Method Of Head Fixation Research Articles

Design and manufacturing of a head mask for fixation in stereotactic radiosurgery by the Gamma Knife® Icon™.

This study evaluates an alternative to the classical method of head fixation during Gamma Knife radiosurgery using a Leksell head frame. In the Gamma Knife® Icon™ model, a new method of head fixation is used by utilizing a thermal molded polymer mask that takes the shape of the patient's head before fixing the head to the table. However, this mask is for single use and quite expensive. We describe a new, very economical method to fix the head of the patient during radiosurgery. We used commercial, quite cheap material [polylactic acid (PLA)] plastic and made a 3D printing model for the patient's face, taking special measurements to put this mask and fix it on the Gamma Knife. The actual material cost is only $4 (100 times less than the original mask cost). The new mask efficiency was tested using the movement checker software, the same one used to measure the efficiency of the original mask. The newly designed and manufactured mask is quite effective for use with the Gamma Knife® Icon™, with a much lower cost, and it can be manufactured locally.

Pituitary adenoma treatment plan quality comparison between linear accelerator volumetric modulated arc therapy and Leksell Gamma Knife® radiosurgery.

The aim of this study was to compare radiosurgical treatment plan quality of a linear accelerator with Leksell Gamma Knife (LGK) for pituitary adenoma irradiation. Thirty pituitary adenoma patients were evaluated in this study. Treatment plans were prepared on LGK and stereotactic linear accelerator Varian TrueBeam STx. Volumetric Modulated Arc Therapy (VMAT) plans (21 plans with 2 coplanar arcs and 9 plans with 4 non-coplanar arcs) were calculated for linear accelerator. All the plans were evaluated in terms of conformity, selectivity, gradient index and organ at risk (OAR) sparing. VMAT produced dosimetrically comparable treatment plans to LGK regarding conformity and selectivity (New Conformity Index (NCI): 1.76 ± 0.65 for 4 arc VMAT, 2.33 ± 1,16 for 2 arc VMAT and 1.96 ± 0.71 for LGK; Selectivity Index (SI): 0.63 ± 0.16 for 4 arc VMAT, 0.51 ± 0.16 for 2 arc VMAT and 0.58 ± 0.17 for LGK). Gradient index (GI) was superior for LGK plans (GI: 2.74 ± 0.20 for LGK and 5.28 ± 2.29 for 4 arc VMAT). OAR sparing for optics, brainstem, and hypophysis was similar for both modalities while target volume coverage was maintained the same. Finally, treatment time resulted in favor of VMAT plans (in this study VMAT plans were almost 5 times faster than LGK treatment regarding beam on time). According to the results of this study stereotactic linear accelerator with VMAT treatment could be used as a reasonable alternative to LGK for pituitary adenoma radiosurgery but only if the same head fixation method accuracy and target volume delineation are maintained for both modalities.

The head fixation based on skull cap: An improved protocol used in single unit recording in the vestibular system

Single unit recording has an important application in neuroscience, especially in the vestibular system such as visual stabilization, posture maintenance, spatial orientation and cognition. However, single unit recording conducted in living animals is a demanding technique and non-ideal mechanical stability between the recording location of nerve tissues and the tip of microelectrode always results in failure to obtain successful recordings in the vestibular system. In order to improve the mechanical stability during single unit recording, we constructed a novel head fixation method based on skull cap. This article describes in detail how to construct this novel head fixation. Following the step-by-step procedure mentioned in this article will provide a high-quality mechanical stability for single unit recording in the vestibular system, allowing us to successfully record the nonlinear neural dynamic response over a big magnitude motion stimulation. This improvement of head fixation contributes to the in-depth understanding of the vestibular system.

Acrylic Resin Molding Based Head Fixation Technique in Rodents.

Head fixation is a technique of immobilizing animal's head by attaching a head-post on the skull for rigid clamping. Traditional head fixation requires surgical attachment of metallic frames on the skull. The attached frames are then clamped to a stationary platform resulting in immobilization of the head. However, metallic frames for head fixation have been technically difficult to design and implement in general laboratory environment. In this study, we provide a novel head fixation method. Using a custom-made head fixation bar, head mounter is constructed during implantation surgery. After the application of acrylic resin for affixing implants such as electrodes and cannula on the skull, additional resins applied on top of that to build a mold matching to the port of the fixation bar. The molded head mounter serves as a guide rails, investigators conveniently fixate the animal's head by inserting the head mounter into the port of the fixation bar. This method could be easily applicable if implantation surgery using dental acrylics is necessary and might be useful for laboratories that cannot easily fabricate CNC machined metal head-posts.

A minimally invasive approach to long-term head fixation in behaving nonhuman primates

We have designed a device for long-term head fixation for use in behaving nonhuman primates that is robust yet minimally invasive and simple to use. This device is a modified version of the halo system that is used in humans for cervical traction and stabilization after spinal column injuries. This device consists of an aluminum halo with four titanium skull pins offset from the halo by aluminum posts. The titanium pins insert onto small segments of cranially reinforcing titanium plate, which are attached to the skull with titanium cortex screws. The surgery involves four scalp incisions, placement of the reinforcing plates, insertion of the pins for attachment of the halo, and incision closure. After the halo is attached, the animal's head can be fixed to a primate chair using a custom-built attachment arm that provides three degrees of adjustability for proper positioning during behavioral tasks. We have installed this device on two Macaque monkeys weighing 7 and 10kg. The halos have been in place on these animals for up to 8 months without signs of discomfort or loss of fixation. Using this method of head fixation, we have been able to track the animals’ eye positions with an accuracy of less than two visual degrees while they perform behavioral tasks.

A motile human sperm head fixation method.

In a solution containing less than 5% seminal fluid, human sperm has a tendency to attach its head on the smooth surface of an object. Based on such a phenomenon, a simple method was developed to fix sperm head on the surface of glass slide. This method was demonstrated by studying caffeine effect on the tail movement of human sperm in phosphate buffered saline. By analysing the images recorded on a videocassette, caffeine, a well known stimulator of human sperm motility, was shown to induce an immediate increase of sperm TBF (tail beat frequency) and the amplitude of TBF increase was found to be larger in sperm with lower basal TBF value. This method can provide a flock of head-fixed motile sperm for a precise sperm tail movement assessment or for other purposes.

Acrosome reaction in the head-attached human sperm.

The physiological acrosome reaction of the sperm occurs on the surface of the oocyte. Although its occurrence on the zona pellucida is considered to be a specific response to zona compounds, whether the simple attachment itself could influence the reaction of motile spermatozoa to a fixed surface and promote onset of the reaction is questioned. A motile human sperm head fixation method was developed recently, through which a group of head-attached sperm can be established easily. These head-attached sperm were investigated for their acrosome reactions. After staining by fluorescein iso-thiocyanate conjugated peanut lectin (FITC-PNA), many head-attached spermatozoa (75.7%) were found to have undergone an acrosome reaction.

A novel method of head fixation for the study of rodent facial function

The rodent vibrissial system offers an excellent model for the study of both sensory and motor function. It has been widely employed to gather data pertaining to sensory and motor function involving the 5th and 7th cranial nerves and the central nervous system. Existing methods of head fixation for precise measurements of ocular and vibrissial function involve exposing the cranium and applying dental cement from which two or more threaded rods emerge. This common approach is suboptimal, requiring a relatively complicated implantation procedure, and results in a large, chronic interface between the scalp and environmentally exposed implant material attached to the skull. Here we describe a head fixation device that is inexpensive, easy to build, less prone to infection, preserves access to the cranial midline, and permits repeated measurements over many months.

Noninvasive head fixation for external irradiation of tumors of the head-neck area

To fully utilize the technical capabilities of radiation diagnostics and planning, a precise and reproducible method of head fixation is a prerequisite. We have adapted the Vogele-Bale-Hohner (VBH) head holder (Wellhöfer Dosimetrie, Schwarzenbruck, Germany), originally designed for frameless stereotactic operations, to the requirements of external beam radiotherapy. A precise and reproducible head fixation is attained by an individualized vacuum upper-dental cast which is connected over 2 hydraulic arms to an adjustable head- and rigid base-plate. Radiation field and patient alignment lasers are marked on a relocatable clear PVC localization box. The possibility of craniocaudal adjustment of the head plate on the base plate allows the system to adapt to the actual position of the patient on the radiotherapy couch granting tensionless repositioning. The VBH head holder has proven itself to be a precise yet practicable method of head fixation. Duration of mouthpiece production and daily repositioning is comparable to that of the thermoplastic mask. The new head holder is in routine use at our hospital and quite suitable for external beam radiation of patients with tumors of the head and neck.

An alternative and more cost effective method of delivery of radiotherapy in age related macular degeneration

AIMS/BACKGROUNDIn the past 5 years there has been a dramatic increase in the use of radiotherapy to treat subfoveal neovascular membranes (NVMs) in both Europe and the USA despite the...

Implication of sperm head agglutination induced by a V3 peptide (fragment 307-330, HIV-1 envelope protein gp120) solution.

Human semen is the main vehicle for the transmission of human immunodeficiency virus (HIV); therefore, the interaction of HIV with the sperm is worthy of study. The motile sperm head fixation method was used as an in vitro model system to demonstrate the interaction of sperm with the peptide of HIV envelope protein. A micropipette loaded with semen was put into phosphate-buffered saline (PBS) containing V3 peptide (HIV-1IIIB envelope protein, fragment 307-330) or C2 peptide (HIV-1IIIB envelope protein, fragment 254-274). The V3 peptide caused a significant number of head-to-head binding sperm while the C2 peptide did not. This V3 peptide carries a high positive charge, which may overcome the electrostatic resistance on the cell to bring the sperm together. An HIV-CD4+ cell attachment inhibitor, dextran sulfate (DS, molecular weight about 5000), enhanced the sperm head agglutination induced by the V3 peptide. DS is presumed able to bind with specific sites near the V3 domain of gp120 to induce conformational change so as to prevent the binding of anti-V3 monoclonal antibodies or CD4+ cells to the V3 domain. This study suggests that DS interacts directly with the V3 peptide to enhance the sperm head agglutination.

Magnolol protects human sperm motility against lipid peroxidation: a sperm head fixation method.

It was previously reported that magnolol, isolated from the Chinese medicinal herb Magnolia officinalis, had a potent inhibitory activity on lipid peroxidation. Since sperm motility could be suppressed by lipid peroxidation, this study examines the protective effect of magnolol on lipid peroxidation-suppressed sperm motility. FeSO4 was used to induced lipid peroxidation and sperm motility was expressed as tail beat frequency (TBF) measured with a sperm head fixation method. Magnolol at 10(-9) to 10(-7) M significantly reversed the FeSO4-suppressed TBF. Magnolol significantly inhibited the generation of malondialdehyde (MDA), the end product of lipid peroxidation, in sperm. Magnolol protected sperm motility by inhibiting lipid peroxidation in sperm.

Feasibility of patient immobilization for conventional cranial irradiation with a relocatable stereotactic frame.

The precision of patient repositioning and the firmness of immobilization are among the major determinants of the accuracy of radiation treatment delivery. A relocatable Gill-Thomas localizer (GTL) developed for neurosurgery and stereotactic radiotherapy achieves highly accurate relocation and immobilization and has been used successfully for fractionated stereotactic radiotherapy of intracranial lesions. The feasibility of using GTL for immobilization in conventional fractionated external beam radiotherapy was assessed by comparison with conventional Cabulite shell head fixation. The GTL was well tolerated at the time of preparation and during a 5 week course of radiotherapy. The principal advantage was superior relocation accuracy maintained throughout the course of treatment, high precision of field set-up and markedly reduced production time. In addition the time taken to position the patient in the treatment room was also marginally shortened. GTL is therefore a feasible method of head fixation for conventional cranial irradiation providing patients have adequate dentition. With further development the relocatable method of immobilization originally designed for stereotactic radiotherapy may become the preferred technique particularly in situations where high accuracy is desirable, such as stereotactically guided conformal radiotherapy.

Computed tomography: immobilization of the head by dental holder.

Movement of the patient's head during computed tomographic studies with the EMI scanner causes some degradation of the quality of the examination. With sufficient movement, major artifacts appear which may obscure intracranial pathology. A simple method of head fixation, utilizing a dental mold, greatly reduces the incidence of unsatisfactory scans.