Magnetic Resonance Imaging Table Research Articles

Efficacy and cost-effectiveness of breast cancer (BC) screening in female survivors of childhood Hodgkin lymphoma (HL).

6593 Background: Female childhood HL survivors treated with ≥10 Gy of chest radiation are at high risk of developing BC. The Children’s Oncology Group (COG) guidelines recommend lifetime annual mammography (MAM) and breast Magnetic Resonance Imaging (MRI) starting 8y after chest radiation or age 25, whichever is later, and clinical breast examination (CBE) annually from puberty and semiannually from age 25. Initial model results suggest that CBE adds no survival benefit in this cohort. Digital breast tomosynthesis (DBT) is increasingly replacing digital MAM in clinical practice. Here, we present the efficacy and cost-effectiveness of COG’s imaging-based screening recommendations. Methods: Life-years (LYs), quality-adjusted LYs (QALYs), BC mortality, and costs (2017 U.S.$) were estimated from simulating the lifetimes of 5-million chest-irradiated 25y old HL survivors who underwent BC screening with each of the following strategies: annual digital MAM, MRI, MAM+MRI, annual DBT or DBT+MRI from age 25 onward. Treatment-related BC risk (in-situ and invasive) and non-BC mortality were estimated from female 5y HL survivors in the Childhood Cancer Survivor Study and from U.S. population rates. Test sensitivity was 70-74% for MAM (based on prior HL studies) and 89% for DBT and MRI (based on women at high risk of de novo BC). Costs and quality of life weights were obtained from medical literature. Results: For HL survivors with no screening, lifetime BC risk was 42.7% and BC mortality was 18.1%. BC risk and non-BC mortality were, respectively, 7.4- and 5.2-fold higher at age 50 in HL survivors relative to the general population. Screening at ages 25-74 had similar LY gain and BC mortality reduction compared to lifetime screening; hence, we focused on screening for ages 25-74. For all strategies screening provided LY gain of 0.34-0.47 and reduced BC mortality by 6.7-9.8% compared with no screening; incremental cost-effectiveness ratio (ICER), or cost per QALY gained, for MAM alone was $58,726 and for DBT alone was $62,989. ICER of adding MRI to MAM ($385,285) or to DBT ($513,358) indicated lower cost-effectiveness of supplemental MRI (Table). Conclusions: Annual screening at ages 25-74y in chest-irradiated HL survivors appears beneficial. Using $100K per QALY gained as cost-effectiveness threshold, annual MAM or DBT are more cost-effective, whereas adding MRI to MAM is less cost-effective.[Table: see text]

Remotely Actuated Needle Driving Device for MRI-Guided Percutaneous Interventions: Force and Accuracy Evaluation.

This paper presents a 2 degrees-of-freedom (DOF) remotely actuated needle driving device for Magnetic Resonance Imaging (MRI) guided pain injections. The device is evaluated in phantom studies under real-time MRI guidance. The force and torque asserted by the device on the 4-DOF base robot are measured. The needle driving device consists of a needle driver, a 1.2-meter long beaded chain transmission, an actuation box, a robot controller and a Graphical User Interface (GUI). The needle driver can fit within a typical MRI scanner bore and is remotely actuated at the end of the MRI table through a novel beaded chain transmission. The remote actuation mechanism significantly reduces the weight and size of the needle driver at the patient end as well as the artifacts introduced by the motors. The clinician can manually steer the needle by rotating the knobs on the actuation box or remotely through a software interface in the MRI console room. The force and torque resulting from the needle driver in various configurations both in static and dynamic status were measured and reported. An accuracy experiment in the MRI environment under real-time image feedback demonstrates a small mean targeting error (<; 1.5 mm) in a phantom study.

Robotically assisted long bone biopsy under MRI: cadaver study results.

We have designed and constructed an MR-safe robot made entirely of nonmetallic components with pneumatic actuators and optical encoders. The robot was developed to enable bone biopsies to be performed under magnetic resonance imaging (MRI) guidance in pediatric patients. The purpose of this study was to show the feasibility of using the robot for biopsy of the femur and tibia in a cadaver leg. Our long-term goal is to eliminate radiation exposure during bone biopsy procedures and provide more timely and accurate diagnosis for children with bone cancers and bone infections. The MR-safe robot was mounted on the MRI table. A cadaver leg was procured from an anatomy supply house and placed on the MRI table. All required hospital precautions for infection control were taken. A total of 10 biopsy targets were sampled using MRI guidance: five from the femur and five from the tibia. A handheld, commercially available battery-powered bone drill was used to facilitate drilling through the cortex. After the study, the leg was scanned with CT to better visualize and document the bone biopsy sites. Both the MRI and CT images were used to analyze the results. All of the targets were successfully reached with an average targeting accuracy of 1.43mm. A workflow analysis showed the average time for the first biopsy was 41min including robot setup time and 22min for each additional biopsy including the time for the repeat MRI scan used to confirm accurate targeting. The robot was shown to be MRI transparent, as no image quality degradation due to the use of the robot was detected. The results showed the feasibility of using an MR-safe robotic system to assist the interventional radiologist in performing precision bone biopsy under MRI guidance. Future work will include developing an MR-safe drill, improving the mounting of the robot and fixation of the leg, and moving toward first in child clinical trials.

Sacral Soft Tissue Deformations When Using a Prophylactic Multilayer Dressing and Positioning System: MRI Studies.

The sacrum is the most common location of pressure injuries (PIs) in bedridden patients. The purpose of this study was to measure the effect of specific pressure preventive devices on sacral skeletal muscle, subcutaneous fat, and skin tissue deformations. The sample comprised 3 healthy adults residing in a community setting in Tel Aviv, Israel. Descriptive, comparative design. Tissue thickness changes of 3 healthy adults were measured using magnetic resonance imaging (MRI) in weight-bearing sacral skin, subcutaneous fat, and muscle. Changes in tissue thickness were compared under the following conditions: (1) lying supine on a rigid surface (unpadded MRI table), (2) lying on a standard foam mattress, (3) lying on a mattress after application of a prophylactic multilayer dressing, and (4) lying on a standard foam mattress with a prophylactic multilayer dressing and a positioning system. One-way analysis of variance and post hoc Tukey-Kramer multiple pairwise comparisons were used to compare outcomes. The mattress, the prophylactic multilayer dressing, and the turning and positioning device when applied together resulted in significantly lower deformation levels of each of the soft tissue layers (ie, skin, subcutaneous fat, and muscle separately) as well as of the total soft tissue bulk, with respect to the rigid MRI table (P < .05). Study findings suggest that a combination of preventive interventions may reduce the risk of developing a sacral PI.

Geometric accuracy of the MR imaging techniques in the presence of motion

Magnetic Resonance Imaging (MRI) is increasingly being used for improving tumor delineation and tumor tracking in the presence of respiratory motion. The purpose of this work is to design and build an MR compatible motion platform and to use it for evaluating the geometric accuracy of MR imaging techniques during respiratory motion. The motion platform presented in this work is composed of a mobile base made up of a flat plate and four wheels. The mobile base is attached from one end and through a rigid rod to a synchrony motion table by Accuray® placed at the end of the MRI table and from the other end to an elastic rod. The geometric accuracy was measured by placing a control point‐based phantom on top of the mobile base.In‐house software module was used to automatically assess the geometric distortion. The blurring artifact was also assessed by measuring the Full Width Half Maximum (FWHM) of each control point. Our results were assessed for 50, 100, and 150 mm radial distances, with a mean geometric distortion during the superior–inferior motion of 0.27, 0.41, and 0.55 mm, respectively. Adding the anterior–posterior motion, the mean geometric distortions increased to 0.4, 0.6, and 0.8 mm. Blurring was observed during motion causing an increase in the FWHM of ≈30%. The platform presented in this work provides a valuable tool for the assessment of the geometric accuracy and blurring artifact for MR during motion. Although the main objective was to test the spatial accuracy of an MR system during motion, the modular aspect of the presented platform enables the use of any commercially available phantom for a full quality control of the MR system during motion.

Can Ultrasound Accurately Assess Ischiofemoral Space Dimensions? A Validation Study

BackgroundIschiofemoral impingement is a potential cause of hip and buttock pain. It is evaluated commonly with magnetic resonance imaging (MRI). To our knowledge, no study previously has evaluated the ability of ultrasound to measure the ischiofemoral space (IFS) dimensions reliably. ObjectiveTo determine whether ultrasound could accurately measure the IFS dimensions when compared with the gold standard imaging modality of MRI. DesignA methods comparison study. SettingSports medicine center within a tertiary-care institution. ParticipantsA total of 5 male and 5 female asymptomatic adult subjects (age mean = 29.2 years, range = 23-35 years; body mass index mean = 23.5, range = 19.5-26.6) were recruited to participate in the study. MethodsSubjects were secured in a prone position on a MRI table with their hips in a neutral position. Their IFS dimensions were then acquired in a randomized order using diagnostic ultrasound and MRI. Main Outcome MeasurementsThe main outcome measurements were the IFS dimensions acquired with ultrasound and MRI. ResultsThe mean IFS dimensions measured with ultrasound was 29.5 mm (standard deviation [SD] 4.99 mm, standard error mean 1.12 mm), whereas those obtained with MRI were 28.25 mm (SD 5.91 mm, standard error mean 1.32 mm). The mean difference between the ultrasound and MRI measurements was 1.25 mm, which was not statistically significant (SD 3.71 mm, standard error mean 3.71 mm, 95% confidence interval −0.49 mm to 2.98 mm, t19 = 1.506, P = .15). The Bland-Altman analysis indicated that the 95% limits of agreement between the 2 measurement was −6.0 to 8.5 mm, indicating that there was no systematic bias between the ultrasound and MRI measurements. ConclusionsOur findings suggest that the IFS measurements obtained with ultrasound are very similar to those obtained with MRI. Therefore, when evaluating individuals with suspected ischiofemoral impingement, one could consider using ultrasound to measure their IFS dimensions. Level of EvidenceIII

A child with difficult airway for magnetic resonance imaging: Is dexmedetomidine useful?

Sir, Magnetic resonance imaging (MRI) poses challenges to the anaesthesiologists in providing adequate sedation without compromising the patient's airway or haemodynamics and ensuring rapid recovery. The additional challenges posed by remote locations make the highest level of vigilance essential during MRI study. Dexmedetomidine has been used as a sole agent or in combination with other drugs for sedation in radiology set up.[1,2] Seven-month-old male child, weighing 7 kg, with history of swelling in the floor of mouth was referred to our hospital for MRI scanning. On detailed history, the swelling was present since birth and was increasing in size. There was no feeding difficulty but sleep was disturbed. On examination, a 4 cm × 4 cm swelling completely pushing tongue to one side was seen [Figure 1a]. Rest of the clinical examination was normal. Need for Intensive Care Unit stay was explained to relatives. Equipment for difficult airway was kept ready. Plan was to sedate the child in the preparation room. All monitors (electrocardiogram [ECG], pulse oximetry, end-tidal CO2 [ETCO2]) were attached. In the MRI room, MRI-compatible anaesthesia workstation and multiparameter monitor were kept ready. Intravenous (i.v.) cannula was secured and glycopyrrolate 0.05 mg administered. Dexmedetomidine 7 µg was administered over 10 min as infusion. Sedation was assessed using Ramsay sedation score. Ketamine 10 mg i.v. was given as supplemental sedation after completion of dexmedetomidine infusion to achieve Ramsay sedation score of 6. Then patient was transferred to MRI table and all monitors (ECG, pulse oximetry, ETCO2) were attached. Stable capnogram was established before proceeding to scan. Oxygen supplementation was given with nasal cannula (2 L/min). Continuous monitoring of vital parameters was done. Procedure lasted for 45 min. No episode of apnoea, desaturation and bradycardia was noted. The child was immobile throughout the MRI scanning. After the procedure, the patient was transferred to recovery room and monitored till recovery. MRI imaging confirmed the extent of swelling, and the tumour was compressing trachea [Figure 1b]. Figure 1 (a) Large tumour in oral cavity pushing tongue; (b) magnetic resonance imaging scan showing tumour compressing trachea Dexmedetomidine is useful for paediatric sedation in many clinical situations. It is associated with rapid onset and offset and a natural, sleep-like state with minimal effect on respiration. During MRI, the patient needs to be still for good-quality image. Paediatric patients need sedation and sometimes general anaesthesia for MRI. Many drugs such as chloral hydrate, phenobarbital, ketamine, midazolam and propofol have been used in MRI setting.[1] Dexmedetomidine alone has been used for sedation in MRI suite with more than 90% success.[3] These studies noted no apnoea or respiratory depression with high dose of dexmedetomidine. As dexmedetomidine single dose gives adequate sedation for 45–60 min, MRI can be done without need for supplemental sedation. In a study comparing dexmedetomidine plus single bolus dose of midazolam and propofol, dexmedetomidine provided satisfactory condition for MRI and respiratory incidences were similar to the propofol group.[2] In another study of dexmedetomidine versus midazolam,[4] the quality of MRI was better with dexmedetomidine and need for rescue medication was less. Comparison of intramuscular (i.m.) ketamine, i.m. dexmedetomidine, and dexmedetomidine–ketamine combination showed that the combination was superior with regard to onset, haemodynamic and respiratory stability.[5] Quality of MRI and radiologist satisfaction regarding image quality was better in dexmedetomidine–ketamine combination group. The combination of dexmedetomidine and ketamine is useful as the risk of apnoea is minimal with this combination. In a case series of trisomy 21 patients for MRI, dexmedetomidine–ketamine combination provided effective sedation without haemodynamic and respiratory compromise.[6] We conclude that dexmedetomidine and ketamine combination is an option to manage children with difficult airway for sedation in MRI suite.

Low Cost Magnetic Resonance Imaging-Compatible Stepper Exercise Device for Use in Cardiac Stress Tests.

Cardiovascular disease is the leading cause of death worldwide. Many cardiovascular diseases are better diagnosed during a cardiac stress test. Current approaches include either exercise or pharmacological stress echocardiography and pharmacological stress magnetic resonance imaging (MRI). MRI is the most accurate noninvasive method of assessing cardiac function. Currently there are very few exercise devices that allow collection of cardiovascular MRI data during exercise. We developed a low-cost exercise device that utilizes adjustable weight resistance and is compatible with magnetic resonance (MR) imaging. It is equipped with electronics that measure power output. Our device allows subjects to exercise with a leg-stepping motion while their torso is in the MR imager. The device is easy to mount on the MRI table and can be adjusted for different body sizes. Pilot tests were conducted with 5 healthy subjects (3 male and 2 female, 29.2 ± 3.9 yr old) showing significant exercise-induced changes in heart rate (+42%), cardiac output (+40%) and mean pulmonary artery (PA) flow (+%49) post exercise. These data demonstrate that our MR compatible stepper exercise device successfully generated a hemodynamically stressed state while allowing for high quality imaging. The adjustable weight resistance allows exercise stress testing of subjects with variable exercise capacities. This low-cost device has the potential to be used in a variety of pathologies that require a cardiac stress test for diagnosis and assessment of disease progression.

A pilot study of regional perfusion and oxygenation in calf muscles of individuals with diabetes with a noninvasive measure

To assess alterations in the regional perfusion and oxygenation of the calf muscles in individuals with diabetes. Age-matched individuals with (n = 5) and without diabetes (n = 6) were investigated. Skeletal muscle perfusion, oxygen extraction fraction, and oxygen consumption rate were measured by newly developed noncontrast magnetic resonance imaging (MRI) techniques. The subjects lay supine on the MRI table with their foot firmly strapped to a custom-built isometric exercise device. The measurements were performed at rest and during an isometric plantar flexion muscle contraction. Individuals without diabetes had up to a 10-fold increase in muscle perfusion, 25% elevation in muscle oxygen extraction fraction, and a 12-fold increase in oxygen consumption rate in the calf during the plantar flexion isometric contraction. In patients with diabetes, the increases in these parameters were only up to sixfold, 2%, and sixfold, respectively. Exercise oxygen consumption rate was inversely associated with blood HbA1c levels (r(2) = .91). This is the first study to quantify regional skeletal muscle oxygenation in patients with diabetes using noncontrast MRI and warrants additional study. Attenuation of perfusion and oxygenation during exercise may have implications for understanding diabetic complications in the lower extremities.

Pinpointing Moments of High Anxiety During an MRI Examination

Magnetic Resonance Imaging (MRI) is associated with high levels of anxiety in many patients which may interfere with image quality and increase examination time. In order to develop effective intervention strategies that decrease anxiety, more insights into moments of high anxiety during a MRI examination are necessary. The present study aimed at obtaining insights into anxiety levels and moments of high anxiety during a Magnetic Resonance Imaging examination. The study included 67 patients, of whom 52 (77.6 %) were categorized as highly anxious. Stress and anxiety were measured continuously throughout the entire duration of the MRI examination by monitoring the heart rate. An increase in heart rate during the scan was taken as an indication for higher stress and anxiety. In addition to measuring stress and anxiety objectively, anxiety was assessed subjectively before and after the procedure by means of self-report questionnaires. The self-report data indicate that patients were highly anxious before the MRI examination. Moreover, the electrophysiological data clearly show that anxiety levels were highest at the beginning of the procedure, i.e., when the MRI table moved into the scanner, and then decreased over the course of the examination. Furthermore, the findings show that while subjectively measured anxiety was higher in patients who had taken anxiolytics prior to the MRI examination than in patients who had not taken any anxiolytics, objectively measured anxiety during the scan was equally high in both groups. The present study provides detailed insights into the anxiety levels during an MRI examination, which may aid in developing effective anxiety-reduction strategies. Additionally, the findings show that measuring anxiety continuously throughout the entire examination using electrophysiology in combination with measuring anxiety subjectively prior to and after the scan provides a more complete assessment of MRI-related anxiety.

Paraplegia Caused By Posture During MRI in a Patient With Cervical Disk Herniation

A 48-year-old man presented with numbness in the lower left extremity of 4 months' duration. One month earlier, he presented to an orthopedic clinic and magnetic resonance imaging (MRI) revealed cervical disk herniation. Because the pain did not subside, he visited the clinic again and MRI was performed. His neck was slightly extended and fixed to the headrest of the MRI instrument. Because of the posture of his cervical spine, he suffered severe pain in the scapular region during the MRI. After 15 minutes the pain was unbearable and the MRI examination was aborted. As the patient tried to descend from the MRI table, he was unable to move his bilateral lower extremities. No muscle contraction was observed in his lower limbs. Following MRI with flexion posture of the cervical spine, he was diagnosed with paraplegia caused by cervical disk herniation. Emergency surgery consisting of anterior decompression and fusion was performed. The patient showed good neurological recovery. Three weeks postoperatively, the patient could walk without assistance and he was discharged. The extension posture of the cervical spine during MRI was considered to be the cause of acute paraplegia in this patient. Care should be taken with the posture of the cervical spine, when performing MRI in patients with cervical disk herniation. Extended posture of the cervical spine during MRI may lead to acute neurological deterioration.

Biventricular non-compaction and giant left atrial appendage

A young man with unexplained symptoms of breathlessness presented for cardiovascular magnetic resonance imaging (MRI) following a non-contrast echocardiogram that had suggested mild impairment of function. As he was being placed on the MRI table, the technologist spontaneously commented upon his unusual facial features with the words ‘he's a funny looking kid’. Cardiac MRI revealed …

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Propofol anaesthesia in spontaneously breathing paediatric patients during magnetic resonance imaging.

The aim of this study was to evaluate the use of propofol to induce and maintain anaesthesia in spontaneously breathing paediatric patients (age 2 weeks-11 years) during Magnetic Resonance Imaging (MRI) of the CNS. All patients were spontaneously breathing, without intubation, and received supplemental O2. Pulse rate, blood pressure (BP), electrocardiogram and EtCO2 were recorded in all patients, and in 38 subjects SpO2 was also monitored. Patients were divided in 2 groups according to their body weights: Group A (n = 34, bwt < or = 10 kg), and Group B (n = 48, bwt > 10 kg). Dosage of propofol during the time of induction (from insertion of the i.v. cannula to positioning on the MRI table) was significantly higher in smaller children (Group A; 5.4 +/- 2.2 (SD) mg/kg) as compared to children with bwt above 10 kg (Group B; 3.7 +/- 1.6 mg/kg). Propofol dosage for maintenance of anaesthesia was significantly higher in smaller children (Group A: 10.1 +/- 5.7 vs Group B: 7.1 +/- 3.0 mgkg-1 h-1, P = 0.003). During the time of induction, transient episodes of reduced BP (< or = 20%) occurred in 6 patients in Group A and 2 patients in Group B. During anaesthesia in Group B there was 1 episode of oxygen desaturation (95%), and 3 episodes of short and mild increases of EtCO2(< or = 52 mmHg). No other side effects occurred in any patient. MRI studies were successfully completed, only 3 sequences (Group A) had to be restarted. Propofol can be safely used for total intravenous anaesthesia in children undergoing MRI.