Digital imaging--what is it, how does it work, and what should you buy (Proceedings)

Overview of Imaging: what you need to know today to better serve your clients tomorrow.

Image perception

·         You tend to see what you have seen before.

·         The larger your data base, the greater your list of differentials.

·         The greater your experience, the more realistic is your most probable diagnosis.

Radiographic definition

If the radiographic image is of diagnostic quality, you are able to perceive objects/structures because of their atomic composition and state of matter.

The radiographic jargons used to define the whiteness or darkness (black) of an object/structure is called opacity and lucency.  The opacity of an object is determined by its composition.  The opacity of an object is a relative term as it is influenced by the technical factors used to obtain a radiograph and what is surrounding the object of interest.

                                Opacity                                   Color                                      Jargon

                                gas                                           black                                        radiolucent, least opaque

                                fat                                            light gray

                                soft tissue                                gray to white

                                bone                                        white                                       radiopaque, most opaque

 Straight interpretation

·         Take as many radiographs as required to answer the questions you need to answer or to satisfy yourself the lesion is not definable to the degree you desire.

·         View the radiographs in a consistent fashion; you can follow the international conventions or have your own convention but be consistent!

·         During conventional radiographic studies, equipment and patient motion should be kept to a minimum.  A wobbly tube head, a moving table or cassette, patient torso motion or excessive respiratory motion will all result in a loss of image detail.

·         The most accurate anatomic information is usually obtained when the x-ray beam is centered on the area of interest; however, oblique imaging can be used to separate structures and lesions.

·         Proper radiographic exposure technique is  required to perceive a lesion.  The smaller the lesion, the better the technique required to define the lesion. Digital imagining has many of the same demands as analog imaging; however, the film/screen factor has been replaced with pixels, fill factor, electronic mottling etc.

·         Overhead lights should be off, the room should be darkened .

·         Viewing the image should be done with as much or more care than was used to obtain the images.  You should not be harassed while interpreting the study.  The equipment used to view the study should be the best available or the best you can afford.

Imaging methods

Radiology, ultrasound, computed tomography (CT), magnetic resonance imaging (MRI) and nuclear medicine are the diagnostic modalities currently being used routinely in veterinary medicine.

Radiology

Historically, the radiographic study is the oldest of these diagnostic methods to be used in almost every veterinary hospital.  The basic principle upon which this imaging method depends is differential absorption/penetration of the x-ray beam.  The x-ray beam is produced in an x-ray tube. The x-ray beam exits from the tube where it is collimated and enters the patient in the area of interest.  The x-ray beam either penetrates or is absorbed and scattered by the patient's tissues. 

The portion of the beam that penetrates the patient passes into a cassette that contains screens.  The x-rays energize crystals in the screens. The screens produce light proportional to the amount of x-ray energy that energized them.  The light generated by the screens exposes radiographic film.  The film is processed/developed to give us the image we evaluate.

We have the option of choosing the amount of radiation and the energy of the radiation produced by selecting mA, time and kVp settings.  We can determine the degree to which the beam is collimated allowing us to concentrate on a specific structure or to visualize an entire region.  We may place the patient directly on top of the cassette, or we may interpose a grid that contains lead strips between the patient and the cassette to remove some of the scatter radiation.

We may elect not to use a screen but to have the x-rays expose the film directly.  Finally, we may choose the type of screen and film we use which will influence the amount of radiation required to obtain an image and the quality/detail of that image.

The major advantages of radiology are: (1) it is quick, (2) it is relatively easy to do, (3) it is relatively inexpensive and (4) it can give us considerable imaging information if used properly. The differential absorption of the x-ray beam allows us to easily determine the difference amongst bone (white), soft tissue (whitish), fat (gray) and gas (black).  The radiographic image allows us to appreciate the size, shape, location and opacity of many structures especially when structures of different densities are adjacent to each other.

Digital imaging: what is it, how does it work, what should you buy?

·         What I have learned:

·         If you take excellent quality radiographs now, you may or may not like digital.

·         If you take good quality radiographs now, you will like digital.

·         If you take poor quality radiographs now, you will love digital.

·         If all goes “right,” you will love digital.

·         If all goes not so right, you will hate digital.

·         You will either need to be reasonably computer knowledgeable, or you will spend the rest of your life relying on your support staff to do everything!

·         It helps to have a local computer geek.

·         It will take longer to review a series of radiographs.

·         You better have a backup system to store your images.

·         You will take more radiographs-often a lot more!

·         You need to be aware of radiation safety.

·         You will invest a reasonable amount to a large amount of money and you must figure a payback within three years (may be five years).

·         A high speed internet connection is a good thing to have.

If you go digital, you will need

·         Radiographic unit

·         Safety garb

·         Proper patient positioning

·         Computer work station

·         Electronic storage

·         Photographic printer

·         Digital Processor and Cassette-CR

What you will no longer need

·         Wet chemical processor

·         Conventional cassette/screen system

·         Darkroom               

·         Radiographic viewers

Electronic imaging-digital imaging

Cr-computed radiography

·         Cassette (cassettes)

·         Processor

·         Computer

·         Monitor

·         Software

Dr-digital radiography-flat panel

·         Direct to Digital Receptor

·         Computer

·         Monitor

·         Software

CCD

·         Direct to Digital Receptor

·         Computer

·         Monitor

·         Software

DICOM

The Digital Imaging and Communications in Medicine (DICOM) standard for distributing and viewing any kind of medical image regardless of the origin. http://medical.nema.org/

JPEG

JPEG (Joint Photographic Experts Group). The JPEG compression format was standardized by ISO in August 1990, and commercial applications using it began to show up in 1991. The widely used IJG implementation was first publicly released in October 1991 and has been considerably developed since that time. JPEG images are widely used on the Web. The amount of compression can be adjusted to achieve the desired trade-off between file size and visual quality.

Issues and considerations

·         Dicom vs. Other formats

·         Digital radiography artifacts

·         Image display

·         Acquisition hardware for digital imaging

·         Picture archiving and communication systems (pacs)

·         Digital image storage

·         Teleradiology

Search the web-what they all say!

·         We are a highly innovative company which designs and manufactures high quality medical radiographic systems for hospitals and...

·         The leader….

·         Over!!!! units sold….

What none of them say!

·         The first stuff  we sold was junk…

·         We have gone out of business because we could not do what we promised!

 Final comments

·         The good interpreters look in the area of the radiograph where they expect the lesion to be; the great interpreters look at the entire radiograph.

·         Look at the radiograph when you are not rushed, harassed, or tired.

·         Avoid constant interruptions when reviewing the radiograph.

·         Try to review the radiographs before the client calls or comes back to discuss the case with you.

·         When reviewing the radiographs, do the following:

o    List your radiographic findings

o    List your differentials/diagnosis

o    State your comments and methods for further evaluation

·         When buying anything-ask questions, make sure they deliver what they promise, do not give them the final payment until you are satisfied with the product.  

·         Protect your body from radiation:

http://www.evetdiagnostics.com/(S(1s2tbbm03mduzo55ddoej132))/HowTos.aspx

If you are pregnant or under 18 years of age, do not be in the room

Compare images at www.evetinfo.com