MRI Radiographers Research Articles

Supporting claustrophobic patients during Magnetic Resonance Imaging examination– the patient perspective

IntroductionMagnetic Resonance Imaging (MRI) is a common imaging modality used to diagnose disease and monitor treatment. However, some patients cannot complete their MRI examination as a result of claustrophobia. The recent developments in the MRI scanner design may have reduced the incidence of claustrophobia in MRI. This study aimed to explore the claustrophobic patients’ experience to better understand how to support them. MethodsA qualitative descriptive approach using focus groups was deemed appropriate for the study. The research was advertised in a print newspaper and on social media platforms for eligible participants to contact the researcher. Six claustrophobic patients were recruited to the focus group meeting. The discussion was audio recorded and transcribed. Content analysis was used to analyse the data into code and categories. ResultsFour themes emerged from the data analysis, which included examination preparation, information provision, coping mechanisms and MR scanner design. Participants reported that the confined space in the MRI scanner bore is responsible for their anxiety during MRI. However, the majority of the participants believe that they would be able to complete the examination if, in advance of their scan, they were shown the MRI scanner and what they would be required to do. ConclusionSeveral coping mechanisms were shared by the participants on how they were able to complete their MRI examination despite their claustrophobia. MRI radiographers should endeavour to use these mechanisms to support their patients in practice. Also, the findings emphasise the importance of virtual reality and clear communication with patients in preparing them for their MRI examinations. Implications for practiceThe findings of this study may be used to enhance claustrophobic patients’ experience in MRI. It also identified those aspects of the MRI examination that matter most to patients with claustrophobia in order to provide a suitable intervention to support these patients.

Application of synthetic data in the training of artificial intelligence for automated quality assurance in magnetic resonance imaging.

Magnetic resonance imaging scanner faults can be missed during routine quality assurance (QA) if they are subtle, intermittent, or the test being performed is insensitive to the type of fault. Coil element malfunction is a common fault within MRI scanners, which may go undetected for quite some time. Consequently, this may lead to poor image quality and the potential for misdiagnoses. Daily QA typically consists of an automated signal to noise ratio test and in some instances this test is insensitive to coil element malfunction. Instead of relying on daily QA testing, it was proposed to utilize patient images in conjunction with a trained neural network to detect coil element malfunction, even when it presents as a very subtle defect. The advantage to using patient images over phantom testing is real-time monitoring can be achieved. This allows clinical staff to focus more on patient throughput without being burdened by daily testing. A neural network was trained using simulated coil failure in 3958 abdominal or pelvic images from 497 patients. The accuracy of the trained network was then tested on an unseen dataset of 109 images from which 44 patients which had coil element malfunction present. Five MRI radiographers were shown 249 images with and without real coil malfunction to assess their accuracy compared to the neural network in identifying the scanner fault. The neural network achieved an accuracy of 91.74% in identifying coil element malfunction in the unseen data. Radiographers tasked with identifying coil element malfunction had an average accuracy of 59.99%. In the same test case, the neural network outperformed all radiographers with an accuracy of 91.56%. This work demonstrates that neural networks trained with artificial data can successfully identify MRI scanner coil element malfunction in clinical images. The method provided better accuracy than MRI radiographers (technologists) at identifying coil element malfunction and highlights the potential utility of AI methods as an alternative to support traditional QA. Further, our methodology of training neural networks with simulated data could potentially identify other faults, allowing centers to produce robust fault detection systems with minimal data.

Graduate radiographers’ experience of learning MRI practice: A pilot study using constructivist grounded theory methodology

IntroductionTraditionally radiographers, specialising in MRI practice, would have first worked in a general imaging department, however due to the shortage of MRI radiographers within the UK, opportunities have now arisen for graduate radiographers to enter MRI practice directly. There are no requirements to undertake formal MRI qualifications or competency frameworks for UK MRI practitioners. Consequently, training is often conducted in house by other MRI practitioners and is not regulated or audited. The aim of this pilot study was to explore graduate radiographers’ experiences of learning MRI practice. MethodsA constructivist grounded theory methodology was implemented. Purposeful sampling was employed, and participants were recruited via social media. Participants (n3) had all entered MRI practice directly from graduation within the last 5 years and were currently working in the UK. Data was collected through semi-structured interviews, undertaken virtually and audio recorded. Analysis of the data was conducted using the constructivist grounded theory process, as set out by Charmaz and NVivo software was used to manage the data. ResultsFive core categories emerged from the data, 1) aspirations to enter MRI practice, 2) engaging in the learning process, 3) influences of the learning environment, 4) confidence in competence, 5) identification of the need for further learning. These core categories describe the stages of the participants' experience of learning MRI practice. ConclusionThe results of this pilot study demonstrate the pathway taken by graduate MRI radiographers through their MRI educational experience. Undergraduate placements, within MRI, influenced their choice to enter MRI practice, however it did not sufficiently prepare them and further education was necessary. All the participants were provided with a structure to their learning and assessment of competence was required, although the complexity of which varied between participants. Despite feeling competent to undertake MRI imaging examinations all participants sought out opportunities to engage with more formalised MRI radiographer education. Consequently, there may be a need for a standardised national training programme for MRI radiographers to ensure consistency of training and assessment. Further research with a larger participant size is required to consolidate these findings.

Development of lumbar spine MRI referrals vetting models using machine learning and deep learning algorithms: Comparison models vs healthcare professionals

IntroductionReferrals vetting is a necessary daily task to ensure the appropriateness of radiology referrals. Vetting requires extensive clinical knowledge and may challenge those responsible. This study aims to develop AI models to automate the vetting process and to compare their performance with healthcare professionals. Methods1020 lumbar spine MRI referrals were collected retrospectively from two Irish hospitals. Three expert MRI radiographers classified the referrals into indicated or not indicated for scanning based on iRefer guidelines. The reference label for each referral was assigned based on the majority voting. The corpus was divided into two datasets, one for the models' development with 920 referrals, and one included 100 referrals used as a held-out for the final comparison of the AI models versus national and international MRI radiographers. Three traditional models were developed: SVM, LR, RF, and two deep neural models, including CNN and Bi-LSTM. For the traditional models, four vectorisation techniques applied: BoW, bigrams, trigrams, and TF-IDF. A textual data augmentation technique was applied to investigate the influence of data augmentation on the models' performances. ResultsRF with BoW achieved the highest AUC reaching 0.99. CNN model outperformed Bi-LSTM with AUC = 0.98. With the augmented dataset, the performance significantly improved with an increase in F1 scores ranging from 1% to 7%. All models outperformed the national and international radiographers when compared on the hold-out dataset. ConclusionThe models assigned the referrals' appropriateness with higher accuracies than the national and international radiographers. Applying data augmentation significantly improved the models' performances. Implications for practiceThe outcomes suggest that the use of AI for checking referrals' eligibility could serve as a supporting tool to improve the referrals' management in radiology departments.

An investigation of lumbar spine magnetic resonance referrals in two Irish university teaching centres: Radiology clinical judgement versus iRefer guideline compliance

IntroductionWith the annual increase in medical imaging demand, the appropriateness of the lumbar spine magnetic resonance imaging LSMRI referrals is worldwide gaining attention. This study aims to determine the appropriateness of LSMRI referrals and compare radiology clinical decisions to iRefer compliance based solely on referral text content. MethodsReferral text was extracted from 1021 LSMRI referrals. Two review panels were recruited: three expert radiologists and three MRI radiographers. Radiologists classified cases as indicated or not indicated for scanning based on their clinical judgement. The radiographers classified based solely on iRefer guidelines. Majority voting for each case was applied to both review panels and reviewer agreement was tested using Kappa analysis. Logistic regression models were developed to identify medical disciplines associated with high rates of indicated referrals. Results21.7% and 11.9% of the cases were found not indicated for MRI for radiologists and radiographers, respectively. Radiology review identified 18% of the GPs referrals as not indicated and 17% in the radiographers’ review. Panel agreement was fair: Kappa values of 0.23 and0.26 for the radiologists and radiographers respectively. Neurosurgery was associated with the highest rate of indicated referrals across both review panels: oncology referrals raised the highest number of open comments. ConclusionThe study identified a lower number of not indicated referrals compared to previous research. Findings indicate the importance of both guidelines compliance and clinical judgement to optimise practice. Implications for practiceFindings in this study found that even when strict instructions were given to the MR radiographers to vet referrals using the iRefer guidelines, ambiguity within the guidelines resulted in variations in decision-making. This suggests that detailed protocols are required to support radiographers in the vetting process to ensure a standardised approach.

Radiographer Perspectives on current occurrence and management of claustrophobia in MRI

IntroductionMagnetic Resonance Imaging (MRI) is well known to be a source of anxiety for patients, commonly appearing as claustrophobia. One of the main reasons for this is due to the physical nature of the scanner itself. Despite technological improvements, there is lacking evidence on whether these improvements have resulted in a reduction in claustrophobia and anxiety in the clinical setting. Background anxiety associated with the current COVID-19 pandemic may also have shown an increase in prevalence. Therefore, the aim of this study was to survey MRI radiographers on their perspectives on the occurrence and management of claustrophobia in modern day clinical practice. MethodsFollowing ethical approval, an online survey was used to gather the opinions of MRI radiographers. This used closed ranking questions as well as open responses to gain insight into how this issue may be presenting in practice, preferences in management, and barriers to providing support. ResultsResponses provide an up-to-date view on how radiographers perceive both displays of anxiety and associated impacts on patient outcome, the considered sources of anxiety, the use and effectiveness of support strategies, barriers to providing this support, and views on how COVID-19 has impacted on practice. ConclusionThe study provides a current view from radiographers on their experience of claustrophobia in practice. It shows that this remains a regular part of practice within the modality. Therefore, for MRI radiographers managing this is an essential component of their role. Communication and interaction with the patient are recognised as important, although time is a barrier to always being able to provide patient centred care. Implications for practiceOngoing support is needed for both patients and radiographers to improve experience within MRI.

Cognisance of magnetic resonance imaging-induced vertigo and supported care: A study among a cohort of MRI radiographers in a country in West Africa

IntroductionMagnetic resonance imaging (MRI) can induce vertigo in patients undergoing such examinations. The severity of the vertigo is thought to increase with higher magnetic field strengths and could cause a patient to fall.The study assessed the awareness levels on MRI-induced vertigo among a cohort of MRI radiographers and their perspectives on the care that should be administered to patients post MRI examinations. MethodsThe study utilized a quantitative cross-sectional research design and a questionnaire. Out of a total of 40 MRI-radiographers identified nationwide, 31 participated in the study. Statistical Package for Social Sciences v.21.0 was used to analyse the data. ResultsMost participants (n = 21, 67.7%) were aware of MRI-induced vertigo. Many knew that patients (able and weaker) need to be assisted off the couch (n = 28, 90.3%) and escorted to the changing rooms post MRI examinations (n = 31,100%). There were statistically significant associations between the size of magnetic field strength used by the participants and their level of awareness about MRI-induced vertigo (r = 0.691, p = 0.003), appreciation of the needed support for patients post MRI examinations (r = 0.530, p = 0.041) and the frequency of occurrence of MRI-induced vertigo among their patients (r = 0.530, p = 0.001). ConclusionThe radiographers were mostly cognisant of MRI-induced vertigo and the supported care they were supposed to administer to their patients. The size of magnetic field strength used by the participants correlated with their level of awareness about MRI-induced vertigo and their appreciation of the needed support for patients post MRI examinations. Implication for practiceThe study highlights the need for a refresher training to expand the knowledge-base of a few of the radiographers who were not very cognisant about MRI-induced vertigo.

Multiparametric Magnetic Resonance Imaging for the Detection of Clinically Significant Prostate Cancer: What Urologists Need to Know. Part 1: Acquisition.

Acquiring multiparametric magnetic resonance images of the prostate is not a simple "push-button" approach. To show how image acquisition of prostate multiparametric Magnetic Resonance Imaging (mpMRI) can be optimized. Image protocols, magnetic field strength choice, and the use of receiver coils are discussed. In addition, patient preparation and the recognition, prevention, and mitigation of artifacts are evaluated. Based on expert prostate MRI technologists (MRI radiographers) opinion, the optimal protocol is reviewed, and potential artifacts are determined. The entire acquisition process is presented from initial patient preparation until the end of the imaging. The choice of the used equipment, pulse sequences, and prevention of patient- and imaging-related artifacts are presented. This will be shown in individual patients. Although the Prostate Imaging Reporting and Data System guidelines (2012 and 2016) describe minimal and optimal acquisition protocols for prostate mpMRI, these standards are not always met in daily practice. A major challenge in mpMRI is to obtain high image quality and reduce its variability for radiologic interpretations. A summary of evidence and guidelines for the acquisition of mpMRI of the prostate can set a basic guideline to reduce these variabilities. This article and an accompanying video can be used as a guide by MRI technologists (MRI radiographers) to improve their image acquisitions by optimizing protocols, magnetic field strength choice, and use of receiver coils. We also discuss patient preparation and the recognition, prevention, and mitigation of artifacts. In this first surgery-in-motion contribution, we will show how optimized image acquisition is performed to detect prostate cancer. Both MRI-dependent and patient related factors are discussed.

A Comparison of MRI Radiographers' Knowledge in Saudi Arabia and the Republic of Ireland in Relation to Image Quality Management, for Abdomen and Pelvic MRI Examinations

PurposeThe purpose of this article was to qualitatively compare current MRI radiographers’ knowledge from Saudi Arabia and the Republic of Ireland in relation to MR image quality for abdominal and pelvic MRI examinations. Methods and materialsSemistructured interviews were designed to investigate the professional role of radiographers towards image quality management, personal development in MRI, and training in relation to image quality improvement. Public, private, military, and academic hospitals in the Western region of the Kingdom of Saudi Arabia participated, as did a range of public and private Irish centres. Clinical specialist radiographers (CSRs)/supervisors, and MR radiographers working in MR completed the interviews. These were recorded, coded, and transcribed. ResultsSixty-one MR radiographers and CSRs/supervisors within 11 MRI departments in the Kingdom of Saudi Arabia and 11 MRI departments in the Republic of Ireland participated in this study. Three themes resulted by using a qualitative data analysis program called NVivo: (1) health care professional and the cultural attitudes with regards to the scope of professional roles, (2) factors affecting image quality, and (3) departmental policy. Participants' knowledge of image quality varied and challenges to achieving optimal quality levels were noted. Differences in clinical practice between countries were identified, as was the impact of clinical experience and levels of education. ConclusionDifferences in attitude and clinical practice between Saudi and Irish radiographers and CSRs/supervisors working in MRI departments were identified. There is a need for further training and subsequent assessment of professional skills, including developing postgraduate opportunities, particularly for Saudi radiographers, to support radiographers in the routine management of MR image quality.

Development of an inventory of biomedical imaging physics learning outcomes for MRI radiographers

IntroductionMRI is highly physics based yet no research-based inventory of physics learning outcomes specific to MRI radiographers was found in the literature. The purpose of this study was the development of such an inventory using a multi-stakeholder, multi-disciplinary approach (as advised by the WHO) and which would support a previously published competence profile. MethodsThe inventory was developed in two phases:Phase 1: Development of an initial version of the learning outcomes inventory required to be able to deliver the competences via an analysis of textbooks and literature and validated by a small (n = 3) expert advisory groupPhase 2: Final validation carried out via a bigger (n = 15) international group of subject matter experts (SMEs). Consensus was achieved via a dichotomous web-based questionnaire. ResultsAt 70% level of consensus the expert group validated an inventory of biomedical physics learning outcomes consisting of 281 knowledge and skill statements. It is subdivided into two sections: ‘fundamental’ physics learning outcomes which are generic to all competences and ‘additional’ physics learning outcomes specific to each individual competence. ConclusionThe process used is sufficiently generic to be easily adapted to the development of physics learning outcome inventories in other specialties of radiography and for other healthcare professions whose work involves highly technological medical devices. As a result of this study, the current MRI curriculum would need to be revised as it was not based on a formal systematic research process and many learning outcomes are in fact missing.

An international survey of MRI qualification and certification frameworks with an emphasis on identifying elements of good practice

The purpose of the study was to survey MRI qualification and certification frameworks in the major English-speaking countries (Australia, New Zealand, US, Canada, UK, Ireland) with the aim of identifying elements of good practice. The intention is to incorporate these elements in a national framework that could be used in supporting an MRI specialist register. The study was conducted using document analysis of MRI qualification and certification documents from these states with data triangulated through a web-based questionnaire amongst an expert group of MRI radiographers (n = 59) from the same states. Based on the results of the study, recommendations have been put forward for those countries that are in the process of developing such frameworks. The main recommendations include that a professional or regulatory body externally accredits MRI programmes and that learning outcomes be based on an MRI competence profile that addresses current and forecasted needs of the particular country. The MRI competence profile should encompass a novice-to expert continuum and be referenced directly to a national qualification framework. Ideally each level of expertise should be assessed and evidenced by a portfolio of CPD activities, including clinical and management case studies appropriate to that level.

Diagnostic performance of volume and limited oblique MRI of the anterior cruciate ligament compared to knee arthroscopy.

Many strategies have been used to improve the visualisation of the ACL including sagittal, coronal oblique sequences, and 3D volume imaging. Nevertheless, the ACL may not always be visualised. Two hundred and thirty-one consecutive patients (77 females; 154 males; average age 43.5, range 18 to 82 years; 205 with chronic, 20 acute, and 6 acute on chronic symptoms) underwent knee arthroscopy for mechanical symptoms within a week of MRI. After routine orthogonal sequences, if general MRI radiographers, with over four years experience, were not able to identify the presence of the ACL, then two 3D volume sequences and 2D limited sagittal oblique T1 sequences were performed. Patients requiring extra sequences, missed by the radiography technicians, were recalled. The MRI sequences were evaluated in a blinded fashion by three radiologists, and compared to the knee arthroscopy findings, with the normal ACL acting as internal controls. The radiography technicians performed additional ACL sequences in 63 patients (27%); of these, 10 patients had a partial and 12 patients had a complete ACL tear. Only 2 patients (0.6%) were recalled (one with a normal, and one with a full thickness ACL tear). The filmed ACL evaluation for complete tears and a normal ACL had a sensitivity of 100%, specificity of 97.1% and accuracy of 97.3%, slightly higher than evaluating on the monitor. Volume sequences had specificities and accuracies over 95%, with good intraobserver reliability (Kappa 0.859, 95% CI 0.705-1.0). Experienced radiographers identified most cases requiring supplementary MRI ACL sequences. An additional volume sequence was beneficial when filmed. Use of the monitor can offer some benefits. Limited oblique T1 sequence of the intercondylar notch was unreliable.

Optimizing a magnetic resonance care pathway: A strategy for radiography managers

PurposeThis study reports the optimization of a local MR care pathway. A search of the literature did not result in any studies regarding the optimization of MRI care pathways through a formal research process. Discussions with international MR radiographers indicated that such development is often carried out using informal methods that are highly dependent on local conditions, that are rarely reported in the public domain and the validities of which are therefore not open to scrutiny; in addition, care pathways need to be specific to local healthcare needs and culture. In this study, the authors propose a formal documented methodology for developing a local MRI care pathway based on the well-established nominal group technique. Methods and materialsA nominal group technique was conducted amongst a multi-professional panel. Results14 participants accepted the invitation to participate: an executive from the principal public general hospital, a manager from the national Ministry for Health, a service development manager from the allied healthcare professional sector, 2 senior physiotherapists, 3 nursing officers, 3 MRI radiographers, 2 medical physicists, 1 radiologist. Ten optimization related issues were identified and ranked in order of decreasing importance. Highest ranking scores were assigned to patient safety, education of referrers and use of quality criteria. The NGT method also brought forward novel themes in particular the need for a radiographer's technical report and the need for referrers to indicate pain levels of patients. ConclusionThe design of an MR care pathway was successfully optimized using a collaborative multi-stakeholder approach.

‘On their side’: Focus group findings regarding the role of MRI radiographers and patient care

IntroductionRadiographers have been described as caring and concerned healthcare professionals, who are attentive to the needs of their patients. However, this may not always be the case, and patient care may be overlooked at times. MethodsA qualitative descriptive study using a focus group was conducted with radiographers to determine their views on patient care. The focus group included 7 MRI radiographers of varying levels of experience. The data was analysed following a process of thematic analysis. Results7 themes emerged from analysis of the data. These were; a trade-off, a wide range of patients with a wide range of issues, from one extreme to the other, it's not that bad, getting the patient scanned, room for improvement, and on their side. ConclusionThe radiographers considered themselves on the patient's side, with the main objective to get the patient scanned, in some way, to aid in their diagnosis and treatment.

242 Quantitative measurements of occupational exposure to static magnetic stray fields from MRI scanners in clinical and research environments

ObjectivesWorkers’ exposure to static magnetic stray fields from MRI scanners was evaluated in a large cross-sectional study in The Netherlands. Factors determining the exposure to static magnetic fields (SMF) and...

Perception of health risks of electromagnetic fields by MRI radiographers and airport security officers compared to the general Dutch working population: a cross sectional analysis

BackgroundThe amount of exposure to electromagnetic fields (EMF) at work is mainly determined by an individual's occupation and may differ from exposure at home. It is, however, unknown how different occupational groups perceive possible adverse health effects of EMF.MethodsThree occupational groups, the general Dutch working population (n = 567), airport security officers who work with metal detectors (n = 106), and MRI radiographers who work with MRI (n = 193), were compared on perceived risk of and positive and negative feelings towards EMF in general and of different EMF sources, and health concerns by using analyses of variances. Data were collected via an internet survey.ResultsOverall, MRI radiographers had a lower perceived risk, felt less negative, and more positive towards EMF and different sources of EMF than the general working population and the security officers. For security officers, feeling more positive about EMF was not significantly related to perceived risk of EMF in general or EMF of domestic sources. Feeling positive about a source did not generalize to a lower perceived risk, while negative feelings were stronger related to perceived risk. MRI radiographers had fewer health concerns regarding EMF than the other two groups, although they considered it more likely that EMF could cause physical complaints.ConclusionsThese data show that although differences in occupation appear to be reflected in different perceptions of EMF, the level of occupational exposure to EMF as such does not predict the perceived health risk of EMF.

Radiographer led supplementary anterior cruciate ligament MRI sequences: Technical report

AimsTo compare different supplementary MRI sequences of the ACL to arthroscopy and determine the diagnostic performance of each sequence. To ascertain whether radiographers could identify patients requiring supplementary MRI sequences of anterior cruciate ligament (ACL) tears, without a supervising radiologist. MethodsThe study had ethical approval and two hundred and thirty one consecutive prospective MRI patients with mechanical knee symptoms (77 females, 154 males, of mean age 43.5, range 18–82 years) gave written informed consent. They then had a knee arthroscopy within seven days of the MRI. This was a pragmatic study to see if the six general MRI radiographers, each with over four years experience, could evaluate the ACL on routine orthogonal sequences (sagittal T1, Gradient Echo T2, Coronal STIR and axial fat suppressed dual echo). If they identified no ACL, then two 3D volume sequences (Dual Echo Steady State and Fast Low Angle Shot) and 2D limited sagittal oblique T1 sequences were also performed. Patients requiring extra sequences, missed by the radiographers, were recalled. The MRI sequences were independently evaluated in a blinded fashion by two consultant radiologists and a specialist radiology registrar and compared to the subsequent knee arthroscopy, as the gold standard, to determine the diagnostic performance statistics. ResultsThe cohort was on the knee arthroscopy weighting list and comprised 205 patients with chronic, 20 acute and 6 acute on chronic mechanical knee symptoms. There were no posterior cruciate, medial, or lateral collateral ligament tears at arthroscopy, used as the gold standard. The arthroscopy was normal and the radiographers correctly did not scan the extra sequence in 140 patients (72%) who then had normal arthroscopies. The radiographers did perform additional ACL sequences in 63 patients (27%). Of these, 10 patients had a partial and 12 complete ACL tears. Only two patients (0.9%) were recalled for additional sequences by the radiologist, and one ACL was normal and one had a full thickness tear at arthroscopy. The ACL evaluation for complete tears and a normal ACL on the volume sequences had a sensitivity of 100%, specificity of 97% and accuracy of 97%, excluding partial tears. Volume sequences including partial tears, had specificities and accuracies over 94%, with substantial interobserver agreement (Kappa 0.86, 95% CI 0.71–1.0). The limited oblique T1 sequence had sensitivities and negative predictive value of over 90%, but low specificity and positive predictive values and slight interobserver reliability (Kappa 0.42, 95% CI 0.2–0.6). ConclusionsFirstly, we have shown pragmatically that experienced radiographers identified almost all cases requiring supplementary MRI ACL sequences, without over scanning or needing supervision. Secondly, either volume sequence (DESS or FLASH) could be used as the supplementary sequence, to evaluate the ACL, but a limited oblique T1 sequence of the intercondylar notch cannot be recommended.

Denoising of Dynamic Contrast-Enhanced MR Images Using Dynamic Nonlocal Means

This paper presents a new algorithm for denoising dynamic contrast-enhanced (DCE) MR images. It is a novel variation on the nonlocal means (NLM) algorithm. The algorithm, called dynamic nonlocal means (DNLM), exploits the redundancy of information in the temporal sequence of images. Empirical evaluations of the performance of the DNLM algorithm relative to seven other denoising methods-simple Gaussian filtering, the original NLM algorithm, a trivial extension of NLM to include the temporal dimension, bilateral filtering, anisotropic diffusion filtering, wavelet adaptive multiscale products threshold, and traditional wavelet thresholding-are presented. The evaluations include quantitative evaluations using simulated data and real data (20 DCE-MRI data sets from routine clinical breast MRI examinations) as well as qualitative evaluations using the same real data (24 observers: 14 image/signal-processing specialists, 10 clinical breast MRI radiographers). The results of the quantitative evaluation using the simulated data show that the DNLM algorithm consistently yields the smallest MSE between the denoised image and its corresponding original noiseless version. The results of the quantitative evaluation using the real data provide evidence, at the alpha = 0.05 level of significance, that the DNLM algorithm yields the smallest MSE between the denoised image and its corresponding original noiseless version. The results of the qualitative evaluation provide evidence, at the alpha = 0.05 level of significance, that the DNLM algorithm performs visually better than all of the other algorithms. Collectively the qualitative and quantitative results suggest that the DNLM algorithm more effectively attenuates noise in DCE MR images than any of the other algorithms.

Investigation of the effects of magnetic fields on memory in occupationally exposed mri radiographers

aims: 1. compare memory ability between ct and mri radiographers using the rey auditory verbal learning test (ravlt) and between mri radiographers working with 1 and 1.5tesla (t) scanners. 2. investigate the change in memory ability (as measured by ravlt) with increasing time worked in mri.subjects: 11 ct and mri radiographers from four hospital sites were included. each worked exclusively in their modality. ravlt was administered once to each subject. results show no significant difference between mri and ct groups' scores. there were significantly lower scores in subjects who worked more than 5 years in mri and subjects who worked with 1.5t scanners.the results indicate that static magnetic fields may have a detrimental effect on memory ability. these results indicate the need for further research into the neuropsychological effects of the mri environment on occupationally exposed staff.