Search Results

41 - 50 of 189 items :

  • "Measurement" x
  • Haematology, Oncology x
Clear All
Dosimetric verification of compensated beams using radiographic film

Dosimetric verification of compensated beams using radiographic film

Introduction. External photon beam modulation using compensators in order to achieve a desired dose distribution when brachytherapy treatment is followed by external beam radiation is a well-established technique. A compensator modulates the central part of the beam, and the dose beneath the thickest part of the compensator is delivered mostly by scattered, low energy photons. A two-dimensional detector with a good spatial resolution is needed for the verification of those beams. In this work, the influence of different types of detectors on the measured modulated dose distributions was examined.

Materials and methods. Dosimetric verification was performed using X-Omat V, Eastman Kodak radiographic films at different depths in a solid water phantom. The film measurements were compared with those made by ionization chambers. Photon beams were also modelled using EGSnrc Monte Carlo algorithm to explain the measured results.

Results. Monte Carlo calculated over-response of the film under the thickest part of the compensator was over 15%, which was confirmed by measurements. The magnitude of over-response could be associated with changes in the spectra of photon energy in the beam.

Conclusions. The radiographic film can be used for the dosimetry of compensated high energy photon beams, with limitations in volumes where photon spectra are hardly degraded.

Open access
A comparison of the quality assurance of four dosimetric tools for intensity modulated radiation therapy

Abstract

Background. This study was designed to compare the quality assurance (QA) results of four dosimetric tools used for intensity modulated radiation therapy (IMRT) and to suggest universal criteria for the passing rate in QA, irrespective of the dosimetric tool used.

Materials and methods. Thirty fields of IMRT plans from five patients were selected, followed by irradiation onto radiochromic film, a diode array (Mapcheck), an ion chamber array (MatriXX) and an electronic portal imaging device (EPID) for patient-specific QA. The measured doses from the four dosimetric tools were compared with the dose calculated by the treatment planning system. The passing rates of the four dosimetric tools were calculated using the gamma index method, using as criteria a dose difference of 3% and a distance-to-agreement of 3 mm.

Results. The QA results based on Mapcheck, MatriXX and EPID showed good agreement, with average passing rates of 99.61%, 99.04% and 99.29%, respectively. However, the average passing rate based on film measurement was significantly lower, 95.88%. The average uncertainty (1 standard deviation) of passing rates for 6 intensity modulated fields was around 0.31 for film measurement, larger than those of the other three dosimetric tools.

Conclusions. QA results and consistencies depend on the choice of dosimetric tool. Universal passing rates should depend on the normalization or inter-comparisons of dosimetric tools if more than one dosimetric tool is used for patient specific QA.

Open access
The effect of breast shielding during lumbar spine radiography

Abstract

Background. The aim of the study was to determine the influence of lead shielding on the dose to female breasts in conventional x-ray lumbar spine imaging. The correlation between the body mass index and the dose received by the breast was also investigated.

Materials and methods. Breast surface dose was measured by thermoluminescent dosimeters (TLD). In the first phase measurements of breast dose with and without shielding from lumbar spine imaging in two projections were conducted on an anthropomorphic phantom. In the second stage measurements were performed on 100 female patients, randomly divided into two groups of 50, with breast shielding only used in one group.

Results. On average, breast exposure dose in lumbar spine imaging in both projections (anteroposterior (AP) and lateral) was found reduced by approximately 80% (p < 0,001) when shielding with 0.5 mm lead equivalent was used (from 0.45±0.25 mGy to 0.09±0.07 mGy on the right and from 0.26±0.14 mGy to 0.06±0.04 mGy on the left breast). No correlation between the body mass index (BMI) and the breast surface radiation dose was observed.

Conclusions. Although during the lumbar spine imaging breasts receive low-dose exposure even when shielding is not used, the dose can be reduced up to 80% by breast shielding with no influence on the image quality.

Open access
Effect of ionizing radiation on human skeletal muscle precursor cells

Abstract

Background. Long term effects of different doses of ionizing radiation on human skeletal muscle myoblast proliferation, cytokine signalling and stress response capacity were studied in primary cell cultures.

Materials and methods. Human skeletal muscle myoblasts obtained from muscle biopsies were cultured and irradiated with a Darpac 2000 X-ray unit at doses of 4, 6 and 8 Gy. Acute effects of radiation were studied by interleukin - 6 (IL-6) release and stress response detected by the heat shock protein (HSP) level, while long term effects were followed by proliferation capacity and cell death.

Results. Compared with non-irradiated control and cells treated with inhibitor of cell proliferation Ara C, myoblast proliferation decreased 72 h post-irradiation, this effect was more pronounced with increasing doses. Post-irradiation myoblast survival determined by measurement of released LDH enzyme activity revealed increased activity after exposure to irradiation. The acute response of myoblasts to lower doses of irradiation (4 and 6 Gy) was decreased secretion of constitutive IL-6. Higher doses of irradiation triggered a stress response in myoblasts, determined by increased levels of stress markers (HSPs 27 and 70).

Conclusions. Our results show that myoblasts are sensitive to irradiation in terms of their proliferation capacity and capacity to secret IL-6. Since myoblast proliferation and differentiation are a key stage in muscle regeneration, this effect of irradiation needs to be taken in account, particularly in certain clinical conditions.

Open access
The clinical value of combined use of MR imaging and multi-slice spiral CT in limb salvage surgery for orthopaedic oncology patients: initial experience in nine patients

The clinical value of combined use of MR imaging and multi-slice spiral CT in limb salvage surgery for orthopaedic oncology patients: initial experience in nine patients

Background. The purpose of this prospective study was to evaluate the value of the combined use of MR imaging and multi-slice spiral CT for limb salvage surgery in orthopaedic oncology patients.

Patients and methods. Nine consecutive patients with lower/upper limb malignant bone tumours (7 osteosarcomas and 2 chondrosarcomas) were treated with limb-salvaging procedures. Preoperative planning including determination of the osteotomy plane and diameters of the prosthesis was performed basing on the preoperative CT and MR images. The histopathology was performed as golden diagnostic criteria to evaluate the accuracy of CT and MR-based determination for tumour's boundary.

Results. The tumour extension measured on MRI was consistent with the actual extension (P>0.05, paired Student's t test), while the extension measured on CT imaging was less than the actual extension. The length, offset and alignment of the affected limb were reconstructed accurately after the operation. An excellent functional outcome was achieved in all patients.

Conclusions. In the present study, MRI was found to be superior to CT for determining the tumour extension, combined use of MRI and CT measurement provided high precision for the fit of the prosthesis and excellent functional results.

Open access
Electrogene therapy with interleukin-12 in canine mast cell tumors

Electrogene therapy with interleukin-12 in canine mast cell tumors

Background. Mast cell tumors (MCT) are the most common malignant cutaneous tumors in dogs with extremely variable biological behaviour. Different treatment approaches can be used in canine cutaneous MCT, with surgical excision being the treatment of choice. In this study, electrogene therapy (EGT) as a new therapeutic approach to canine MCTs, was established.

Materials and methods. Eight dogs with a total of eleven cutaneous MCTs were treated with intratumoral EGT using DNA plasmid encoding human interleukin-12 (IL-12). The local response to the therapy was evaluated by repeated measurements of tumor size and histological examination of treated tumors. A possible systemic response was assessed by determination of IL-12 and interferon- γ (IFN-γ) in patients' sera. The occurence of side effects was monitored with weekly clinical examinations of treated animals and by performing basic bloodwork, consisting of the complete bloodcount and determination of selected biochemistry parameters.

Results. Intratumoral EGT with IL-12 elicits significant reduction of treated tumors' size, ranging from 13% to 83% (median 50%) of the initial tumor volume. Additionally, a change in the histological structure of treated nodules was seen. There was a reduction in number of malignant mast cells and inflammatory cell infiltration of treated tumors. Systemic release of IL-12 in four patients was detected, without any noticeable local or systemic side effects.

Conclusions. These data suggest that intratumoral EGT with plasmid encoding IL-12 may be useful in the treatment of canine MCTs, exerting a local antitumor effect.

Open access
Evaluation of shRNA-mediated gene silencing by electroporation in LPB fibrosarcoma cells

Evaluation of shRNA-mediated gene silencing by electroporation in LPB fibrosarcoma cells

Background. Silencing oncogenes or other genes that contribute to tumor malignancy and progression offers a promising approach to treating cancer. Specific and efficient silencing of gene expression can be achieved by RNA interference (RNAi) technology using small interfering RNA (siRNA) or short hairpin RNA (shRNA). However, a major challenge in RNAi technology is effective delivery of interfering molecules into target cells. The aim of our study was to evaluate electroporation as a perspective method for efficient in vitro transfection of LPB fibrosarcoma cells with plasmid DNA expressing shRNA.

Methods. Induction of shRNA-mediated gene silencing by electroporation was determined by fluorescence microscopy, flow cytometry and western blot analysis. The effect of electroporation conditions on cell survival and proliferation was determined by clonogenic assay.

Results and conclusions. Our results demonstrated that electroporation is a feasible and effective method for delivery of plasmid DNA expressing shRNA into cancer cells in vitro. Electrotransfection of murine LPB fibrosarcoma cells, continuously expressing green fluorescence protein - GFP (LPBGFP), with plasmid DNA encoding shRNA-GFP, reduced GFP expression, which was determined on the protein level, as well as by measurement of GFP fluorescence intensity. A pronounced reduction in GFP expression level was detected from the second to the fifth day after treatment. Moreover, the method is easy to perform and showed low cell damaging effects, which are the most important and preferential factors for further in vivo studies.

Open access
A neutron track etch detector for electron linear accelerators in radiotherapy

positioning methods 203 in prostate image guided radiation therapy (IGRT). Radiol Oncol 2009; 43 : 203-12. Ongaro C, Zanini A, Nastasi U, Rodenas J, Ottaviano G, Manfredotti C. Analysis of photoneutron spectra produced in medical accelerators. Phys Med Biol 2005; 45 : 55-61. Králík M, Turek K. Characterisation of neutron fields around high-energy x-ray radiotherapy. Radiat Prot Dosimetry 2004; 110 : 503-7. Rivera JC, Falcão RC, deAlmeida CE. The measurement of photoneutron dose in the

Open access
Nutrition of patients with severe neurologic impairment

Abstract

Background

Commercial enteral formulas are generally recommended for gastrostomy feeding in patients with severe neurologic impairment. However, pureed food diets are still widely used and even gaining popularity among certain groups. We tried to compare the effectiveness of gastrostomy feeding for treatment of severe malnutrition with either enteral formulas or pureed feeds.

Patients and methods

A 6-month nutritional intervention was made with 37 malnourished children, adolescents and young adults (2–26 years old) with severe neurologic impairment (Gross Motor Function Classification system [GMFCS] grade V). The individual needs were calculated. Participants were fed by gastrostomy with either enteral formulas (n = 17) or pureed food (n = 20). Measurements to assess nutritional status were made at the beginning and at the end of intervention.

Results

The Z scores for weight-for-age and for the body-mass index increased more in enteral formula than in pureed food group (2.07 vs. 0.70, p = 0.0012; and 3.75 vs. 0.63, p = 0.0014, respectively). Fat mass index increased more in enteral formula than in pureed food group (1.12 kg/m2 vs. 0.38 kg/m2; p = 0.0012). Patients in the enteral formula group showed increase in lean body mass expressed as fat-free mass index (0.70 kg/m2), while those in pureed food group did not (-0.06 kg/m2) (p = 0.0487).

Conclusions

The results suggest that even professionally planned pureed food diet is less effective than commercial enteral formula for nutritional rehabilitation of malnourished patients with severe neurologic impairment. However, larger and if possible randomised clinical studies should be made to confirm our findings.

Open access
Endobronchial ultrasound elastography strain ratio for mediastinal lymph node diagnosis

Abstract

Background. Ultrasound elastography is an imaging procedure that can assess the biomechanical characteristics of different tissues. The aim of this study was to define the diagnostic value of the endobronchial ultrasound (EBUS) elastography strain ratio of mediastinal lymph nodes in patients with a suspicion of lung cancer. The diagnostic values of the strain ratios were compared with the EBUS brightness mode (B-mode) features of selected mediastinal lymph nodes and with their cytological diagnoses.

Patients and methods. This prospective, single-centre study enrolled patients with an indication for biopsy and mediastinal staging after a non-invasive diagnostic workup of a lung tumour. EBUS with standard B-mode evaluation and elastography with strain ratio measurement were performed before endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA).

Results. Thirty-three patients with 80 suspicious mediastinal lymph nodes were included. Malignant infiltration was confirmed in 34 (42.5%) lymph nodes. The area under the receiver operating characteristic curve for the strain ratio was 0.87 (p < 0.0001). At a strain ratio ≥ 8, the accuracy for malignancy prediction was 86.25% (sensitivity 88.24%, specificity 84.78%, positive predictive value [PPV] 81.08%, negative predictive value [NPV] 90.70%). The strain ratio is more accurate than conventional B-mode EBUS modalities for differentiating between malignant and benign lymph nodes.

Conclusions. EBUS-guided elastography with strain ratio assessment can distinguish malignant from benign mediastinal lymph nodes with greater accuracy than conventional EBUS modalities. This new method may reduce the number of mediastinal EBUS-TBNAs and thus reduce the invasiveness and expense of mediastinal staging in patients with non-small lung cancer (NSCLC).

Open access