TERMINATOR SALVATION - Spoiler Alert #4

MARCUS' HEART

The dialogue of the film reminds us on occasion of Marcus' heart. Blair (Moon Bloodgood, Rowr!) mentions it beating strongly when she seductively snuggles up to him and lays her head on Marcus' chest. Connor tells Marcus he sees his "heart beating a mile a minute." However we never see it directly, only through Terminator-vision at the end of a fight, so we don't know it's a human heart. Marcus' metallic skeleton at his chest is exposed but his heart is never visible to us.

Marcus' naughty parts

Here's a picture of Marcus' skeleton that I got off of Rotten Tomatoes. You can see that Marcus either has an organic heart encased in that metal skeleton, or perhaps he doesn't have a heart at all. Maybe the machines gave him some kind of mechanical pump that only sounds like a heart in case he has to snuggle with a human female.

Everyone mentions his heart. We all get it. Marcus has a strong heart. It's robust, can pump blood through an organism made of a combination of organic and manufactured materials, and is the symbol of his emotions, values, and humanity. Marcus' heart is the key to the final action, his redemption, and John Connor's life (so that there can be another movie -- spoiler alert #4.5!). The way the film works this material is both irritating and entertaining.

MARCUS TO THE RESCUE

In the factory during the final big action scene, Connor defribillates Marcus with industrial cables not because he is a being of value, but because Connor can use him as a weapon against a Terminator. Connor needs a weapon, and Marcus is it. But before the revived Marcus can stop it, the Terminator shoves a pipe through Connor's chest, where his heart would be if he had one(1). That is a great moment! It's shot really well, the welling blood suits their palette, and the action is well timed. Marcus then saves Connor and helps get him back to the base.

Getting to the 'copter

YOU KNOW THORAX

Back at base, Connor is dying because "his heart is too weak." Really? That's it? How about a collapsed lung, massive loss of blood, perhaps a sucking chest wound, fractured ribs splintering into everything, and insane amounts of bleeding around the mediastinum?

Below are some pictures of the chest. The mediastinum is essentially the area between the lungs, housing the heart in the "pericardial cavity". The lungs, heart, and other tubes are partitioned off from one another by sheets of connective tissue, sometimes referred to as membranes.

Mediastinum, anterior view

Here we see the heart and its vessels nestled in the mediastinum, between the lungs.

Mediastinum, cross cut

This is similar to an aerial view. The sternum is at the top of the picture, the vertebral column at the bottom, center. We see the lungs (right and left) and many of their blood vessels. We also see the top of the heart and the vessels from the lungs leading into the heart (in blue... yes, blue); these are essentially located within the borders of the mediastinum.

If bleeding happens within a partitioned area, the membranous walls keep blood from going everywhere. If one lung collapses due to blood in the chest (hemothorax[2]), the other lung can function because the blood won't leak into its space unless these partitions are compromised.

Hemothorax

After Marcus rescues him, Connor seems to be able to breathe and is not hacking up blood loogies, so the pipe and splintered ribs have obviously not pierced his lungs or their cavity (the plural cavity for you trivia buffs). His breathing would be pretty labored if he had a hemothorax or pneumothorax(3) situation. So what the heck happened? What is the scenario to fit the shot of the pipe emerging from Connor's chest, with all that blood welling up?

The only thing we can assume is there is bleeding (and swelling) around Connor's heart, causing compression to its chambers. This is called cardiac tamponade(4). The pressure from the blood build-up would reduce the amount of blood that could get into the heart, reducing cardiac output. To compensate, the heart would have to beat faster to try and get enough blood around the body. This condition would indeed weaken and exhaust the heart. This is the only condition I could possibly come up with to support the action and the script. I'd be curious to know what the writers were thinking...

Here's an illustration of cardiac tamponade from a World War II surgical manual. It's comforting to know that traumatic injuries suffered in the 20th century will still be around well into the 21st century...

Cardiac Tamponade

I LEFT MY HEART IN SAN FRANCISCO...OR WAS IT L.A?

So, Marcus tells them to take his heart and transplant it into Connor's body. It is Marcus' chance to redeem his criminal life and sacrifice himself for a higher cause. What does Marcus get from Connor for his heart? A curt nod. No "thank you" or, "I guess you're human after all" or anything. Obviously Connor will never need a penis transplant. He's a big enough one as it is.

Then they perform transplant surgery out of doors under a netted camouflage tent. Grit and dust aren't sterile. There is a lot of bacteria in dirt, you know. As an example, anthrax bacteria can live in dirt for years and years. Wind can blow all sorts of bacteria into a wound. They should also do some blood and tissue typing before wasting Marcus' heart, if he even has one. If Connor doesn't die of infection, he may die of tissue rejection(5), which means... no sequel!

Anthrax Bacteria (the rod-shaped things)

CYBORGS AT LARGE

Thinking about Marcus (only professionally, of course) as the first human-based cyborg to show up in a Terminator film, I started thinking about cyborg films, generally. Expect the next entries to be an exploration of the meat/metal interface.

1. Connor's character is so self-centered! Let's face it, if I grew up with a mother who taught me to use firearms and told me I was destined to be the savior of the world, I'd be pretty stuck up, too.

2. Hemo = blood, thorax = chest. Put it all together, and there you have it.

3. Pneumo = air. I sense a pattern. Pneumothorax might happen if the chest wall and/or lung was punctured. As Connor struggled to breathe, air could get into the space around the lung, collapsing it.

4. Tamponade can refer to both the accumulation of blood around the heart or "the act of using a tampon." Thank you, Taber's Cyclopedic Medical Dictionary.

5. For more on transplantation feel free to peruse the Face/Off! entries from March of 2009.

Face/Off part 5 - Can you handle the rejection?

To wrap up the Face/Off series, a little more exploration of tissue rejection is in order so that we can appreciate the full depth of amazing, entertaining, wackiness serving as a vehicle for this movie.

MHC ANTIGENS

All the cells in you body have a unique set of protein markers on them called major histocompatibility complex antigens (MHC antigens).

MHC antigens

MHC antigens are sometimes called "self antigens." They let the cells of your immune system know what is you (cells with your MHC antigens on them) and what is not you. If cells are not you, they should be inactivated, destroyed, and/or eaten, because they are usually pathogens and about to do you harm, or so your immune system would reason.

There are a number of ways one's body will destroy foreign cells, here are a couple of them. Immune cells (white blood cells) travel to the site of foreign cells to eat them or cells already in the area can release chemicals to destroy them (cell mediated immunity). Or antibodies and other plasma proteins can attack the tissues via the bloodstream (humoral immunity).

Antibodies

What does this mean for our movie? Well, if the blood match is wrong, and/or the graft (or face) for the recipient is of the wrong tissue/blood type, that FACE is coming OFF, all right. It will not be in any shape to return to its original owner, either.

Rejection of a transplant can be dramatic, as in a hyperacute reaction which happens within hours or minutes of revascularization (return of blood flow).

Hyperacute tissue rejection

(Dark purple things are stained white blood cells.)

Acute rejection will occur within a week, or months.

Acute rejection

Chronic rejections can happen after years, even when the patient is taking anti-rejection drugs(1). With rejection, one's immune system attacks the foreign tissue. In the case of a face, that might make for a good horror movie...

Chronic rejection slide

(The slides of tissue rejections are all of kidneys.

I couldn't find pictures of rejected face tissues online.)

Can't you see John Travolta (as Archer) impersonating Nicholas Cage (Troy) with his face all mottled and slipping around? They could fight over the only remaining viable face, which would be Archer's, due to that blood type issue mentioned in Part 4. But I digress.

To prevent rejection, a transplantation patient must take drugs to suppress their immune system for the rest of their life (or as long as they have the transplanted tissue in their body.) These drugs suppress the whole immune system. Death due to secondary infections is very possible with transplant recipients, whether they are using "the new anti-inflammatories" or not because they are not as capable of fighting off pathogenic organisms like bacteria (whose antigenic markers show them to be foreign to one's body.) We don't see it in the film but I'm sure Archer and Troy were scrupulous hand-washers when off camera. Particularly Archer, when he was in prison with Troy's face. I imagine prison is kind of dirty and has lots of bacteria.

Prednisone is a corticosteroid immune suppressant that is commonly used by transplant patients. Dosages of prednisone are much higher immediately following surgery, and can usually be lowered over time, but rarely can the patient stop taking the drug altogether(2).

Prednisone can cause a number of side effects including; increased fat over the face (sometimes called "moon face"), shoulders, and abdomen, although the arms and legs will be unaffected by the new fat distribution; longer healing time for skin; ulcerations of the skin; osteoporosis (thinning of the bones); fatigue; and muscle weakness. In addition, people taking prednisone or other immunosuppressive drugs have a greatly increased risk of developing certain types of cancers, which a healthy immune system would help to keep in check.

Signs of chronic prednisone use

In conclusion, it's a great thing for Archer that these procedures were indeed "completely reversible." He got his original tissues (including tummy fat) returned to his body and got rid of the morpho plate inside his face. If Troy's face had damage to it from rejection, it doesn't really matter because (spoiler alert 12 years after the screening of the film) Troy dies, but not from faceless cigarette smoking!

Face/Off

1. Merck. pp. 347-352

2. Merck. pp. 346-354

Face/Off part 4 - Troy Emerges From His Coma!

Face/Off

TROY AWAKENS

Troy comes out of his coma without signs of functional or cognitive debility, and unwraps his face. We get some great wet sucking sounds as he pads barefoot through a deserted hospital ward to discover Archer's face-skin floating in a dish.

Face/Off

Troy is initially incoherent and starts screaming when he sees Archer's face, but he's a resilient psychotic terrorist and recovers his wits pretty quickly. Within hours (or less) he's sucking up a cigarette and on the phone to his henchmen.

Troy also talks on the phone pretty well. We see a bit later in a reflection of his faceless face that he's still got a lot of lip and cheek left, which explains why he is so coherent when speaking. It also explains how he can get that smoke out of his cigarette. Yes, smoking without a face, nice touch! It reminds me of the old films like Double Indemnity where Fred Mc Murray has been mortally wounded, is oozing blood everywhere, and wants a cigarette from Edward G. Robinson, which he smokes as he slips into unconsciousness(1).

Face/Off

My colleague Bill reports that the whole smoking without skin on your face thing had been done already. Hellraiser III apparently has a woman, with no skin at all, calmly smoking a cigarette.

We don't see Dr. Walsh and his team perform Troy's surgery as he takes on the face and body of Archer, but one again, the procedure is a success. surgery is performed and Troy is recovered before people come in to work the next morning.

FUN FACTS ABOUT TRANSPLANTATION

An allograft is a tissue graft between genetically dissimilar members of the same species(2). An autograft is a transfer of one's own tissues from one site to another(3). Transplantation is the transfer of living tissues or cells from a donor to a recipient(4).

So when Archer gets Troy's face the first time, it's transplantation/allograft. The question is, is it autograft when he gets his face back at the end of the film? Is there a name for a procedure where one has living tissue removed, and then re-attached to the same place after hanging out on someone else for awhile?

Allografts may be rejected by the recipient's immune system. this is a major danger for most types of transplants.

Image from Dailymail

As a plot point in the film, Troy's AB blood gives him away to Archer's doctor wife, which Archer's O- blood confirms that he is who he claims to be. I assume that both men are Rh negative(5), just for the sake of argument. If we only look at blood typing, people with type AB blood can receive type O, but people with type O blood cannot receive type AB (long story). So Archer's face might go onto Troy's body (assuming tissue compatibility for a moment) without major trouble, but Archer will probably reject Troy's face tissue that minute his blood vessels get his blood into Troy's tissues. CLOT CITY!

Next time: The final episode of Face/Off - Tissue rejection!

1. Chandler, Raymond, Billy Wilder, et al. Double Indemnity. Universal legacy series. Universal City, CA: Universal Studios Home entertainment, 2006. One of the bes love stories about two men in the insurance business.

2, 3, 4. Berkow, Robert. The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 1992 p. 347

5. In the most basic of nutshells, Rh factor is a blood group discovered on the surface of erythrocytes (red blood cells, to you and me) of rhesus monkeys. Some people have this group (RH+) and some do not (Rh-). If you inject an Rh- person with Rh+ factor, their body will become sensitized to it. If injected with it again later on, perhaps via a transfusion, the Rh- person's body will have a transfusion reaction, which is an allergic reaction (cytotoxic hypersensitivity reaction for you trivia buffs). Red blood cell destruction and huge amounts of clotting are the result. Gues what "Rh" stands for...Yup! Rhesus!

Face/Off part 3 - The Surgery

TROY'S SURGERY

Troy and Archer are in surgery at the same time so that Troy's face will be plenty fresh for Archer's skull. Surgeons cut through the dermal layers of Archer's face with another laser that looks very similar to the laser that was building Loomis' ear. There is very little blood. I assume that laser is cauterizing as it slices. these people have red and blue lasers for everything!

After cutting around the perimeter of his face, the surgeon (presumably Walsh) applies a clear plastic face-suctioning device that seems to work pneumatically, pulling Archer's skin, fat, and a a few muscles, away from the deeper structures with a light, wet, sucking sound.

Because there was no incredibly wet ripping-noise foley, we must assume that they didn't show the hours of surgery it would take to free Archer's face from the fascia, muscle, and bone below, without tearing chunks of tissue or creating geysers of blood.

After all that, one of the surgeons decides to save time by cutting and dying Archer's hair DURING THE SURGERY. Cutting hair during surgery is so unhygienic! You could see those little bits of hair flying away from those scissors, and no matter how carful you were, eve with "laser sheers," some bacteria laden bits of hair would find their way into the wound site and contribute to a drippy infection later. Brrr!

As they place and manipulate Troy's facial skin over Archer's skull, you get a nice sense of the texture the the skin would have. They really got the right limp, leathery, fatty texture for that type of tissue. I was impressed!

The surgery is quick and bloodless, whereas the woman who had the partial face transplant last December was operated on for 23 hours, and I'm inclined to think there was more bleeding, even with cautery, for her procedure.

The saga of Face/Off continues, when Troy emerges from his coma!

Face/Off part 2 - new anti-inflammatories

NEW ANTI-INFLAMMATORIES

Walsh and Miller pitch the face transplant idea to Archer.  While trying to convince him that this cosmetic/transplantation procedure will be a snap, Walsh tells Archer, "with the new anti-inflammatories, healing takes days, not weeks."

Inflammation gets a bad reputation, but actually helps to stimulate acute wound healing.  The problem is that inflammatory reactions can get out of hand and secondary tissue death and/or delayed healing can be the result.  I'm curious what "new anti-inflammatory" might make it possible to heal from major surgery in "days, not weeks."  One interesting anti-inflammatory mediator I cam across is called Activated Protein C, or APC for short.  This stuff is great at healing rat skin(1) and seems like a very promising therapeutic agent for the healing of chronic wounds.  Even though the research I found dates from 2005 instead of 1997, kudos to screenwriters Mike Werb and Michael Colleary for hopping on the research train.

Image from Regrowhair.com

OTHER PROCEDURES

Walsh also tells Archer that they'll use "laser sheers" and micro plugs to alter his head and body hair.  Did you know that about 80% of all transplanted hair falls out within three weeks, then starts growing again(2)?  I love the idea of John Travolta and Nicholas Cage going about this movie with many looking bald patches on their heads and torsos.  Did they transplant leg hair too?  How many hours would that take?  A head can take hours.

Image from Wikipedia

This is a great line: "Your blood types won't match, but Pollux won't know that." But Pollux might get suspicious when Archer's face, which would actually be Troy's face, started turning black and sliding around.  The problem here is that blood typing is really important to transplanting.  Tissue rejection can happen within minutes to hours (acute rejection) from blood coagulation, if the donor and recipient don't have compatible blood types.  Tissue typing would also be a good idea if you were doing a transplant.  More on this in later posts.

Walsh also explains to Archer that abdominoplasty can be performed for his "love handles."  Abdominoplasy is often called a "tummy tuck."  The procedure involves "tightening" the abdominal musculature and fascia with sutures, repositioning the navel, cutting away redundant skin, and a little liposuction to get those extra areas of fat.  Does Troy get Archer's fat squirted into his abdominal fascia when he takes Archer's place?  Ew!  He might need some of that cut away skin to accommodate the extra fat.  Ick!  If he's on prednisone (an immune suppressive drug to prevent tissue refection) for long enough, he may develop a layer of abdominal fat caused by the drug, and not have to get Archer's fat squirted in there after all.

"REAL" SCIENCE

Walsh has been taking Archer around his facility, showing him the great strides he's made in surgery, tissue regeneration, and transplantation.  After talking about anti-inflammatory drugs and love handles, Walsh says "but here's the real science."

Face/Off

To give Archer Troy's face, Walsh is going to use a "state of the art Morphogenetic Template" which looks like a clear hard plastic facemask with blobs of putty inside it.  The inside is modeled on Archer's skull, the outside on Troy's skull, although the external surface is shaped like soft tissue and not bone.  The morpho plate (my nickname for it) doesn't have a separate jaw hinge, which should make speaking difficult, but we don't notice any speech impediments or inability to chew, post operation, so what do I know?

That the template is "morphogenetic" implies all sorts of things, and nothing at all.  Morphogenesis means the formation of an organism.  It can refer to cell formation, tissue formation, and also the organization of cells and tissues in a larger structure or organism.

So if I was the writer trying to justify the science, I might say that the morpho plate was impregnated (by lasers, of course) with some type of, I don't know... polymer?.... enzyme?... protein?... I'm trying to recall substance that previous movies have relied on for this kind of thing.  Ultimately the plate would be impregnated with something that promotes organized cell growth, as dictated by the DNA(3) of the cells in the donor tissue that has been laid over it.

Image from Wikipedia

Now, this part is unclear to me:  The remove Archer's skin, put the mask on him, and put Troy's skin over the mask to "fit the face on top."  Walsh will "simply connect the muscles, tear ducts, and nerve endings" and voila!  My confusion arises because some facial muscle run from bone to bone(4), some run from skin to skin(5), and some from bone to skin(6).  If they want to attach zygomaticus minor, how do they get the muscle from Archer's face through the mask to Troy's mouth-skin?  Or, how do they get Troy's muscle through the mask to the bone below?  Apparently they can do this because both men smile after their transplants.  Of course Archer (as Troy) is smiling ironically at the cruelty of his position, but it's still a smile.

Even with the "new anti-inflammatories," it takes time to build movement skills with parts that have undergone major surgery, or parts that were moved from one area to another, or parts that aren't originally yours.  As an example of the time it takes for this type of recovery, the woman who received the first face transplant in the United States in December of 2008 has a good prognosis.  she should have feeling return to her face in six months, and with physical therapy to retrain her muscles, she should be able to smile and have most function (speaking, eating, expression) return in about a year(7).  Archer has six days to have transplant surgery, recover full function, fool Pollux into revealing the location of the bomb, find it, and neutralize it.  That's a lot of pressure for his physical therapist.

One of my favorite things about this film is that everyone keeps saying, "this procedure is completely reversible."

Next time, the surgery!

1.  Jackson, Christopher J., et al. "Activated Protein C Prevents Inflammation Yet Stimulates Angiogenesis to Promote Cutaneous Wound Healing." Wound Repair & Regeneration 13.3 (2005): 284-94.

2.  "Hair Today, More Hair Tomorrow?" Harvard Health Letter 33.10 (2008): 1-3

3.  Yes, I know DNA is so 90s but this is a 90s film, so it would fit if they'd used it.

4.  E.g., the masseter which closes the jaw, attaches at the cheekbone and onto the jawbone.

5.  Obicularis oculi makes a sphincter around teh eye, just under the skin.  It is a blinker and a squinter.

6.  Zygomaticus minor runs fromt he cheekbone to tissue of the upper lip.  This muscle contributes to smiling and sneering derisively.

7.  Altman, Lawrence K.  "First U.S. Face Transplant Described."  The New York Times, December 18, 2008.  

Face/Off part 1

Here's the first post for a multiple installment analysis of John Woo's Face/Off.  

SYNOPSIS

For six years FBI agent Sean Archer (John Travolta) has been pursuing terrorist Castor Troy (Nicholas Cage), the murderer of Archer's young son.  Troy is finally captured, albeit in a comatose state.  Archer discovers that Troy and his brother, Pollux (Alessandro Nivola) have planted a bomb containing a nerve gas and a biological payload somewhere in LA.  Archer takes on Troy's identity by borrowing the skin and superficial fascia of his (Troy's) face in a hefty surgical procedure that also transforms his voice and body into a replica of Troy.  He heads off to prison as Troy, to trick Pollux, whose central nervous system is intact, into revealing the location of the bomb.  Troy awakens from his coma faceless, and insists on making use of Archer's face and looks.  He then murders the surgeons and agents who know about this top-secret project.  Now things get complicated.  No one but Troy and Archer knows that they are not themselves. Archer (posing as Troy) escapes from prison, to recover his face and his family. There is a lot of great action.  Archer reveals himself to his wife (Joan Allen) who types the men's blood (O- and AB) to discover the truth.  After more great action, Troy dies and Archer is restored "just the way he was."  He also gets a new adopted son, the offspring of Troy.  Balance is restored.

COMMENTARY

A friend of mine in med school couldn't stand this film.  She hated it!  It was so idiotic!  That surgery could never happen!  She took the whole thing very personally, which is too bad.  She missed a great film.

The key to the success of this movie is that everyone knows the premise is impossible and nobody cares.  I'd say the film even leans into that impossibility as hard as it can, mixing heavy doses of the preposterous with touches of accuracy and new directions in medical research.  Woo uses special effects and snappy dialogue to ignore or gloss over gargantuan obstacles to the success of a super-secret cosmetic alteration and transplantation project.

Let's look at some of the ideas this film invokes regarding transplantation surgery and healing from this type of operation.

THE "SCIENTIFIC EXPLANATION" SCENE

In this scene Troy is comatose, I assume due to head trauma incurred in the great action sequence during his arrest.  Archer visits Troy in the hospital ward where he lies in a stupor, sporting what looks like an oxygen feed up his nose.  Another FBI agent, Dr. Hollis Miller (played by CCH Pounder - lover her!) tells Archer that Troy isn't dead after all.  He's in a coma and "he's a turnip."  She then puts her cigarette out on Troy's arm.  Troy doesn't twitch.  His monitors blink regularly and don't alter tempos in the least.  This moment clearly demonstrates that, "In deep coma primitive avoidance reflexes may be absent"(1).  This means that you could put a giant glowing coal on Troy's arm and, if the damage to his brain were severe enough, he wouldn't respond.  I believe we were meant to understand that Troy was in a coma, not a vegetative state, even though he was called a "turnip"(2).  I'm no doctor, but I watch one on TV, and I suspect someone unresponsive to cigarette burns will core pretty low (below an 8 out of a possible 15) on the Glasgow coma scale(3).  That's not good in terms of prognosis of spontaneous recovery, even though this is a plot point later.

In order to impress Archer, and get him to agree to a risky and preposterous mission, the head surgeon, Dr. Malcolm Walsh (Colm Feore) leads him to a glass wall, behind which we see a team of surgeons building a new ear, from scratech, with red and blue lasers.  the ear is for an agent Loomis, injured during Troy's capture.

In order to build and ear, these lasers would have to be able to organize a number of different types of cells into a super organized arrangement of skin layers, superficial fascia, elastic cartilage, blood vessels, and a number of nervous structures.  the surgeons then attach the ear to Loomis, and seal the tissue with another laser. Later a laser is used as a cutting tool to perform surgery.

In the real world, lasers are being used to perform a number of different tasks from skin tightening to tumor removal(4).  When researching to see what has been done in the area of lasers and tissue regeneration, I found an abstract describing the use of lasers to stimulate cartilage cells to grow(5), and since one's ear is elastic cartilage, that's a big part of the wounded agent's ear graft.  The abstract was a little vague as to whether or not this approach will pan out in terms of its usefulness, or even if it really worked at all.  But, assuming it worked, I suspect that the cartilage cells stimulated by laster activity would grow in one big, undifferentiated lump.  Still, the way the film used lasers to generate and destroy tissues wasn't quite as far-fetched as one might think.  Well, okay.  It's pretty out there but I could find evidence of research (regardless of outcome) in this area, so you have to give the movie a little credit here.

Next time, we look at the "new anti-inflammatories!"

1.  Berkow, Robert.  "The Merck Manual of Diagnosis and Therapy."  Whitehouse Station, NJ: Merck Research Laboratories, 1992 p.1398

2. Wikipedia classifies turnips as true "root vegetables" as opposed to modified stems such as tubers or other root-like structures such as bulbs.

3.  "Merck" p. 1463  Yes, they have a point scale for comas.  you can score between 3 and 15.  The lower the score, the worse the prognosis.  3-5 means you will probably die.  Over 8 and your chances of recovery are good.  Troy must have been somewhere between 5-8 and had the help of a miracle.

4. Galewitz, Phil. "Multi-use Lasers Cast doctors in New Light." USA Today

5. Baumann, Marcus, et al.  "Influence of Wavelength, Power Density and Exposure Time of Laser Radiation on chondrocyte Cultures - an in-Vitro Investigaion."  Medical Laser Application 21.3 (2006): 191-8. Abstract.