DigiGait Imaging System - MOUSE

The imaging system is designed for registration of variation parameters of rats’ vestibular apparatus and study of behavior  (the system includes race track for experimental animals and video-camera that registers position of lags on the track (with a frequency no less than 150 fragments per second) and software, analyzing speed, deviation angle with respect to mechanical trajectory, posture, etc.)AH Medical --DigiGait Product Sheet.pdf

The said device shall be ready for utilization and equipped with software package for registration and analyzing of the data and permitting to measure running and motor activity parameters with high accuracy.

The imaging system permits video filming of abdominal cavity of rodents running along transparent electric-drive race track via high-performance video-camera.

Running cells are made of transparent polycarbonate (or equivalent) with adjustable front and back walls.

Positioning of cells’ walls: from 7,6 cm up to 61 cm

Cell changing time: no less than 1 minute

Race track: transparent, easy- washable closed polymer tape.

Speed adjustment of race track using digital indicator: from 0 up to 100 cm/sec with resolution no less than 0.1 cm/sec.

Race track motor: DC-type - ¼ HP; torque – no less than 45 ft/inch.

Illumination: 90-250V (DC, 25 KHz); color temperature - 5000 K.

Computation of running parameters – automatic, without markers.

Speed for definition of limbs’ positioning - no less than up to 150 images per second.

Data output:  dynamic parameters of running for each limb and animal posture diagram.

Definable parameters: step length, limb transfer, inhibition, beat and fall, step sequence, regularity ratio and functional index of sciatic nerve.

DigiGaitTM Imaging System

We developed DigiGaitTM to image the ventral side of mice or rats as they walk on a motorized transparent treadmill belt. One high-speed camera captures the dynamics of the paws and corresponding limbs as they approach the belt during the braking phase of stance, or move away from the belt during the propulsion phase of stance just before the swing phase. The DigiGaitTM system fully quantifies the stance and swing components of stride. Proprietary software automatically calculates stride length, stride duration, stride frequency, and numerous other spatial and temporal gait indices, for each limb. This novel system was initially invented (patents pending) by Mouse Specifics to identify mice with biomarkers of gait abnormalities. We have extended the application of this unique instrument to the study of a wide array of models, pathologies, and drug-induced ataxias.

NO MORE INKING OF PAWS! NO REFLECTIVE MARKERS REQUIRED!

DigiGaitTM will become the assay of choice for phenotyping mouse models of neurodegenerative disease, arthritis, and pain, and testing the efficacy of drugs to correct motor dysfunction.

The DigiGaitTM system provides numerous spatial and temporal indices of posture and gait dynamics, including:

• Stride length
• Stance width
• Stance duration
• Swing duration
• Braking duration
• Propulsion duration
• Stride frequency
• Paw Angle

Applications include mouse models of:

• Amyotrophic lateral sclerosis
• Arthritis
• Drug-induced ataxia
• Ethanol sensitivity
• Huntington's disease
• Pain
• Parkinson's disease
• Spinal Muscular Atrophy

DigiGait Frequently Asked Questions

1. Why did you patent the DigiGait system?

Scientists and engineers from Mouse Specifics, Inc. and The CuraVita Corporation invented the technology and analysis software for imaging small mammals' gait from underneath a transparent treadmill belt. The system provides not only two-dimensional topography, but also three-dimensional kinematics. The patent exemplifies the system's utility and novelty, and our commitment to scientific excellence. Imitators of the technology do not adhere to the same rigor in ensuring instrument accuracy or sensitivity.

2. How does the DigiGait system compare to other gait analysis systems?

The DigiGait system does not require external reflective markers to be attached to the animal for gait analysis, whereas other systems may require markers. DigiGait directly collects digital video images of the underside of animals, whereas other systems may use a mirror to reflect the ventral view of the animal to a camera. As a consequence, image clarity, color, and shades are best preserved by DigiGait. The DigiGait system enables the user to select a range of walking speeds, whereas other systems expect the animal to walk [or not walk] at its preferred walking speed. This feature of DigiGait is important since there may be no gait abnormalities at a slow walking speed, but a high walking speed may demonstrate important differences. Moreover, even subtle differences in walking speed may have profound effects on gait indices.

3. Why is temporal resolution important in gait analysis?

Rodents may walk at speeds exceeding 90 cm/s. Mice walking at such speeds recruit their limbs more than 10 times each second. All the kinematic parameters are shortened at such a high speed. The braking duration of the forelimbs, for example, can be shorter than 40 ms. High temporal resolution, therefore, is important to provide exact information about subtle gait abnormalities.

4. What is the spatial resolution of the DigiGait system?

The spatial resolution of the DigiGait system exceeds 5,000 pixels per cm2.

5. How does the DigiGait system determine the correct swing time?

The treadmill belt of the DigiGait system is transparent, so that the high resolution digital video camera is able to image the ventral view of the paws even when they are not in contact with the treadmill belt. Among the thousands of lines of code and artificial intelligence algorithms within the DigiGait software are functions that detect not only the spatial coordinates of a pixel, but also its direction. An image pixel of a paw that has a linear direction parallel to the treadmill belt is in the stance phase of a stride. An image pixel of a paw that has a direction different from the direction of the belt is in the swing phase of stride.

6. How often does the treadmill belt need to be replaced?

One of the first DigiGait treadmills has been in service at the Pfizer Pharmaceutical Company for over 3 years, and the treadmill belt has been changed once. The belt can be exchanged in <10 minutes. The belt material has good transparency without comprising the animals' tactile walking comfort. The belt can be cleaned with most laboratory cleaning agents, including ethanol.

7. Can spinal cord injured animals walk on the treadmill?

Spinal cord injured rodents are able to execute stepping on the treadmill. In animals with total hemisection, the forelimbs of the animals attempt to compensate for hind limbs paralysis. The DigiGait system is able to quantify the asymmetry between forelimb and hind limb stepping as the animals recover from spinal cord injury. Several gait metrics are of interest in spinal cord injured animals, including phase dispersion, paw placement angle, and toe spread.

8. How do the metrics of the DigiGait system compare to the BBB score?

The DigiGait system objectively reports over 30 metrics of posture and locomotion at a range of walking speeds. There are likely some functional measures of the Basso-Beattie-Bresnahan (BBB) score that relate to the DigiGait system's quantitative metrics. However, most gait metrics are very sensitive to walking speeds, and walking speeds usually differ between animals in the open field. Stride lengths, for example, of a group of mice with cerebral infarction, may be significantly different at walking speeds of 20 cm/s vs. 25 cm/s, a velocity difference imperceptible to the eye. The DigiGait system also reports phase dispersion values that quantify interlimb coordination, differences in which are relevant when animals are studied at comparable walking speeds.

9. Does the DigiGait system measure ground reaction forces?

The DigiGait system does not measure ground reaction forces. Only a system that includes force transducers can measure ground reaction forces. The qualitative shape and quantitative timings of gait signals obtained by the DigiGait system, however, have been shown to correlate to force development in rodents. For example, the protracted braking durations of forelimbs compared to hind limbs, and the briefer propulsion durations of hind limbs compared to forelimbs, indicate hind limb vs. forelimb functional differences in loading and force development. DigiGait, moreover, has demonstrated significant differences in several gait metrics in hamsters with muscular dystrophy that may be attributable to their muscle weakness.

Publications describing application of DigiGait Imaging System

1. HamptonTG, Stasko MR, Kale A, Amende I, Costa ACS. Gait Dynamics in Trisomic Mice: Quantitative Neurological Traits of Down Syndrome. Physiology & Behavior, 2004, in press.

2. Piskorksi K, Kale A,ChuV, Otero JM, Gladstone K, Mueller P, Amende I, and Hampton TG. Non-invasive physiology in conscious mice. 2002Fourth WorldCongress Alternatives Congress Trust Proceedings. 2004, in press.

3. HamptonTG, Stasko MR, Amende I, Kale A, Costa ACS. Gait dynamics in a mouse model of Down syndrome. Program No. 664.15. 2002 Abstract Viewer/Itinerary Planner.Washington,DC: Society for Neuroscience, 2002.

4. HamptonTG, Kale A,GladstoneK, Bridges J, Costa ACS, Amende I. How to characterize gait dynamics in mouse models of neuromuscular disease. Program No. 22.60. 2002 Abstract Viewer/Itinerary Planner.Washington,DC: Society for Neuroscience, 2002.

Amende I, Kale A, McCue S, Glazier S, Morgan JP, Hampton TG.

Division of Medicine,BethIsraelDeaconessMedicalCenter,HarvardMedicalSchool,Boston,MA02215,USA. ivo@amende-hannover.de

BACKGROUND: Gait is impaired in patients with Parkinson's disease (PD) and Huntington's disease (HD), but gait dynamics in mouse models of PD and HD have not been described. Here we quantified temporal and spatial indices of gait dynamics in a mouse model of PD and a mouse model of HD. METHODS: Gait indices were obtained in C57BL/6J mice treated with the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, 30 mg/kg/day for 3 days) for PD, the mitochondrial toxin 3-nitropropionic acid (3NP, 75 mg/kg cumulative dose) for HD, or saline. We applied ventral plane videography to generate digital paw prints from which indices of gait and gait variability were determined. Mice walked on a transparent treadmill belt at a speed of 34 cm/s after treatments. RESULTS: Stride length was significantly shorter in MPTP-treated mice (6.6 +/- 0.1 cm vs. 7.1 +/- 0.1 cm, P < 0.05) and stride frequency was significantly increased (5.4 +/- 0.1 Hz vs. 5.0 +/- 0.1 Hz, P < 0.05) after 3 administrations of MPTP, compared to saline-treated mice. The inability of some mice treated with 3NP to exhibit coordinated gait was due to hind limb failure while forelimb gait dynamics remained intact. Stride-to-stride variability was significantly increased in MPTP-treated and 3NP-treated mice compared to saline-treated mice. To determine if gait disturbances due to MPTP and 3NP, drugs affecting the basal ganglia, were comparable to gait disturbances associated with motor neuron diseases, we also studied gait dynamics in a mouse model of amyotrophic lateral sclerosis (ALS). Gait variability was not increased in the SOD1 G93A transgenic model of ALS compared to wild-type control mice. CONCLUSION: The distinct characteristics of gait and gait variability in the MPTP model of Parkinson's disease and the 3NP model of Huntington's disease may reflect impairment of specific neural pathways involved.

6. Digigait quantitation of gait dynamics in rat rheumatoid arthritis model.Berryman ER, Harris RL, Moalli M, Bagi CM.

Global Science and Technology, Worldwide Comparative Medicine, Pfizer Inc.,Groton,CT06304,USA.

INTRODUCTION: Rheumatoid arthritis (RA) is characterized by joint pain, allodynia and hyperalgesia. The rat carrageenan model utilizes inflammation-associated pain following injection of the knee joint to model RA. Traditional assessment of pain in these models utilizes behavioral scoring or manual measurements, methods that are labor intensive and prone to subjective interpretation. This study utilizes the Digigait system to objectively quantify movement and gait dynamics in a monoarthritic rat model. MATERIAL AND METHODS: A pilot study in rats selected "natural" runners using Digigait, and also measured inter and intraday variability as well as effects of anesthesia on gait dynamics. In the main study, 12 female rats were tested at baseline, divided in two groups of 6 rats, briefly anesthetized with isoflurane and injected with 60 microl of 2% lambda carrageenan or vehicle; Digigait testing was repeated 2 and 4 hours post injection and data analyzed. RESULTS: Selection of "natural" runners significantly contributed to accuracy and reproducibility of gait parameters obtained by the Digigait system. There was minimal intra and inter day variation between individual rats and 4 minutes of isoflurane anesthesia had no effect on gait dynamic at 2 and 4 hours post administration. In the main study a highly reproducible gait signature in the injected limb, and well coordinated adaptation of gait during locomotion in the non-affected limbs were noted as short-term changes following carrageenan injection. CONCLUSION: Digigait system was found to be an objective and reliable method for quantification of early behavioral changes consistent with allodynia and hyperalgesia in an inflammatory pain model.

老鼠全自动步态分析系统是为了用于在行为学上评价神经创伤、神经性萎缩、神经疾病、疼痛症状群动物模型，其应用范围包括：脊髓损伤、神经性疼痛、关节炎、中风、帕金森病、运动失调、脑损伤、外周神经损伤、关节损伤、骨伤等。

*(1).老鼠全自动步态分析仪包括软件和硬件部分：软件部分为自动步态分析软件，硬件部分包括压力反光玻璃跑道、彩色高速摄像机以及工作站。

*(2).足印光亮技术：LED灯在压力反光玻璃内部发光，正常情况下压力玻璃为全内反射状态。当老鼠的爪子接触到压力玻璃时，光线从另外一面折射出来，被正置于压力反光玻璃彩色高速摄像机以100HZ的速度记录下来并且传输到装有全自动步态分析软件的工作站中，进行下一步的分析。

(3).压力反光玻璃跑道包括压力反光玻璃以及回廊。压力发光玻璃确保可以记录全自然状态下的运动以及足印为标准步态，为了适合同时进行大小鼠实验，其尺寸应该为（长*宽*高）：130*20* 0.5cm ；回廊的宽度应为连续可调以便适应不同尺寸的大鼠及小鼠，同时方便清理。

(4).在一个完整的步态分析中，起码应该捕捉到老鼠5-6个踏步。因此，彩色高速相机的高度位置在0 -100cm 之间连续可调，以适应不同规格的大鼠及小鼠的步态分析。

(5).分析软件支持浏览、设置、采集、分类、可视化、分析以及结果输出。

(6).分析软件可视化至少包括：足印图（print view）、步态示意图（gait diagram）、足印强度（Print intensities）、以及三维足印（3D footprint）。

*(7).分析软件至少可以分析以下的参数：：落脚位置（stance）、停步（brake）、推进（propulsion）、摆动周期（swing phase）、步态循环比例（duty cycle）、压力（pressure）、四足的3D强度（3D intensitys）、2D强度（2D intensitys）、踏步范式（Footfall Patterns）、站立指数（stand index）、节奏（cadence）、跨步长度（stride length）、步间距离（base of support）、踏步次序（step sequence）、周期延迟（phase lags）、支撑方式（support formulas）、正常步序指数（regularity index）。