A comparison between low-dose and standard-dose non-contrasted multidetector CT scanning of the paranasal sinuses

Comparison of Low-Dose Non-contrast CT in Detecting Anatomical and Surgically Important Variants of Paranasal Sinuses to Standard Dose Non-contrast CT: Experience from a Tertiary Care Hospital in Sub-Himalayan Region of Northern India

Computed tomography (CT) is the gold standard for diagnosing sinusitis and anatomical variations and a guide for paranasal sinus (PNS) surgeries. High doses of radiation lead to increased risk of head and neck malignancies, radiation-induced cataracts, hypothyroidism, and hyperthyroidism. The purpose of this study was to assess the effectiveness of low-dose CT as compared to standard-dose CT in the identification of anatomical variants of paranasal sinus and rhinosinusitis. This was a prospective cross-sectional study consisting of 72 patients who were divided equally into cases (underwent low-dose CT for PNS) and controls (underwent CT for PNS using standard dose protocols). Prevalence of anatomical variants and sinusitis were compared. Image quality was assessed using volume CT dose index (CTDIvol), dose length product (DLP), scan length, and noise. Subjective assessment was done by two radiologists, and scores were given. The comparison and analysis of the quantitative and qualitative variables were done. Anatomical variants were comparable among cases and controls, with post-sellar sphenoid being most common and paradoxical middle turbinate being least common surgically important variant. The difference in mean SD of CTDIvol (mGy), DLP (mGy-cm), effective dose (mSv), globe, and air noise between low and standard doses was statistically significant. A moderate agreement (with kappa 0.50) in cases and substantial agreement (with kappa 0.69) in controls was observed between both observers. Low-dose CT PNS and standard-dose CT PNS are comparable in delineating the paranasal sinus anatomy, with a 3.53× reduction of effective radiation dose to patients.

Optimization of paranasal sinus CT procedure: Ultra-low dose CT as a roadmap for pre-functional endoscopic sinus surgery

OBJECTIVE

To assess image quality and radiation dose associated with ultra-low dose CT protocol for patients with benign paranasal sinus diseases undergoing functional endoscopic surgery (FESS).

METHODS

We scanned the head portion of Alderson RANDO phantom on a second generation, dual-source, multidetector-row CT scanner (Siemens Definition Flash) using standard-dose and five low-dose protocols. Two radiologists assessed the image quality for each protocol to determine best ultra-low-dose protocols for imaging patients with benign paranasal sinus diseases undergoing FESS. The ultra-low-dose CT protocols were then used for scanning. Thereafter, 40 adult patients (age range 18-54 years, M:F 23:17) were scanned with the four low dose scanning protocols (10 patients per protocol). On both transverse and coronal reformatted CT images, two radiologists assessed visibility of key anatomic landmarks for FESS on a 2-point scale (1 = clear and complete visualization; 2 = suboptimal visualization). Data were analyzed with descriptive statistics and Cohen's kappa coefficient for interobserver agreement.

RESULTS

In phantom study, the lowest dose scan protocol (CTDI_vol 2.1 mGy, 70 kV, 75 mAs) was unacceptable due to poor image quality. For patient studies, both radiologists gave acceptable image quality scores for ultra-low-dose scan protocol with axial scan mode, automatic tube potential selection and tube current modulation (CTDI_vol 2.2 mGy; DLP 22.9 mGy.cm) with up to 60% lower dose compared to prior standard-dose CT (CTDI_vol 5.3 mGy; DLP 73.5 mGy.cm).

CONCLUSIONS

Ultra-low-dose CT protocol provides sufficient image quality for scanning patients undergoing functional endoscopic surgery for benign paranasal sinus diseases.

Cone-beam computed tomography and its applications in dental and maxillofacial radiology

Cone-beam computed tomography (CBCT) was first used in dental and maxillofacial radiology (DMFR) at the end of the 1990s. Since then, it has been successfully established as the standard three-dimensional radiographic imaging technique in DMFR, with a wide variety of applications in this field. This manuscript briefly reviews the background information on the technology and summarises available data on effective dose and dose optimisation. In addition, typical clinical applications and indications of the technique in DMFR are presented.

Tin-filtered 100 kV ultra-low-dose CT of the paranasal sinus: Initial clinical results

Objectives

To investigate the feasibility, diagnostic image quality and radiation dose of 3^rd generation dual-source computed tomography (CT) using a tin-filtered 100 kV protocol in patients with suspected acute inflammatory sinus disease.

Methods

We retrospectively evaluated 109 consecutive patients who underwent CT (Siemens SOMATOM Force, Erlangen, Germany) of the paranasal sinus with a new tin-filtered scan-protocol (Sn100 kV; tube current 35 mAs) using iterative reconstruction. Two readers independently assessed subjective image quality using a five-point Likert scale (1 = excellent, 5 = non-diagnostic). Inter-observer agreement was calculated and expressed as percentage of agreement. Noise was determined for calculation of signal-to-noise-ratio (SNR). Effective radiation dose (ED) was calculated from the dose-length-product (DLP).

Results

All examinations showed diagnostic image quality regarding evaluation of inflammatory sinus disease. On average, subjective general image quality was rated moderate (= 3) with a percentage of agreement between the observers of 81%. The mean image noise was 14.3 HU. The calculated median SNR was 6.0 for intraorbital fat, and 3.6 for the vitreous body, respectively. The median DLP was 2.1 mGy*cm, resulting in a median ED of 0.012 mSv.

Conclusions

Taking the study limitations into account, ultra-low-dose tin-filtered CT of the paranasal sinus at a tube voltage of 100 kV utilizing an iterative reconstruction algorithm provides for reliable exclusion of suspected acute inflammatory sinus disease in 100% of the cases.

Dose reduction in CT imaging for facial bone trauma in adults: A narrative literature review

Trauma to the facial area accounts for a significant number of admissions to the emergency department. Diagnostic imaging is almost always required, and is critical in determining patient management. Multi‐detector computed tomography (MDCT) appears consistently in the literature as the gold‐standard imaging modality for facial bones, but results in a high radiation dose to the patient. This makes the application and advancement of dose reduction and dose optimisation methods vital. This narrative review presents a critical analysis of the literature concerning diagnostic imaging of facial bone trauma, with an emphasis on dose reduction methods for MDCT. Databases including Pubmed, Medline, Web of Science and Scopus were used to investigate this topic, with the key words: facial bone trauma, computed tomography (CT) imaging and dose reduction. Exclusion criteria included studies on nasal bone fracturing, dental imaging, elective surgeries and paediatric imaging. The literature shows overwhelming support for MDCT, given its accuracy, efficiency and ease of operation. Noise reducing reconstruction algorithms show promise as a successful method of dose reduction in facial bone imaging. Investigations of more innovative techniques also appear within the literature, including diagnostic cone‐beam CT (CBCT), intraoperative CBCT and dual‐source CT (DSCT), but further research is required to confirm their clinical value.

Standard-dose versus low-dose multidetector computed tomography examinations in patients with uncontrolled chronic rhinosinusitis: A randomized, controlled trial

BACKGROUND

Multidetector computed tomography (MDCT) images for rhinosinusitis may have a risk of radiation hazards. Reduction in radiation dose may lead to a compromise in quality of MDCT images and have chances of postoperative complications.

OBJECTIVE

The aim of the study was to test the applicability of low-dose MDCT protocols for decision-making of sinus surgeries of patients with uncontrolled chronic rhinosinusitis.

DESIGN

Randomized, double-blind (patients and evaluators blind), controlled, trial.

SETTING

People's Hospital of Guanghan, China.

PATIENTS

A total of 288 patients with clinically confirmed uncontrolled chronic rhinosinusitis were subjected to randomization (1:1 ratio).

INTERVENTIONS

Patients were subjected to low-dose preoperative protocols of MDCT (n = 144; ldMDCT group) or standard-dose preoperative protocols of MDCT (n = 144; sdMDCT group).

OUTCOME MEASURES

Image analysis was performed by the workstation. Lund-Mackay score, modified Lund-Mackay score, estimated radiation exposure, and surgical complications were evaluated for each patient. The χ independent test or 2-tailed paired t test were performed for statistical analysis.

RESULTS

The preoperative MDCT images for standard-dose protocol had better quality than low-dose protocol (P < .001, q = 4.57). The area of images that give confidence for sinus surgery at one time was higher for standard-dose MDCT protocol technique than low-dose MDCT protocol method. Patients of ldMDCT group with large growth of nasal polyps (P = .03, q = 5.35) and complete opacification of sinuses (P = .03, q = 7.94) had complications after sinus surgeries. Either low-dose or standard-dose MDCT protocol was performed, the experience of otolaryngologist had decreased complication after surgeries.

CONCLUSION

Preoperative low-dose MDCT should be used for diagnosis of uncontrolled chronic rhinosinusitis for decision making of sinus surgeries.

LEVEL OF EVIDENCE

III.

TRIAL REGISTRATION

researchregistry4264 dated 1 March 2016 (www.researchregistry.com).

Application of a full model-based iterative reconstruction (MBIR) in 80 kVp ultra-low-dose paranasal sinus CT imaging of pediatric patients

OBJECTIVE

To evaluate the clinical application of a full model-based iterative reconstruction (MBIR) algorithm in the ultra-low-dose paranasal sinus CT imaging of children.

MATERIALS AND METHODS

In the first phase, 16 low-dose CT dacryocystography (DCG) (80 kV/64 mAs) scans were reconstructed with MBIR and filtered back-projection (FBP) to demonstrate noise reduction capability of MBIR. MBIR images were also compared with the images of 21 standard-dose paranasal sinus patients reconstructed with adaptive statistical iterative reconstruction (ASIR) algorithm. In the second phase, 14 pediatric tumors patients (images with ASIR in the initial scan) who came for follow-up paranasal sinus CT scan were prospectively enrolled with reduced radiation and MBIR algorithm. In both study phases, image noise and the contrast noise ratio (CNR) of sphenoid was measured; and subjective image quality was evaluated. CTDIvol and DLP were recorded, and effective dose calculated.

RESULTS

The CTDIvol value for the DCG group was 63.9% lower than the standard-dose sinus group (1.09 ± 0.01 mGy vs. 3.02 ± 0.35 mGy). Compared with the ASIR reconstruction in the standard-dose sinus patient group, images with MBIR in the ultra-low-dose DCG group had 39.9% lower noise (9.5 ± 0.8HU vs. 15.8 ± 3.3HU) and 63.6% higher CNR (14.4 ± 4.7 vs. 8.8 ± 2.2), with similar subjective image quality score. For the tumor patients, 65.5% dose reduction was achieved. Subjective quality scores were similar between the initial and follow-up scans. Objective noise was significantly lower for the follow-up group.

CONCLUSION

MBIR provided equal or better image quality with significantly reduced radiation dose in paranasal sinus CT imaging of pediatric patients compared with standard-dose CT with ASIR algorithm.

Detection of Dental Pathologies in Routine Paranasal CT Scans: A Retrospective Study

INTRODUCTION

Multidetector Computed Tomography (MDCT) is a widespread method for evaluating paranasal sinuses and nasal cavity in daily practice. The maxillary teeth are in field of view in a paranasal sinus CT scan and it is possible to detect dental pathologies with CT.

AIM

To determine the incidence of maxillary teeth pathologies in routine paranasal sinus CT scans.

MATERIALS AND METHODS

A retrospective study was conducted. Consecutive 395 paranasal sinus CT scans were evaluated. All CT images were obtained with a 64 detector-CT. Patients with previous facial trauma, operation, invasive tumors and repeated exams were excluded. Detected findings were classified as "tooth loss, dental restorations or procedures and dental pathologies (carious lesions, dental developmental anomalies, periapical lesions and periodontal diseases). The proportion of findings was reported as simple percentiles.

RESULTS

Three hundred and eighty-four CT scans were included in the study. Dental restorations or procedures were determined in 129 (33.5%) patients. A total of 34 (8.8%) patients had normal teeth count and morphology. A total of 264 (64.3%) patients had at least one tooth loss. A total of 195 (51%) patients had at least one or more dental pathology. Number of dental carious lesions, dental developmental anomalies, periapical lesions and periodontal disease were 104 (27.0%), 78 (14.3%), 46 (11.9%), 44 (11.4%), respectively.

CONCLUSION

Dental pathologies were encountered in more than half of the patients. Detecting dental pathologies may prevent tooth loss and improve oral health. The radiologist should keep in mind dental pathologies while evaluating paranasal sinus CT in daily practice.

Evaluation of different low-dose multidetector CT and cone beam CT protocols in maxillary sinus imaging: part I-an in vitro study

OBJECTIVES

This in vitro study aimed to assess radiation dose and image quality of different low-dose multidetector CT (MDCT) and CBCT imaging protocols in comparison with the standard MDCT protocol for maxillary sinus imaging.

METHODS

Effective dose (E) and image quality of 10 MDCT (changing effective milliampere second starting from 141.3 EmAs to 20 EmAs) and 3 CBCT protocols (changing milliampere second and voxel size) were assessed throughout scanning an anthropomorphic head and neck Alderson Rando phantom. E values were calculated using thermoluminescent dosemeters (TLDs) fixed at 6 sensitive organs (14 sites) on the Rando phantom. Image quality was assessed objectively (by calculating the standard deviation values of the radiographic density of water) and subjectively (by assessing the diagnostic image quality using a four-graded scale: 1 = very good, 2 = good, 3 = acceptable and 4 = unacceptable).

RESULTS

Two MDCT protocols (120 kV/32 EmA and 120 kV/25 EmA) had lower radiation doses with statistically significant differences (p < 0.001) compared with that of the standard MDCT protocol (120 kV/141.3 EmA), and they preserved a good diagnostic image quality. One CBCT protocol (120 kV/20 mA) had a reasonable radiation dose and good image quality. There were no statistically significant differences between the above-mentioned lower dose MDCT and CBCT protocols (p > 0.05) with respect to the radiation dose and image quality.

CONCLUSIONS

The low-dose MDCT and CBCT protocols are viable methods for maxillary sinus examination as evaluated using the above-mentioned phantom that yield a good diagnostic image quality using E approximately 7 and 11 times lower than that of the standard MDCT, respectively. These findings were evaluated in the in vivo part of this project.

Reduction of Radiation Dosage in Visualization of Paranasal Sinuses in Daily Routine

Background. Preoperative imaging of the nose and paranasal sinus is standard in otorhinolaryngology. Previous studies on phantoms demonstrated the potential for dose reduction of cone beam computed tomography (CBCT) by varying the application parameters. Methodology. Based on previous studies, the standard protocol of paranasal sinus imaging by CBCT was altered. One hundred and fifty examinations using the old protocol (01/2010–01/2011, high dosage) and 150 examinations using the new protocol (09/2012–09/2013, low dosage) were evaluated and compared for the visibility of 17 anatomical structures, the Lund-Mackay Score, and technical parameters. Results. Alteration of the protocol resulted in a significant reduction in dosage (6.64 mGy versus 2.88 mGy). Both groups showed the same amount of pathology (Lund-Mackay Score: 4.95 ± 3.79 versus 5.26 ± 5.77; p = 0.558). There was a significant better visibility of the anatomical structures (all visible = 1, nothing visible = 4) (results: 1.25 versus 1.17; p = 0.001) in the low-dosage group. Conclusion. Despite a significant reduction in the applied dosage, reliable visualization of the bony anatomy of the anterior skull base is possible by CBCT. This demonstrates the need for the discussion of the required clinical imaging quality.

Problem-based learning discussion: Medical treatment of pediatric chronic rhinosinusitis

This problem-based learning case focused on the approach to evaluation and management of a 5-year old girl who was "always sick" with sinus infections. The discussion unfolds in a "real life" scenario, i.e., based on information available to the clinician initially and after the acquisition of laboratory data, and, ultimately, after sinus surgery. Emphasis is placed on the differential diagnosis of the patient's symptoms, discussion of the initial management strategy for chronic rhinosinusitis (CRS), evolution from acute rhinosinusitis to CRS, the prevalence of and differential diagnosis of nasal polyps in children, treatment considerations specific for CRS with nasal polyps, the significance of Pseudomonas aeruginosa sinus infection, the significance of an abnormal sweat chloride test in a young child with nasal polyposis, special considerations in children with CRS who have cystic fibrosis, treatment considerations after endoscopic sinus surgery, and, finally, prognostic factors that impact the outcomes of endoscopic sinus surgery. This problem-based learning case highlights many facets of managing refractory CRS in children.

Nasal endoscopy: an adjunct to patient selection for preoperative low-dose CT examination in chronic rhinosinusitis

OBJECTIVES

The growing awareness of increased X-ray exposure to the public has led to the propagation of several methods for reducing the radiation dose during CT examination. Low-dose CT protocols do not, however, have an established role in pre-operative evaluation. The aim of this article was to assess the usefulness of nasal endoscopy in the selection of patients under pre-operative care for low-dose CT examination.

METHODS

A cadaver head was used to discover institutional minimum acceptable CT image quality and scanning settings. Then, 134 adult patients with chronic rhinosinusitis (CRS) were enrolled into the study and divided randomly into standard dose (120 kVp, 100 mAs) or low-dose CT groups (120 kVp, 45 mAs). Subjective assessment of the diagnostic image quality of the surgically relevant anatomical structures was compared using a five-point scale (from excellent to unacceptable) by a radiologist and sinus surgeon independently. Pathologic states of the nose were quantified according to the Lund-Kennedy endoscopic system (LKES) and Lildholdt's scale.

RESULTS

Image quality was similar in low-dose and standard dose groups in patients without polyps. The quality of 13% of scans from patients with polyps from the low-dose group and 4% from the standard dose group was in the range from moderate to poor. The quality of scans obtained with low milliamperes second (mAs) values worsened in patients with polyps in the middle meatus, but the difference was particularly pronounced compared with standard dose among subjects with Lildholdt's score above 2 (p < 0.001). Correlation with LKES revealed that changes other than polyps (i.e. discharge, oedema, scaring or crusting) in the nasal cavity alone do not affect the image quality. Interobserver agreement in both groups was very high.

CONCLUSIONS

Low-dose scanning should be promoted as the screening imaging method of choice in patients with suspected CRS. Furthermore, low mAs value examination can be performed pre-operatively without fear of significant image quality deterioration in uncomplicated CRS patients without polyps, or with minor changes in nasal endoscopy. Standard dose CT, which provides a better identification of bony landmarks, minimizes diagnostic errors and risk to patients, so it might be considered in those with polyps below the middle turbinate.

Pediatric chronic rhinosinusitis

The goal of this review is to elucidate the pathogenic factors, histopathologic features, and special considerations that relate to pediatric versus adult chronic rhinosinusitis (CRS) and to emphasize differences and similarities between the adult and pediatric conditions. Emphasis is placed on understanding of the differences in pathogenic mechanisms, host-microbial interactions, potential defects in innate antimicrobial immunity, and the role of biofilm formation in pediatric versus adult CRS and how these translate to different approaches toward both medical and surgical management. Pediatric CRS can be viewed as evolving from acute bacterial rhinosinusitis into an uncomplicated "early" stage of CRS, later evolving into a persistent stage and, in some cases, evolving into a late "maladaptive-eosinophilic" stage disease. Given this potential evolution toward more irreversible disease, a plea can be made for improved recognition of and more aggressive early intervention for pediatric CRS, it is hoped, to prevent these long-term consequences. For the primary care physician, this may necessitate enlisting the support of a sinus specialist before the symptoms of CRS have persisted for months or years. It may also necessitate, in some cases, the use of sinus computed tomography imaging to demonstrate that sinus abnormalities have resolved. Other arguments can be made for prompt and comprehensive management of pediatric CRS, including the need to reduce the burden of illness, reduce health care costs, avoid unnecessary antibiotic use and its attendant effects toward promoting antibiotic resistant infections and, potentially, to reduce the development of important comorbidities, e.g., asthma.

Radiation Dose Reduction in Paranasal Sinus CT: With Feasibility of Iterative Reconstruction Technique

OBJECTIVES

To (1) compare the radiation dose of low-dose computed tomography (CT) to that of standard-dose CT, (2) determine the minimum optimal radiation dose for use in patients who need endoscopic sinus surgery, and (3) assess the reliability of iterative model reconstruction.

STUDY DESIGN

Prospective single-institution study.

SETTING

Tertiary care center.

SUBJECTS AND METHODS

We recruited 48 adults with medically refractory sinusitis. Each patient underwent 4 scans with different CT parameters: 120 kV and 100 mAs (standard dose), 100 kV and 40 mAs (low dose), 100 kV and 20 mAs (very low dose), and 100 kV and 10 mAs (ultra-low dose). All CT scans were reconstructed via filtered back-projection, and ultra-low dose scans were additionally reconstructed through iterative model reconstruction. Radiation dose, image quality, and diagnostic performance were compared among the scans.

RESULTS

Radiation doses decreased to 6% (ultra-low dose), 12% (very low dose), and 22% (low dose) of the standard-dose CT. The image quality of low-dose CT was similar to that of standard-dose CT. Ultra-low-dose CT with iterative model reconstruction was inferior to standard-dose CT for identifying anatomic structures, except for the optic nerve. All CT scans had 100% agreement for diagnosing rhinosinusitis.

CONCLUSIONS

With low-dose CT, the radiation dose can be decreased to 22% of that of standard-dose CT without affecting the image quality. Low-dose CT can be considered the minimum optimal radiation for patients who need surgery. Iterative model reconstruction is not useful for assessing the anatomic details of the paranasal sinus on CT.

Investigation of sinonasal anatomy via low-dose multidetector CT examination in chronic rhinosinusitis patients with higher risk for perioperative complications

The aim of the study was to compare visualisation of the surgically relevant anatomical structures via low- and standard-dose multidetector CT protocol in patients with chronic rhinosinusitis (CRS) and higher risk for perioperative complications (i.e. presence of bronchial asthma, history of sinus surgery and advanced nasal polyposis). 135 adult CRS patients were divided randomly into standard-dose (120 kVp, 100 mAs) or low-dose CT groups (120 kVp, 45 mAs). The detectability of the vital anatomical structures (anterior ethmoid artery, optic nerve, cribriform plate and lamina papyracea) was scored using a five-point scale (from excellent to unacceptable) by a radiologist and sinus surgeon. Polyp sizes were quantified endoscopically according to the Lildholdt's scale (LS). Olfactory function was tested with the "Sniffin' Sticks" test. On the low-dose CT images, detectability ranged from 2.42 (better than poor) for cribriform plate among anosmic cases to 4.11 (better than good) for lamina papyracea in cases without nasal polyps. Identification of lamina papyracea on low-dose scans was significantly worse in each group and the same was the case with cribriform plates in patients with advanced polyposis and anosmia. Cribriform plates were the most poorly identified (between poor and average) among all the structures on low-dose images. Identification of anterior ethmoid artery (AEA) with reduced dose was insignificantly worse than with standard-dose examination. The AEA was scored as an average-defined structure and was the second weakest visualised. In conclusion, preoperatively, low-dose protocols may not sufficiently visualise the surgically relevant anatomical structures in patients with CRS and bronchial asthma, advanced nasal polyps (LS > 2) and history of sinus surgery. Low mAs value enables comparable detectability of sinonasal landmarks with standard-dose protocols in patients without analysed risk factors. In the context of planned surgery, the current preferences of the tube should be carefully evaluated for different patient constitutions to minimise the risk of complications.

Current Trends in Sinonasal Imaging

As endoscopic sinus surgery (ESS) has evolved since its introduction to the United States, so has technology for imaging the sinonasal cavities. Although imaging is most frequently performed for evaluating chronic sinusitis refractory to medical therapy, its uses have expanded beyond inflammatory sinus disease. Multidetector Computed Tomography is the current workhorse for both diagnosis and preoperative planning in prospective ESS patients, while MR imaging remains a complementary tool for evaluating suspected tumors or intracranial and orbital complications of rhinosinusitis. In this article, the authors review current trends and potential future directions in the use of these modalities for sinus imaging.

Reliability of high-pitch ultra-low-dose paranasal sinus computed tomography for evaluating paranasal sinus anatomy and sinus disease

OBJECTIVES

The aim of this study was to evaluate the reliability of high-pitch ultra-low-dose computed tomography (CT) for detecting important paranasal sinus anatomic landmarks and pathologies.

MATERIALS AND METHODS

Sixty patients (22 females, 38 males) aged 15 to 67 years (mean age, 33.68 y; SD, 9.83 y) underwent high-pitch ultra-low-dose CT of the paranasal sinuses between February and June 2012. To determine the lowest possible dose for evaluation of the paranasal sinuses, the patients were divided into three groups randomly and prospectively. A different low-dose CT protocol was applied to each group. The image quality was assessed subjectively by a radiologist and an otorhinolaryngology head and neck surgeon independently using a 4-point grading scale (0 = structures could not be identified, 1 = indistinctly defined structures, 1.5 = relatively well-defined structures, 2 = very well-defined structures). Anatomic landmarks and mucosal structures were evaluated. Mean scores were evaluated to assess statistical significance.

RESULTS

According to the anatomic landmark scoring, excluding the ethmoid foramen for ethmoid artery identification, all of the structures in all 3 groups were very well-defined structures. The ethmoid foramen for ethmoid artery identification was scored as either could not be identified or an indistinctly defined structure in all groups. On evaluating the mucosa of the paranasal sinuses, normal and pathologic mucosal structures were scored as very well defined in all of the patients. The interobserver agreement was excellent.

CONCLUSION

High-pitch ultra-low-dose CT is a safe, reliable paranasal sinus screening tool.

Seventy kilovolt ultra-low dose CT of the paranasal sinus: first clinical results

AIM

To evaluate the diagnostic image quality and radiation dose of low-dose 70 kV computed tomography (CT) of the paranasal sinus in comparison to 100 and 120 kV CT.

MATERIALS AND METHODS

CT of the paranasal sinus was performed in 127 patients divided into three groups using different tube voltages and currents (70 kV/75 mAs, ultra-low dose protocol, n = 44; 100 kV/40 mAs, standard low-dose protocol, n = 42; 120 kV/40 mAs, standard protocol, n = 41). CT dose index (CTDIvol), dose-length product (DLP), attenuation, image noise and signal-to-noise ratio (SNR) were compared between the groups using Wilcoxon-Mann-Whitney U-test. Subjective diagnostic image quality was compared by using a five-point scale (1 = non-diagnostic, 5 = excellent, read by two readers in consensus) and Cohen's weighted kappa analysis for interobserver agreement.

RESULTS

Radiation dose was significantly lower with 70 kV acquisition than 100 and 120 kV (DLP: 31 versus 52 versus 82 mGy·cm; CTDI 2.33 versus 3.95 versus 6.31 mGy, all p < 0.05). Mean SNR (70 kV: 0.37; 100 kV: 0.21; 120 kV: 0.13; p < 0.05) and organ attenuation increased significantly with lower voltages. All examinations showed diagnostic image quality. Subjective diagnostic image quality was higher with standard protocols than the 70 kV protocol (120 kV: 5.0; 100 kV: 4.5; 70 kV: 3.5, p < 0.05) without significant differences with substantial interobserver agreement (κ > 0.59).

CONCLUSION

The ultra-low dose (70 kV) CT imaging of the paranasal sinus allowed for significant dose reduction by 61% and an increased attenuation of organ structures in comparison to standard acquisition while maintaining diagnostic image quality with a slight reduction in subjective image quality.

Three-dimensional architectural and structural analysis--a transition in concept and design from Delaire's cephalometric analysis

The aim of this study was to present a systematic sequence for three-dimensional (3D) measurement and cephalometry, provide the norm data for computed tomography-based 3D architectural and structural cephalometric analysis, and validate the 3D data through comparison with Delaire's two-dimensional (2D) lateral cephalometric data for the same Korean adults. 2D and 3D cephalometric analyses were performed for 27 healthy subjects and the measurements of both analyses were then individually and comparatively analyzed. Essential diagnostic tools for 3D cephalometry with modified definitions of the points, planes, and measurements were set up based on a review of the conceptual differences between two and three dimensions. Some 2D and 3D analysis results were similar, though significant differences were found with regard to craniofacial angle (C1-F1), incisal axis angles, cranial base length (C2), and cranial height (C3). The discrepancy in C2 and C3 appeared to be directly related to the magnification of 2D cephalometric images. Considering measurement discrepancies between 2D and 3D Delaire's analyses due to differences in concept and design, 3D architectural and structural analysis needs to be conducted based on norms and a sound 3D basis for the sake of its accurate application and widespread adoption.

Radiation dose reduction in paranasal sinus CT using model-based iterative reconstruction

BACKGROUND AND PURPOSE

CT performed with Veo model-based iterative reconstruction has shown the potential for radiation-dose reduction. This study sought to determine whether Veo could reduce noise and improve the image quality of low-dose sinus CT.

MATERIALS AND METHODS

Twenty patients consented to participate and underwent low- and standard-dose sinus CT on the same day. Standard-dose CT was created with filtered back-projection (120 kV[peak], 210 mA, 0.4-second rotation, and 0.531 pitch). For low-dose CT, mA was decreased to 20 (the remaining parameters were unchanged), and images were generated with filtered back-projection and Veo. Standard- and low-dose datasets were reconstructed by using bone and soft-tissue algorithms, while the low-dose Veo reconstruction only had a standard kernel. Two blinded neuroradiologists independently evaluated the image quality of multiple osseous and soft-tissue craniofacial structures. Image noise was measured by using multiple regions of interest.

RESULTS

Eight women and 12 men (mean age, 63.3 years) participated. Volume CT dose indices were 2.9 mGy (low dose) and 31.6 mGy (standard dose), and mean dose-length products were 37.4 mGy-cm (low dose) and 406.1 mGy-cm (standard dose). Of all the imaging series, low-dose Veo demonstrated the least noise (P < .001). Compared with filtered back-projection low-dose CT using soft-tissue and bone algorithms, Veo had the best soft-tissue image quality but the poorest bone image quality (P < .001).

CONCLUSIONS

Veo significantly reduces noise in low-dose sinus CT. Although this reduction improves soft-tissue evaluation, thin bone becomes less distinct.