Name: troubleshooting focus image acquisition: patient positioning, transducer manipulation, and image optimization
Uploaded: 2023-03-03T14:25:00.000+00:00
Duration: 6 min 50 s
Description: Watch this Scientific Journal Video about Troubleshooting FoCUS Image Acquisition: Patient Positioning, Transducer Manipulation, and Image Optimization at JoVE.com

We would like to thank the University of Michigan Department of Anesthesia, Max Harry Weil Institute for Critical Care Research and Innovation, and Katelyn Murphy for their administrative and graphic design support.

This material is the authors&#39; original work, which has not been previously published elsewhere. The protocol described is for clinical use and not research purposes. De-identified images were obtained from a volunteer model in a non-clinical environment. The authors did not seek a formal &#34;Not Regulated&#34; determination from the IRB in accordance with institutional policy, as the activity falls outside of the Common Rule and FDA definitions of human subject research.
1. The transducer
<ol>
	<li>Use the phased array transducer. This is a 4-12 MHz transducer that penetrates deep into the thoracic space, due to its low frequency compared to other ultrasound transducers.
	<ol>
		<li>Select the phased array transducer using the Exam button on the machine and selecting the cardiac exam or equivalent available exam.</li>
	</ol>
	</li>
	<li>Practice with transducers from various vendors to gain experience and refine one&#39;s cognitive skill set for transducer manipulation.</li>
	<li>Practice transducer manipulation with both hands to develop ambidexterity, which may be required when working in limited clinical environments.</li>
	<li>Anchor the dominant hand while holding the ultrasound transducer on the patient, with the fat pad of the medial aspect of the hand. 
	&#8203;NOTE: This provides additional stability and reduces error caused by large movements. Holding the transducer by the base, without anchoring, results in unintended movements, preventing the ability to maintain the image axis and orientation.</li>
	<li>Use two hands for transducer manipulation to improve the ultra-fine adjustments often required for optimal views. Place the dominant hand on the base of the transducer with the non-dominant hand on the tail of the transducer, providing additional stability and guided movement.</li>
</ol>
2. Patient positioning
<ol>
	<li>Obtain the PLAX, PSAX, A4C, SC4C, and IVC views in the supine position.</li>
	<li>Instruct the patient to extend their left arm above their head and lie on their left side, and obtain images in this position if they are unable to be obtained in the supine position. 
	NOTE: This results in expansion of the intercostal spaces for larger imaging windows.
	<ol>
		<li>Place a wedge or blanket roll behind the patient&#39;s right upper torso if the patient cannot easily rotate to 45&#176;, or reposition their limbs. Postoperative and intensive care unit patients often need support to maintain appropriate positioning for FoCUS examination.</li>
	</ol>
	</li>
	<li>Drape the breast as desired by the patient, and make sure that the patient is aware of where the transducer will be placed before beginning the exam.</li>
	<li>Manipulate the breast tissue to allow for optimal image acquisition.
	<ol>
		<li>If able, instruct the patient to assist moving the breast tissue with their right hand.</li>
	</ol>
	</li>
	<li>Discuss the appropriateness of removal or relocation of monitors beforehand with bedside nurses and other relevant providers.</li>
	<li>Do not alter or remove tubes, lines, or drains for imaging purposes. Discuss the duration of the devices with the relevant providers and consider reimaging the patient following their removal.</li>
</ol>
3. Transducer manipulation
<ol>
	<li>Appreciate and understand the definitions of transducer movements to allow for optimal image acquisition, and provide consistent terminology for communication between providers, especially during teaching (Figure 1 and Table 1).</li>
</ol>
4. 2-D image optimization
<ol>
	<li>Adjust the depth (approximately 12-16 cm, depending on view) to see the structure of interest.</li>
	<li>Adjust the gain to optimize the brightness of the image.</li>
	<li>Adjust the focus to the depth of the structure of interest in order to improve resolution.</li>
</ol>
5. Motion mode (M-mode)
<ol>
	<li>Use M-mode to display a single scan line (wherever the cursor is placed) of the B-mode image (Y-axis) against time (X-axis). 
	NOTE: This mode can help operators understand the dynamic relationship of different structures over time and is useful in many different assessments, including IVC size and variability and E-point septal separation (EPSS).</li>
	<li>Use the button with the letter &#34;M&#34; on it to turn on M-mode. 
	&#8203;NOTE: M-mode will be an on/off button unique to each machine.</li>
</ol>
6. Parasternal long axis (PLAX)
NOTE: The PLAX refers to obtaining an image that is along the long axis of the heart (Figure 2).
<ol>
	<li>Place the patient in the supine position. If there is difficulty obtaining the PLAX image, place the patient on their left side and extend their arm above their head, if possible.</li>
	<li>Place the transducer at an oblique angle between the third and fifth intercostal space of the left parasternal region, with the transducer marker pointing to the patient&#39;s right shoulder.
	<ol>
		<li>Visualize the right ventricle, left ventricle, left atrium, mitral valve, left ventricular outflow tract, aortic valve, and descending thoracic aorta in this image.</li>
		<li>Visualize the mitral valve and aortic valve opening and closing together, to ensure that the image is not foreshortened. Foreshortening is where the ultrasound plane does not cut through the true apex of the structure, changing the perceived image.</li>
	</ol>
	</li>
	<li>2-D image optimization
	<ol>
		<li>Start with an initial depth of approximately 15-20 cm. Adjust the depth so that the tip of the mitral valve is in the center of the image, and the descending thoracic aorta (deep to the left atrium) is visible.</li>
		<li>Adjust the gain to maximize the visibility of the myocardium and mitral valve.</li>
		<li>Move the focus to the region of interest, most focused at the depth of the mitral valve.</li>
		<li>Use M-mode for EPSS or fractional shortening.</li>
	</ol>
	</li>
</ol>
7. Parasternal short axis (PSAX; Figure 3)
<ol>
	<li>Place the patient in the same positioning for the PSAX as used for the PLAX.</li>
	<li>Place the transducer approximately 90&#176; relative to the transducer in the PLAX.
	<ol>
		<li>Obtain an optimal PLAX and rotate the transducer slowly in a clockwise fashion without lifting the transducer from the patient&#39;s chest, until the transducer is obliquely angled across the third to fifth intercostal space of the parasternal region, with the transducer marker pointing to the patient&#39;s left shoulder. 
		NOTE: Over-rotation beyond 90&#176; can lead to interventricular septal flattening, and falsely appear as right ventricular volume or pressure overload.</li>
		<li>Tilt the transducer until the mid-papillary muscles are visualized for the FoCUS assessment. 
		NOTE: The papillary muscles should move in synchrony with the left ventricle wall. If the papillary muscles appear to be bouncing or fluttering independent of the left ventricular wall, it may signify that the image is capturing the mitral valve leaflet as a result of being off axis.</li>
		<li>Tilt the transducer toward the base of the heart, to visualize the bi-leaflet mitral valve initially followed by the tri-leaflet aortic valve.</li>
	</ol>
	</li>
	<li>2-D image optimization
	<ol>
		<li>Start with a deeper image (approximately 16 cm) to identify any pleural effusion.</li>
		<li>Adjust the depth to include the full depth of the left ventricle and a few centimeters beyond, to ensure that a pericardial effusion would be fully visualized.</li>
		<li>Adjust the gain to maximize visualization of the septum and papillary muscles.</li>
		<li>Adjust the focus to the papillary muscles.</li>
	</ol>
	</li>
</ol>
8. Apical four chamber view (A4C; Figure 4)
NOTE: Images in patients with chronic obstructive pulmonary disease (COPD), and otherwise inflamed thoracic cavities, are obtained more medially, and images in patients with left ventricular hypertrophy (LVH) or heart failure with reduced ejection fraction (HFrEF) have their view more lateral.
<ol>
	<li>Position the patient with their left arm extended above their head and lying on their left side. If there is significant artifact present, have the patient exhale and hold their breath to minimize pulmonary artifact.</li>
	<li>Position the transducer in the fourth through sixth intercostal space along the left anterior axillary line (inferolateral to the left pectoral muscle), with the transducer marker pointed toward the left axilla. Move the transducer lateral, medial, or caudal, as needed to obtain an optimal A4C view.
	<ol>
		<li>Lift the breast tissue and push superior along the inframammary fold as needed.</li>
		<li>If the left ventricular apex is not fully visualized, move the transducer lateral while orienting the transducer toward the right shoulder.</li>
		<li>Position the marker on the phased array transducer between the two and three o&#39;clock positions. In the normal heart, the apex of the left ventricle is at the top and center of the sector, the right ventricle is triangular and smaller, and the myocardium should be uniform from the apex to the atrioventricular valves. If this is not the case, the image may be foreshortened, and should be optimized and acquired from a lower intercostal space.</li>
		<li>Tilt the transducer cephalad approximately 60&#176;, so that the A4C view can capture an A4C cardiac image that includes both atria, ventricles, the interventricular septum, and the lateral portions of the tricuspid and mitral annuli. The aortic valve and left ventricular outflow tract should not be present in an A4C view, and are only present in an apical five chamber view.</li>
		<li>Visualize the mitral valve, the tricuspid valves, and the interventricular septum on the A4C image. If both valves and the interventricular septum are not visualized, the image should be further optimized.</li>
		<li>Slide the transducer up or down a rib space and tilt the base of the transducer down (cranially) to improve the image of the valves. If the base of the transducer is tilted too far down (cranially), an apical five chamber view, including the aortic valve, will appear, and the transducer should be tilted back up (caudally) to optimize the A4C view. If the base of the transducer is tilted too far up (caudally), the coronary sinus will appear, and the transducer should be tilted back down (cranially).</li>
		<li>Rotate the base of the transducer toward the patient&#39;s midline to optimize the interventricular septum position, which should be present vertical in the center of the image. Minimal rotation should be required. If over-rotated, a two chamber view will be observed.</li>
	</ol>
	</li>
	<li>2-D image optimization
	<ol>
		<li>Increase the depth to include both atria at the image&#39;s deepest point, in addition to accommodating the left and right ventricular free walls (approximately an initial depth of 20 cm).</li>
		<li>Adjust the gain to maximize visibility, often resulting in increased echogenicity, of the myocardium, the mitral valvular annulus, and the tricuspid valvular annulus.</li>
		<li>Adjust the focus to the depth of the valvular annuli (the tricuspid annulus is most commonly used). This depth will also be appropriate when transitioning to an apical five view, if desired.</li>
	</ol>
	</li>
</ol>
9. Subcostal four chamber view (SC4C; Figure 5)
<ol>
	<li>Position the patient supine for the subcostal four chamber view. Flex the patient&#39;s knees, and support them to maintain the flexed position, to reduce the abdominal muscle tone for easier transducer compression.</li>
	<li>Place the transducer nearly flat on the patient&#39;s subxiphoid abdomen, with the operator hand on top of the transducer providing cephalad pressure. Find the liver, and then drop the transducer to a shallower angle (often less than 30&#176;) against the subxiphoid portion of the patient&#39;s abdomen in a cephalad fashion, with the transducer marker to the patient&#39;s left side, approximately pointing to three o&#39;clock. Include the liver in the image so that it can be utilized as an acoustic window to obtain this image.
	<ol>
		<li>Hold the lateral aspects of the transducer with the fingers, not underneath the transducer, to flatten the transducer appropriately. Use the index finger to provide downward pressure.</li>
	</ol>
	</li>
	<li>2-D image optimization
	<ol>
		<li>Start with an initial depth of 18-24 cm. Adjust the depth to include the liver as a sonographic window for the ultrasound. The optimal depth varies from patient to patient based on patient body habitus and liver size.</li>
		<li>Decrease the gain, as the liver often provides a good medium to transmit sound waves.</li>
		<li>Increase the focal points to focus on the cardiac structures of interest below the liver.</li>
		<li>Instruct non-intubated patients to perform an inspiratory hold, as this often increases the quality of the image.</li>
	</ol>
	</li>
</ol>
10. Inferior vena cava (IVC; Figure 6)
<ol>
	<li>Position the patient supine for the IVC view.</li>
	<li>Begin with the subcostal view, then rotate the transducer counterclockwise until confluence of the right atrium and IVC is appreciated, and the transducer is placed longitudinally in the upper abdomen, to the right of the patient&#39;s midline. Optimize the image by tilting the transducer until the IVC is fully visualized, and then by rocking the transducer cephalad until the confluence of the IVC and the right atrium is fully visualized. Adjust the transducer (most frequently with minimal rotation) until the IVC is visualized across the entire screen.
	<ol>
		<li>Visualize the right atrium, IVC, liver, and hepatic vein in an optimal view.</li>
		<li>Do not confuse the IVC with the aorta. The aorta is left lateral of the IVC and will not touch the liver. The IVC will always touch the liver, and is often surrounded by liver on both sides.
		<ol>
			<li>Appreciate that hepatic veins can often be seen coming into the IVC, providing another way to prove that the structure being imaged is the IVC.</li>
			<li>Use pulse wave velocity to visualize the venous (vs. arterial) waveform, and confirm the vessel being imaged is the IVC and not the aorta.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Measure IVC diameters at midline and mid-expiration. Do not measure the diameter of the IVC to the side which could underestimate the diameter of the IVC.</li>
	<li>2-D image optimization
	<ol>
		<li>Minimize the depth to only include the IVC. Do not include the spine in the image.</li>
		<li>Adjust the gain to be the same as for the subcostal view.</li>
		<li>Adjust the focus to the depth of the IVC.</li>
		<li>Place the cursor 1-3 cm from the confluence of the IVC and the right atrium, and apply M-mode to evaluate respiratory variation of the IVC.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Birch, M. S., Marin, J. R., Liu, R. B., Hall, J., Hall, M. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Trends+in+diagnostic+point-of-care+ultrasonography+reimbursement+for+medicare+beneficiaries+among+the+US+emergency+medicine+workforce,+2012+to+2016.">Trends in diagnostic point-of-care ultrasonography reimbursement for medicare beneficiaries among the US emergency medicine workforce, 2012 to 2016.</a> Annals of Emergency Medicine. 76 (5), 609-614 (2020).</li><li>Moore, C. L., Copel, J. 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N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Point-of-care+ultrasound+for+assessing+arteriovenous+fistula+maturity+in+outpatient+hemodialysis.">Point-of-care ultrasound for assessing arteriovenous fistula maturity in outpatient hemodialysis.</a> The Journal of Vascular Access. 21 (6), 923-930 (2020).</li><li>Gundersen, G. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adding+point+of+care+ultrasound+to+assess+volume+status+in+heart+failure+patients+in+a+nurse-led+outpatient+clinic.+A+randomised+study.">Adding point of care ultrasound to assess volume status in heart failure patients in a nurse-led outpatient clinic. A randomised study.</a> Heart. 102 (1), 29-34 (2016).</li><li>Kirkpatrick, J. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recommendations+for+echocardiography+laboratories+participating+in+cardiac+point+of+care+cardiac+ultrasound+(POCUS)+and+critical+care+echocardiography+training:+report+from+the+American+Society+of+Echocardiography.">Recommendations for echocardiography laboratories participating in cardiac point of care cardiac ultrasound (POCUS) and critical care echocardiography training: report from the American Society of Echocardiography.</a> Journal of the American Society of Echocardiography. 33 (4), 409-422 (2020).</li><li>Annals of Emergency Medicine. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrasound+Guidelines:+Emergency,+point-of-care+and+clinical+ultrasound+guidelines+in+medicine.">Ultrasound Guidelines: Emergency, point-of-care and clinical ultrasound guidelines in medicine.</a> Annals of Emergency Medicine. 69 (5), 27-54 (2017).</li><li>Levitov, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Guidelines+for+the+appropriate+use+of+bedside+general+and+cardiac+ultrasonography+in+the+evaluation+of+critically+ill+patients-part+II:+cardiac+ultrasonography.">Guidelines for the appropriate use of bedside general and cardiac ultrasonography in the evaluation of critically ill patients-part II: cardiac ultrasonography.</a> Critical Care Medicine. 44 (6), 1206-1227 (2016).</li><li>Neskovic, A. 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The authors whose names are listed immediately below certify that they have NO affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers' bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge, or beliefs) in the subject matter or materials discussed in this manuscript.

The aim of this publication is to provide practical recommendations and best practices to achieve optimal FoCUS images in challenging clinical environments. Formal ultrasound seminars, clinical experience, and observations of learners during hands-on teaching have given insight into pitfalls and less optimal tendencies. As a result, many factors that influence the stereotactic and psychomotor skills have become apparent. Although this material is described in relation to FoCUS exams, many of the principles can be applied...

Focused cardiac ultrasound (FoCUS) is a limited, clinician-performed application of echocardiography that provides immediate anatomic, physiologic, and functional information to patient care. These exams, consisting of five classic views, are problem oriented, performed in real time at the bedside, and do not replace comprehensive echocardiography exams1,2. Given the focused nature of these exams, they are often repeatedly performed when clinical status changes or serial monitoring is required. It is important to have standardized training and obtain adequate images of all five views, when possible, as some views may provide limited information depending on the individual patient and pathology.
The use of FoCUS is rapidly expanding. Many clinical landscapes, such as perioperative anesthesiology, critical care and emergency medicine1,2,3, now routinely employ FoCUS. Inpatient medical wards and outpatient clinical care settings are also adopting this tool to enhance clinical practice4,5,6. As a result, several societal bodies, such as the American Society of Echocardiography, the Society of Critical Care Medicine, and the American College of Emergency Physicians, have published guidelines and recommendations for FoCUS competency and scope of practice7,8,9. While these guidelines and recommendations are not codified, much of the content is consistent and influences FoCUS training curricula10.
Beyond didactics and image interpretation, competency in FoCUS includes mastery of stereotactic and psychomotor skill sets. Stereotactic skill refers to the accurate positioning of ultrasound transducers on the body, based on three-dimensional anatomic features. Psychomotor skill describes the relationship between cognitive function and physical movement that influences coordination, dexterity, and manipulation. Expanding knowledge and awareness about these skills supports FoCUS trainee development.
This article presents concepts for high-quality image acquisition in FoCUS, with both pragmatic considerations and attention to stereotactic and psychomotor skill sets. Specifically, it discusses optimal patient positioning, transducer manipulation, and suggests tips to optimize phased array transducer use. Finally, it examines image optimization for 2-dimensional (B-mode or 2-D mode) and motion modes (M-mode).

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troubleshooting focus image acquisition: patient positioning, transducer manipulation, and image optimization

Focused cardiac ultrasound (FoCUS) is a limited, clinician-performed application of echocardiography to add real-time information to patient care. These bedside exams are problem oriented, rapidly and repeatedly performed, and largely qualitative in nature. Competency in FoCUS includes mastery of the stereotactic and psychomotor skills required for transducer manipulation and image acquisition. Competency also requires the ability to optimize the setup, troubleshoot image acquisition, and understand the sonographic limitations because of complex clinical environments and patient pathology. This article presents concepts for successful, high-quality two-dimensional (B-mode) image acquisition in FoCUS.
Concepts of high-quality image acquisition can be applied to all established sonographic windows of the FoCUS exam: the parasternal long-axis (PLAX), parasternal short-axis (PSAX), apical four chamber (A4C), subcostal fourchamber (SC4C), and the inferior vena cava (IVC). The apical five-chamber (A5C) and subcostal short-axis (SCSA) views are mentioned, but are not discussed in-depth. A pragmatic figure illustrating the movements of the phased array transducer is also provided to serve as a cognitive aid during FoCUS image acquisition.

Representative images obtained from the focused cardiac ultrasound protocol presented above are presented in Figure 2, Figure 3, Figure 4, Figure 5, and Figure 6, demonstrating the feasibility of the technique described. These images were captured with the phased array 5-1 MHz transducer. The parasternal long axis (PLAX) image obtained from protocol se...

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Troubleshooting FoCUS Image Acquisition: Patient Positioning, Transducer Manipulation, and Image Optimization

Here, we present a protocol to allow providers to perform focused cardiac ultrasound (FoCUS) in the clinical environment. We describe methods of transducer manipulation, review common pitfalls of transducer movements, and suggest tips to optimize phased array transducer use.

Focused cardiac ultrasound (FoCUS) is a limited, clinician-performed application of echocardiography to add real-time information to patient care. These ...

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1.4K Views.  University of Michigan, Ann Arbor. Here, we present a protocol to allow providers to perform focused cardiac ultrasound (FoCUS) in the clinical environment. We describe methods of transducer manipulation, review common pitfalls of transducer movements, and suggest tips to optimize phased array transducer use. 

Video: Troubleshooting FoCUS Image Acquisition: Patient Positioning, Transducer Manipulation, and Image Optimization

Evaluating Targeting Accuracy in the Focal Plane for an Ultrasound-guided High-intensity Focused Ultrasound Phased-array System

Phased arrays are increasingly used as high-intensity focused ultrasound (HIFU) transducers in the existing extracorporeal ultrasound-guided HIFU (USgHIFU) systems. The HIFU transducers in such systems are usually spherical in shape with a central hole where a US imaging probe is mounted and can be rotated. The image on the plane of treatment can be reconstructed through the image sequence acquired during the rotation of the probe. Therefore, the treatment plan can be made on the reconstructed images. In order to evaluate the targeting accuracy in the focal plane of such systems, the protocol of a method using a bovine muscle and marker-embedded phantom is described. In the phantom, four solid balls at the corners of a square resin model serve as the reference markers in the reconstructed image. The target should be moved so that both its center and the center of the square model can coincide according to their relative positions in the reconstructed image. Swine muscle with a thickness of about 30 mm is placed above the phantom to mimic the beam path in clinical settings. After sonication, the treatment plane in the phantom is scanned and the boundary of the associated lesion is extracted from the scanned image. The targeting accuracy can be evaluated by measuring the distance between the centers of target and lesion, as well as three derivative parameters. This method cannot only evaluate the targeting accuracy of the target consisting of multiple focal spots rather than a single focal spot in a clinically relevant beam path of the USgHIFU phased-array system, but it can be also used in the preclinical evaluation or regular maintenance of USgHIFU systems configured with phased-array or self-focused HIFU transducer.

This study describes a protocol to evaluate the targeting accuracy in the focal plane of an ultrasound-guided high-intensity focused ultrasound phased-array system.

Phased arrays are increasingly used as high-intensity focused ultrasound (HIFU) transducers in the existing extracorporeal ultrasound-guided HIFU ...

Engineering

Quantitative Magnetic Resonance Imaging of Skeletal Muscle Disease

Quantitative magnetic resonance imaging (qMRI) describes the development and use of MRI to quantify physical, chemical, and/or biological properties of living systems. Neuromuscular diseases often exhibit a temporally varying, spatially heterogeneous, and multi-faceted pathology. The goal of this protocol is to characterize this pathology using qMRI methods. The MRI acquisition protocol begins with localizer images (used to locate the position of the body and tissue of interest within the MRI system), quality control measurements of relevant magnetic field distributions, and structural imaging for general anatomical characterization. The qMRI portion of the protocol includes measurements of the longitudinal and transverse relaxation time constants (T1 and T2, respectively). Also acquired are diffusion-tensor MRI data, in which water diffusivity is measured and used to infer pathological processes such as edema. Quantitative magnetization transfer imaging is used to characterize the relative tissue content of macromolecular and free water protons. Lastly, fat-water MRI methods are used to characterize fibro-adipose tissue replacement of muscle. In addition to describing the data acquisition and analysis procedures, this paper also discusses the potential problems associated with these methods, the analysis and interpretation of the data, MRI safety, and strategies for artifact reduction and protocol optimization.

Neuromuscular diseases often exhibit a temporally varying, spatially heterogeneous, and multi-faceted pathology. The goal of this protocol is to characterize this pathology using non-invasive magnetic resonance imaging methods.

Quantitative magnetic resonance imaging (qMRI) describes the development and use of MRI to quantify physical, chemical, and/or biological properties of ...

Effective Co-Registration of Two Preclinical Imaging Modalities Across Devices

Multimodal Cross-Device and Marker-Free Co-Registration of Preclinical Imaging Modalities

Integrated preclinical multimodal imaging systems, such as X-ray computed tomography (CT) combined with positron emission tomography (PET) or magnetic resonance imaging (MRI) combined with PET, are widely available and typically provide robustly co-registered volumes. However, separate devices are often needed to combine a standalone MRI with an existing PET-CT or to incorporate additional data from optical tomography or high-resolution X-ray microtomography. This necessitates image co-registration, which involves complex aspects such as multimodal mouse bed design, fiducial marker inclusion, image reconstruction, and software-based image fusion. Fiducial markers often pose problems for in vivo data due to dynamic range issues, limitations on the imaging field of view, difficulties in marker placement, or marker signal loss over time (e.g., from drying or decay). These challenges must be understood and addressed by each research group requiring image co-registration, resulting in repeated efforts, as the relevant details are rarely described in existing publications.
This protocol outlines a general workflow that overcomes these issues. Although a differential transformation is initially created using fiducial markers or visual structures, such markers are not required in production scans. The requirements for the volume data and the metadata generated by the reconstruction software are detailed. The discussion covers achieving and verifying requirements separately for each modality. A phantom-based approach is described to generate a differential transformation between the coordinate systems of two imaging modalities. This method showcases how to co-register production scans without fiducial markers. Each step is illustrated using available software, with recommendations for commercially available phantoms. The feasibility of this approach with different combinations of imaging modalities installed at various sites is showcased.

Author Spotlight: An Efficient and Robust Software for Automated Fusion of Multiple Preclinical Imaging Modalities

The combination of multiple imaging modalities is often necessary to gain a comprehensive understanding of pathophysiology. This approach utilizes phantoms to generate a differential transformation between the coordinate systems of two modalities, which is then applied for co-registration. This method eliminates the need for fiducials in production scans.

Integrated preclinical multimodal imaging systems, such as X-ray computed tomography (CT) combined with positron emission tomography (PET) or magnetic ...

Bioengineering

Obtaining High-Quality Hyperpolarized Xenon-129 Magnetic Resonance Images

Troubleshooting and Quality Assurance in Hyperpolarized Xenon Magnetic Resonance Imaging: Tools for High-Quality Image Acquisition

Hyperpolarized (HP) xenon magnetic resonance imaging (129Xe MRI) is a recently federal drug administration (FDA)-approved imaging modality that produces high-resolution images of an inhaled breath of xenon gas for investigation of lung function. However, implementing 129Xe MRI is uniquely challenging as it requires specialized hardware and equipment for hyperpolarization, procurement of xenon imaging coils and coil software, development and compilation of multinuclear MR imaging sequences, and reconstruction/analysis of acquired data. Without proper expertise, these tasks can be daunting, and failure to acquire high-quality images can be&#160;frustrating, and expensive. Here, we present some quality control (QC) protocols, troubleshooting practices, and helpful tools for129Xe MRI sites, which may aid in the acquisition of optimized, high-quality data and accurate results. The discussion will begin with an overview of the process for implementing HP 129Xe MRI, including requirements for a hyperpolarizer lab, the combination of 129Xe MRI coil hardware/software, data acquisition and sequence considerations, data structures, k-space and image properties, and measured signal and noise characteristics. Within each of these necessary steps lies opportunities for errors, challenges, and unfavorable occurrences leading to poor image quality or failed imaging, and this presentation aims to address some of the more commonly encountered issues. In particular, identification and characterization of anomalous noise patterns in acquired data are necessary to avoid image artifacts and low-quality images; examples will be given, and mitigation strategies will be discussed. We aim to make the 129Xe MRI implementation process easier for new sites while providing some guidelines and strategies for real-time troubleshooting.

Author Spotlight: Using Hyperpolarized Xenon-129 MRI to Study Lung Diseases 

Here, we present a protocol for obtaining high-quality hyperpolarized xenon-129 magnetic resonance images, covering hardware, software, data acquisition, sequence selection, data management, k-space utilization, and noise analysis.

Hyperpolarized (HP) xenon magnetic resonance imaging (129Xe MRI) is a recently federal drug administration (FDA)-approved imaging modality that produces ...

Point-of-Care Lung Ultrasound in Adults: Image Acquisition

Consultative ultrasound performed by radiologists has traditionally not been used for imaging the lungs, as the lungs&#39; air-filled nature normally prevents direct visualization of the lung parenchyma. When showing the lung parenchyma, ultrasound typically generates a number of non-anatomic artifacts. However, over the past several decades, these artifacts have been studied by diagnostic point-of-care ultrasound (POCUS) practitioners, who have identified findings that have value in narrowing the differential diagnoses of cardiopulmonary dysfunction. For instance, in patients presenting with dyspnea, lung POCUS is superior to chest radiography (CXR) for the diagnosis of pneumothorax, pulmonary edema, lung consolidations, and pleural effusions. Despite its known diagnostic value, the utilization of lung POCUS in clinical medicine remains variable, in part because training in this modality across hospitals remains inconsistent. To address this educational gap, this narrative review describes lung POCUS image acquisition in adults, including patient positioning, transducer selection, probe placement, acquisition sequence, and image optimization.

Point-of-care ultrasound (POCUS) of the lungs provides quick answers in rapidly changing clinical scenarios. We present an efficient and informative protocol for image acquisition for use in acute care settings.

Consultative ultrasound performed by radiologists has traditionally not been used for imaging the lungs, as the lungs&#39; air-filled nature normally ...

Point-of-Care Ultrasound: A Review of Ultrasound Parameters for Predicting Difficult Airways

Airway management remains a crucial part of perioperative care. The conventional approach to assessing potentially difficult airways emphasizes the LEMON method, which looks for and evaluates the Mallampati classification, signs of obstruction, and neck mobility. Clinical findings help predict a higher likelihood of difficult tracheal intubation, but no clinical result reliably excludes difficult intubation. Ultrasound as an adjunct to clinical examination can provide the clinician with a dynamic anatomical airway assessment, which is impossible with clinical examination alone. In the hands of anesthesiologists, ultrasound is becoming more popular in the perioperative period. This method is particularly applicable for identifying proper endotracheal tube positioning in specific patient populations, such as those who are morbidly obese and patients with head and neck cancer or trauma. The focus is on identifying the normal anatomy, correctly positioning the endotracheal tube, and refining the parameters that predict difficult intubation. Several ultrasound measurements are clinical indicators of difficult direct laryngoscopy in the literature. A meta-analysis revealed that the distance from the skin to the epiglottis (DSE) is most associated with a difficult laryngoscopy. An ultrasound of the airway could be applied in routine practice as an adjunct to the clinical examination. A full stomach, rapid sequence intubation, gross visual anatomical abnormalities, and restricted neck flexibility prevent using ultrasound to assess the airway. The airway evaluation is performed with a linear array transducer of 12-4 MHz, with the patient in the supine position, with no pillow, and with the head and neck in a neutral position. The central axis of the neck is where the ultrasound parameters are measured. These image acquisitions guide the standard ultrasound examination of the airway.

A point-of-care ultrasound (POCUS) is a simple, non-invasive, and portable tool that enables dynamic airway assessment. Several studies have attempted to determine the role of ultrasound parameters as an adjunct to clinical examination in predicting difficult laryngoscopies.

Airway management remains a crucial part of perioperative care. The conventional approach to assessing potentially difficult airways emphasizes the LEMON ...

Focused Assessment with Sonography for Trauma (FAST) Exam: Image Acquisition

Over the past twenty years, the Focused Assessment with Sonography for Trauma (FAST) exam has transformed the care of patients presenting with a combination of trauma (blunt or penetrating) and hypotension. In these hemodynamically unstable trauma patients, the FAST exam permits rapid and noninvasive screening for free pericardial or peritoneal fluid, the latter of which implicates intra-abdominal injury as a likely contributor to the hypotension and justifies emergent abdominal surgical exploration. Further, the abdominal portion of the FAST exam can also be used outside of the trauma setting to screen for free peritoneal fluid in patients who become hemodynamically unstable in any context, including after procedures that may inadvertently injure abdominal organs. These "non-trauma" situations of hemodynamic instability are often triaged by providers from specialties other than emergency medicine or trauma surgery who are not familiar with the FAST exam. Therefore, there is a need to promulgate knowledge about the FAST exam to all clinicians caring for critically ill patients. Toward this end, this article describes FAST exam image acquisition: patient positioning, transducer selection, image optimization, and exam limitations. Since the free fluid is likely to be found in specific anatomic locations that are unique for each canonical FAST exam view, this work centers on the unique image acquisition considerations for each window: subcostal, right upper quadrant, left upper quadrant, and pelvis.

Focused Assessment with Sonography for Trauma FAST Exam: Image Acquisition

The Focused Assessment with Sonography for Trauma (FAST) exam is a diagnostic point-of-care ultrasound examination used to screen for the presence of free fluid in the pericardium and peritoneum. Indications, techniques, and pitfalls of the procedure are discussed in this article.

Over the past twenty years, the Focused Assessment with Sonography for Trauma (FAST) exam has transformed the care of patients presenting with a ...

Strategies for Optimization of Cryogenic Electron Tomography Data Acquisition

Cryogenic electron tomography (cryoET) is a powerful method to study the 3D structure of biological samples in a close-to-native state. Current state-of-the-art cryoET combined with subtomogram averaging analysis enables the high-resolution structural determination of macromolecular complexes that are present in multiple copies within tomographic reconstructions. Tomographic experiments usually require a vast amount of tilt series to be acquired by means of high-end transmission electron microscopes with important operational running-costs. Although the throughput and reliability of automated data acquisition routines have constantly improved over the recent years, the process of selecting regions of interest at which a tilt series will be acquired cannot be easily automated and it still relies on the user's manual input. Therefore, the set-up of a large-scale data collection session is a time-consuming procedure that can considerably reduce the remaining microscope time available for tilt series acquisition. Here, the protocol describes the recently developed implementations based on the SerialEM package and the PyEM software that significantly improve the time-efficiency of grid screening and large-scale tilt series data collection. The presented protocol illustrates how to use SerialEM scripting functionalities to fully automate grid mapping, grid square mapping, and tilt series acquisition. Furthermore, the protocol describes how to use PyEM to select additional acquisition targets in off-line mode after automated data collection is initiated. To illustrate this protocol, its application in the context of high-end data collection of Sars-Cov-2 tilt series is described. The presented pipeline is particularly suited to maximizing the time-efficiency of tomography experiments that require a careful selection of acquisition targets and at the same time a large amount of tilt series to be collected.

The increasing demand for large-scale data collection in cryogenic electron tomography requires high-throughput image acquisition routines. Described here is a protocol that implements the recent developments of advanced acquisition strategies aimed at maximizing the time-efficiency and throughput of tomographic data collection.

Cryogenic electron tomography (cryoET) is a powerful method to study the 3D structure of biological samples in a close-to-native state. Current ...

Biology

Advanced Lung Imaging for Disease Detection and Monitoring

Phase-Resolved Functional Lung MRI for Pulmonary Ventilation and Perfusion (V/Q) Assessment

Fourier decomposition is a contrast agent-free 1H MRI method for lung perfusion (Q) and ventilation (V) assessment. After image registration, the time series of each voxel is analyzed with regard to the cardiac and breathing frequency components.
Using a standard 2D spoiled gradient-echo sequence with a temporal resolution of ~300 ms, an image-sorting algorithm was developed to produce phase-resolved functional lung imaging (PREFUL) with an increased temporal resolution. Thus, it is feasible to evaluate regional flow volume loops (FVL) during tidal volume breathing and depict the propagation of the pulse wave during the cardiac cycle. This method can be applied at 1.5T or 3T with standard MR hardware without the necessity for sequence programming, as the described protocol can be implemented with the default SPGRE sequence on most systems.
PREFUL ventilation MRI has been validated using 129Xe and 19F gas imaging with good regional agreement. Perfusion-weighted PREFUL MRI has been validated using SPECT as well as dynamic contrast enhanced (DCE) MRI. PREFUL has been tested in a dual center dual vendor setting and is currently applied in several ongoing multicenter trials. Furthermore, it is feasible across a range of field strengths (0.55T-3T) and different age groups, including newborns.
Quantitative V/Q PREFUL MRI has been used in patients with cystic fibrosis, chronic obstructive pulmonary disease, chronic thromboembolic pulmonary hypertension, and corona virus disease-2019 to quantify disease and monitor treatment change after therapy. Furthermore, PREFUL V/Q imaging has been shown to predict transplant loss due to chronic lung allograft dysfunction in patients after lung transplantation. In summary, PREFUL MRI is a validated technique for quantitative ventilation and pulmonary pulse wave/perfusion imaging for regional pulmonary disease detection, quantification, and treatment monitoring with potential added value to the current clinical routine.

Author Spotlight: Enhancing Diagnostic Strategies and Biomarker Development for Comprehensive Lung Function Analysis

Here, we describe the implementation of phase-resolved functional lung MRI as a contrast-agent-free proton MR technique for the assessment of pulmonary ventilation and perfusion dynamics. Validated and applicable across different field strengths and age groups, it could enhance clinical decision-making in the future by aiding in disease quantification and therapy monitoring.

Fourier decomposition is a contrast agent-free 1H MRI method for lung perfusion (Q) and ventilation (V) assessment. After image registration, the time ...

Cryo-Electron Tomography Remote Data Collection and Subtomogram Averaging

Cryo-electron tomography (cryo-ET) has been gaining momentum in recent years, especially since the introduction of direct electron detectors, improved automated acquisition strategies, preparative techniques that expand the possibilities of what the electron microscope can image at high-resolution using cryo-ET and new subtomogram averaging software. Additionally, data acquisition has become increasingly streamlined, making it more accessible to many users. The SARS-CoV-2 pandemic has further accelerated remote cryo-electron microscopy (cryo-EM) data collection, especially for single-particle cryo-EM, in many facilities globally, providing uninterrupted user access to state-of-the-art instruments during the pandemic. With the recent advances in Tomo5 (software for 3D electron tomography), remote cryo-ET data collection has become robust and easy to handle from anywhere in the world. This article aims to provide a detailed walk-through, starting from the data collection setup in the tomography software for the process of a (remote) cryo-ET data collection session with detailed troubleshooting. The (remote) data collection protocol is further complemented with the workflow for structure determination at near-atomic resolution by subtomogram averaging with emClarity, using apoferritin as an example.

The present protocol describes high-resolution cryo-electron tomography remote data acquisition using Tomo5 and subsequent data processing and subtomogram averaging using emClarity. Apoferritin is used as an example to illustrate detailed step-by-step processes to achieve a cryo-ET structure at 2.86 &#197; resolution.

Cryo-electron tomography (cryo-ET) has been gaining momentum in recent years, especially since the introduction of direct electron detectors, improved ...