A survey of digital radiography practice in four South African teaching hospitals: an illuminative study
1 School of Physics, University of the
Witwatersrand, Johannesburg, South Africa
2 Epidemiology and Biostatistics Unit, School of
Public Health, University of the Witwatersrand, Johannesburg, South Africa
3 Charlotte Maxeke Johannesburg Academic Hospital, Johannesburg, South Africa
Purpose: The purpose of this study was to assess
radiographer familiarity and preferences with digital radiography in four
teaching hospitals and thereafter make recommendations in line with the
migration from screen film to digital radiography.
Materials and Methods: A questionnaire was designed
to collect data from either qualified or student radiographers from four
teaching hospitals. From the four teaching hospitals, there were a total of 205
potential respondents. Among other things, responses regarding experiences and
preferences with digital radiography, quality control procedures, patient dose,
advantages and disadvantages of digital radiography were sought. The
information collected was based on self-reporting by the participants. The
study is exploratory in nature and descriptive statistics were generated from
the collected data using Microsoft Excel 2007 and StatsDirect software.�
Results: Sixty-three out of 205 (31%) radiographers
from all the four radiology centers responded to the circulated questionnaire.
Only 15% (8) of the qualified radiographers had 4 or more years of experience
with digital radiography compared to 68% (36) for the same amount of experience
with screen-film radiography. Sixty-one percent (38) of the participants had
been exposed to digital radiography during their lectures while at university.
A small proportion, 16% (10) of the respondents underwent formal training in
quality control procedures on the digital X-ray units they were using. Slightly
more than half (55%) of the participants felt it was easier for them to retake
an image in digital radiography than in screen film radiography.
Conclusion: The results of this survey showed that
the participants are familiar with digital radiography and have embraced this
relatively new technology as shown by the fact that they can identify both its
advantages and disadvantages as applied to clinical practice. However, there
are minimal quality control procedures specific to digital radiography being
undertaken as such there is need for formal education, continuing education and
manufacturer training with respect to quality control as institutions make the
transition from conventional screen film radiology to digital radiology. � 2010
Biomedical Imaging and Intervention Journal. All rights reserved.
Keywords: Digital radiography, radiography practice, quality
The foundation of diagnostic radiology lies in the discovery
of X-rays by Professor Wilhelm Conrad R�entgen, of the University of Wurzburg,
Germany, in November 1895 . Radiography has evolved over the years from
using screen-film technology to digital imaging, which is sometimes referred to
as filmless radiography. Nowadays, digital X-ray units are ubiquitous in most
radiology departments .
Digital imaging is a term used to describe general
radiography when the radiographic images are in digital form and are capable of
being displayed on a computer monitor . Digital imaging can be realized
through the use of either computed radiography or digital radiography. It has
become technically possible and economically feasible for digital imaging
technologies to challenge screen-film technology for projection radiography
. This has been made possible by the prerequisite technological advances
such as high-luminance and high-resolution display monitors combined with
high-performance computer workstations and a decline in the price of computer
technology. This shift in choice of imaging modality is not only confined to
developed countries but is gradually finding its way to developing countries.
Computed radiography uses an imaging plate coated with
photostimulable phosphors to capture x-rays as they traverse through the
patient. BaFBr:Eu2+ and BaFI:Eu2+ are the commonly used
phosphors . When exposed to radiation, the phosphors absorb and store x-ray
energy in gaps of their altered crystal structure. This trapped energy
comprises a latent image. When stimulated by additional light energy of the
proper wavelength, the trapped energy is released. The amount of light emitted
is directly proportional to the number of X-ray photons absorbed. The resulting
computed radiography image comprises of multiple rows and columns of pixels
representing the X-ray intensities at locations (x;y). Eventually, these raw
pixel values are processed using mathematical algorithms for subsequent
In digital radiography, the digitization of the X-ray
projection image occurs within the image receptor. Detectors in digital
radiography can be in the form of charged coupled devices or flat panel
imagers. Furthermore, flat panel imagers are generally of two types namely,
direct conversion or indirect conversion systems. Direct conversion systems use
an X-ray sensitive photoconductor layer (amorphous selenium, a-Se) and a
thin-film transistor (TFT) charge collector [5, 6, 7]. Radiation absorbed by
the photoconductor is directly converted into charge, which is drawn to the TFT
charge collector where it is stored until readout. On the other hand, indirect
conversion systems use scintillators e.g. cesium iodide (CsI) or gadolinium
oxysulphide (Gd2O2S) layered on top of an array of
light-sensitive photodiodes with TFTs [5, 6, 7]. The scintillator converts
radiation into light that is detected by the photodiode/TFT array. For
anatomical regions with gross density differences such as the chest, thoracic
spine, shoulder, facial bone, cervical spine, thoraco-lumbar spine, femur and
feet, digital radiography has shown superior image quality over screen-film
In this work, the term digital radiography will represent
both computed radiography and digital radiography. Digital radiography has both
advantages and disadvantages when compared to screen-film radiography, as
summarized in Table 1 based on literature [8, 9, 10].
Over the last few years, public hospitals in South Africa have been purchasing digital units for their radiology departments. This is in
line with worldwide trends of migration from screen-film radiography to digital
radiography. Upon adoption of new technology, it is advisable that the
technology undergoes evaluation and critique so that strategies are devised to
optimize its use. Currently, there is no published data on use of digital X-ray
units in South Africa except for one paper on computed radiography in
mammography . The transition from screen-film to digital radiography
technology is not a simple matter, at it involves acquirement of new skills,
change in the workflow process, training and retraining at times . As such,
this present study seeks to elucidate two issues, which are as listed below:
- Assess radiographers� familiarity and preferences with digital
- Make recommendations in line with migration from screen film radiography
to digital radiography to the participating institutions.
Materials and Methods
This was a cross-sectional study in which a questionnaire
was designed to collect data from either qualified or student radiographers from
four teaching university hospitals in South Africa. Only qualified
radiographers or registered student (trainee) radiographers were eligible for
inclusion in the current study. Student radiographers were included in the
study because they would give an insight into the training programs and in some
cases due to staff shortages they work under minimal supervision. From the four
teaching hospitals, there were a total of 205 potential respondents. Due to a
request by one of the participating institutions, the hospitals will not be
identified by name in this study.
The questionnaire used took a multiple format, i.e. it had
closed- and open-ended questions. The information collected was based on
self-reporting by the study participants. The questionnaire captured the
participants� familiarity, preferences, knowledge and workmanship with regards
to digital radiography. The participants in this survey were further asked
questions relating to operation of their digital X-ray units, comparing digital
radiography to screen-film radiography and their preferences when using digital
radiography units. The questionnaire captured the quality control procedures
performed at the different institutions and, furthermore, the participants were
asked to identify the advantages and disadvantages of digital radiography.
A soft copy of the questionnaire was e-mailed to the
radiotherapy medical physicist at the relevant teaching hospital, who made
printouts and hand delivered them to the Assistant Director of Radiography. The
Assistant Director then asked the radiographers to respond to the
questionnaire. Participants were given a maximum of one week to respond to the
questionnaire. Participation in the study was voluntary and no incentives were
offered. Filled questionnaires were given to the medical physicist, who
returned them to the authors.�
The study is exploratory in nature and descriptive
statistics were generated from the data using Microsoft Excel 2007 and
StatsDirect software. Descriptive statistics included summary measures and
frequency tables. Collected data was handled with confidentiality.
This survey was sanctioned by the Assistant Directors of
Radiography in the respective participating institutions.
Sixty-three out of 205 (31%) radiographers from all the
four radiology centers responded to the circulated questionnaire. Among those
who responded, there were 10 student radiographers and 53 qualified
radiographers employed on a full-time basis. Because of the small numbers,
student radiographers participating in the survey from each hospital were
combined with qualified radiographers as shown in Table 2. Possible reasons for
poor response could be lack of incentive, lack of active follow-up and that
radiographers working night shift were not given the questionnaire directly by
the Assistant Director. Hospital D had the greatest response rate among the
participating hospitals. Despite the poor response in some hospitals, the data
collected provided some insights and lessons, and was, nonetheless, useful. As
such, interpretations from this study should be viewed as exploratory and
illuminative. Radiography techniques were not compared between the
In terms of modalities, Hospitals A and D currently use
flat panel based digital radiography units whereas Hospital B uses both
computed radiography and flat panel based digital radiography units while
Hospital C is currently using computed radiography units only. The equipment
manufacturers are varied and included Philips Medical Systems, Siemens Medical,
GE Medical Systems, Toshiba, Agfa, Fuji, Kodak and Konica Minolta. However, the
interest of this present study was not to compare manufacturers.
All the qualified radiographers had post qualification
experience ranging from 1 year to more than 5 years. Post qualification
experience was further stratified by whether such experience was based on using
either screen-film technology or digital radiography technology. Figure 1 shows
the distribution of post qualification experience according to the radiography
modality. The above distribution confirms the fact that digital technology is
still a relatively new technology in South African public hospitals, only 15%
(8) of the qualified radiographers have 4 years or more of experience with
digital radiography compared to 68% (36) for the same amount of experience with
Table 3 provides a summary of key responses from
radiographers based on the questionnaire administered. This has not been broken
down into qualified and student radiographers because of the small number of
Presently radiography training in South Africa involves academic teaching at a university and clinical practice at a
university hospital. Sixty-one percent (38) of the participants had been exposed
to digital radiography during their lectures while at university. A small
proportion, 16% (10) of the respondents underwent formal training in quality
control procedures on the digital X-ray units they were using. The training was
conducted by the relevant manufacturer�s representative. However, none of the
surveyed departments had or were following a particular written protocol on
quality control procedures, although there was a designated radiographer
responsible for quality control. Twenty-three percent of the respondents had
managed to read the manual of the digital X-ray unit they were operating.
Slightly more than half (55%) of the participants felt it was easier for them
to retake an image in digital radiography than in screen film radiography. Fifty-five
percent of the respondents preferred to collimate to the region of interest
instead of cropping the image after acquisition.
In an open-ended section of the questionnaire,
participants were asked what they thought the advantages of digital radiography
were. The responses varied, but some reported advantages were common to most
participants. Table 4 shows the five popular advantages cited by the
respondents. One of the commonly cited advantages of digital radiography is the
increase in patient throughput. In response to the question of how many
patients they could image, a median of 20 patients and 50 patients could be
imaged per eight-hour shift in screen-film radiography and digital radiography
with inter-quartile ranges of (15-45) and (25�108), respectively.
Consistent with the fact that the participants are from
teaching hospitals, the most commonly cited disadvantage of digital radiography
was its �press button� approach. The digital radiography user interface takes
away the fundamental radiography technique training i.e. exposure settings,
which is core to the art of screen-film radiography.
This study was exploratory and illuminative for other
teaching hospitals, however it has shown some very interesting results worthy
of further exploration. The study also presents a potential area of
collaboration with other teaching hospitals in South Africa for further studies
based on lessons from this study. Although this is the case, caution is needed
with the interpretations as the present sample size is relatively small given
the number of radiology centers in South Africa having both conventional screen
film and digital radiography. Further face-to-face interviews rather than
mailed questionnaires would have improved participation. However, it stands to
reason that since these surveyed institutions are teaching hospitals, their
radiography practice culture cascades to a number of other centers.
Among the four institutions surveyed, only Hospital B had
a picture archiving and communication system (PACS) implemented in its
radiology department. Some experts have suggested that in order to reap the
full benefits of digital radiography, one needs to implement PACS . It is,
therefore, recommended and encouraged that institutions should eventually
implement PACS as they migrate from film to filmless radiography if they are to
fully realize the benefits of digital radiography. Studies have shown that
implementation of PACS has led to increased radiographer productivity and
overall efficiency of radiology departments [13-16].
There is a large gap in the number of radiographers with
at least four years of experience with digital radiography in comparison to
screen-film radiography. This could be explained by the fact that most
radiographers were only exposed to digital radiography after qualification.
This becomes a challenge since in most cases it is the more qualified
radiographers who are tasked with training students and supervising
newly-qualified radiographers. Thus, it becomes imperative for them to be
subjected to formal training in this modality.
Quality control procedures and quality assurance are
equally important in digital radiography as they are in conventional
screen-film radiography. However, it must be appreciated that the workflow
process and operational nature of digital radiography directly affects
traditional quality assurance practice . For example, how does a radiology
department implement an accurate film reject analysis in digital radiography?
In South Africa, performing quality control procedures on X-ray emitting
devices is enacted in law, thus it is mandatory to do such tests . The
Directorate: Radiation Control, which is the authority responsible for
governing the use of radiation emitting substances in South Africa, has a
document entitled �Requirements for license holders with respect to quality
control tests for diagnostic X-ray imaging systems� which lists the acceptance
tests and quality control procedures . It would be better if the document
described how to perform these tests. It is recommended that quality control
procedures required for digital radiography be included in radiography
undergraduate and postgraduate programs. To further improve service delivery,
radiology departments should implement formal in-house quality control training
to members of staff.
Radiographers should be encouraged to read the operator�s
manual of the X-ray units they are using. Reading the manual would empower the
operator to realize the most out of the unit, particularly post processing
functionality. Since the majority of the participants (84%) alluded to the fact
that they never had formal quality control training of the units they are
using, it is advisable that they at least read through the manuals available to
All the hospitals who participated in this study did not
have a full-time medical physicist in their radiology departments. This is
owing to a nationwide shortage of medical physicists in South Africa, and as a result of this critical shortage, most institutions have medical
physicists working in their radiotherapy department full-time and service to
diagnostic radiology departments is limited to a consultative basis.
Furthermore, the regulations governing licensing and operation of radiology
departments do not stipulate the minimum medical physics staffing levels
consistent with the type of equipment. The advent of these new technologies
should encourage participation of medical physicists who would be responsible
for performing acceptance testing, patient dose measurements, objective image
quality assessments, setting up of quality control programs, annual quality
assessment of all the X-ray units in their departments and quality control
review programs [2, 9, 10].
In dealing with radiation dose issues, it should be
appreciated that digital radiography has a wider dynamic range than screen-film
systems and overexposures or underexposures can yield quality images, as during
post processing adjustments can be made . In digital radiography, a higher
patient dose would usually translate into an improvement in image quality as
the images have less noise. In comparison to screen-film technology, digital
radiography systems do not give an immediate feedback to radiographers
concerning the radiation dose and as a result, there is a potential risk for
dose creep [6, 8, 20]. Although digital radiography has the potential to
achieve dose reduction in a number of examinations, patient dose increments in
the range of 40�103% have been reported in the process of migrating from
screen-film to digital radiography . Thus, the unnecessary pursuit of
beautiful images would violate the �as low as reasonably achievable� (ALARA)
principle. There is also a risk that if the X-ray generator automatic exposure
control (AEC) develops a fault or the output calibration drifts, the dose
increase or decrease can go unnoticed because of the wide exposure dynamic
range of digital systems. In addition, the wide exposure dynamic range means
that there is significant potential for the initial set-up of the system to be
non-optimized, which further motivates for having medical physicists staffing
Digital radiography has post processing functions, for
example, images can be cropped to show only the region of interest. It is bad
radiography practice to rely on cropping images instead of collimating the beam
as this leads to unnecessary radiation dose burden to the patient. In addition,
proper collimating will lead to noise reduction in images, which will
potentially result in lower reject rates.
The results of this survey showed that participants are
familiar with digital radiography and have embraced this relatively new
technology as shown by the fact that they can identify both its advantages and
disadvantages as applied to clinical practice. There is, however, minimal
quality control of digital radiography being done at the surveyed institutions.
It is, therefore, recommended that users of digital X-ray units adopt
comprehensive national or international protocols [10, 21, 22]. Findings from
this study suggest that there is need for formal education, continuing
education and manufacturer training with respect to quality control as
institutions make the transition from conventional screen film radiology to digital
radiology. Stakeholders in the South African diagnostic radiology community
should establish the minimum staffing requirements for medical physicists
particularly for teaching hospitals.
The authors would like to thank the following people,
Miss. MM Pule, Mr. SA Ngcezu, Mr. P Segone and Mr. SG Somlota for helping with
the distribution and collection of the questionnaires. The Assistant Directors
in the respective radiology departments are also acknowledged for sanctioning
the study. Furthermore, all the respondents are acknowledged for their effort
and willingness to provide information which made this study possible.
Figure 1 Post qualification experience stratified by imaging modality.
Table 1 Advantages and disadvantages of digital radiography over screen-film radiography.
Table 2 Response rate based on returned questionnaires according to hospitals.
Table 3 Summary of key responses from study by participants
Table 4 The most commonly cited advantages of digital radiography over screen-film radiography (n=63)
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|Received 8 July 2009; received in revised form 3 September
2009, accepted 30 September 2009
Correspondence: Johannesburg Hospital, Area 248: Medical Physics, Private Bag X39, 2000 Johannesburg, Republic of South Africa. Tel.: +27 11 481 2158; Fax: +27 11 484 9202; E-mail: firstname.lastname@example.org (Thulani Nyathi).
Please cite as: Nyathi T, Chirwa TF, van der Merwe DG,
A survey of digital radiography practice in four South African teaching hospitals: an illuminative study, Biomed Imaging Interv J 2010; 6(1):e5