14 noise contrast noise ratio cnr 15 contrast noise ratio

The contrast to noise ratio (CNR) as calculated by the PIPSpro software is defined as:

to maintain the contrast to noise ratio cnr the noise

The variation in noise and contrast to noise ratio are displayed in . The blue line is the baseline generated by taking the average of noise over a week. The baseline for CNR and noise was set to 34.5 and 64.5, respectively. The accepted deviation was set to 10% for both CNR and noise, based on the Varian linac study() and PIPSpro manual. The green area is within acceptable parameters range; yellow area indicates caution level, and pink area indicates rejection areas, respectively. It can be noted that the noise and CNR lies in the acceptable range over the period four months.

Fig. 8. Variation of noise and contrast to noise ratio over a period of four months in the TomoTherapy machine.

image noise, signal to noise ratio and contrast to noise ratio

The QC-3 phantom can be used to perform the following tests: relative modulation transfer function (RMTF), spatial resolution, signal to noise ratio, and contrast to noise ratio (CNR). The use of QC-3 phantom to determine the quality assurance of the electric portal imaging device (EPID) using the software PIPSpro, which provides the frequencies at 50%, 40% and 30% (f50, f40 and f30) of the maximum RMTF, has been extensively studied in literature.(,) We have used the software to study the consistency of noise and CNR in the MVCT images acquired using TomoTherapy.

The contrast to noise ratio is the ability to visualize different tissues through noise

Quantitative image quality was determined by measuring signal intensity (HU), IN, signal to noise ratio (SNR) and contrast to noise ratio (CNR) using established criteria , at the left ventricle and LMA on the axial images using a Vitrea work station (Vital Images, version 5.2). Then equal size regions of interest (ROI = 30 mm 3 ) were taken in the contrast filled left ventricle and left ventricular wall. IN was calculated from the standard deviation of Hounsfield density values (HU) within the ROI in the left ventricle. SNR was defined as the ratio of mean signal intensity (HU) divided by IN. CNR was defined as the difference between the mean density (HU) of the left ventricle and left ventricular wall divided by IN. ,,, An ROI was then placed in the LMA and perivascular tissue adjacent to the LMA to determine SNR and CNR of the LMA , and .

Subject: contrast to noise ratio From: Syafeeqa Date: 18 Jan, 2007 19:51:16 Message: 1 of 1