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Biomedical subjects

R Muller-Runkel

Publications and source records attributed to R Muller-Runkel.

17 recordsLinked to original sources
PubMed1992

Therapeutic gain with hyperfractionation in prophylactic cranial irradiation of children with acute lymphoblastic leukemia.

IQ deterioration after prophylactic cranial irradiation is a dreaded complication for children with acute lymphoblastic leukemia. Alternate treatment schemes are needed that achieve comparable tumor control, but avoid such long-term complication. To this end, a hyperfractionated treatment scheme is proposed. Using two different radiobiological models, we analyze the doses required to achieve equivalent disease control while reducing the severity of late sequelae. Analysis based on the linear-quadratic and surviving fractions models clearly indicates a therapeutic gain with hyperfractionation.

Brain Neoplasms↗
PubMed1992

Hyperfractionated, twice-a-day, radiotherapy may decrease IQ deterioration due to prophylactic cranial irradiation in childhood acute lymphoblastic leukemia: a radiobiological analysis.

High cure rates in childhood acute lymphoblastic leukemia (ALL) are being achieved with aggressive systemic chemotherapy and treatment to sanctuary sites including prophylactic cranial irradiation. However, IQ deterioration is a dreaded complication of prophylactic cranial irradiation. IQ deterioration is a late sequela. Since there is evidence--both radiobiological and clinical--to suggest that acute tissue (including tumor) response and late tissue response can be separated by hyper-fractionation, we propose a twice-a-day radiotherapy in prophylactic cranial irradiation of childhood ALL to decrease delayed toxicity. Analysis based on current radiobiological models favors such a treatment scheme. However, only a prospective clinical trial can confirm whether IQ deterioration can be prevented or decreased with hyper-fractionated radiotherapy.

Brain Neoplasms↗
PubMed1992

Dosimetry of shaped electron fields using a radial integration method.

The feasibility of an analytical approach to calculate monitor units for shaped electron fields is investigated. A radial integration method is used to calculate the dose at prescription depth from an average output factor and an average depth dose. This concept, as implemented in a commercial planning system, has been tested on various arbitrary fields, and 66 shaped electron fields clinically used for head and neck, chestwall, internal mammary, breast boost, and skin lesions. The measured and prescribed doses agreed within 3.5% or better for 71% of all clinical fields tested; for 91% the agreement was 5.5% or better. The greatest discrepancy (-7.2%) was found for a narrow, long internal mammary field. All treatments were administered on a linear accelerator with electron energies between 6 and 20 MEV.

Electrons↗
PubMed1991

Introducing a computerized record and verify system: its impact on the reduction of treatment errors.

A survey of treatment errors has been conducted over a period of several months before and after the introduction of a CMS computerized record and verify system for radiation treatments administered on a Varian CL-1800 accelerator. It was found that treatment errors could be reduced considerably. However, some errors were also caused by wrong data entry into the system. In two instances, errors were detected only through the record and verify system; they had escaped all previous chart checks and would never have been found otherwise. The impact of the computerized record and verify system is analyzed with regard to improved treatment delivery, reception by technologists, and treatment documentation.

Humans↗
PubMed1991

Equivalent total doses for different fractionation schemes, based on the linear quadratic model.

A majority of patients receiving radical radiation therapy are treated with 1.8-2.0-Gy fractions, a dose that has evolved from clinical experience. However, other fractionation schemes can be advantageous. When fractionation is altered, the total dose prescribed should lead to equivalent or higher tumor control with the same or less tissue toxicity. To facilitate the use of different fractionation schemes, the authors compiled tables for equivalent biologic doses for late toxicity in normal tissues and tumoricidal doses for epithelial tumors, for various fraction sizes. The linear quadratic model according to Fowler was used. It is shown how these tables should be modified for proliferation of tumors during the course of radiation therapy. The tables make the use of different fractionation schemes easy. They also allow adjustment of total dose if fractionation needs to be changed during the course of treatment.

Cell Survival↗
PubMed1990

Monitoring the radiation dose to a multiprogrammable pacemaker during radical radiation therapy: a case report.

Multiprogrammable pacemakers, using complimentary metaloxide semiconductor (CMOS) circuitry, may fail during radiation therapy. We report about a patient who received 6,400 cGy for unresectable carcinoma of the left lung. In supine treatment position, arms raised above the head, the pacemaker was outside the treated area by a margin of at least 1 cm, shielded by cerrobend blocking mounted on a tray. From thermoluminescent dosimeter (TLD) measurements, we estimate that the pacemaker received 620 cGy in scatter doses. Its function was monitored before, during, and after completion of radiation therapy. The pacemaker was functioning normally until the patient's death 5 months after completion of treatment. The relevant electrocardiograms (ECGs) are presented.

Aged↗
PubMed1990

Scatter dose from tangential breast irradiation to the uninvolved breast.

Thermoluminescent dosimeters (TLDs) were used to measure scatter radiation to the uninvolved breast in 30 patients who received tangential breast or chest-wall radiation with a technique in which the deep edges of the tangential fields were aligned. In most patients, measurements were made during the 1st week of radiation therapy, after port radiographs were obtained to ensure proper field position and accurate alignment of the posterior tangential field edges. Phantom measurements were made simultaneously with TLD measurements to systematically assess the scatter dose as a function of the wedging, number of fields, type of accelerator, beam energy, and bolus used in each treatment. For most patients, the scatter dose to the contralateral breast at a point on the skin 5 cm outside the edge of the medial beam was 8%-13% of the prescribed dose. However, higher doses (up to 36% of the therapeutic dose) were recorded in some patients.

Breast↗
PubMed1989

Using different sets of wedges: clinical applications, dosimetry and safety interlocks.

Each accelerator is customarily supplied with one set of wedges, typically for a maximum field width of 15 cm across the wedge slope. Clinically, however, the need arises at times for larger wedged fields. Independent jaws may require wedges which are mounted at 90 degrees from a standard set, and some half-field treatment techniques may benefit from half-field wedges. To optimize treatment conditions, it is therefore desirable to have several sets of wedges available for each treatment machine. We will present clinical examples for different sets of wedges, the results of our dosimetric measurements and will discuss the required safety interlocks.

Humans↗
PubMed1989

Impact of CT information on the treatment planning for lung tumors.

With CT information available today, the prevailing, though strong, argument for not applying lung corrections is that all clinical experience gathered so far applies to doses that were prescribed for uniform density throughout the treated volume. To ease the transition from not correcting, to the state of accounting for increased lung transmission, we have planned 10 patients: (a) in the conventional way with a wire contour obtained at simulation; target volume and critical structures were drawn in by the physician utilizing information gathered from diagnostic CT scans and X-ray films; no lung correction was applied for treatment planning. (b) For the same patients, a CT scan was obtained in treatment position and the target volume was outlined on the CT film utilizing the same information as in (a); a relative lung density of 0.3 was assigned for treatment planning. The geometric accuracy of patient outline and target volume obtained in both planning modalities is analyzed, and the intended and actually delivered tumor doses are compared when optimized treatment plans from either planning modality are selected for treatment.

Humans↗
PubMed1987

Brachytherapy implants with differently spaced Ir-192 seeds: a dosimetric study.

Brachytherapy implantations traditionally have been carried out with continuous line sources of radium. With the popularity of afterloading implantations, iridium-192 seeds in plastic ribbons have replaced radium in the United States, although continuous sources, such as iridium wires, are widely used in Europe. The authors analyzed the impact of the use of noncontinuous sources in brachytherapy implants. Computer simulations and film dosimetry of a two-planar implant were carried out. Seeds at standard spacing (1 seed/cm), nonstandard spacing (1 seed/6mm), and continuously arranged seeds were studied.

Brachytherapy↗
PubMed1985

Medulloblastoma therapy using electron beams.

The use of megavoltage photons for the spinal component of cerebrospinal axis irradiation is responsible for most of the long-term sequelae in children with medulloblastomas who undergo this procedure. The technique and advantages of using electrons for this component of the procedure are described.

Adolescent↗
PubMed1985

Medulloblastoma: are we overtreating?

Modern advances in the concept and the techniques of megavoltage radiation therapy have revolutionized the treatment of medulloblastoma. Five-year survivals of 50 to 70 percent are achieved by craniospinalaxis irradiation with a boost to the posterior fossa. However, the price paid by the long-term survivors is significant. Sequelae include growth retardation, thyroid deficiency and anomalies, marrow suppression, gonadal irradiation, IQ and psychological deterioration, immunological alterations, second malignancies, and pituitary hormonal deficiencies.The literature is reviewed in terms of these sequelae and analyzed to determine optimal therapeutic doses. Although the authors agree with the doses used to treat the posterior fossa, the current doses recommended to eradicate the microscopic disease in the rest of the neuroaxis appear excessive; a lesser dose can be as effective and may decrease the rate and severity of complications.The authors believe that there is enough evidence to initiate a randomized, multi-institutional clinical trial using 20 to 25 Gy to the neuraxis (other than the posterior fossa) in one of the arms, especially when there is no evidence of tumor outside the posterior fossa.Electron beam radiation of the spinal component can decrease the dose to some of the normal structures and prevent some of the long-term sequelae.

Cerebellar Neoplasms↗
PubMedDate not supplied

A shaping device for irregular electron fields for the Therac-20 accelerator.

A device for shaping electron fields from a Therac-20 accelerator is described. The considerable advantage of continuously variable field sizes is enhanced when the shaping device is placed on the lower trimmer bars of the shorter set of electron trimmers, which remain fully adjustable. Cerrobend blocks of 1-cm thickness are sufficient for a 5% attenuation level with 20-MeV electrons and large field sizes.

Electrons↗
PubMedDate not supplied

The neutron dose and energy spectrum outside a 20-MV accelerator treatment room.

A maze design is discussed for a Therac 20 linear accelerator (manufactured by Atomic Energy of Canada, Ltd.) which reduces the flux of neutrons at the door to permissible levels in controlled areas. The L-shaped design allows for a relatively light door at the end of the maze, consisting of 5.08-cm (2-in.) borated polyethylene and 2-mm lead. A comparison is made between the neutron dose equivalent (DE) calculated by various methods and the DE measured with a variety of portable neutron survey meters. In addition, the neutron energy spectrum outside the maze at 1 m from the door, measured with a polyethylene multisphere LiI system, is reported.

Humans↗
PubMedDate not supplied

Spinal axis irradiation with electrons: measurements of attenuation by the spinal processes.

Electrons may be used beneficially for spinal axis irradiation in medulloblastoma children to avoid some of the long-term sequelae induced by megavoltage photons. However, the attenuation by the intervening bone ought to be considered. Three-dimensional computer treatment planning with inhomogeneity correction for electron beams is not yet generally available, and alternate methods are needed to evaluate the attenuation by the complex bony structure of the spine. Here, we present our experimental data showing the alteration in the electron isodoses due to the intervening spinous processes. Film dosimetric measurements were made in the vertebral columns obtained from autopsies of a goat, a dog, and a child. Our results show that electron beam therapy for the spinal axis is a viable option.

Animals↗
PubMedDate not supplied

Irradiation of the thoracic esophagus. Prone versus supine treatment positions.

A vast majority of patients with esophageal cancer receive radiation therapy for cure or palliation. Because of the close anatomic proximity of the esophagus to the spinal cord, and unusually long fields used in the irradiation of esophageal cancer, staying within the spinal cord tolerance is crucial. The present investigation shows how this can be achieved by delivering the radiation in prone position.

Esophageal Neoplasms↗