- A Mobile CT with Intraoperative
and ICU Applications
computed tomography (CT) scanner has been developed in which
the scan plane is selected by means of gantry translation rather
than by translation of the patient table. This permits CT scanning
in situ patient who is positioned on a radiolucent surface that
fits within the inner diameter of the gantry. We report the
design of and initial experience with this scanner as used with
adaptors for intraoperative and bedside CT.
is equipped with wheels, runs on wall outlets (120V, 20A) in
combination with batteries, and has a translating gantry. Preclinical
studies of image quality were performed with phantoms. An operating
table adaptor was built for use with a radiolucent cranial fixation
device. A bedside adaptor was built that holds the head and
shoulders of an intensive care unit (ICU) patient.
phantom studies showed satisfactory image spatial resolution
(0.8mm) and low-contrast resolution signal to noise SD (0.37%).
Experience to date with 12 operative patients confirmed the
feasibility of intraoperative CT on demand. Experience to date
has confirmed the feasibility of routine bedside CT in the ICU.
With these adaptations,
mobile CT may increase the efficiency of intraoperative scanning
by making it available to multiple operating rooms without committing
it to any room for an entire operation, and increase the efficiency
and safety of CT of critically ill patients who currently need
to leave the ICU to travel to a fixed CT installation and back.
Bedside ICU CT scan of 70 F with intracerebral hematoma.
MGH ICU Mobile CT Program
- Perform CT in the ICU
at the bedside
- Avoid transporting
critically ill patients to and from the fixed CT suite
patient must be positioned on a radiolucent surface that fits
within the inner diameter of the CT gantry. To accomplish this,
the patient is turned 90 degrees so that the head and torso
are supported by a bedside adaptor. The gantry is positioned
about the head, and the CT scan is obtained.
Mobile CT Key Features
- On Wheels
- Fits on Elevators
- Draws Power from Electrical
- Translating Gantry
- Can Perform CT on Any
- Resting on a Radiolucent
- Fits in the Inner
Diameter of the Gantry
- U.S. limit of annual
radiation beyond background to the general public: 100 mR/year
- Annual background levels
from environment (naturally occurring in soils, radon, and cosmic
rays): 300 mR/year
- Annual radiation for
occupationally exposed workers: 5000 mR/year effective body
These radiation measurements indicate that mobile CT is safe
for ICU and OR use with precautions similar to those used
for other portable x-ray devices.
Scatter Radiation from the Mobile CT Scanner
- Outside of ICU
room with no lead shield: 2 mR/exam (20 slices/scan)
- A lead shield reduces
radiation by a factor of approximately 50
- Measurements taken
using body phantom, 120 KV, 50 mA, 4 seconds, 10 mm slice
- A at 1 meter from
phantom, at 45o angle; B at 1 meter from phantom along table
axis; C at door with door closed, standing in corridor;
D at door with door open (2.5-2.6 meters); E at window outside
room (2.5-2.6 meters); F at window inside room (2.3 meter);
G at 1 meter 45o to left, protected by lead shield; H at
1 meter, 45o to left, before lead shield; I at 1 meter from
phantom at scanner side.
MGH Intraoperative Mobile
- Make intraoperative
CT available to a maximum Number of Cases
- Permit intraoperative
CT while requiring minimal preoperative planning
- Require minimal or
no change in existing surgical protocols, routines or instruments
- Allow intraoperative
CT on-demand at any point in the case
- Require mobile CT scanner
in the operating room only when it is actually in use
positioned in a radiolucent headframe, on a narrow radiolucent shoulder
CT is ordered, the gantry is positioned about the head, and the
CT scan is obtained.
Photo of intraoperative CT. A clear sterile bag is placed
over the sterile field
Prior to draping, the fit of the head into the gantry
is confirmed with a metal loop with same inner diameter
as the CT gantry.
CT to Query Residual Tumor
29 F Recurrent Right Thalamic Astrocytoma
A barium-impregnated cottonoid is placed at the bottom
of the resection margin. This margin is then evaluated
with intraoperative CT.
43M R temporal abscess
The stereotactic CT scan is obtained in the OR with
the patient on the OR table.
Immediate Postoperative CT
M Craniotomy for L frontal parasagital meningioma.
Upon emergence from anesthesia and extubation in the OR, the
patient was noted to have a dense right hemiparesis. To exclude
hematoma at the operative site, the mobile CT was brought
into the OR and a head CT obtained. It demonstrated the expected
edema. The patient was then released to the recovery room.
Preoperative axial MRI
Preoperative coronal MRI
A mobile computed tomographic
scanner with intraoperative and intensive care unit applications.
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