Comunicología, Comunicometodología y Cibercultura

To compare the radiation dosage necessary to obtain a high quality image from (both a CCD or an excitable phosphor) DRS and from an X-ray film, may be consi- dered a disputable approach as it compares quantities which are physically inconsistent. In actual fact, while a certain X-ray dosage causes a specific blackening of the film, that is (given a correct chemical process) an opti- cal effect, the same dosage causes an electrical signal in an electronic sensor, with a level which can be ampli- fied and altered in the next stages of electronic proces- sing, before obtaining a visible image.

The radiation dosage required by DRS is, anyway, surely lower than the one necessary in traditional radiology, even taking into account that the radiation dosage must not be reduced too much in order to have a good signal- to-noise ratio (that is a good image quality).30

In general one can state that the required exposure is at least six times lower compared with a D-type film and three times lower compared with an E-type film. One can expect the same correlation to exist between the absorbed dosages (in gray) (Tab. VI).

Regardless of the type of image acquisition device

Table VI

Exposure times in seconds recommended for the Oralix DC (Gendex) intra-oral device with a constant 60 and 70 kV potential

DRS Systems Agfa Dentus_{M4 Films} Kodak Ektaspeed_{E-type Films} Kodak Ultraspeed_{D-type Films} Very Slow speeds

60 kV 70 kV 60 kV 70 kV 60 kV 70 kV 60 kV 70 kV 60 kV 70 kV Incisors 0.100 0.050 0.160 0.080 0.250 0.125 0.400 0.200 0.630 0.320 Canines 0.100 0.063 0.160 0.100 0.250 0.160 0.400 0.250 0.630 0.400 Premolars 0.125 0.080 0.200 0.125 0.320 0.200 0.500 0.320 0.800 0.500 Lower molar 0.160 0.100 0.250 0.160 0.400 0.250 0.630 0.400 1.000 0.630 Upper molars 0.200 0.125 0.320 0.200 0.500 0.320 0.800 0.500 1.250 0.800 Bite Wing 0.160 0.100 0.250 0.160 0.400 0.250 0.630 0.400 1.000 0.630 Occlusal 0.250 0.160 0.400 0.250 0.630 0.400 1.000 0.630 1.600 1.000

Fig. 6.21. Detail of a head with a rectangular collimator

used, one must remember that a further reduction of the supplied dosage will be obtainable, if one uses – for a radiogenous head – a rectangular collimator equipped with a limiting device in proximity of the fo- cal spot (Fig. 6.21). In this way one obtains an effecti- ve suppression of the diffused and extrafocal radiation and, in the last analysis, a better image quality.

a one-two millimeter gap to the sizes of the external protective cover. The first CCD sensors featured a de- finitely larger overall size, - even seven, eight milli- meters – compared with the one of the sensitive area. This size was, anyway, much reduced by comparison with the sensitive area of traditional X-ray plates. For this reason it was not always possible to obtain suffi- cient data with a single projection, particularly in the case of polyradicular or larger teeth. It was often ne- cessary, anyway, to define the area of greater inte- rest with care and to sacrifice the vision of neighbo- ring areas. In addition one must consider that sensors were fairly thick and cumbersome and, often, it was not easy to position them in the area of interest so as to obtain a correctly framed projection without distor- tions. At first centering devices were not even availa- ble, whereas the first ones were cumbersome, not mu- ch functional and difficult to use. In addition, then, to the problem of a difficult initial centering there was also the one of an impossible correct repetition, after some time, of the same frame, an almost – I would say – mandatory requirement in Endodontics.

These important failings have been given the right consideration by research centers, so that today the most advanced DRS feature CCD sensors of different

featuring excitable phosphor sensors, which, with nearly the same size and thickness as traditional ra- diographic plates, can use all the standard centering devices (Figs. 6.24 and 6.25).16,27

C

Fig. 3.23. A. (Rinn) Endodontic centering device for Gendex CCD sensors. B. Front view: (Rinn) Endodontic centering device for Gendex CCD sensors, placed in patient’s mouth during endo- dontic treatment. C. Side view.

B A

132 Endodontics 6 - Visiography Systems 133

FILING

Patients’ X-rays are such an important amount of data – both from the clinical and the forensic medicine point of view – that their filing should be a straightforward, safe and easy-to-check process.22 _{In reality this does} not always happen. It is not infrequent, in actual fact, for X-rays to deteriorate and get lost due to both an incorrectly performed developing and fixing process and unforeseeable accidents (Tab. VII). It is necessary to bear in mind, however, that current legislation does not offer univocal interpretations for what regards the forensic validity of digital images. It would be a good rule, at a close periodical interval, to make copies of

the filed images on no longer modifiable supports af- ter the first recording. The hypothesis would be for the presence of an image, exactly identical on nume- rous chronologically progressive registration supports, to be valid in practice also on its unaltered originali- ty. All this, however, will not be valid, if the image has been tampered with before the initial filing registra- tion: all the next copies, of course, would not equally correspond to reality. This problem, of course, takes on particular importance and it is, then, a subject of study in an attempt to reach an adequate solution. One of the suggested solutions (Gendex) consists of filing inside the image file itself a small “file” – no longer modifiable by the user – which registers and

A B

Fig. 6.25. A. Preoperative radiograph. B. Postoperative radiograph. C. Endodontic centering devices for ordinary X-ray plates can be used with memory pho- sphor type sensor, thanks to their identical size. Their overall size is smaller than the endodontic centering devices for CCD sensors.

C

A B

keeps automatically all the changes and modifications performed on the image after its acquisition. This “fi- le” may easily be consulted through a management

and, if necessary, expanding its memory capacity abo- ve-all as the mass of data will grow progressively. The program which manages the clinical or DRS image filing (Fig. 6.26) must be easy and intuitive to use, featuring easy-to-follow systems for filing and later search. It should be compatible, ready for integration, if required, with the management program of the dental surgery so that clinical, statistical and book- keeping data, traditional X-ray images, clinical or intra-operative images (acquired through a scanner or directly via modem or digital cameras) and

C D

Fig. 6.26. A-D. Radiographic and clinical images may be filed in each patient’s clinical card. An example of the software “The Digital Office” (TDO). Courtesy of Dr. Gary Carr.

A B

– Image digital processing

– Efficient filing and re-calling of images from data- base

– Elimination of dark chamber

– Elimination of plates (purchasing, storage and ma- nipulation problems)

134 Endodontics 6 - Visiography Systems 135

radiovisiographs may be linked and grouped in a single clinical card to facilitate the patient’s overall management.

A particular of no secondary importance which may and should affect the choice not only of the DRS, but also of a computer management program for the den- tal surgery, is the guarantee of reversibility of data. They must be filed in standard formats so as to of- fer access to any other programs. It is necessary to beware of anyone who suggests filing formats or sy- stems outside common standards, even if highly effi- cient. Should one change to other systems, one would risk losing data or having to cope with complex, co- stly and often uncertain operations for the extraction and the translation of the data themselves in order to make them compatible.26

The possibility to make all the security copies from the file, believed to be necessary, protects from any chance of loss or deterioration of data. Moreover a copy or a print can easily be made and handed to either the patient or the colleague who has requested the specialist’s consultation (Fig. 6.27).

Fig. 6.27. Referral report made with “The Digital Office” software (TDO). Courtesy of Dr. Gary Carr.

Fig. 6.28. Also orthopantomographic examinations may be performed through radiovideographic systems.