{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,28]],"date-time":"2026-02-28T04:27:56Z","timestamp":1772252876675,"version":"3.50.1"},"reference-count":27,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2022,4,12]],"date-time":"2022-04-12T00:00:00Z","timestamp":1649721600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"North Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, and through the European Regional Development Fund (ERDF)","award":["NORTE-01-0247-FEDER-033275"],"award-info":[{"award-number":["NORTE-01-0247-FEDER-033275"]}]},{"name":"European Regional Development Fund (ERDF), COMPETE2020 (Programa Operacional Competitividade e Internacionaliza\u00e7\u00e3o), Portugal 2020 and Portuguese Funds through Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","award":["POCI-01-0145-36 FEDER-029130"],"award-info":[{"award-number":["POCI-01-0145-36 FEDER-029130"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Long-term adherence to medication is of critical importance for the successful management of chronic diseases. Objective tools to track oral medication adherence are either lacking, expensive, difficult to access, or require additional equipment. To improve medication adherence, cheap and easily accessible objective tools able to track compliance levels are necessary. A tool to monitor pill intake that can be implemented in mobile health solutions without the need for additional devices was developed. We propose a pill intake detection tool that uses digital image processing to analyze images of a blister to detect the presence of pills. The tool uses the Circular Hough Transform as a feature extraction technique and is therefore primarily useful for the detection of pills with a round shape. This pill detection tool is composed of two steps. First, the registration of a full blister and storing of reference values in a local database. Second, the detection and classification of taken and remaining pills in similar blisters, to determine the actual number of untaken pills. In the registration of round pills in full blisters, 100% of pills in gray blisters or blisters with a transparent cover were successfully detected. In the counting of untaken pills in partially opened blisters, 95.2% of remaining and 95.1% of taken pills were detected in gray blisters, while 88.2% of remaining and 80.8% of taken pills were detected in blisters with a transparent cover. The proposed tool provides promising results for the detection of round pills. However, the classification of taken and remaining pills needs to be further improved, in particular for the detection of pills with non-oval shapes.<\/jats:p>","DOI":"10.3390\/s22082958","type":"journal-article","created":{"date-parts":[[2022,4,12]],"date-time":"2022-04-12T22:48:45Z","timestamp":1649803725000},"page":"2958","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":11,"title":["Development and Validation of a Digital Image Processing-Based Pill Detection Tool for an Oral Medication Self-Monitoring System"],"prefix":"10.3390","volume":"22","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-9696-9371","authenticated-orcid":false,"given":"Jannis","family":"Holtk\u00f6tter","sequence":"first","affiliation":[{"name":"MEDCIDS\u2014Department of Community Medicine, Health Informatics and Decision, Faculty of Medicine, University of Porto, 4200-450 Porto, Portugal"},{"name":"CINTESIS\u2014Center for Health Technology and Services Research, Faculty of Medicine, University of Porto, 4200-450 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0233-830X","authenticated-orcid":false,"given":"Rita","family":"Amaral","sequence":"additional","affiliation":[{"name":"MEDCIDS\u2014Department of Community Medicine, Health Informatics and Decision, Faculty of Medicine, University of Porto, 4200-450 Porto, Portugal"},{"name":"CINTESIS\u2014Center for Health Technology and Services Research, Faculty of Medicine, University of Porto, 4200-450 Porto, Portugal"},{"name":"Department of Cardiovascular and Respiratory Sciences, Porto Health School, 4200-072 Porto, Portugal"},{"name":"Department of Women\u2019s and Children\u2019s Health, Paediatric Research, Uppsala University, SE-751 85 Uppsala, Sweden"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7755-5002","authenticated-orcid":false,"given":"Rute","family":"Almeida","sequence":"additional","affiliation":[{"name":"MEDCIDS\u2014Department of Community Medicine, Health Informatics and Decision, Faculty of Medicine, University of Porto, 4200-450 Porto, Portugal"},{"name":"CINTESIS\u2014Center for Health Technology and Services Research, Faculty of Medicine, University of Porto, 4200-450 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1151-8791","authenticated-orcid":false,"given":"Cristina","family":"J\u00e1come","sequence":"additional","affiliation":[{"name":"MEDCIDS\u2014Department of Community Medicine, Health Informatics and Decision, Faculty of Medicine, University of Porto, 4200-450 Porto, Portugal"},{"name":"CINTESIS\u2014Center for Health Technology and Services Research, Faculty of Medicine, University of Porto, 4200-450 Porto, Portugal"}]},{"given":"Ricardo","family":"Cardoso","sequence":"additional","affiliation":[{"name":"MEDIDA\u2014Servi\u00e7os em Medicina, Educa\u00e7\u00e3o, Investiga\u00e7\u00e3o, Desenvolvimento e Avalia\u00e7\u00e3o, LDA, 4200-386 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5468-0932","authenticated-orcid":false,"given":"Ana","family":"Pereira","sequence":"additional","affiliation":[{"name":"MEDCIDS\u2014Department of Community Medicine, Health Informatics and Decision, Faculty of Medicine, University of Porto, 4200-450 Porto, Portugal"},{"name":"CINTESIS\u2014Center for Health Technology and Services Research, Faculty of Medicine, University of Porto, 4200-450 Porto, Portugal"}]},{"given":"Mariana","family":"Pereira","sequence":"additional","affiliation":[{"name":"MEDCIDS\u2014Department of Community Medicine, Health Informatics and Decision, Faculty of Medicine, University of Porto, 4200-450 Porto, Portugal"},{"name":"CINTESIS\u2014Center for Health Technology and Services Research, Faculty of Medicine, University of Porto, 4200-450 Porto, Portugal"},{"name":"MEDIDA\u2014Servi\u00e7os em Medicina, Educa\u00e7\u00e3o, Investiga\u00e7\u00e3o, Desenvolvimento e Avalia\u00e7\u00e3o, LDA, 4200-386 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4422-4837","authenticated-orcid":false,"given":"Ki H.","family":"Chon","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, University of Connecticut, Storrs, CT 06269, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0887-8796","authenticated-orcid":false,"given":"Jo\u00e3o Almeida","family":"Fonseca","sequence":"additional","affiliation":[{"name":"MEDCIDS\u2014Department of Community Medicine, Health Informatics and Decision, Faculty of Medicine, University of Porto, 4200-450 Porto, Portugal"},{"name":"CINTESIS\u2014Center for Health Technology and Services Research, Faculty of Medicine, University of Porto, 4200-450 Porto, Portugal"},{"name":"MEDIDA\u2014Servi\u00e7os em Medicina, Educa\u00e7\u00e3o, Investiga\u00e7\u00e3o, Desenvolvimento e Avalia\u00e7\u00e3o, LDA, 4200-386 Porto, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2022,4,12]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1091","DOI":"10.1080\/17474124.2021.1898944","article-title":"Patients with inflammatory bowel disease (IBD) prefer oral tablets over other modes of medicine administration","volume":"15","author":"Denesh","year":"2021","journal-title":"Expert Rev. Gastroenterol. Hepatol."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"581","DOI":"10.1016\/j.clinthera.2011.04.020","article-title":"A Pharmacoepidemiologic Analysis of the Impact of Calendar Packaging on Adherence to Self-Administered Medications for Long-Term Use","volume":"33","author":"Zedler","year":"2011","journal-title":"Clin. Ther."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"62","DOI":"10.1016\/j.clinthera.2011.02.003","article-title":"Does Packaging with a Calendar Feature Improve Adherence to Self-Administered Medication for Long-Term Use? A Systematic Review","volume":"33","author":"Bzedler","year":"2011","journal-title":"Clin. Ther."},{"key":"ref_4","unstructured":"Sabate, E. (2003). Adherence to Long-Term Therapies: Evidence for Action, World Health Organization."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1701836","DOI":"10.1183\/13993003.01836-2017","article-title":"Nonadherence in the era of severe asthma biologics and thermoplasty","volume":"51","author":"Lee","year":"2018","journal-title":"Eur. Respir. J."},{"key":"ref_6","unstructured":"Kreys, E. (2020, December 01). Measurements of Medication Adherence: In Search of a Gold Standard. Available online: https:\/\/www.journalofclinicalpathways.com\/article\/measurements-medication-adherence-search-gold-standard."},{"key":"ref_7","first-page":"550","article-title":"Effectiveness of Mobile Applications on Medication Adherence in Adults with Chronic Diseases: A Systematic Review and Meta-Analysis","volume":"26","author":"Peng","year":"2020","journal-title":"J. Manag. Care Sp\u00e9c. Pharm."},{"key":"ref_8","first-page":"117","article-title":"An overview of the common methods used to measure treatment adherence","volume":"92","author":"Anghel","year":"2019","journal-title":"Med. Pharm. Rep."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"e380","DOI":"10.1097\/01.hjh.0000748952.19902.f5","article-title":"Development of A Mobile Health App For The Management Of Hypertension, Including Treatment Adherence Assessment, Using Image Detection Technology\u2013Inspirers-Htn","volume":"39","author":"Valente","year":"2021","journal-title":"J. Hypertens."},{"key":"ref_10","unstructured":"Almeida, R., J\u00e1come, C., Martinho, D., Vieira-Marques, P., Jacinto, T., Ferreira, A., Almeida, A., Martins, C., Pereira, M., and Pereira, A. (2020, January 21\u201323). Airdoc: Smart Mobile Application For Individualized Support And Monitoring Of Respiratory Function And Sounds Of Patients With Chronic Obstructive Disease. Proceedings of the 12th International Conference on e-Health (EH2020), online."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"e9","DOI":"10.1055\/s-0041-1726277","article-title":"InspirerMundi\u2014Remote Monitoring of Inhaled Medication Adherence through Objective Verification Based on Combined Image Processing Techniques","volume":"60","author":"Almeida","year":"2021","journal-title":"Methods Inf. Med."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Lee, Y.-B., Park, U., and Jain, A.K. (2010, January 23\u201326). PILL-ID: Matching and Retrieval of Drug Pill Imprint Images. Proceedings of the International Conference on Pattern Recognition, Istanbul, Turkey.","DOI":"10.1109\/ICPR.2010.645"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1523","DOI":"10.1016\/j.protcy.2014.10.174","article-title":"HelpmePills: A Mobile Pill Recognition Tool for Elderly Persons","volume":"16","author":"Cunha","year":"2014","journal-title":"Procedia Technol."},{"key":"ref_14","first-page":"13155","article-title":"Automatic recognition and verification of defective tablet blisters using entropy based filtering and histogram processing","volume":"10","author":"Nithusha","year":"2015","journal-title":"Int. J. Appl. Eng. Res."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Sudharshan, D.P., Ameen, S.A.H., and Baig, K. (2018, January 19\u201320). Dynamic detection of anomalies in pharmaceutical blisters using image processing. Proceedings of the 2nd International Conference on Inventive Systems and Control, ICISC 2018, Coimbatore, India.","DOI":"10.1109\/ICISC.2018.8398890"},{"key":"ref_16","first-page":"1582","article-title":"Efficient approach of detection and visualization of the damaged tablets","volume":"96","author":"Qasim","year":"2018","journal-title":"J. Theor. Appl. Inf. Technol"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"62","DOI":"10.1109\/TSMC.1979.4310076","article-title":"A threshold selection method from gray-level histograms","volume":"9","author":"Otsu","year":"1979","journal-title":"IEEE Trans. Syst. Man Cybern."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"679","DOI":"10.1109\/TPAMI.1986.4767851","article-title":"A Computational Approach to Edge Detection","volume":"8","author":"Canny","year":"1986","journal-title":"IEEE Trans. Pattern Anal. Mach. Intell."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"690","DOI":"10.1109\/TPAMI.1987.4767964","article-title":"The Adaptive Hough Transform","volume":"9","author":"Illingworth","year":"1987","journal-title":"IEEE Trans. Pattern Anal. Mach. Intell."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"11","DOI":"10.1145\/361237.361242","article-title":"Use of the Hough transformation to detect lines and curves in pictures","volume":"15","author":"Duda","year":"1972","journal-title":"Commun. ACM"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"993","DOI":"10.1016\/j.patcog.2014.08.027","article-title":"A survey of Hough Transform","volume":"48","author":"Mukhopadhyay","year":"2015","journal-title":"Pattern Recognit."},{"key":"ref_22","first-page":"17","article-title":"A Visual Inspection System for Prescription Drugs","volume":"5","author":"Morimoto","year":"2013","journal-title":"Int. J. Intell. Comput. Med. Sci. Image Process."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"012029","DOI":"10.1088\/1742-6596\/1827\/1\/012029","article-title":"A Computer Vision System for Missing Tablets Detection","volume":"1827","author":"Zhao","year":"2021","journal-title":"J. Phys. Conf. Ser."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Berciu, A.G., Dulf, E.H., and Stefan, I.A. (2022). Flexible Augmented Reality-Based Health Solution for Medication Weight Establishment. Processes, 10.","DOI":"10.3390\/pr10020219"},{"key":"ref_25","first-page":"30","article-title":"Medication adherence: The elephant in the room","volume":"43","author":"Kim","year":"2018","journal-title":"U.S. Pharm."},{"key":"ref_26","first-page":"638","article-title":"Highlighted Deep Learning based Identification of Pharmaceutical Blister Packages","volume":"1","author":"Wang","year":"2018","journal-title":"IEE Xplore"},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Chung, S.L., Chen, C.F., Hsu, G.S., and Wu, S.T. (2019, January 18\u201321). Identification of partially occluded pharmaceutical blister packages. Proceedings of the 2019 16th IEEE International Conference on Advanced Video and Signal Based Surveillance (AVSS), Taipei, Taiwan.","DOI":"10.1109\/AVSS.2019.8909890"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/8\/2958\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T22:52:37Z","timestamp":1760136757000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/8\/2958"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,4,12]]},"references-count":27,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2022,4]]}},"alternative-id":["s22082958"],"URL":"https:\/\/doi.org\/10.3390\/s22082958","relation":{"has-preprint":[{"id-type":"doi","id":"10.20944\/preprints202202.0204.v1","asserted-by":"object"}]},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,4,12]]}}}