Limitation of Pencil Beam Convolution (PBC) Algorithm for Photon Dose Calculations in Inhomogeneous Medium
Issue:
Volume 2, Issue 1, January 2014
Pages:
1-4
Received:
6 January 2014
Published:
20 February 2014
Abstract: Purpose: The main purpose of this study is to investigate the accuracy of pencil beam convolution (PBC) algorithm when high-density inhomogeneity is involved along the photon beam path. This study will help the PBC users understand the limitation of PBC during the treatment planning of real cancer treatment plans, especially when tumor is located beyond high-density tissue such as bone. Methods: Inhomogeneous phantom (30 cm x 30 cm, 17 cm deep) with a 5 cm thick solid water as the top layer followed by 5 cm thick PVC and 7 cm solid water was manufactured for depth dose calculations and measurements. Data were obtained beyond PVC medium for three field sizes: 5 x 5 cm2, 10 x 10 cm2, and 20 x 20 cm2. Dose calculations were performed using PBC and measurements were done using chamber. Measured and calculated data were compared against each other. Results: PBC produced dose prediction errors beyond high density medium by 3.7% to 7.3% for field size 5 x 5 cm2, by 4.8% to 6.9% for field size 10 x 10 cm2, and by 5.9% to 7.3% for field size 20 x 20 cm2. The results of this study, however, showed no clear dependency on the field size. Similarly, difference between the PBC and measurements did not show a clear trend when results at various points were compared with each other. Conclusion: PBC can overestimate the dose by up to 7.3% beyond high-density medium. High density materials such metallic immobilization devices must be avoided in the beam path during the patient treatment.
Abstract: Purpose: The main purpose of this study is to investigate the accuracy of pencil beam convolution (PBC) algorithm when high-density inhomogeneity is involved along the photon beam path. This study will help the PBC users understand the limitation of PBC during the treatment planning of real cancer treatment plans, especially when tumor is located b...
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Chitotriosidase Activity in Different Stages of Hepatitis C. It may a Possible Tumor Marker for Hepatocellular Carcinoma
Engin ALTINTAS,
Serkan Yaras,
Burak CIMEN,
Enver UCBILEK,
Bunyamin SARITAS,
Fehmi ATES,
Orhan SEZGIN,
Gulhan OREKECI
Issue:
Volume 2, Issue 1, January 2014
Pages:
5-8
Received:
24 December 2013
Published:
10 March 2014
Abstract: Chitotriosidase is synthesized and secreted especially in activated macrophages. The aim of this study was to evaluate chitotriosidase activity in patients with various stages of hepatitis C. The study included a total of 90 patients. The patients were divided into four groups. Group 1 included 54 patients with chronic active hepatitis, Group 2 included 20 patients with recovered HCV, Group 3 included 6 patients with HCV induced hepatocellular carcinoma, and Group 4 included 10 patients with HCV cirrhosis. Chitotriosidase activity was measured with spectrophotometry (SigmaAldrich ®). The mean chitotriosidase activity of the four groups was 0,927u/L (0.804u/L in Group 1, 0.521u/L in Group 2, 3.211u/L in Group 3 and 1.030u/L in Group 4). Chitotriosidase activity was significantly higher in Group 3. ROC analysis, used to evaluate chitotriosidase activity for the diagnosis of hepatocellular carcinoma, showed that chitotriosidase activity of 0,935 was below the curve (CI: 95%; 0,862 - 0,976), which was statistically significant (p= 0,0001). The cut-off value was >1,098 with a sensitivity of 100% and a specifity of 81%. Chitotriosidase activity can be a marker with a high sensitivity and specifity for the diagnosis of hepatocellular carcinoma.
Abstract: Chitotriosidase is synthesized and secreted especially in activated macrophages. The aim of this study was to evaluate chitotriosidase activity in patients with various stages of hepatitis C. The study included a total of 90 patients. The patients were divided into four groups. Group 1 included 54 patients with chronic active hepatitis, Group 2 inc...
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