• View in gallery

    Transverse CT image of a healthy Labrador Retriever showing measurement of CT attenuation values (HU) of the left epaxial muscles over the T13 vertebral body. A freehand closed polygon tool was used to draw around the outer margin of the left epaxial muscles on each transverse image obtained from the cranial to caudal endplates of T13. The CT attenuation values from every voxel from within those regions of interest were exported from the DICOM software as a single dataset in an extensible markup language file, and mean CT attenuation values were calculated.

  • View in gallery

    Transverse CT images of the epaxial muscles at the level of T13 in a healthy 10-year-old Labrador Retriever (A) and a healthy 4-year-old Labrador Retriever (B). Mean CT attenuation values for the measured left epaxial muscle regions were 37.4 and 58.2 HU, respectively. The muscle in the old dog is less uniform in appearance, with a greater number of poorly defined hypoattenuating regions, reflected quantitatively by a higher SD for these measurements (31.8 in the older dog, compared with 20.6 in the younger dog).

  • 1. Lang T, Streeper T, Cawthon P, et al. Sarcopenia: etiology, clinical consequences, intervention, and assessment. Osteoporos Int 2010;21:543559.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 2. Freeman LM. Cachexia and sarcopenia: emerging syndromes of importance in dogs and cats. J Vet Intern Med 2012;26:317.

  • 3. Meyer J, Stadtfeld G. Investigation on the body and organ structure of dogs. In: Anderson RS, ed. Nutrition of the dog and cat. Oxford, England: Pergamon Press, 1980;1530.

    • Search Google Scholar
    • Export Citation
  • 4. Harper EJ. Changing perspectives on aging and energy requirements: aging, body weight and body composition in humans, dogs and cats. J Nutr 1998;128:2627S2631S.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5. Kealy RD, Lawler DF, Ballam JM, et al. Effects of diet restriction on life span and age-related changes in dogs. J Am Vet Med Assoc 2002;220:13151320.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6. Hutchinson D, Sutherland-Smith J, Watson AL. eg al. Assessment of methods of evaluating sarcopenia in old dogs. Am J Vet Res 2012;73:17941800.

  • 7. McGregor RA, Cameron-Smith D, Poppitt SD. It is not just muscle mass: a review of muscle quality, composition and metabolism during ageing as determinants of muscle function and mobility in later life. Longev Healthspan 2014;3:9.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 8. Chan OY, van Houwelingen AH, Gussekloo J, et al. Comparison of quadriceps strength and handgrip strength in their association with health outcomes in older adults in primary care. Age (Dordr) 2014;36:9714.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 9. Pagano TB, Wojcik S, Costagliola A, et al. Age related skeletal muscle atrophy and upregulation of autophagy in dogs. Vet J 2015;206:5460.

  • 10. Hua J, Hoummady S, Muller C, et al. Assessment of frailty in aged dogs. Am J Vet Res 2016;77:13571365.

  • 11. Visser M, Kritchevsky SB, Goodpaster BH, et al. Leg muscle mass and composition in relation to lower extremity performance in men and women aged 70 to 79: the health, aging and body composition study. J Am Geriatr Soc 2002;50:897904.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 12. Delmonico MJ, Harris TB, Visser M, et al. Longitudinal study of muscle strength, quality, and adipose tissue infiltration. Am J Clin Nutr 2009;90:15791585.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 13. Sergi G, Trevisan C, Veronese N, et al. Imaging of sarcopenia. Eur J Radiol 2016;85:15191524.

  • 14. Michel KE, Anderson W, Cupp C, et al. Correlation of a feline muscle mass score with body composition determined by dual-energy X-ray absorptiometry. Br J Nutr 2011;106:S57S59.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 15. World Small Animal Veterinary Association Global Nutrition Committee. Muscle condition score charts for dogs and cats. Available at: www.wsava.org/Guidelines/Global-Nutrition-Guidelines. Accessed Apr 21, 2018.

    • Search Google Scholar
    • Export Citation
  • 16. Freeman LM, Sutherland-Smith J, Prantil LR, et al. Quantitative assessment of muscle in dogs using a vertebral epaxial muscle score. Can J Vet Res 2017;81:255260.

    • Search Google Scholar
    • Export Citation
  • 17. Freeman LM, Sutherland-Smith J, Cummings C, et al. Evaluation of a quantitative ultrasound technique for assessment of muscle mass in normal cats. Am J Vet Res 2018;79:11881192.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 18. Goodpaster BH, Kelley DE, Thaete FL, et al. Skeletal muscle attenuation determined by computed tomography is associated with skeletal muscle lipid content. J Appl Physiol 2000;89:104110.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 19. Zoico E, Rossi A, Di Francesco V, et al. Adipose tissue infiltration in skeletal muscle of healthy elderly men: relationships with body composition, insulin resistance, and inflammation at the systemic and tissue level. J Gerontol A Biol Sci Med Sci 2010;65:295299.

    • Search Google Scholar
    • Export Citation
  • 20. Tieland M, Trouwborst I, Clark BC. Skeletal muscle performance and ageing. J Cachexia Sarcopenia Muscle 2018;9:319.

  • 21. Boutin RD, Yao L, Canter RJ, et al. Sarcopenia: current concepts and imaging implications. AJR Am J Roentgenol 2015;205:W255W266.

  • 22. Boström AF, Lappalainen AK, Danneels L, et al. Cross-sectional area and fat content in dachshund epaxial muscles: an MRI and CT reliability study. Vet Rec Open 2018;5:e000256.

    • Search Google Scholar
    • Export Citation
  • 23. Boström AF, Hielm-Bjorkman AK, Chang YM, et al. Comparison of cross sectional area and fat infiltration of the epaxial muscles in dogs with and without spinal cord compression. Res Vet Sci 2014;97:646651.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 24. Laflamme D. Development and validation of a body condition score system for dogs. Canine Pract 1997;22:1015.

  • 25. Oliveira CR, Ranallo FN, Pijanowski GJ, et al. The VetMousetrap: a device for computed tomographic imaging of the thorax of awake cats. Vet Radiol Ultrasound 2011;52:4152.

    • Search Google Scholar
    • Export Citation

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Comparison of computed tomographic attenuation values for epaxial muscles in old and young dogs

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  • 1 Department of Clinical Sciences, Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA 01536.
  • | 2 Department of Clinical Sciences, Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA 01536.
  • | 3 Department of Clinical Sciences, Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA 01536.

Abstract

OBJECTIVE To determine whether the degree of CT attenuation of muscle would differ between healthy old and young dogs.

ANIMALS 10 healthy old (> 8 years old) and 9 healthy young (1 to 5 years old) Labrador Retrievers with a body condition score of 5 or 6 on a 9-point scale.

PROCEDURES CT was performed with the dogs mildly sedated. A freehand closed polygon tool was used to define the outer margin of the left epaxial muscles on each transverse image obtained from the cranial to caudal endplates of T13. The CT attenuation values from every voxel from within these regions of interest were exported from DICOM software as a single dataset in an extensible markup language file. From these data, mean CT attenuation values were calculated for each dog and these mean values were compared between age groups.

RESULTS Mean CT attenuation values for the epaxial muscles were significantly lower in old dogs than in young dogs. A significant negative correlation (r = –0.74) was identified between mean CT attenuation values and dog age.

CONCLUSIONS AND CLINICAL RELEVANCE In addition to loss of skeletal muscle mass, low muscle CT attenuation values suggested that the old dogs in this study also had greater muscle fat content than did young dogs. Additional studies are warranted to evaluate qualitative and quantitative muscle changes in old dogs.

Abstract

OBJECTIVE To determine whether the degree of CT attenuation of muscle would differ between healthy old and young dogs.

ANIMALS 10 healthy old (> 8 years old) and 9 healthy young (1 to 5 years old) Labrador Retrievers with a body condition score of 5 or 6 on a 9-point scale.

PROCEDURES CT was performed with the dogs mildly sedated. A freehand closed polygon tool was used to define the outer margin of the left epaxial muscles on each transverse image obtained from the cranial to caudal endplates of T13. The CT attenuation values from every voxel from within these regions of interest were exported from DICOM software as a single dataset in an extensible markup language file. From these data, mean CT attenuation values were calculated for each dog and these mean values were compared between age groups.

RESULTS Mean CT attenuation values for the epaxial muscles were significantly lower in old dogs than in young dogs. A significant negative correlation (r = –0.74) was identified between mean CT attenuation values and dog age.

CONCLUSIONS AND CLINICAL RELEVANCE In addition to loss of skeletal muscle mass, low muscle CT attenuation values suggested that the old dogs in this study also had greater muscle fat content than did young dogs. Additional studies are warranted to evaluate qualitative and quantitative muscle changes in old dogs.

Sarcopenia, the age-related loss of skeletal muscle mass, is a multifactorial condition affecting both companion animals and humans.1,2 Although this condition has received less scientific evaluation in dogs than it has in humans, several studies have revealed lower total body protein,3 lean body mass,4,5 or muscle mass6 in old versus younger dogs. In humans, mechanisms for loss of muscle mass include physical inactivity, an increase in cytokine production, decreases in circulating hormone concentrations (including growth hormone, testosterone, and insulinlike growth factor-1) and muscle protein synthesis, and suboptimal nutrition.1,7,8 Little evidence exists that the mechanisms for age-related muscle loss in dogs are similar to those in humans, although results of 1 study9 suggested that autophagy may contribute to sarcopenia in dogs as they age.

In humans, sarcopenia has several adverse effects, including weakness, immobility, falls, fractures, and functional limitations, with impacts on well-being and quality of life.1,8 Although the focus was not on sarcopenia specifically, a study10 involving dogs showed that those identified as frail through clinical geriatric assessment had a significantly higher risk of death than dogs not identified as frail. Additional research is needed into the clinical effects of sarcopenia in old dogs and cats.

The most common methods of identifying sarcopenia in humans are measurement of the cross-sectional area of thigh or epaxial (paraspinal) muscle via CT.1,11–13 Loss of skeletal muscle mass in dogs and cats can be identified clinically by use of a subjective MCS system.14,15 More recently, muscle mass has been assessed in dogs and cats through measurement of epaxial muscle size by use of ultrasonography or CT.6,16,17

In addition to quantitative reductions in muscle mass, qualitative changes in muscle also occur during aging. Humans have a switch from type I to type II muscle fibers, loss of α motor neuron innervation, fibrosis, insulin resistance, and fat infiltration.1,7,18–20 The increase in intramuscular fat in elderly humans is represented by a decrease in muscle density, as evidenced by lower muscle CT attenuation values.18 Therefore, measurement of muscle CT attenuation values, usually of the epaxial muscles specifically, is now being used to assess muscle fat accumulation during aging in humans.12,13,21 This method is commonly used for detection of sarcopenia because CT scans are routinely performed in human medicine for various medical conditions.

High intrarater and interrater agreement has been reported for measurement of CT attenuation values for epaxial muscles in healthy young Dachshunds.22 In another study23 from the same research group, Dachshunds with intervertebral disk herniation had lower muscle CT attenuation values, suggesting more fat infiltration, than did dogs of various breeds with fibrocartilaginous embolism. To the authors’ knowledge, no muscle CT attenuation values have been reported for old versus young dogs. Such information would be useful to determine whether aging dogs have similar muscle changes to aging humans and whether CT could be used to assess these changes as a measure of muscle fat infiltration. Therefore, the objective of the study reported here was to measure CT attenuation values for muscle in healthy old and young dogs. The hypothesis was that healthy old dogs would have lower CT attenuation values for epaxial muscles than those of healthy young dogs.

Materials and Methods

Dogs

The CT images obtained in a previously reported study6 were used for the present study. In that study, 20 healthy young (1 to 5 years) and old (> 8 years) Labrador Retrievers owned by staff members and clients of the Foster Hospital for Small Animals were enrolled with owner consent; however, only 19 dogs (9 young dogs [mean ± SD age, 2.4 ± 1.0 years; 5 spayed females and 4 castrated males] and 10 old dogs [9.1 ± 1.2 years; 8 spayed females and 2 castrated males]) were included. To be eligible for inclusion in that study, dogs were required to have a BCS of 5 to 6 on a 9-point scale24 and to be in good health as determined from their medical history and results of physical examination, CBC, serum biochemical analysis, and urinalysis. Dogs were excluded when they had a history of orthopedic surgery or osteoarthritis or were receiving prescription or over-the-counter medications or supplements. The study protocol was approved by the Tufts Clinical Studies Review Committee.

Body composition measurements

In the previous study,6 all dogs were weighed on the same scale to the nearest 0.1 kg. A BCS25 and MCS15 were assigned to each dog by the same investigator (DH). Although the MCS system is descriptive rather than numeric,15 for the purposes of analysis, normal muscle condition was assigned a score of 0, mild muscle loss a score of 1, moderate muscle loss a score of 2, and severe muscle loss a score of 3.

CT scanning

In preparation for CT scanning, young dogs had been lightly sedated with dexmedetomidine,a butorphanol,b and midazolamc and old dogs had been lightly sedated with a combination of butorphanol,b acepromazine,d and glycopyrrolate.e Propofolf had been administered as needed to maintain sedation. Drugs were administered via an IV catheter. The same investigator (DH) had positioned the dogs in sternal recumbency with sandbag immobilization of the limbs.

The CT data were acquired by use of a 16-slice helical scanner.g Following the acquisition of 2 initial scout views, the helical volume was measured between the mid-T12 to mid-L3 vertebral bodies.6 The total time each dog spent in the CT scan room was < 15 minutes, and the total image acquisition time was < 20 seconds. Transverse 1-mm-thick slices were reconstructed by use of bone and soft tissue algorithms and exported in DICOM format.

CT attenuation measurements

The CT attenuation values (HU) for the left epaxial (paravertebral) muscles over the T13 vertebral body were measured by use of DICOM viewing software.h To do this, a freehand closed polygon tool was used to draw around the outer margin of the left epaxial muscles on each transverse image obtained from the cranial to caudal endplates of T13 (Figure 1). The T13 location was chosen because of the recognizable anatomic features at the thoracolumbar junction on transverse CT images and to reduce the potential influence of subclinical orthopedic disease. A median of 27 (range, 24 to 31) regions of interest were drawn for each dog. The CT attenuation values from every voxel from within these regions of interest were exported from the DICOM software as a single dataset in an extensible markup language file. From these data, mean CT attenuation values and their SDs were calculated.

Figure 1—
Figure 1—

Transverse CT image of a healthy Labrador Retriever showing measurement of CT attenuation values (HU) of the left epaxial muscles over the T13 vertebral body. A freehand closed polygon tool was used to draw around the outer margin of the left epaxial muscles on each transverse image obtained from the cranial to caudal endplates of T13. The CT attenuation values from every voxel from within those regions of interest were exported from the DICOM software as a single dataset in an extensible markup language file, and mean CT attenuation values were calculated.

Citation: American Journal of Veterinary Research 80, 2; 10.2460/ajvr.80.2.174

Statistical analysis

Data distributions were evaluated graphically and with the Shapiro-Wilk test. Normally distributed data are reported as mean ± SD and were compared between young and old dogs by use of the independent t test. Nonnormally distributed data are reported as median (range) and were compared between age groups with the Mann-Whitney U test. Correlations between age and mean muscle CT attenuation values were examined by use of the Pearson correlation test. Statistical softwarei was used for all analyses, and values of P < 0.05 were considered significant.

Results

Neither body weight nor BCS differed significantly between the 9 young Labrador Retrievers (mean ± SD values, 31.5 ± 5.4 kg and 5.4 ± 0.5, respectively) and the 10 old Labrador Retrievers (30.1 ± 5.1 kg and 5.7 ± 0.4, respectively). However, MCSs were significantly (P < 0.001) greater (suggesting more muscle loss) for old dogs (median, 1.3 [range, 0.5 to 2.0]) than for young dogs (0 for all).

Mean CT attenuation values for the left epaxial muscles were significantly (P = 0.005) lower in old dogs (mean ± SD, 47.1 ± 6.5 HU) than in young dogs (55.5 ± 4.4 HU; Figure 2). A significant (P < 0.001) negative correlation was identified between these mean CT attenuation values and age (r = −0.74; Supplementary Figure S1, available at avmajournals.avma.org/doi/suppl/10.2460/ajvr.80.2.174). Mean SDs for the CT attenuation values for individual dogs were 28.8 ± 5.8 HU (mean ± SD) for old dogs and 24.9 ± 4.7 HU for young dogs (P = 0.13).

Figure 2—
Figure 2—

Transverse CT images of the epaxial muscles at the level of T13 in a healthy 10-year-old Labrador Retriever (A) and a healthy 4-year-old Labrador Retriever (B). Mean CT attenuation values for the measured left epaxial muscle regions were 37.4 and 58.2 HU, respectively. The muscle in the old dog is less uniform in appearance, with a greater number of poorly defined hypoattenuating regions, reflected quantitatively by a higher SD for these measurements (31.8 in the older dog, compared with 20.6 in the younger dog).

Citation: American Journal of Veterinary Research 80, 2; 10.2460/ajvr.80.2.174

Discussion

In the present study, healthy old Labrador Retrievers had significantly lower mean CT attenuation values for the epaxial muscles at the evaluated location than did healthy young Labrador Retrievers. Given information from research in human medicine,18 this finding may suggest greater fat content of muscle, although such a suggestion would need to be confirmed. The finding of lower muscle CT attenuation values in old versus young dogs, in combination with previously reported findings6 of smaller normalized epaxial muscle area on CT imaging and lower normalized epaxial muscle height on ultrasonography, suggested that dogs have both quantitative and qualitative changes in muscle as they age. Such aging-related changes would be similar to reported findings for aging humans, in whom both loss of muscle mass and changes in muscle quality occurs.1,7,8,12 Such CT-detected changes are believed to reflect infiltration of the muscle with fat, as previously demonstrated by comparison of CT attenuation values with results of histologic examination of muscle biopsy specimens.18 Muscle condition scoring, the most common method for assessing muscle in dogs clinically, appears insensitive to these more qualitative muscle changes.

If dogs indeed have fat infiltration of muscle as they age, this could adversely affect muscle function, as it does in humans.1,7,8,12 Additional research is needed to evaluate the functional manifestations associated with the quantitative and qualitative muscle changes during the aging process in dogs.

The present study had several limitations that are important to consider. To reduce the impact of variation among breeds on our findings, only CT scans from Labrador Retrievers were used, and it remains unknown whether our findings might apply to other dog breeds as well. In previous research involving Dachshunds,23 differences in muscle CT attenuation values were identified between dogs of various breeds with fibrocartilaginous embolism and Dachshunds with intervertebral disk herniation, but it was unclear whether these differences were due to the underlying disease or to age or breed differences. Also, all dogs included in the present study were healthy and neutered, with a BCS of 5 to 6/9, and so additional research is needed into muscle CT attenuation values in other canine populations. Although considerable effort had originally been made to ensure the dogs included in the present study were indeed healthy, the possibility remained that some may have had subclinical disease (eg, cancer) that went undetected through medical history taking, physical examination, and laboratory testing. Finally, although CT examination of dogs may be uncommon owing to financial cost and the need for sedation or anesthesia, faster scan times and noninvasive methods for restraint25 can make CT a more feasible technique to diagnose and evaluate muscle changes in older dogs and cats.

Acknowledgments

Funded by the Barkley Fund and the National Center for Advancing Translational Sciences, National Institutes of Health (award No. UL1TR001064).

The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.

Presented in abstract form at the 10th International Conference on Cachexia, Sarcopenia, and Muscle Wasting, Rome, December 2017.

The authors thank Amanda Oppold for assistance in the preparation of this manuscript.

ABBREVIATIONS

BCS

Body condition score

MCS

Muscle condition score

Footnotes

a.

Dexdomitor, Pfizer Animal Health, New York, NY.

b.

Torbugesic, Fort Dodge Animal Health, Fort Dodge, Iowa.

c.

Midazolam, Hospira, Lake Forest, Ill.

d.

AceproJect, Butler Animal Health Supply, Dublin, Ohio.

e.

Glycopyrolate, American Regent, Shirley, NY.

f.

Propofol, Hospira, Lake Forest, Ill.

g.

Acquilion 16, Toshiba America Medical Systems, Tustin, Calif.

h.

Horos, version 2.4.1, The Horos Project. Available at www.horosproject.org. Accessed Jun 2, 2017.

i.

Systat, version 12.0, SPSS Inc, Chicago, Ill.

References

  • 1. Lang T, Streeper T, Cawthon P, et al. Sarcopenia: etiology, clinical consequences, intervention, and assessment. Osteoporos Int 2010;21:543559.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 2. Freeman LM. Cachexia and sarcopenia: emerging syndromes of importance in dogs and cats. J Vet Intern Med 2012;26:317.

  • 3. Meyer J, Stadtfeld G. Investigation on the body and organ structure of dogs. In: Anderson RS, ed. Nutrition of the dog and cat. Oxford, England: Pergamon Press, 1980;1530.

    • Search Google Scholar
    • Export Citation
  • 4. Harper EJ. Changing perspectives on aging and energy requirements: aging, body weight and body composition in humans, dogs and cats. J Nutr 1998;128:2627S2631S.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5. Kealy RD, Lawler DF, Ballam JM, et al. Effects of diet restriction on life span and age-related changes in dogs. J Am Vet Med Assoc 2002;220:13151320.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6. Hutchinson D, Sutherland-Smith J, Watson AL. eg al. Assessment of methods of evaluating sarcopenia in old dogs. Am J Vet Res 2012;73:17941800.

  • 7. McGregor RA, Cameron-Smith D, Poppitt SD. It is not just muscle mass: a review of muscle quality, composition and metabolism during ageing as determinants of muscle function and mobility in later life. Longev Healthspan 2014;3:9.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 8. Chan OY, van Houwelingen AH, Gussekloo J, et al. Comparison of quadriceps strength and handgrip strength in their association with health outcomes in older adults in primary care. Age (Dordr) 2014;36:9714.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 9. Pagano TB, Wojcik S, Costagliola A, et al. Age related skeletal muscle atrophy and upregulation of autophagy in dogs. Vet J 2015;206:5460.

  • 10. Hua J, Hoummady S, Muller C, et al. Assessment of frailty in aged dogs. Am J Vet Res 2016;77:13571365.

  • 11. Visser M, Kritchevsky SB, Goodpaster BH, et al. Leg muscle mass and composition in relation to lower extremity performance in men and women aged 70 to 79: the health, aging and body composition study. J Am Geriatr Soc 2002;50:897904.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 12. Delmonico MJ, Harris TB, Visser M, et al. Longitudinal study of muscle strength, quality, and adipose tissue infiltration. Am J Clin Nutr 2009;90:15791585.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 13. Sergi G, Trevisan C, Veronese N, et al. Imaging of sarcopenia. Eur J Radiol 2016;85:15191524.

  • 14. Michel KE, Anderson W, Cupp C, et al. Correlation of a feline muscle mass score with body composition determined by dual-energy X-ray absorptiometry. Br J Nutr 2011;106:S57S59.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 15. World Small Animal Veterinary Association Global Nutrition Committee. Muscle condition score charts for dogs and cats. Available at: www.wsava.org/Guidelines/Global-Nutrition-Guidelines. Accessed Apr 21, 2018.

    • Search Google Scholar
    • Export Citation
  • 16. Freeman LM, Sutherland-Smith J, Prantil LR, et al. Quantitative assessment of muscle in dogs using a vertebral epaxial muscle score. Can J Vet Res 2017;81:255260.

    • Search Google Scholar
    • Export Citation
  • 17. Freeman LM, Sutherland-Smith J, Cummings C, et al. Evaluation of a quantitative ultrasound technique for assessment of muscle mass in normal cats. Am J Vet Res 2018;79:11881192.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 18. Goodpaster BH, Kelley DE, Thaete FL, et al. Skeletal muscle attenuation determined by computed tomography is associated with skeletal muscle lipid content. J Appl Physiol 2000;89:104110.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 19. Zoico E, Rossi A, Di Francesco V, et al. Adipose tissue infiltration in skeletal muscle of healthy elderly men: relationships with body composition, insulin resistance, and inflammation at the systemic and tissue level. J Gerontol A Biol Sci Med Sci 2010;65:295299.

    • Search Google Scholar
    • Export Citation
  • 20. Tieland M, Trouwborst I, Clark BC. Skeletal muscle performance and ageing. J Cachexia Sarcopenia Muscle 2018;9:319.

  • 21. Boutin RD, Yao L, Canter RJ, et al. Sarcopenia: current concepts and imaging implications. AJR Am J Roentgenol 2015;205:W255W266.

  • 22. Boström AF, Lappalainen AK, Danneels L, et al. Cross-sectional area and fat content in dachshund epaxial muscles: an MRI and CT reliability study. Vet Rec Open 2018;5:e000256.

    • Search Google Scholar
    • Export Citation
  • 23. Boström AF, Hielm-Bjorkman AK, Chang YM, et al. Comparison of cross sectional area and fat infiltration of the epaxial muscles in dogs with and without spinal cord compression. Res Vet Sci 2014;97:646651.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 24. Laflamme D. Development and validation of a body condition score system for dogs. Canine Pract 1997;22:1015.

  • 25. Oliveira CR, Ranallo FN, Pijanowski GJ, et al. The VetMousetrap: a device for computed tomographic imaging of the thorax of awake cats. Vet Radiol Ultrasound 2011;52:4152.

    • Search Google Scholar
    • Export Citation

Supplementary Materials

Contributor Notes

Address correspondence to Dr. Sutherland-Smith (james.sutherland-smith@vet-ct.com).

Dr. Sutherland-Smith's present address is VetCT, 596 Grove St, Newton Lower Falls, MA 02462.

Dr. Hutchinson's present address is Hill's Pet Nutrition, 41 Hay St, Newbury, MA 01951.