DTI guides brain tumour resection
Diffusion tensor imaging (DTI), an MR technique that measures the diffusion of water molecules, could prove of great value in planning surgical resection of brain tumours. Researchers at New York University School of Medicine (New York, NY) used DTI to study six children with juvenile pilocytic astrocytoma (JPA), a benign brain tumour. The technique enabled visualization of nerve fibre bundles in the brain, thus maximizing the potential of completely removing the tumour while avoiding damage to nearby critical fibre bundles (J. Neurosurg: Pediatrics 4 495).
The surgical approach to JPA resection is dictated by the location of the displaced normal thalamus and posterior limb of the internal capsule (PLIC). In all six cases, DTI confirmed the expected location of the PLIC, as seen with conventional MRI. In one patient, DTI identified unexpected deviation of the PLIC, which proved useful in tailoring the surgery. "This study showed that using advanced MRI technology can help identify distorted nerve fibre bundles around brain tumours," said Jeffrey Wisoff, director of the Division of Pediatric Neurosurgery at NYU Langone Medical Center. "This allows an otherwise inoperable tumour to be completely removed, which can hopefully lead to a cure."
Deep brain stimulation reduces epilepsy seizures
Long-term data from a randomized, double-blind study of deep brain stimulation (DBS) therapy for epilepsy reveal that the treatment led to a significant reduction in seizure frequency, compared to a control group. The study, called SANTE, involves stimulating the left and right anterior nucleus of the thalamus with a DBS system from Medtronic (Minneapolis, MN), used in conjunction with epilepsy medications. DBS therapy led to a median reduction in seizure frequency of 41% at one year, 56% at two years, and 68% at three years of therapy, compared to baseline.
Of the original 110 patients who received DBS implants in the trial, 91 remain active in the study, including some who have received DBS therapy for more than five years. "DBS therapy holds promise for patients with epilepsy who are severely affected and have not had success with other treatments, including medications, and in some cases, vagus nerve stimulation or even surgery," explained principal investigator Robert Fisher, director of Stanford Epilepsy Center. Medtronic announced the results at the American Epilepsy Society Meeting, held earlier this month in Boston, MA.
Blasted metals detect elusive terahertz rays
Blasting a metal with high-intensity femtosecond laser pulses can cause dramatic changes in its surface, altering its absorption properties. Now, researchers at the University of Rochester (Rochester, NY) have discovered that, as well as changing colour, the altered metals become efficient in absorbing terahertz radiation (T-rays), a frequency that has previously been challenging, if not impossible, to detect.
T-rays, which excite rotational and vibrational states of organic compounds, offer the capability to interrogate tissues at the cellular level. The radiation is also non-ionizing, which could be important for future medical applications. "When we turned metals black, we knew that they became highly absorptive in the visible wavelength range," explained optics professor Chunlei Guo. "Here, we experimentally demonstrated that the enhanced absorption extends well into the far infrared and terahertz frequencies."
Variable doses raise CT safety concerns
A study headed up at the University of California, San Francisco, has shown that radiation doses from CT exams vary widely, and are higher than generally thought. The researchers examined the radiation exposure associated with the 11 most common clinical CT procedures, and estimated the associated potential cancer risks. They reviewed procedures performed on 1119 patients at four institutions over five months, examining three areas: head and neck, chest, and abdomen and pelvis (Arch. Intern. Med. 169 2078).
The results revealed that radiation doses were generally higher than typically reported, and that there was a mean 13-fold variation between the highest and lowest dose for each procedure. "In day-to-day clinical practice, we found significant variation in the radiation doses for the same type of CT procedures within institutions and across institutions," said lead investigator Rebecca Smith-Bindman. "Our results highlight the need for greater standardization because this is a medical safety issue." She notes that the doses patients receive during actual CT exams differ from phantom doses, and suggests that documenting these actual doses could help reduce radiation exposure and associated risks.
Cancer-killing nanoparticles tracked with MRI
Researchers at Rice University and Baylor College of Medicine (Houston, TX) have created a nanoparticle that can be tracked in real time with MRI as it homes in on cancer cells, tags them with a fluorescent dye and destroys them with heat. The particles comprise nanoshells modified with a fluorescent dye. The researchers found that the dye molecules emitted 40–50 times more light if a gap of few nanometres was left between them and the surface of the nanoshell. A layer of iron oxide, which can be detected with MRI, was inserted into this gap. The particles were also functionalized with an antibody that binds to the surface of breast and ovarian cancer cells (Adv. Funct. Mater. doi: 10.1002/adfm.200901235).
The team tracked the fluorescent particles and confirmed that they could target cancer cells and destroy them via photothermal actuation. The next step will be to destroy whole tumours in live animals. While testing in humans is at least two years away, the team's ultimate goal is to create a system in which a patient receives nanoparticles with antibodies tailored for their particular cancer. Using NIR imaging, MRI or a combination, doctors would observe the particles' progress through the body, identify areas where tumours exist and destroy them.
Radiation oncologists count on advanced imaging
Almost all radiation oncologists now employ advanced imaging techniques for radiotherapy target delineation, according to a study from the University of California, San Diego (La Jolla, CA). A survey of 386 respondents revealed that 95% of physicians were using such advanced imaging methods in their practice, including nearly 50% who used novel techniques like 4DCT (JACR 12 876).
"FDG-PET and MRI were the most common technologies used, with nearly 75% of respondents using one or both," said lead author Loren Mell. "Utilization of advanced imaging technologies for target delineation appears to have increased significantly in recent years and the frequency of utilization is expected to increase even further."