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Medical Devices and Systems Exposure and Dosimetry
6.3.4 Magnetic Navigation
Endoscopy by miniaturized swallowable capsules with integrated imaging and transmission systems has become the gold standard for the endoscopic examination of the
gastrointestinal tract. Video capsule endoscopes contain one or two cameras, a light
source, batteries, electromagnetic transmitter and receiver, and magnetic elements for
navigation. Due to their miniaturization, capsules are small enough (e.g., 26 × 11 mm)
to be swallowed with water, usually after a 12-hour fast.
The capsule is propelled via peristalsis through the gastrointestinal tract and can be
magnetically navigated. For this purpose, capsules contain two diagonally mounted
rotatable permanent magnets. To steer the capsule, a static magnetic field is produced
by an external permanent magnet or an electromagnetic coil. In addition, capsules may
incorporate an electromagnetic actuator, which is controlled by wireless communication.
The combined use of external static magnetic fields and internal actuation to move
small permanent intracapsular magnets allow camera steering and orientation with
high accuracy (Valdastri et al. 2010). However, the exponential decrease of magnetic field strength with distance has major implications for precision of the remote
control.
Currently, there are two capsule endoscopes available: PillCam ESO and PillCam SB
for the evaluation of the esophagus and the small bowel, respectively. The PillCam ESO
has two cameras on each end and captures images at a rate of 7 frames per second by
each camera, whereas the PillCam SB has one camera and captures images at a rate of
2 frames per second. Both capsule endoscopes transmit the image data to a recording
device worn on the patient’s waist using a RF signal in the wireless local area network
(WLAN) or Bluetooth bandwidth (Li, Leighton, and Sharma 2007). After incorporation
and some delay to account for the transit time to reach the target region, images are continually acquired with an image storing speed of up to 18 frames per second (Eliakim
2010; Waterman and Gralnek 2009; Delvaux and Gay 2008).
The mean gastric transit time is about 63 minutes (10–319 minutes) and the mean
intestinal transit time about 194 minutes (70–322 minutes). The capsule reaches the
right colon in about 5–8 hours and is finally excreted naturally.
Capsule endoscopy is applied for the examination of the small bowel and other organs
in the gastrointestinal tract, including the esophagus and colon in several clinical situations such as obscure gastrointestinal bleeding, suspected Crohn’s disease, and surveillance of polyposis syndromes. In addition, they help screening for colorectal cancer,
esophageal varices, and Barrett’s esophagus.
Patients are exposed by the incorporated field source to static magnetic fields from
the intracorporal permanent magnetic navigation elements and RF EMF emitted by the
transmitting antenna.
6.3.5 Telemedicine
Wireless medical telemetry from medical device to medical device in a patient’s body,
from the body-worn device to an external monitoring device, or from a medical device
to a network (e.g., bedside data acquisition and monitoring) can directly cause exposure
Medical Devices and Systems Exposure and Dosimetry
6.3.4 Magnetic Navigation
Endoscopy by miniaturized swallowable capsules with integrated imaging and transmission systems has become the gold standard for the endoscopic examination of the
gastrointestinal tract. Video capsule endoscopes contain one or two cameras, a light
source, batteries, electromagnetic transmitter and receiver, and magnetic elements for
navigation. Due to their miniaturization, capsules are small enough (e.g., 26 × 11 mm)
to be swallowed with water, usually after a 12-hour fast.
The capsule is propelled via peristalsis through the gastrointestinal tract and can be
magnetically navigated. For this purpose, capsules contain two diagonally mounted
rotatable permanent magnets. To steer the capsule, a static magnetic field is produced
by an external permanent magnet or an electromagnetic coil. In addition, capsules may
incorporate an electromagnetic actuator, which is controlled by wireless communication.
The combined use of external static magnetic fields and internal actuation to move
small permanent intracapsular magnets allow camera steering and orientation with
high accuracy (Valdastri et al. 2010). However, the exponential decrease of magnetic field strength with distance has major implications for precision of the remote
control.
Currently, there are two capsule endoscopes available: PillCam ESO and PillCam SB
for the evaluation of the esophagus and the small bowel, respectively. The PillCam ESO
has two cameras on each end and captures images at a rate of 7 frames per second by
each camera, whereas the PillCam SB has one camera and captures images at a rate of
2 frames per second. Both capsule endoscopes transmit the image data to a recording
device worn on the patient’s waist using a RF signal in the wireless local area network
(WLAN) or Bluetooth bandwidth (Li, Leighton, and Sharma 2007). After incorporation
and some delay to account for the transit time to reach the target region, images are continually acquired with an image storing speed of up to 18 frames per second (Eliakim
2010; Waterman and Gralnek 2009; Delvaux and Gay 2008).
The mean gastric transit time is about 63 minutes (10–319 minutes) and the mean
intestinal transit time about 194 minutes (70–322 minutes). The capsule reaches the
right colon in about 5–8 hours and is finally excreted naturally.
Capsule endoscopy is applied for the examination of the small bowel and other organs
in the gastrointestinal tract, including the esophagus and colon in several clinical situations such as obscure gastrointestinal bleeding, suspected Crohn’s disease, and surveillance of polyposis syndromes. In addition, they help screening for colorectal cancer,
esophageal varices, and Barrett’s esophagus.
Patients are exposed by the incorporated field source to static magnetic fields from
the intracorporal permanent magnetic navigation elements and RF EMF emitted by the
transmitting antenna.
6.3.5 Telemedicine
Wireless medical telemetry from medical device to medical device in a patient’s body,
from the body-worn device to an external monitoring device, or from a medical device
to a network (e.g., bedside data acquisition and monitoring) can directly cause exposure