"Programmable ventriculoperitoneal shunts are adjustable shunts to treat hydrocephalus by diverting cerebrospinal fluid to the peritoneum. The programmable valve settings are changed by a device with a strong magnetic field supplied by the manufacturer which changes the opening pressure of the ventricular system in the brain. Some shunts are designed so that they are not affected by the magnetic field of MRI scanners however it is recommended that all programmable shunt settings be checked with a plain radiograph of the head following an MRI study to ensure that the settings were not altered 4."
"Programmable ventriculoperitoneal shunts are adjustable shunts to treat hydrocephalus by diverting cerebrospinal fluid to the peritoneum. The programmable valve settings are changed by a device with a strong magnetic field supplied by the manufacturer which changes the opening pressure of the ventricular system in the brain. Some shunts are designed so that they are not affected by the magnetic field of MRI scanners however it is recommended that all programmable shunt settings be checked with a plain radiograph of the head following an MRI study to ensure that the settings were not altered 4."
"More of an annoyance than a safety problem is the ability of the magnetic field of a MRI machine to erase the information contained on the magnetic strip on ATM and credit cards. This may occur a short distance inside of the scanner room of a MRI machine. In addition mechanical watches will "freeze up" in a strong field, sometimes permanently."
"The radiofrequency (RF) power that is capable of being produced matches that of many small radio stations (15-20 kW). As a result there is the presence of heating effects from the RF, known as the specific absorption rate. In most pulse sequences, the heating is insignificant and does not exceed FDA guidelines. However echo planar imaging (EPI) and some spectroscopy localisation techniques are capable of exceeding FDA guidelines. Monitoring of the power deposition in patients is a requirement for FDA approval of clinical MRI scanners."
"The radiofrequency (RF) power that is capable of being produced matches that of many small radio stations (15-20 kW). As a result there is the presence of heating effects from the RF, known as the specific absorption rate. In most pulse sequences, the heating is insignificant and does not exceed FDA guidelines. However echo planar imaging (EPI) and some spectroscopy localisation techniques are capable of exceeding FDA guidelines. Monitoring of the power deposition in patients is a requirement for FDA approval of clinical MRI scanners."
"The radiofrequency (RF) power that is capable of being produced matches that of many small radio stations (15-20 kW). As a result there is the presence of heating effects from the RF, known as the specific absorption rate. In most pulse sequences, the heating is insignificant and does not exceed FDA guidelines. However echo planar imaging (EPI) and some spectroscopy localisation techniques are capable of exceeding FDA guidelines. Monitoring of the power deposition in patients is a requirement for FDA approval of clinical MRI scanners."
Expected headings
"Main magnetic field"
"Varying magnetic (gradient) fields"
"Radiofrequency"
"The main magnetic field (B0) of a 1.5 T magnet is about 30,000 times the strength of the earth's magnetic field. It is strong enough to pull heavy-duty floor buffers and mop buckets into the bore of the magnet, move trolleys across the room and turn oxygen bottles into hazardous projectiles (missile effect). Deaths have occurred from trauma as a result of these effects. Smaller objects such as coins, hairpins and pens have been yanked off the person carrying them."