Dosimetric verification of intensity modulated beams produced with dynamic multileaf collimation using an electronic portal imaging device

Dose distributions can often be significantly improved by modulating the two-dimensional intensity profile of the individual x-ray beams. One technique for delivering intensity modulated beams is dynamic multileaf collimation (DMLC). However, DMLC is complex and requires extensive quality assurance. In this paper a new method is presented for a pretreatment dosimetric verification of these intensity modulated beams utilizing a charge-coupled device camera based fluoroscopic electronic portal imaging device (EPID). In the absence of the patient, EPID images are acquired for all beams produced with DMLC. These images are then converted into two-dimensional dose distributions and compared with the calculated dose distributions. The calculations are performed with a pencil beam algorithm as implemented in a commercially available treatment planning system using the same absolute beam fluence profiles as used for calculation of the patient dose distribution. The method allows an overall verification of (i) the leaf trajectory calculation (including the models to incorporate collimator scatter and leaf transmission), (ii) the correct transfer of the leaf sequencing file to the treatment machine, and (iii) the mechanical and dosimetrical performance of the treatment unit. The method was tested for intensity modulated 10 and 25 MV photon beams; both model cases and real clinical cases were studied. Dose profiles measured with the EPID were also compared with ionization chamber measurements. In all cases both predictions and EPID measurements and EPID and ionization chamber measurements agreed within 2% (1 sigma). The study has demonstrated that the proposed method allows fast and accurate pretreatment verification of DMLC.     

Diffuse and localized pigmented villonodular synovitis: evaluation of treatment of 38 patients

We performed a retrospective study of 38 patients with pigmented villonodular synovitis (PVNS) to evaluate the treatment and functional results. The mean age of the patients was 32 (range 12-72) years at the time of treatment. Three types of PVNS have been identified: localized nodules in 9 patients, diffuse PVNS of the entire synovial membrane in 26, a combination of a diffuse involvement of the synovial membrane and an extra-articular presentation in 1, and extra-articular lesions in 2. The location of the lesions was knee (n = 31), hip (n = 3), ankle (n = 2), femoral triangle (n = 1), and gluteal region (n = 1). The procedures performed were surgery alone, surgery combined with radiosynovectomy and radiosynovectomy only. A follow-up was done after a mean of 4 (range 1-19) years in 34 patients. A functional evaluation according to the Musculoskeletal Tumor Society was performed in 31 patients. The mean functional evaluation score of 34 patients was 24 (range 15-30). Most of the ratings were excellent or good, in 6 cases fair, and in 2 cases poor. This study demonstrates that the functional results are good despite residual or recurrent disease; in addition, we showed that functional evaluation after treatment gives an optimal view of the impact and results of the operation.     

Cell type-specific acquired protection from crystal adherence by renal tubule cells in culture

BACKGROUND: Adherence of crystals to the surface of renal tubule epithelial cells is considered an important step in the development of nephrolithiasis. Previously, we demonstrated that functional monolayers formed by the renal tubule cell line, Madin-Darby canine kidney (MDCK), acquire protection against the adherence of calcium oxalate monohydrate crystals. We now examined whether this property is cell type specific. The susceptibility of the cells to crystal binding was further studied under different culture conditions. METHODS: Cell-type specificity and the influence of the growth substrate was tested by comparing calcium oxalate monohydrate crystal binding to LLC-PK1 cells and to two MDCK strains cultured on either permeable or impermeable supports. These cell lines are representative for the renal proximal tubule (LLC-PK1) and distal tubule/collecting duct (MDCK) segments of the nephron, in which crystals are expected to be absent and present, respectively. RESULTS: Whereas relatively large amounts of crystals adhered to subconfluent MDCK cultures, the level of crystal binding to confluent monolayers was reduced for both MDCK strains. On permeable supports, MDCK cells not only obtained a higher level of morphological differentiation, but also acquired a higher degree of protection than on impermeable surfaces. Crystals avidly adhered to LLC-PK1 cells, irrespective of their developmental stage or growth substrate used. CONCLUSIONS: These results show that the prevention of crystal binding is cell type specific and expressed only by differentiated MDCK cells. The anti-adherence properties acquired by MDCK cells may mirror a specific functional characteristic of its in situ equivalent, the renal distal tubule/collecting ducts.     

Correlation of heterogeneous blood flow and fatty acid uptake in the normal dog heart

Summary Blood flow heterogeneity in normal myocardium may be caused by heterogeneous metabolic demand. We studied, from 80 tissue samples of the left ventricle (LV) of eight anesthetised, open-chest dogs (with prior -blockade (metoprolol) in four dogs), the radioactivity of²⁰¹Thalliumchloride (²⁰¹Tl), an indicator of blood flow, and of the fatty acid¹³¹-Iodine-heptadecanoic acid (¹³¹I-HDA), an indicator of metabolic demand, 3 min after intravenous injection. Global LV uptake (in percent of injected dose ×10^–2, per g tissue; mean ±SD) was 4.94±0.71 for²⁰¹Tl and 4.48±0.58 for¹³¹I-HDA in the dogs without -blockade, and 2.08±0.26 and 1.69±0.20, respectively, in dogs with -blockade (p<0.05). Beta-blockade thus decreased the fraction of cardiac output delivered to the LV, concurrently with a decreased heart rate and arterial blood pressure (p<0.05) and, thus, global metabolic demand and fatty acid uptake. Regional radioactivities per gram were normalized for mean LV radioactivities and heterogeneity was expressed as the coefficient of variation (CV). For pooled data (n=320) in dogs without -blockade, regional²⁰¹Tl and¹³¹I-HDA radioactivities varied from a factor of 0.1 to 1.6 and 0.3 to 1.8 of mean radioactivities, with a CV of 22.9 and 19.4%, respectively, and correlated (r=0.77, p<0.005). For pooled data (n=320) in dogs with -blockade, regional²⁰¹Tl and¹³¹I-HDA radioactivities varied from a factor of 0.2 to 1.5 and 0.2 to 1.6 of mean radioactivity and CV was 23.6% and 24.8%, respectively: r=0.92 (p<0.005). The endo/epi ratio for both radioactivities exceeded unity in each dog. In normal myocardium, blood flow and fatty acid uptake are thus heterogeneous, both transmurally and circumferentially, and matched, concomitantly with coupling of global blood flow to global metabolic demand and fatty acid uptake. This supports the idea that heterogeneous myocardial O₂ supply reflects heterogeneous metabolic demand.     

Effects of an information booklet on well-being of hospital patients

Although informational booklets are being used increasingly in Dutch hospitals, little is known of their effects and the conditions for optimal use. Various aspects of the use and effects of a specially developed information booklet were investigated in two surgical wards of a general hospital. The booklet gave information about ward procedures, operative routines, narcosis, and psychosocial care possibilities. Both before and after introduction of the booklet we gathered data on the satisfaction, knowledge, and emotional state of patients on the two wards and their perception of the care climate. Patients on the control ward received just the booklet. On the experimental ward staff nurses were trained in nondirective therapeutic skills, and measurements were repeated on both wards after this intervention. In a third manipulation on the experimental ward, some of the patients had a supportive and informative talk with a trained nurse. Although patients appreciated and read the booklet better than a general hospital leaflet, the results show that the booklet and other supporting measures had no effect on the patients' perception of their well-being.     

Nucleic acid analysis of antibiotic resistance

The past 15 years the field of molecular biology and especially DNA technology has developed rapidly. This did not leave microbiology unaffected. DNA sequencing and the use of DNA probes led to new insights in the evolution and spread of antibiotic resistance genes. It became clear that resistance determinants often show partial homology even when species are not closely related. DNA probes have established their value as epidemiological tools and currently efforts are being made to introduce them into routine diagnostics.     

Gender differences in stage-adjusted bladder cancer survival

OBJECTIVES: Gender differences have been observed in the prognosis of patients with bladder cancer. It has also been suggested that these differences are caused by a worse stage distribution at diagnosis among women. The purpose of this study was to evaluate whether women with bladder cancer have a worse prognosis even after adjustment for disease stage at first presentation. METHODS: Data on patients with bladder cancer diagnosed between 1973 and 1996 and registered by one of the nine population-based Surveillance, Epidemiology, and End Results (SEER) cancer registries in the United States (n = 80,305) were obtained from the National Cancer Institute public domain SEER*Stat 2.0 package. Similar data on patients with bladder cancer diagnosed between 1987 and 1994 and registered by two population-based registries in the Netherlands (n = 1722) were obtained through the Comprehensive Cancer Centers, Amsterdam and South. Survival rates adjusted for mortality owing to other causes (ie, relative survival) were calculated for men and women within each category of the American Joint Committee on Cancer (SEER data) and TNM (Netherlands data) stage groupings.Results. In the United States, the 5-year relative survival rate of male patients with bladder cancer was calculated to be 79.5% (95% confidence interval 79.0% to 80.0%). Among women, the 5-year relative survival rate was significantly worse: 73.1% (95% confidence interval 72.2% to 74.0%). The male versus female 5-year survival rate among stage groups I, II, III, and IV was 96.5% versus 93.7%, 65.5% versus 59.6%, 58.8% versus 49.6%, and 27.1% versus 15.2%, respectively. The (sparser) data from the Netherlands were less conclusive. Women with Stage II and Stage IV disease fared worse than men but the reverse seemed to be true in Stage I disease. CONCLUSIONS: Female patients with bladder cancer have a worse prognosis than male patients. It is unlikely that the difference can explained entirely by the more frequent diagnosis of higher stages at first presentation among women.