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Misregistration between CT and PET in PET/CT is mainly caused by respiratory motion or irregular respiration during the CT scan in PET/CT. Other than repeat CT, repeat PET/CT, or data-driven gated (DDG) CT, there is no practical approach to mitigate the misregistration artifacts and subsequent CT attenuation correction (CTAC) of the PET data. DDG PET derives a respiratory motion model based on the multiple phases of PET images without hardware gating and it allows for a potential correction of the misregistration artifacts based on the respiratory motion model. The purpose of this commentary was to compare the recent two publications on matching the random phase of helical CT with one of the PET phases derived from the motion model of DDG PET and warping the misregistered helical CT for CTAC of and registration with PET or DDG PET. The two publications were similar in methodology. However, the data sets used for the comparison were different and could potentially impact their conclusions. [ABSTRACT FROM AUTHOR]

Abstract Misregistration between CT and PET in PET/CT is mainly caused by respiratory motion or irregular respiration during the CT scan in PET/CT. Other than repeat CT, repeat PET/CT, or data-driven gated (DDG) CT, there is no practical approach to mitigate the misregistration artifacts and subsequent CT attenuation correction (CTAC) of the PET data. DDG PET derives a respiratory motion model based on the multiple phases of PET images without hardware gating and it allows for a potential correction of the misregistration artifacts based on the respiratory motion model. The purpose of this commentary was to compare the recent two publications on matching the random phase of helical CT with one of the PET phases derived from the motion model of DDG PET and warping the misregistered helical CT for CTAC of and registration with PET or DDG PET. The two publications were similar in methodology. However, the data sets used for the comparison were different and could potentially impact their conclusions.

The complex anatomical structure of the foot-ankle imposes challenges to accurately quantify detailed hindfoot kinematics and estimate musculoskeletal loading parameters. Most systems used to capture or estimate dynamic joint function oversimplify the anatomical structure by reducing its complexity. Can four dimensional computed tomography (4D CT) imaging in combination with an innovative foot manipulator capture in vivo hindfoot kinematics during a simulated stance phase of walking and can talocrural and subtalar articular joint mechanics be estimated based on a detailed in silico musculoskeletal foot-ankle model. A foot manipulator imposed plantar/dorsiflexion and inversion/eversion representing a healthy stance phase of gait in 12 healthy participants while simultaneously acquiring 4D CT images. Participant-specific 3D hindfoot rotations and translations were calculated based on bone-specific anatomical coordinate systems. Articular cartilage contact area and contact pressure of the talocrural and subtalar joints were estimated using an extended foot-ankle model updated with an elastic foundation contact model upon prescribing the participant-specific rotations measured in the 4D CT measurement. Plantar/dorsiflexion predominantly occurred at the talocrural joint (RoM 15.9±3.9°), while inversion/eversion (RoM 5.9±3.9°) occurred mostly at the subtalar joint, with the contact area being larger at the subtalar than at the talocrural joint. Contact pressure was evenly distributed between the talocrural and subtalar joint at the beginning of the simulated stance phase but was then redistributed from the talocrural to the subtalar joint with increasing dorsiflexion. In a clinical case study, the healthy participants were compared with four patients after surgically treaded intra-articular calcaneal fracture. The proposed workflow was able to detect small but meaningful differences in hindfoot kinematics and kinetics, indicative of remaining hindfoot pathomechanics that may influence the onset and progression of degenerative joint diseases. • 4D CT enables in vivo quantification of dynamic gait-like motion of the hindfoot. • Talocrural joint allows plantar/dorsiflexion; subtalar enables inversion/eversion. • Musculoskeletal modelling allows quantification of dynamic hindfoot loading. • Talocrural contact pressure is negatively correlated with talocrural dorsiflexion. • Detection of meaningful differences between healthy and pathological subjects. [ABSTRACT FROM AUTHOR]

Our rationale was to review the imaging options for patients with primary hyperparathyroidism and to advocate for judicious use of 4-dimensional (4D) SPECT/CT to visualize diseased parathyroid glands in patients with complex medical profiles or in whom other imaging modalities fail. We review the advantages and disadvantages of traditional imaging modalities used in preoperative assessment of patients with primary hyperparathyroidism: ultrasound, SPECT, and 4D CT. We describe a scheme for optimizing and individualizing preoperative imaging of patients with hyperfunctioning parathyroid glands using traditional modalities in tandem with 4D SPECT/CT. Using the input from radiologists, endocrinologists, and surgeons, we apply patient criteria such as large body habitus, concomitant multiglandular disease, multinodular thyroid disease, confusing previous imaging, and unsuccessful previous surgery to create an imaging paradigm that uses 4D SPECT/CT yet is cost-effective, accurate, and limits extraneous radiation exposure. 4D SPECT/CT capitalizes on the strengths of SPECT and 4D CT and addresses limitations that exist when these modalities are used in isolation. In select patients with complicated clinical parameters, preoperative imaging with 4D SPECT/CT can improve accuracy yet remain cost-effective. [ABSTRACT FROM AUTHOR]

Background: 4D CT imaging is an essential component of radiotherapy of thoracic and abdominal tumors. 4D CT images are, however, often affected by artifacts that compromise treatment planning quality and image information reliability. Purpose: In this work, deep learning (DL)‐based conditional inpainting is proposed to restore anatomically correct image information of artifact‐affected areas. Methods: The restoration approach consists of a two‐stage process: DL‐based detection of common interpolation (INT) and double structure (DS) artifacts, followed by conditional inpainting applied to the artifact areas. In this context, conditional refers to a guidance of the inpainting process by patient‐specific image data to ensure anatomically reliable results. The study is based on 65 in‐house 4D CT images of lung cancer patients (48 with only slight artifacts, 17 with pronounced artifacts) and two publicly available 4D CT data sets that serve as independent external test sets. Results: Automated artifact detection revealed a ROC‐AUC of 0.99 for INT and of 0.97 for DS artifacts (in‐house data). The proposed inpainting method decreased the average root mean squared error (RMSE) by 52 % (INT) and 59 % (DS) for the in‐house data. For the external test data sets, the RMSE improvement is similar (50 % and 59 %, respectively). Applied to 4D CT data with pronounced artifacts (not part of the training set), 72 % of the detectable artifacts were removed. Conclusions: The results highlight the potential of DL‐based inpainting for restoration of artifact‐affected 4D CT data. Compared to recent 4D CT inpainting and restoration approaches, the proposed methodology illustrates the advantages of exploiting patient‐specific prior image information. [ABSTRACT FROM AUTHOR]

Objective: Primary hyperparathyroidism (PHPT) affects approximately 0.86% of the population, with surgical resection as the treatment of choice. A 4D computed tomography (CT) is a highly effective tool in localizing parathyroid adenomas; however, there is currently no defined role for 4D CT when stratified against ultrasonography (USG) and nuclear medicine Technetium Sestamibi SPECT/CT (SES) imaging. Study Design: Retrospective Study. Setting: University Hospital. Methods: All patients who underwent parathyroidectomy for PHPT between 2014 and 2019 at a single institution were reviewed. Patients who had a 4D CT were included. We compared outcomes of 4D CT as a second line imaging modality to those of USG and SES as first line modalities. An imaging algorithm was proposed based on these findings. Results: There were 84 patients identified who had a 4D CT after unsuccessful first line imaging. A 4D CT localized parathyroid adenoma to the correct quadrant in 64% of cases, and to the correct laterality in 75% of cases. Obese patients had significantly lower rates of adenoma localization with USG (33.4%), compared to non-obese patients (67.5%; P =.006). In determining multigland disease the sensitivity of 4D CT was 86%, while the specificity was 87%. Conclusions: A 4D CT has impressive rates of accurate localization of parathyroid adenomas; however due to the radiation exposure involved, it should remain a second line imaging modality. PHPT patients should first be evaluated with USG, with 4D CT used if this is unsuccessful and patients are greater than 40 years old, have a high BMI, or are having revision surgery. [ABSTRACT FROM AUTHOR]

Background: Respiratory signal‐guided 4D CT sequence scanning such as the recently introduced Intelligent 4D CT (i4DCT) approach reduces image artifacts compared to conventional 4D CT, especially for irregular breathing. i4DCT selects beam‐on periods during scanning such that data sufficiency conditions are fulfilled for each couch position. However, covering entire breathing cycles during beam‐on periods leads to redundant projection data and unnecessary dose to the patient during long exhalation phases. Purpose: We propose and evaluate the feasibility of respiratory signal‐guided dose modulation (i.e., temporary reduction of the CT tube current) to reduce the i4DCT imaging dose while maintaining high projection data coverage for image reconstruction. Methods: The study is designed as an in‐silico feasibility study. Dose down‐ and up‐regulation criteria were defined based on the patients' breathing signals and their representative breathing cycle learned before and during scanning. The evaluation (including an analysis of the impact of the dose modulation criteria parameters) was based on 510 clinical 4D CT breathing curves. Dose reduction was determined as the fraction of the downregulated dose delivery time to the overall beam‐on time. Furthermore, under the assumption of a 10‐phase 4D CT and amplitude‐based reconstruction, beam‐on periods were considered negatively affected by dose modulation if the downregulation period covered an entire phase‐specific amplitude range for a specific breathing phase (i.e., no appropriate reconstruction of the phase image possible for this specific beam‐on period). Corresponding phase‐specific amplitude bins are subsequently denoted as compromised bins. Results: Dose modulation resulted in a median dose reduction of 10.4% (lower quartile: 7.4%, upper quartile: 13.8%, maximum: 28.6%; all values corresponding to a default parameterization of the dose modulation criteria). Compromised bins were observed in 1.0% of the beam‐on periods (72 / 7370 periods) and affected 10.6% of the curves (54/510 curves). The extent of possible dose modulation depends strongly on the individual breathing patterns and is weakly correlated with the median breathing cycle length (Spearman correlation coefficient 0.22, p < 0.001). Moreover, the fraction of beam‐on periods with compromised bins is weakly anti‐correlated with the patient's median breathing cycle length (Spearman correlation coefficient ‐0.24; p < 0.001). Among the curves with the 17% longest average breathing cycles, no negatively affected beam‐on periods were observed. Conclusion: Respiratory signal‐guided dose modulation for i4DCT imaging is feasible and promises to significantly reduce the imaging dose with little impact on projection data coverage. However, the impact on image quality remains to be investigated in a follow‐up study. [ABSTRACT FROM AUTHOR]

Objectives: To assess the performance of dynamic or 4D CT in characterizing endoleaks in advanced endovascular aortic repair (branched and fenestrated) when other modalities fail to fully characterize the leak, most often conventional CTA. Methods: Retrospective review of 13 patients from 2008 to 2021 who underwent 16 4D CTs to characterize endoleaks in branched and fenestrated endovascular aortic repair (FB-EVAR). The 4D CTs were performed covering up to 16 cm of the z-axis, with anywhere between 10 and 40 iterations performed every 2 s. These settings were adjusted depending on graft characteristics and type of endoleak suspected. The scans were assessed for their ability to detect the endoleak (sensitivity), and further to characterize the endoleak by type and subtype (specificity). Results: Overall sensitivity in 16 scans for endoleak detection was 100%. There was a specificity of 87.5% for determining the type of endoleak (14/16). These results included two studies that were inconclusive and repeated due to technical difficulties. In patients where a specific subtype was not established, the leak was localized to the appropriate target vessel. Average dose for the 4D CT was 4724 mGy*cm (1108–11069), with the outlining higher dose scans secondary to higher iterations in those scans. Conclusions: 4D CT is a useful adjunctive tool in FB-EVAR surveillance with excellent sensitivity and specificity in characterizing endoleaks. This allows for accurate localization of leaks, which is critical for management planning. [ABSTRACT FROM AUTHOR]

Purpose: 4D CT imaging is an integral part of 4D radiotherapy workflows. However, 4D CT data often contain motion artifacts that mitigate treatment planning. Recently, breathing-adapted 4D CT (i4DCT) was introduced into clinical practice, promising artifact reduction in in-silico and phantom studies. Here, we present an image quality comparison study, pooling clinical patient data from two centers: a new i4DCT and a conventional spiral 4D CT patient cohort. Methods: The i4DCT cohort comprises 129 and the conventional spiral 4D CT cohort 417 4D CT data sets of lung and liver tumor patients. All data were acquired for treatment planning. The study consists of three parts: illustration of image quality in selected patients of the two cohorts with similar breathing patterns; an image quality expert rater study; and automated analysis of the artifact frequency. Results: Image data of the patients with similar breathing patterns underline artifact reduction by i4DCT compared to conventional spiral 4D CT. Based on a subgroup of 50 patients with irregular breathing patterns, the rater study reveals a fraction of almost artifact-free scans of 89% for i4DCT and only 25% for conventional 4D CT; the quantitative analysis indicated a reduction of artifact frequency by 31% for i4DCT. Conclusion: The results demonstrate 4D CT image quality improvement for patients with irregular breathing patterns by breathing-adapted 4D CT in this first corresponding clinical data image quality comparison study. [ABSTRACT FROM AUTHOR]

Key Clinical Message: Ectopic mediastinal parathyroid adenoma causes primary hyperparathyroidism presenting as hypercalcemia. When children with hypercalcemia present with slipped capital femoral epiphysis, a detailed evaluation for hypercalcemia must be done before surgery. The association between slipped capital femoral epiphysis (SCFE) and hyperparathyroidism has been reported and is rare. Each is known to affect different age groups. We report a case of a 13‐year‐old boy with SCFE and primary HPT leading to hypercalcemia and skeletal deformities. [ABSTRACT FROM AUTHOR]

Key Clinical Message Ectopic mediastinal parathyroid adenoma causes primary hyperparathyroidism presenting as hypercalcemia. When children with hypercalcemia present with slipped capital femoral epiphysis, a detailed evaluation for hypercalcemia must be done before surgery. Abstract The association between slipped capital femoral epiphysis (SCFE) and hyperparathyroidism has been reported and is rare. Each is known to affect different age groups. We report a case of a 13‐year‐old boy with SCFE and primary HPT leading to hypercalcemia and skeletal deformities.

In this paper, a new method for the mathematical tomographic reconstruction of time-varying objects (4D tomography) is presented. The method is applicable under the conditions that the amount of substance at each spatial point does not decrease, and only one projection image is available per time point during the process of the object changing. The temporal resolution of the proposed method is obtained by using an iterative approach to reconstruction. Prior knowledge about object morphology is exploited to improve the convergence of the algorithm by reducing the number of processed spatial points. Verification of the algorithm operation was carried out using model examples. The presented method was experimentally tested on the tomographic reconstruction of the dynamics of the capillary rise of a liquid. Our experiments demonstrated that monitoring fast processes, when the speed of the process does not allow to measure more than one tomographic projection, is potentially possible.

Background: Four-dimensional computed tomography (4D CT) is rapidly emerging as a diagnostic tool for the investigation of dynamic upper limb disorders. Dynamic elbow pathologies are challenging to diagnose, and at present, limitations exist in current imaging modalities Objective: We aimed to assess the clinical utility of 4D CT in detecting potential dynamic elbow disorders. Methods: Twenty-eight elbow joints from 26 patients with symptoms of dynamic elbow pathology were included in this study. They were first assessed by a senior orthopedic surgeon with subsequent qualitative data obtained via a Siemens Force Dual Source CT scanner (Erlangen, Germany), producing two- and three-dimensional “static” images and 4D dynamic “movie” images for assessment in each clinical scenario. Clinical assessment before and after scan was compared. Results: Use of 4D CT scan resulted in a change of diagnosis in 16 cases (57.14%). This included a change in primary diagnosis in 2 cases (7.14%) and secondary diagnosis in 14 cases (50%). In 25 cases (89.29%), the 4D CT scan allowed us to understand the pathological anatomy in greater detail which led to a change in the management plan of 15 cases (53.57%). Conclusion: 4D CT is a promising diagnostic tool in the management of dynamic elbow disorders and may be considered in clinical practice. Future studies need to compare it with other diagnostic modalities such as three-dimensional CT.

Purpose: The 4D computed tomography (CT) simulation is an essential procedure for tumors exhibiting breathing‐induced motion. However, to date there are no established guidelines to assess the characteristics of existing systems and to describe meaningful performance. We propose a commissioning quality assurance (QA) protocol consisting of measurements and acquisitions that assess the mechanical and computational operation for 4D CT with both phase and amplitude‐based reconstructions, for regular and irregular respiratory patterns. Methods: The 4D CT scans of a QUASAR motion phantom were acquired for both regular and irregular breathing patterns. The hardware consisted of the Canon Aquilion Exceed LB CT scanner used in conjunction with the Anzai laser motion monitoring system. The nominal machine performance and reconstruction were demonstrated with measurements using regular breathing patterns. For irregular breathing patterns the performance was quantified through the analysis of the target motion in the superior and inferior directions, and the volume of the internal target volume (ITV). Acquisitions were performed using multiple pitches and the reconstructions were performed using both phase and amplitude‐based binning. Results: The target was accurately captured during regular breathing. For the irregular breathing, the measured ITV exceeded the nominal ITV parameters in all scenarios, but all deviations were less than the reconstructed slice thickness. The mismatch between the nominal pitch and the actual breathing rate did not affect markedly the size of the ITV. Phase and normalized amplitude binning performed similarly. Conclusions: We demonstrated a framework for measuring and quantifying the initial performance of 4D CT simulation scans that can also be applied during periodic QAs. The regular breathing provided confidence that the hardware and the software between the systems performs adequately. The irregular breathing data suggest that the system may be expected to capture in excess the target motion and geometry, but the deviation is expected to be within the slice thickness. [ABSTRACT FROM AUTHOR]

Subclinical obstructive valve thrombosis after transcatheter aortic valve replacement (TAVR) is of uncertain frequency and clinical impact. The aim of this study was to determine the effects of apixaban vs standard of care on post-TAVR valve thrombosis detected by 4-dimensional (4D) computed tomography. The randomized ATLANTIS (Anti-Thrombotic Strategy to Lower All Cardiovascular and Neurologic Ischemic and Hemorrhagic Events After Trans-Aortic Valve Implantation for Aortic Stenosis) trial demonstrated that apixaban 5 mg twice daily was not superior to standard of care (vitamin K antagonists or antiplatelet therapy) after successful TAVR and was associated with similar safety but with more noncardiovascular deaths. Three months after randomization, 4D computed tomography was proposed to all patients to determine the percentage of patients with ≥1 prosthetic valve leaflet with grade 3 or 4 reduced leaflet motion or grade 3 or 4 hypoattenuated leaflet thickening (the primary endpoint) in the intention-to-treat population. Seven hundred sixty-two participants had complete multiphase datasets and were included in the 4D computed tomographic analysis. The primary endpoint occurred in 33 (8.9%) and 51 (13.0%) patients in the apixaban and standard-of-care groups, respectively. It was reduced with apixaban vs antiplatelet therapy (OR: 0.51; 95% CI: 0.30-0.86) but not vs vitamin K antagonists (OR: 1.80; 95% CI: 0.62-5.25) (P interaction = 0.037). The composite of death, myocardial infarction, any stroke, or systemic embolism at 1 year occurred in 10.7% (n = 9 of 84) and 7.1% (n = 48 of 178) of patients with and without subclinical valve thrombosis at 90 days, respectively (HR: 1.68; 95% CI: 0.82-3.44). Apixaban reduced subclinical obstructive valve thrombosis in the majority of patients who underwent TAVR without having an established indication for anticoagulation. This study was not powered for clinical outcomes. (Anti-Thrombotic Strategy After Trans-Aortic Valve Implantation for Aortic Stenosis [ATLANTIS]; NCT02664649) [Display omitted] [ABSTRACT FROM AUTHOR]

Background: Preoperative localization of parathyroid adenomas aids surgical planning for patients with hyperparathyroidism. This study explores the diagnostic accuracy of surgeon-reviewed 4D computed tomography (4D CT) scans for localization of parathyroid adenomas., Methods: A retrospective review of 95 patients with hyperparathyroidism who underwent parathyroidectomy at a tertiary care center was performed. The sensitivity, specificity, positive and negative predictive values, accuracy of identifying abnormal glands by surgeon, and interrater reliability between two head and neck surgeons was assessed., Results: The sensitivity of surgeon localization of all glands was 71% (95% CI, 63%-78%), improving to 76% when combined with radiology reads. The specificity was 98% (95% CI, 95%-99%), the positive predictive value was 95% (95% CI, 90%-99%), and the negative predictive value was 84% (95% CI, 79%-88%) for all abnormal glands. Interrater reliability between surgeons was κ = 0.771., Conclusions: The diagnostic accuracy of surgeon localization of abnormal glands on the 4D CT scan was substantial. Improvement with radiology report integration highlights the benefits of multidisciplinary collaboration. Interrater reliability between two fellowship-trained surgeons was moderate. These findings support the importance of surgeons developing proficiency in reading 4D CT scans to engage in interdisciplinary communication and improve patient outcomes., (© 2024 The Author(s). Head & Neck published by Wiley Periodicals LLC.)

• Cardiorespiratory ITV generated using cardiac-gated and respiratory-gated 4DCT. • Cardiorespiratory motions lead to an important increase of target volume in cardiac radioablation. • Combining 2 cardiac phases with 10 respiratory phases is a robust approach. • Using a single cardiac phase with our without fixed margin is a suboptimal approach. To evaluate different approaches for generating a cardiorespiratory ITV for cardiac radioablation. Four patients with ventricular tachycardia were included in this study. For each patient, cardiac-gated and respiration-correlated 4D-CT scans were acquired. The cardiorespiratory ITV was defined using registrations of the cardiac and respiratory 4D-CT images. Five different approaches, which differed in the number of incorporated cardiac phases (1, 2, 10, or 1 with a fixed 3 mm margin (FM) expansion) and respiratory phases (2 or 10), were evaluated. For each approach, a VMAT treatment plan was simulated. Target coverage (TC) and spill were evaluated geometrically and dosimetrically for each approach. When employing one cardiac phase, the TC did not exceed 85%. Using the two extreme phases of the cardiac and respiratory cycles resulted in a geometric TC < 88% for two patients, with a dosimetric TC of 83% for one patient. An acceptable TC for all patients (geometric TC > 89%, dosimetric TC > 92%) was only achieved when combining 10 respiratory phases with either 2 or 10 cardiac phases or a single cardiac phase with FM. The use of a single cardiac phase with FM combined with 10 respiratory phases lead to a mean geometric and dosimetric spill of 43% and 35%, respectively. For cardiac radioablation, the use of two extreme cardiac phases combined with 10 respiratory phases is a robust approach to generate a cardiorespiratory ITV. The use of a single cardiac phase with or without fixed margin expansion is not recommended based on this study. [ABSTRACT FROM AUTHOR]

Abstract Background Early detection of scapholunate ligament (SLL) tears is essential after minor and major trauma to the wrist. The differentiation between stable and instable injuries determines therapeutic measures which aim to prevent osteoarthritis. Arthroscopy has since been the diagnostic gold standard in suspected SLL tears because non-invasive methods have failed to exclude instable injuries reliably. This prospective study aims to determine the diagnostic accuracy of dynamic, 4D computed tomography (CT) of the wrist for diagnosing instable SLL tears. Methods Single center, prospective trial including 40 patients with suspected SLL tears scheduled for arthroscopy. Diagnostic accuracy of 4D CT will be tested against the reference standard arthroscopy. Radiologists will be blinded to the results of arthroscopy and hand surgeons to radiological reports. A historical cohort of 80 patients which was diagnosed using cineradiography before implementation of 4D CT at the study site will serve as a comparative group. Discussion Static imaging lacks the ability to detect instable SLL tears after wrist trauma. Dynamic methods such as cineradiography and dynamic magnetic resonance imaging (MRI) are complex and require specific technical infrastructure in specialized centers. Modern super-fast dual source CT scanners are gaining popularity and are being installed gradually in hospitals and ambulances. These scanners enable dynamic imaging in a quick and simple manner. Establishment of dynamic 4D CT of the wrist in patients with suspected SLL tears in in- and outpatient settings could improve early detection rates. Reliable identification of instable injuries through 4D CT scans might reduce the number of unnecessary diagnostic arthroscopies in the future. Trial registration This study was registered prospectively at the German Clinical Trials Register (DRKS) DRKS00021110 . Universal Trial Number (WHO-UTN): U1111–1249-7884.

Background and purposeThe impact of audiovisual (AV) biofeedback on four dimensional (4D) positron emission tomography (PET) and 4D computed tomography (CT) image quality was investigated in a prospective clinical trial (NCT01172041).Material and methods4D-PET and 4D-CT images of ten lung cancer patients were acquired with AV biofeedback (AV) and free breathing (FB). The 4D-PET images were analyzed for motion artifacts by comparing 4D to 3D PET for gross tumor volumes (GTVPET) and maximum standardized uptake values (SUVmax). The 4D-CT images were analyzed for artifacts by comparing normalized cross correlation-based scores (NCCS) and quantifying a visual assessment score (VAS). A Wilcoxon signed-ranks test was used for statistical testing.ResultsThe impact of AV biofeedback varied widely. Overall, the 3D to 4D decrease of GTVPET was 1.2±1.3cm(3) with AV and 0.6±1.8cm(3) for FB. The 4D-PET increase of SUVmax was 1.3±0.9 with AV and 1.3±0.8 for FB. The 4D-CT NCCS were 0.65±0.27 with AV and 0.60±0.32 for FB (p=0.08). The 4D-CT VAS was 0.0±2.7.ConclusionThis study demonstrated a high patient dependence on the use of AV biofeedback to reduce motion artifacts in 4D imaging. None of the hypotheses tested were statistically significant. Future development of AV biofeedback will focus on optimizing the human-computer interface and including patient training sessions for improved comprehension and compliance.

• The 4D CT failed to represent the motion characteristic during dose delivery. • Quantify the amplitude changes of respiratory motion based on intra-fractional CBCT. • Quantify the baseline drift of respiratory motion based on intra-fractional CBCT. • The ITV to PTV margin should be 4.0 mm (LR), 7.0 mm (SI), and 4.0 mm (AP) to compensate for the baseline drifts. • The recalculated ITV to PTV margin was clinically acceptable based on dosimetric parameters. Using intra-fractional cone-beam CT (CBCT) to evaluate the amplitude changes and baseline shifts of respiratory motion in liver stereotactic body radiation therapy (SBRT). The amplitude changes and baseline shifts of respiratory motion for 24 liver patients were evaluated by the four-dimensional (4D) CT, inter- and intra-fractional CBCT. The difference of the average liver position errors among all treatment fractions and the 4D CT representthe baseline shifts. According to the baseline shifts, the ITV to PTV margin was recalculated and the plan was re-designed to compare the dosimetric variation. The systematic and random errors of the baseline shifts for intra-fractional CBCT in the left–right (LR), superior-inferior (SI), and anterior-posterior (AP) directions were 0.99/1.60 mm, 2.03/2.46 mm, and 1.02/2.07 mm, respectively. The new ITV to PTV margins should be 4.0 mm, 7.0 mm, and 4.0 mm, respectively. The amplitude change of motion between the 4D CT and the intra-fractional CBCT was 1.03 ± 4.35 mm, with 31% of fractions exceeding 5 mm. To achieve the same dose coverage of the new PTV, the D mean , V50, V40, V30, V25 of normal liver and maximum dose of the duodenum were significantly different. Significant amplitude changes and baseline shifts of motion occurred during dose delivery compared with those in 4D CT. Using the ITV to PTV margin of 4.0 mm (LR), 7.0 mm (SI), and 4.0 mm (AP) can ensure the target dose coverage and keep the dose constrain of normal tissues at an acceptable level. [ABSTRACT FROM AUTHOR]

Background: Previous studies have discussed the diagnostic value of four dimensional kinematic CT in cases of carpal instabilities. This analysis compares calculated skin doses of 4D CT and conventional cineradiography of the wrist in cases of suspected SLL rupture. Methods: Retrospective calculation and interpolation of skin doses and effective doses for ten consecutive 4D CT examinations and 41 cineradiographies for suspected lesions of the scapholunate ligament. Standardised anterior-posterior and lateral cine sequences using a flat-panel digital subtraction imager and of 4D kinematic CT using a dual-source scanner were acquired and acquisition parameters recorded. We tested if the skin dose of 4D CT is different from cineradiography. Results: Median dose area product (DAP) of cineradiography was 135.34 cGycm2 resulting in a calculated median skin dose of 32.6 mSv (confidence interval 26.86–42.90 mSv) and an estimated effective skin dose of 3.26 µSv. CT dose index (CTDI) for 4D examinations was recorded to be 26.79 mGy and the dose-length product (DLP) was 150 mGy × cm. This resulted in an estimated skin dose of 34 mSv, which is covered by the confidence interval of cineradiography, and an effective skin dose of 3.4 µSv. Conclusions: Skin dose calculations are comparable for 2D cineradiography in two plains and 4D kinematic CT of the wrist. Calculated effective doses are < 0.01 mSv. [ABSTRACT FROM AUTHOR]

Ectopic and supernumerary parathyroid glands in the neck is a real surgical challenge especially in multi-gland pathologies. We report a supernumerary ectopic gland at a rare site in the neck in a chronic kidney disease patient which required a re-exploration following a deceptively successful bilateral neck dissection. [ABSTRACT FROM AUTHOR]

Purpose: Manual delineation on all breathing phases of lung cancer 4D CT image datasets can be challenging, exhaustive, and prone to subjective errors because of both the large number of images in the datasets and variations in the spatial location of tumors secondary to respiratory motion. The purpose of this work is to present a new deep learning‐based framework for fast and accurate segmentation of lung tumors on 4D CT image sets. Methods: The proposed DL framework leverages motion region convolutional neural network (R‐CNN). Through integration of global and local motion estimation network architectures, the network can learn both major and minor changes caused by tumor motion. Our network design first extracts tumor motion information by feeding 4D CT images with consecutive phases into an integrated backbone network architecture, locating volume‐of‐interest (VOIs) via a regional proposal network and removing irrelevant information via a regional convolutional neural network. Extracted motion information is then advanced into the subsequent global and local motion head network architecture to predict corresponding deformation vector fields (DVFs) and further adjust tumor VOIs. Binary masks of tumors are then segmented within adjusted VOIs via a mask head. A self‐attention strategy is incorporated in the mask head network to remove any noisy features that might impact segmentation performance. We performed two sets of experiments. In the first experiment, a five‐fold cross‐validation on 20 4D CT datasets, each consisting of 10 breathing phases (i.e., 200 3D image volumes in total). The network performance was also evaluated on an additional unseen 200 3D images volumes from 20 hold‐out 4D CT datasets. In the second experiment, we trained another model with 40 patients' 4D CT datasets from experiment 1 and evaluated on additional unseen nine patients' 4D CT datasets. The Dice similarity coefficient (DSC), center of mass distance (CMD), 95th percentile Hausdorff distance (HD95), mean surface distance (MSD), and volume difference (VD) between the manual and segmented tumor contour were computed to evaluate tumor detection and segmentation accuracy. The performance of our method was quantitatively evaluated against four different methods (VoxelMorph, U‐Net, network without global and local networks, and network without attention gate strategy) across all evaluation metrics through a paired t‐test. Results: The proposed fully automated DL method yielded good overall agreement with the ground truth for contoured tumor volume and segmentation accuracy. Our model yielded significantly better values of evaluation metrics (p < 0.05) than all four competing methods in both experiments. On hold‐out datasets of experiment 1 and 2, our method yielded DSC of 0.86 and 0.90 compared to 0.82 and 0.87, 0.75 and 0.83, 081 and 0.89, and 0.81 and 0.89 yielded by VoxelMorph, U‐Net, network without global and local networks, and networks without attention gate strategy. Tumor VD between ground truth and our method was the smallest with the value of 0.50 compared to 0.99, 1.01, 0.92, and 0.93 for between ground truth and VoxelMorph, U‐Net, network without global and local networks, and networks without attention gate strategy, respectively. Conclusions: Our proposed DL framework of tumor segmentation on lung cancer 4D CT datasets demonstrates a significant promise for fully automated delineation. The promising results of this work provide impetus for its integration into the 4D CT treatment planning workflow to improve the accuracy and efficiency of lung radiotherapy. [ABSTRACT FROM AUTHOR]

Background: Intraoperative scintigraphy (IoS) has been proposed as a tool for real‐time intraoperative decision‐making regarding parathyroid adenoma localization and confirmation of excision. Methods: Retrospective review of patients who underwent minimally invasive parathyroidectomies with scintigraphy performed intraoperatively. Preoperative neck ultrasound, 4D computed tomography, as well as intraoperative parathyroid hormone (IOPTH) and gamma probe measurements were conducted per standard practice. IoS images were obtained prior to and following parathyroid excision. Cases were reviewed to determine accuracy of IoS for localizing parathyroid pathology and confirming successful excision. Results: Fifty‐six cases met the inclusion criteria. Twenty‐nine patients (51.8%) showed confirmation of excision of an abnormal gland on post‐excision IoS. There were no significant differences in IOPTH reduction and postoperative laboratory values between patients with IoS‐identified resolution and those without IoS‐identified resolution. Conclusions: With low accuracy in correctly localizing abnormal glands and confirming their excision, there is no appreciable benefit of IoS at this time. [ABSTRACT FROM AUTHOR]

Purpose: For mobile lung tumors, four‐dimensional computer tomography (4D CT) is often used for simulation and treatment planning. Localization accuracy remains a challenge in lung stereotactic body radiation therapy (SBRT) treatments. An attractive image guidance method to increase localization accuracy is 4D cone‐beam CT (CBCT) as it allows for visualization of tumor motion with reduced motion artifacts. However, acquisition and reconstruction of 4D CBCT differ from that of 4D CT. This study evaluates the discrepancies between the reconstructed motion of 4D CBCT and 4D CT imaging over a wide range of sine target motion parameters and patient waveforms. Methods: A thorax motion phantom was used to examine 24 sine motions with varying amplitudes and cycle times and seven patient waveforms. Each programmed motion was imaged using 4D CT and 4D CBCT. The images were processed to auto segment the target. For sine motion, the target centroid at each phase was fitted to a sinusoidal curve to evaluate equivalence in amplitude between the two imaging modalities. The patient waveform motion was evaluated based on the average 4D data sets. Results: The mean difference and root‐mean‐square‐error between the two modalities for sine motion were −0.35 ± 0.22 and 0.60 mm, respectively, with 4D CBCT slightly overestimating amplitude compared with 4D CT. The two imaging methods were determined to be significantly equivalent within ±1 mm based on two one‐sided t tests (p < 0.001). For patient‐specific motion, the mean difference was 1.5 ± 2.1 (0.8 ± 0.6 without outlier), 0.4 ± 0.3, and 0.8 ± 0.6 mm for superior/inferior (SI), anterior/posterior (AP), and left/right (LR), respectively. Conclusion: In cases where 4D CT is used to image mobile tumors, 4D CBCT is an attractive localization method due to its assessment of motion with respect to 4D CT, particularly for lung SBRT treatments where accuracy is paramount. [ABSTRACT FROM AUTHOR]

Respiratory motion of the human body remains a major challenge in procedures for percutaneous puncture intervention. A solution is to develop a respiratory motion model. The aim of this study is to construct a respiratory motion model that can accommodate extreme respiratory conditions. Principal component analysis (PCA) and the support vector regression (SVR) method were employed as the framework to build the respiratory motion model. In the first stage, internal respiratory signals and respiratory surrogate signals are extracted. In the second stage, the respiratory motion model based on SVR is established. This study proposes a unique data augmentation method to improve the model robustness and the corresponding response capacity under extreme respiratory conditions. Finally, relevant evaluation indicators are used to evaluate the motion prediction accuracy of a reference model and the model in this study. When estimating the motion of the end-inspiratory phase (T00), the mean target registration error (TRE) of the motion estimate of the model after data augmentation was 1.28 ± 0.24 mm, while that of the model before data augmentation and that of the reference model were 1.67 ± 0.55 mm and 2.29 ± 1.06 mm, respectively. When estimating the motion of all phases, the mean TRE of the model after data augmentation was 1.26 ± 0.23 mm, which was also lower than that of the model before data augmentation. The data augmentation method improves the accuracy of the model and is statistically significant. Displaying excellent performance under extrapolation conditions, the proposed model effectively improves both accuracy and robustness. [ABSTRACT FROM AUTHOR]

Aims and Objectives: The influence of target motion on the reconstructed internal target volume (ITV) for device-based (DB) external surrogate system and Smart deviceless (DL) 4-dimensional (4D) system were compared in a controlled phantom experiment. The volumetric changes in reconstructed ITVs from the average intensity projection (AveIP) images using DB method (Anzai Respiratory Gating System, ANZAI MEDICAL CO., LTD, Japan) and DL method (Smart deviceless 4D system by GE Medical Systems (Chicago, USA)) with the theoretical true volume (ITVth) for moving target with the increasing target motion in anterior-posterior (A-P), lateral (left-right [L-R]) and inferior-superior (S-I) directions were assessed. Materials and Methods: 4D computed tomography (4DCT) of CIRS dynamic phantom (Computerized Imaging Reference Systems Inc., Norfolk, VA, USA) with 2.5 cm diameter spherical target of volume 8.2 cc programmed to move in a cos4(x) motion pattern placed in the lung volume were acquired for various target motion pattern using DB and DL method of gating. AveIP images of 10 phase binned image sets were generated and ITVs were delineated. Results: The maximum absolute percent differences between ITVaveand ITVthfor DL and DB methods were 15.91% and 4.94 % respectively for target motion of 5 mm in AP with 15 mm S-I direction. When the S-I motion was decreased to 10 mm, the observed % difference of the ITVs were also decreased to 12.5% and 0.3% for DL and DB method. When the lateral [L-R] motion was varied from 0 mm to 5 mm for S-I motion of 5 mm to 15 mm, the differences in the ITVs were significant (P = 0.004) with the maximum absolute percent difference of 18.61% and 4.94 % for DL and DB gating. With the simultaneous motion of the target in all the 3 directions, the difference in the reconstructed ITVs were statistically significant for DL method (P = 0.0002) and insignificant for DB method (P = 0.06) with an average increase of 10% in ITVDL against 2% in the ITVDB. The difference in ITVDL was significant for the target motion above 3 mm in A-P and L-R directions for S-I movement of above 10 mm (P = 0.0002). However, for low excursions of the target movement, no significant difference in the ITVs were observed (P > 0.06). In general, ITVDBs were closer to the ITVth (within 7.8%) than ITVDL (18.61%). Conclusion: The results showed that the DL method is an effective way of image sorting in 4D acquisition for smaller target excursion. When the target motion exceeds 3 mm in A-P and L-R directions with S-I more than 10 mm, DB method is the choice due to its accuracy in reproducing the absolute target volume.

Background: The advances in image guidance and capability of highly conformal dose deliveries made possible the use of helical tomotherapy (HT) for lung cancer treatment. To determine the effect of respiratory motion on the delivered dose in HT, film dosimetry using a dynamic phantom was performed. This was a phantom study to determine the effect of motion on the delivered dose in HT. Materials and methods: 4D computed tomography (4DCT) was acquired for various target motions of CIRS dynamic phantom (CIRS Inc., Norfolk, USA) with 2.5cm diameter spherical target of volume 8.2 cc moving in the COS4 motion pattern. AveIP images and treatment plans were generated in the HT planning system. Target excursions during treatment delivery were changed in the superior-inferior, anteroposterior and lateral directions. The breathing cycle time was varied from 4 to 5 sec. and also the delivery interruptions were introduced. A film was exposed for each delivery and gamma analysis was performed. Results: The gamma pass rate (GPR) with 3%, 2 mm criteria for the target motion in the S-I direction showed a significant reduction from 97.5% to 54.4% as the motion increased from 3 mm to 8 mm (p = 0.03). For the target motion in S-I = 8 mm, L-R = A-P = 3 mm, the percentage decrease in the GPR was 74% (p = 0.001) for three interruptions. Conclusion: The ITV based approach in HT is ideal for a shallow breathing situation when the tumor excursions were confined to 5 mm in the S-I and 3 mm in L-R and A-P directions. [ABSTRACT FROM AUTHOR]

La radiothérapie stéréotaxique pulmonaire est réalisée dans l'équipe du centre Georges-François-Leclerc (CGFL) à Dijon depuis 2008 sur un accélérateur Truebeam® (Varian®) avec la technique RPM. Cinquante patients atteints d'un cancer bronchique primitif de stade T1–T2 (n = 30) ou une métastase bronchique (n = 20) ont été inclus dans l'étude. Depuis 2014, trois scanographies quadridimensionnelles successives à j1, j2 et j3, sont réalisées afin de s'assurer de la reproductibilité des ITV (Internet Target Volume). Les trois ITV sont délinéés (ITV 1,2 et 3) à partir de la MIP (Maximum Intensity Projection) de chacune des trois scanographies. Un ITV global est créé à partir des ITV des trois scanographies (fusion des MIP2 et 3 avec la MIP1). Une CBCT (Cone Beam Computerised Tomography) est réalisée au début de chaque séance d'irradiation pour positionner le patient. L'étude consistait à analyser la pertinence de la réalisation de trois scanographies différentes avant la dosimétrie pour définir l'ITV et à comparer les volumes délinéés sur les différentes CBCT à l'ITV pour s'assurer que le volume tumoral est bien inclus dans l'ITV au cours des séances. Il existe une forte corrélation entre les différents ITV 1, 2, 3 et global, ainsi qu'entre les volumes obtenus sur les différentes CBCT (p = 0,977). Le coefficient de corrélation entre les différents ITV et les volumes délinéés sur CBCT était élevé pour les lésions lobaires supérieures. En termes de tolérance, le VEMS (volume maximal expiré pendant la première seconde) ne semblait pas être un facteur significatif influant sur la corrélation entre les ITV et les volumes délinées sur CBCT. La réalisation d'une seule scanographie de centrage quadridimensionnelle est suffisante pour envisager une irradiation stéréotaxique pulmonaire, quelle que soit la localisation des lésions pulmonaires. Le coefficient de corrélation entre les ITV et les CBCT était élevé pour les lésions lobaires supérieures. Stereotactic lung radiosurgery has been carried out in the team at the Georges-François-Leclerc centre (CGFL) in Dijon since 2008 on a Truebeam® accelerator (Varian®) with the RPM technique. Fifty patients with primary T1–T2 stage lung cancer (n = 30) or lung metastasis (n = 20) were included in the study. Since 2014, 3 successive 4D scanners on D1, D2 and D3, have been produced in order to ensure the reproducibility of ITV (Internet Target Volume). The 3 ITVs are contoured (ITV 1, 2 and 3) from the MIP (Maximum Intensity Projection) of each of the 3 scanners. A global ITV is created from the ITV volumes of the 3 scanners (MIP 2 and 3 merged with MIP 1). A CBCT (Cone Beam Computerised Tomography) is performed at the start of each irradiation session to position the patient. The study consisted in analysing the relevance of the realisation of 3 different scanners before dosimetry to define the ITV and in comparing the volumes contoured on the different CBCT to the ITV to make sure that the tumour volume is well included in the ITV during the sessions. There is a strong correlation between the different ITVs 1, 2, 3 and global, as well as between the volumes obtained on the different CBCTs. The correlation coefficient between the different ITVs and the volumes contoured on CBCT was high for upper lobar lesions. In terms of tolerance, the FEV1 (Maximum volume expired during the first second) did not seem to be a significant factor influencing the correlation between the ITV and the volumes bypassed on CBCT. Performing a single 4D planification CT is sufficient to consider stereotactic lung irradiation, regardless of the location of the lung lesions. The correlation coefficient between ITV and CBCT was high for upper lobar lesions. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the effect of breathing motion on dose distribution for hepatocellular carcinoma (HCC) patients using four‐dimensional (4D) CT and deformable registration. Methods: Fifty HCC patients who were going to receive radiotherapy were enrolled in this study. All patients had been treated with transarterial chemoembolization beforehand. Three‐dimensional (3D) and 4D CT scans in free breathing were acquired sequentially. Volumetric modulated arc therapy (VMAT) was planned on the 3D CT images and maximum intensity projection (MIP) images. Thus, the 3D dose (Dose‐3D) and MIP dose (Dose‐MIP) were obtained, respectively. Then, the Dose‐3D and Dose‐MIP were recalculated on 10 phases of 4D CT images, respectively, in which the end‐inhale and end‐exhale phase doses were defined as Dose‐3D‐EI, Dose‐3D‐EE, Dose‐MIP‐EI, and Dose‐MIP‐EE. The 4D dose (Dose‐4D‐3D and Dose‐4D‐MIP) were obtained by deforming 10 phase doses to the end‐exhale CT to accumulate. The dosimetric difference in Dose‐3D, Dose‐EI3D, Dose‐EE3D, Dose‐4D‐3D, Dose‐MIP, Dose‐EIMIP, Dose‐EEMIP, and Dose‐4D‐MIP were compared to evaluate the motion effect on dose delivery to the planning target volume (PTV) and normal liver. Results: Compared with Dose‐3D, PTV D99 in Dose‐EI3D, Dose‐EE3D and Dose‐4D‐3D decreased by an average of 6.02%, 1.32%, 2.43%, respectively (P < 0.05); while PTV D95 decreased by an average of 3.34%, 1.51%, 1.93%, respectively (P < 0.05). However, CI and HI of the PTV in Dose‐3D was superior to the other three distributions (P < 0.05). There was no significant differences for the PTV between Dose‐EI and Dose‐EE, and between the two extreme phase doses and Dose‐4D (P> 0.05). Negligible difference was observed for normal liver in all dose distributions (P> 0.05). Conclusions: Four‐dimensional dose calculations potentially ensure target volume coverage when breathing motion may affect the dose distribution. Dose escalation can be considered to improve the local control of HCC on the basis of accurately predicting the probability of radiation‐induced liver disease. [ABSTRACT FROM AUTHOR]

Background: Early detection of scapholunate ligament (SLL) tears is essential after minor and major trauma to the wrist. The differentiation between stable and instable injuries determines therapeutic measures which aim to prevent osteoarthritis. Arthroscopy has since been the diagnostic gold standard in suspected SLL tears because non-invasive methods have failed to exclude instable injuries reliably. This prospective study aims to determine the diagnostic accuracy of dynamic, 4D computed tomography (CT) of the wrist for diagnosing instable SLL tears.Methods: Single center, prospective trial including 40 patients with suspected SLL tears scheduled for arthroscopy. Diagnostic accuracy of 4D CT will be tested against the reference standard arthroscopy. Radiologists will be blinded to the results of arthroscopy and hand surgeons to radiological reports. A historical cohort of 80 patients which was diagnosed using cineradiography before implementation of 4D CT at the study site will serve as a comparative group.Discussion: Static imaging lacks the ability to detect instable SLL tears after wrist trauma. Dynamic methods such as cineradiography and dynamic magnetic resonance imaging (MRI) are complex and require specific technical infrastructure in specialized centers. Modern super-fast dual source CT scanners are gaining popularity and are being installed gradually in hospitals and ambulances. These scanners enable dynamic imaging in a quick and simple manner. Establishment of dynamic 4D CT of the wrist in patients with suspected SLL tears in in- and outpatient settings could improve early detection rates. Reliable identification of instable injuries through 4D CT scans might reduce the number of unnecessary diagnostic arthroscopies in the future.Trial Registration: This study was registered prospectively at the German Clinical Trials Register (DRKS) DRKS00021110 . Universal Trial Number (WHO-UTN): U1111-1249-7884. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the impact of respiratory motion in the treatment margins for lung SBRT frameless treatments and to validate our treatment margins using 4D CBCT data analysis. Methods: Two hundred and twenty nine fractions with early stage NSCLC were retrospectively analyzed. All patients were treated in frameless and free breathing conditions. The treatment margins were calculated according to van Herk equation in Mid‐Ventilation. For each fraction, three 4D CBCT scans, pre‐ and postcorrection, and posttreatment, were acquired to assess target baseline shift, target localization accuracy and intra‐fraction motion errors. A bootstrap analysis was performed to assess the minimum number of patients required to define treatment margins. Results: The retrospectively calculated target‐baseline shift, target localization accuracy and intra‐fraction motion errors agreed with the literature. The best tailored margins to our cohort of patients were retrospectively computed and resulted in agreement with already published data. The bootstrap analysis showed that fifteen patients were enough to assess treatment margins. Conclusions: The treatment margins applied to our patient's cohort resulted in good agreement with the retrospectively calculated margins based on 4D CBCT data. Moreover, the bootstrap analysis revealed to be a promising method to verify the reliability of the applied treatment margins for safe lung SBRT delivery. [ABSTRACT FROM AUTHOR]

Aim: To mimic chest compression during cardiopulmonary resuscitation (CPR), this study aimed to produce time-resolved 3D (volumetric) reformats of thoracic and upper abdominal tissue movement during incremental closed chest compression/decompression from 0 to 8 to 0 cm.Methods: Sequential angiography enhanced computed tomography (CT) scans were acquired from a recently deceased, consented adult cadaver with 1 cm incremental closed chest compression/decompression. Three compression/decompression sequences from 0 to 3 cm, 0 to 5 cm, and 0 to 8 cm, respectively, were scanned using a radio-opaque, manually operated, chest compression device. The multiphase volumetric data sets were compiled into 4D models that allowed for multiplanar reformatted and volume rendered image manipulation.Results: Time-resolved volumetric (4D) models were produced using freeware to post-process the static CT scans. The 4D models allowed the study of simulated thoracic and upper abdominal content movement during closed chest compression.Conclusions: The method described could assist CPR researchers and educators in the development and demonstration of effective CPR protocols. [ABSTRACT FROM AUTHOR]

Purpose: Four‐dimensional (4D) computed tomography (CT) imaging is an essential part of current 4D radiotherapy treatment planning workflows, but clinical 4D CT images are often affected by artifacts. The artifacts are mainly caused by breathing irregularity during data acquisition, which leads to projection data coverage issues for currently available commercial 4D CT protocols. It was proposed to improve projection data coverage by online respiratory signal analysis and signal‐guided CT tube control, but related work was always theoretical and presented as pure in silico studies. The present work demonstrates a first CT prototype implementation along with respective phantom measurements for the recently introduced intelligent 4D CT (i4DCT) sequence scanning concept (https://doi.org/10.1002/mp.13632). Methods: Intelligent 4D CT was implemented on the Siemens SOMATOM go platform. Four‐dimensional CT measurements were performed using the CIRS motion phantom. Motion curves were programmed to systematically vary from regular to very irregular, covering typical irregular patterns that are known to result in image artifacts using standard 4D CT imaging protocols. Corresponding measurements were performed using i4DCT and routine spiral 4D CT with similar imaging parameters (e.g., mAs setting and gantry rotation time, retrospective ten‐phase reconstruction) to allow for a direct comparison of the image data. Results: Following technological implementation of i4DCT on the clinical CT scanner platform, 4D CT motion artifacts were significantly reduced for all investigated levels of breathing irregularity when compared to routine spiral 4D CT scanning. Conclusions: The present study confirms feasibility of fully automated respiratory signal‐guided 4D CT scanning by means of a first implementation of i4DCT on a CT scanner. The measurements thereby support the conclusions of respective in silico studies and demonstrate that respiratory signal‐guided 4D CT (here: i4DCT) is ready for integration into clinical CT scanners. [ABSTRACT FROM AUTHOR]

Parathyroid carcinoma is a rare tumor associated with significantly high levels of parathyroid hormone (PTH) and primary hyperparathyroidism (HPT) and is difficult to distinguish from parathyroid adenoma, which is a much more common cause of HPT. Parathyromatosis is a rare condition in which several nodules of hyperfunctioning parathyroid tissue form in the neck and mediastinum, and it presents as recurrent hyperparathyroidism. We describe the case of a 44-year-old woman with recurrent hyperparathyroidism who presented with hypercalcemic crisis and biochemical investigations showed a severely raised serum intact parathyroid hormone (iPTH) level of 2513 pg/ml and serum calcium level of 17 mg/dl. A four-dimensional computed tomography (4D CT) of the neck was done, which showed few arterially enhancing nodular lesions in the right paratracheal and retrotracheal location at the level of thoracic inlet showing washout in delayed images suggestive of recurrent/residual parathyroid lesions. A technetium-99 m methoxyisobutylisonitrile (Tc-99 m MIBI) scan was done, and the planar neck anterior early images showed an area of increased radiotracer uptake in the right lower neck region with persistent uptake in the delayed images. Single photon emission computed tomography/ computed tomography (SPECT/CT) images showed a soft-tissue lesion in the right paratracheal region at the level of C7 vertebra showing increased radiotracer uptake suggestive of a recurrent/residual parathyroid lesion. Exploration and excision of the recurrent parathyroid mass was planned, and the right paratracheal mass with nodes above the aortic arch along with the subcutaneous and intramuscular lesions were excised. Postoperative serum calcium was 7.8 mg/dl, and serum iPTH was 135 pg/ml. Histopathological examination of the excised tissue showed the features of parathyroid carcinoma. Thus, Tc-99 m MIBI scan and 4D CT were critical in evaluating this case of parathyroid carcinoma with recurrent hyperparathyroidism and planning its management. [ABSTRACT FROM AUTHOR]

To solve the problem that traditional image registration methods based on continuous optimization for large motion lung 4D CT image sequences are easy to fall into local optimal solutions and lead to serious misregistration, a novel image registration method based on high-order Markov Random Field (MRF) is proposed. By analyzing the effect of the deformation field constraint of the potential functions with different order cliques in MRF model, energy functions with high-order cliques form are designed separately for 2D and 3D images to preserve topology of the deformation field. In order to preserve the topology of the deformation field more effectively, it is necessary to apply a smooth term and a topology preservation term simultaneously in the energy function and use logarithmic function to impose a penalty on the Jacobian matrix with high-order cliques in the topology preservation term. For the complexity of the designed energy function with high-order cliques form, Markov Chain Monte Carlo (MCMC) algorithm is used to solve the optimization problem of the designed energy function. To address the high computational requirements in lung 4D CT image registration, a multi-level processing strategy is adopted to reduce the space complexity of the proposed registration method and promotes the computational efficiency. In the DIR-lab dataset with 4D CT images and the COPD (Chronic Obstructive Pulmonary Disease) dataset with 3D CT images, the average target registration error (TRE) of our proposed method can reach 0.95 mm respectively. [ABSTRACT FROM AUTHOR]

Observation of dynamic testing by means of X-ray computed tomography (CT) and in-situ loading devices has proven its importance in material analysis already, yielding detailed 3D information on the internal structure of the object of interest and its changes during the experiment. However, the acquisition of the tomographic projections is, in general, a time-consuming task. The standard method for such experiments is the time-lapse CT, where the loading is suspended for the CT scan. On the other hand, modern X-ray tubes and detectors allow for shorter exposure times with an acceptable image quality. Consequently, the experiment can be designed in a way so that the mechanical test is running continuously, as well as the rotational platform, and the radiographic projections are taken one after another in a fast, free-running mode. Performing this so-called on-the-fly CT, the time for the experiment can be reduced substantially, compared to the time-lapse CT. In this paper, the advanced pore morphology (APM) foam elements were used as the test objects for in-situ X-ray microtomography experiments, during which series of CT scans were acquired, each with the duration of 12 s. The contrast-to-noise ratio and the full-width-half-maximum parameters are used for the quality assessment of the resultant 3D models. A comparison to the 3D models obtained by time-lapse CT is provided.

This study deals with comparison of conventional and 4D CT (GE Lightspeed) planning on the tumour control probability (TCP), using the TCP model of the AAPM-Report Task Group 166. In the first step a VMAT treatment plan was calculated (Varian Eclipse 13.7) on basis of conventional CT data. This treatment plan was transferred to the complete 4D CT, which represents the tumour volume in motion. Due to the increased volume and the resulting decrease of tumour coverage the TCP went down from 97,6% to 91,2%. After adding an internal target volume (ITV, ICRU 62) to the conventional CT according to our clinical protocols (1,0 cm cc and 0,3 cm axial plane) the TCP increased to 98,0% when applying the conventional plan to the 4D CT. This finding demonstrates the need of 4D CT for moving tumours in chest and abdomen region.

We present a case of an ectopic mediastinal parathyroid adenoma in a 58-year-old male patient. We show how different imaging modalities were successfully used to reach a diagnosis. We particularly focus on the role of four-dimensional CT scan in preoperative localization of ectopic adenomas and discuss how diverse imaging modalities can be integrated in the workup of ectopic parathyroid adenomas.

Abstract Background Respiration-correlated CT (4D CT) is the basis of radiotherapy treatment planning of thoracic and abdominal tumors. Current clinical 4D CT images suffer, however, from artifacts due to unfulfilled assumptions concerning breathing pattern regularity. We propose and evaluate modifications to existing low-pitch spiral 4D CT reconstruction protocols to counteract respective artifacts. Methods The proposed advanced reconstruction (AR) approach consists of two steps that build on each other: (1) statistical analysis of the breathing signal recorded during CT data acquisition and extraction of a patient-specific reference breathing cycle for projection binning; (2) incorporation of an artifact measure into the reconstruction. 4D CT data of 30 patients were reconstructed by standard phase- and local amplitude-based reconstruction (PB, LAB) and compared with images obtained by AR. The number of artifacts was evaluated and artifact statistics correlated to breathing curve characteristics. Results AR reduced the number of 4D CT artifacts by 31% and 27% compared to PB and LAB; the reduction was most pronounced for irregular breathing curves. Conclusions We described a two-step optimization of low-pitch spiral 4D CT reconstruction to reduce artifacts in the presence of breathing irregularity and illustrated that the modifications to existing reconstruction solutions are effective in terms of artifact reduction.

Background Primary hyperparathyroidism is an endocrinopathy associated with dysregulated calcium homeostasis. The most common etiology is a parathyroid adenoma most definitely managed via a parathyroidectomy. The two main surgical approaches include a minimally invasive parathyroidectomy (MIP) and open four-gland exploration (4-GE). MIP is the preferred operative strategy since it is associated with less postoperative complications. Accurate preoperative imaging is essential in informing the optimal approach to surgery. MIP is only considered if adenoma is able to be localized precisely. The most commonly used imaging modality includes ultrasound and sestamibi single-photon emission computed tomography (SPECT)/CT, either as a single or combination strategy. Other options include MRI, PET, and 4D CT. There is no universally accepted preoperative imaging strategy. The literature is discordant and recommendations proposed by existing guidelines are incongruous. Objectives This study aimed to evaluate currently utilized preoperative parathyroid imaging modalities at our institution and correlate them with surgical and histological findings to determine the most efficient imaging strategy to detect adenomas for our patient cohort. This will ultimately guide the best surgical approach for patients receiving parathyroidectomies. Methods This is a retrospective observational study of all patients undergoing first-time surgery for biochemically proven primary hyperparathyroidism at our institution over the past five years. Multiple data points were collected including modality of preoperative disease localization, operation type, final histopathology, biochemical investigations, and cure rate. Patients were categorized into one of three groups based on the method of disease localization. Results A total of 244 patients had parathyroidectomies performed at our institution in the past five years from January 2018 to December 2022. Ninety-six percent (n=235) of all patients received dual imaging preoperatively with SPECT/CT and ultrasound performed on the same day and therefore included in this study. A total of 64.3% (n=151) underwent MIP. Eighty percent (n=188) of all histopathology revealed adenomas and 26.8% (n=63) of patients had adenoma localized on SPECT/CT only (sensitivity: 58.1%, specificity: 71%, and positive predictive value {PPV}: 85.7%). A total of 9.8% (n=23) had adenoma localized on ultrasound only (sensitivity: 15.6%, specificity: 73.3%, and PPV: 65.2%). A total of 45.1% (n=106) were dual localized on both SPECT/CT and ultrasound (sensitivity: 75.6%, specificity: 46.6%, and PPV: 84.9%). The cure rate was 91.5% in the dual-localized group, 86% in the dual-unlocalized group, and 96.5% when localized with SPECT/CT alone. Conclusion A dual-imaging modality with SPECT/CT and ultrasound should remain the first-line imaging strategy. This approach has higher sensitivity rates and poses no inherent patient or surgical-related risks. Patients with disease unlocalized on SPECT/CT alone had a positive predictive value, specificity, and likelihood ratio for adenoma detection comparable to dual-localized patients. Therefore, SPECT/CT alone is sufficient for directing MIP in the presence of a negative ultrasound., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2024, Vasandani et al.)