The veterinary digital radiology market is maturing. Several years ago, veterinary vendors were selling equipment that was actually a veiled attempt to lock veterinarians into proprietary telemedicine contracts and software upgrades. By today’s standards the images were also of marginal quality.

Just a few short years ago, the image quality improved and the DICOM standard began to make inroads opening digital communications in the veterinary community and allowing veterinarians to chose “best of breed” systems.

Today veterinarians expect outstanding digital image quality and DICOM connectivity. Unfortunately many digital systems on the market today still fall short of the expectations of veterinarians purchasing these systems.

There is more to a digital radiography system than a pretty picture and DICOM compliance.

An analogy. You are a veterinarian. You have an employee. That employee speaks English and he is a cover model on Men’s Health magazine. However, he is a real pain in the neck. He does not communicate well, and often shows up for work unkempt and unshaven. Every time you turn around, he is continually getting into conflicts with the other staff members. He takes no initiative and must be continually reminded when there is a job for him to do. He also takes longer than the other employees to get simple tasks accomplished and requires a considerable amount of hand holding.

In this analogy, the employee’s photograph on the magazine cover correlates to the great looking digital radiograph you were shown by the vendor. His knowledge of the English language correlates to some degree of DICOM functionality claimed by the vendor, but neither guarantees they will look that good when they show up in your practice or that they can communicate well. Fortunately, when hiring an employee, most veterinarians are proficient at evaluating more than just good looks and knowledge of the English language. Unfortunately, most veterinarians are not sufficiently experienced in evaluating digital systems, and are susceptible to thinking every radiograph will look like the one the vendor is showing, and that the word DICOM thrown out by the vendor will mean the system will function without a great deal of hand holding.

Computer programs, like employees, need to be reliable, and make your practice more efficient by relieving you of responsibility for routine tasks.

The following is a checklist of software and imaging features that we recommend. A system with all of the features is ideal. However, you get what you pay for and it is up to you to decide which features are essential to your situation.

Digital Radiography Image Acquisition

1. Minimum 2.5 LPMM resolution (observed NOT theoretical)
2. Minimum 10 bit greyscale image depth (4000 shades of grey)
3. Get as large of an imaging area as you can afford that will provide good images. In small animal radiology, 14 x 17 is optimal.
4. DICOM C-store SCU to send images to PACS (in other words, you must be able to send DICOM images to a remote server using a DICOM transfer).
5. All acquisition workstations and units should have a DICOM conformance statement.
6. When shopping, evaluate real life images NOT vendor supplied images for image quality. Compare digital images to digital images and do not fall into the trap of comparing digital images to poorly processed film images. Many digital systems were on display at this years SHOWDOWN. Please contact me for more information about the SHOWDOWN.
7. Images should be presented to the technician after acquisition with a minimum of “twiddling” needed to process the image. Test different systems and count the number of mouse clicks it takes from the time you acquire an image until the time it is sent to PACS
8. The image data set produced on the digital modality in terms of both image matrix size and pixel bit depth should be transferred to the image management system. It is recommended that the DICOM standard be used. This is the most desirable mode of digital image acquisition for primary diagnosis¹.
9. At the time of acquisition, the system must be able to capture and save into the acquired image the accession number, patient name, identification number, date and time of examination, name of facility or institution of acquisition, type of examination, patient or anatomic part orientation (i.e., right, left, cranial, caudal etc.), and amount and method of data compression, and display of the total number of images acquired in the study. The ability to record patient date of birth, sex, and a brief patient history is desirable¹
10. Data compression may be performed to facilitate transmission and storage. Several methods, including both reversible and irreversible techniques, may be used under the direction of a qualified veterinarian, with no reduction in clinical diagnostic image quality. The types and ratios of compression used for different imaging studies transmitted and stored by the system should be selected and periodically reviewed by the responsible veterinarian to ensure appropriate clinical image quality¹

1. Digital imaging data management systems should provide storage capacity capable of complying with all facility, state, and federal regulations regarding medical record retention¹
2. The system must support the DICOM Query/retrieve service class to make the images available to other DICOM conformant applications.
   1. The DICOM images retrieved must be consistent from one retrieve to another – it is NOT acceptable for the study, series or instance UIDs to differ from one retrieve to another
   2. The image format that the database uses to store the image internally may vary, however, images stored as DICOM “part 10” files are useful in the event of disaster recovery or loss of vendor support
   3. This database need not be a full PACS. However, if no PACS is supplied this functionality should be provided by the acquisition station.
3. Redundant storage (RAID) or off site backup is recommended
4. Each facility should have policies and procedures for archiving and storage of digital image data equivalent to the policies that currently exist for the protection of hard-copy storage media to preserve imaging records.
5. A study should be defined within PACS and a study must have a unique study identifier identifying that study in the database
6. All storage and PACS systems should have a DICOM conformance statement
7. There should be functionality to autoroute images to a remote DICOM server. This is essential for offsite backup and large volume teleradiology
8. Digital imaging data management systems should provide storage capacity capable of complying with all facility, state, and federal regulations regarding medical record retention. Images stored at either a transmitting or receiving site should meet the jurisdictional requirements of the acquisition and transmitting site. Images interpreted off-site need not be stored at the receiving facility provided they are stored at the transmitting site. However, if the images are retained at the receiving site, the retention period of that jurisdiction must be met as well. The policy on record retention must be in writing¹
9. Once the study is sent to storage/PACS, the digital storage or imaging system should take reasonable safeguards to ensure that this information cannot be easily altered
10. Ideally an audit trail will be left if patient demographic information is changed in an image.

1. DICOM images are recommended as the primary means of teleradiology in veterinary medicine.
   1. E-mail, third party website downloads (i.e. sending the reader to look at a web based interface provided by a third party), or other methods of sending images are an inappropriate and inefficient for teleradiology
   2. Systems that do not provide means of “streaming” images and allowing the radiologists to login to the database should have DICOM c-store SCU functionality to be able to send to a remote DICOM server. In other words, your system must be able to send images directly to a remote DICOM server for interpretation
   3. The sending process should be performed as a background process
2. The sending process should take measures to ensure that the images reach their destination. The transmission system shall have adequate error-checking capability¹
3. In all cases, for official interpretation, the digital data received at the receiving end of any transmission must have no loss of clinically significant information
4. When images are sent for teleradiology the entire study must be included and transmitted
   1. The system should prevent selection of partial studies for transmission
5. Data compression may be performed to facilitate transmission and storage. Several methods, including both reversible and irreversible techniques, may be used under the direction of a qualified physician, with no reduction in clinical diagnostic image quality. The types and ratios of compression used for different imaging studies transmitted and stored by the system should be selected and periodically reviewed by the responsible physician to ensure appropriate clinical image quality¹.

1. Selection of image sequence
2. Accurately associating the patient and study demographic characterizations with the images of the study performed
3. Window and level adjustment
4. Pan functions, the ability to zoom up to 1:1 screen pixel to image pixel sizing, and zoom (magnification) functions capable of meeting guidelines for display of all acquired data
5. Rotating or flipping the images, provided labeling of patient orientation is preserved
6. Calculating and displaying accurate linear measurements and pixel value determinations in values appropriate for the modality (e.g., Hounsfield units for CT images), if those data are available
7. Displaying prior application of irreversible compression ratio, processing, or cropping
8. Displaying the total number of images acquired in the study
9. Care should be taken to control the lighting in the reading room to eliminate reflections in the monitor and to lower the ambient lighting level as much as is feasible
10. when the display is not used for official interpretation it need not meet the criteria described above
11. Idealluy, the display should be calibrated to DICOM Part 14 guidelines

Image distribution

1. The digital radiography system must have a means of burning a CD or DVD with the patient images for distribution
2. DICOM images should be included on the removable media as the default image type
3. An auto-opening viewer should be included with each CD.
4. The viewer should not require software to be loaded onto a computer to view the images. In other words, the software must run off of the CD.
5. The CD/DVD shall conform one or more of the DICOM exchangeable media profiles, including the requirement that DICOM image file names shall not exceed 8 characters, with no extension, and inclusion of a DICOMDIR index file

References:

1. ACR Technical Standard for Digital Image Data Management

2. PACS users wise to maintain DICOM object integrity