Changes

A survey of technicians at GE who had worked around 1.5 T and 4 T MRI machines over ther previous year.

A survey of technicians at GE who had worked around 1.5 T and 4 T MRI machines over ther previous year.

"A mild level of sensory experiences, apparently associated with motion within the field of the magnet, was reported by some of the volunteers during some of their exposures. A questionnaire regarding sensory effects associated with magnetic resonance scanners and possibly caused by the static magnetic field of these instruments, was given to nine respondents who had experience within both 1.5-T scanners and this 4-T scanner and to another group of 24 respondents who had experience only within 1.5-T scanners. For the sensations of vertigo, nausea, and metallic taste there was statistically significant (p less than 0.05) evidence for a field-dependent effect that was greater at 4 T. In addition, there was evidence for motion-induced magnetophosphenes caused by motion of the eyes within the static field."

"A mild level of sensory experiences, apparently associated with motion within the field of the magnet, was reported by some of the volunteers during some of their exposures. A questionnaire regarding sensory effects associated with magnetic resonance scanners and possibly caused by the static magnetic field of these instruments, was given to nine respondents who had experience within both 1.5-T scanners and this 4-T scanner and to another group of 24 respondents who had experience only within 1.5-T scanners. For the sensations of vertigo, nausea, and metallic taste there was statistically significant (p less than 0.05) evidence for a field-dependent effect that was greater at 4 T. In addition, there was evidence for motion-induced magnetophosphenes caused by motion of the eyes within the static field."

'''Kangarlu et al. 1999''' PMID 10609989

'''Kangarlu et al. 1999''' PMID 10609989

In a study on cognitive and cardiac effects of an 8T MRI machine:

In a study on cognitive and cardiac effects of an 8T MRI machine:

"During exposure, subjects were encouraged to verbalize any unusual sensations. The responses to these communications were later recorded on each subject file. According to our subjects, entrance into the magnet and passage through the high gradient region was the dominant characteristic sensations they experienced inside the magnetic field of 8 Tesla. They reported vertigo and metallic taste in the mouth, and slight tingling effects. Most of these reports (except occasional metallic taste) were rare once the subject was positioned at the isocenter. While subjects were being transferred through the region of maximum field gradient, six individuals felt that they needed to lower their insertion rate into the magnet to avoid the unusual sensations. Note, however, that these initial studies were conducted without a patient table."

"During exposure, subjects were encouraged to verbalize any unusual sensations. The responses to these communications were later recorded on each subject file. According to our subjects, entrance into the magnet and passage through the high gradient region was the dominant characteristic sensations they experienced inside the magnetic field of 8 Tesla. They reported vertigo and metallic taste in the mouth, and slight tingling effects. Most of these reports (except occasional metallic taste) were rare once the subject was positioned at the isocenter. While subjects were being transferred through the region of maximum field gradient, six individuals felt that they needed to lower their insertion rate into the magnet to avoid the unusual sensations. Note, however, that these initial studies were conducted without a patient table."

 

'''Chakeres et al. 2003''' PMID 12938130

'''Chakeres et al. 2003''' PMID 12938130

Tests of neuropsychological function in an 8T MRI machine (same machine as Kangarula 1999):  

Tests of neuropsychological function in an 8T MRI machine (same machine as Kangarula 1999):  

"A few of the subjects commented on mild dizziness or vertigo while entering or exiting the magnet, but there were no significant complaints related to exposure."

"A few of the subjects commented on mild dizziness or vertigo while entering or exiting the magnet, but there were no significant complaints related to exposure."

 

'''de Vocht et al 2003''' PMID 14523950

'''de Vocht et al 2003''' PMID 14523950

 

'''de Vocht et al 2006''' PMID 16374876

'''de Vocht et al 2006''' PMID 16374876

Survey of complaints among  MRI manufacturing workers at Philips Medical Systems. Nice features: videotaped workers moving around 1.0 T and  1.5 T magnets,  so got estimate of movement speed and magnetic field exposure; used X-ray assembly workers as a control group.  

Survey of complaints among  MRI manufacturing workers at Philips Medical Systems. Nice features: videotaped workers moving around 1.0 T and  1.5 T magnets,  so got estimate of movement speed and magnetic field exposure; used X-ray assembly workers as a control group.  

"Dizziness, concentration problems, metallic taste, and suggestions of head ringing were significantly more reported by exposed workers, with the latter two only being reported near 1.5-T MRI systems....Our results show that employees from an MRI manufacturing department who moved more rapidly in the RF cage and consequently generated a stronger dynamic field, indeed reported more complaints than individuals who moved at a slower pace through the SMFs. Furthermore, moving speed and intensity was found to be to a large extent a personal characteristic, with a large between-subject and a small within-subject variance.  

"Dizziness, concentration problems, metallic taste, and suggestions of head ringing were significantly more reported by exposed workers, with the latter two only being reported near 1.5-T MRI systems....Our results show that employees from an MRI manufacturing department who moved more rapidly in the RF cage and consequently generated a stronger dynamic field, indeed reported more complaints than individuals who moved at a slower pace through the SMFs. Furthermore, moving speed and intensity was found to be to a large extent a personal characteristic, with a large between-subject and a small within-subject variance."

'''de Vocht et al 2006''' PMID 16463303

'''de Vocht et al 2006''' PMID 16463303

Subjects seated right outside a 1.5 T and 3.0 T MRI machine to assess effects of stray field on neurobehavioral tests. Found deficits in hand-eye coordination, visual tracking, and processing of auditory and visual information.  

Subjects seated right outside a 1.5 T and 3.0 T MRI machine to assess effects of stray field on neurobehavioral tests. Found deficits in hand-eye coordination, visual tracking, and processing of auditory and visual information.  

"This study confirms that eye– hand coordination and  the visual domain are affected by exposure to SMFs. In  addition, our results suggest that processing of visual  and auditive information is also affected, and that an  exposure–response relation exists for visual and audi-tive working memory, eye– hand coordination speed, and visual-tracking tasks. However, since the stray fields to which the volunteers were exposed were very inhomogeneous, it was difficult to assess the actual exposure in a given time interval. Therefore, it remains unclear whether the speed of motion in combination with the gradient or the SMF strength is the more imporant factor in causing the neurobehavioral effects."

"This study confirms that eye– hand coordination and  the visual domain are affected by exposure to SMFs. In  addition, our results suggest that processing of visual  and auditive information is also affected, and that an  exposure–response relation exists for visual and audi-tive working memory, eye– hand coordination speed, and visual-tracking tasks. However, since the stray fields to which the volunteers were exposed were very inhomogeneous, it was difficult to assess the actual exposure in a given time interval. Therefore, it remains unclear whether the speed of motion in combination with the gradient or the SMF strength is the more imporant factor in causing the neurobehavioral effects."

 

'''de Vochet et al 2007''' PMID 17290435

'''de Vochet et al 2007''' PMID 17290435

Subjects seated right outside a 7T MRI machine to assess effects of stray field on neurobehavioral tests; highest exposure was 1.6 - 2.0 T (but a very high gradient). Deficits in visual tracking were found after head movements in the stray field, which might be secondary to vestibular effects (although no vertigo is reported in this paper).

Subjects seated right outside a 7T MRI machine to assess effects of stray field on neurobehavioral tests; highest exposure was 1.6 - 2.0 T (but a very high gradient). Deficits in visual tracking were found after head movements in the stray field, which might be secondary to vestibular effects (although no vertigo is reported in this paper).

"As shown, only visual tracking performance … differed significantly (P <.01) between different levels of static magnetic field exposure, and the magnitude of the effect also depended on the magnitude  of the exposure (P <.01). Performance of the Pursuit  Aiming II-test (P =.09) and the time to complete the line bisection-test (P =.06) showed a trend towards dependence on the magnitude of exposure, with borderline statistical significance. There was also a trend for the average deviance in the line bisection-test to improve with increased exposure (P =.08)....Since this and previous studies suggest that cognitive effects occur particularly in the visual sensory domain, a possible mechanism might be that the widely recognized  "vertigo’’ effect of moving in a magnetic field, might interfere with the vestibulo-ocular reflex."

"As shown, only visual tracking performance … differed significantly (P <.01) between different levels of static magnetic field exposure, and the magnitude of the effect also depended on the magnitude  of the exposure (P <.01). Performance of the Pursuit  Aiming II-test (P =.09) and the time to complete the line bisection-test (P =.06) showed a trend towards dependence on the magnitude of exposure, with borderline statistical significance. There was also a trend for the average deviance in the line bisection-test to improve with increased exposure (P =.08)....Since this and previous studies suggest that cognitive effects occur particularly in the visual sensory domain, a possible mechanism might be that the widely recognized  "vertigo’’ effect of moving in a magnetic field, might interfere with the vestibulo-ocular reflex."