Displaying publications 21 - 40 of 1500 in total

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  1. Reduwan NH, Abdul Aziz AA, Mohd Razi R, Abdullah ERMF, Mazloom Nezhad SM, Gohain M, et al.
    BMC Oral Health, 2024 Feb 19;24(1):252.
    PMID: 38373931 DOI: 10.1186/s12903-024-03910-w
    BACKGROUND: Artificial intelligence has been proven to improve the identification of various maxillofacial lesions. The aim of the current study is two-fold: to assess the performance of four deep learning models (DLM) in external root resorption (ERR) identification and to assess the effect of combining feature selection technique (FST) with DLM on their ability in ERR identification.

    METHODS: External root resorption was simulated on 88 extracted premolar teeth using tungsten bur in different depths (0.5 mm, 1 mm, and 2 mm). All teeth were scanned using a Cone beam CT (Carestream Dental, Atlanta, GA). Afterward, a training (70%), validation (10%), and test (20%) dataset were established. The performance of four DLMs including Random Forest (RF) + Visual Geometry Group 16 (VGG), RF + EfficienNetB4 (EFNET), Support Vector Machine (SVM) + VGG, and SVM + EFNET) and four hybrid models (DLM + FST: (i) FS + RF + VGG, (ii) FS + RF + EFNET, (iii) FS + SVM + VGG and (iv) FS + SVM + EFNET) was compared. Five performance parameters were assessed: classification accuracy, F1-score, precision, specificity, and error rate. FST algorithms (Boruta and Recursive Feature Selection) were combined with the DLMs to assess their performance.

    RESULTS: RF + VGG exhibited the highest performance in identifying ERR, followed by the other tested models. Similarly, FST combined with RF + VGG outperformed other models with classification accuracy, F1-score, precision, and specificity of 81.9%, weighted accuracy of 83%, and area under the curve (AUC) of 96%. Kruskal Wallis test revealed a significant difference (p = 0.008) in the prediction accuracy among the eight DLMs.

    CONCLUSION: In general, all DLMs have similar performance on ERR identification. However, the performance can be improved by combining FST with DLMs.

    Matched MeSH terms: Cone-Beam Computed Tomography; Spiral Cone-Beam Computed Tomography*
  2. Chan R, Kumar G, Abdullah B, Ng Kh, Vijayananthan A, Mohd Nor H, et al.
    Biomed Imaging Interv J, 2011 Apr;7(2):e12.
    PMID: 22287986 MyJurnal DOI: 10.2349/biij.7.2.e12
    To optimize the delay time before the initiation of arterial phase scan in the detection of focal liver lesions in contrast enhanced 5 phase liver CT using the bolus tracking technique.
    Matched MeSH terms: Tomography, X-Ray Computed
  3. Fathinul Fikri A, Lau W
    Biomed Imaging Interv J, 2010 10 01;6(4):e37.
    PMID: 21611073 DOI: 10.2349/biij.6.4.e37
    An incidental finding of an intense focus of (18)F-Fluorodeoxyglucose (FDG) pulmonary uptake on positron emission tomography (PET) without detectable lesions on computed tomography (CT) is highly suggestive of FDG microembolus. Its microscopic nature means it is undetectable on CT. It is an artefact attributable to (18)F-FDG-tracer contamination at the injection site. This paper reports a case of a 61 year-old lady with a past history of breast carcinoma, in whom follow-up PET/CT images demonstrated an incidental intense FDG pulmonary abnormality. A follow-up PET/CT seven months later demonstrated complete resolution of the abnormality.
    Matched MeSH terms: Tomography, X-Ray Computed; Positron-Emission Tomography; Positron Emission Tomography Computed Tomography
  4. Abd Samat, A.H., Ida, Z.Z., Yat, Keong Y., Isa, M.H.
    Medicine & Health, 2020;15(2):297-305.
    MyJurnal
    Kenaikan segmen ST di elektrod aVR elektrokardiografi di dalam kes diseksi aorta mempunyai risiko kematian yang tinggi. Ia melibatkan diseksi yang berlaku di akar aorta. Kami melaporkan kes pesakit lelaki muda yang menghidap penyakit darah tinggi, yang datang ke Jabatan Kecemasan dengan sakit dada dan sakit di bahagian kaki. Pemeriksaan fizikal pada bahagian bawah kiri anggota adalah konsisten dengan iskemia akut. Elektrokardiogram menunjukkan serangan jantung akut di bahagian elektrod anterolateral, dan kenaikan ST segmen di elektrod aVR. Ekokardiografi menunjukkan akar aorta yang berukuran 4.51 cm dan kehadiran flap intimal, meningkatkan kebarangkalian diseksi pada akar aorta dan arteri koronari. Tomography Computed Angiogram menunjukkan terdapat diseksi aorta dari akar aorta termasuk flap intimal berhampiran permulaan arteri koronari kiri, hingga ke arteri iliac utama ke arteri iliac kiri. Malangnya, pesakit memilih untuk tidak menjalani pembedahan dan akhirnya meninggal dunia selepas 48 jam di masukkan ke wad. Kes ini menjelaskan bahawa, dalam kes diseksi aorta yang hadir dengan sindrom 'malperfusion', kenaikan segmen ST pada elektrod aVR akan meningkatkan kebarangkalian terjadinya diseksi aorta yang teruk melibatkan akar aorta dan juga arteri koronari, yang menjadikan prognosis pesakit lebih teruk.
    Matched MeSH terms: Tomography
  5. Aferka, S., Abdullah, J., Olujic, Z., Saroha, A.K., Crine, M., Toye, D., et al.
    MyJurnal
    This work focuses on the use of X-ray tomography in investigating the flow distribution in a structured packed bed. Cross sections of the liquid hold up distribution in a 10 cm diameter column packed with Katapak-SP12 are obtained at various column heights for different liquid flow rates. The repartition of the liquid hold up between baskets and corrugated sheets is quantified. Wall wipers and column wall effects are visualized. Results are obtained from an initially dry column without gas flow.
    Matched MeSH terms: Tomography, X-Ray
  6. Ahmad Saad FF, Zakaria MH, Appanna B
    J Int Med Res, 2018 Aug;46(8):3138-3148.
    PMID: 29781364 DOI: 10.1177/0300060518773019
    Objectives 18F-choline is a useful tracer for detecting tumours with high lipogenesis. Knowledge of its biodistribution pattern is essential to recognise physiological variants. The aim of this study was to describe the physiologic distribution of 18F-choline and pitfalls in patients with breast cancer. Methods Twenty-one consecutive patients with breast cancer (10 premenopausal and 11 postmenopausal women; mean age, 52.82 ± 10.71 years) underwent 18F-choline positron emission tomography (PET)/computed tomography (CT) for staging. Whole-body PET/CT was acquired after 40 minutes of 18F-choline uptake. Acquired PET images were measured semiquantitatively. Results All patients showed pitfalls unrelated to breast cancer. These findings were predominantly caused by physiological glandular uptake in the liver, spleen, pancreas, bowels, axial skeleton (85%-100%), inflammation and benign changes (4.76%), appendicular skeleton (4.76%-19.049%), and site contamination (61.9%). In <1%, a concomitant metastatic neoplasm was found. The breast showed higher physiological uptake in premenopausal compared with postmenopausal woman (18F-choline maximum standardised uptake values [g/dL] of the right breast = 2.04 ± 0.404 vs 1.59 ± 0.97 and left breast = 2.00 ± 0.56 vs 1.93 ± 1.28, respectively). Conclusion 18F-choline uptake was higher in premenopausal women. Physiological 18F-choline uptake was observed in many sites, representing possible pathologies.
    Matched MeSH terms: Positron Emission Tomography Computed Tomography*
  7. Abdul Aziz AF, Mohamed AR, Murugesu S, Siti Zarina AH, Lee BN
    Med J Malaysia, 2021 07;76(4):502-509.
    PMID: 34305111
    BACKGROUND: Scalp video electroencephalography monitoring (VEM) and brain MRI sometime fail to identify the epileptogenic focus (EF) in patients with drug resistant epilepsy (DRE). 18F-FDG PET/CT has been shown to improve the detection of EF in patients but is not widely used in Malaysia. Thus, the objective of this study was to identify whether 18F-FDG PET/CT conferred an added benefit in the pre-surgical evaluation of DRE.

    METHODS: Retrospective review of 119 consecutive paediatric patients referred for 18F-FDG-PET/CT at the Department of Nuclear Medicine of the National Cancer Institute, Putrajaya. All had DRE and underwent evaluation at the Paediatric Institute, Hospital Kuala Lumpur. Visually detected areas of 18F-FDG-PET/CT hypometabolism were correlated with clinical, MRI and VEM findings.

    RESULTS: Hypometabolism was detected in 102/119 (86%) 18FFDG- PET/CT scans. The pattern of hypometabolism in 73 patients with normal MRI was focal unilobar in 16/73 (22%), multilobar unilateral in 8/73 (11%), bilateral in 27/73 (37%) and global in 5/73 (7%) of patients; whilst 17/73 (23%) showed normal metabolism. In 46 patients with lesions on MRI, 18F-FDG-PET/CT showed concordant localisation and lateralization of the EF in 30/46 (65%) patients, and bilateral or widespread hypometabolism in the rest. Addition of 18FFDG PET/CT impacted decision making in 66/119 (55%) of patients; 24/73 with non-lesional and 30/46 patients with lesional epilepsies were recommended for surgery or further surgical work up, whilst surgery was not recommended in 11/46 patients with lesional epilepsy due to bilateral or widespread hypometabolism. 25 patients subsequently underwent epilepsy surgery, with 16/25 becoming seizure free following surgery.

    CONCLUSION: 18F-FDG-PET/CT has an added benefit for the localization and lateralization of EF, particularly in patients with normal or inconclusive MRI.

    Matched MeSH terms: Positron Emission Tomography Computed Tomography*
  8. Rabba JA, Suhaimi FM, Mat Jafri MZ, Jaafar HA, Osman ND
    Radiography (Lond), 2023 May;29(3):533-538.
    PMID: 36913788 DOI: 10.1016/j.radi.2023.02.028
    INTRODUCTION: The daily image quality assessment involves large datasets that consume a lot of time and effort. This study aims to evaluate a proposed automated calculator for image distortion analysis in 2-dimensional (2D) panoramic imaging mode for a dental cone beam computed tomography (CBCT) system in comparison with present manual calculations.

    METHODS: A ball phantom was scanned using panoramic mode of the Planmeca ProMax 3D Mid CBCT unit (Planmeca, Helsinki, Finland) with standard exposure settings used in clinical practice (60 kV, 2 mA, and maximum FOV). An automated calculator algorithm was developed in MATLAB platform. Two parameters associated with panoramic image distortion such as balls diameter and distance between middle and tenth balls were measured. These automated measurements were compared with manual measurement using the Planmeca Romexis and ImageJ software.

    RESULTS: The findings showed smaller deviation in distance difference measurements by proposed automated calculator (ranged 3.83 mm) as compared to manual measurements (ranged 5.00 for Romexis and 5.12 mm for ImageJ software). There was a significant difference (p 

    Matched MeSH terms: Cone-Beam Computed Tomography/methods; Spiral Cone-Beam Computed Tomography*
  9. Masoomi MA, Al-Shammeri I, Kalafallah K, Elrahman HMA, Ragab O, Ahmed E, et al.
    Medicine (Baltimore), 2019 Jan;98(4):e14207.
    PMID: 30681596 DOI: 10.1097/MD.0000000000014207
    Many discrepancy in selection of proper filter and its parameters for individual cases exists. The authors investigate the impact of the most common filters on patient NM images with coronary artery disease (CAD), and compare the results with the computerized tomography (CT)-Angio and angiography for accuracy.The investigation initiated by performing various single photon emission computerized tomography (SPECT)/CT scan of the national electrical manufacturers association chest phantoms having hot and cold inserts. Data acquired on GE 670 PRO SPECT/CT; 360Ø, 64 frames, 60 seconds, low energy high resolution (LEHR) 128, low energy general purpose (LEGP) with CT attenuation (120 kV and 170 mA). The images reconstructed with filtered back projection and ITERATIVE ordered-subset expectation maximization utilizing filters; Hann, Butterworth, Metz, Hamming, and Wiener. The Image contrast was calculated to assess absolute nearness of the inserts. Based on the preliminary results, then scans of 92 patients with CAD; 64 males and 28 females, age 41 to 77 years old, who had been reported earlier reprocessed with the nominated filter and were reported by 2 NM expert. The results compared to the earlier reports and to the CT-Angio and angiography.The optimization suggested 3 filters; Wiener (Wi), Metz and Butterworth (But) provide the highest contrast (99- 66.4%) and (81- 32%) for the cold and hot inserts respectively, with the (Wi) filter to be the better option. The reprocessed patients scan with the (Wi) presented an elevated diagnostic accuracy, correlated well with the CT-Angio and angiography results (P 
    Matched MeSH terms: Tomography, Emission-Computed, Single-Photon/instrumentation*; Tomography, Emission-Computed, Single-Photon/methods; Single Photon Emission Computed Tomography Computed Tomography/methods; Single Photon Emission Computed Tomography Computed Tomography/statistics & numerical data; Computed Tomography Angiography*
  10. Rahmat MF, Isa MD, Rahim RA, Hussin TA
    Sensors (Basel), 2009;9(12):10291-308.
    PMID: 22303174 DOI: 10.3390/s91210291
    Electrical charge tomography (EChT) is a non-invasive imaging technique that is aimed to reconstruct the image of materials being conveyed based on data measured by an electrodynamics sensor installed around the pipe. Image reconstruction in electrical charge tomography is vital and has not been widely studied before. Three methods have been introduced before, namely the linear back projection method, the filtered back projection method and the least square method. These methods normally face ill-posed problems and their solutions are unstable and inaccurate. In order to ensure the stability and accuracy, a special solution should be applied to obtain a meaningful image reconstruction result. In this paper, a new image reconstruction method - Least squares with regularization (LSR) will be introduced to reconstruct the image of material in a gravity mode conveyor pipeline for electrical charge tomography. Numerical analysis results based on simulation data indicated that this algorithm efficiently overcomes the numerical instability. The results show that the accuracy of the reconstruction images obtained using the proposed algorithm was enhanced and similar to the image captured by a CCD Camera. As a result, an efficient method for electrical charge tomography image reconstruction has been introduced.
    Matched MeSH terms: Tomography; Tomography, X-Ray Computed
  11. Abu Bakar N, Lee CL
    Med J Malaysia, 2013;68(1):73-5.
    PMID: 23466774
    Osteo-odontokeratoprosthesis (OOKP) surgery is a technique used to replace damaged cornea in blind patients for whom cadaveric transplantation is not feasible. OOKP surgery is a complex procedure requiring lifetime follow-up. The preservation of the osteo-odontolamina is the vital feature in maintaining the stability of the OOKP. Early detection of lamina resorption enables early prophylactic measures to be taken and prevent resorption-related complications. This case illustrates the radiological findings of the first OOKP surgery in Malaysia and the role of multidetector computed tomography (MDCT) in postoperative management of OOKP surgery.
    Matched MeSH terms: Multidetector Computed Tomography*
  12. Robson RE, Brunger MJ, Buckman SJ, Garcia G, Petrović ZLj, White RD
    Sci Rep, 2015 Aug 06;5:12674.
    PMID: 26246002 DOI: 10.1038/srep12674
    The kinetic theory of non-relativistic positrons in an idealized positron emission tomography PET environment is developed by solving the Boltzmann equation, allowing for coherent and incoherent elastic, inelastic, ionizing and annihilating collisions through positronium formation. An analytic expression is obtained for the positronium formation rate, as a function of distance from a spherical source, in terms of the solutions of the general kinetic eigenvalue problem. Numerical estimates of the positron range - a fundamental limitation on the accuracy of PET, are given for positrons in a model of liquid water, a surrogate for human tissue. Comparisons are made with the 'gas-phase' assumption used in current models in which coherent scattering is suppressed. Our results show that this assumption leads to an error of the order of a factor of approximately 2, emphasizing the need to accurately account for the structure of the medium in PET simulations.
    Matched MeSH terms: Positron-Emission Tomography/methods*
  13. Hassan HA, Nazri M, Azman RR
    World J Nucl Med, 2012 May;11(2):81-3.
    PMID: 23372443 DOI: 10.4103/1450-1147.103421
    Technetium (99mTc) exametazime (hexamethylpropyleneamine oxime, HMPAO) labeled leukocyte scintigraphy is mainly used to exclude occult infection in our institution. On review of previously published article, no case of popliteal venous aneurysm was ever diagnosed and detected on labeled leukocyte scintigraphy. We present a rare case of popliteal venous aneurysm which was detected on labeled leukocyte scintigraphy and was further confirmed with single-photon emission computed tomography and computed tomography fusion.
    Matched MeSH terms: Tomography, X-Ray Computed; Tomography, Emission-Computed, Single-Photon
  14. Gill MK, Vijayananthan A, Kumar G, Jayarani K, Ng KH, Sun Z
    Quant Imaging Med Surg, 2015 Aug;5(4):524-33.
    PMID: 26435916 DOI: 10.3978/j.issn.2223-4292.2015.04.04
    To determine the effective radiation dose and image quality resulting from 100 versus 120 kilovoltage (kV) protocols among patients referred for computed tomography pulmonary angiography (CTPA).
    Matched MeSH terms: Tomography, X-Ray Computed; Computed Tomography Angiography
  15. Abdul Rahim, R., Pang, J.F., Chan, K.S., Leong, L.C., Fazalul Rahiman, M.H.
    ASM Science Journal, 2007;1(1):27-36.
    MyJurnal
    In this study, real-time imaging was monitored for flowing solid particles when various baffles were created to block certain areas of the pipe. The generated flow regimes were full-flow, three-quarter-flow, half-flow and quarter-flow. A vertical pneumatic conveyor was designed to hold a 85 mm inner diameter pipeline. The four projection optical tomography systems used, applied the parallel beam projection approach and use infrared light sources so that the sensor was free of noise from the surrounding visible light source. The two orthogonal and two rectilinear projections were axial, but ideally they should have been in the same layer. The sensor readings could be related to the varying light intensity effects of the dropping particles and were used to provide cross-sectional distribution information for the conveyor. By using computer programming, the information was reconstructed to produce coloured images and concentration was obtained by reference to a colour code. The results obtained from this study showed how imaged flow followed the artificial flow regime. This study could benefit industrial production lines in maintaining the desired flow rates.
    Matched MeSH terms: Tomography, X-Ray Computed; Tomography, Optical
  16. Moghbel M, Mashohor S, Mahmud R, Saripan MI
    EXCLI J, 2016;15:500-517.
    PMID: 28096782 DOI: 10.17179/excli2016-473
    Segmentation of the liver from Computed Tomography (CT) volumes plays an important role during the choice of treatment strategies for liver diseases. Despite lots of attention, liver segmentation remains a challenging task due to the lack of visible edges on most boundaries of the liver coupled with high variability of both intensity patterns and anatomical appearances with all these difficulties becoming more prominent in pathological livers. To achieve a more accurate segmentation, a random walker based framework is proposed that can segment contrast-enhanced livers CT images with great accuracy and speed. Based on the location of the right lung lobe, the liver dome is automatically detected thus eliminating the need for manual initialization. The computational requirements are further minimized utilizing rib-caged area segmentation, the liver is then extracted by utilizing random walker method. The proposed method was able to achieve one of the highest accuracies reported in the literature against a mixed healthy and pathological liver dataset compared to other segmentation methods with an overlap error of 4.47 % and dice similarity coefficient of 0.94 while it showed exceptional accuracy on segmenting the pathological livers with an overlap error of 5.95 % and dice similarity coefficient of 0.91.
    Matched MeSH terms: Tomography, X-Ray Computed; Cone-Beam Computed Tomography
  17. Mohamad Saberi FN, Sukumaran P, Ung NM, Liew YM
    Biomed Eng Online, 2022 Dec 03;21(1):83.
    PMID: 36463182 DOI: 10.1186/s12938-022-01055-x
    Tooth demineralization is one of the most common intraoral diseases, encompassing (1) caries caused by acid-producing bacteria and (2) erosion induced by acid of non-bacterial origin from intrinsic sources (e.g. stomach acid reflux) and extrinsic sources (e.g. carbonated drinks). Current clinical assessment based on visual-tactile examination and standardized scoring systems is insufficient for early detection. A combination of clinical examination and technology is therefore increasingly adapted. This paper reviews various procedures and technologies that have been invented to diagnose and assess the severity of tooth demineralization, with focus on optical coherence tomography (OCT). As a micron-resolution non-invasive 3D imaging modality, variants of OCT are now available, offering many advantages under different working principles for detailed analytical assessment of tooth demineralization. The roles, capabilities and impact of OCT against other state-of-the-art technologies in both clinical and research settings are described. (139 words).
    Matched MeSH terms: Tomography, Optical Coherence*
  18. Chiong E, Murphy DG, Buchan NC, Chua MLK, Hakim L, Hamid AR, et al.
    Asia Pac J Clin Oncol, 2022 Dec;18(6):686-695.
    PMID: 35134266 DOI: 10.1111/ajco.13722
    AIM: The second Asia-Pacific Advanced Prostate Cancer Consensus Conference (APAC APCCC 2020) gathered insights into the real-world application in the Asia-Pacific (APAC) region of consensus statements from the 3rd Advanced Prostate Cancer Consensus Conference (APCCC 2019).

    METHODS: The 4-h our virtual meeting in October 2020 brought together 26 experts from 14 APAC countries to discuss APCCC 2019 recommendations. Presentations were prerecorded and viewed prior to the meeting. A postmeeting survey gathered views on current practice.

    RESULTS: The meeting and survey highlighted several developments since APAC APCCC 2018. Increased access and use in the region of PSMA PET/CT imaging is providing additional diagnostic and staging information for advanced prostate cancer and influencing local and systemic therapy choices. Awareness of oligometastatic disease, although not clearly defined, is increasing. Novel androgen receptor pathway antagonists are expanding treatment options. Cost and access to contemporary treatments and technologies continue to be a significant factor influencing therapeutic decisions in the region. With treatment options increasing, multidisciplinary treatment planning, shared decision making, and informed choice remain critical. A discussion on the COVID-19 pandemic highlighted challenges for diagnosis, treatment, and clinical trials and new service delivery models that will continue beyond the pandemic.

    CONCLUSION: APAC-specific prostate cancer research and data are important to ensure that treatment guidelines and recommendations reflect local populations and resources. Facilitated approaches to collaboration across the region such as that achieved through APAC APCCC meetings continue to be a valuable mechanism to ensure the relevance of consensus guidelines within the region.

    Matched MeSH terms: Positron Emission Tomography Computed Tomography
  19. Zhang X, Dong X, Saripan MIB, Du D, Wu Y, Wang Z, et al.
    Thorac Cancer, 2023 Jul;14(19):1802-1811.
    PMID: 37183577 DOI: 10.1111/1759-7714.14924
    BACKGROUND: Radiomic diagnosis models generally consider only a single dimension of information, leading to limitations in their diagnostic accuracy and reliability. The integration of multiple dimensions of information into the deep learning model have the potential to improve its diagnostic capabilities. The purpose of study was to evaluate the performance of deep learning model in distinguishing tuberculosis (TB) nodules and lung cancer (LC) based on deep learning features, radiomic features, and clinical information.

    METHODS: Positron emission tomography (PET) and computed tomography (CT) image data from 97 patients with LC and 77 patients with TB nodules were collected. One hundred radiomic features were extracted from both PET and CT imaging using the pyradiomics platform, and 2048 deep learning features were obtained through a residual neural network approach. Four models included traditional machine learning model with radiomic features as input (traditional radiomics), a deep learning model with separate input of image features (deep convolutional neural networks [DCNN]), a deep learning model with two inputs of radiomic features and deep learning features (radiomics-DCNN) and a deep learning model with inputs of radiomic features and deep learning features and clinical information (integrated model). The models were evaluated using area under the curve (AUC), sensitivity, accuracy, specificity, and F1-score metrics.

    RESULTS: The results of the classification of TB nodules and LC showed that the integrated model achieved an AUC of 0.84 (0.82-0.88), sensitivity of 0.85 (0.80-0.88), and specificity of 0.84 (0.83-0.87), performing better than the other models.

    CONCLUSION: The integrated model was found to be the best classification model in the diagnosis of TB nodules and solid LC.

    Matched MeSH terms: Positron Emission Tomography Computed Tomography
  20. Saberi FNM, Liew YM, Sukumaran P, Ung NM
    Photodiagnosis Photodyn Ther, 2023 Sep;43:103715.
    PMID: 37481146 DOI: 10.1016/j.pdpdt.2023.103715
    Head and neck cancer patients are prone to dental caries after radiotherapy. An ex-vivo study was conducted to assess the feasibility of optical coherence tomography (OCT) to detect tooth demineralization due to caries in irradiated teeth. Thirty-nine human molar teeth were subjected to caries lesion induction through irradiation (Group 1), pH cycling (Group 2-1), and both (Group 2-2). The OCT signal attenuation coefficient, µR was assessed and validated against microhardness test and scanning electron microscope (SEM). The µR for Group 1 increased from 10 Gy to 40 Gy, and subsequently decreased after irradiated to 50 Gy and 60 Gy due to damaged enamel microstructure. In Group 2-1, the µR decreased with duration of pH cycling from day 1 to day 14 due to the increase of porosity in enamel layer. However, the µR showed decreasing trend from day 14 to day 28 of pH cycling, resulted from mineral deposition in the enamel layer. Although no significant difference was found in the µR between Group 2-1 and 2-2, SEM of Group 2-2 demonstrated visually higher porosity and larger gaps between microstructures. Irradiation may accelerate caries damage to tooth microstructure by increasing its porosity and brittleness, but larger sample size may be needed to further prove the effect. OCT could potentially be used for early detection of tooth demineralization in vivo based on the measurable µR changes for all groups which are shown negatively correlated with microhardness value (p 
    Matched MeSH terms: Tomography, Optical Coherence/methods
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