Limitations of a pencil beam approach to photon dose calculations in lung tissue.

A common limitation in treatment planning systems for photon dose calculation is to ignore the impact on electron transport and photon scatter from patient heterogeneities. The heterogeneity correlation is often based on scaling operations along beam rays as for the method according to Batho or the more novel approach of 1D convolutions along beam paths applied in pencil-beam-based systems. The effects of the limitation have been studied in a mediastinum geometry for a wide range of beam qualities by comparing the results from a pencil-beam-based treatment planning system with the results from Monte Carlo calculations.

Heat generation and heat protection in methylmethacrylate cementation of vertebral bodies. A cadaver study evaluating different clinical possibilities of dural protection from heat during cement curing.

For metastatic disease of the spine, anterior operations on the vertebral bodies often include methylmethacrylate cementation. The cement curing process may produce high temperatures in the surroundings, as demonstrated in joint replacement surgery, and there is a risk of thermal injury to the spinal nerves. In cadavers, we studied the heat arising during curing of cement on the dural sac, and the temperature of the cement surface was measured when the vertebral body was reconstructed using acrylic cement in the same way as in tumor surgery.

The dosimetric verification of a pencil beam based treatment planning system.

A new three-dimensional treatment planning system (TPS) based on convolution/superposition algorithms (TMS-Radix from HELAX AB, Uppsala, Sweden) was recently installed at the University Hospital in Lund. The purpose of the present study was to design a quality assurance and acceptance testing programme to meet the specific characteristics of this convolution model. The model is based on parametrization of a non-measurable quantity-the polyenergetic pencil beam.

Anomalous lumbosacral articulations and low-back pain. Evaluation and treatment.

Eleven patients ranging from 13 to 76 years in age with low-back pain and asymmetric sacro-transverse joints were studied. Preoperatively, scintimetry was performed in eight of the patients, in all cases with normal results. Ten of the 11 patients had their sacrotransverse joint anesthesized in fluoroscopy.

Transient synovitis of the hip in the child: increased levels of proteoglycan fragments in joint fluid.

The levels of proteoglycan antigen were measured in joint aspirates from the hip of children with transient synovitis, septic arthritis, Legg-Calvé-Perthes' disease and congenital and traumatic dislocation. Significantly increased levels were found in children with transient synovitis and septic arthritis as compared with other conditions. We propose that the proteoglycan antigens in the joint fluid were released from the articular cartilage in a partially degraded form as a result of an increased rate of proteolytic degradation.