication. However, the file size is larger and may not be suitable for use in presentations or on the web.

  • PNG (Portable Network Graphics Format): This supports lossless type of compression. PNG can be used to control image functions such as brightness and transparency. One advantage of PNG is that the images can be provided with metadata, similar to the header of a DICOM file. This versatile format is suitable for publications, presentations and the Internet.

  • GIF (Graphics Interchange format): This was one of the earliest image formats to be introduced and is not used much today. It has limited features and the compression is inefficient. It supports lossless type of compression and is widely used for websites.


Now that I've learned about DICOM software, what's the next step?

The best way to use your DICOM medical imaging knowledge is through hands-on hands-on. The first step is to download a DICOM application that suits your needs and start using it. There are several free applications that you can use to gain experience. The most popular are PostDicom, Horos, Radiant, Miele LXIV and Navegatium.

PostDicom is a one-size-fits-all solution that is just right for beginners. It is compatible with the most popular operating systems including Windows, Mac OS, Linux, and Android platforms. It's fast and has an easy-to-use interface that is great for people just learning the basics of handling DICOM images. At the same time, radiologists with advanced functions such as MPR, MP, MINIP and volume reproduction can use the application for improved diagnostic functions. PostDicom comes with a unique cloud-based PACS that allows you to save DICOM files online and access them from anywhere, anytime. Best of all, this DICOM medical imaging software is free to download! With a single accessible account, you can store up to 50 GB of data on your free cloud-based PACS. If you think you need more storage space or more user accounts, options to upgrade are available. Try PostDicom today!


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