A sandy clay till - some properties measured during consolidation and shear

Imperial Users onl

Optimization of dose distribution with multi-leaf collimator using field-in-field technique for parallel opposing tangential beams of breast cancers

3 Dimensional Conformal Radiotherapy (3D-CRT) planning software helps in displaying the 3D dose distribution at different levels in the planned target volume (PTV). Physical or dynamic wedges are commonly applied to obtain homogeneous dose distribution in the PTV. Despite all these planning efforts, there are about 10% increased dose hot spots encountered in final plans. To overcome the effect of formation of hot spots, a manual forward planning method has been used. In this method, two more beams with multi-leaf collimator (MLC) of different weights are added in addition to medial and lateral wedged tangent beams. Fifteen patient treatment plans were taken up to check and compare the validity of using additional MLC fields to achieve better homogeneity in dose distributions. The resultant dose distributions with and without presence of MLC were compared objectively. The dose volume histogram (DVH) of each plan for the PTV was evaluated. The 3D dose distributions and homogeneity index (HI) values were compared. The 3D dose maximum values were reduced by 4% to 7%, and hot spots assumed point size. Optimizations of 3D-CRT plans with MLC fields improved the homogeneity and conformability of dose distribution in the PTV. This paper outlines a method of obtaining optimal 3D dose distribution within the PTV in the 3D-CRT planning of breast cases

The pattern of hepatobiliary complications among Egyptian sickle cell disease children

Background: Hepatobiliary complications are frequent among sickle cell disease patients. Sickle cell disease has been extensively studied. However, data about hepatobiliary abnormalities among the pediatric age group are limited. Objective: This study aimed at describing the pattern of hepatobiliary complications among sickle cell disease patients as detected clinically, by laboratory testing and by abdominal ultrasonography. Methods: Seventy sickle cell disease patients, aged 2–8 years, of both SS and Sβ types were enrolled in this cross-sectional study. Thorough history taking, full clinical examination, hematological and biochemical parameters assessment and abdominal ultrasonographic studies were performed to all patients. Result: The median age of the patients was 12.5 years (mean: 11.81 ± 5.1). Hepatomegaly was detected ultrasonographically in 24 patients (34.3%) and was more encountered among patients with increasing age (P = 0.003), patients with HbSβ type (P = 0.002) and high serum ferritin levels (P = 0.047). Gallbladder diseases were encountered in 19 patients (27.1%), and manifested as isolated stones in (7.1%), isolated mud in (5.7%), stones with mud in 2 patients (2.9%), and surgically removed stones in (11.4%). Cholecystectomy was done in 8 patients (11.4%). Gallbladder disease was more frequent among patients with older age (P = 0.041), more severe sickle cell disease attacks (P = 0.035), and longer duration of blood transfusion therapy (P = 0.041). Other hepatobiliary complications were chronic hepatitis C (12.9%), benign hyperbilirubinemia (1.4%), intrahepatic cholestasis (1.4%), hepatic sequestration(1.4%), hepatic crisis (1.4%), and liver cirrhosis (1.4%). Conclusion: Hepatobiliary complications are frequent among sickle cell disease children especially gallbladder diseases. Repeated clinical and ultrasound screening is needed for early detection and treatment of these complications

Verification of setup errors in external beam radiation therapy using electronic portal imaging

The objective of this study was to conduct an audit on QA aspects of treatment delivery by the verification of the treatment fields′ position on different days to document the efficiency of immobilization methods and reproducibility of treatment. A retrospective study was carried out on 60 patients, each 20 treated for head and neck, breast, and pelvic sites; and a total of 506 images obtained by electronic portal imaging device (EPID) were analyzed. The portal images acquired using the EPID systems attached to the Varian linear accelerators were superimposed on the reference images. The anatomy matching software (Varian portal Vision. 6.0) was used, and the displacements in two dimensions and rotation were noted for each treated field to study the patient setup errors. The percentages of mean deviations more than 3 mm in ′lateral (X) and longitudinal (Y)′ directions were 17.5%, 11.25%, and 7.5% for breast, pelvis, and head and neck cases respectively. In all cases, the percentage of mean deviation with more than 5 mm error was 0.83%. The maximum average mean deviation in all the cases was 1.87. The average mean SD along X and Y directions in all the cases was less than 2.65. The results revealed that the ranges of setup errors are site specific and immobilization methods improve reproducibility. The observed variations were well within the limits. The study confirmed the accuracy and quality of treatments delivered to the patients

Clinical implementation of dynamic intensity-modulated radiotherapy: Dosimetric aspects and initial experience

This paper describes the initial experience of quality assurance (QA) tests performed on the millennium multi-leaf collimator (mMLC) for clinical implementation of intensity-modulated radiotherapy (IMRT) using sliding window technique. The various QA tests verified the mechanical and dosimetric stability of the mMLC of linear accelerator when operated in dynamic mode (dMLC). The mechanical QA tests also verified the positional accuracy and kinetic properties of the dMLC. The stability of dMLC was analyzed qualitatively and quantitatively using radiographic film and Omnipro IMRT software. The output stability, variation in output for different sweeping gap widths, and dosimetric leaf separation were measured. Dose delivery with IMRT was verified against the dose computed by the treatment planning system (TPS). Monitor units (MUs) calculated by the planning system for the IMRT were cross-checked with independent commercial dose management software. Visual inspection and qualitative analysis showed that the leaf positioning accuracy was well within the acceptable limits. Dosimetric QA tests confirmed the dosimetric stability of the mMLC in dynamic mode. The verification of MUs using commercial software confirmed the reliability of the IMRT planning system for dose computation. The dosimetric measurements validated the fractional dose delivery