by Leif Kullman
What is a Digital Image?
Today every dentist is aware of that our ordinary radiographic films and the darkrooms will disappear. The digital image will soon take over, thanks to the computer development. What is an digital image and which advantages does it have? Here is a try to a simple (well almost) explanation: A digital image consists of discrete picture elements, arranged in rows and columns in the memory of a computer. Each picture element can be defined by its position in the mentioned matrices system and by its grey scale level. Often 512 rows and 512 columns are used in radiographic imaging. The total sum of elements will then be 262144 (512 x 512) and this number will decide thegeometric resolution of the image ( the more the "better" image).
A computer is a binary computing machine. All information are represented by either a zero or a one, called a bit. The grey scale level in a picture element, are decided from the formula 2n where n is the number of bits. If we have a 3-bits image the number of grey scales will be eight for a pixel ( 000, 001, 010, 011, 100, 101, 110, 111).
However usually an 8-bits image is used where 28=256 grey scale levels are possible. The value 0 (zero) is usually black and the value 255 (=11111111) is white. The number of grey scale levels in a pixel will define the contrast (resolution) in the image.
Some of the advantages of digital images are:
The darkrooms with all chemical solutions and possibilities to
errors during film processing will disappear.
The radiation doses from diagnostic radiography to the
population will diminish since digital systems require less
radiation than film. No retakes of radiographs.
A faster handling and possibility to communicate with the
images.
A better diagnostic accuracy of different bone and tooth
changes.
Next month:
Increased possibilities for radiographic diagnosing in the future with Internet.
Leif Kullman
