Magnetic Field Magnetic Resonance Imaging Research Articles

Gender- and age-specific impairment of rat performance in the Morris water maze following prenatal exposure to an MRI magnetic field

We examined the effects of prenatal exposure (40 min/day, gestation days 12–18) of rats to a magnetic resonance imaging (MRI) magnetic field (MF) on their performance in the Morris water maze. At 2 months of age, female rats showed impaired performance. The animals spent longer time swimming and used inefficient strategies. However, no significant effects on maze performance were observed at 1 and 5 months of age. No evident maze performance deficit was detected in male rats prenatally exposed to the magnetic field. Thus, we conclude that prenatal exposure to MRI magnetic field induces cognitive/behavioral deficits in female rats at a specific age.

Application of transcutaneous blood carbon dioxide monitoring to the magnetic resonance imaging of rat.

A transcutaneous blood gas monitor is a non-invasive tool that is used clinically. Magnetic resonance imaging (MRI) of the rat has been performed for basic research of pathology and brain science. Non-invasive monitoring of blood gas is expected for such small animal experiments because of the need to minimize blood loss. We applied a commercially available transcutaneous blood gas monitor to rat experiments with MRI. The monitoring responses to rat arterial tension of carbon dioxide (paCO2) appeared to change exponentially with the time constant 1820 +/- 40 s, which was five times slower than that of man. The jump in paCO2, however, can be translated only by a differential slope of values monitored by transcutaneous measurement of carbon dioxide (tcpCO2) at the timing of paCO2 change without waiting for the saturated value of tcpCO2. The magnetic field of MRI did not affect blood gas monitoring and magnetic material in the blood gas sensor did not jeopardize the magnetic homogeneity of imaging. The transcutaneous blood gas monitor can be applied to MRI measurements with paCO2 jumps.

Magnetic resonance imaging implications of metal-reinforced spinal microcatheters

Study Objective: To estimate the magnetic behavior of ferrous-alloy, wire-reinforced microcatheters for subarachnoid anesthesia and the possible hazards of exposing patients to magnetic resonance imaging (MRI) after accidental catheter fracture within the subarachnoid space. Design: Open, qualitative in vitro study. Setting: MRI facility of a university-affiliated medical center. Measurements and Main Results: Measurements were made of the angular deflection of 28-gauge and 32-gauge TFX catheters from their resting alignment by a small bar magnet. Mobility of 28-gauge catheter fragments 3.0 to 3.5 cm in length and 3.3 to 4.0 mg in mass were tested (1) when lying free on a polished surface in an MRI magnetic field of 1.5 tesla and 60 cm from the magnetic casing, and (2) when mounted on a mildly viscous agar surface 40 to 50 cm from the magnetic casing. Catheters were attracted to a small bar magnet and could be pulled out of alignment by the magnetic attraction to a degree inversely proportional to their caliber. Catheter fragments released in a magnetic field of 1.5 tesla flew from a glass surface and attached themselves firmly to the magnet casing, while catheter fragments adhering to an agar surface were not levitated but were rotated from their resting orientation. Conclusions: The microcatheters under test exhibited marked magnetic properties. Two questions arise: First, should MRI be avoided in patients where broken TFX catheter fragments may lie partly or completely within the subarachnoid space? Second, should ferrous metallic strengthening wire be replaced by a nonmetallic fiber of comparable or greater tensile strength? Further in vitro studies are indicated to answer these questions.