Biomedical subjects

J E Marks

Publications and source records attributed to J E Marks.

93 records · Page 6Linked to original sources

PubMedDate not supplied

The dosimetry of a single "hockey stick" portal for treatment of tumors of the cranio-spinal axis.

Conventional treatment of tumors of the cranio-spinal axis portal usually involves multiple-field, moving junction treatments to avoid overlapping fields over the spinal cord. To avoid these problems, we irradiate the cranio-spinal axis using a single "hockey stick" portal and the 25-MV x-ray beam from a Varian Clinac-35 linear accelerator. Patients are positioned prone on the floor 229 cm from the radiation source and the collimators are rotated 45 degrees so the maximum diagonal dimension of the field 116 cm at 229 cm is coincident with the cranio-spinal axis. The head is alternately rotated to treat the right-hand side one day and the left-hand side the next day. Thermoluminescent dosimetry in an anatomical phantom reveals that, relative to the 100% dose delivered at 4-cm depth on the central axis of the blocked field, the midline posterior fossa dose is about 100%, with a maximum dose of about 105% to the extreme posterior portion of the skull. The midline neck dose is about 95% and the dose to the inferior portion of the spinal cord is about 105%. The doses to other critical organs are also presented.

Head and Neck Neoplasms↗

PubMedDate not supplied

The use of diafiltration for the measurement of dialysable ligand binding to macromolecules: an examination of the theoretical parameters using concanavalin A in an Amicon cell.

The technique of diafiltration as a means of determining the characteristics of small ligand binding by proteins has been evaluated by measuring the binding of 45Ca to concanavalin A. Deposition of protein on the diafiltration membrane was found to be an important source of error but which could be eliminated by presaturation of the membrane with polylysine. The association constant for concanavalin A and calcium was 1.8 x 10(4) M-1, with a value of n = 2.2 atoms of calcium being bound per dimer of concanavalin A. The concentration of protein relative to the dissociation constant is also an important variable, and it was found that the method of diafiltration is only useful when protein concentrations greater than the value of the dissociation constant are used.

Calcium↗

PubMedDate not supplied

Preoperative irradiation and surgery for carcinoma of the base of the tongue.

From 1960 through 1978, 101 patients with histologically proven epidermoid carcinoma of the base of the tongue were treated with preoperative irradiation and surgery at Washington University School of Medicine. Local and regional control at 3 years was achieved in 65% of the patients, and at 5 years in 57%. Sixteen percent of patients who suffered local or regional failure were salvaged by further surgery. Distant metastases developed in approximately 18% of patients and second malignancies developed in 20%. It appears that the combination of preoperative irradiation plus surgery provides substantial local control rates and survival for patients with base of tongue cancer in both early and moderately advanced stages.

Adult↗