Number Of Magnetic Resonance Imaging Scans Research Articles

Direct Temperature Measurements of Cardiac Stent during MRI Examinations

Nowadays, Magnetic Resonance Imaging (MRI) is considered the gold standard for imaging the brain, spinal cord, musculoskeletal system, head and neck, and complex congenital heart malformations; consequentially, the number of MRI scans in patients with implantable electronic devices has simultaneously increased. During the entire length of the MRI exam, patients are exposed to electromagnetic fields with different characteristics (static, low frequency, radiofrequency fields), which are related to different risks. The scarce available literature about MRI-induced heating on cardiac stents suggests that excessive temperature rise occurs only in unfavorable cases. Ideally, RF safety assessment could be performed during the anamnestic process, but this simulation process’s results are too slow to be performed before patient MRI examination. In this context, we developed a dedicated measurement set-up by focusing our target on the measurement of the heating of a cardiac stent during an MRI examination. Results for the temperature rise trend along the entire stent length during a clinical MRI protocol are shown together with the local Specific Absorption Rate (SAR) values and cumulative equivalent minutes at 43 °C (CEM43°C), in order to ensure the safety of patients with MR-conditional devices, also with a view to not inappropriately preclude their access to MRI scans. The obtained results show that the maximum temperature rise (4.12 °C) is within the limit of 5 °C stated in the stent manual for 15 min of continued scanning with the specific conditions. The maximum temperature rise was in correspondence with the stent tips and calculated SAR confirms the fact that two hotspots are present near the tips of the stent. Finally, the calculated CEM43°C remained well below the proposed threshold for muscle tissue.

Value of screening and follow-up brain MRI scans in patients with metastatic melanoma.

BackgroundNovel treatments make long‐term survival possible for subsets of patients with melanoma brain metastases. Brain magnetic resonance imaging (MRI) may aid in early detection of brain metastases and inform treatment decisions. This study aimed to determine the impact of screening MRI scans in patients with metastatic melanoma and follow‐up MRI scans in patients with melanoma brain metastases.MethodsThis retrospective cohort study included patients diagnosed with metastatic melanoma or melanoma brain metastases between June 2015 and January 2018. The impact of screening MRI scans was evaluated in the first 2 years after metastatic melanoma diagnosis. The impact of follow‐up MRI scans was examined in the first year after brain metastases diagnosis. The number of MRI scans, scan indications, scan outcomes, and changes in treatment strategy were analyzed.ResultsIn total, 116 patients had no brain metastases at the time of the metastatic melanoma diagnosis. Twenty‐eight of these patients (24%) were subsequently diagnosed with brain metastases. Screening MRI scans detected the brain metastases in 11/28 patients (39%), of which 8 were asymptomatic at diagnosis. In the 96 patients with melanoma brain metastases, treatment strategy changed after 75/168 follow‐up MRI scans (45%). In patients treated with immune checkpoint inhibitors, the number of treatment changes after follow‐up MRI scans was lower when patients had been treated longer.Conclusion(s)Screening MRI scans aid in early detection of melanoma brain metastases, and follow‐up MRI scans inform treatment strategy. In patients with brain metastases responding to immune checkpoint inhibitors, treatment changes were less frequently observed after follow‐up MRI scans. These results can inform the development of brain imaging protocols for patients with immune checkpoint inhibitor sensitive tumors.

Long‐interval T2‐weighted subtraction magnetic resonance imaging: A powerful new outcome measure in multiple sclerosis trials

To compare long-interval T2-weighted subtraction (T2w-Sub) imaging with monthly gadolinium-enhanced T1-weighted (Gd-T1w) imaging for (1) detection of active lesions, (2) assessment of treatment efficacy, and (3) statistical power, in a multiple sclerosis (MS), phase 2, clinical trial setting. Magnetic resonance imaging (MRI) data over 9 months from 120 patients (61 treatment, 59 placebo) from the oral temsirolimus trial were used. T2w-Sub images were scored for active lesions, independent of the original reading of the monthly Gd-T1w images. Treatment efficacy was evaluated using the nonparametric Mann-Whitney U test, and parametric negative binomial (NB)-regression and power calculations were conducted. Datasets from 116 patients (58 treatment, 58 placebo) were evaluated. The mean number of T2w-Sub lesions in the treatment group was 3.0 (+/-4.6) versus 5.9 (+/-8.8) for placebo; the mean cumulative number of new Gd-T1w lesions in the treatment group was 5.5(+/-9.1) versus 9.1(+/-17.2) for placebo. T2w-Sub imaging showed increased power to assess treatment efficacy compared with Gd-T1w imaging, when evaluated by Mann-Whitney U test (p = 0.017 vs p = 0.177), or NB-regression without (p = 0.011 vs p = 0.092) or with baseline adjustment (p < 0.001 vs p = 0.002). Depending on the magnitude of the simulated treatment effect, sample size calculations showed reductions of 22 to 34% in the number of patients (translating into reductions of 81-83% in the number of MRI scans) needed to detect a significant treatment effect in favor of T2w-Sub imaging. Compared with monthly Gd-T1w imaging, long-interval T2w-Sub MRI exhibited increased power to assess treatment efficacy, and could greatly increase the cost-effectiveness of phase 2 MS trials by limiting the number of patients, contrast injections, and MRI scans needed.

Response of patients to the introduction of a private Magnetic Resonance Imaging service in Western Jamaica.

Background:Magnetic Resonance Imaging (MRI) is one of today's fastest growing imaging modalities, spurred in part by rapid advances in technology and important new applications in patient care. It was introduced in Western Jamaica in March 2005 at a non-hospital-based facility called North Coast Imaging MRI Service.Aims:The study examined the socio-demographics, accessibility and affordability of the services to patients.Materials and Method:A random sample of 100 patients was used and the research instrument was a questionnaire. The study was conducted between August and November 2008.Results:The findings of the study showed that majority of the respondents lived in rural areas and were within the age group 30 - 59 years. One-half of the respondents resided in St. James, were employed; earned more than US$1,351.00 per month and could afford the cost of the MRI procedure. More than one half of the respondents indicated that it took 15 – 30 minutes to be examined after arrival at the Centre; most (81%) of the respondents indicated that the MRI procedure was adequately explained, and 99% indicated that questions about the procedure were satisfactorily answered. The MRI Scans performed at the North Coast Imaging MRI Service showed an increase of 157.49% in 2006 when compared with 2005, and 70.90% in 2007 when compared with 2006. Our findings suggest that the number of MRI scans done at the North Coast Imaging MRI Service is likely to increase.Conclusion:Although most of the respondents were able to afford the procedure there are concerns about persons in the lower socio-economic group who are unable to afford expensive diagnostic imaging tests such as MRI scans. There is an urgent need for government-owned hospital-based MRI Units in Jamaica to offer lower cost MRI scans to the public.

Individualizing the interval between neoadjuvant chemoradiation with uracil-tegafur (UFT) and total mesorectal excision in magnetic resonance imaging (MRI) defined poor-risk rectal cancer

14557 Background: The importance of achieving negative circumferential resection margins (CRM) for patients (pts) with MRI - defined poor - risk rectal cancer (PRRC) has led to an increase in the use of pre-operative chemoradiotherapy (CRT) employing long fractionation schedules, usually with an interval of 4 to 6 weeks before surgery. We report our experience of using serial MRI post CRT to optimise the timing of total mesorectal excision (TME) surgery at maximal radiological response for each pt. Methods: Data was collected prospectively from 4/03 to 10/06 on toxicity and response for 50 consecutive patients ( 36 male; median age 64 years, range 39 - 76 years), 47 with biopsy - proven PRRC by MRI criteria (threatened / definite CRM involvement, T3 &gt; 5mm into perirectal fat, T4 tumours, and / or multiple nodes) and 3 pts with localised recurrence after previous anterior resection. Pts received 2 phase, conformal external beam radiotherapy ( 45 - 50.4 Gy / 25 - 28 fractions / 5 weeks), concurrently with their choice of either oral UFT (n = 44, 88%), 240mg/m2/d d 1 - 28 with Leucovorin (LV) 90mg/d or iv bolus 5 FU (n= 6) 300mg/m2 d 1,8,15,22,29 with LV 20 mg/m2). Clinical re-assessment q 2 wkly from 4 weeks post CRT, with serial MRIs 4-weekly, from 6 wks. Results: 48 pts (96%) completed CRT, worst toxicity, diarrhoea Grade 3, 6%. Mean number of MRI scans per pt post CRT 1.48, with response seen in 46 pts (92%), of whom 43 (86%) underwent resection, 27 (63%) of which were performed laparoscopically. Median time to surgery was 11 weeks (range 8 to 15 wks). 37pts (86% of those undergoing surgery) achieved R0 resection, mean CRM 6.1mm, mean no. of identifiable lymph nodes 6.4, most frequent pathology ypT3 pN0 26%, pCR 16%, Tmic, 21%. Surgical morbidities included small bowel adhesions requiring laparotomy 8%, infection/abscess 14%. Post-operative mortality 5%. 1 PRRC pt developed liver metastases prior to surgery. Conclusions: CRT with UFT/LV is well tolerated and effective in achieving substantial tumour regression pre-operatively for PRRC. The optimal timing of surgery post CRT at maximal response can be documented with serial MRI, resulting in a high rate of R0 resections. Laparoscopic TME is feasible in this group of pts. [Table: see text]