BJR
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
British Journal of Radiology (2006) 79, 315-318
© 2006 British Institute of Radiology
doi: 10.1259/bjr/66912494
This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF)
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Anderson, D W
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Anderson, D W

Full Paper

Introduction of grids to mobile ICU radiography in a teaching hospital

D W Anderson, MBBS (hons), FRANZCR

Monash Medical Centre, 246 Clayton Road, Clayton, Melbourne, Victoria, Australia 3168


   Abstract
Top
 Abstract
Introduction
 Methods
 Results
 Discussion
 References
 
The purpose of this study was to review the change in image quality before and after introducing grid use routinely to our mobile X-ray service. This was studied in the intensive care unit (ICU) setting, comparing images obtained over a 2 week period prior to and after the introduction of the change in technique. We introduced a 6:1 grid with appropriate changes in exposure factors. No other alterations were made. There were 133 patients in the preliminary group and 196 patients in the post-grid group. We found a reduction in the proportion of images that were of non-diagnostic or barely diagnostic quality. Non-diagnostic examinations were reduced from 18% to 1%. Introducing grids to our mobile service resulted in improvement in image diagnostic quality, largely by reducing the proportion of poor and unacceptable quality images. This effect does not appear to have been documented in the literature.


   Introduction
Top
 Abstract
 Introduction
Methods
 Results
 Discussion
 References
 
Monash Medical Centre (MMC) is a large teaching hospital in suburban Melbourne, Victoria. We have recently introduced grids to our mobile ward service. Data were collected before and after the introduction of grids to assess their impact on the diagnostic quality of images obtained on the daily morning intensive care unit (ICU) film round.


   Methods
Top
 Abstract
 Introduction
 Methods
Results
 Discussion
 References
 
All patients examined during the morning ICU X-ray round were collected for a 2 week period prior to the introduction of a grid technique. Images were obtained using GE AMX4 mobile machine and Agfa CR system. 1 month following the changed technique, data were again collected for a 2 week period. Images were obtained using a 6:1 grid landscape or portrait grid with GE AMX4 mobile machine and Agfa CR system. Both sets of images were viewed on BARCO monitors. Data for the 4 week period following the introduction of the new technique were not collected to allow staff to become familiar with changed techniques, particularly exposure alterations. This was thought desirable for repeatable and reliable patient examinations. The images were graded for diagnostic quality using a five point grading system as follows:

  1. not of diagnostic quality
  2. poor, barely adequate diagnostic quality
  3. fair, acceptable diagnostic quality
  4. good, above average diagnostic quality
  5. excellent diagnostic quality

Images were determined "not of diagnostic quality" if any of the following were present:

Also contributing to image grading was a subjective assessment of lung parenchymal detail, both the ability to satisfactorily characterize the nature and extent of infiltrates as well as the ability to resolve normal parenchymal architecture in areas of non-pathological lung. The components of our scoring system are similar to those used by others in the assessment of portable radiographs [1–3].

Images were graded independently by two experienced radiologists, each with more than 2 years experience with the display system used. Images were modified for window settings by each viewer to their satisfaction with active changes made during review of each image to fully interrogate each image to the satisfaction of the reviewers. Differences in grade were resolved by consensus.

A blinded interpretation of pre- and post-grid images was not attempted as the use of a grid results in discernable grid lines, rendering overt identification of technique used.


   Results
Top
 Abstract
 Introduction
 Methods
 Results
Discussion
 References
 
The initial image set performed before grid technique (total 133 patients) produced the following results:

The second image set, performed following the introduction of grid technique (total 196 patients) produced the following results:

The difference in group size was the result of differences in patient load in the ICU for the morning radiology service.

Figures 2–5GoGoGoGo are comparative chest X-rays performed on the same day with and without grids on two separate patients.


Figure 2
View larger version (118K):
[in this window]
[in a new window]
  		Figure 2. Chest radiograph no grid.

 

Figure 3
View larger version (126K):
[in this window]
[in a new window]
  		Figure 3. Same patient as Figure 2 with grid.

 

Figure 4
View larger version (110K):
[in this window]
[in a new window]
  		Figure 4. Chest radiograph no grid.

 

Figure 5
View larger version (123K):
[in this window]
[in a new window]
  		Figure 5. Same patient as Figure 4 with grid.

 

   Discussion
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
References
 
The initial data set produced a somewhat surprising result in that nearly one in five images (18%) was not of diagnostic quality. This was largely the result of not being able to identify the position or tip of various devices. Swan-ganz catheters and fine bore central lines were most often affected. There was also a contribution in many images from difficulties in reliably characterizing infiltrates. This was most notable in larger patients. In combination with barely acceptable images (category 2, 41%), our ICU mobile service was producing images of poor to unacceptable quality in nearly six out of 10 patients. Portable images had been acknowledged as of lesser quality than imaging performed in department. This had been considered a largely inevitable outcome given the compromises involved in portable imaging. The desire to investigate the impact of grids was prompted by their effect when used on a very large patient in the ICU in attempts to produce a diagnostic image. That grid use can result in a significant improvement in signal to noise ratio (SNR) at the cost of increased dose is well recognized [4–6].

Our service had not conducted a formal review of image diagnostic quality in any systematic fashion for some years, instead relying on an ad-hoc notification and correction of specific problems as they arose. Review had not been performed since the introduction of our film-less screen based CR reporting system. As such, we do not have a prior benchmark for comparison with these results.

The data set following introduction of grid technique shows a significant reduction in the proportion of images deemed not of diagnostic quality (18%>1%). There was also a significant reduction in category two images (41%>15%). As a result of these improvements, 78% of images were deemed of acceptable or above average diagnostic quality (53% category 3 + 25% category 4). Review of the literature shows little has been published quantifying the change in diagnostic viewing quality of mobile ICU images performed with and without grids. Two authors have stated that portable chest radiography is significantly improved with use of a 6:1 or 8:1 grid [7, 8], but without comparative evidence.

Introduction of grids has also introduced some new problems. All images contain discernable grid lines. Whilst visible, these were not thought to impede satisfactory image interpretation. Grid "cut-off" producing asymmetrical density was seen on approximately 30% of films. This was of variable severity but again did not appear to significantly affect image interpretability. No image was deemed category 1 as a result of grid cut-off. The finding that grid cut-off was not a significant problem is in keeping with the work of Grunert et al and Ciccotosto et al [2, 5, 9].

A grid technique results in an increased radiation dose to the patient. Rill et al stated that use of a grid resulted in a 400–600% increase in dose to their phantom for a 60–300% improvement in SNR [4]. Increasing tube potential from 80 kVp to 100 kVp resulted in further 10% increases in SNR and phantom dose. Similar dose increases and decreases in scatter radiation were found by Floyd et al [6]. Balanced against this is the critical status of the typical ICU patient with a requirement for the most accurate diagnostic information achievable. Most patients in our ICU are older adults with multiple co-morbidities. As such, the increased dose is acceptable. No attempt was made to assess the clinical relevance of changes to subjective image quality in this study as this lay outside our scope.

The intent of this article is to provide a small measure of our experience with introducing grids to our ICU mobile service and their impact on subjective radiologist assessed image quality, and the following limitations are acknowledged:

  1. The sample sizes are relatively small
  2. No attempt was made to correlate image quality with patient size (body mass index, BMI)
  3. No attempt was made to determine the effect of radiographer experience on image quality. MMC is a teaching hospital with staff of significantly varying experience
  4. No attempt has been made to determine if the subjective improvement in image quality has had any relevant effect on clinical decision making or patient outcome
  5. The study is unable to be performed in a blinded fashion due to image effects resulting from the intervention (grid use)
  6. The differences in sample size (patient load), may reflect further unknown confounding factors in the patients with independent effect on image quality. We made no attempt at randomization
  7. The introduction of a change in technique may have resulted in a change in the diligence of radiography staff regarding positioning, exposures and other factors

Optimizing image diagnostic quality is relevant in the ICU setting as other authors have found unexpected findings in 37–65% of patients [10–13]. Ekenmeyer et al stated changes were initiated in diagnostic approach or therapy as a result of CXR findings alone in 27% of patients [11]. Malpositioned ETT, central lines or catheters have been seen in 9–20% of patients [11, 13].

An American study from 1994 showed 12% of hospitals using grids for mobile chest radiography. It was not stated if this was routine or on a patient by patient basis [14]. Review of technique used by the other large public hospitals in our city found only one of four institutions were using grids for mobile ICU radiography and this was reserved for very large patients only. Reasons given included inconvenience and historical practice.


Figure 1
View larger version (13K):
[in this window]
[in a new window]
  		Figure 1. Comparison chest radiograph(CXR) pre- and post-grid.

 
Received for publication March 18, 2005. Revision received September 7, 2005. Accepted for publication September 15, 2005.


   References
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 

  1. Langevin PB, Hellein V, Harms SM, Tharp C, Cheung-Seekit C, Lampotang S. Synchronization of radiograph film exposure with the inspiratory pause. Am J Respir Crit Care Med 1999;160:2067–71.[Abstract/Free Full Text]
  2. Ciccotosto C, Storto ML, Guidotti A, Ferrante R, Bonomo L. Bedside thoracic radiography: a comparison between 3 different types of grid. Radiol Med (Torino) 1994;87:127–33.
  3. Rottenberg GT, Chin RJ, Allen CM, Maggs P, Kessel D. Portable chest radiology in intensive care: a comparison of a new dual characteristic film-screen system (Insight) incorporating a flexible grid with a standard film-screen system. Clin Radiol 1996;51:494–8.[CrossRef][Medline]
  4. Rill LN, Brateman L, Arreola M. Evaluating radiographic parameters for mobile chest computed radiography: phantoms, image quality and effective dose. Med Phys 2003;30:2727–35.[CrossRef][Medline]
  5. Grunert JH, Boy B, Groenwold SK, Krahn-Peters V, Hendrickx P. Use of multi-grid screens in intensive care units. Aktuelle Radiol 1995;5:293–6.[Medline]
  6. Floyd CE Jr, Chotas HG, Ravin CE. Scatter-reduction characteristics of an infinity-focussed gridded radiographic cassette. Invest Radiol 1994;29:852–5.[CrossRef][Medline]
  7. BHR 1980; HHS Publ 80–8124: 202–6
  8. Rossi RP, Harnisch BD, Hendee WR. Evaluation of an automatic exposure control device for mobile radiography. Radiology 1982;145:823–7.[Free Full Text]
  9. Grunert JH, Boy B, Busche D, Groenewold SK, Herrmann H, Krahn-Peters V, et al. Grids and high kilo-volt-peak-setting in bedside chest radiographic examinations. JBR-BTR 2000;83:296–9.
  10. Janower ML, Jennas-Nocera Z, Mukai J. Utility and efficacy of portable chest radiographs. AJR Am J Roentgenol 1984;142:265–7.[Abstract/Free Full Text]
  11. Ekenmeyer WB, Crapo RO, Calhoon S, Cannon CY, Clayton PD. Efficacy of chest radiography in a respiratory intensive care unit. A prospective study. Chest 1985;88:691–6.[Abstract/Free Full Text]
  12. Greenbaum DM, Marschall KE. The value of daily chest x-rays in intubated patients in the medical intensive care unit. Crit Care Med 1982;10:29–30.[Medline]
  13. Henschke CI, Pasternak GS, Schroder S, Hart KK, Herman PG. Bedside chest radiography: diagnostic efficacy. Radiology 1983;149:23–6.[Abstract/Free Full Text]
  14. Wandtke JC. Bedside chest radiography. Radiology 1994;190:1–10.[Abstract/Free Full Text]




This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF)
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Anderson, D W
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Anderson, D W

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
BJR DMFR IMAGING  ALL BIR JOURNALS