Performance of a Novel SUV Calculation Scheme for PET Study

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Performance of a Novel SUV Calculation Scheme for PET Study

  1. 1. Recent Advances in Applied & Biomedical Informatics and Computational Engineering in Systems Applications Performance of a Novel SUV Calculation Scheme for PET Study SOMPHOB SOONGSATHITANON*, MALULEE TUNTAWIROON, THONNAPONG THONGPRAPARN and PAWITRA MASA-AH Nuclear Medicine Division, Department of Radiology, Faculty of Medicine Siriraj Hospital, Mahidol University, 2 Prannok Rd., Bangkoknoi, Bangkok, 10700 THAILAND *Corresponding author: sissst@mahidol.ac.thAbstract: - PET/CT has become an important cancer imaging tool for both diagnosis and staging. One of themost important values for both diagnosis and staging is Standardized Uptake Value (SUV). However the dataaccessibility and analysis would be limited because the SUV is usually retrieved by using their own applicationsoftware only. In order to eradicate these limitations, a novel SUV calculation scheme based on the data fromDICOM files was created. This scheme was written by MATLAB which is widely used in science andengineer. For much more practicable, the scheme was tasted a performance by comparing with Xelerisworkstation, the well-known application from GE healthcare. The comparative analysis of both systems wasdone on 108 slices of DICOM files were obtained from 11 patients (8 men, 3 women). The results showed thatthe correlation between the two systems is statistically significant with a 99% confidence interval. The averagepercentage of accuracy is 85% for the report at a 95% confidence interval. The results of performance reassurean advanced practical use of the new scheme. The interchangeability of this scheme offers user convenienceand approachability of data and is a stand-alone application that allows more accessibility. Physicians caninterpret PET/CT scans without further applications of other software.Key-Words: - Positron Emission Tomography combined Computed tomography (PET/CT), StandardizedUptake Value (SUV), The Digital Imaging and Communications in Medicine (DICOM)1 Introduction F18-FDG is widely used techniques that are inPET/CT plays an important role in medical imaging. clinical practice today.It has been popular since it was launched to market FDG could be used as tracer for diagnosis of cancerin early 2001. The integration of PET-CT has been because FDG is an analog of glucose that the livingshown to improve the accuracy of staging in cancer. cell will be taken up in the first stage of glucoseThe benefits of PET / CT in radiation treatment pathway. The taking of FDG by cell depends on anplanning (RTP) has been widely accepted because increased of glycolytic activity in neoplastic cellof the ability to demonstrate the physiological data which is a cancer cell.of the tumor cell. PET/CT is classified as medical The simplest semi-quantitative approach is todevice that measures radioactive traces injected into estimate the concentration of tracer in a given regionthe body. from PET images by using an ROI analysis. ThePET is a non-invasive diagnostic tool that provides semi-quantitative measure of local FDG uptake hastomographic images and quantitative parameters of been developed and utilized in differentiatingthe blood perfusion, cell viability, proliferation and / benign from malignant lesion since malignantor metabolic activity of tissues. These images result lesions in general having greater uptake. SUVfrom the use of different substances of biological (Standardized Uptake Value) is the value that ofteninterest (glucose, amino acids, and hormones) used in PET scan.labeled with positron emitting radionuclides. Standardized Uptake Value (SUV) is universallyPET radiopharmaceuticals are used for diagnostic used in routine clinical practice. It is used asused for imaging of metabolic pathway in the body. parameter of the semi-quantitative in FDG - PET analysis. The SUV provides a determination of activity in a defined region of interest (ROI) ISBN: 978-1-61804-028-2 83
  2. 2. Recent Advances in Applied & Biomedical Informatics and Computational Engineering in Systems Applicationsnormalized to the patient’s body weight and 2 Methodadministered dose. Being a ratio, it is unit less and is The algorithm of the SUV calculation schemecalculated by Extract pixel intensity value from PET image. a) Define the region of interest (ROI) in the image and then extract the pixel intensity Measure Activity in Region of interest (ROI) (mCi/ml)SUV bw = value in that ROI. The maximum of the Injected Dose (mCi) value is used for SUVmax calculation. Body Weight (g) b) Convert the obtained pixel intensity value …(1) from ROI to the activity concentration inTo calculate the SUV, ROI was drawn on the image Becquerel.that was appeared on the screen by the reader The pixel intensity value represents the(physician). The computer then calculates the accumulation of activity in the region, theaverage density or maximum density in that ROI, conversion needs the parameter from thethen the decay of uptake in the period and counting metadata part which is containing allefficiency were corrected. The pixel intensity value information of the scan.in the ROI area finally was converted to the activity The attributed tags in this part includeper gram of tissue, assuming tissue density is equal Rescale Slope, Rescale Intercept, doseto 1 g/cc. [1-2] calibration and Units. (Only Rescale slopeThe body weight (kg) and injected dose (µCi(Bq)) is individual in each slice). [7-8]were together used, the SUV is calculated for the Activity Conc. in ROI (Bq/ml)ROI using Eq. 1. All process above needs a specificapplication program. = Pixel Value × Image Scale Factor × dose calibratio nEach manufacture (vendor) in the market have their …(2)own application, which is supported the files onlyfrom their equipment. Moreover the workstation of Image Scale Factor = Rescale Slope …(3)application is mostly installed nearby the equipmentor in the hospital area. The limitation of data c) Together all other related attributed tag foraccessible is the main motivation in this research. calculate SUV within a file slice.We eradicate limitation by created the application Full fill the SUV calculation formula (1) byprogram for calculate the SUV using MATLAB the actual activity and body weight whichwhich is a widely used in science and engineering. are obtained from these attributed tag i.e.In this research, DICOM (Digital imaging and Total Dose (0018,1074), Series Datecommunications in medicine) [3-4] file is used as (0008,0021), Series Time (0008,0031),the sample source. DICOM is not just an image or Radiopharmaceutical Start Timefile formats. It covers all of the data transfer, storage (0018,1072), Radiopharmaceutical Half Lifeand display protocol created and designed to cover (0018,1075) and Patient Weightall aspects of digital photography, medical (0010,1010)simplified. d) Calculate as a volume term by integral SUVA DICOM file is easily divided into two main parts from many slices. In practical, SUVwhich are the DICOM image and the metadata calculation is analyzed in the Volume of(header). The SUV calculation scheme is created Interest (VOI). So In this study , Webased on the data from both part. defined the volume of interest (VOI) andFor more practicable, the scheme was tested then summarized the SUV in every slice inperformance by comparing to the well-known the volume. The ROI of SUV from eachapplication from GE healthcare (Xeleris slice is all same position and size.workstation).This paper will present the SUV calculation scheme For more practicable the SUV calculation Schemewas create from DICOM files by using MATLAB testing is needed. This research will use the same[5-6] and performance test of the SUV scheme by sample to compare SUV from two methods. Thiscomparison of the SUV from the scheme to the SUV calculation Scheme is operated on the PC withSUV was obtain from the Xeleris workstation. For installing MATLAB. In order to evaluate themore practicable, it was tested based on patient files. performance of the scheme, it is compared to the SUV that obtained from the Well-known application software from GE healthcare (Xeleris workstation). ISBN: 978-1-61804-028-2 84
  3. 3. Recent Advances in Applied & Biomedical Informatics and Computational Engineering in Systems ApplicationsThe scheme will be tested by inputting the PET The performance of MA ss. TLAB scheme wasDICOM file. The first aspect in this comparison is tested by comparing the obtained SUVmax to theboth system need to proceed in the same file. After Xeleris Workstation.a study of GE healthcare DICOM file by doing the AccuracyPILOT STUDY, we found that GE healthcare has 14stored the DICOM file by arranged inversely. The 12first file (Slice No.1) on Xeleris is the last DICOM 10file (Slice No.277) on MATLAB. 8Both Xeleris and MATLAB ( the SUV calculation 6scheme) allow interpretation of ROI analysis. The 4circular ROIs were drawn surrounding the region of Frequency 2 Std. Dev = 6.73 Mean = 85.2FDG uptake (lesion). In each patient consisted many 0 N = 108.00of file slices according to each lesion on each 75 77 79 81 83 85 87 89 91 93 95 97 99 .0 .0 .0 .0 .0 .0 .0 .0 .0 .0 .0 .0 .0patient. The SUV in the defined region was Accuracyrecorded by the Xeleris® workstation andMATLAB.The main SUV calculation scheme was created asan application that can calculate the SUV bydrawing immediately on the DICOM files that youwant to know. Both systems needed to analyze onthe same file, and also matched region of interest(ROI). The ROI within slice was drawn in the samelocation and size. So that the another applicationneeded to be created to compare them both. It wasrun by calling the file as ROIs model (includeposition and shape) for the next DICOM file tocompare.The statistical analysis was tested using SPSSversion 11.5 and Microsoft excel. The correlationbetween two variables reflects the degree to which Fig.1 Histogram and Chart of the percentagethe variables are related. The most common measure accuracy from MATLAB and Xeleris workstation.of correlation is Pearsons Correlation. Pearsonscorrelation reflects the degree of linear relationship The percentage accuracy of MATLAB is normallybetween two variables. It is used when both distributed significantly with a 95% confidencevariables are at least at interval level and data interval.parametric. The average of percentage accuracy is 85% and forThe SUV from new MATLAB scheme was the report at 95% confidence interval, the resultcompared to the Xeleris workstation. It was ranged from 83.91% to 86.48%.performed with 108 file slices from 11 patients. The The chart in Fig.2 shows the percentage accuracy ofcorrelation of both systems was analyzed with SUV sorted by range from 0-30.Pearsons correlation technique. The accuracy ofnew scheme was tested by calculated the relativeerror between both system and distribution of theseresult were tested.3 ResultsThe SUV from Xeleris Workstation and MATLABwere compared by the Pearson correlation Test. Theresult showed high correlation coefficient of 0.974indicating a close correlation of results from Xelerisworkstation and MATLAB. R2 is 0.9487, we cansay that about 99% of comparable capability to Fig.2 Scatter gram of percentage accuracy from thepredict the SUVMATLAB from SUVXeleris, 1% remain MATLAB scheme.for other factors plus randomness. ISBN: 978-1-61804-028-2 85
  4. 4. Recent Advances in Applied & Biomedical Informatics and Computational Engineering in Systems ApplicationsThe accuracy of estimate is expressed by confident 5 Conclusioninterval with specific confidence level. At 95% The SUV from the scheme which was created byconfident interval, the accuracy of SUV from the MATLAB could be used interchangeably withMATLAB scheme is 85%. PET/CT Xeleris® workstation. It can also be used for interpretation of PET/CT image without losing the capacity to accurately measure the SUV.4 Discussion The new scheme is a stand-alone application,The related parameters which are used in this SUV running on PC with MATLAB installing. Therefore,calculation scheme are different in data type, so the the new scheme allows for more simpleconversion is mainly needed in every step. A lower interpretation of SUV. Physician can access,SUV compared to the Xeleris workstation in all interpret and analyze data without other software.study may be possible because of the data lost in The interchangeability of this scheme offers user toconversion step. the convenient and approachability of data. TheSince defined the MATLAB scheme in term of the benefit of this scheme is that it can be adopted as aamount of SUV value, we found that the small value PET/CT analysis tool to medical imaging system. Itof SUV gives high accuracy compared to the large. allows a reduction in the number of computer forIt means that the MATLAB scheme is high effective the practice. Moreover, it allows direct comparisonfor used with the small SUV. with prior study without consideration of modalityThe data viewing, analysis and interpretation in a and its archive procedure, which is beneficial in aPET / CT scanning are often done by software that multi-vendor surrounding.installed within the workstation area or where thePACS is accessible. Besides, the applicationsoftware is generally from the same manufacturer of References:the scanner. These are the problem and reason that [1] J. A. Thie, "Understanding the standardizedis leading to this research. uptake value, its methods, and implications forThe sample source of this research is DICOM files. usage," J Nucl Med, vol. 45, pp. 1431-4, SepThese are archived from PET/CT Discovery STE 2004.(DSTE) scanner [9]. In the comparative study, it [2] G. B. Saha, Basics of PET imaging : physics,was tested by comparing with the Xeleris chemistry, and regulations, 2nd ed. New York ;workstation. Both DSTE and Xeleris workstation London: Springer, 2010.are manufactured by GE healthcare and routinely [3] O. S. Pianykh, Digital imaging andoperated in Siriraj Imaging Center. communications in medicine (DICOM) : aThe SUV scheme in this research was created by practical introduction and survival guide.DICOM file based on the attribute of GE’s vendor. Berlin: Springer, 2008.Each vendor implements DICOM in its own dialect. [4] F. J.Novoa, et al., "Development of a DICOMEven though, the SUV calculation is based on the server for the reception and storage of medicalfundamental formula, but different vendor’s images in digital format," in the 4th WSEASDICOM impose slightly different method. So, this International Conference on AppliedSUV scheme was supported only for GE’s DICOM. Information and communication, Wisconsin,However, it can be simply completed more USA 2004.ultimately in a future. [5] P. Masa-Ah and S. Soongsathitanon, "A NovelThis scheme was created by using MATLAB Standardized Uptake Value (SUV) Calculationlanguage. MATLAB is a technical computing of PET DICOM Files Using MATLAB," inlanguage which is a widely used tool in science and NEW ASPECTS of APPLIED INFORMATICS,engineering community. It allows creation of user BIOMEDICAL ELECTRONICS &interfaces. Therefore, the scheme can be developed INFORMATICS and COMMUNICATIONS, P.to be the convenient and easy-to-use application N. E. Mastorakis, et al., Eds., ed: WSEASprogram with an uncomplicatedly approach. Press, 2010, pp. 413-416.Moreover, instead of MATLAB, the scheme can [6] P. Masa-Ah, et al., "A Novel Scheme foralso be written in any other programming language. Standardized Uptake Value (SUV) Calculation in PET Scans," INTERNATIONAL JOURNAL of MATHEMATICAL MODELS AND METHODS IN APPLIED SCIENCES, NAUN, vol. 4, pp. 291-299, 2010. ISBN: 978-1-61804-028-2 86
  5. 5. Recent Advances in Applied & Biomedical Informatics and Computational Engineering in Systems Applications[7] Digital Imaging and Communication in Medicine (DICOM) Positron emission tomography image objects Supplement 12 ACR-NEMA[8] "Technical Publication Advance TM 5.1 Conformance Statement for DICOM V3.0," G. M. System, Ed., ed: General Electric Healthcare, pp. 3_17-3_21.[9] "DiscoverySTE Quick Manual," G. M. System, Ed., ed: General Electric Healthcare pp. 28-38. ISBN: 978-1-61804-028-2 87

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