Effect of dose reduction on image registration and image quality for cone-beam CT in radiotherapy.

INTRODUCTION: The additional radiation exposure applied to patients undergoing cone-beam computed tomography (CBCT) for image registration in radiation therapy is of great concern. Since a decrease in CBCT dose is linked to a degradation of image quality, the consequences of dose reduction on the registration process have to be investigated. MATERIAL AND METHODS: This paper examines image quality and registration of low-contrast structures on an Elekta XVI for the two treatment areas prostate and chest while gradually decreasing the mAs per frame and the number of projections per CBCT to achieve dose reduction. RESULTS: Ideal results for image quality were obtained for 1.6 mAs/frame and 377 projections in prostate scans and 0.63 mAs/frame and 440 projections in chest images. Lower as well as higher total mAs lead to a decrease in image quality. In spite of poor image quality, registration can be successfully performed even for lowest possible settings. CONCLUSION: The results for registration allow an extensive dose reduction in both treatment areas. Very low mAs, however, do not qualify for clinical use because subjective judgment of the registration process is impossible. Compared to default presets the use of settings for acceptable image quality already permit a decrease in exposure of about 40 % (29.0 to 16.7 mGy) in prostate scans and 60 % (18.3 to 7.7 mGy) in chest scans.

[Costs-proceeds calculation for radiotherapy; comment]. / Kosten-Erlös-Rechnung für die Strahlentherapie.

BACKGROUND: The Health Care Structure Bill (Gesundheitsstrukturgesetz) and the Federal Health Care Tariff Regulation (Bundespflegesatzverordnung) pose new challenges for the chief physician in charge, which he has to face on account of hospital management control with department-specific internal budgeting of services, expenditure and remittance. In view of the impending establishment of care-related lump sums (Fallpauschalen) and special allowances for radiation therapy (Sonderentgelte) as well as the introduction of an appropriate internal budget plan, we resolved to draw up the service-cost ratio for 11 tumor entities, implementing calculation based on process evaluation, and to match this calculation to the actual proceeds from outpatient treatment covered either by general health insurance or private care insurance. MATERIAL AND METHODS: The following 11 tumors were included in the analysis: Glioblastoma multiforme, squamous cell carcinoma of the head and neck, lung cancer, oesophageal cancer, breast cancer, rectal and prostate cancer, cancer of the anal canal and the uterine cervix, Hodgkin's disease and bone metastases. For the description of the services rendered and for the calculation of actual cost, the complex treatment regime was divided into the following steps: administration, medical radiation planning, radiation planning by physicist, workmanship, radiotherapy treatment and medical service. The calculation of costs was made either in- or excluding the cost of teatment facilities and basic investment. The proceeds were calculated according to the regulations of the EBM (dated 1. 10. 1994) for general health insurance patients (median point value 9.35 DPF) and the GOA (dated 1. 7. 1988) for private patients (point value 11 DPF). RESULTS: 1. Calculation by EBM standards: Excluding the cost of facilities and basic investment, there is a profit margin for the following tumor entities amounting to +1.6% (103.18 DM) for ENT tumors, +9.2% (671.90 DM) for carcinoma of the anal canal and +35.8% (1637.84 DM) for bone metastases. All other tumor entities cannot be treated cost-effectively. With the exception of glioblastoma, median loss comes to -20% (-14% to -27.4%, i.e. -809.48 to -1812.84 DM). Including in the calculation the cost of the facilities and investment, only bone metastases can be treated with a profit margin. For all other tumors, the mean loss amounts to -33% (-14.1% to -44.7%) or else -1308.26 to -4550.51 DM. 2. Calculation by GOA standards: Comparing cost and actual proceeds, there is a loss for all tumor entities. Excluding the cost of treatment facilities and investment, median loss amounts to -44% (-33.3% to -53.5%, or -1752.64 DM to -3488.18 DM), including both, mean loss comes to -56% (-47.8% to -53.3% or -3156.33 DM to -6332.43 DM). 3. Calculation of comprehensive cost and of the proceeds: For our own department, considering the cost-proceeds ratio for 1994, we ran up a deficit of 673,767.10 DM for outpatient care. This deficit can mainly be traced back to non-operational hours of the linear accelerator due to machine impairment, maintenance and dosimetric measurements by the physicists, leading to the loss of 53 work-days (14 hours each) amounting to 498,771.34 DM plus general costs of 271,000 DM added to the bill by hospital administration. CONCLUSIONS: As to the reviewed tumor entities, modern standard radiotherapy cannot be administrated cost-effectively. A considerable degree of under-funding is especially evident with the inclusion of cost of investment and of the facilities. The cost-proceeds ratio is most unsatisfactory as regards GOA calculation, which is obsolete as far as service description and service payment is concerned. As it in no way measures up to the required standard of modern radiotherapy, reform is therefore urgently needed.

[Ultrasound diagnosis of birth trauma lesion of the cervical spine]. / Sonographische Diagnostik einer geburtstrumatischen Halsmarkläsion.

Ultrasonographic imaging in the newborn via a posterior approach allows the visualization of the craniocervical junction. We describe a case presenting with clinical signs of a spinal cord injury after delivery by forceps extraction. The sonographic examination demonstrated an increased cervical cord echogenicity during the first days of life, and a decrease of cord size at the craniocervical junction after 3 weeks. MRI confirmed these findings. Sonography is useful in showing severe spinal cord injury with minimal handling of these severely traumatized neonates.

Reactions of formate and ethanol radicals with bovine serum albumin studied by electrophoresis.

Radiation-induced reactions of formate and ethanol radicals with bovine serum albumin were studied by electrophoresis. The reaction products were separated as reduced and unreduced SDS-protein-complexes on polyacrylamide gel. Quantitative evaluation of the densitometric measurements gives information about the reaction mechanisms. Initially formate radicals react rapidly and very selectively with the disulphide groups which then form partly intermolecular S-S-bonds. This formation of reducible aggregates causes a massive loss of serum albumin. With increasing dose unreducible aggregates are formed. Formate radicals show a high efficiency in both degradation processes, which are not caused by ethanol radicals. Formate radicals are much more effective in degrading serum albumin than ethanol radicals. Both radicals show a third degradation process which has low G-values and is presumably caused by H-abstraction.

The effects of thyroid hormones on myelination in the developing rat brain.

Rats radiothyroidectomized 1 day after birth received daily subcutaneous injections of 1 microgram/10 g body weight of thyroxine (T4) or an equimolar amount of triiodothyroacetic acid (T3AC) from day 6 through day 25. The number of myelinated axons, myelinated axon area, and area of the myelin sheath in the corpus striatum were investigated. Hypothyroid neonates demonstrated a normal number of myelinated axons with a decrease in the area of these axons. T4 treatment resulted in an increased number of smaller axons while T3AC treatment produced fewer but larger axons than the T4 treatment. The myelin area changed as the axon area changed with the myelin thickness remaining constant in all groups.