This work was supported by Charley&#39;s Fund and NIH R01NS055099.

All methods described here have been approved by the Institutional Animal Care and Use Committee of Beth Israel Deaconess Medical Center under protocol numbers (031-2019; 025-2019). Wear proper PPE equipment to handle animals and adhere to IACUC guidelines for all animal work.
1. In vivo surface EIM
<ol>
	<li>Place the animal in an anesthesia box to induce anesthesia. 
	NOTE: For rats, 1.5%-3.5% isoflurane and 2 O2 L&#183;min-1 were used, ...

<ol>
	<li>Rutkove, S. B., Sanchez, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrical+impedance+methods+in+neuromuscular+assessment:+An+overview.">Electrical impedance methods in neuromuscular assessment: An overview.</a> Cold Spring Harbor Perspectives in Medicine. 9 (10), 034405 (2019).</li><li>Rutkove, S. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrical+impedance+myography:+Background,+Current+State,+and+Future+Directions.">Electrical impedance myography: Background, Current State, and Future Directions.</a> Muscle &amp; Nerve. 40, 936-946 (2009).</li><li>Sanchez, B., Rutkove, S. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Present+uses,+future+applications,+and+technical+underpinnings+of+electrical+impedance+myography.">Present uses, future applications, and technical underpinnings of electrical impedance myography.</a> Current Neurology and Neuroscience Reports. 17 (11), 86 (2017).</li><li>Garmirian, L. P., Chin, A. B., Rutkove, S. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Discriminating+neurogenic+from+myopathic+disease+via+measurement+of+muscle+anisotropy.">Discriminating neurogenic from myopathic disease via measurement of muscle anisotropy.</a> Muscle &amp; Nerve. 39 (1), 16-24 (2009).</li><li>Rutkove, S. B., 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=Loss+of+electrical+anisotropy+is+an+unrecognized+feature+of+dystrophic+muscle+that+may+serve+as+a+convenient+index+of+disease+status.">Loss of electrical anisotropy is an unrecognized feature of dystrophic muscle that may serve as a convenient index of disease status.</a> Clinical Neurophysiology. 127 (12), 3546-3551 (2016).</li><li>Wang, L. L., 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=Assessment+of+alterations+in+the+electrical+impedance+of+muscle+after+experimental+nerve+injury+via+finite-element+analysis.">Assessment of alterations in the electrical impedance of muscle after experimental nerve injury via finite-element analysis.</a> IEEE Transactions on Biomedical Engineering. 58 (6), 1585-1591 (2011).</li><li>Katirji, B., Ruff, R. L., Kaminski, H. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Neuromuscular Disorders in Clinical Practice. , (2014).</li><li>Rutkove, S. B., 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=Electrical+impedance+myography+for+assessment+of+Duchenne+muscular+dystrophy.">Electrical impedance myography for assessment of Duchenne muscular dystrophy.</a> Annals of Neurology. 81 (5), 622-632 (2017).</li><li>Semple, C., 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=Using+electrical+impedance+myography+as+a+biomarker+of+muscle+deconditioning+in+rats+exposed+to+micro-+and+partial-gravity+analogs.">Using electrical impedance myography as a biomarker of muscle deconditioning in rats exposed to micro- and partial-gravity analogs.</a> Frontiers in Physiology. 11, 557796 (2020).</li><li>Kortman, H. G. J., Wilder, S. C., Geisbush, T. R., Narayanaswami, P., Rutkove, S. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Age-+and+gender-associated+differences+in+electrical+impedance+values+of+skeletal+muscle.">Age- and gender-associated differences in electrical impedance values of skeletal muscle.</a> Physiological Measurement. 34 (12), 1611-1622 (2013).</li><li>Clark, B. C., Rutkove, S., Lupton, E. C., Padilla, C. J., Arnold, W. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Potential+utility+of+electrical+impedance+myography+in+evaluating+age-related+skeletal+muscle+function+deficits.">Potential utility of electrical impedance myography in evaluating age-related skeletal muscle function deficits.</a> Frontiers in Physiology. 12, 666964 (2021).</li><li>Kapur, K., 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=Predicting+myofiber+size+with+electrical+impedance+myography:+A+study+in+immature+mice.">Predicting myofiber size with electrical impedance myography: A study in immature mice.</a> Muscle and Nerve. 58 (1), 106-113 (2018).</li><li>Kapur, K., Nagy, J. A., Taylor, R. S., Sanchez, B., Rutkove, S. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Estimating+myofiber+size+with+electrical+impedance+myography:+a+study+in+amyotrophic+lateral+sclerosis+mice.">Estimating myofiber size with electrical impedance myography: a study in amyotrophic lateral sclerosis mice.</a> Muscle and Nerve. 58 (5), 713-717 (2018).</li><li>Mortreux, M., Semple, C., Riveros, D., Nagy, J. A., Rutkove, S. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrical+impedance+myography+for+the+detection+of+muscle+inflammation+induced+by+&#955;-carrageenan.">Electrical impedance myography for the detection of muscle inflammation induced by &#955;-carrageenan.</a> PLoS ONE. 14 (10), 0223265 (2019).</li><li>Pandeya, S. R., 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=Predicting+myofiber+cross-sectional+area+and+triglyceride+content+with+electrical+impedance+myography:+A+study+in+db/db+mice.">Predicting myofiber cross-sectional area and triglyceride content with electrical impedance myography: A study in db/db mice.</a> Muscle and Nerve. 63 (1), 127-140 (2021).</li><li>Pandeya, S. R., 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=Estimating+myofiber+cross-sectional+area+and+connective+tissue+deposition+with+electrical+impedance+myography:+A+study+in+D2-mdx+mice.">Estimating myofiber cross-sectional area and connective tissue deposition with electrical impedance myography: A study in D2-mdx mice.</a> Muscle &amp; Nerve. 63 (6), 941-950 (2021).</li><li>St&#229;lberg, E., 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=Standards+for+quantification+of+EMG+and+neurography.">Standards for quantification of EMG and neurography.</a> Clinical Neurophysiology. 130 (9), 1688-1729 (2019).</li><li>Theodorou, D. J., Theodorou, S. J., Kakitsubata, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Skeletal+muscle+disease:+Patterns+of+MRI+appearances.">Skeletal muscle disease: Patterns of MRI appearances.</a> British Journal of Radiology. 85 (1020), 1298-1308 (2012).</li><li>Simon, N. G., Noto, Y., Zaidman, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Skeletal+muscle+imaging+in+neuromuscular+disease.">Skeletal muscle imaging in neuromuscular disease.</a> Journal of Clinical Neuroscience. 33, 1-10 (2016).</li><li>Kwon, H., Rutkove, S. B., Sanchez, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recording+characteristics+of+electrical+impedance+myography+needle+electrodes.">Recording characteristics of electrical impedance myography needle electrodes.</a> Physiological Measurement. 38 (9), 1748-1765 (2017).</li><li>Kwon, H., Di Cristina, J. F., Rutkove, S. B., Sanchez, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recording+characteristics+of+electrical+impedance-electromyography+needle+electrodes.">Recording characteristics of electrical impedance-electromyography needle electrodes.</a> Physiological Measurement. 39 (5), 055005 (2018).</li><li>Rutkove, S. B., 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=Characterizing+spinal+muscular+atrophy+with+electrical+impedance+myography.">Characterizing spinal muscular atrophy with electrical impedance myography.</a> Muscle and Nerve. 42 (6), 915-921 (2010).</li><li>Schwartz, S., 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=Optimizing+electrical+impedance+myography+measurements+by+using+a+multifrequency+ratio:+A+study+in+Duchenne+muscular+dystrophy.">Optimizing electrical impedance myography measurements by using a multifrequency ratio: A study in Duchenne muscular dystrophy.</a> Clinical Neurophysiology. 126 (1), 202-208 (2015).</li><li>Li, J., Pacheck, A., Sanchez, B., Rutkove, S. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single+and+modeled+multifrequency+electrical+impedance+myography+parameters+and+their+relationship+to+force+production+in+the+ALS+SOD1G93A+mouse.">Single and modeled multifrequency electrical impedance myography parameters and their relationship to force production in the ALS SOD1G93A mouse.</a> Amyotrophic Lateral Sclerosis and Frontotemporal Degeneration. 17 (5-6), 397-403 (2016).</li><li>Hu, 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=Antisense+oligonucleotide+and+adjuvant+exercise+therapy+reverse+fatigue+in+old+mice+with+myotonic+dystrophy.">Antisense oligonucleotide and adjuvant exercise therapy reverse fatigue in old mice with myotonic dystrophy.</a> Molecular Therapy - Nucleic Acids. 23, 393-405 (2021).</li><li>Sanchez, B., 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=Non-invasive+assessment+of+muscle+injury+in+healthy+and+dystrophic+animals+with+electrical+impedance+myography.">Non-invasive assessment of muscle injury in healthy and dystrophic animals with electrical impedance myography.</a> Muscle &amp; Nerve. 56 (6), 85-94 (2017).</li><li>Sanchez, B., Li, J., Bragos, R., Rutkove, S. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differentiation+of+the+intracellular+structure+of+slow-+versus+fast-twitch+muscle+fibers+through+evaluation+of+the+dielectric+properties+of+tissue.">Differentiation of the intracellular structure of slow- versus fast-twitch muscle fibers through evaluation of the dielectric properties of tissue.</a> Physics in Medicine and Biology. 59 (10), 2369-2380 (2014).</li><li>Shefner, J. M., 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=Assessing+ALS+progression+with+a+dedicated+electrical+impedance+myography+system.">Assessing ALS progression with a dedicated electrical impedance myography system.</a> Amyotrophic Lateral Sclerosis &amp; Frontotemporal Degeneration. 19 (7-8), 555-561 (2018).</li><li>Lungu, C., 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=Quantifying+muscle+asymmetries+in+cervical+dystonia+with+electrical+impedance:+a+preliminary+assessment.">Quantifying muscle asymmetries in cervical dystonia with electrical impedance: a preliminary assessment.</a> Clinical Neurophysiology. 122 (5), 1027-1031 (2011).</li><li>Wang, Y., 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=Electrical+impedance+myography+for+assessing+paraspinal+muscles+of+patients+with+low+back+pain.">Electrical impedance myography for assessing paraspinal muscles of patients with low back pain.</a> Journal of Electrical Bioimpedance. 10 (1), 103-109 (2019).</li><li>Leitner, M. L., 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=Electrical+impedance+myography+for+reducing+sample+size+in+Duchenne+muscular+dystrophy+trials.">Electrical impedance myography for reducing sample size in Duchenne muscular dystrophy trials.</a> Annals of Clinical and Translational Neurology. 7 (1), 4-14 (2020).</li><li>Rutkove, S. B., 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=Improved+ALS+clinical+trials+through+frequent+at-home+self-assessment:+a+proof+of+concept+study.">Improved ALS clinical trials through frequent at-home self-assessment: a proof of concept study.</a> Annals of Clinical and Translational Neurology. 7 (7), 1148-1157 (2020).</li></ol>

S. B. Rutkove has equity in, and serves as a consultant and scientific advisor to, Myolex, Inc., a company that designs impedance devices for clinical and research use, and the mView system used here. He is also a member of the company's Board of Directors. The company also has an option to license patented impedance technology of which S. B. Rutkove is named as an inventor. The other authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

This article provides the basic methods for performing EIM in rodents, both in vivo and ex vivo. To acquire reliable measurements, it is critical to perform a series of steps. First, one needs to properly identify the muscle of interest, as each muscle will have different responses to diseases, treatment, and pathology. One must be mindful that the data acquired on one muscle (e.g., gastrocnemius) will not provide the same information as on another muscle (e.g., tibialis anterior). Second, one needs to ...

Electrical impedance myography (EIM) provides a powerful method to assess muscle condition, potentially enabling the diagnosis of neuromuscular disorders, tracking of disease progression, and assessment of response to therapy1,2,3. It can be applied analogously to animal disease models and humans, allowing for relatively seamless translation from preclinical to clinical studies. EIM measurements are easily obtained using four linearly-placed electrodes, with the two outer ones applying a painless, weak electrical current across a range of frequencies (generally between 1 kHz and approximately 2 MHz), and the two inner ones recording the resulting voltages1. From these voltages, the impedance characteristics of the tissue can be obtained, including the resistance (R), a measure of how difficult it is for current to pass through the tissue, and the reactance (X) or &#34;chargeability&#34; of the tissue, a measure related to the tissue&#39;s ability to store charge (capacitance). From the reactance and resistance, the phase angle (&#952;) is calculated via the following equation: <img alt="Equation 1" src="/files/ftp_upload/63513/63513eq01.jpg" style="margin: auto;" />, providing a single summative impedance measure. Such measurements can be obtained using any multifrequency bioimpedance device. As myofibers are essentially long cylinders, muscle tissue is also highly anisotropic, with current flowing more easily along fibers than across them4,5. Thus, EIM is often performed in two directions: with the array placed along the fibers such that current runs parallel to them, and across the muscle such that the current flows perpendicular to them. Additionally, in ex vivo measurements, where a known volume of tissue is measured in an impedance measuring cell, the inherent electrical properties of the muscle (i.e. the conductivity and relative permittivity), can be derived6.
The term &#34;neuromuscular disorders&#34; defines a wide range of primary and secondary diseases that lead to structural muscle alteration and dysfunction. This includes amyotrophic lateral sclerosis and various forms of muscular dystrophy, as well as simpler changes related to aging (e.g., sarcopenia), disuse atrophy (e.g., due to prolonged bedrest or microgravity) or even injury7. While the causes are plentiful and can originate from the motor neuron, nerves, neuromuscular junctions, or the muscle itself, EIM can be used to detect early alterations in muscle due to many of these processes and to track progression or response to therapy. For example, in patients with Duchenne muscular dystrophy (DMD), EIM has been shown to detect disease progression and response to corticosteroids8. Recent work has also shown EIM to be sensitive to varying disuse states, including fractional gravity9, as would be experienced on the Moon or Mars, and the effects of aging10,11. Finally, by applying predictive and machine learning algorithms to the data set obtained with each measurement (multifrequency and directionally dependent data), it becomes possible to infer histological aspects of the tissue, including myofiber size12,13, inflammatory changes and edema14, and connective tissue and fat content15,16.
Several other noninvasive or minimally invasive methods are also used to evaluate muscle health in humans and animals, including needle electromyography17 and imaging technologies such as magnetic resonance imaging, computerized tomography, and ultrasound18,19. However, EIM demonstrates distinct benefits compared with these technologies. For example, electromyography records only the active electrical properties of the myofiber membranes and not the passive properties, and thus cannot provide a true assessment of muscle composition or structure. In a certain respect, imaging methods are more closely related to EIM, as they too provide information about the structure and composition of tissue. But in some sense, they provide too much data, requiring detailed image segmentation and expert analysis rather than just providing a quantitative output. Moreover, given their complexities, imaging techniques are also greatly impacted by the specifics of both the hardware and software being used, ideally requiring the use of identical systems so that data sets can be compared. In contrast, the fact that EIM is much simpler means that it is less impacted by these technical issues and does not require any form of image processing or expert analysis.
The following protocol demonstrates how to perform in vivo EIM in rats and mice, using both noninvasive (surface array) and minimally invasive (subdermal needle array) techniques, as well as ex vivo EIM on freshly excised muscle.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>3D Printer</td>
			<td>Formlabs Inc.</td>
			<td>Form 2 Desktop</td>
			<td>3D printer</td>
		</tr>
		<tr>
			<td>3D Printer</td>
			<td>Shenzhen Creality 3D Technology Co. LTD</td>
			<td>Creality Ender 3 V2</td>
			<td>3D printer</td>
		</tr>
		<tr>
			<td>3M Micropore surgical tape</td>
			<td>Fisher</td>
			<td>19-027761 and 19-061655</td>
			<td>models 1530-0 and 1530-1</td>
		</tr>
		<tr>
			<td>3M TRANSPORE surgical tape</td>
			<td>Fisher</td>
			<td>18-999-380 and 18-999-381</td>
			<td>models 1527-0 and 1527-1</td>
		</tr>
		<tr>
			<td>Connector header vertical 10 POS 1 mm spacing</td>
			<td>Digi-Key (Sullins connector solution)</td>
			<td>S9214-ND (SMH100-LPSE-S10-ST-BK)</td>
			<td>Plastic spacer 1 mm holes for the rat in vivo array displayed in Figure 2A</td>
		</tr>
		<tr>
			<td>Cotton-tipped applicators</td>
			<td>Fisher</td>
			<td>22-363-172</td>
			<td></td>
		</tr>
		<tr>
			<td>Dental Wax</td>
			<td>Fisher</td>
			<td>NC9377103</td>
			<td></td>
		</tr>
		<tr>
			<td>Depilatory agent</td>
			<td>NAIR</td>
			<td>NA</td>
			<td>hair remover lotion with softening baby oil</td>
		</tr>
		<tr>
			<td>Dumont #7b Forceps</td>
			<td>Fine Science Tools</td>
			<td>No. 11270-20</td>
			<td>Used for dissection, Style: #7b, Tip Shape: Curved, Tips: Standard, Tip Dimensions: 0.17 mm x 0.1 mm, Alloy/Material: Inox, Length: 11 cm</td>
		</tr>
		<tr>
			<td>Electronic Digital Caliper</td>
			<td>Fisher</td>
			<td>14-648-17</td>
			<td>Used to measure out the dimensions of the Gastrocnemius muscle</td>
		</tr>
		<tr>
			<td>Epoxy adhesive dual cartridge 4 min work life</td>
			<td>Devcon</td>
			<td>series 14265, model 2217</td>
			<td>Glue used in the rat in vivo array displayed in Figure 2A</td>
		</tr>
		<tr>
			<td>Ex vivo dielectric impedance cell</td>
			<td>Custom</td>
			<td>NA</td>
			<td>Dielectric cells were 3D printed in the Rutkove laboratory</td>
		</tr>
		<tr>
			<td>Graefe Forceps</td>
			<td>Fine Science Tools</td>
			<td>No. 11051-10</td>
			<td>Used for muscle to place and adjust, Length: 10 cm, Tip Shape: Curved, Tips: Serrated, Tip Width: 0.8 mm, Tip Dimensions: 0.8 mm x 0.7 mm, Alloy/Material</td>
		</tr>
		<tr>
			<td>Hair clipper</td>
			<td>Amazon</td>
			<td>NA</td>
			<td>Wahl professional animal BravMini+</td>
		</tr>
		<tr>
			<td>Impedance Animal Device</td>
			<td>Myolex</td>
			<td>EIM1103</td>
			<td>mView system - investigational electrical impedance myography device for use in animal research</td>
		</tr>
		<tr>
			<td>In vivo needle arrays</td>
			<td>Custom</td>
			<td>NA</td>
			<td>Custom arrays using 27 G subdermal needles from Ambu. The construction was finalized using a 3D printer in the Rutkove laboratory</td>
		</tr>
		<tr>
			<td>In vivo surface array</td>
			<td>Custom</td>
			<td>NA</td>
			<td>The in vivo surface array was printed and assembled in the Rutkove laboratory</td>
		</tr>
		<tr>
			<td>Isoflurane</td>
			<td>Patterson Veterinary Supplies</td>
			<td>07-893-8441 (NDC: 46066-755-04)</td>
			<td>Pivetal - 250 mL bottle</td>
		</tr>
		<tr>
			<td>Non-woven gauze</td>
			<td>Fisher</td>
			<td>22-028-559</td>
			<td>2 x 2 inch</td>
		</tr>
		<tr>
			<td>Polystyrene Weighing Dishes</td>
			<td>Fisher</td>
			<td>S67090A</td>
			<td>Dimensions (L x W x H): 88.9 mm x 88.9 mm x 25.4 mm</td>
		</tr>
		<tr>
			<td>Razor Blades</td>
			<td>Fisher</td>
			<td>12-640</td>
			<td>Used to cut muscle to right dimensions, Single-edge carbon steel blades</td>
		</tr>
		<tr>
			<td>Student Fine Scissors</td>
			<td>Fine Science Tools</td>
			<td>No. 91460-11</td>
			<td>Used for dissection, Tips: Sharp-Sharp, Alloy/Material: Student Stainless Steel, Serrated: No, Tip Shape: Straight, Cutting Edge: 20 mm, Length: 11.5 cm, Feature: Student Quality</td>
		</tr>
		<tr>
			<td>Subdermal needles 27 G Neuroline</td>
			<td>Ambu</td>
			<td>745 12-50/24</td>
			<td>Needles used in the rat in vivo array displayed in Figure 2A</td>
		</tr>
		<tr>
			<td>Surgical Scissors - Sharp</td>
			<td>Fine Science Tools</td>
			<td>No. 14002-13</td>
			<td>Used to cut skin, Tips: Sharp-Sharp, Alloy/Material: Stainless Steel, Serrated: No, Tip Shape: Straight, Cutting Edge: 42 mm, Length: 13 cm</td>
		</tr>
		<tr>
			<td>TECA ELITE monopolar needle electrodes</td>
			<td>Natus</td>
			<td>902-DMG50-S</td>
			<td>0.46 mm diameter (26 G). Blue hub</td>
		</tr>
		<tr>
			<td>Teknova 0.9% saline solution</td>
			<td>Fisher</td>
			<td>S5815</td>
			<td>1000 mL sterile</td>
		</tr>
	</tbody>
</table>

performing in vivo and ex vivo electrical impedance myography in rodents

Electrical impedance myography (EIM) is a convenient technique that can be used in preclinical and clinical studies to assess muscle tissue health and disease. EIM is obtained by applying a low-intensity, directionally focused, electrical current to a muscle of interest across a range of frequencies (i.e., from 1 kHz to 10 MHz) and recording the resulting voltages. From these, several standard impedance components, including the reactance, resistance, and phase, are obtained. When performing ex vivo measurements on excised muscle, the inherent passive electrical properties of the tissue, namely the conductivity and relative permittivity, can also be calculated. EIM has been used extensively in animals and humans to diagnose and track muscle alterations in a variety of diseases, in relation to simple disuse atrophy, or as a measure of therapeutic intervention. Clinically, EIM offers the potential to track disease progression over time and to assess the impact of therapeutic interventions, thus offering the opportunity to shorten the clinical trial duration and reduce sample size requirements. Because it can be performed noninvasively or minimally invasively in living animal models as well as humans, EIM offers the potential to serve as a novel translational tool enabling both preclinical and clinical development. This article provides step-by-step instructions on how to perform in vivo and ex vivo EIM measurements in mice and rats, including approaches to adapt the techniques to specific conditions, such as for use in pups or obese animals.

EIM can be obtained in many conditions, including surface in vivo arrays (Figure 1), needle in vivo arrays (Figure 2A-F), and ex vivo dielectric cells (Figure 2G,H).
EIM provides a near-instantaneous snapshot of the muscle condition based on the measured impedance values. Measurements are acquired swiftly and result in a simple ...

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Performing In Vivo and Ex Vivo Electrical Impedance Myography in Rodents

This article details how to perform in vivo (using surface and needle electrode arrays) and ex vivo (using a dielectric cell) electrical impedance myography on the rodent gastrocnemius muscle. It will demonstrate the technique in both mice and rats and detail the modifications available, (i.e., obese animals, pups).

Performing In Vivo and Ex Vivo Electrical Impedance Myography in Rodents

Electrical impedance myography (EIM) is a convenient technique that can be used in preclinical and clinical studies to assess muscle tissue health and ...

Electrical Impedance Myography is a none or minimally invasive technique for assessing muscle condition. It provides a quantitative index of muscle health serving as a diagnostic tool or biomarker. So technique is quantitative, rapid, and does not require detailed image analysis so it can serve as a convenient biomarker of disease status in a therapeutic study.Another useful aspect of Electrical Impedance Myography is that it is sensitive to most types of skeletal muscle pathology. Abnormal Electrical Impedance Myography values can reveal underlying histological alterations. For surface measurements, the skin needs to be prepared well.One has to become familiar with the appearance of contact impedance artifacts and remeasure if needed. To begin, place the mouse on the bench in a prone position after confirming the absence of response during the toe pinching test. Place the animal's leg to be analyzed at a 45 degree angle with the knee extended and secure the foot with medical tape.Trim the fur overlaying the gastrocnemius muscle using a hair clipper, and apply a thick layer of depilatory cream over the animal's skin for one minute. Remove the depilatory agent using the saline saturated gauze and repeat this process up to three times until all the fur overlaying the gastrocnemius muscle is removed. Connect the surface array to the Electrical Impedance Myography device and let the electrodes rest on a piece of gauze soaked in saline solution.Place the surface array directly on the skin, over the gastrocnemius muscle oriented longitudinally to the muscle fibers. Check for appropriate contact by checking that all the bars appear green on the software with the stability of the 50 kilohertz resistance, reactance, and phase values. Then acquire the Electrical Impedance Myography measurements.Rotate the surface array by 90 degrees and reposition it on the skin over the gastrocnemius to obtain the transverse measurements. Connect the needle array to the Electrical Impedance Myography device and let the electrode array rest in a weighing boat containing saline solution. Then check for connectivity and signal stability.Place the needle array in a longitudinal position compared to the my fibers, and press it firmly into the skin until all the needles penetrate the skin and the underlying muscle up to the plastic guard on the array. Acquire the data. Gently remove the array and reinsert it through the skin and into the muscle at a 90 degree angle relative to the first measurement in the transverse direction.Then acquire this data. For Ex Vivo Electrical Impedance Myography, prepare the ex vivo dielectric cell, add saline solution to the chamber and connect the cell to the Electrical Impedance Myography device to obtain the reference values. Place the gastrocnemius muscle on a sheet of dental wax and section it using a razor blade in a ruler to obtain a 10 millimeter by 10 millimeter section for rats.And five millimeter by five millimeter section for mice from the center of the gastrocnemius muscle. Gently place the gastrocnemius in the dialectric cells using tweezers, making sure the fibers are oriented longitudinally and the muscle is entirely in contact with the metal electrodes. Attach the top part of the dialectric cell and insert two monopolar needles of 26 gauge into the two holes.Connect the wires from the Electrical Impedance Myography device to the ex vivo cell in the order mentioned in the manuscript. Then acquire the longitudinal measurement. Open the dialectric cell and reorient the muscle in the transverse direction by rotating it 90 degrees.Reattach the top of the dialectric cell and acquire the transverse measurement. Electrical Impedance Myography can be obtained in many conditions with surface in vivo arrays, needle in vivo arrays, and ex vivo dialectric cells. Representative curves for surface E I M are shown for phase, reactance and resistance for longitudinal in transverse measurements.Some irregularities, which are typically related to contact issues can result in extreme values observed at low frequencies. A graph showing the reactance as a resistance function and longitudinal and transverse directions is displayed. Good skin preparation is crucial for surface measurements.There can be no fur remaining. Repeat fur removal, saline application and measurement if contact artifact is identified. Electrical Impedance Myography allows enhanced assessment of disease status and therapy effects in rodent models helping to speed the identification of promising new therapies for the treatment of neuromuscular diseases.

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JoVE Journal

Biology

2.7K Views.  Harvard Medical School - Beth Israel Deaconess Medical Center. Electrical Impedance Myography is a none or minimally invasive technique for assessing muscle condition. It provides a quantitative index of muscle health serving as a diagnostic tool or biomarker. So technique is quantitative, rapid, and does not require detailed image analysis so it can serve as a convenient biomarker of disease status in a therapeutic study.Another useful aspect of Electrical Impedance Myography is that it is sensitive to most types of skeletal muscle pathology. Abn...