By definition, a ____________ is an authoritative report or guide that often addresses issues and how to selve them.

342

white paper

The bioeffects of RF irradiation include:

346

• heating of tissues
• RF antennae effects
• thermal injuries

The biologic effect of RF absorption is _________________.

347

It can be measured in units of ___________ and expressed in terms of ________.

347

There have been a number of burns and even fires associated with exposure to the __________ in MRI.

348

As the flip angle is doubled (for example from 90° to 180° flip angles), the power increases by a factor of ________.

348

___________ create a time-varying magnetic field (TVMF) that result in unique safety considerations from those associated with the RF and static field.

349

TVMF effects include:

349

• peripheral nerve stimulation
• magneto-phosphenes
• acoustic noise

TVMF effects vary with the ___________, ___________ and __________ of the gradient pulses.

349

Effects occasionally experienced during MRI examinations using echo planar techniques include mild cutaneous sensations and involuntary muscle contractions. This phenomenon is known as _________________.

350

_____________ sequences pose the greatest concern for TVMF effects as strong gradients are switched rapidly during         "    "       acquisition.

350

Visual effects may occur when retinal phosphates are stimulated by induction from TVMF. This phenomenon is known as _______________ and is described as 'stars in one's eyes' or presents as light flashes.

350

Most studies show no effects on cell growth and morphology at field strengths below ______.

352

In _____________, scans are times to the patient's heartbeat and triggered by the R wave.

352

Some reversible biologic effects have been observed on human subjects exposed to 2.0 T and above. These effects include:

253

• fatigue
• headaches
• hypotension
• irritability

Two forces cause ferromagnetic materials and devices to move when in the proximity of a static magnetic field. These forces are known as the _____________ force and the ____________ force.

254

The ___________ force is responsible for ferromagnetic objects being violently attracted into the MRI scanner.

355

The ___________ force is responsible for the aneurysm clip moving or twisting when entering the bore of the magnet.

354

The magnetic field strength decreases with the ___________ of the distance from the magnet.

358

Zone I is defined as follows:

358

• all areas that are freely accessible to the general public
• generally includes the parking lot, the general hallway, etc.
• all personnel are permitted in Zone I

Zone II is defined as follows:

358

• is the interface between the publicly accessible uncontrolled Zone I and the strictly controlled Zone III
• generally pertains to the patient waiting room

Zone III is defined as follows:

359

• generally pertains to the dressing room and/or the console area; this area should be strictly monitored as it is the interface to Zone IV

Zone IV is defined as follows:

359

• is only suitable for screened patients under direct constant supervision of MRI staff as there is a risk of patient heating, RF antenna effects, missile effects and anoxia due to quench pipe failure.

Patient and personnel ___________ is the most effective way to avoid potential safety hazards to patients.

360

Testing for implants and prostheses includes, but is not limited to the following characteristics:

361

• torque and heating
• functionality of the device
• device interference with image quality
• artefacts
• safety associated with particular devices.

Many facilities recommend that MR is delayed until _________ weeks after surgery.

363

Certain implanted devices are _____________ or _______________ for MR imaging because they are magnetically, electrically or mechanically activated.

366