Increased interest of clinicians for using 3.0 T magnetic resonance imaging (MRI), as imaging modality of choice for their patients, has been evident in the past few years. The aim of this study was to compare the technical quality of the obtained tomography using 3.0 T and 1.5 T MRI, and to compare the subjective feeling of discomfort of patients and subjective acoustic noise experience during imaging using MRI at 3.0 T and 1.5 T. Brain MRI (1.5 and 3.0 T) was performed in 58 patients, according to a standardized protocol. All studies have been randomly described by independent two radiologists. The reference standard for the existence of technical artifact is established on the basis of both radiologists’ consensus. We also compared the subjective feelings of the discomfort and acoustic noise during the both MRI (1.5 T and 3.0 T) exams. Artifacts were significantly more common during 3.0 T MRI in comparison with the 1.5 T MRI (χ2 = 5.286, P < 0.05), as well as in male patients (χ2 = 8.841, P < 0.05), and sub-jective assessments of discomfort and acoustic noise were higher in patients who underwent imaging using 3.0 T MRI, (χ2 = 125.959, df = 1, P < 0.001) and in females (χ2 = 195.449, df = 1, P < 0.001). Additional research is needed to prove that appropriate information for patients about the discomfort during 3.0 T MRI and their psychological preparation is very important element for optimal use of 3.0 T MRI in daily clinical practice.
Magnetic resonance imaging (MRI) is considered to be a safe imaging technique. From the first days of using MRI, there have been a lot of attempts to make scanner with stronger magnetic field [
Susceptibility artifacts could be useful for detection of hemoglobin breakdown products [
Good quality examination largely depends on how an individual tolerates lying in the MR scanner, environment and performed procedures. Factors influencing a reduced tolerance patient for all MR scanners independent of magnetic field strength are extended time of scanning, ambient temperature, acoustic noise, uncomfortable position during laying and a personal level of the discomfort [
The strongest level of noise that was measured during the noisiest sequences at 1.5 T MRI was 101 - 117 dB [
Anxiety patients are more likely to experience claustrophobia during MRI, in up to 35% of cases [
The aim of this study was to compare the technical quality of the obtained tomography using 3.0 T and 1.5 T MRI, and to compare the subjective feeling of discomfort of patients and subjective acoustic noise experience during imaging using MRI at 3.0 T and 1.5 T.
The study was conducted as a prospective study from 30 September 2013 to 01 May 2014 in the Department of Clinical Radiology, University Medical Centre in Banja Luka. The study included 58 patients suffering from epilepsy older than 6, both gender.
The study was approved by the Ethics Committee of the Clinical Center of Banja Luka. Before each examination patients were thoroughly informed by the radiologist about examination, duration of the imaging, noise exposure, and confinement. Patients were informed that imaging could be discontinued at any time. All patients gave informed consent to participate in this study. For juvenile patients informed consent for participation in the study was given by parents. Before imaging each patient filled out a security form of the Institute of Clinical Medicine, which was explained to each patient individually. For juvenile patients, the security form was filled out by their parents.
Each patient was examined using a MR scanner at 1.5 T as well as the MR scanner at 3.0 T. The time interval between the two MRIs was not longer than 14 days. Visualizations were performed using 1.5-T MR scanner (Avanto, Siemens, Erlangen, Germany), software version NUMARIS/4 (syngo MR B13) coil Head Matrix Coil (12-element design, IPAT-compatible coil for standard and advanced neuro applications) and 3.0-T MR scanner (GE Signa, General Electric, Milwaukee, WI, USA), software version mRose: GEHCMR_1.1-8_cselx1.1_OS MrpApps: 15.0_M4B_1034.a, coil HD NV Array (8-chan- nel, 12-element phased array design).
Identical, standardized protocol was applied for each MRI. A standardized protocol includes sagittal T1W tomography, T2W, and FLAIR axial tomography parallel to the axis of the temporal lobe, and T2W, FLAIR, STIR/T1 FSPGR tomography in coronal plane and optionally triplane contrast T1W.
Radiologists registered technical artifacts that lead to the degradation of MR images, which were related to the MR scanners and displacement of the patient. The presence of technical artifact radiologists evaluated with “Yes or No”. The following was notified: artifacts caused by displacement, movement, artifacts caused by magnetic field distortion, aliasing artifacts, artifacts caused by metal objects, chemical shift artifacts, Gibbs artifacts. All artifacts that were identified by both radiologists were compared with a reference standard. The reference standard for the existence of technical artifact is established on the basis of both radiologists’ consensus.
Levels of general discomfort that might have been experienced during both MRI were evaluated and reported by the patients using values of 1 to 10. Value 1 corresponded to the absence of any discomfort, while a value 10 corresponded to the intolerable discomfort.
Levels of acoustic noise that might have been experienced during the both MRI were evaluated and reported by the patients using scale from 1 to 10. Value 1 corresponds to the absence of any acoustic noise, until a value 10 corresponds to the state of intolerable acoustic noise. Noise and discomfort evaluation was not correlated with MRI sequences.
Data on the subjective feeling of discomfort and subjective feeling of exposure to noise were entered in the forms created by the author.
Statistical program SPSS for Windows software (SPSS18.0, Inc., Chicago, Illinois, USA) and Microsoft Excel (Microsoft Corporation, Redmond, WA, USA) was used for statistical analysis of the data obtained.
All results will be properly statistically analyzed (descriptive statistics, sensitivity, specificity, appropriate statistical tests with significance level of P < 0.05).
The study included 58 patients suffering from epilepsy, 30 men (51.7%) and 28 women (48.3%). The average age of patients was 27.6 (±14.1) with a range of 9 - 70 years. Most of patients (33 of them), were 11 to 30 years old (56.9%). Three patients manifested anxiety and claustrophobia during the first MRI (man and woman at 3.0 T and man at 1.5 T) and withdrawal examinations. They have been excluded from the study.
For 1.5 T MR scanner, radiologists by consensus included 10 MRI exams in the reference standard (interrater agreement coefficient at 1.5 T was 0.837) and for 3.0 T MRI they included 15 MRI exams, with artifacts that significantly degraded image quality (interrater agreement coefficient at 3-T was 0.828) (
The following was evaluated: effects of gender, the strength of MRI and their relations with the number of artifacts by consensus using Brunner-Langer nonparametric ANOVA. The results showed that there was a statistically significant difference in the number of artifacts in men and women (χ2 = 8.841, P < 0.05), as well as a statistically significant difference in the number of artifacts at 1.5 T and at 3.0 T (χ2 = 5.286, P < 0.05). Artifacts were more common in men than women and more common seen at 3.0 T (
There were 11 artifacts in 10 patients at 1.5 T MRI and 18 artifacts in 15 patients at 3.0 T MRI (
It was tested whether the effects of gender and their interaction on the discomfort evaluation (based on consensus) were significant, using Brunner-Langer non-parametric ANOVA. The results showed that there was a statistically significant difference between estimates of discomfort for men and women (χ2 = 13.623, df = 1, P < 0.001), average rank of estimates of discomfort for men was 43.583, and for women 63.798. So, we could conclude that the assessment of discomfort was greater for women than for men (
Artifacts | |||||
---|---|---|---|---|---|
Yes | No | ||||
N | % | N | % | ||
The first radiologist | 1.5 T | 11 | 19.0 | 47 | 81.0 |
3.0 T | 15 | 25.9 | 43 | 74.1 | |
The second radiologist | 1.5 T | 12 | 20.7 | 46 | 79.3 |
3.0 T | 17 | 29.3 | 41 | 70.7 | |
Consensus | 1.5 T | 10 | 17.2 | 48 | 82.8 |
3.0 T | 15 | 25.9 | 43 | 74.1 | |
Interrater agreement coefficient for 1.5 T MRI was 0.837 | |||||
Interrater agreement coefficient for 3 T MRI was 0.828 |
Number of artifacts | ||
---|---|---|
Magnetic field strength | Gender | |
M | F | |
1.5 T | 9 | 1 |
3.0 T | 12 | 3 |
χ2 = 5.286, P = 0.022 | χ2 = 8.841, P = 0.003 |
Artifactscaused by | 1.5 T | 3.0 T | ||
---|---|---|---|---|
men | women | men | women | |
Movement | 4 | 1 | 6 | 2 |
Distorsion of magnetic field | 2 | 0 | 3 | 1 |
Metal objects | 2 | 1 | 2 | 1 |
Other | 1 | 0 | 2 | 1 |
Total | 9 | 2 | 13 | 5 |
Evaluation of patient’s discomfort in relation to gender and magnetic field strength | |||
---|---|---|---|
Average rank for discomfort estimates | Brunner-Langer non-parametric ANOVA | ||
Gender | M | 43.583 | χ2 = 13.623, P < 0.001 |
F | 63.798 | ||
Magnetic field strength | 1.5 T | 36.186 | χ2 = 125.959, P < 0.001 |
3.0 T | 71.196 |
Also, it was tested whether the effects of MR strength and their interaction on the discomfort evaluation (based on consensus) were significant, using Brunner-Langer non-parametric ANOVA. The results showed that there was a statistically significant difference between estimates of discomfort for 1.5 T and 3.0 T MRI (χ2 = 125.959, df = 1, P < 0.001). Average rank of estimates of discomfort for 1.5 T MRI was 36.186, and for 3.0 T MRI was 71.196. So, we could conclude that the assessment of discomfort was greater for 3.0 T MRI than for 1.5 T MRI (
It was tested whether the effects of gender and their interaction on the patient’s evaluation regarding acoustic noise (based on consensus) were significant, using Brunner-Langer non-parametric ANOVA. The results showed that there was a statistically significant difference between estimates of acoustic noise for men and women (χ2 = 15.256, df = 1, P < 0.001). Average rank of estimates of acoustic noise for men was lower (44.380) in comparison to women (62.971) (
Also, it was tested whether the effects of MR strength and their interaction on the patient evaluation of acoustic noise (based on consensus) were significant, using Brunner-Langer non-parametric ANOVA. Average rank of estimates of acoustic noise for 1.5 T MRI was 32.937, and for 3.0 T MRI was 74.413. The results showed that there was a statistically significant difference between estimates of acoustic noise for 1.5 T and 3.0T MRI (χ2 = 195.449, df = 1, P < 0.001). Average rank of estimates of acoustic noise for 1.5 T MRI was lower (32.937) in comparison to 3.0 T MRI (74.413) (
Calculated correlation coefficients (Pearson and Spearman correlation coefficient) are those between the age of patients and, respectively, discomfort and acoustic noise that patients experienced during the MRI at 1.5 T or at 3.0 T. The correlation coefficients were not significantly different from zero (in all cases, P-value of the test was greater than 0.05). There was no correlation between the age of patients and the discomfort or acoustic noise that patients experienced during the MRI at 1.5 T or at 3.0 T (
With a statistically significant difference there was greater number of artifacts registered on 3.0 T MR scanner versus 1.5 T MR scanner and they were seen more common in males than in females. The largest number of artifacts are caused by the movement, and then because of magnetic field distortion.
Research by Phal and associates showed that artifacts, due to displacements, were
Evaluation of acoustic noise in relation to gender and magnetic field strength | |||
---|---|---|---|
Average rank for discomfort estimates | Brunner-Langer non-parametric ANOVA | ||
Gender | M | 44.380 | χ2 = 15.256, P < 0.001 |
F | 62.971 | ||
Magnetic field strength | 1.5 T | 32.937 | χ2 = 195.449, P < 0.001 |
3.0 T | 74.413 |
Variable | MR | Pearson’s correlations coefficient | Test statistics | Spearman rank correlation coefficient | Test statistics |
---|---|---|---|---|---|
Acoustic noise | 1.5 T | 0.039 | t = 0.276, df = 51 P = 0.784 | 0.059 | t = 0.425, df = 51 P = 0.672 |
3.0 T | −0.138 | t = −0.995, df = 51 P = 0.325 | −0.070 | t = −0.501, df = 51 P = 0.618 | |
Discomfort | 1.5 T | −0.129 | t = −0.926, df = 51 P = 0.359 | −0.105 | t = −0.752, df = 51 P = 0.456 |
3.0 T | −0.141 | t = −1.015, df = 51 P = 0.321 | −0.120 | t = −0.861, df = 51 P = 0.393 |
equally expressed at 1.5 T and 3.0 T, while other artifacts were significantly lower at 3.0 T [
In the paper by Zijlmans and associates of the examined 27 patients, artifacts were registered in 1 patient who underwent 1.5 T MRI due to displacement and in 2 patients who underwent 3.0 T MRI, and one patient was excluded from analysis due to demonstrated artefacts at 3.0 T MRI [
In our research, the subjective assessment of acoustic noise in patients who underwent 3.0 T MRI is significantly higher compared to patients who underwent MRI at 1.5 T, and subjective assessment of noise is greater in women than in men. Also, the subjective assessment of discomfort on patients who underwent 3.0 T MRI is significantly higher compared to patients who underwent 1.5 T MRI, and subjective assessment of discomfort is greater in women than in men.
Price and colleagues measured the noise of 15 different MR scanners, magnitude 0.2 to 3.0 Tesla [
In the paper by Chou et al., acoustic noise is the most common cause of discomfort for children and youth who underwent MRI at 3.0 T [
Less than 20% of children who underwent 3.0 T MRI complained of general discomfort, feeling cold, claustrophobia, and dizziness. Weintraub and colleagues reported for the 1023 patients who underwent 3.0 T MRI the following: sensory inconvenience in 14% patients, with dizziness, headaches and low back pain were more common in patient who underwent 3.0 T MRI, and metallic taste in the mouth was more common in patients who underwent 1.5 T MRI [
Study by Esed and associates revealed that claustrophobia occurred more often in females, with no significant difference [
Results of the study conducted by Dawey and associates, which included 55,000 patients who had undergone various MRI examinations, showed that the claustrophobia was statistically more common in women and middle-aged patients [
In our study there was no correlation between the age of patients and the discomfort or acoustic noise that patients experienced during 1.5 T or 3 T MRI. One patient at 3.0 T MRI (the second exam) exhibited symptoms of claustrophobia in the middle of the procedure. The exam was completed with additional effort of personnel and few interruptions and pronounced artifacts. Patients which have anxiety and claustrophobia that require sedation and anesthesia have been excluded from the study because they could not objectively estimate, noise and general discomfort.
To avoid claustrophobic reactions of patients, there are attempts to improve comfort during MRI, usually by reducing acoustic noise and reducing feelings of isolation simulating panoramic view [
MR scanner with an open gantry is useful for anxious patients. Until recently, their main disadvantage was the low field (0.2 T), which resulted in poor quality imaging. [
In the past few years, increased interest of clinicians for using 3.0 T MR scanner as imaging modality for their patients is evident. The reason is a superior spatial and temporal resolution and better signal to noise ratio compared to 1.5 T MRI. On the other hand, clinical practice shows that the success of MRI depends not only on the above- mentioned parameters, but also on a whole range of other parameters that are related to scanner, staff and patients.
Our results showed that artifacts were significantly more common during 3.0 T MRI in comparison with the 1.5 T MRI, as well as in male patients, and subjective assessments of discomfort and acoustic noise were higher in patients who underwent 3.0 T MRI, and in females. Appropriate information for patients about discomfort during 3.0 T MRI, and their psychological preparation is very important element for optimal use of 3.0 T MRI in daily clinical practice. The future will probably show new technological solutions that will reduce the feeling of discomfort and noise and thus contribute to quality imaging.
Vujmilović, S., Vuj- nović, S., Kovačević-Dragosavljević, V., Vuj- ković, Z., Katana, D. and Grujić-Vujmilović, D. (2016) Patient’s Comfort and Technical Quality Exams at 1.5 and 3.0 T Magnetic Re- sonance Imaging. Open Journal of Radiology, 6, 264-274. http://dx.doi.org/10.4236/ojrad.2016.64035