Subjective symptoms of SMFs and RF energy, and risk perception among staff working with MR scanners within two public hospitals in South Africa

Figures & data

Table 1. Characteristics of study participants

Characteristics	Exposed participants		Control participants		chi square test
	N	%	N	%
AGE
Mean	34.62		34.59		0.21
Std.±	7.8		10.02
Gender
Male	22	44	11	41	0.000*
Female	28	46	16	59
Job titles
Radiographers	14	28	27	100	0.000*
Nurses	13	26
Medical physicists	2	4
Radiologists	4	8
Maintenance engineers	2	4
Others (porters and cleaners)	15	30
No. of Years in the MRI units
Median	5				0.44
Min.	1
Max.	15
Range	14
Hospital employed
A	20	41	15	56	0.000*
B	26	53	12	44
Both	3	6
Presence in the scanner room during work shifts (days)					0.043*
1	15	20
2	10	13
3	6	8
4	2	3
5	15	20
Longer stay in the scanner room due to irregularities					0.003*
Yes	15	20
No	35	46
Scanner worked on
1.5 T	27	35			0.000*
3.0 T	20	3
Both	2	26
Presence in the scanner room during image acquisitioning (times)					0.016*
0	29	38
1	9	12
2	7	9
3	4	5
4	1	1
Shift duration in the MRI unit
N/A	24	31			0.000*
1 hr	2	3
2 hrs	2	3
8 hrs	22	29
Movement of head/upper body in the scanner bore (times)					0.000*
0	25	33
1	16	21
2	4	5
3	3	4
4	2	3
Tiring workweek
Very tiring	18	36	9	33	0.000*
A little tiring	30	60	18	67
Hardly tiring	1	2	0	0
Workload
Light	1	2	16	59	0.000*
Moderate Heavy	37	74	11	41
	12	24	0	0

N = number of participants; % = percentages; *significant p-values; 24 participants did not work shifts in the MRI units however, they frequent zone IV to perform certain activities. N/A= part of exposed group that do not work shifts in the MRI units.

Table 2. Overview of reported symptoms between exposed and control group on the Likert scale

	Likert scale					Study groups
Symptoms	Never	Seldom	Half of the time	Usually	Always	Exposed group N %	Control group N
Tinnitus or sensation of head ringing ^a	45	16	2	0	0	18 36	0
Headache ^c	41	21	0	1	0	22* 44	0
Concentration problems ^a	60	3	0	0	0	3 6	0
Tiredness or sleepiness ^c	60	2	0	1	0	3 6	0
Nausea ^a	43	17	3	0	0	20 40	0
Involuntary muscle contractions ^a	61	1	1	0	0	2 4	0
Sensation of glowing, burning or irritated skin ^b	61	2	0	0	0	2 4	0
Suddenly feeling warm/hot, hot flushes ^b	50	13	0	0	0	13 26	0
Sensation of dizziness or vertigo ^a	34	15	14	0	0	20 40	0
Feeling lightheaded or weightless ^a	49	14	0	0	0	14 28	0
Feeling of instability when standing, walking or moving ^a	34	16	13	0	0	29 58	0
A metallic taste ^a	34	9	19	1	0	29 58	0

^{*One radiographer (from CT scan, assigned to exposed group) reported headache; a SMFs-related symptoms; b RF energy-related symptoms; c SHC symptoms;}

Table 3. Relationship between predictors and subjective symptoms using logistic regression

Predictors	Job title	Gender	Years in the MRI units	Shift duration	Scanner worked on	Workload	Tiring workweek	Medication use
Symptoms
Tinnitus	OR: 0.12 CI: 0.02, 0.85 p < .03*	OR: 2.67 CI: 0.48, 15.17 p < .26	OR: 1.47 CI: 0.25, 8.70 p < .67	OR: 0.64 CI: 0.12, 3.39 p < .60	OR: 8.00 CI: 1.51, 42.46 p < .02*	OR: 0.69 CI: 0.11, 4.17 p < .68	OR: 0.14 CI: 0.02, 1.23 p < .08	OR: 0.28 CI: 0.04, 1.93 p < .20
Headache	OR: 0.35 CI: 0.07, 1.67 p < .19	OR: 0.71 CI: 0.15, 3.36 p < .66	OR: 4.57 CI: 0.96, 21.70 p < .05*	OR: 1.56 CI: 0.33, 7.35 p < .58	OR: 2.14 CI: 0.52, 8.83 p < .30	OR: 1.57 CI: 0.31, 7.96 p < .59	OR: 0.67 CI: 0.14, 3.23 p < .62	OR: 0.35 CI: 0.07, 1.61 p < .18
Nausea	OR: 0.06 CI: 0.01, 0.48 p < .01*	OR: 11.20 CI: 1.57, 79.92 p < .02*	OR: 0.45 CI: 0.08, 2.56 p < .37	OR: 0.37 CI: 0.06, 2.13 p < .27	OR: 0.93 CI: 0.20, 4.25 p < .92	OR: 2.66 CI: 0.45, 15.75 p < .28	OR: 0.17 CI: 0.03, 1.13 p < .07	OR: 0.19 CI: 0.03, 1.15 p < .07
Suddenly feeling warm/hot, hot flushes	OR: 0.79 CI: 0.15, 4.23 p < .78	OR: 0.72 CI: 0.15, 3.59 p < .69	OR: 2.86 CI: 0.52, 15.60 p < .23	OR: 2.39 CI: 0.51, 11.16 p < .27	OR: 1.25 CI: 0.29, 5.41 p < .76	OR: 1.08 CI: 0.19, 6.04 p < .93	OR: 0.31 CI: 0.05, 1.91 p < .20	OR: 0.32 CI: 0.07, 1.54 p < .16
Sensation of dizziness or vertigo	OR: 0.35 CI: 0.08, 1.59 p < .18	OR: 4.43 CI: 0.91, 21.47 p < .07	OR: 2.09 CI: 0.47, 9.34 p < .34	OR: 1.76 CI: 0.39, 7.90 p < .05*	OR: 0.93 CI: 0.23, 3.74 p < .92	OR: 2.70 CI: 0.49, 14.86 p < .25	OR: 0.18 CI: 0.03, 0.99 p < .05*	OR: 0.77 CI: 0.16, 3.61 p < .74
Feeling lightheaded or weightless	OR: 0.14 CI: 0.02, 1.20 p < .07	OR: 1.27 CI: 0.19, 8.62 p < .81	OR: 3.99 CI: 0.53, 29.95 p < .18	OR: 0.21 CI: 0.03, 1.58 p < .13	OR: 9.67 CI: 1.44, 64.92 p < .02*	OR: 0.82 CI: 0.11, 6.30 p < .85	OR: 0.23 CI: 0.02, 2.40 p < .22	OR: 0.15 CI: 0.02, 1.11 p < .06
Feeling of instability when standing, walking or moving	OR: 0.35 CI: 0.08, 1.59 p < .18	OR: 4.43 CI: 0.91, 21.47 p < .07	OR: 2.09 CI: 0.47, 9.34 p < .34	OR: 1.76 CI: 0.39, 7.90 p < .46	OR: 0.93 CI: 0.23, 3.74 p < .92	OR: 2.70 CI: 0.49, 14.86 p < .25	OR: 0.18 CI: 0.03, 0.99 p < .05*	OR: 0.77 CI: 0.16, 3.61 p < .74
A metallic taste	OR: 0.19 CI: 0.04, 0.96 p < .05*	OR: 6.42 CI: 1.27, 32.51 p < .03*	OR: 1.42 CI: 0.31, 6.58 p < .65	OR: 1.14 CI: 0.25, 5.35 p < .86	OR: 1.23 CI: 0.30, 5.11 p < .77	OR: 2.83 CI: 0.51, 15.85 p < .24	OR: 0.20 CI: 0.04, 1.10 p < .06	OR: 1.07 CI: 0.22, 5.23 p < .94

^{*Significant p values (≤ 0.05); adjusted for gender and medication use.}

Table 4. Relationship between predictors and subjective symptoms using linear regression

Predictors	Job title	Gender	Years in the MRI units	Shift duration	Scanner worked on	Workload	Tiring workweek	Medication use
Symptoms
Involuntary muscle contraction	B: −0.010 CI: −0.146,0.126 p < .883	B: −0.033 CI: −0.160,0.093 p < .598	B: 0.081 CI: −0.054,0.215 p < .234	B: 0.070 CI: −0.063,0.202 p < .295	B: −0.066 CI: −0.183,0.052 p < .265	B: −0.037 CI: −0.179,0.105 p < .600	B: −0.060 CI: −0.186,0.066 p < .344	B: −0.038 CI: −0.172,0.097 p < .575
Concentration problems	B: −0.059 CI: −0.225, 0.106 p < .472	B: −0.071 CI: −0.225, 0.082 p < .354	B: 0.044 CI: −0.120, 0.207 p < .592	B: 0.102 CI: −0.058, 0.263 p < .206	B: −0.010 CI: −0.152, 0.133 p < .891	B: −0.051 CI: −0.224, 0.121 p < .549	B: −0.068 CI: −0.221, 0.086 p < .378	B: −0.012 CI: −0.175, 0.152 p < .887
Sensation of glowing, burning or irritated skin	B: 0.174 CI: 0.051,0.297 p < .007a	B: −0.144 CI: −0.258,-0.030 p < .015a	B: 0.187 CI: 0.066, 0.309 p < .003a	B: 0.071 CI: −0.048,0.190 p < .234	B: 0.006 CI: −0.100,0.112 p < .905	B: −0.059 CI: −0.187,0.069 p < .355	B: −0.029 CI: −0.143,0.085 p < .611	B: −0.032 CI: −0.153,0.089 p < .596
Tiredness or sleepiness	B: −0.095 CI: −0.237, 0.047 p < .183	B: −0.010 CI: −0.142,0.121 p < .873	B: −0.022 CI: −0.163,0.118 p < .750	B: −0.009 CI: −0.147,0.129 p < .892	B: 0.027 CI: −0.096,0.149 p < .660	B: 0.051 CI: −0.097,0.199 p < .491	B: 0.032 CI: −0.099,0.164 p < .624	B: 0.073 CI: −0.067,0.213 p < .298

^{aSignificant p values (≤ 0.05); gender and medication use were adjusted for (cofounders).}

Table 5. Reporting of subjective symptoms based on the presence in zone IV

Symptoms	Relationship between symptoms and predictors
	R Square	Adjusted R Square	p- value
			longer stay in zone IV due to irregularities	Times in zone IV during image acquisitioning	Movement of head/ upper body in the scanner bore
Tinnitus	.226	.176	0.002*	0.29	0.35
Headache	.240	.191	0.005*	0.45	0.45
Concentration problems	.166	.112	0.015*	0.64	0.64
Tiredness	.095	.036	0.93	0.31	0.31
Nausea	.241	.192	0.004*	0.10	0.026*
Involuntary muscle contractions	.123	.065	0.017*	0.58	0.58
Sensation of glowing, burning or irritated skin	.616	.591	0.89	0.000*	0.000*
Suddenly feeling warm/hot, hot flushes	.204	.152	0.007*	0.51	0.15
vertigo	.246	.197	0.001*	0.81	0.014*
Feeling lightheaded	.291	.244	0.000*	0.15	0.42
Feeling of instability when standing or walking	.246	.197	0.001*	0.81	0.014*
metallic taste	.287	.241	0.000*	0.34	0.031*

* ^{Significant p values (≤ 0.05)}

Figure 1. Perceptions of MRI scanner safety among MRI staff.