Radiomics reproducibility challenge in computed tomography imaging as a nuisance to clinical generalization: a mini-review

Abstract Background Radiomics has demonstrated striking potential in accurate cancer diagnosis but still needs strengthening of validity and standardization to achieve reproducible and generalizable results. Despite the advantages of radiomics, inter-scanner and intra-scanner variations of computed tomography (CT) scanning parameters can affect the reproducibility of its results. Accordingly, this article aims to review the impact of CT scanning parameters on the reproducibility of radiomics results. Main body of the abstract In general, radiomics results are sensitive to changes in the noise level; therefore, any parameter that affects image noise, such as kilovoltage (kVp), tube current (mAs), slice thickness, spatial resolution, image reconstruction algorithm, etc., can affect radiomics results. Also, region of interest (ROI) segmentation is another fundamental challenge in reducing radiomics reproducibility. Studies showed that almost all scanning parameters affect the reproducibility of radiomics. However, some robust features are reproducible. Short conclusion One of the solutions to overcome the radiomics reproducibility challenge is the standardization of imaging protocols according to noise level (not scanning protocols). The second solution is to list reproducible features according to the type of complication and anatomical region. Resampling may also overcome feature instability

Investigating the reproducibility of radiomics features extracted from ultrasound images as diagnostic biomarkers in patients with hepatocellular carcinoma

Background: Radiomics is a noninvasive method that reveals information from medical images that are not recognizable by the naked eye. Radiomics has shown a high potential in the accurate diagnosis and prognosis of liver lesions in ultrasound images. Despite this high potential, changes in imaging parameters affect the reproducibility of ultrasound radiomics results. Therefore, the present study aims to investigate the reproducibility of the radiomics features extracted from the images of patients with hepatocellular carcinoma under changes in ultrasound scan parameters. Methods: This was a cross-sectional study conducted from July 2020 to July 2021 in the radiology department of Tabriz Paramedical Faculty. The images of 20 patients with hepatocellular carcinoma were obtained from the Cancer Imaging Archive database. These images were taken under different imaging conditions and parameters. The areas related to the lesion were manually extracted from the images with software tools. Then, in order to radiomics analysis, different radiomics features, including 24 gray level co-occurrence matrix (GLCM) and 16 gray level run length matrix (GLRLM), were extracted from the images. Then, using the coefficient of variation (CV%) and intraclass correlation coefficient (ICC) statistical tests, the reproducibility of radiomics features under changes in scan parameters was investigated. The values of ICC≥0.90 and CV<20% were considered reproducible in this study. Results: Among the 40 features extracted from ultrasound images, eight showed high reproducibility in both CV% and ICC tests. These features were joint entropy, Idmn, Imc2, correlation, MCC, sum entropy, gray level non-uniformity normalized, and run entropy in which the two features, Idmn and gray level non-uniformity normalized, showed the highest (CV%=0.24) and the lowest (CV%=14.90) stability against the changes of ultrasound scan parameters, respectively. The average ICC value of these features was obtained at 0.977. Conclusion: Despite the high potential of radiomics in diagnosing liver lesions, changes in imaging parameters directly affect the reproducibility of results. However, some radiomics features still show high stability and reproducibility under changes in imaging parameters

Dosimetric properties of new formulation of PRESAGE ®

Aim: Tin-base catalyst is one of the widely used organometallic catalysts in polyurethane technology. The purpose of this study was to evaluate the effect of tin organometallic catalyst in the radiation response and radiological properties of a new formula of PRESAGE®. Materials and Methods: In the study, two types of PRESAGE were fabricated. A very little amount of dibutyltindillaurate (DBTDL) (0.07% weight) was used as a catalyst in the fabrication of new PRESAGE (i.e., PRESAGE with catalyst), which components were: 93.93% weight polyurethane, 5% weight tetrachloride, and 1% weight leucomalachite green (LMG). For PRESAGE without catalyst, 94% weight polyurethane, 4% weight tetrachloride, and 2% weight LMG were used. Radiochromic response and postirradiation stability of PRESAGEs were determined. Also, radiological characteristics of PRESAGEs, such as mass density, electron density, mass attenuation coefficient, and mass stopping power in different photon energies were assessed and compared with water. Results: The absorption peak of new PRESAGE compared to PRESAGE without catalyst was observed without change. Sensitivity of new PRESAGE was higher than PRESAGE without catalyst and its stability after the first 1 h was relatively constant. Also, Mass attenuation coefficient of new PRESAGE in energy ranges <0.1 MeV was 10% more than water, whereas the maximum difference of mass stopping power was only 3%. Conclusions: Tin organometallic catalyst in very low concentration can be used in fabrication of radiochromic polymer gel to achieve high sensitivity and stability as well as good radiological properties in the megavoltage photon beam

Investigation of the Field Size Effect on Wedge Field Isodose Curves Angle for Two Energies; 6 & 18 MV, produced by VARIAN 2100C Linac

Introduction: Nowadays,  considerable developments  in  the field  of  radiotherapy have  been  achieved.  They  include  the  advances  made  in  the  equipments  and  treatment  planning  techniques  which  require  highly complex calculations. Such achievements have made it possible to treat cancer patients not only  with  higher  radiation  dose  but  also  with  higher  precision  and  consequently  increasing  the  chance  of  curing the cancer. However, the conventional techniques requiring physical wedge are still being used  but with a lesser frequency. One of the wedge parameters needed to be measured is the wedge angle. It is  the angle that the horizontal line creates with the tilted isodose curve at a specific depth and for a certain  field size.   In this study, the variation of wedge angle for different field sizes was evaluated using dosimetric and  mathematical method.  Material and Methods: For the wedge fields with a dimension of 6×6 to 20×20 cm 2 , the wedge angle  for  two  photon  energies  of  6  and  18  MV  was  measured  by  the  dosimetric  method.  For  these  measurements, the conventional wedges having the nominal wedge angle of 15, 30, 45 & 60 were used.  The theoretical method suggested by Saw et al. is also used to indirectly calculate the slope of isodose  curve  by  the  dose  profile  and  percent  depth  dose  data.  The  dose  profile,  percentage  depth  dose  and  isodose curves were drawn for all the field sizes and the tilt of isodose curve at 10 cm depth, according to  international definition, is considered as the wedge angle. The data were obtained using the theoretical  equation of wedge angle and it was compared to the dosimetric data.  Results: The result obtained in this work shows that the wedge angle increases with the field size. For a  6×6 cm 2 field size, the calculated wedge angle has the highest difference in comparison to the nominal  wedge angle. The difference is equal to 14.7 degree for a 45° wedge and a 6 MV photon. The highest  difference for a 45° wedge angle, a field size of 10×10 cm 2 and a 6 MV photon is 9.2 degree. Comparing  the calculated and measured wedge angles shows a maximum difference of 4 degree for 6 and 18 MV  photon beams.  Discussion  and  Conclusion:  The  wedge  angle  varies  with  field  size.  In  order  to  get  a  better  dose  distribution in the conventional radiotherapy, it is necessary to use the appropriate wedge angle which  generates the desired slope for the isodose line and for the specific field size

Optical computed tomography in PRESAGE ®

With the advent of new complex but precise radiotherapy techniques, the demands for an accurate, feasible three-dimensional (3D) dosimetry system have been increased. A 3D dosimeter system generally should not only have accurate and precise results but should also feasible, inexpensive, and time consuming. Recently, one of the new candidates for 3D dosimetry is optical computed tomography (CT) with a radiochromic dosimeter such as PRESAGE®. Several generations of optical CT have been developed since the 90s. At the same time, a large attempt has been also done to introduce the robust dosimeters that compatible with optical CT scanners. In 2004, PRESAGE® dosimeter as a new radiochromic solid plastic dosimeters was introduced. In this decade, a large number of efforts have been carried out to enhance optical scanning methods. This article attempts to review and reflect on the results of these investigations