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Table 1 A non-systematic summary of methods across studies that describe intrinsic foot muscle (IFM) morphology using magnetic resonance imaging (MRI)

From: New insights into intrinsic foot muscle morphology and composition using ultra‐high‐field (7-Tesla) magnetic resonance imaging

Citation Reliability MRI sequence Slice selection Muscle of interest ROI selection Fat detection Measure
Andersen et al., 2004 [7] Not reported 1T; T1-weighted spin echo; 4 mm slice thickness; slice interval 10 mm All slices, the first section being randomly placed within the first interslice 10-mm
interval
All, as a single group Semi-automated user set pixel intensity threshold, stereological point-counting method N/A Muscle volume (expressed as a percentage of the value of the matched control participant)
Andreassen et al., 2009 [8] Not reported 1.5T; T1-weighted fast spin echo; 4 mm slice thickness All slices All, as a single group Semi-automated user set pixel intensity threshold, stereological point-counting method N/A Muscle volume (cm3)
Brash et al., 1999 [9] Not reported 0.5T; T1-weighted gradient-echo and T2-weighted spin echo Sagittal section through first metatarsal head Muscle tissue under the first metatarsal head Not described N/A Percentage of CSA that was magnetization transfer active
Bus et al., 2002 [12] Not reported 3T; T2-weighted fast spin echo; 3 mm slice thickness; 0.15 mm interslice gap; acquisition time 30 min 2 datasets collected in frontal plane; 1st dataset 40–46 slices from mid-tarsal joint proximally & distal IP of 2nd toe distally; 2nd dataset 6 slices from distal metatarsal region; one slice through head 5th metatarsal selected for quantitative analysis All, as a single group Semi-automated signal intensity levels using CCHIPS software, verified by visual inspection N/A Muscle CSA (expressed as a percentage of total foot CSA)
Bus et al., 2006 [10] Intra-rater reliability; 4 weeks between measures; weighted kappa = 0.94 1.5T; T1-weighted spin echo; slice thickness 3 mm; 0.9 mm interslice gap Sagittal plane images oriented parallel to long axis 2nd metatarsal and perpendicular to sole of the foot − 19 slices acquired between 1st and 5th metatarsal heads; coronal plane images oriented perpendicular to sagittal plane images − 20 slices between proximal phalanx and cuneiforms; one slice through head 5th metatarsal selected for analysis All, as a single group Visual inspection Semi-quantitative 5-point scale Fatty atrophy: 0 = healthy muscle or no atrophy; 1 = mild atrophy; 2 = moderate atrophy; 3 = severe atrophy; 4 = almost no or no muscle tissue visible
Bus et al., 2009 [11] Cited Bus et al., 2006
(Intra-rater reliability;
weighted kappa = 0.94)
1.5T; T1-weighted spin echo; slice thickness 3 mm; 0.9 mm interslice gap Sagittal plane images − 19 slices acquired between 1st and 5th metatarsal heads; coronal plane images − 20 slices between proximal phalanx and cuneiforms; one slice through head 5th metatarsal selected for analysis All, as a single group Visual inspection Semi-quantitative 5-point scale Fatty atrophy: 0 = healthy muscle tissue or no atrophy; 1 = mild atrophy;
2 = moderate atrophy; 3
= severe atrophy; 4 =
almost complete or complete loss
of muscle tissue
Chang et al., 2012 [18] Intra-rater reliability; one image processed 5 times; coefficient of variation of muscle CSA = 1.3% 1.5T; T1-weighted spin echo; slice thickness 4 mm; contiguous slices; acquisition time 25 min Frontal plane images acquired perpendicular to plantar aspect of foot; every image from calcaneus through to image containing maximum diameter of sesamoid bones All, as a single group (but excluding EDB) Interactive custom software programmed in Matlab; Semi-automated user set pixel intensity threshold N/A Muscle volume (cm3)
Chen et al., 2016 [26] Cited Cheung et al., 2016 (who cited Chang 2012) 1.5T; T1-weighted spin echo; slice thickness 4 mm; contiguous slices Sagittal and frontal plane acquisition; entire length of foot All, as a single group Segmented by excluding all non-contractile tissues in Mimics software N/A Muscle volume (mm3/kg)
Cheung et al., 2016 [19] Cited Chang et al., 2012 1.5T; T1-weighted; Slice thickness 4 mm; contiguous slices Images acquired perpendicularly to the plantar aspect of the foot; entire length of foot All, as a single group Segmented by excluding all non-contractile tissues in Mimics software N/A Muscle volume (mm3/kg)
Cheuy et al., 2013a [13] Inter- and intra-rater reliability; 2 raters processed 46 slices with at least 14 days between measures; all ICCs > 0.9 3T; optimised to fat; spin echo pulse; slice thickness 3.5 mm; acquisition time 9–12 min; Coronal plane images acquired; 35–65 slices; the forefoot (mid-metatarsal), the
midfoot (tarsometatarsal joint of the second metatarsal), the hindfoot (talonavicular joint)
Plantar side muscles, as a single group Signal intensity threshold automatically identified with optional manual editing of borders and thresholds as required, Matlab software Quantitative Volume (cm3):
Subcutaneous fat; Lean muscle; Intermuscular adipose tissue
Cheuy et al., 2013b [14] Not reported 3T; spin echo pulse; slice thickness 3.5 mm; acquisition time 12 min Coronal plane images acquired; 35 slices; talonavicular joint to tarsometatarsal joint Intrinsic foot muscles between the talonavicular and tarsometatarsal joints Signal intensity threshold automatically identified with optional manual editing of borders and thresholds as required, Matlab software Quantitative Volume (cm3):
Subcutaneous fat; Lean muscle; Intermuscular adipose tissue; Intrinsic foot muscle ratio (ratio of intermuscular volume to lean muscle volume
Feger et al., 2016 [25] Not reported 3T; spiral gradient echo; slice thickness 5 mm; acquisition time 15 min Axial slices; entire foot ABH; ADDH-O; ADDH-T; FHB; ABDM; FDM; EDB; FDB; QP, Interosseous Manual segmentation of each muscle perimeter on each slice using custom software written in MatLab N/A Muscle volume (cm3/m.kg)
Feger et al., 2019 [24] Cited Handsfield et al., 2014 (study of leg muscle segmentation; inter-user variability reported as acceptable at < 0.6%) 3T; spiral gradient echo; slice thickness 5 mm; acquisition time 15 min Axial slices were obtained in sets of 20 contiguous images from just posterior to the calcaneus anteriorly through the entire foot. ABH; ADDH-O; ADDH-T; FHB; ABDM; FDM; EDB; FDB; QP, Interosseous Manual segmentation of each muscle perimeter on each slice using custom software written in MatLab N/A Muscle volume (cm3/m.kg)
Gallardo et al., 2006 [23] Not reported 1.5T; T1-weighted fast spin-echo and fat-supressed proton density-T2 weighted fast spin-echo in both planes;
Transverse plane slice thickness 10 mm with 0.5-1.0 mm slice gap; coronal plane slice thickness 4–5 mm with 0.5-1.0 mm slice gap
Coronal and axial planes All Visual inspection Qualitative Presence of signal intensity alterations including muscle oedema, fatty infiltration and abnormal enhancement
Gooding et al., 2016 [29] Not reported 3T; turbo spin echo; slice thickness 10 mm; 0 mm interslice gap; acquisition time 7 min From most posterior aspect calcaneus to the toes; for each muscle the series of 3 contiguous slices that provided the largest CSA used for analysis ABH, FDB, ABDM, QP, FDM, ADDH-O, FHB, Interosseous & lumbricals (together) Each muscle manually outlined; pixel-by-pixel count based on active range (any pixel that exceeded the lower threshold) N/A Percentage increase in muscle activation (pre to post exercise)
Green & Briggs, 2013 [32] Not reported Magnet strength not specified; T1- & proton density weighted; slice thickness not specified; interslice gap 5 mm; Coronal plane images acquired with the plane tilted antero-superiorly to lie perpendicular to the long axis of the second metatarsal 5 groups:
(1) Medial - ABH, FHB; (2) ADDH; (3) Central - FDB, QP, lumbricals; (4) Interosseous; (5) Lateral - ABDM, FDM
Measured using a freehand cursor to trace around the muscle groups N/A Maximum muscle CSA (cm2)
Greenman et al., 2005 [15] Not reported 3T; T2-weighted H spin echo: thickness 2.5 mm; acquisition time 6 min 24 s;
RARE pulse: slice thickness 25 mm; acquisition time 4 min
Axial plane slices; 10 contiguous locations All, as a single group Interactive data language software; an outline of the muscle tissue and reference standard was created using a contour mapping function set to a single level that was equal to the noise threshold value; count of pixels that represented signal from foot tissues N/A Muscle area- to -total area ratio
Kurihara et al., 2014 [33] Not reported 1.5T; T1-weighted fast spin echo; slice thickness 4 mm; acquisition time ~ 9 min Whole foot (sesamoids to calcaneal tuberosity); contiguous slices; acquired perpendicular to plantar aspect of foot; image at the MTP joint that was near 20% longitudinal foot length was selected for analysis 3 muscle groups: 1) Medial – FHB, FDB, QP, ABH and lumbricals;
2) ADDH; 3) Lateral – ABDM, FDB, interosseus
Manual; SliceOmatic software; excluded non-contractile tissues where possible N/A Muscle CSA (cm2)
Lin et al., 2016 [16] Not reported 3T; T1-weighted 1H spin: slice thickness 2.5 mm; acquisition time 6 min 24 s; 31P-RARE: slice thickness 25 mm; scan time 4 min Acquired in a plane perpendicular to longitudinal direction of foot through the metatarsal head region; 10 contiguous; Selected for analysis: level of the 5th metatarsal head from T1-weighted images 3 muscle regions:
(1) FHB medial head; (2) ADDH, FHB lateral head, lumbricals; (3) Interosseous, FDM, ABDM
Manually outlined using tracing tool in OsiriX software; pixel threshold technique Semi-quantitative 5-point scale Ratio (31P/1H) of the area of viable muscle tissue to total area outlined; Fatty atrophy: 0 = healthy muscle with no atrophy; 1 = mild atrophy; 2 = moderate atrophy; 3 =
severe atrophy; 4 = almost no or no muscle tissue visible.
Miller et al., 2014 [27] Intra-rater reliability; five measurements on each muscle over multiple days; mean measurement relative error 0.2–4.3% 1.5T; T2 turbo spin echo fat saturation; slice thickness 5 mm Coronal, sagittal, axial scans; entire foot; muscle measurement from axial scan ABH; FDB; ABDM Manually traced in ImageJ N/A Muscle CSA (mm2)
Muscle volume (mm3)
log normalised to foot length
Pelayo-Negro et al., 2014 [22] Not reported 1.5T; T1-weighted fast spin-echo; fat suppressed proton density-T2-weighted fast spin-echo Slice thickness not specified; axial and coronal planes All, as a single group Visual inspection Semi-quantitative; 5-point scale Fatty infiltration: 0 = no evidence of fatty infiltration; 1 = some fatty streaks; 2 = fat evident but
less extensive than muscle; 3 = fat equal to muscle;
and stage 4 = fat more extensive than muscle.
Recht et al., 2007 [21] Not reported 0.2 to 1.5T; T1- and T2-weighted
(with or without fat suppression) in coronal; STIR or T2-weighted in sagittal
All images ABDM Visual inspection Semi-quantitative; 4-point scale Fatty atrophy: grade 0 =
no fat or minimal fatty streaks; 1 = increased
fat within the muscle but greater amount of muscle; 2 = equal amounts of fat and muscle; 3 = greater amount of fat than
muscle
Savnik et al., 2000 [31] Not reported 1.5T; T1-weighted spin echo;
T2-weighted spin echo and STIR; slice thickness 3–4 mm; interslice gap 0.3–0.4 mm
Sagittal images acquired; coronal reformatted images used for measurement QP; FDB; EH Measured using region-of-interest area function N/A Muscle largest diameter and transverse area
Schmid et al., 2009 [20] Intra-rater reliability CSA measures; 20% of measures repeated; ICCs > 0.9
Inter-rater reliability fatty atrophy score; kappa 0.33 to 0.68
1.5T; T1- and T2-weighted; Slice thickness 3-3.5 mm Coronal images; CSA measures at the level where the bony insertion of the tibiocalcaneal ligament at the calcaneus was best visualised ABDM; FDB; ABH; QP Visual inspection and measurements using OsiriX software Semi-quantitative 3-point scale Muscle CSA (cm2)
Fatty muscle atrophy: 0 = normal muscle; 1 = mild fatty atrophy with more muscle than fat; 2 = substantial fatty atrophy
with more fat than muscle or equal parts fat and muscle
Severinsen et al., 2007 [17] Not reported 1.5T; T1 spin echo; slice thickness 1.5 mm; inter-slice interval 10 mm The first section being randomly
placed within the first interslice interval
All, as a single group Semi-automated user set signal intensity threshold, stereological point-counting technique N/A Muscle volume (mm3)
Taddei et al., 2018 [28] Not reported 1.5T; T1-weighted spin-echo; slice thickness 4 mm; contiguous Images acquired perpendicular to the plantar aspect of the foot; between the most proximal and most distal images in which every intrinsic foot muscle is visible ABH; ABDM; FHB; FDB Measured by ImageJ planimeter software for each muscle at each slice N/A Muscle CSA (mm2)
Taddei et al., 2020 [30] Not reported 1.5T; T1-weighted spin-echo; slice thickness 4 mm; contiguous Images acquired perpendicular to the plantar aspect of the foot; between the most proximal and most distal images in which every intrinsic foot muscle is visible ABH; ABDM; FHB; FDB Measured by ImageJ planimeter software for each muscle at each slice N/A Muscle CSA (mm2)
Muscle volume (cm2)
  1. ABH Abductor hallucis, ABDM Abductor digiti minimi, ADDH Adductor hallucis (oblique and transverse heads combined), ADDH-O Adductor hallucis oblique head, ADDH-T Adductor hallucis transverse head, EDB Extensor digitorum brevis, EH Extensor hallucis, FDB Flexor digitorum brevis, FDM Flexor digiti minimi, FHB Flexor hallucis brevis, QP Quadratus plantae, CSA Cross-sectional area, N/A Not applicable