Limits...
Use of a radio frequency shield during 1.5 and 3.0 Tesla magnetic resonance imaging: experimental evaluation.

Favazza CP, King DM, Edmonson HA, Felmlee JP, Rossman PJ, Hangiandreou NJ, Watson RE, Gorny KR - Med Devices (Auckl) (2014)

Bottom Line: Attenuation, by as much as 35 dB, of RF field power was found inside the RF shield.These results were supported by temperature measurements of metallic leads placed inside the shield, in which no measurable RF heating was found.These results suggest that the RF shield could be a valuable tool for clinical MRI practices.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, Mayo Clinic, Rochester, MN, USA.

ABSTRACT
Radiofrequency (RF) shields have been recently developed for the purpose of shielding portions of the patient's body during magnetic resonance imaging (MRI) examinations. We present an experimental evaluation of a commercially available RF shield in the MRI environment. All tests were performed on 1.5 T and 3.0 T clinical MRI scanners. The tests were repeated with and without the RF shield present in the bore, for comparison. Effects of the shield, placed within the scanner bore, on the RF fields generated by the scanner were measured directly using tuned pick-up coils. Attenuation, by as much as 35 dB, of RF field power was found inside the RF shield. These results were supported by temperature measurements of metallic leads placed inside the shield, in which no measurable RF heating was found. In addition, there was a small, simultaneous detectable increase (∼1 dB) of RF power just outside the edges of the shield. For these particular scanners, the autocalibrated RF power levels were reduced for scan locations prescribed just outside the edges of the shield, which corresponded with estimations based on the pick-up coil measurements. Additionally, no significant heating during MRI scanning was observed on the shield surface. The impact of the RF shield on the RF fields inside the magnet bore is likely to be dependent on the particular model of the RF shield or the MRI scanner. These results suggest that the RF shield could be a valuable tool for clinical MRI practices.

No MeSH data available.


RF heating of metallic leads submerged in the ASTM head-and-torso phantom with and without the RF shield wrapped around the phantom and enclosing the leads: (A) 1.5 T and (B) 3.0 T.Note: The 4-echo spin echo pulse sequence begins at 25 seconds and ends at the 420 second mark in both (A and B).Abbreviations: RF, radiofrequency; ΔT, change in temperature.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4219642&req=5

f6-mder-7-363: RF heating of metallic leads submerged in the ASTM head-and-torso phantom with and without the RF shield wrapped around the phantom and enclosing the leads: (A) 1.5 T and (B) 3.0 T.Note: The 4-echo spin echo pulse sequence begins at 25 seconds and ends at the 420 second mark in both (A and B).Abbreviations: RF, radiofrequency; ΔT, change in temperature.

Mentions: As shown in Figure 6, the shield suppressed RF heating in the metallic leads at both 1.5 T and 3.0 T. Without the shield, maximal temperature increases of about 4.5°C at 1.5 T and 3°C at 3.0 T were measured at 1.5 T and 3.0 T. With the added protection of the RF shield, heating was reduced to about 0.2°C at 1.5 T and 0.5°C at 3.0 T. Notably, the metallic leads near the edges of the phantom and correspondingly closer to the bore wall demonstrated greater heating than the center wire.


Use of a radio frequency shield during 1.5 and 3.0 Tesla magnetic resonance imaging: experimental evaluation.

Favazza CP, King DM, Edmonson HA, Felmlee JP, Rossman PJ, Hangiandreou NJ, Watson RE, Gorny KR - Med Devices (Auckl) (2014)

RF heating of metallic leads submerged in the ASTM head-and-torso phantom with and without the RF shield wrapped around the phantom and enclosing the leads: (A) 1.5 T and (B) 3.0 T.Note: The 4-echo spin echo pulse sequence begins at 25 seconds and ends at the 420 second mark in both (A and B).Abbreviations: RF, radiofrequency; ΔT, change in temperature.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4219642&req=5

f6-mder-7-363: RF heating of metallic leads submerged in the ASTM head-and-torso phantom with and without the RF shield wrapped around the phantom and enclosing the leads: (A) 1.5 T and (B) 3.0 T.Note: The 4-echo spin echo pulse sequence begins at 25 seconds and ends at the 420 second mark in both (A and B).Abbreviations: RF, radiofrequency; ΔT, change in temperature.
Mentions: As shown in Figure 6, the shield suppressed RF heating in the metallic leads at both 1.5 T and 3.0 T. Without the shield, maximal temperature increases of about 4.5°C at 1.5 T and 3°C at 3.0 T were measured at 1.5 T and 3.0 T. With the added protection of the RF shield, heating was reduced to about 0.2°C at 1.5 T and 0.5°C at 3.0 T. Notably, the metallic leads near the edges of the phantom and correspondingly closer to the bore wall demonstrated greater heating than the center wire.

Bottom Line: Attenuation, by as much as 35 dB, of RF field power was found inside the RF shield.These results were supported by temperature measurements of metallic leads placed inside the shield, in which no measurable RF heating was found.These results suggest that the RF shield could be a valuable tool for clinical MRI practices.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, Mayo Clinic, Rochester, MN, USA.

ABSTRACT
Radiofrequency (RF) shields have been recently developed for the purpose of shielding portions of the patient's body during magnetic resonance imaging (MRI) examinations. We present an experimental evaluation of a commercially available RF shield in the MRI environment. All tests were performed on 1.5 T and 3.0 T clinical MRI scanners. The tests were repeated with and without the RF shield present in the bore, for comparison. Effects of the shield, placed within the scanner bore, on the RF fields generated by the scanner were measured directly using tuned pick-up coils. Attenuation, by as much as 35 dB, of RF field power was found inside the RF shield. These results were supported by temperature measurements of metallic leads placed inside the shield, in which no measurable RF heating was found. In addition, there was a small, simultaneous detectable increase (∼1 dB) of RF power just outside the edges of the shield. For these particular scanners, the autocalibrated RF power levels were reduced for scan locations prescribed just outside the edges of the shield, which corresponded with estimations based on the pick-up coil measurements. Additionally, no significant heating during MRI scanning was observed on the shield surface. The impact of the RF shield on the RF fields inside the magnet bore is likely to be dependent on the particular model of the RF shield or the MRI scanner. These results suggest that the RF shield could be a valuable tool for clinical MRI practices.

No MeSH data available.