Pusat Pengajian Sains Kesihatan - Monograf
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- PublicationImpact of BPL penalty functions and PSF models in PET/CT radial spatial resolution recovery(2024-07)Si, Wang JieIntroduction: A conventional three-point source method adhering to NEMA NU 2-2018 has been introduced where three-point sources are placed at 1 cm, 10 cm, and 20 cm within the PET/CT FOV to evaluate impact of radial distance on spatial resolution. Advanced reconstruction algorithms like TOF, BPL, and PSF models, along with OSEM have shown spatial resolution enhancements based on the FWHM measured. Combining OSEM with TOF improves event localization, and PSF modelling mitigates parallax effects. However, OSEM often struggles with full convergence, necessitating BPL with smooth penalty functions (β values) for regularized iterative reconstruction. Since National Cancer Institute (NCI) currently practice OSEM+TOF+PSF+BPL (β 450) as the in-house protocol, this study explores alternative BPL and PSF functions in OSEM to enhance spatial resolution and determine optimal β values for NCI's routine clinical use. Methods: In-house spatial resolution phantom acquisition was conducted using single F-18 point source method with activity > 5mCi/cc. A capillary tube was used to draw the selected drop, creating the point source with volume 1 mm3. Tubes filled were placed at 5 cm intervals from the center towards the PET/CT FOV's periphery. Scans were done with default settings of scout view, followed by CT axial slice scan and subsequently PET scan with 1 minute per bed position. PET data was then reconstructed with OSEM+TOF, OSEM+TOF+PSF, and OSEM+TOF+PSF+BPL (β 200,400,450, 600,800,1000 and 1200). Tangential and radial FWHM of the point source at different radial distances and locations were calculated by using Xeleris Functional Imaging Workstation Version 4.1. Radial distance effects on spatial resolution under the NCI protocol (OSEM+TOF+PSF+BPL with β450) and varying BPL β values (β 200-1200) were evaluated using fitted function slopes. Additionally, different reconstruction algorithms' impact on spatial resolution within PET/CT FOV was assessed using standard deviation calculations and plotting error bars to show spreading of the data around the mean as well as to determine the significant difference between the FWHM measured using different types of reconstruction. Result: The tangential FWHM at Location D was the only measurement that aligned with the theoretical prediction, increasing linearly with the increment of the radial distance from 1.10 mm to 1.76 mm (R2 = 0.8602). Additionally, OSEM+TOF+PSF+BPL provided greatest spatial resolution compared to OSEM+TOF and OSEM+TOF+PSF, where BPL with β200 reduced FWHM measurements closed to actual size of point source. Conclusion: OSEM+TOF+PSF+BPL (β200) reconstruction algorithms is suggested to be the optimum reconstruction algorithm that can be practiced by NCI in clinical setting due to best radial spatial resolution recovery even with increased of radial distances.
- PublicationInvestigation of gamma index parameters in patient specific quality assurance (PSQA) for radiotherapy treatment planning technique: retrosective study(2024-06)Mukhtar, Siti Yuni SaraThe patient specific quality assurance (PSQA) is a pre-treatment procedure performed to evaluate the validity of the inversed treatment plans, before the actual radiotherapy (RT) treatment delivery, to ensure the patient’s safety. The current method applied for the PSQA assessment in Hospital Universiti Sains Malaysia (HUSM) department is the ArcCHECK phantom based measurement using 3%/3mm gamma index (GI) analysis and currently, there is no standard procedure to perform the PSQA assessment. The aim of this study is to investigate the GI parameters (3%/3mm, 3%/2mm, 2%/2mm, 2%/1mm and 1%/1mm) in Volumetric modulated arc therapy (VMAT), intensity-modulated radiation therapy (IMRT) and Stereotactic body radiation therapy (SBRT) across various treatment regions retrospectively. The gamma passing rate (GPR) of 95% is the universal tolerance limit provide by the American Association of Physicist in Medicine Task Group 218 (AAPM TG-218). The GPR result indicated the PSQA cases were able to fulfill the 95% limit when 3%/3mm 3%/2mm and 2%/2mm GI parameter were applied with the result of 92.5% (99 cases), 100% (29 cases) and 87.5% (14 cases) for 3%/3mm, 82 cases (82.8%),18 cases (62.1%) and 8 cases (57.1%) for 3%/2mm, meanwhile for 2%/2mm, 46 cases (46.5%), 6 cases (20.7%) and 6 cases (42.9%) respectively for VMAT, IMRT and SBRT. Consequently, the GPR tolerance limit were also evaluated and reflected that 3%/2mm (≥95%), and 2%/2mm (>90%) is applicable for IMRT, VMAT and SBRT as the tolerance limit aligns with the suggestion by the previous study. Subsequently, The GPR tolerance limit for different treatment technique indicates a significant difference (p<0.05) in tolerance limit between IMRT and VMAT when applied using 3%/2mm (≥97.19%) and (≥94.85%), 2%/2mm (≥93.74%) and (≥90.39%). Moreover, The GPR tolerance limit for different treatment region reflect a significant different (p<0.05) when VMAT 3%/2mm is applied for HN (≥97 %), Pelvic (≥ 96%) and Chest (≥ 98%). In conclusion this study proves that apart from 3%/3mm (≥95%), 3%/2mm (≥95%) and 2%/2mm (>90%) are suitable for IMRT, VMAT and SBRT cases for all treatment region to be applied in HUSM, except for IMRT and VMAT when applied on HN region, as well as for VMAT when applied on HN, pelvic and chest region using 3%/2mm.
- PublicationThe effects of CT-based attenuation correction on the accuracy of 99mtc SPECT/CT quantification(2024-08)Vijayakumar, Shamalah SThis study focuses on how CT- based attenuation correction affects the precision of quantification using Technetium-99m (99mTc) single-photon emission computed tomography/computed tomography (SPECT/CT). Functional and anatomical imaging are combined in SPECT/CT in nuclear medicine which is essential for precise diagnosis and therapy planning. To reduce patient exposure while retaining the image quality, CT scan radiation doses must be lowered. Therefore, this study investigates how varying CT current (mA) affects 99mTc SPECT/CT image quality overall and photon attenuation correction accuracy. In terms of methodology, the study used NEMA 2012/IEC 2008 phantoms filled with 99mTc and the GE Discovery NM/CT 670 Pro SPECT/CT system, using tumor-to-background ratios (TBR) of 4:1 and 10:1. The effects of various mA levels (30, 60, 90, 100, and 120 mA) on quantification accuracy and image quality were investigated. Image quantification and reconstruction were made easier using the Q.Metrix software and the Xeleris workstation, respectively. To evaluate the quality of the images, important metrics like contrast, signal-to-noise ratio (SNR) and coefficient of variation (COV) were examined. Recovery coefficients (RC) were utilised for quantitative analysis. According to the findings, low-dose CT which is accomplished by reducing the tube current can generate images with sufficient quality for precise quantification in 99mTc SPECT/CT. The study supports the ALARA (As Low As Reasonably Achievable) principle by showing that radiation exposure to patients can be decreased without sacrificing diagnostic accuracy. The significance of these findings lies in their potential to improve patient safety by lowering radiation doses while maintaining accurate and trustworthy diagnostic imaging.
- PublicationEvaluation of patient dose during multi-catheter insertion in CT-guided interstitial liver brachytherapy(2024-07)Sivaprakasam, PuviyaIntroduction: Brachytherapy is a type of cancer treatment that involves placing an encapsulated radioactive source either near or directly into the tumour. Liver brachytherapy has been practiced in institutions where multiple catheters are inserted into the liver under CT-guidance. Numerous studies have acknowledged the dose received during brachytherapy, however, the dose received during CT-guided multi-catheter insertion lacks in discussion, hence, the optimisation of the procedure is presented by investigating various aspects of the procedure. Objectives: This study aims to evaluate the patient dose received from multi-catheter insertion during interstitial liver brachytherapy, to determine the association between number of catheters with the CT dose values (𝐶𝑇𝐷𝐼𝑣𝑜𝑙 and total DLP) and to evaluate the organ dose for the patients undergoing multi-catheter insertion in CT-guided interstitial liver brachytherapy using IndoseCT software as well. Methods: This study involved a retrospective survey on 18 patients who undergone CT-guided multi-catheter insertion for liver brachytherapy for evaluation of the patient dose received from the procedure. Patients’ demographic information (age and gender), CT data (number of catheters, number of CT phases, exposure settings – kVp, mAs, pitch and scan length (in cm)), patient dose data (𝐶𝑇𝐷𝐼𝑣𝑜𝑙(in mGy) and total DLP (in mGy.cm)), volume of lesion (in cm3) and diameter of lesion (in cm) were retrieved from CT workstation and recorded for further analysis. Besides that, the axial CT images of patients were obtained and retrieved from the Picture Archiving and Communication System (PACS) for further analysis. The collected CT images were uploaded in the IndoseCT software (Version 20b) to estimate the organ dose (developed by Anam et al., 2021). Result: Number of catheters showed weak correlation with CT dose indices (CTDIvol and total DLP) and number of CT phases while number of catheters had strong correlation with volume and diameter of lesion. Furthermore, the organ that received the highest dose for patient undergone RTP Abdomen HCT 3 mm protocol was heart with 755.79 mGy, while kidneys received the highest dose (964.79 mGy) for patients underwent RTP Abdo/Pelvis HCT 3 mm protocol. Conclusion: The examination of association between variables used in the procedures is extremely important to further optimise the procedure as well as provide insight on accurate decision making for future advancements.
- PublicationA comprehensive 3D dosimetric analysis of the vienna ring applicator in high-dose-rate (HDR) brachytherapy for cervical cancer treatment: TLD measurement(2024)Sivaprakasam, PugalyaIntroduction: Intracavitary brachytherapy is the most common approach used for gynecological cancers which happens to be the cancer with highest occurrence among women. Intracavitary-interstitial (IC/IS) brachytherapy is an approach that is developed, and various applicators are utilised in this treatment method such as the Vienna Ring applicator. However, a comprehensive understanding on the dosimetric behavior of Vienna Ring applicator is required for efficient use in brachytherapy for cervical cancer. Purpose: This study aims to experimentally analyse the dosimetric performance of Vienna Ring applicator in aspects of target coverage, organ at risk (OAR) sparing and ability to deliver the planned dose during treatment. Methods and Materials: A Vienna Ring applicator was assembled in a pelvic phantom with Thermoluminescence Dosimeters (TLD-100) chips were attached to the OARs (bladder and rectum) to act as markers. Computed Tomography (CT) images were obtained for treatment planning. 7Gy was prescribed for irradiation and the treatment was planned for the assessment of dose received by target, OAR and the TLDs at 8 points. The dose measured by the TLD-100 chips during the irradiation and dose calculated by treatment planning system (TPS) on the TLD points were compared. Results: The dose received by target, bladder and rectum are 7.1 Gy, 2.4 Gy and 7.4 Gy respectively as obtained from TPS. Out of 8 TLDs, 7 TLDs have dose deviation less than 20% while 1 TLD (F7) have dose deviation of 31.03% between measured and calculated dose. Conclusion: The dose distribution of Vienna ring applicator to GTV is not homogenous but has high degree of conformity. The Vienna ring applicator was able to spare the bladder and deliver optimum dose to tumour. The Vienna ring applicator can deliver planned dose during treatment delivery due to 90% of the dose deviation was below 20%. Therefore, the applicator can be categorised as a reliable applicator in brachytherapy for cervical cancer.