Biomedical subjects

J W Rieke

Publications and source records attributed to J W Rieke.

9 recordsLinked to original sources

PubMed2000

An isocentrically mounted stand for total body irradiation.

The purpose of this study was to construct a stand to support a patient for total body photon irradiation and to expedite the set-up and treatment by rotating the stand. As in other isocentric treatments, the midline dose is impacted less by source-to-skin distance variations. The method of immobilizing the patient is described. A 10 mm lucite plate is supported in front of the patient to increase skin dose. A matrix of holes in this plate serves to index the location of blocks used to shield the lungs. The dosimetry of the set-up is described, as is the production of tissue deficit compensators. The results of phantom studies and in vivo thermoluminescent dosimetry measurements are presented.

Equipment Design↗

PubMed1995

Oral pilocarpine for radiation-induced xerostomia: integrated efficacy and safety results from two prospective randomized clinical trials.

PURPOSE: Pilocarpine hydrochloride administered in either a fixed-dose or in a dose-titration protocol three times a day for 12 weeks was evaluated for its ability to relieve symptoms of postradiation xerostomia and to improve saliva production. The studies were randomized, double-blind, placebo-controlled, multicenter clinical trials. A total of 369 patients who had received at least 40 Gy of radiation to the head and neck with clinically significant xerostomia were enrolled in the two studies. In the dose-titration study, 162 patients were enrolled and they received a thrice daily regimen of 2.5 mg tablets for first 4 weeks, 5.0 mg tablets for the second 4 weeks, and 10.0 mg tablets for last 4 weeks of a 12-week study. Patients in the titration study were allowed to down titrate following at least one dose escalation to alleviate bothersome side effects, if any. In the fixed dose study, 207 patients received either placebo, 5.0 mg, or 10.0 mg tablets t.i.d. for 12 weeks. METHODS AND MATERIALS: Patients were evaluated for symptomatic relief by responding to questionnaires using visual analog scales and categorical questions; and, for saliva production by sialometry. Questionnaires measured relief of intraoral dryness, improvement in overall condition (global response), oral discomfort, difficulty in speaking, chewing and swallowing, denture wearing, and usage of artificial saliva. Evaluations were conducted at baseline, and weeks 4, 8, and 12. RESULTS: There were statistically significant improvements in salivary flow in pilocarpine treatment groups vs. placebo. There was a significant improvement in the overall "global" condition of xerostomia associated with the use of pilocarpine in both studies. In the fixed-dose study, there were significant improvements in oral dryness, mouth comfort, ability to speak, and reduction in the use of oral comfort agents. The dose-titration study showed improvements in dryness that approached significance (p = 0.057) and a decreased use of oral comfort agents (p = 0.045). All pilocarpine dosages (2.5, 5.0, and 10.0 mg three times a day) were judged to be safe. Adverse experiences were those expected for a cholinergic agonist, with the most common being mild to moderate sweating. The incidence of these events increased by dose. CONCLUSION: It is concluded that in these studies pilocarpine produced clinically significant benefits with acceptable side effects and risks for the treatment of symptomatic postradiation xerostomia. The incidence of most adverse events increased with dose. Best results may require continuous treatment for more than 8 weeks with doses greater than 2.5 mg three times a day. A 5.0 mg thrice daily regimen produced the best clinical results when both efficacy and side effects were taken into consideration. There may be some patients who would experience some additional benefit by increasing the dose to 10 mg thrice daily.

Administration, Oral↗

PubMed1995

The incorporation of partial shielding of the spinal cord in a tissue deficit compensator in radiotherapy of the thorax.

A method to determine the shape of a patient by placing radiopaque wires and chains on the skin and taking two isocentric X-ray films is described. The wire locations are reconstructed by X-ray stereo photogrammetry, and a beam's eye view of the wire frame structure can be obtained with reference to the original setup of the "stereo-pair" films. An algorithm for paving between the wires with triangular plates is described which allows the calculation of the tissue deficit distance and compensator thickness. The depth and distance to points on the spinal cord are calculated, and the dose rate is calculated using a standard irregular field computation program. The limit for spinal cord tolerance is specified in terms of the maximum daily dose based on an equivalent dose formula. The additional thickness of compensator, required for the posterior field compensator to satisfy the tolerance limit, is calculated. The technique readily accommodates the kyphotic and scoliotic spine and has been in routine clinical use for seven years.

Algorithms↗

PubMed1995

An estimate of the margin required when defining blocks around the prostate.

The portal films of 54 consecutive patients treated for primary prostate cancer have been compared to the simulation films. The systematic and random uncertainty in the set-up, defined by the couch movement required to move the patient to the simulated position, was determined to be 1.6 mm UP (SD 3.3 mm), 0.3 mm RT (SD 2.6 mm) and 1.3 mm IN (SD 2.4 mm). The area of fields defined on simulation films was compared with that on portal films to determine the error in block production which was -0.7 mm (SD = 0.9 mm). Five sources of uncertainty in the radiotherapy have been identified, three occur before and two during the course of treatment. A method for combining these uncertainties is proposed and used on the data obtained in this study. This provides estimates of the margin required when drawing blocks so that the minimum dose to the target is 95% of the prescription in 95% of treatments. The block margins are not uniform and range from 21 mm, when drawing the block outline to the posterior on a lateral film, to 13 m when drawing laterally on an anterior film.

Humans↗

PubMed1993

A multicenter, randomized, double-blind, placebo-controlled, dose-titration study of oral pilocarpine for treatment of radiation-induced xerostomia in head and neck cancer patients.

PURPOSE: To determine the efficacy and safety of pilocarpine hydrochloride for symptomatic relief of postradiation xerostomia symptoms and for saliva production in patients with head and neck cancer. PATIENTS AND METHODS: One hundred sixty-two head and neck cancer patients who had received at least 40 Gy of radiation (117 patients had received > 60 Gy) with clinically significant xerostomia were enrolled onto a randomized, double-blind, placebo-controlled, multi-center clinical investigation. Patients received 2.5-mg tablets for the first 4 weeks, 5.0-mg tablets for the second 4 weeks, and 10.0-mg tablets for the last 4 weeks of the 12-week study. Patients were allowed to titrate pilocarpine or placebo for improvement in symptoms or to reduce side effects. Patients were evaluated for symptomatic relief by questionnaires and visual analog scales (VAS), and for saliva production by sialometry. RESULTS: Pilocarpine produced a significant improvement (P = .035) in overall global assessments compared with placebo. There was a statistically significant (P = .020) decreased use of oral comfort agents such as artificial saliva, hard candy, and water. Values for symptomatic improvement in dryness approached significance (P = .057). There were statistically significant postdose improvements in whole and parotid salivary flow in pilocarpine treatment groups versus placebo. All pilocarpine dosages tested were judged to be safe. Adverse experiences were primarily sweating, rhinitis, headache, nausea, and urinary frequency, with the most common side effect being mild to moderate sweating. There were no serious drug-related adverse experiences in any of the pilocarpine treatment groups. CONCLUSION: It is concluded that pilocarpine produces clinically significant benefits for the symptomatic treatment of postradiation xerostomia. Best results were obtained with continuous treatment for 8 to 12 weeks with doses greater than 2.5 mg three times per day.

Administration, Oral↗

PubMed1993

A frameless method for stereotactic radiotherapy.

A frameless method for stereotactic multiple arc radiotherapy (SMART) is described. Three short gold wires are implanted in the scalp approximately 100 mm apart. These are localized in a computed tomographic or angiographic study along with the target. Subsequently the gold markers are localized on beam films and the target position calculated using a computer program ISOLOC. This program provides the couch movements required to move the target to the isocentre and a micropositioner attached to the couch is used to make the adjustment. Beam films are repeated until the movements required are less than 1 mm in any direction. It is shown that the simple procedures of implanting the markers subcutaneously do not provide a stable reference system in about 25% of patients and the markers are now screwed into the cranium. The precision of the method is evaluated by phantom studies and measurements taken during several hundred treatments.

Brain Diseases↗

PubMed1989

Hypercalcemia and vitamin D metabolism in Hodgkin's disease. Is there an underlying immunoregulatory relationship?

Hypercalcemia is not common in Hodgkin's disease, but in reported cases is often unassociated with bone involvement. A case is presented demonstrating a mechanism involving elevated levels of 1,25-dihydroxy vitamin D3 (calcitriol). Similar cases in the literature are reviewed. Data implicating calcitriol as a hematolymphoid regulatory hormone are discussed as they may relate to lymphomas, leukemias, and paraneoplastic lymphocyte and monocyte/macrophage activity.

Adolescent↗

PubMed1988

Successful management of malignant pericardial effusion in metastatic squamous cell carcinoma of the uterine cervix.

Malignant pericardial effusion secondary to pericardial metastases from gynecological malignancies represents an infrequent but potentially life threatening problem. A patient with recurrent squamous cell carcinoma of the cervix causing symptomatic pericardial effusion is presented, and the incidence, mechanism, pathophysiology, treatment, and outcomes of malignant pericardial effusion in patients with gynecologic malignancies are reviewed. This case represents only the fourth reported patient with metastatic carcinoma of the cervix in whom the diagnosis of malignant pericardial effusion was made antemortem, and is the longest survivor of treatment. Gratifying results, in terms of improved quality and length of survival, can be obtained in what is often perceived as a preterminal complication. Recommendations for management are presented, stressing radiation therapy and other local measures following initial pericardiocentesis.

Carcinoma, Squamous Cell↗

PubMed1988

A new catheter system with remote tip guidance for endobronchial brachytherapy.

Endobronchial brachytherapy is being used with increased frequency in the treatment of recurrent neoplastic obstruction of the major airways, alone or in combination with Nd-YAG laser ablation of the occluding tumor mass. Currently available catheter systems are not reliable with respect to accurate and simple bronchoscopic guidance during placement. Flexibility, wall strength and radiation transmission characteristics are not optimized. We describe a system that meets these goals which has been designed and tested in our department. It is composed of an external handle, deflecting guidewire, and catheter specially modified for endobronchial brachytherapy, with a tip that can be maneuvered in any direction with one hand from outside the patient. Major advantages of the system are ease of concurrent bronchoscopy and catheter guidance, good dosimetric characteristics of the catheter, reasonable cost, and ready availability for adaptation to various techniques of endobronchial brachytherapy.

Brachytherapy↗