Dynamic stereotactic radiosurgery: the Charleston program: a report on the first 150 patients.

We have been pleased with our initial experience in an evolving program. As newer surgical and radiotherapy techniques have become available, the role of radiosurgery has been and will continue to be modified. As more commercially available systems have been marketed, the availability will become more widespread. A battery of residents in neurosurgery and radiation oncology trained in these technologies will provide leadership and future directions of this therapy.

Treatment planning optimization for multiple arcs stereotactic radiosurgery using a linear accelerator.

PURPOSE: Multiarc stereotactic radiosurgery is a technique used to irradiate an intracranial tumor with minimal damage to the surrounding normal tissue. The purpose of this paper is to present a method for and the results from optimizing three dimensional (3D) treatment dose for multiarc stereotactic radiosurgery. METHODS AND MATERIALS: The normal procedure for a physician-physicist team designing a treatment plan for multiarc stereotactic radiosurgery is the trial-and-error approach of changing the collimator size and the isocenter of radiation by viewing the isodose curves on a two dimensional (2D) computed tomography (CT) or magnetic resonance imaging (MRI) image plane. Not only is this time consuming, but the resulting treatment plan is not optimal in most, if not all, cases. One reason for such nonconformal isodose curves is that the same collimator size is used for all arcs. However, it is very difficult to determine manually the different collimator sizes for different arcs. A derivative free optimization method is used to optimize the collimator size for each arc, as well as the 3D coordinates of the isocenter(s). RESULTS: One spherical and two ellipsoidal artificial tumors, and one actual tumor, were used to show the utilities of the optimization process. The 90% isodose curves resulting from optimization conform very well with the tumor; whereas the 90% isodose curves from the conventional method either do not envelop the entire tumor when the collimator size is too small, or a large volume of normal tissue is also irradiated by the 90% dose when the next larger collimator size is used. CONCLUSIONS: When the collimator size for each arc and the location of the isocenters(s) are optimized in a multiarc stereotactic surgery treatment plan, the 90% isodose curve conforms to the tumor much better than when the same collimator size is used for all arcs.

Dynamic stereotactic radiosurgery using a linear accelerator.

We describe a system for stereotactic radiosurgery with a linear accelerator. This technique allows treatment of small (less than 40 mm diameter) intracranial lesions, including vascular malformations, and primary and metastatic tumors that are deep within the brain or in areas not amenable to open surgery. A beam of ionizing radiation (1800 to 2500 cGy) is focused on the center of the lesion, which is determined by stereotactic localization. "Dynamic rotation" of the linac gantry and table continuously about this predetermined point ensures that only the lesion receives the full radiation dose, while the normal structures in the head receive minimal amounts of radiation. The system combines, for the first time in one place, elements of radiosurgical technique developed at various centers. Testing for accuracy compares favorably with results at other centers using linac-based systems as well as comparing favorably with the gamma knife.

Intraperitoneal P-32 after negative second-look laparotomy in ovarian carcinoma.

Thirty-one patients underwent a negative second-look laparotomy between 1976 and 1986. Fourteen patients received intraperitoneal chromic phosphate (P-32) after a negative second-look laparotomy. There has been no local recurrence (zero of 14) and no deaths attributable to recurrent disease. Local control and disease-free survival are 100%, with a minimum follow-up of 2 years and a mean follow-up of 4 years. Seventeen patients received no further therapy because of patient refusal, poor diffusion, or other contraindications to P-32 installation. Four of 17 patients undergoing negative second-look procedures without the addition of P-32 have subsequently recurred. This difference is highly suggestive (P = .076). There have been no major complications with the addition of P-32. The use of intraperitoneal P-32 after negative second-look laparotomies on ovarian carcinoma is well tolerated and effective in preventing recurrence.

Swelling of multicellular spheroids induced by hyperthermia.

EMT6 multicellular spheroids invariably swell by 10 to 50 per cent after incubation at 43 to 45 degrees C for 1 h. Both scanning electron and optical microscopy reveal morphological alterations particularly in the outer region of the spheroids. While the control cells are contiguous to one another and tightly held to the spheroid body, the heated spheroids exhibit partially disrupted contacts among cells. Measurements of intercellular volume and water volume of spheroids with labelled water and inulin show that changes in the spheroid volume are not due to an increase in cell volume, but that they can be explained by a 60-100 per cent increase in the intercellular space within a spheroid. Continuous observation of individual spheroids heated to 43-45 degrees C shows loss of adhesion of cells in the outer region and even detachment of a few surface cells. This 'melting' of the spheroid surface appears to result from a disorder in the extracellular material. Treatment with cell swelling agents such as hypotonic solution, ouabain, excess extracellular potassium ions, or ionophore nigericin, K+/H+ exchanger, each separately causes the spheroids to swell at the control temperature. On the other hand, A23187, Ca2+ ionophore, causes shrinkage of the spheroids. Thus, under hyperthermia, the volume of spheroids increases due to the disruption in the cell organization in their outer region.

Use of silicone fluids in studies of cellular amino acids.

In numerous cellular studies, cells labeled with radioisotopes have been separated from the labeling medium by an aqueous solution in order to determine the quantity of internalized labels; however, the aqueous wash tends to remove significant labeling from the cells. Therefore, in order to preserve all of the internalized labels, non-aqueous medium such as silicone fluids may be used. The termination of the labeling is achieved in the silicone method when, upon centrifugation, the cells separate from the medium and enter the silicone fluid to sediment to the tube bottom. This sedimentation of cells placed above a layer of silicone fluid exhibits a critical dependence on the centrifugal force, and gives rise to an uncertainty of only 2 s in determining the time of separation of cells from the medium using General Electric F-50 silicone fluid and a modified Beckman J2-21 centrifuge. It is therefore possible to determine the kinetics of incorporation of labeled amino acids into intracellular pools and proteins. In particular, since this silicone wash method determines the size of the total pool and the aqueous wash method determines the size of the acid-extractable pool, the simultaneous measurements of the size of both pools leads to the determination of the kinetics of labeling of the free amino acid pool. Among many possible applications and extensions of these methods, the studies of formation of intracellular pools and relations among different pools of transported molecules, such as water and amino acids, appear promising.

Mobilization of amino acids in tumor cells by hyperthermia.

When p815 mastocytoma cells are heated to 43 degrees C from 37 degrees C, pools of individual amino acids and the total amino acid pool increase significantly, the latter reaching a new plateau within 20 minutes. The increase in the total amino acid pool may reach as much as 75 mOsm per liter of cell water or 26% of the cellular osmolarity. The source of this excess amino acid is not due to an accelerated degradation of proteins, but either to the amino acids left behind by slowed protein synthesis or to the accelerated transport of extracellular amino acids into the cell. The excess amino acid should increase the osmolarity and the cell volume. Evidence suggests that the cell volume increase triggers the osmoregulatory process to reduce the contents of major ions.

Dosimetry of auricular keloid irradiation.

The incidental radiation dose of lithium fluoride thermoluminescence dosimeters was recorded during 15 treatments of patients with auricular keloids. Two half-value layers were used, and the results were compared. In both instances, the homolateral lens and thyroid received twice the contralateral dose. The oropharynx dose exceeded the thyroid dose.

Megavoltage therapy in patients with aneurysmal bone cysts.

Three adolescent patients with similar destructive lesions involving the pelvis were found to have unresectable aneurysmal bone cysts. All 3 patients appear to have permanent control and good function from 2 to 7 years after megavoltage irradiation with 4,000 rads. No complications or late sequelae have occurred, and follow-up radiographs demonstrate reconstitution and calcification of the affected bone. A slightly lower dose may be just as effective in controlling such lesions.