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Background: Photon-counting computed tomography (PCCT) is an emerging technique under evaluation for temporal bone imaging. Its capacity for radiation dose reduction while maintaining diagnostic image quality (IQ) requires further study.

Purpose: To evaluate how PCCT compares to energy-integrating CT (EICT) in temporal bone imaging in terms of IQ and visualization of anatomical landmarks, at a clinically relevant, reduced radiation dose.

Material and Methods: An anthropomorphic phantom with exchangeable fresh frozen human temporal bone specimens was scanned. Nine specimens were scanned on a PCCT system with clinical protocol settings, followed by stepwise dose reductions for one specimen. Ten specimens were scanned on a EICT system with clinical protocol settings. Three readers assessed overall IQ and visualization of 10 important anatomical landmarks on a 4-point scale.

Results: PCCT was preferred by readers for most landmarks and ranked higher in overall IQ compared with EICT. At clinical protocol, PCCT provided statistically significant better results for all landmarks and overall IQ compared to EICT with dose reduction of almost 70%. With stepwise dose reduction PCCT maintained good to excellent IQ for most landmarks, suboptimal for the ossicular chain landmarks at lower doses, and overall poor image quality at the lowest dose level. PCCT at clinical and several reduced dose levels demonstrated statistically significant difference in overall image quality and visualization of landmarks, compared to EICT (P <0.05).

Conclusion: PCCT provides improved diagnostic image quality compared to EICT at clinical protocols, with lowered radiation dose, indicating its suitability for temporal bone imaging.

Ultra-porous TiO₂ scaffolds are architected non-degradable ceramic graft substitutes, but human evidence relating their structural integration to local tissue maturation remains limited. This exploratory study assessed scaffold-associated healing in a prospective clinical cohort registered at ClinicalTrials.gov (NCT06269497; 10 patients, 11 treated sites). Cone-beam computed tomography (CBCT)-based segmentation at baseline and follow-up was used to quantify changes in bone volume, radiographic low-density/non-mineralized volume, and radiographically detectable scaffold volume. Eleven scaffold-associated specimens were examined using non-decalcified histology, histomorphometry, and immunohistochemistry; nine were retrieved at approximately 6 months, one at 4 months, and one at 9 months. CBCT showed within-site increases in bone and total tissue volume and a reduction in radiographically detectable scaffold volume. Histology showed extensive pore colonization by osteoid-rich tissue, localized mineralization, and limited residual cartilage, consistent with ongoing but incomplete matrix maturation. Normalized RunX2 showed a positive exploratory association with absolute bone volume change, whereas associations with osteocalcin were uncertain and endpoint-dependent. CD206/CD68 and the vessel-to-osteoid ratio were more closely associated with low-density/non-mineralized volume outcomes than with bone-volume change. Osteoclast-associated variables were evaluable in only four sites and were interpreted descriptively. These findings are exploratory and do not establish causality or comparative efficacy, but they characterize tissue-scaffold interactions during human extraction-socket healing. Statement of significance Permanent, highly porous scaffolds are intended to guide tissue growth without being replaced, but human evidence linking scaffold architecture to tissue maturation remains limited. This study combines serial cone-beam computed tomography (CBCT), non-decalcified histology, histomorphometry, and immunohistochemistry to characterize tissue development within an ultra-porous TiO₂ scaffold placed in human extraction sockets. The findings show extensive pore colonization by osteoid-rich tissue containing vascular structures, with localized mineralization and spatially heterogeneous remodeling, immune, and Wnt-regulatory features. The analyses are exploratory and do not establish causality or comparative efficacy; however, they provide human tissue-level data on how a permanent architected ceramic scaffold coexists with regenerating bone. This work supports biomaterials-focused evaluation of scaffold-guided regeneration and informs the design of larger controlled studies.

Accurate forensic age estimation is critical in legal contexts where documentation is unavailable. The Third Molar Maturity Index (I3M) is a quantitative, reproducible method based on the ratio of the open apical width to the length of the mandibular third molar. This multicentre, cross-sectional study evaluated I3M performance for age-threshold classification at 18 years across five populations. A total of 3000 orthopantomograms from individuals aged 13–22 years were collected in Brazil, China, Croatia, Portugal and Sweden. Teeth 38 and 48 were measured, and binary classification (≥ 18 vs. <18 years) was assessed using ROC analysis, hierarchical logistic regression with likelihood ratio testing, and machine learning with leave-one-population-out (LOPO) validation. I3M showed excellent discriminatory performance in all five populations (AUC: 0.917–0.942 for tooth 38). Inter-population differences in I3M distributions were significant; population was an independent predictor of 18-year-old classification. Intra-population sex differences were significant in three populations, with females showing higher I3M values. Optimal cut-off values varied from 0.126 (Croatia) to 0.223 (China). LOPO validation confirmed robust cross-population generalisability (AUC: 0.917–0.958). I3M is a reliable age classification tool across diverse ethnic groups. Population-specific thresholds are recommended when ethnic background is known; when unknown, a conservative threshold of 0.10–0.15 is advised to minimise misclassification of minors.

To develop a modular anthropomorphic phantom to evaluate the performance of radiological techniques for detecting pathologies in the temporal bone region. A phantom was constructed using a human skull, temporal bone specimen, and 3D-printed contour of a human skull. The human skull was embedded in tissue-equivalent plastic, with a cavity to hold the plastic jars containing the exchangeable freshly frozen human temporal bones. Subsequently, stepwise introduction and examination of different clinicopathological scenarios were conducted. Radiological images were nearly identical to those acquired from patients using computed tomography (CT) and cone beam computed tomography (CBCT). The radiological attenuation of polyurethane plastic (PUR) and alginate were similar to those of the soft tissues of living human patients. The mean Hounsfield unit values of the CT slices representing tissue at the brain and temporal bone level were 184 and 171 in the phantom and patient groups, respectively. The modular phantom developed in this study can evaluate radiological techniques and diagnostic possibilities without exposing patients to radiation. To our knowledge, no such modular phantom has been reported in the literature or made available commercially.

Background: In the field of otorhinolaryngology, the paranasal sinuses and the middle and inner ear present a clinical challenge. Radiological methods offer a stable foundation for diagnostics and preoperative decisions in this context. While many studies have explored the prevalence of maxillary sinusitis of dental origin (MSDO), the use of MSDO detected on cone beam computed tomography (CBCT) scans, rather than conventional computed tomography (CT), is a relatively new approach to detect MSDO. CBCT, with its higher ability to assess bony details, is becoming a valuable tool in detecting MSDO. Photon-counting Computed Tomography (PCCT), a cutting-edge diagnostic imaging method, enables radiological examinations with high spatial resolution at a low radiation dose compared with conventional CT. However, the question of how much the dose can be reduced while maintaining still diagnostic value in radiological examinations remains unanswered.

Aims: This thesis aimed to further develop the use of radiology in the ear, nose and throat (ENT) medical field, which could impact how we interpret radiological findings to obtain useful clinical information. The objectives for this thesis were as follows: 1) to investigate the proportion of MSDO among patients with suspected sinusitis referred for radiological examination; 2) to compare the symptomatology of MSDO with sinusitis due to upper respiratory tract infection (URTI); 3) to develop a modular anthropomorphic phantom that could be used to evaluate the performance of radiological techniques in detecting pathology in the temporal bone (TB) region; and 4) to investigate whether the diagnostic quality of TB imaging is maintained even at significantly lower radiation doses using PCCT compared to conventional energy integrated computed tomography (EICT).

Material and methods: Paper I was a retrospective study in which our research team reviewed 303 CBCT sinus examinations and analysed the data to determine the prevalence of MSDO among patients with suspected sinusitis who had been referred for radiological examination.A retrospective study was conducted in Paper II, in which the medical records from 61 patients with maxillary sinusitis confirmed via CBCT were thoroughly reviewed. Two independent observers reviewed all cases; when the observers disagreed, the examinations were re-reviewed to reach a consensus, ensuring the reliability of the findings. For comparison, the patients were divided into MSDO and URTI sinusitis groups. Information including self-reported symptoms, clinical findings, and time between first medical contact to correct diagnosis were collected and compared between the groups, providing a comprehensive understanding of the differences between the two conditions.

In Paper III, a modular anthropomorphic phantom was constructed. '

To evaluate anatomical structures and image quality, the phantom was used in paper IV to scan 10 human TB specimens using PCCT and conventional CT systems.

Results: In paper I, we found that the prevalence of unilateral MSDO was 40 %. Maxillary sinus mucosal swelling adjacent to periapical destruction was found in 91 % of the studied patients.

In paper II, we found that the MSDO patients reported a foul odour and foul taste more often, and the time from their first symptom to the correct diagnosis was significantly longer. The URTI sinusitis patients reported toothache, bilateral facial pain, and symptoms associated with a cold more often than the MSDO patients. The accuracy of CBCT for detecting MSDO was 97%.

In paper III, we found that the radiological attenuation of the polyurethane (PUR) plastic and alginate plastic used for the phantom was similar to those of the soft tissues of a living human. The mean Hounsfield unit (HU) values of the CT slices representing tissue at the TB and brain level were comparable in the phantom and patient groups.

In paper IV, we found that reviewers preferred PCCT scans for the majority of structures being evaluated and for overall image quality. This was true even at a radiation dose below 15 % of that in the clinical EICT protocol.

Conclusion: The close relationship between dental infections and unilateral sinusitis should not be overlooked. MSDO differs from URTI sinusitis regarding symptoms and clinical findings, and should be suspected in patients with unilateral symptoms presenting little pain and experiencing a foul odour and/or foul taste. CBCT is a reliable method of detecting MSDO. The modular phantom developed in the third study can be used to evaluate examination methods in a set-up corresponding to a living human without exposing patients to radiation. Finally, PCCT was found to be superior to EICT in terms of image quality. 

Objectives: To compare the symptomatology of patients with maxillary sinusitis of dental origin (MSDO) with sinusitis due to upper respiratory tract infection (URTI) with a special focus on time to correct diagnosis. To define the accuracy of cone beam computed tomography (CBCT) in detecting the dental origin of the sinusitis.

Methods: Retrospective review of the otolaryngology specialist care, primary health care and dental health care medical records of patients with maxillary sinusitis who has been referred for radiology. All patients were examined by CBCT, which has a better resolution regarding bony structures than low-dose computed tomography. To the best of our knowledge there is no previous study on this topic based on CBCT as diagnostic method.

Results: Sixty-one patients were included in the study; of these, 25 had MSDO and 36 had URTI sinusitis. The MSDO patients more frequently reported foul odour and foul taste than patients with URTI sinusitis. The URTI sinusitis patients more frequently reported symptoms such as facial pain, facial congestion and cold-related symptoms. Both the time from the onset of symptoms to the first medical visit and the subsequent time to a correct diagnosis were significantly longer in the MSDO group. The accuracy of CBCT for detecting dental pathology as the underlying cause of sinusitis was 97%.

Conclusion: The present study verifies that maxillary sinusitis of dental origin differs from viral-induced rhinosinusitis concerning symptomatology and clinical findings. Certain findings and symptoms could serve as valuable indicators of an underlying dental pathology, because although MSDO is well known, the present study shows that these patients are often misdiagnosed and the correct diagnose and treatment is often delayed several months. Consequently, better assessment is important. The suspicion of MSDO should be raised for patients with unilateral sinusitis presenting little pain, foul odour or foul taste and a long time course. These patients should be referred for radiology, preferably CBCT, to rule out odontogenic cause. CBCT is easy to perform for sinusitis examinations and has advances to common CT, especially regarding detection of pathology in bony structures as the periapical area. Because of this CBCT is a reliable tool in order to detect maxillary sinusitis of dental origin.

Objectives: This study sought to investigate the proportion of patients with suspected sinusitis referred for radiological examination who have radiologically verified sinusitis of odontogenic origin and to describe this type of sinusitis. Study Design: This investigation is a retrospective study. Methods: A total of 303 sinus examinations involving cone beam computed tomography (CBCT) performed at Sunderby Hospital, Lulea, Sweden in 2012 were independently reviewed by two radiologists. The number of cases of maxillary sinusitis and the correlation between maxillary sinusitis and odontogenic infections were determined. Results: Overall, 24% of the verified cases of sinusitis were odontogenic. An odontogenic origin was identified in 40% of unilateral maxillary sinusitis cases but only 6% of bilateral maxillary sinusitis cases (p=0.0015). Forty-nine out of 54 patients with periapical destruction had adjacent mucosal swelling in the maxillary sinus, but only 15 of these patients satisfied the criteria for sinusitis. Conclusion: The present study confirms the close relationship between odontogenic infections and unilateral maxillary sinusitis.