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.th
Abstract: - PET/CT has become an important cancer imaging tool for both diagnosis and staging. One of the
most important values for both diagnosis and staging is Standardized Uptake Value (SUV). However the data
accessibility and analysis would be limited because the SUV is usually retrieved by using their own application
software only. In order to eradicate these limitations, a novel SUV calculation scheme based on the data from
DICOM files was created. This scheme was written by MATLAB which is widely used in science and
engineer. For much more practicable, the scheme was tasted a performance by comparing with Xeleris
workstation, the well-known application from GE healthcare. The comparative analysis of both systems was
done on 108 slices of DICOM files were obtained from 11 patients (8 men, 3 women). The results showed that
the correlation between the two systems is statistically significant with a 99% confidence interval. The average
percentage of accuracy is 85% for the report at a 95% confidence interval. The results of performance reassure
an advanced practical use of the new scheme. The interchangeability of this scheme offers user convenience
and approachability of data and is a stand-alone application that allows more accessibility. Physicians can
interpret PET/CT scans without further applications of other software.
Key-Words: - Positron Emission Tomography combined Computed tomography (PET/CT), Standardized
Uptake Value (SUV), The Digital Imaging and Communications in Medicine (DICOM)
1 Introduction F18-FDG is widely used techniques that are in
PET/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 cancer
in early 2001. The integration of PET-CT has been because FDG is an analog of glucose that the living
shown to improve the accuracy of staging in cancer. cell will be taken up in the first stage of glucose
The benefits of PET / CT in radiation treatment pathway. The taking of FDG by cell depends on an
planning (RTP) has been widely accepted because increased of glycolytic activity in neoplastic cell
of 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 to
device that measures radioactive traces injected into estimate the concentration of tracer in a given region
the body. from PET images by using an ROI analysis. The
PET is a non-invasive diagnostic tool that provides semi-quantitative measure of local FDG uptake has
tomographic images and quantitative parameters of been developed and utilized in differentiating
the blood perfusion, cell viability, proliferation and / benign from malignant lesion since malignant
or metabolic activity of tissues. These images result lesions in general having greater uptake. SUV
from the use of different substances of biological (Standardized Uptake Value) is the value that often
interest (glucose, amino acids, and hormones) used in PET scan.
labeled with positron emitting radionuclides. Standardized Uptake Value (SUV) is universally
PET radiopharmaceuticals are used for diagnostic used in routine clinical practice. It is used as
used 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)
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2. Recent Advances in Applied & Biomedical Informatics and Computational Engineering in Systems Applications
normalized to the patient’s body weight and 2 Method
administered dose. Being a ratio, it is unit less and is The algorithm of the SUV calculation scheme
calculated 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 in
To 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, the
average density or maximum density in that ROI, conversion needs the parameter from the
then the decay of uptake in the period and counting metadata part which is containing all
efficiency 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 include
per gram of tissue, assuming tissue density is equal Rescale Slope, Rescale Intercept, dose
to 1 g/cc. [1-2] calibration and Units. (Only Rescale slope
The 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 specific
application program. = Pixel Value × Image Scale Factor × dose calibratio n
Each manufacture (vendor) in the market have their …(2)
own application, which is supported the files only
from their equipment. Moreover the workstation of Image Scale Factor = Rescale Slope …(3)
application is mostly installed nearby the equipment
or in the hospital area. The limitation of data c) Together all other related attributed tag for
accessible 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) by
program for calculate the SUV using MATLAB the actual activity and body weight which
which 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 Date
communications 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 Time
file formats. It covers all of the data transfer, storage (0018,1072), Radiopharmaceutical Half Life
and display protocol created and designed to cover (0018,1075) and Patient Weight
all aspects of digital photography, medical (0010,1010)
simplified. d) Calculate as a volume term by integral SUV
A DICOM file is easily divided into two main parts from many slices. In practical, SUV
which 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 , We
based on the data from both part. defined the volume of interest (VOI) and
For more practicable, the scheme was tested then summarized the SUV in every slice in
performance by comparing to the well-known the volume. The ROI of SUV from each
application 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 Scheme
was 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. This
comparison of the SUV from the scheme to the SUV calculation Scheme is operated on the PC with
SUV was obtain from the Xeleris workstation. For installing MATLAB. In order to evaluate the
more 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).
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3. Recent Advances in Applied & Biomedical Informatics and Computational Engineering in Systems Applications
The scheme will be tested by inputting the PET The performance of MA ss. TLAB scheme was
DICOM file. The first aspect in this comparison is tested by comparing the obtained SUVmax to the
both system need to proceed in the same file. After Xeleris Workstation.
a study of GE healthcare DICOM file by doing the Accuracy
PILOT STUDY, we found that GE healthcare has 14
stored the DICOM file by arranged inversely. The 12
first file (Slice No.1) on Xeleris is the last DICOM 10
file (Slice No.277) on MATLAB. 8
Both Xeleris and MATLAB ( the SUV calculation 6
scheme) allow interpretation of ROI analysis. The 4
circular ROIs were drawn surrounding the region of
Frequency
2 Std. Dev = 6.73
Mean = 85.2
FDG uptake (lesion). In each patient consisted many 0 N = 108.00
of file slices according to each lesion on each
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99
.0
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patient. The SUV in the defined region was Accuracy
recorded by the Xeleris® workstation and
MATLAB.
The main SUV calculation scheme was created as
an application that can calculate the SUV by
drawing immediately on the DICOM files that you
want to know. Both systems needed to analyze on
the same file, and also matched region of interest
(ROI). The ROI within slice was drawn in the same
location and size. So that the another application
needed to be created to compare them both. It was
run by calling the file as ROIs model (include
position and shape) for the next DICOM file to
compare.
The statistical analysis was tested using SPSS
version 11.5 and Microsoft excel. The correlation
between two variables reflects the degree to which Fig.1 Histogram and Chart of the percentage
the variables are related. The most common measure accuracy from MATLAB and Xeleris workstation.
of correlation is Pearson's Correlation. Pearson's
correlation reflects the degree of linear relationship The percentage accuracy of MATLAB is normally
between two variables. It is used when both distributed significantly with a 95% confidence
variables are at least at interval level and data interval.
parametric. The average of percentage accuracy is 85% and for
The SUV from new MATLAB scheme was the report at 95% confidence interval, the result
compared 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 of
correlation of both systems was analyzed with SUV sorted by range from 0-30.
Pearson's correlation technique. The accuracy of
new scheme was tested by calculated the relative
error between both system and distribution of these
result were tested.
3 Results
The SUV from Xeleris Workstation and MATLAB
were compared by the Pearson correlation Test. The
result showed high correlation coefficient of 0.974
indicating a close correlation of results from Xeleris
workstation and MATLAB. R2 is 0.9487, we can
say that about 99% of comparable capability to Fig.2 Scatter gram of percentage accuracy from the
predict the SUVMATLAB from SUVXeleris, 1% remain MATLAB scheme.
for other factors plus randomness.
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4. Recent Advances in Applied & Biomedical Informatics and Computational Engineering in Systems Applications
The accuracy of estimate is expressed by confident 5 Conclusion
interval with specific confidence level. At 95% The SUV from the scheme which was created by
confident interval, the accuracy of SUV from the MATLAB could be used interchangeably with
MATLAB 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 simple
conversion 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 to
conversion step. the convenient and approachability of data. The
Since defined the MATLAB scheme in term of the benefit of this scheme is that it can be adopted as a
amount of SUV value, we found that the small value PET/CT analysis tool to medical imaging system. It
of SUV gives high accuracy compared to the large. allows a reduction in the number of computer for
It means that the MATLAB scheme is high effective the practice. Moreover, it allows direct comparison
for used with the small SUV. with prior study without consideration of modality
The data viewing, analysis and interpretation in a and its archive procedure, which is beneficial in a
PET / CT scanning are often done by software that multi-vendor surrounding.
installed within the workstation area or where the
PACS is accessible. Besides, the application
software is generally from the same manufacturer of References:
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5. Recent Advances in Applied & Biomedical Informatics and Computational Engineering in Systems Applications
[7] Digital Imaging and Communication in
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