Small animal marker tracking

[John Barden]

Dear BIOMCH-L members:

I'm interested in hearing from those of you who have done locomotor biomechanics research on small animals (or facial motion tracking in humans). I'm working with a colleague in Biology who does spinal cord research, and he's trying to quantify the level of gait function that can be restored in rats after a spinal cord injury. I'm trying to help him by tracking markers placed on the rats legs which is proving to be quite a challenge. We've had some success cutting small pieces of 3M reflective tape, but we can't get it to stick very well (or for very long). I was wondering if you know whether there's a special kind of glue that we could use? We tried Crazy Glue but I was told that this would not be okay as it caused quite a bit of pain to remove the glue from the rats legs afterwards. My understanding is that glue is used to attach the small markers used for facial marker tracking in animation. If any of you know of something that's typically used or have any suggestions I'd be grateful to find out. We've also tried metallic paint, but we can't seem to find any paint that reflects well enough to be picked up by the cameras. So, if you also have knowledge of any paint that works for the purposes of motion tracking I'd be interested in finding that out as well. Thanks very much in advance for any assistance you can provide.

[Dan India]

Re: Small animal marker tracking

Dear BIOMCH-L members:


You wrote


I'm interested in hearing from those of you who have done locomotor biomechanics research on small animals (or facial motion tracking in humans). I'm working with a colleague in Biology who does spinal cord research, and he's trying to quantify the level of gait function that can be restored in rats after a spinal cord injury. I'm trying to help him by tracking markers placed on the rats legs which is proving to be quite a challenge. We've had some success cutting small pieces of 3M reflective tape, but we can't get it to stick very well (or for very long). I was wondering if you know whether there's a special kind of glue that we could use? We tried Crazy Glue but I was told that this would not be okay as it caused quite a bit of pain to remove the glue from the rats legs afterwards. My understanding is that glue is used to attach the small markers used for facial marker tracking in animation. If any of you know of something that's typically used or have any suggestions I'd be grateful to find out. We've also tried metallic paint, but we can't seem to find any paint that reflects well enough to be picked up by the cameras. So, if you also have knowledge of any paint that works for the purposes of motion tracking I'd be interested in finding that out as well. Thanks very much in advance for any assistance you can provide.

Qualisys has many users assessing small animals with our 2.5 and 4.0mm hemisphere lightweight markers which are stamped and hollow backs. Go to www.qualisys.com to view such markers.

Users would use tweasers and eye lash glue especially on the face

Dan india

[Erik Sinsel]

Re: Small animal marker tracking

In using 4mm and 3mm hemispherical reflective markers on human hands we have had success using electrode washers, with the adhesive disc cut sufficiently closely around the marker using a hobby knife.

Erik Sinsel

[Amanda Lin]

Re: Small animal marker tracking

If you have a good enough budget (or you can write it in a grant), try one of those rodent gait assessment systems. For pilot data, you can use footprint test which I am using at the moment. That doesn't require a high-end motion capture system and has been proven sensitive enough to assess motor behavior in rodents.

Dear BIOMCH-L members:

I'm interested in hearing from those of you who have done locomotor biomechanics research on small animals (or facial motion tracking in humans). I'm working with a colleague in Biology who does spinal cord research, and he's trying to quantify the level of gait function that can be restored in rats after a spinal cord injury. I'm trying to help him by tracking markers placed on the rats legs which is proving to be quite a challenge. We've had some success cutting small pieces of 3M reflective tape, but we can't get it to stick very well (or for very long). I was wondering if you know whether there's a special kind of glue that we could use? We tried Crazy Glue but I was told that this would not be okay as it caused quite a bit of pain to remove the glue from the rats legs afterwards. My understanding is that glue is used to attach the small markers used for facial marker tracking in animation. If any of you know of something that's typically used or have any suggestions I'd be grateful to find out. We've also tried metallic paint, but we can't seem to find any paint that reflects well enough to be picked up by the cameras. So, if you also have knowledge of any paint that works for the purposes of motion tracking I'd be interested in finding that out as well. Thanks very much in advance for any assistance you can provide.

[Sharon Zdunowski]

Re: Small animal marker tracking

We have been doing motion tracking with rats and mice after spinal cord injury for many years. The best way to adhere markers is with eyelash adhesive. The eyelash adhesive is a latex based glue, so it peels off when you are done or can be removed with warm water. Also, it is non-toxic if some is left on the skin.

You will need to shave the whole lower body within 48 hours of needing to place markers. Longer fur can cover parts of the markers giving you odd shapes in the video and leads to inaccurate tracking. Depending on the species, some fur can act retro-reflectively; meaning you get 'phantom markers' on the body. And the eyelash adhesive does not stick to the fur; it needs to adhere directly to the skin.

We make our own reusable marker using retro-reflective tape. Sounds like you already have tape, but you can search through the Biomech archives to find more information on which tapes work best. We use the tape and wrap it around 'wiggle eyes' that you get at the craft store. We use 3mm and 4mm markers. For marking the digits of the toes, we use a 1/8" hole punch, make a tee-pee style marker and adhere using the eyelash adhesive; these are not reusable.

We learned the hard way that getting the eyelash adhesive on the retro-reflective tape renders it non retro-reflective. Now we are very careful in how much glue we place on the bottom of the marker, clean our forceps/tweezers often so any glue that may have gotten on there does not transfer to the next marker we place, and pull off any glue on the markers after each use.

Good Luck!
Sharon

[Young-Hui Chang]

Re: Small animal marker tracking

Hi John, We have done rat movement analysis using x-ray video for a few years now and have data showing considerable movement errors associated with soft tissue movement artifacts (see Bauman & Chang J. Neurosci. Methods 2010; Bauman & Chang Biol Let 2013). This artifact problem is exacerbated in small mammals like rats and mice compared to larger animals like horses and humans. I would strongly caution against using skin markers to estimate positions of the proximal joints (knee and hip) as they can lead to very misleading proximal joint kinematics. In a direct comparison using x-rays and skin markers, we saw errors as high 40 degrees at the knee in some parts of the gait cycle(!). The skin around the foot and ankle is reasonably tight, so I would be more confident in those markers if you wanted to calculate step parameters or ankle joint kinematics using two markers to estimate a shank segment unit vector and a third on the metatarsal-phalangeal joint, but I would not calculate ankle joint angles using data from knee or hip joint markers as these can be unreliable. Varejao and colleagues have done some nice work showing that sagittal plane ankle joint kinematics alone can provide greater sensitivity than paw print analysis (Sciatic Function Index) after a sciatic nerve injury (e.g., see Varejao et al., Muscle Nerve 2003; Varejao et al., Microsurgery 2001).

If you really want accurate/reliable proximal joint kinematics in rodents, I don't see any other way other than to use an x-ray video system. The good news is that more and more of these systems are becoming available around the world. I think at last count there was close to at least 25-30 of them around the world--I know there is one at the Univ. Calgary (Janet Ronksy's lab). Brown University has an excellent resource for how to set up one of these labs and what type of data you can get from them (http://www.xromm.org). Gillian Muir (who I assume is your collaborator in Saskatchewan?), has also done some excellent work using ground reaction force patterns to characterize rat gait after SCI. It really is surprising that given the importance of rodent models for biomedical research, that we are still unable to do basic biomechanical analyses like we have been doing in humans for decades now. But, I think this is beginning to change.

Regarding marker attachment, rats are excellent at taking their own markers off! You just need to make it so that it is safe for them to ingest. In our skin marker comparison study, since we were using x-rays we used 0.8-1.0 mm tantalum beads that we superglued to the skin after palpation and marking with a pen. These beads are radiographically opaque, but biologically inert. We agree that you can tear skin trying to take these markers off, so we just let the rats take off their own markers--they are far superior to taking them off without tearing skin then we are. An added benefit is that I think it is less stressful for the animals since it requires less handling and/or anesthetization after the experiment. Since tantalum is a biologically inert metal, if they ingested the beads they would just pass the marker in a couple days. With reflective markers, we have also used reflective tape over hemispheres as previously mentioned (little doll eyes you can buy at craft stores). They can work well for reflective markers, but again, I would caution about where you try to make measurements with skin markers and consider whether the rats can ingest these markers safely. We have tried wig glue, but were not very satisfied with it. The suggestion for eyelash adhesive sounds interesting and may be a good alternative.

One other tip, if you put something that is bitter tasting over the marker, the rats are less likely to tear them off during the trial. We have used a mixture of New Skin (liquid bandage) and metronidazole (very bitter tasting antibiotic) that we coat on top of the markers (and healing wounds). We find that this works quite well for us. You can also try Bitter Apple spray, which is used by vets to keep dogs from chewing their stitches, but the New Skin/metronidazole mixture seems to work much better for us.

Hope this is helpful, feel free to email me offline if you have any further questions.

cheers,

Young-Hui Chang


Cited Refs:
1. Bauman JM, Chang YH. 2010 High-speed X-ray video demonstrates significant skin movement errors with standard optical kinematics during rat locomotion. J. Neurosci. Methods 186, 18–24. (doi:10.1016/j.jneumeth.2009.10.017)

2. Bauman JM and Chang YH. Rules to limp by: joint compensation conserves limb function after peripheral nerve injury. Biology Letters, 9(5): 20130484, 2013. doi:10.1098/rsbl.2013.0484

3. Varejao ASP, Cabrita AM, Meek MF, Bulas-Cruz J, Filipe VM, Gabriel RC, et al. Ankle kinematics to evaluate functional recovery in crushed rat sciatic nerve. Muscle
Nerve 2003;27:706–14.

4. Varejao ASP, Cabrita AM, Patricio JA, Bulas-Cruz J, Gabriel RC, Melo-Pinto P, et al. Functional assessment of peripheral nerve recovery in the rat: gait kinematics. Microsurgery 2001;21:383–8.

[John Barden]

Re: Small animal marker tracking

Thanks Dan.

[John Barden]

Re: Small animal marker tracking

Thank you Erik.

[John Barden]

Re: Small animal marker tracking

Thanks Fang, the footprint analysis is a good suggestion. Do you have any further info. on "rodent gait assessment systems"? I'm not familiar with any such thing. I'll see what I can find out, but if you have a link or any other info. I'd appreciate knowing about it. Thanks in advance.

[John Barden]

Re: Small animal marker tracking

Hi Sharon. Thanks very much for this. This is extremely helpful and we will likely give it a try. Best wishes.

John.

[John Barden]

Re: Small animal marker tracking

Thanks Young-Hui. I am very grateful for the reply. I'll look into the x-ray video system as this sounds promising. I don't know Janet Ronsky, but have heard of her and have several contacts at the Univ. of Calgary so that might be something we can work out. I do not know (or collaborate with) Gillian Muir (is she at the Univ. of Saskatchewan?), but would be interested in talking to her as well since you say she has done work in this area. Please let me know if you have any contact info. for her. Thanks again as this is very helpful.

John

[Amanda Lin]

Re: Small animal marker tracking

You may want to take a look at DigiGait from Mouse Specifics, https://mousespecifics.com/digigait/

Thanks Fang, the footprint analysis is a good suggestion. Do you have any further info. on "rodent gait assessment systems"? I'm not familiar with any such thing. I'll see what I can find out, but if you have a link or any other info. I'd appreciate knowing about it. Thanks in advance.