Clinical application of radiation dose reduction for head and neck CT

Cranial Computer Tomography with Photon Counting and Energy-Integrated Detectors: Objective Comparison in the Same Patients

This study provides an objective comparison of cranial computed tomography (CT) imaging quality and radiation dose between photon counting detectors (PCCTs) and energy-integrated detectors (EIDs). We retrospectively analyzed 158 CT scans from 76 patients, employing both detector types on the same individuals to ensure a consistent comparison. Our analysis focused on the Computed Tomography Dose Index and the Dose-Length Product together with the contrast-to-noise ratio and the signal-to-noise ratio for brain gray and white matter. We utilized standardized imaging protocols and consistent patient positioning to minimize variables. PCCT showed a potential for higher image quality and lower radiation doses, as highlighted by this study, thus achieving diagnostic clarity with reduced radiation exposure, underlining its significance in patient care, particularly for patients requiring multiple scans. The results demonstrated that while both systems were effective, PCCT offered enhanced imaging and patient safety in neuroradiological evaluations.

Consensus paper on the assessment of adult patients with traumatic brain injury with Glasgow Coma Scale 13-15 at the emergency department: A multidisciplinary overview

Traumatic brain injury (TBI) is a common reason for presenting to emergency departments (EDs). The assessment of these patients is frequently hampered by various confounders, and diagnostics is still often based on nonspecific clinical signs. Throughout Europe, there is wide variation in clinical practices, including the follow-up of those discharged from the ED. The objective is to present a practical recommendation for the assessment of adult patients with an acute TBI, focusing on milder cases not requiring in-hospital care. The aim is to advise on and harmonize practices for European settings. A multiprofessional expert panel, giving consensus recommendations based on recent scientific literature and clinical practices, is employed. The focus is on patients with a preserved consciousness (Glasgow Coma Scale 13-15) not requiring in-hospital care after ED assessment. The main results of this paper contain practical, clinically usable recommendations for acute clinical assessment, decision-making on acute head computerized tomography (CT), use of biomarkers, discharge options, and needs for follow-up, as well as a discussion of the main features and risk factors for prolonged recovery. In conclusion, this consensus paper provides a practical stepwise approach for the clinical assessment of patients with an acute TBI at the ED. Recommendations are given for the performance of acute head CT, use of brain biomarkers and disposition after ED care including careful patient information and organization of follow-up for those discharged.

Evaluation of radiation dose in multi-slice computed tomography protocols of head and neck regions

In head and neck computed tomography (CT) imaging, the optimisation of radiation dose is crucial due to the presence of radio-sensitive organs. This study aimed to evaluate the radiation dose in multi-slice CT for head and neck examinations. Volume CT dose index, dose length product and effective dose (E) were assessed for 10 head and neck CT scans performed on 292 adult patients (mean age 49.2 ± 15.9 y). The study resulted in median E values of 0.82, 1.62, 2.43, 0.93, 1.70, 0.83, 3.55, 6.25, 2.19 and 5.26 mSv, respectively, for sinuses (non-contrast (NC)), sinuses (NC) and contrast-enhanced (CE), petrous bone (PTB)/internal auditory meatus (IAM) (NC + CE), PTB/IAM (NC), orbit (NC + CE), orbit (NC), brain with the orbit (NC), brain CT angiography (CTA) subtraction, neck (NC) and brain/neck (NC). Furthermore, the overall radiation doses of this institution were found to be below the values suggested by similar studies. However, optimisation of the dose is required for brain CTA.

Organ-based tube current modulation and bismuth eye shielding in pediatric head computed tomography

BACKGROUND

Exposure of the eye lens to ionizing radiation results in cataract. Several dose optimization techniques to protect the lens are available for computed tomography (CT).

OBJECTIVE

The radiation dose to the eye lens, volume CT dose index (CTDI_vol) and image quality of various methods of dose optimization were evaluated for pediatric head CT: automated tube current modulation (ATCM), automated tube voltage selection (ATVS), organ-based tube current modulation (OBTCM) and bismuth shielding.

MATERIALS AND METHODS

An anthropomorphic phantom of a 5-year-old child was scanned with nine protocols: no dose optimization technique and then adding different dose optimization techniques alone and in combination. Dose to the eye, thyroid and breast were estimated using metal oxide semiconductor field effect transistor (MOSFET) dosimetry. CTDI_vol, influence of timing of shield placement, image noise and attenuation values in 13 regions of interest of the head and subjective image quality were compared.

RESULTS

The eye shield significantly reduced the eye lens dose when used alone, to a similar degree as when using all software-based techniques together. When used in combination with software-based techniques, the shield reduced the eye lens dose by up to 45% compared to the no dose optimization technique. Noise was significantly increased by the shield, most pronounced in the anterior portion of the eye.

CONCLUSION

The combination of ATCM, ATVS, OBTCM and a bismuth shield, with the shield placed after acquiring the localizer image, should be considered to reduce the radiation dose to the eye lens in pediatric head CT.

Automated patient centering of computed tomography images and its implementation to evaluate clinical practices in three hospitals in Indonesia

Purpose: This study aims to develop a software tool for investigating patient centering profiles of axial CT images and to implement it to evaluate practices in three hospitals in Indonesia.

Methods: The evaluation of patient centering accuracy was conducted by comparing the center coordinate of the patient’s image to the center coordinates of the axial CT image. This process was iterated for all slices to yield an average patient mis-centering in both the x- and y-axis. We implemented the software to evaluate the profile of centering on 268 patient images from the head, thorax, and abdomen examinations taken from three hospitals.

Results: We found that 82% of patients were mis-centered in the y-axis (i.e., placed more than 5 mm from the iso-center), with 49% of patients placed 10–35 mm from the iso-center. Most of the patients had a tendency to be placed below the iso-centers. In head examinations, patients were more precisely positioned than in the other examinations. We did not find any significant difference in mis-centering between males and females. We found that there was a slight difference between mis-centering in adult and pediatric patients.

Conclusion: Software for automated patient centering was successfully developed. Patients in three hospitals in Indonesia had a tendency to be placed under the iso-center of the gantry.

Joint application of hybrid iterative reconstruction and adaptive filters on neck-and-shoulder CT imaging: A clinical evaluation

PURPOSE

To assess whether the joint application of hybrid iterative reconstruction (HIR) and an adaptive filter (AF) could reduce streak artifacts and improve image quality of neck-and-shoulder computed tomography (CT).

METHODS

This study included 96 patients with suspicious neck lesions who underwent a routine nonenhanced scan on a 64-slice CT scanner. The raw data were reconstructed using four different settings: filtered back projection (FBP), HIR, FBP + AF, and HIR + AF. Regions of interest were manually drawn in erector spine, axillary fat, latissimus dorsi, and dorsal cervical fat. Mean and standard deviation (SD) of the CT number, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were obtained and compared using Wilcoxon signed-rank tests. The qualitative assessments of five factors were compared by two independent investigators.

RESULTS

Compared to the other three settings, HIR + AF reduced noise in the area where the streak artifact of the lower neck were most serious (SD; all p ≤ 0.001). The SNR and CNR were improved significantly (all p ≤ 0.001). Compared to the other three settings, HIR + AF showed a significant improvement in CT image quality regarding the visibility of suspicious lesions, the extent of streaking artifacts, noise, soft-tissue contrast, and visualization of small structures (all p ≤ 0.02).

CONCLUSIONS

The combination of HIR and AF can significantly reduce streaking artifacts and improve image quality in neck-and-shoulder CT imaging.

Improvement in Validity and Reliability of Airway Assessment Using Ultrasonography by Novice Personnel: A Learning Cohort Study

PURPOSE

To assess improvements in the validity and reliability of novices' skills in performing ultrasonography for airway assessment.

PATIENTS AND METHODS

A learning cohort study was conducted with 20 anesthesiology residents and 10 volunteers in the Department of Anesthesiology, Faculty of Medicine, Prince of Songkla University. The four parameters of airway assessment were soft tissue thickness at the level of 1) hyoid bone (STT-HY), 2) true vocal cords (STT-VC), 3) thyroid isthmus (STT-TI), and 4) suprasternal notch (STT-SN). The magnitude of discrepancies between the residents' and experienced anesthesiologists' measurements was evaluated over the sequence of measurements in the 10 volunteers.

RESULTS

The mean ultrasonic measurements of STT-HY by the experienced anesthesiologists and residents were significantly different (11.09 ± 3.14 mm vs 8.53 ± 3.02 mm, respectively; P = 0.008), whereas measurements of STT-VC, STT-TI, and STT-SN were not (7.18 ± 1.70 vs 7.14 ± 1.93, P = 0.32; 7.81 ± 2.14 vs 7.73 ± 2.19, P = 0.62; and 11.32 ± 3.33 vs 10.30 ± 3.02, P = 0.35, respectively). The mean discrepancy between the residents' and experienced anesthesiologists' measurements was close to zero throughout the sequence of measurements of STT-TI and STT-VC. However, the residents' measurements of STT-HY and STT-SN were considerably lower than those of anesthesiologists. The range of discrepancies between residents and experienced anesthesiologists in each sequential measurement was wide for all measurements, particularly for the measurement values of STT-HY, and the standard deviation of the discrepancies did not decrease over the sequence of measurements.

CONCLUSION

Over the sequence of measurements for airway assessment in 10 volunteers by 20 residents in this learning trial, we found no evidence of improvement in measurement accuracy. Discrepancies between the residents' and anesthesiologists' measurements and the variability in discrepancy across residents were greatest in the measurement of STT-HY.

Are Continued Efforts to Reduce Radiation Exposures from X-Rays Warranted?

There are pressures to avoid use of radiological imaging throughout all healthcare due to the notion that all radiation is carcinogenic. This perception stems from the long-standing use of the linear no-threshold (LNT) assumption of risk associated with radiation exposures. This societal perception has led to relentless efforts to avoid and reduce radiation exposures to patients at great costs. Many radiation reduction campaigns have been launched to dissuade doctors from using radiation imaging. Lower-dose imaging techniques and practices are being advocated. Alternate imaging procedures are encouraged. Are these efforts warranted? Based on recent evidence, LNT ideology is shown to be defunct for risk assessment at low-dose exposure ranges which includes X-rays and CT scans. In fact, the best evidence that was once used to support LNT ideology, including the Life Span Study data, now indicates thresholds for cancer induction are high; therefore, low-dose X-rays cannot cause harm. Current practices are safe as exposures currently encountered are orders of magnitude below threshold levels shown to be harmful. As long as imaging is medically warranted, it is shown that efforts to reduce exposures that are within background radiation levels and that are also shown to enhance health by upregulating natural adaptive protection systems are definitively wasted resources.

Artificial Intelligence and Big Data

Medical images play an important role in ophthalmology and radiology. Medical image analysis has greatly benefited from the application of "deep learning" techniques in clinical and experimental radiology. Clinical applications and their relevance for radiological imaging in ophthalmology are presented.

Hydrocephalus: Ventricular Volume Quantification Using Three-Dimensional Brain CT Data and Semiautomatic Three-Dimensional Threshold-Based Segmentation Approach

OBJECTIVE

To evaluate the usefulness of the ventricular volume percentage quantified using three-dimensional (3D) brain computed tomography (CT) data for interpreting serial changes in hydrocephalus.

MATERIALS AND METHODS

Intracranial and ventricular volumes were quantified using the semiautomatic 3D threshold-based segmentation approach for 113 brain CT examinations (age at brain CT examination ≤ 18 years) in 38 patients with hydrocephalus. Changes in ventricular volume percentage were calculated using 75 serial brain CT pairs (time interval 173.6 ± 234.9 days) and compared with the conventional assessment of changes in hydrocephalus (increased, unchanged, or decreased). A cut-off value for the diagnosis of no change in hydrocephalus was calculated using receiver operating characteristic curve analysis. The reproducibility of the volumetric measurements was assessed using the intraclass correlation coefficient on a subset of 20 brain CT examinations.

RESULTS

Mean intracranial volume, ventricular volume, and ventricular volume percentage were 1284.6 ± 297.1 cm³, 249.0 ± 150.8 cm³, and 19.9 ± 12.8%, respectively. The volumetric measurements were highly reproducible (intraclass correlation coefficient = 1.0). Serial changes (0.8 ± 0.6%) in ventricular volume percentage in the unchanged group (n = 28) were significantly smaller than those in the increased and decreased groups (6.8 ± 4.3% and 5.6 ± 4.2%, respectively; p = 0.001 and p < 0.001, respectively; n = 11 and n = 36, respectively). The ventricular volume percentage was an excellent parameter for evaluating the degree of hydrocephalus (area under the receiver operating characteristic curve = 0.975; 95% confidence interval, 0.948-1.000; p < 0.001). With a cut-off value of 2.4%, the diagnosis of unchanged hydrocephalus could be made with 83.0% sensitivity and 100.0% specificity.

CONCLUSION

The ventricular volume percentage quantified using 3D brain CT data is useful for interpreting serial changes in hydrocephalus.

Bucco alveolar bone thickness of mandibular impacted third molars with different inclinations: a CBCT study

PURPOSE

To compare the buccal alveolar bone thickness of mesioangulated mandibular impacted third molars (MITM) with buccal versus lingual inclination using cone-beam computed tomography (CBCT).

METHODS

This retrospective cross-sectional study evaluated 69 individuals (39 women and 30 men) who presented a total of 101 mesioangulated MITM according to the Winter classification and in B position according to the Pell and Gregory classification. The average age was 22.99 ± 3.94 years. The superior, medial and inferior alveolar thickness regarding buccal (n = 44) or lingual (n = 57) mandibular third molar inclination were measured. T test or Mann-Whitney U test and finally, a multiple linear regression were applied (p < 0.05).

RESULTS

The buccal alveolar bone thickness of mesioangulated mandibular impacted third molars was significantly greater in the group with lingual inclination compared to the group with buccal inclination, in the superior region (6.21 ± 3.27 vs. 4.85 ± 3.06; p = 0.036). The lingual inclination significantly influenced the buccal alveolar bone thickness in the middle region (p = 0.011).

CONCLUSIONS

The mesioangulated MITM in B position with lingual inclination have a greater thickness of the superior and medial buccal alveolar bone than the MITM with buccal inclination. These results should be considered during MITM diagnosis and surgical planning.

Application of low-concentration contrast agents and low-tube-voltage computed tomography to chest enhancement examinations: A multicenter prospective study

To evaluate the influence of low-concentration contrast agents and low-tube-voltage computed tomography on chest enhancement examinations, we conducted a multicenter prospective study. A total of 216 inpatients enrolled from 12 different hospitals were randomly divided into four groups: A: voltage, 120 kVp; iohexol, 350 mgI/mL; B: voltage, 100 kVp, iohexol, 350 mgI/mL; C: voltage, 120 kVp, iodixanol, 270 mgI/mL; and D: voltage, 100 kVp, iodixanol, 270 mgI/mL. Subjective image quality was assessed by two radiologists and compared by weighted kappa test. The objective image scores, scanning radiation doses, and pathological coincidence rates were analyzed. There were no significant differences in gender, age, height, weight, and body mass index between the four groups (p > 0.05). The consistency of the radiologists' ratings were good, with kappa value ranging from 0.736 (95% confidence interval: 0.54-0.933) to 0.809 (95% confidence interval: 0.65-0.968), and there was no difference in subjective image score between the four groups. The computed tomography value of group D had no difference with group A. The volume computed tomography dose index, dose length product, and effective dose of group D (6.93 ± 3.03, 241.55 ± 104.75, and 3.38 ± 1.47, respectively) were all significantly lower than those of group A (10.30 ± 4.37, 359.70 ± 152.65, and 5.04 ± 2.14, respectively). There was no significant difference in the imaging diagnosis accuracy rate between the four groups (p > 0.05). The results indicated that low-concentration contrast agents (270 mgI/mL) and low-tube-voltage (100 kVp) computed tomography can not only decrease radiation dose but also guarantee the image quality and meet the needs of imaging diagnosis in chest enhancement examinations, which make it possible for its generalization and application.

Assessment of image quality and dose in contrast-enhanced head and neck CT angiography of New Zealand rabbit

BACKGROUND

Although computed tomography (CT) is a powerful diagnostic imaging modality for diagnosing vascular diseases, it is some what risky to human health due to the high radiation dosage. Thus, CT vendors have developed low dose computed tomography (LDCT) aiming to solve this problem. Nowadays, LDCT has gradually become a main stream of CT examination.

OBJECTIVE

This study aimed to assess the feasibility of LDCTAin an animal model and compare the imaging features and doses in two clinical scanners.

METHODS

Twenty-two New Zealand rabbit head and neck CTA images pre- and post-contrast agent injection were performed using256-sliceand 64-slice CT scanners. The tube voltages used in the 256-slice and the 64-slice CTA were 70 kVp and 80 kVp, respectively. Quantitative images indices and radiation doses obtained from CTA in these two scanners were compared.

RESULTS

More neck arterial vessels could be visualized in multi-planar reconstruction (MPR) CTA on the 256-slice CT scanner than on the 64-slice CT scanner. After contrast agent injection, all observed neck arterial vessels had higher CT numbers in 256-slice CTA than in 64-slice CTA. There was no significant difference in contrast-to-noise (CNR) of CTA images between these two scanners. CT dose index (CTDI) and dose length product (DLP) for the 256-slice CTA were lower than those for the 64-slice CTA.

CONCLUSIONS

Low dose CTA of rabbits with 70 or 80 kVp is feasible in a 256-slice or a 64-slice CT scanner. The radiation dose from the 256-slice CTA was much lower than that from the 64-slice CTA with comparable SNR and CNR. The technique can be further applied in longitudinal monitoring of an animal stroke model in the future.

Computed tomography-guided navigated transcranial magnetic stimulation for preoperative brain motor mapping in brain lesion resection: A case report

Background:

Navigated transcranial magnetic stimulation (nTMS) is a well establish a noninvasive method for preoperative brain motor mapping. We commonly use magnetic resonance imaging (MRI) to supply the nTMS system. In some cases, MRI is not possible or available, and the use of computed tomography (CT) is necessary. We present the first report describing the association of CT and nTMS motor mapping for brain lesion resection.

Case Description:

CT imaging of a 59-year-old man suffering from acquired immune deficiency syndrome for 17 years, presenting with seizure and right hemiparesis, revealed a small single hypodense ring-enhancing lesion in the left central sulci suggesting cerebral toxoplasmosis. After 3 weeks of neurotoxoplasmosis treatment, due to four consecutive tonic-clonic seizures, a new CT scan was performed and showed no lesion changes. MRI was in maintenance at that time. Infectious diseases department suggested a brain lesion biopsy. Due to lesion’s location, we decided to perform a presurgical nTMS motor mapping. After a small craniotomy, we could precisely locate and safely totally remove the lesion. The pathology report revealed a high suspicious toxoplasmosis pattern. The patient was discharged after 2 days and continued toxoplasmosis treatment. After 6 months follow-up, he showed no signs of any procedure-related deficits or radiological recurrence.

Conclusion:

We report the feasibility and applicability of nTMS motor mapping using CT scan as an image source. It gives neurosurgeons another possibility to perform motor mapping for brain lesion removal, especially when MRI is not available or feasible.

Development of a novel artifact-free eye shield based on silicon rubber-lead composition in the CT examination of the head

The aim of this work was to develop a novel artifact-free eye shield and evaluate its effect on the dose received by the eye lens and the resulting image quality in the CT examination of the head. A new material for an eye shield was synthesised from silicon rubber (SR) and lead (Pb) using a simple method. The percentage of Pb was varied from 0 to 5% wt. An anthropomorphic head phantom was scanned with and without the SR-Pb eye shield, and compared with a tungsten paper (WP) eye shield. The distance from the eye shield and head was varied from 0 to 5 cm. The dose to the eye lens was measured using photo-luminescence detectors (PLDs). The presence of artifacts was determined by measuring CT numbers at different eye lens locations and by subtracting images with and without the eye shield. The dose reduction increases with increasing Pb content in the SR-Pb eye shield. A 5% wt SR-Pb eye shield reduced the eye lens dose by up to 50%, whereas the WP eye shield reduced the dose by up to 86%. The CT numbers in images with the SR-Pb eye shield in the regions of both eyes and the center of the head phantom is similar to those without the eye shield, indicating that there is no artifact in the resulting image. Using the WP eye shield, there is considerable artifact with the CT number increasing by up to 700% in the regions of both eyes and the center of the head. It is found that the distance between the SR-Pb eye shield and the head does not affect either the dose or the resulting images. A SR-Pb-based eye shield can be applied in clinical environments and should be placed directly above the eye surface for dose optimisation.

Sinus augmentation analysis of the gradient of graft consolidation: a split-mouth histomorphometric study

OBJECTIVE

The aim of this study was to histomorphometrically test the hypothesis that graft consolidation originates from the sinus floor.

MATERIALS AND METHODS

This prospective, randomized split-mouth study investigated patients undergoing bilateral maxillary lateral sinus floor augmentation using either freeze-dried bone allografts (FDBAs) or biphasic calcium phosphate (BCP) bone substitute. Apico-coronal core biopsies were harvested during implant placement 9 months after sinus floor augmentation, processed for histological observation, and measured histomorphometrically.

RESULTS

Biopsies were taken from 26 bilateral sites in 13 patients. The density of new bone (NB) decreased with increasing distance from the sinus floor. The percentage mean surface of NB ranged from 31 ± 9.5% at 2 mm from the sinus floor (G1) to 27.7 ± 11.2% at 4 mm (G2) for the FDBA specimens and from 30.0 ± 11.0% at G1 to 23.5 ± 9.9% at G2 for the BCP specimens. Evaluation of the residual graft particle (GP) area alone as a function of distance from the floor revealed a clear inverse gradient of 7.1 ± 6.6 to 9.1 ± 10.3 between G1 and G2 for the FDBA allografts, with the same tendency for the BCP alloplasts (21.9 ± 9.9 to 27.7 ± 6.6, respectively).

CONCLUSION

Our results support the concept that osteogenesis initiates in regions proximal to the bony walls of the maxillary sinus and may be enhanced by them.

CLINICAL RELEVANCE

The nature of the grafting material had a greater influence on the degree of NB formation in regions distant from the native walls where there is reduced inherent osteogenic potential.

Basics of iterative reconstruction methods in computed tomography: A vendor-independent overview

Over the past two decades, technical innovations in computed tomography (CT) have constantly extended its spectrum of clinical applications and made new radiodiagnostic applications accessible. At the same time, concerns have arisen with respect to the radiation exposure to the patients caused by CT examinations. In order to address this issue, different strategies for radiation dose reduction in CT have been introduced, spanning technical approaches as well as specific examination techniques applied in clinical practice, such as reduced-dose CT. Developed technical approaches for reducing radiation dose in CT by improvements of CT scanner hardware and acquisition mechanisms, however, have not been sufficient to address the degradation of image quality caused by increasing noise and susceptibility to artifacts inherent to reduced-dose CT acquisitions. Recent advances in computing power have enabled the development of software-based methods for iterative image reconstruction (IR) in CT enabling simultaneous reduction of image noise and improvement of overall image quality. Thereby, IR allows for dose reduction by reconstruction of low-noise image data from intrinsically noisy reduced-dose CT acquisitions, thereby preserving diagnostic image quality equivalent to current clinical standards. This review provides an overview of the underlying basic principles of iterative image reconstruction methods currently available for and applied in CT imaging, independent of vendor-specific details regarding algorithms and implementations. It discusses potential strengths and weaknesses of these CT image reconstruction techniques in view of their application in clinical routine, especially in view of the potential of IR for noise and artifact reduction as well as for radiation dose reduction. Furthermore, the effect of statistical (hybrid) and model-based IR methods on image quality are exemplarily illustrated in comparison to filtered back projection (FBP) traditionally used for image reconstruction in CT.