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Magnetic Resonance Imaging Physics
Published in Debbie Peet, Emma Chung, Practical Medical Physics, 2021
Moving around close to the static field effectively results in exposure to time-varying magnetic fields. Some individuals may experience acute effects such as vertigo, dizziness or nausea when moving close to the scanner. Slow movement rather than fast movement of the head is advised to minimise the risk of acute biological effects, particularly when positioning a test object inside of the magnet bore. During scanning, rapidly changing magnetic field gradients are used to encode spatial position in the image, which also can result in exposure to time-varying magnetic fields if an individual is inside the MR Environment. Time-varying magnetic fields can induce electric currents that could be sufficiently large in tissues to interfere with the normal function of nerve cells, generating peripheral nerve stimulation (PNS) and direct muscle stimulation. While potentially uncomfortable during the scan, the effects have not been shown to be long lasting.
Clinical Applications and Protocols of Single Photon Emission Computed Tomography
Published in Bhagwat D. Ahluwalia, Tomographic Methods in Nuclear Medicine: Physical Principles, Instruments, and Clinical Applications, 2020
Stress imaging is started after injection of approximately 2 to 3 mCi of 201T1Cl. Approximately 4% of the injected 201T1 is extracted from the blood. The uptake of 201T1 by the myocardium reflects mainly the blood supply to the heart. Data acquisition postinjection with a single-head large-field-of-view camera is generally performed over 180° from a right anterior oblique (RAO) to a left posterior oblique (LPO) position. A total acquisition time of approximately 20 min is considered adequate to scan most patients. It has also been observed that the patient’s discomfort is reasonably low for these scan times. On the other hand, problems associated with 201T1 redistribution, washout, and uptake arise with an increase in scan time.
Knowledge Area 3: Surgical Procedures
Published in Rekha Wuntakal, Ziena Abdullah, Tony Hollingworth, Get Through MRCOG Part 1, 2020
Rekha Wuntakal, Ziena Abdullah, Tony Hollingworth
Randomized controlled trials have shown that the incidence of incomplete procedure or retained products of conception can be reduced with appropriate use of transvaginal ultrasound in theatre once the surgery is accomplished. However, the limitations include the need for a high-resolution ultrasound scan machine and the expertise to use the scan machine.Further readingRoyal College of Obstetricians and Gynaecologists (RCOG). Consent Advice No. 10. Surgical Management of Miscarriage and Removal of Persistent Placental or Fetal Remains (Consent Advice No. 10—Joint with AEPU). January 2018.
Pinch points in the consultation – and how to avoid them
Published in Education for Primary Care, 2023
Other cues that the dance is drifting include negative, closed body language; the patient not following the doctor’s lead as they move through the stages of the consultation and repeated rejection of the doctor’s suggestions. The dance will also be threatened by more challenging consultations, particularly where doctor and patient may not agree. Examples include the use of strong pain killers, the prescription of antibiotics or the value of an MRI scan. Often the doctor will know in advance that a disagreement is probably on the cards – for instance where a patient starts the consultation with a demand for a scan: ‘I won’t keep you long, doctor, I just need a scan for my back’. The doctor can anticipate a tricky passage to come in the dance where they may have to state that a scan will not be helpful. Rather than carrying on as normal and hoping for the best, the doctor can prepare for this challenge by looking for common ground to ensure as much agreement as possible before the dance gets more difficult. In the example of the scan, the doctor can agree that it is very reasonable to want to find out what is happening and that it is fair to ask for a scan, that it is unpleasant being in pain, and so on. By finding this common ground the dance is kept in hold and the patient is more likely to listen and understand if the doctor has to say to them that actually a scan won’t be helpful in their case.
Ultrasonic ocular dimensions and anthropometry in normal and myopic eyes: a case-control study
Published in Expert Review of Ophthalmology, 2022
Faosat Olayiwola Jinadu, Iskilu Adekunle Jolaoso, Modupe Balogun, Tawaqualit Abimbola Ottun, Ufuoma Oluwaseyi Olumodeji, Ayokunle Moses Olumodeji
There was consistency between ocular biometric measurements obtained by B-mode and A-mode ultrasonography in this study (Table 7). This is in support of the growing belief in the accuracy of B-scan in the assessment of ocular biometry [18,28,29]. Previous studies by Yang et al. [21], Olivier et al. [28], and Abu et al. [29] on myopic eyes with cataracts found no significant difference in ocular axial biometric measurement (AL) using A-mode, B-mode ocular scan and IOL master in individuals with AL > 26 mm. They also suggested that the accuracy and reproducibility of AL measurement using B-mode is better than contact A-mode scanning. Gonzalez et al. [18] in their study on highly myopic eyes further opined that B-scan provides a more accurate AL measurement in calculating intraocular lens power than the A-scan because of its ability to locate the macula which commonly bulges to form staphyloma (and thus an increase in ocular axial length) in highly myopic eyes. The ability is absent in A-scan and as such provides a false shorter AL measurement. These suggest that B-scan is a suitable alternative to the A-scan in the measurement of ocular axial parameters.
Clinical Features of Endogenous Endophthalmitis Secondary to Minimally Invasive Upper Urinary Tract Calculus Removal
Published in Ocular Immunology and Inflammation, 2022
Bingsheng Lou, Yi Sun, Jialiu Lin, Zhaohui Yuan, Liwen He, Chongde Long, Xiaofeng Lin
The initial BCVA ranged from no light perception (NLP) to 0.8 (Table 1). Overall, the infection manifestation was moresevere in the posterior segment than in the anterior segment. Hypopyon was only found in 3 patients (3 eyes) (Figure 1, Table 1). All eyes presented as vitritis and fluffy yellow-white retinal exudates. Retinal exudates located in the posterior polar region (4 eyes) were isolated or bead-like, while exudates at inferior quadrant retina (6 eyes) were bead-like or diffuse (Figure 2).Retinal exudates showed hypofluorescence under fundus fluorescein angiography (FFA) (Figure 3a,b), surrounding hyperfluorescence due to capillary leakage, and demonstrated the hyper-reflectivity lesions with optical coherence tomography (OCT) (Figure 3c,d). Besides, mild papilledema, retinal vessel dilatation and tortuousness was also noted, while no hemorrhage or vascular occlusion was found. B scan ultrasound usually showed echogenic spots nearby the retina in eyes with severe vitreous opacity (Figure 3e,f). Retinal detachment was detected in 1 eye by B scan ultrasound.