Posts tagged neurosurgery

As brain surgeons test new procedures and drugs to treat conditions ranging from psychiatric disorders to brain cancer, accuracy is becoming an ever-greater issue.

In treating the brain, the state of the art today starts with images from a magnetic resonance (MR) scanner, usually made a few days before surgery. Then, in the operating room, multiple cameras track instruments as they are inserted through a hole in the skull, creating images that can be superimposed on the original MR scans.

But there is no guarantee that the brain will not shift slightly during the surgery and throw off the best efforts at exact guidance.

For 20 years, neurosurgeons have discussed a radical way to achieve real-time accuracy in placement: performing surgery with the brain inside an MR machine, says Walter Block, professor of biomedical engineering at the University of Wisconsin-Madison. “When you open the brain for surgery, the tissue can shift slightly, and that will throw off predictions made in advance.”

To bring the full promise of MR into the operating room, Block has formed a company called InseRT MRI to develop software that allows surgeons to observe the brain in real time on an MR machine during surgery.

Such a system would have a number of applications, he says. Drugs for brain cancer can be delivered over as long as 54 hours. “It would be valuable to see where the drug is going during the first few hours,” Block says. “Drugs move at different rates through gray and white matter, and this ability to recalibrate the treatment plan, based on actual data on where the drug is moving, would allow you to alter the location of the catheter or the flow rate of the medication.”

To get that accuracy advantage, Block does not envision forcing surgeons to learn a new operating environment. “Surgeons have operating room tools and work stations that are familiar to them,” he says. “We are creating a set of tools that make the MR space a comfortable place for the surgeon.”

UW-Madison neurosurgeon Azam Ahmed plans to use the system through test procedures on animal brains and cadavers, Block says. “We are working with Dr. Ahmed to design the workflow so it’s intuitive to him. We are not going to piggyback on top of a large scanner market designed for largely diagnostic purposes, kludging it to make it work for interventional applications.”

The goal is not to develop software that could be spliced into MR manufacturers’ systems, he says, “since every time they alter their software, we would have to change ours.” Instead, Block is borrowing tactics from the smartphone industry. “People write apps that use various phone resources — GPS, the screen, the orientation system. We look at the MR scanner as a set of resources that we can control. An app writer does not have to go to Samsung or Apple and say, ‘We have this idea.’”

Block says his software will interact with the MR machine through a software “portal” being developed by another firm.

One obvious market is the pharmaceutical industry. “Any drug trial in the brain will cost hundreds of millions of dollars,” he says, “and we often see trials being repeated after post-mortem analysis raises questions about the accuracy of drug placement.”

Targeted surgery could also help remove bits of brain tissue to treat severe epilepsy. Marvel Medtech in Cross Plains, Wisconsin, is developing a system that would employ InseRT MRI’s guidance to biopsy breast tumors. The technology also raises the potential for localized psychiatric drug therapy, Block says.

In the brain, the MR-guidance system is already accurate to less than a millimeter, Block says. While conventional stereotactic systems can approach that accuracy “in the best case,” the error can rise to 1.5 or 2 millimeters — a vast distance in an organ as delicate as the human brain, in which damage to healthy tissue must be minimized.

Block says InseRT MRI’s competitive advantage resides in his long experience in medical imaging. “Our value is (faster) time to market. We have come up with ways to circumvent the significant hurdles that now limit image-guided therapy, and we believe we can do this faster than anybody else.”

(Source: news.wisc.edu)

Johns Hopkins researchers have devised a computerized process that could make minimally invasive surgery more accurate and streamlined using equipment already common in the operating room.

In a report published recently in the journal Physics in Medicine and Biology, the researchers say initial testing of the algorithm shows that their image-based guidance system is potentially superior to conventional tracking systems that have been the mainstay of surgical navigation over the last decade.

“Imaging in the operating room opens new possibilities for patient safety and high-precision surgical guidance,” says Jeffrey Siewerdsen, Ph.D., a professor of biomedical engineering in the Johns Hopkins University School of Medicine. “In this work, we devised an imaging method that could overcome traditional barriers in precision and workflow. Rather than adding complicated tracking systems and special markers to the already busy surgical scene, we realized a method in which the imaging system is the tracker and the patient is the marker.”

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Anesthesia may have lingering side effects on the brain, even years after an operation

Two and a half years ago Susan Baker spent three hours under general anesthesia as surgeons fused several vertebrae in her spine. Everything went smoothly, and for the first six hours after her operation, Baker, then an 81-year-old professor at the Johns Hopkins Bloomberg School of Public Health, was recovering well. That night, however, she hallucinated a fire raging through the hospital toward her room. Petrified, she repeatedly buzzed the nurses’ station, pleading for help. The next day she was back to her usual self. “It was the most terrifying experience I have ever had,” she says.

Baker’s waking nightmare was a symptom of postoperative delirium, a state of serious confusion and memory loss that sometimes follows anesthesia. In addition to hallucinations, delirious patients may forget why they are in the hospital, have trouble responding to questions and speak in nonsensical sentences. Such bewilderment—which is far more severe than the temporary mental fog one might expect after any major operation that requires general anesthesia—usually resolves after a day or two.

Although physicians have known about the possibility of such confusion since at least the 1980s, they had decided, based on the then available evidence, that the drugs used to anesthetize a patient in the first place were unlikely to be responsible. Instead, they concluded, the condition occurred more often because of the stress of surgery, which might in turn unmask an underlying brain defect or the early stages of dementia. Studies in the past four years have cast doubt on that assumption, however, and suggest that a high enough dose of anesthesia can in fact raise the risk of delirium after surgery. Recent studies also indicate that the condition may be more pernicious than previously realized: even if the confusion dissipates, attention and memory can languish for months and, in some cases, years.

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NIBIB-funded scientists and engineers are teaming up with neurosurgeons to develop technologies that enable less invasive, image-guided removal of hard-to-reach brain tumors. Their technologies combine novel imaging techniques that allow surgeons to see deep within the brain during surgery with robotic systems that enhance the precision of tissue removal.

A robot that worms its way in

The median survival rate for patients with glioblastomas, or high grade primary brain cancer, is less than two years. One factor contributing to this low rate is the fact that many deep-seated and pervasive tumors are not entirely accessible or even visible when using current neurosurgical tools and imaging techniques.

But several years ago, J. Marc Simard, M.D., a professor of neurosurgery at the University of Maryland School of Medicine in Baltimore (UMB), had an insight that he hoped might address this problem. At the time, he had been watching a TV show in which plastic surgeons were using sterile maggots to remove damaged or dead tissue from a patient.

“Here you had a natural system that recognized bad from good and good from bad,” said Simard. “In other words, the maggots removed all the bad stuff and left all the good stuff alone and they’re really small. I thought, if you had something equivalent to that to remove a brain tumor that would be an absolute home run.”

Image: Initial prototype for the minimally invasive neurosurgical intracranial robot. Image courtesy of University of Maryland.

And so Simard teamed up with Rao Gullapalli, Ph.D., professor of diagnostic radiology and nuclear medicine also at UMB, as well as Jaydev Desai, Ph.D., professor of mechanical engineering at the University of Maryland, College Park, to develop a small neurosurgical robot that could be used to remove deep-seated brain tumors.

Within four years, the team had designed, constructed, and tested their first prototype, a finger-like device with multiple joints, allowing it to move in many directions. At the tip of the robot is an electrocautery tool, which uses electricity to heat and ultimately destroy tumors, as well as a suction tube for removing debris.

“The idea was to have a device that’s small but that can do all the work a surgeon normally does,” said Simard. “You could place this small robotic device inside a tumor and have it work its way around from within, removing pieces of diseased tissue.”

A key component of the team’s device is its ability to be used while a patient is undergoing MRI. By replacing normal vision with continuously updated MRI, the surgeon is able to visualize deep-seated tumors and monitor the robot’s movement without having to create a large incision in the brain.

In addition to reducing incision size, Simard says the ability to view the brain under continuous MRI also helps surgeons keep track of tumor boundaries throughout an operation. “When we’re operating in a conventional way, we get an MRI on a patient before we do the surgery, and we use landmarks that can either be affixed to the scalp or are part of the skull to know where we are within the patient’s brain. But when the surgeon gets in there and starts to remove the tumor, the tissues shift around so that now the boundaries that were well-established when everything was in place don’t exist anymore, and you’re confronted once again with having to distinguish normal brain from tumor. This is very difficult for a surgeon using direct vision, but with MRI, the ability to discriminate tumor from non-tumor is much more powerful.”

Steve Krosnick, M.D., a program director at NIBIB, says real-time MRI guidance during brain tumor surgery would be a tremendous advantage. “Unlike pre-operative MRI or intermittent MRI, which requires interruption of the surgical procedure, real-time intra-operative MRI offers rapid delineation of normal tissue from tumor while accounting for brain shifts that occur during surgery.”

But designing a neurosurgical device that can be used inside an MRI magnet is no easy task. One of the first issues you have to consider, said Gullapalli, is a surgeon’s access to the brain. “When you scan a person’s brain during an MRI, he’s deep inside the machine’s tunnel. The problem is, how do you get your hands on the brain while the patient’s in the scanner?”

The team’s solution was to give the surgeon robotic control of the device in order to circumvent the need to access the brain directly. In other words, a surgeon can insert the robot into the brain while the patient is outside of the scanner. Then, when the patient moves into the scanner, the surgeon can sit in a different room and –while watching MRI images of the brain on a monitor—move the robot deep inside the brain and direct it to electrocauterize and aspirate the tissue.

Jaydev Desai, the team’s mechanical engineer, says the most challenging aspect of the project has been designing a robot that can be controlled inside the magnetic field of an MRI. While robots are often controlled via electromagnetic motors, this was not an option because, besides being magnetic, these motors create significant image distortion, making it impossible for the surgeon to perform the task. Other potential mechanisms such as hydraulic systems were off the table due to concerns about fluid leakage.

Instead, Desai decided to use shape memory alloy (SMA)—a material that alters its shape in response to changes in temperature—to control the robot’s movement. In the most recent prototype—developed by Desai and his team at the Robotics, Automation, and Medical Systems (RAMS) laboratory at the University of Maryland, College Park—a system of cables, pulleys and SMA springs are used. This cable and pulley system is an improvement from their previous prototype which caused some image distortion.

Image: The newest prototype for the minimally invasive neurosurgical intracranial robot uses a system of pulleys and springs to move the robot. Source: Jaydev Desai, University of Maryland

With continued support from NIBIB, Desai and colleagues are now working to further reduce image distortion and to test the safety and efficacy of their device in swine as well as in human cadavers. Though it will be several years before their device finds its way into the operating room, Simard is excited by the prospect. “Advancing brain surgery to this level where tiny machines or robots could navigate inside people’s heads while being directed by neurosurgeons with the help of MRI imaging…It’s beyond anything that most people dream of.”

Scoping the brain

On the opposite side of the country, a different group of engineers and neurosurgeons is also working to develop an image-guided, robotically-controlled neurosurgical tool. Lead by Eric Seibel, Ph.D., a professor of mechanical engineering at the University of Washington, the team is attempting to adapt a scanning fiber endoscope—a tool initially developed by Seibel to image inside the narrow bile ducts of the liver—so that it can be used to visualize the brain during surgery.

An endoscope is a thin, tube-like instrument with a video camera attached to its end that can be inserted through a small incision or natural opening in the body to produce real-time video during surgery. Endoscopes are an essential component of minimally invasive surgeries because they allow surgeons to view the inside of the body on a monitor without having to make a large incision.

However, there are many parts of the body such as small vessels and ducts as well as areas deep in the brain that are inaccessible to conventional endoscopes. Although ultrathin endoscopes have recently been developed, Seibel says these smaller scopes come with the price of greatly reduced image resolution.

“Right now, with the current state of the art ultrathin endoscopes, I calculate based on the field of view and their resolution that the person looking at that display would see so little as to be classified in the US as legally blind,” said Seibel.

Image: Microfabricated optical fiber scanner emitting red laser light, with scan amplitude of 1 mm peak-to-peak. Image courtesy of Eric Seibel, University of Washington

But with support from NIBIB over ten years ago, Seibel began working on a new type of endoscope that could fit into tiny crevices in the body while retaining high image quality. His end product was a new type of endoscope that, despite having the diameter of a toothpick, can provide doctors with microscopic views of the inside of the body.

Seibel retained image quality while significantly reducing the size of his scope by eschewing traditional endoscope models. Instead of a light source and a video camera, Seibel’s scope consists of a single optical fiber—approximately the size of a human hair—located in the middle of the scope. The fiber releases white laser light (a combination of green, red, and blue lasers) when vibrated at a particular frequency. By directing the laser light through a series of lenses in the scope, it can be reflected widely within the body, providing a 100 degree field of view. As the white laser light interacts with tissue, it picks up coloration and scatters it back to a ring of additional optical fibers which transmit this information to a monitor.

“It’s almost like putting your eyes inside the body so you can see with the wide field view of your human vision,” said Seibel.

In collaboration with three neurosurgeons and an electrical engineer, Seibel is now working to secure his novel endoscope to the tip of a robotically controlled micro-dissection neurosurgical tool.

As opposed to larger traditional endoscopes, Seibel say his scanning fiber endoscope is barely noticeable.

“It’ s like a piece of wet spaghetti,” said Seibel. “It’s even smaller then a piece of wet spaghetti in diameter, but it feels like that. So when it is actually at the tip of the surgeon’s tool, the surgeon wouldn’t feel it dragging behind her.”

One advantage of having the endoscope under robotic control is that the brain can be imaged at a higher magnification.

“A surgeon couldn’t hold a microscope steady in her hand while performing surgery, but the robot can,” said Seibel.

Microscopic detail is essential when trying to determine the border between healthy tissue—which if removed could lead to neurological deficits—and cancerous tissue—which if left in the brain could allow a tumor to return.

Krosnick says he’s excited by the combination of high-quality imaging and robotic enabled micro-neurosurgery. “It addresses a critical need, which is to discern tumor margins at high resolution while minimizing disruption to normal structures.”

Seibel believes this discrimination between cancerous and healthy tissue could be enhanced even further by taking advantage of the fact that his scanning endoscope is also able to detect fluorescence. One of the main focuses of his current research is a collaboration with Jim Olson, M.D., Ph.D. at the Fred Hutchinson Cancer Research Center, who is the inventor of a substance called “tumor paint”.

Tumor paint is a fluorescent probe that attaches to cancerous but not healthy cells when injected into the body. Seibel says the ultimate goal would be to give a patient an injection of tumor paint and then use his endoscope to create an image of the fluorescing cancer cells as well as a colored anatomic image of the brain. The two images could then be merged on a screen for the surgeon to view during an operation.“You would be able to see all the structure that a surgeon would see, but you’d also see those molecular pinpoints of light that are cancer cells…and from there the robot can be used to resect, or remove, these small cells of cancer, and it can do it very precisely because you don’t have the shaking of a human holding it.”

Image: Tumor paint is made of a compound extracted from scorpion venom that can travel through the blood brain barrier and bind specifically to tumor cells. Source: iStockphoto

Seibel concluded by saying, “There’s a real niche for video-quality, high-resolution, multi-modal imaging that’s in a tiny package so that it can be put on microscopic tools for minimally invasive medicine. I really feel it’s an enabling technology that could move the whole field forward.”

Krosnick is enthusiastic about the progress the two teams have made so far. “These are innovative technologies that, if effective, could significantly add to the brain surgery armamentarium. They’re still early in development, but I think both show considerable promise.” He concluded by emphasizing that, like all new devices, these technologies would need to undergo a series of clinical trials to ensure that they are safe and effective before making their way into an operating room.

(Source: nibib.nih.gov)

A multi-center study supports the effectiveness of the newest technology available for the treatment of difficult, life-threatening brain aneurysms. The technology, the Pipeline embolization device, is a flow diverter that redirects blood flow away from wide-necked or giant aneurysms that cannot be treated in more conventional ways.

Andrew Ringer, MD, director of the division of cerebrovascular surgery and professor of neurosurgery and radiology at the University of Cincinnati (UC) College of Medicine, led the Cincinnati portion of the study, which was published in the December issue of Neurosurgery.

"The study showed that the Pipeline device is a safe and effective tool for patients and surgeons," says Ringer, a Mayfield Clinic neurosurgeon who has treated 11 patients with the device. "This expands our ability to safely treat aneurysms that were very difficult to treat before."

(Source: sciencedaily.com)

When initial computed tomography (CT) scans show bleeding within the brain after mild head injury, decisions about repeated CT scans should be based on the patient’s neurological condition, according to a report in the January issue of Neurosurgery, official journal of the Congress of Neurological Surgeons. The journal is published by Lippincott Williams & Wilkins, a part of Wolters Kluwer Health.

The study questions the need for routinely obtaining repeated CT scans in patients with mild head trauma. “The available evidence indicates that it is unnecessary to schedule a repeat CT scan after mild head injury when patients are unchanged or improving neurologically,” according to the study by Dr. Saleh Almenawer and colleagues of McMaster University, Hamilton, Ont., Canada.

Are Repeated Scans Necessary after Mild Head Trauma?

In a review of their hospital’s trauma database, the researchers identified 445 adult patients with mild head injury who had evidence of intracranial hemorrhage (ICH)—bleeding within the brain—on an initial CT scan. In many trauma centers, it’s standard practice to schedule a second CT scan within 24 hours after ICH is detected, to make sure that the bleeding has not progressed.

To evaluate the need for routine repeated scans, Dr. Almenawer and colleagues looked at how many patients needed surgery or other additional treatments, and whether the change in treatment was triggered by changes in the patients’ neurological condition or based on the routine CT scan alone. (For patients whose neurological condition worsened, CT was performed immediately.)

Overall, 5.6 percent of the patients required a change in treatment after the second CT scan. Most of these patients underwent surgery (craniectomy) to relieve pressure on the brain. Nearly all patients who underwent further treatment developed neurological changes leading to immediate CT scanning.

Just two patients had a change in treatment based solely on routine repeated CT scans. Both of these patients received a drug (mannitol) to reduce intracranial pressure, rather than surgery

Decisions on CT Scans Can Be Based on Neurological Status

Dr. Almenawer and colleagues extended the same method to patients reported in 15 previous studies of CT scanning after mild head injury. Including the 445 new patients, the analysis included a total of 2,693 patients. Overall, 2.7 percent of patients had a change in management based on neurological changes. In contrast, just 0.6 percent had treatment changes based on CT scans only.

Bleeding within the brain is a potentially life-threatening condition, prompting routine repeated CT scans after even mild head injury. The researchers write, “Although CT scanners are very useful tools, in an era of diminishing resources and a need to justify medical costs, this practice needs to be evaluated.” Each scan also exposes the patient to radiation, contributing to increased cancer risk.

The new study questions the need for routine repeated CT scans, as long as the patient’s neurological condition is improving or stable. “In the absence of supporting data, we question the value of routine follow-up imaging given the associated accumulative increase in cost and risks,” Dr. Almenawer and coauthors conclude.

Neurological examination is the “simple yet important” predictive factor leading to changes in treatment and guiding the need for repeat CT scanning after mild head injury, the researchers add. They emphasize that their findings don’t necessarily apply to patients with more severe head injury.

(Source: newswise.com)