Intraoperative CT- MGH Neurosurgical Service

Technology & the Neurosurgery Operating Rooms:

Neuro Control Room | Surgical Planning & IGS | Stereotactic Neurosurgery
Intra-Operative MRI | Intra-Operative CT | Intra-Operative Electrophysiology
Neuro ORs | Neuro Intensive Care Unit (NICU)

Intra-Operative CT:

Intra-Operative CT:

Mobile CT Unit in
Neuro ICU

Old Analogic Mobile CT Scanner
vs.
New Neurologica CereTom

Intra-Operative CT:
Mobile CT in Neuro ICU

Mobile CT in Neuro ICU

Mobile CT Unit in
Neuro ICU

A Mobile CT Scanner with Intraoperative and ICU Applications

William E. Butler, M.D.
Cristina M. Piaggio, B.S.
Christodoulous Constantinou, Ph.D.
Loren Nicklason, Ph.D.
R. Gilberto Gonzalez, M.D, Ph.D.
G. Rees Cosgrove, M.D.
Nicholas T. Zervas, M.D.

Neurosurgical Service
Massachusetts General Hospital
Boston, MA

Abstract - A Mobile CT with Intraoperative and ICU Applications

Introduction:

A mobile 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.

Methods:

The scanner 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.

Results:

The preclinical 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.

Discussion and Conclusions:

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.

[Mobile CT 1]

[Mobile CT 2]

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
An ICU 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 Wall Outlet
Translating Gantry

Radiation Considerations

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 dose

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 thickness
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.

[Mobile CT 3]

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 thickness
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.

[Mobile CT 4]

MGH Intraoperative Mobile CT Program

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

Patient is positioned in a radiolucent headframe, on a narrow radiolucent shoulder holder.

If intraoperative CT is ordered, the gantry is positioned about the head, and the CT scan is obtained.

[Mobile CT 5]

Photo of intraoperative CT. A clear sterile bag is placed over the sterile field

[Mobile CT 6]

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.

Intraoperative CT to Query Residual Tumor
29 F Recurrent Right Thalamic Astrocytoma
[Mobile CT 7]

[Mobile CT 7]

Preoperative MRI

[Mobile CT 8]

Intraoperative CT. A barium-impregnated cottonoid is placed at the bottom of the resection margin. This margin is then evaluated with intraoperative CT.

Stereotactic Biopsy

[Mobile CT 9]

43M R temporal abscess
The stereotactic CT scan is obtained in the OR with the patient on the OR table.

Immediate Postoperative CT - 69 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.

[Mobile CT 10]

Preoperative axial MRI

[Mobile CT 11]

Preoperative coronal MRI

[Mobile CT 12]

Post-extubation CT

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