THE MEDICAL PHYSICS CONSULT
MAHADEVAPPA MAHESH, MS, PhD
Portable Wireless Digital Detectors: Advantages and Challenges Mahadevappa Mahesh, MS, PhD, Bruce Berlenstein, MD, Jonathan Lewin, MD Wireless digital detectors are gaining increased use in mobile unit medical imaging. These detectors allow rapid, high-quality imaging anywhere, anytime in a hospital, allowing physicians in many instances to make fast decisions at the bedside. Medical imaging manufacturers are rolling out wireless digital detectors that are increasingly efficient and rugged. Most wireless digital detectors weigh about 3 to 4 kg and are comparatively heavier than film-screen cassettes or computed radiography cassettes, yet they are increasingly embraced because of efficiency in speed and convenience of delivering images [1]. Portable unit wireless digital detectors that are currently in use are amorphous siliconebased thin-film transistor arrays with scintillator (mostly cesium iodide or gadolinium oxysulfide) deposited on top that converts x-rays into light photons [1,2]. These detectors have the potential to deliver patient care efficiently and improve workflow. Yet the efficiency and convenience offered by these detectors are introducing new challenges to workflow and to some extent to the radiation dose burden for patients in cases such as central venous catheter (CVC) placement. More than 5 million CVCs or central lines are placed each year in the United States [3]. Most line placements are performed in surgical suites, often fluoroscopic or ultrasound guidance. Often, placement is verified by acquiring a radiograph. Although the need for such postoperative radiography is in debate [4], in most cases, an image is acquired for verification of position before catheter use. In fact, the FDA recommends obtaining such radiographs 212
after the insertion of a catheter [5] to avoid future complications and infections due to incorrect placement. Often, CVC placement is performed under fluoroscopic guidance (considered the gold standard) using a fluoroscopic C-arm unit in the surgical suite or by transporting the patient to a stationary fluoroscopy suite. Radiologists perform CVC placement in fluoroscopy suites or read the radiographs obtained at patients’ bedsides with mobile unit radiographic systems. This workflow requires a radiographer to transport a mobile radiographic system to the desired location, such as the surgical suite or the patient ward, and obtain a radiograph for verification. With the influx of portable wireless digital detectors [1], often the physician performing CVC placement requires the technologists to leave the wireless detector in place (underneath the patient) while the physician verifies the positioning, resulting in the acquisition of multiple radiographs that could be avoided if the same procedure were performed under fluoroscopic guidance. When line placement becomes complex, there is an increasing tendency to acquire additional radiographs to verify the location of the CVC tip. The speed of image availability at the beside makes this very tempting. In addition to the radiation burden, the workflow disturbance arising from tying up the detector and the technologists for more than the usual time is introducing complex policy issues in hospitals. The purposes of this article are to discuss this issue not just from a radiation dose point of view but also from a workflow point of view
and to suggest recommendations that are feasible and beneficial to both patients and physicians. When film-screen cassettes or computed radiographic plates are used with mobile radiographic systems, after acquiring each image, the cassettes must be removed from beneath the patient to process or read the images, and subsequent images are obtained after repositioning the cassettes. This time requirement is a deterrent to the acquisition of multiple radiographs or using portable radiography in place of fluoroscopic guidance. In such situations, few radiographs (between 1 and 3) are obtained, and if the CVC placement is not successful, the patient is transported to the surgical or fluoroscopy suite to perform CVC placement under fluoroscopic guidance. Typical CVC line placement is performed between 5 and 30 seconds of fluoroscopic guidance, and the patient is then returned to the ward. With wireless digital detectors, once the detector is positioned under the patient’s bed and because the images are transmitted wirelessly to the display monitor on the mobile system (Fig. 1), there has been an increase in the number of radiographs acquired, in our experience. This has multiple repercussions, namely, not only are larger numbers of radiographs acquired, increasing radiation dose burden, but each radiograph is to be ordered separately for billing purpose (which can add to procedure cost) and read immediately by radiologists (when requested) while the mobile unit remains in place for the entire procedure. This can disrupt workflow because the mobile radiography unit and the wireless digital detector become unavailable
ª 2014 American College of Radiology 1546-1440/14/$36.00 http://dx.doi.org/10.1016/j.jacr.2013.11.008
The Medical Physics Consult 213
Fig 1. Wireless digital detector (35 43 cm) in a portable radiographic system retrofitted with a display monitor stationed outside an operating room.
for other studies until completion of the line placement study. In fact, with the proliferation of portable wireless digital detectors, we are observing that about 10% of line placement procedures are incurring >3 x-rays, up to 9 radiographs or even more. For the patient from the radiation dose point of view, if a line placement procedure requires >3 x-rays, it will be advantageous to have the procedure performed under fluoroscopic guidance, as the radiation dose will be much lower (onehalf to one-third) with fluoroscopy than by acquiring multiple radiographs (Table 1). With this in mind, a hospitalwide policy regarding line placement is considered. The main objectives for the policy are to lower radiation dose burden, make efficient use of portable imaging technology and portable wireless
digital detectors, and provide a safe environment during x-ray imaging on patient units for nurses, physicians, and all health care professionals who participate in line placement procedures. The policy in consideration is as follows: The physician requesting the study must enter a STAT electronic order in Physician Ordering Entry (POE) system. Upon seeing the order in the Radiology Information System (RIS), the Imaging Technologist will respond to the unit within
20-25 minutes with an available portable x-ray unit. The Physician performing the procedure will indicate to the technologist when the x-ray is needed. A maximum of 3 radiographs can be taken to complete the procedure. If placement is complicated and cannot be resolved after three radiographs, patient should be moved to the fluoroscopic area for line placement under fluoroscopy guidance unless patient condition dictates to do more imaging for completion of procedure at the bedside.
This policy provides the opportunity to efficiently maintain workflow,
Table 1. Radiation dose comparison for a CVC placement procedure involving radiographic exposures (1e3 radiographs) obtained with a portable wireless digital detector and a procedure performed under fluoroscopic guidance (1e30 seconds) Patient Radiation Modality Typical Procedure Dose (mSv) Radiography (portable x-ray unit) Fluoroscopy
1e3 radiographs 1e30 s of fluoroscopy time
0.05e0.15 0.005e0.15
214 The Medical Physics Consult
deliver timely imaging service, lower radiation dose, and use wireless digital detectors efficiently. CONCLUSIONS
The demand for high-quality imaging anywhere, anytime in the hospital is increasing and is challenging day-to-day workflow to efficiently balance available resources such as mobile wireless digital detectors, x-ray technologists time, and radiation burden to patients and staff members. Implementing policy to curtail the
excessive use of portable wireless digital detectors and direct to more efficient resources is a balanced approach that is beneficial to both patients and physicians.
2. Samei E, Murphy S, Christianson O. DQE of wireless digital detectors: Comparative performance with differing filtration schemes. Med Phys 2013;40:081910.
ACKNOWLEDGMENTS
3. McGee DC, Gould MK. Preventing complications of central venous catheterization. N Engl J Med 2003;348:1123-33.
We thank Angela Kim and Paula Frank for their assistance. REFERENCES 1. Comparison charts for wireless portable digital detectors. Imaging Technology News. Available at: http://www.itnonline.com/comparison-
charts?t¼DigitalþRadiographyþSystems. Accessed Oct 29, 2013
4. Keckler SJ, Spilde TL, Ho B, et al. Chest radiograph after central line placement under fluoroscopy: utility or futility? J Pediatr Surg 2008;48:854-6. 5. US Food and Drug Administration. Precautions necessary with central venous catheters. FDA Task Force. FDA Drug Bull 1989;July:15-6.
Mahadevappa Mahesh, MS, PhD, Bruce Berlenstein, MD, and Jonathan Lewin, MD, are from The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland. Mahadevappa Mahesh, MS, PhD, Johns Hopkins University, The Russell H. Morgan Department of Radiology and Radiological Science, 601 N Caroline Street, Baltimore, MD 21287-0856; e-mail: [email protected].
MAHADEVAPPA MAHESH, MS, PhD
Portable Wireless Digital Detectors: Advantages and Challenges Mahadevappa Mahesh, MS, PhD, Bruce Berlenstein, MD, Jonathan Lewin, MD Wireless digital detectors are gaining increased use in mobile unit medical imaging. These detectors allow rapid, high-quality imaging anywhere, anytime in a hospital, allowing physicians in many instances to make fast decisions at the bedside. Medical imaging manufacturers are rolling out wireless digital detectors that are increasingly efficient and rugged. Most wireless digital detectors weigh about 3 to 4 kg and are comparatively heavier than film-screen cassettes or computed radiography cassettes, yet they are increasingly embraced because of efficiency in speed and convenience of delivering images [1]. Portable unit wireless digital detectors that are currently in use are amorphous siliconebased thin-film transistor arrays with scintillator (mostly cesium iodide or gadolinium oxysulfide) deposited on top that converts x-rays into light photons [1,2]. These detectors have the potential to deliver patient care efficiently and improve workflow. Yet the efficiency and convenience offered by these detectors are introducing new challenges to workflow and to some extent to the radiation dose burden for patients in cases such as central venous catheter (CVC) placement. More than 5 million CVCs or central lines are placed each year in the United States [3]. Most line placements are performed in surgical suites, often fluoroscopic or ultrasound guidance. Often, placement is verified by acquiring a radiograph. Although the need for such postoperative radiography is in debate [4], in most cases, an image is acquired for verification of position before catheter use. In fact, the FDA recommends obtaining such radiographs 212
after the insertion of a catheter [5] to avoid future complications and infections due to incorrect placement. Often, CVC placement is performed under fluoroscopic guidance (considered the gold standard) using a fluoroscopic C-arm unit in the surgical suite or by transporting the patient to a stationary fluoroscopy suite. Radiologists perform CVC placement in fluoroscopy suites or read the radiographs obtained at patients’ bedsides with mobile unit radiographic systems. This workflow requires a radiographer to transport a mobile radiographic system to the desired location, such as the surgical suite or the patient ward, and obtain a radiograph for verification. With the influx of portable wireless digital detectors [1], often the physician performing CVC placement requires the technologists to leave the wireless detector in place (underneath the patient) while the physician verifies the positioning, resulting in the acquisition of multiple radiographs that could be avoided if the same procedure were performed under fluoroscopic guidance. When line placement becomes complex, there is an increasing tendency to acquire additional radiographs to verify the location of the CVC tip. The speed of image availability at the beside makes this very tempting. In addition to the radiation burden, the workflow disturbance arising from tying up the detector and the technologists for more than the usual time is introducing complex policy issues in hospitals. The purposes of this article are to discuss this issue not just from a radiation dose point of view but also from a workflow point of view
and to suggest recommendations that are feasible and beneficial to both patients and physicians. When film-screen cassettes or computed radiographic plates are used with mobile radiographic systems, after acquiring each image, the cassettes must be removed from beneath the patient to process or read the images, and subsequent images are obtained after repositioning the cassettes. This time requirement is a deterrent to the acquisition of multiple radiographs or using portable radiography in place of fluoroscopic guidance. In such situations, few radiographs (between 1 and 3) are obtained, and if the CVC placement is not successful, the patient is transported to the surgical or fluoroscopy suite to perform CVC placement under fluoroscopic guidance. Typical CVC line placement is performed between 5 and 30 seconds of fluoroscopic guidance, and the patient is then returned to the ward. With wireless digital detectors, once the detector is positioned under the patient’s bed and because the images are transmitted wirelessly to the display monitor on the mobile system (Fig. 1), there has been an increase in the number of radiographs acquired, in our experience. This has multiple repercussions, namely, not only are larger numbers of radiographs acquired, increasing radiation dose burden, but each radiograph is to be ordered separately for billing purpose (which can add to procedure cost) and read immediately by radiologists (when requested) while the mobile unit remains in place for the entire procedure. This can disrupt workflow because the mobile radiography unit and the wireless digital detector become unavailable
ª 2014 American College of Radiology 1546-1440/14/$36.00 http://dx.doi.org/10.1016/j.jacr.2013.11.008
The Medical Physics Consult 213
Fig 1. Wireless digital detector (35 43 cm) in a portable radiographic system retrofitted with a display monitor stationed outside an operating room.
for other studies until completion of the line placement study. In fact, with the proliferation of portable wireless digital detectors, we are observing that about 10% of line placement procedures are incurring >3 x-rays, up to 9 radiographs or even more. For the patient from the radiation dose point of view, if a line placement procedure requires >3 x-rays, it will be advantageous to have the procedure performed under fluoroscopic guidance, as the radiation dose will be much lower (onehalf to one-third) with fluoroscopy than by acquiring multiple radiographs (Table 1). With this in mind, a hospitalwide policy regarding line placement is considered. The main objectives for the policy are to lower radiation dose burden, make efficient use of portable imaging technology and portable wireless
digital detectors, and provide a safe environment during x-ray imaging on patient units for nurses, physicians, and all health care professionals who participate in line placement procedures. The policy in consideration is as follows: The physician requesting the study must enter a STAT electronic order in Physician Ordering Entry (POE) system. Upon seeing the order in the Radiology Information System (RIS), the Imaging Technologist will respond to the unit within
20-25 minutes with an available portable x-ray unit. The Physician performing the procedure will indicate to the technologist when the x-ray is needed. A maximum of 3 radiographs can be taken to complete the procedure. If placement is complicated and cannot be resolved after three radiographs, patient should be moved to the fluoroscopic area for line placement under fluoroscopy guidance unless patient condition dictates to do more imaging for completion of procedure at the bedside.
This policy provides the opportunity to efficiently maintain workflow,
Table 1. Radiation dose comparison for a CVC placement procedure involving radiographic exposures (1e3 radiographs) obtained with a portable wireless digital detector and a procedure performed under fluoroscopic guidance (1e30 seconds) Patient Radiation Modality Typical Procedure Dose (mSv) Radiography (portable x-ray unit) Fluoroscopy
1e3 radiographs 1e30 s of fluoroscopy time
0.05e0.15 0.005e0.15
214 The Medical Physics Consult
deliver timely imaging service, lower radiation dose, and use wireless digital detectors efficiently. CONCLUSIONS
The demand for high-quality imaging anywhere, anytime in the hospital is increasing and is challenging day-to-day workflow to efficiently balance available resources such as mobile wireless digital detectors, x-ray technologists time, and radiation burden to patients and staff members. Implementing policy to curtail the
excessive use of portable wireless digital detectors and direct to more efficient resources is a balanced approach that is beneficial to both patients and physicians.
2. Samei E, Murphy S, Christianson O. DQE of wireless digital detectors: Comparative performance with differing filtration schemes. Med Phys 2013;40:081910.
ACKNOWLEDGMENTS
3. McGee DC, Gould MK. Preventing complications of central venous catheterization. N Engl J Med 2003;348:1123-33.
We thank Angela Kim and Paula Frank for their assistance. REFERENCES 1. Comparison charts for wireless portable digital detectors. Imaging Technology News. Available at: http://www.itnonline.com/comparison-
charts?t¼DigitalþRadiographyþSystems. Accessed Oct 29, 2013
4. Keckler SJ, Spilde TL, Ho B, et al. Chest radiograph after central line placement under fluoroscopy: utility or futility? J Pediatr Surg 2008;48:854-6. 5. US Food and Drug Administration. Precautions necessary with central venous catheters. FDA Task Force. FDA Drug Bull 1989;July:15-6.
Mahadevappa Mahesh, MS, PhD, Bruce Berlenstein, MD, and Jonathan Lewin, MD, are from The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland. Mahadevappa Mahesh, MS, PhD, Johns Hopkins University, The Russell H. Morgan Department of Radiology and Radiological Science, 601 N Caroline Street, Baltimore, MD 21287-0856; e-mail: [email protected].
