4DCT Research Articles

Early 6 months usage of single anTiplAtelet OR anTicoAgulant followed by single antiplatelet after transcatheter aortic valve replacement: protocol for a multicentre, open-label, randomised controlled clinical trial

IntroductionThe strategy for initiating antithrombotic therapy to prevent bioprosthetic valve thrombosis (BPVT) after transcatheter aortic valve replacement (TAVR) remains uncertain. There is still lacking evidence on the efficacy and safety...

Interplay Effect of Splenic Motion for Total Lymphoid Irradiation in Pediatric Proton Therapy.

(1) Background: The most significant cause of an unacceptable deviation from the planned dose during respiratory motion is the interplay effect. We examined the correlation between the magnitude of splenic motion and its impact on plan quality for total lymphoid irradiation (TLI); (2) Methods: Static and 4D CT images from ten patients were used for interplay effect simulations. Patients' original plans were optimized based on the average CT extracted from the 4D CT and planned with two posterior beams using scenario-based optimization (±3 mm of setup and ±3% of range uncertainty) and gradient matching at the level of mid-spleen. Dynamically accumulated 4D doses (interplay effect dose) were calculated based on the time-dependent delivery sequence of radiation fluence across all phases of the 4D CT. Dose volume parameters for each simulated treatment delivery were evaluated for plan quality; (3) Results: Peak-to-peak splenic motion (≤12 mm) was measured from the 4D CT of ten patients. Interplay effect simulations revealed that the ITV coverage of the spleen remained within the protocol tolerance for splenic motion, ≤8 mm. The D100% coverage for ITV spleen decreased from 95.0% (nominal plan) to 89.3% with 10 mm and 87.2% with 12 mm of splenic motion; (4) Conclusions: 4D plan evaluation and robust optimization may overcome problems associated with respiratory motion in proton TLI treatments. Patient-specific respiratory motion evaluations are essential to confirming adequate dosimetric coverage when proton therapy is utilized.

Dose reduction in sequence scanning 4D CT imaging through respiratory signal-guided tube current modulation: A feasibility study.

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. 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. 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. 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. 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.

FRI688 Efficacy Of 4D CT Scan And Tc-99m-MIBI-SPECT/CT For The Preoperative Localization Of Abnormal Parathyroid Glands In Patients With Primary Hyperparathyroidism

Abstract Disclosure: E. Zareva: None. V. Rivera-Hernandez: None. S. Salpekar: None. J. Moyo: None. M. Bilbatua: None. Z. Lauer: None. A. Zare: None. P. Kaur: None. M. Deshmukh: None. Background: Primary hyperparathyroidism is a common endocrine disorder that often requires surgical intervention for a cure. Accurate localization of abnormal parathyroid glands is critical for successful surgical treatment. NM Parathyroid scan with single-photon emission computed tomography(Tc99m-MIBI-SPECT/CT) is considered the gold standard, but other options like ultrasound, CT, MRI, and PET have been used. Accurate preoperative imaging has become even more critical with the development of focused surgical approaches. This study aims to evaluate the accuracy of Tc99m-MIBI-SPECT/CT and 4D CT scan in localizing abnormal parathyroid glands in our institution. Objectives: To evaluate and compare the efficacy of 4D CT scan and Tc99m-MIBI-SPECT/CT for the preoperative localization of abnormal parathyroid glands in patients with primary hyperparathyroidism in a single health network. Methods and Design: We collected data on 100 patients with biochemically confirmed primary hyperparathyroidism regarding age, sex, image modalities such asTc99m-MIBI-SPECT/CT and 4D CT before surgery, and the surgical pathology results. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were calculated for both imaging modalities. Results: A total of 100 patient charts were reviewed, including 77 females and 23 males (3.35:1 female to male ratio),with an average age of 65.9 years (standard deviation 12.59). 90 patients had undergone surgical resection. 54 (60%) of them were diagnosed as parathyroid adenoma; 30 (33.3%) as parathyroid hyperplasia; 1 (1.1%) malignant parathyroid carcinoma; 5 (5.5%) were normal. 84 patients underwent Tc99m-MIBI-SPECT/CT and97 patients - 4D CT. 4D CT scan had a sensitivity of 90.36% (95% CI,81.89%-95.75%) and specificity of 50.00% (95% CI, 6.76%-93.24%) and outperformed Tc99m-MIBI-SPECT/CT which had a sensitivity of 45.71% (95% CI,33.74%-58.06%) and specificity of 80.00% (95% CI, 28.36%-99.49%). 4D CT had a positive predictive value (PPV) of 97.40% (95% CI, 90.93%-99.68%) and a negative predictive value (NPV) of 20.01% (95% CI, 2.52%-55.62%) compared toTc99m-MIBI-SPECT/CT which had PPV of 96.95% (95% CI, 84.22%-99.92%) and NPV of9.57% (95% CI, 2.68%-22.68%). 4D CT also had higher accuracy (85.5%; 95% CI,79.87%-94.35%) compared to Tc99m-MIBI scan (48.01%; 95% CI,36.32%-59.86%). Conclusion: Diagnostic imaging plays a crucial role in the management of primary hyperparathyroidism. Among the patients who had Tc99m-MIBI-SPECT/CT, less than half had positive scans suggestive of abnormal parathyroid tissue. This highlights the need for additional imaging methods for patients with negative scans. 4D CT is widely used in our institution and is more effective than Tc99m-MIBI-SPECT/CT in the preoperative localization of abnormal parathyroid glands. Presentation: Friday, June 16, 2023

SAT187 A Case Of CDC73 Mutation Related Primary Hyperparathyroidism With Ectopic Parathyroid Hyperplasia

Abstract Disclosure: T. Wu: None. N. Dhir: None. M. Bollineni: None. Introduction: Primary hyperparathyroidism is the most common cause of hypercalcemia, and most cases are sporadic. However, in 5-10% cases, it may occur as a syndromic and hereditary disease, like Multiple endocrine neoplasia type 1, type 2A, type 4, or CDC73 mutation related hereditary benign or malignant hyperparathyroidism. In patients with severe or early onset primary hyperparathyroidism, screening for genetic etiology should be considered. Case Presentation: A 35-year-old woman with a medical history of hypertension, kidney stones, and post-operative hypothyroidism presented to the endocrinology clinic due to recurrent hyperparathyroidism. She initially had a parathyroidectomy in 2008 and her calcium corrected at that time. She was again diagnosed with hypercalcemia due to primary hyperparathyroidism in 2021. She underwent re-exploration and had a right thyroid lobectomy with removal of three parathyroid glands. Her PTH was still 309 pg/mL (9-77 pg/mL) and calcium was 11.2 mg/dL (8.6-10.5 mg/dL), and she was started on Cinacalcet. The patient continued to have elevated calcium, bone pain, fatigue, and constipation. A 4D CT scan was ordered, which localized activity to a 1.5 cm arterial enhancing nodule in the anterior mediastinum, with intrathymic location. She underwent right video-assisted thoracoscopic total thymectomy with en bloc and the nodule was found to be ectopic parathyroid tissue. Post-operatively, her calcium normalized to 8.6 mg/dL and PTH was undetectable. She underwent genetic testing due to her recurrent hyperparathyroidism, which showed a CDC73 mutation. She is currently on calcitriol and calcium supplements, and serum calcium has been maintained in the low-normal range. Discussion: The CDC73 gene encodes a protein called parafibromin, which acts as a tumor suppressor, prohibiting cells from proliferating. Mutations in this gene are linked to jaw-tumor syndrome, familial isolated primary hyperparathyroidism (FIHP), and parathyroid carcinoma. These three CDC73-related disorders are clinically overlapping and inherited in an autosomal dominant manner. Biallelic mutations of the CDC73 gene are associated with a high risk of parathyroid cancer since the parafibromin protein is usually absent in parathyroid carcinoma and occasionally in atypical adenomas. FIHP tends to have a more severe clinical presentation with earlier onset (younger than 45 years). Additionally, patients with CDC73 related disorders are more prone to developing ossifying fibroma(s) of the jaw, uterine tumors, and various renal lesions. In summary, this case highlights the diagnostic and therapeutic challenges in a patient with persistent primary hyperparathyroidism after a failed second surgery. Genetic testing is vital for early detection, surveillance, and familial genetic counseling in patients with CDC73 related disorders. Presentation: Saturday, June 17, 2023

New Data-Driven Gated (DDG) PET/CT for Radiation Treatment Planning of NSCLC

PET/CT for RT simulation of NSCLC is typically conducted in two separate imaging sessions of gated 4D-CT in radiation oncology and fusion with non-gated PET/CT in diagnostic imaging, making treatment response assessment (TRA) with PET/CT and radiation treatment planning (RTP) challenging. To remedy this short-coming, we designed a new data-driven gated (DDG) PET/CT, based on the self-gated PET and self-gated CT data to derive the gated PET/CT data free of tumor blurring and misregistration artifacts without any respiratory monitoring device (ease of use and cost reduction). The new DDG PET/CT also provides the important 4D-CT information of end-inspiratory (EI), end-expiratory (EE), maximum-intensity-projection (MIP) and average-intensity-projection (AIP) CT's. The total imaging time is < 15 min, which makes DDG PET/CT simulation in a single session without any respiratory monitoring device possible. Acquisition is standard PET/CT imaging protocol followed by a cine CT imaging of the tumor area. We utilized the commercial DDG PET from GE Discovery PET/CT and designed a new DDG CT for attenuation correction of the DDG PET for reduction of tumor motion and mis-registration. The AIP and MIP images were from the average and maximum pixel values of the cine CT images, respectively. The cine CT images with the largest and smallest average CT number in the lung region were identified as the EE and EI CT images, respectively. For the image slices without any lung region present, the largest and smallest expansions of the body outline contour were selected to be the EE and EI CT phases, respectively. The AIP and EE CT images were used for attenuation correction of the PET and DDG PET data, respectively. Both DDG PET/CT and 4D-CT of (EI, EE, AIP and MIP) are for RT simulation of NSCLC. 38 4D-CT patient data sets were compared at the EE and EI phases between our DDG CT and 4D-CT to demonstrate the applicability of the newly designed DDG CT. A prototype software on a Dell PC of i5-6500 CPU has been successfully developed to enable DDG PET/CT and 4D-CT on seven GE Discovery PET/CT scanners. The operating system was Ubuntu and the computer language was Python. In the EE phase, the images selected by DDG CT and 4D CT were identical 62.5±21.6% of the time. In the EI phase, the images selected by DDG CT and 4D CT were identical 68.2±18.9% of the time. Inspection of the EE and EI phases of DDG CT and 50% and 0% of 4D-CT demonstrated both data sets of DDG CT and 4D CT were almost identical. A new DDG PET/CT and 4D-CT in a single imaging session without any hardware gating has been developed for TRA and RTP of NSCLC. The utility is available on the network and it enables all PET/CT scanners on the network for TRA and RTP. The new DDG CT provides the benefits of 4D-CT without any requirement of external hardware gating and make possible DDG PET/CT free of tumor motion and misregistration artifacts.

Effects of Respiratory and Cardiac Motion on Dose to the Left Anterior Descending Artery in Patients Undergoing Radiation Therapy for Locally Advanced Lung Cancer

Radiation dose to the left anterior descending artery (LAD) appears to be an independent predictor of major cardiac events and all-cause mortality following radiation therapy (RT) for lung cancer. In this study, we characterize the dosimetric effects of respiratory (RM) and cardiac (CM) motion on LAD. Ten patients with stage IIIA-IVA lung cancer received cine MRIs (25 phases) at expiration which were used to evaluate the CM, and 4D CT scans for the evaluation of RM. Following registration of the expiration images of 4D CTs with MRIs, RT dose was transferred from planning CT datasets to all phases of 4D CTs and cine MRIs. LAD was manually contoured on all scans. The contours from each 4D phase represent LADs over multiple cardiac cycles, thus they are referred to as cLAD from here on. Displacements and dose variations of cLAD between exhale/inhale on 4D CTs and of LAD between systolic and diastolic phases on cine MRIs were analyzed, and paired t-tests were performed to assess the significance of the differences observed. The following metrics are reported averaged over all patients. Clinical treatment planning CT metrics and doses: Mean dose, max dose, V5 Gy and V15 Gy were 15.0 (±11.3) Gy, 31.1 (±22.1) Gy, 53 (±33)%, 35 (±30)%. The cLAD metrics and dose variations due to respiratory motion (between exhale and inhale): RM amplitude was 0.3±0.2cm (RL 0.3 ± 0.1 cm, AP 0.2 ± 0.2 cm, SI 0.3 ± 0.2 cm). The variations in mean dose, max dose, V5 and V15 were 4.0 (±4.0) Gy, 1.6 (±1.5) Gy, 4.4 (±3.4)%, 4.0 (±3.4)%. Mean, max, V5 Gy and V15 Gy increased or remained unchanged with expiration in 8, 9, 5 and 5 patients, respectively. LAD metrics and dose variations due to cardiac motion (between systole and diastole): CM amplitude was 0.2 ± 0.1 cm (RL 0.2 ± 0.1 cm, AP 0.2 ± 0.1 cm, SI 0.3 ± 0.1 cm). The variations in mean dose, max dose, V5 and V15 were 1.7 (±1.4) Gy, 1.2 (±0.9) Gy, 5.2 (± 6.7)%, 4.6 (± 4.0)%. Mean, max, V5 Gy and V15 Gy increased or remained unchanged with diastole in 7, 7, 8 and 8 patients respectively. Statistical significance: The differences in displacement and dose between respiration and cardiac motion were not statistically significant. Respiratory and cardiac-induced physiological variations of the LAD position have dosimetric consequences comparable in magnitude. Expiration and diastole lead to increased LAD doses. This underscores the importance of considering both the respiratory and the cardiac motion when motion management techniques are considered. 4D CTs inherently include the cardiac motion. However, if breath-hold is used for respiratory motion mitigation, CM might not be captured appropriately due to short tube rotation times. In this case, understanding CM characteristics is important for more accurate assessment of LAD dose.

Pencil Beam Scanning Proton Stereotactic Body Radiation Therapy (SBRT): A Robust Single Institution Experience

To describe the feasibility of treating a complex and diverse group of patients using pencil beam scanning (PBS) proton stereotactic body radiation therapy (SBRT: 5 or fewer fractions, with a fraction size of at least 5 Gy). Our center treats on average 105-120 PBS proton treatments daily, of which 9.5% of treatment courses are proton SBRT. Statistics of disease sites, treatment planning parameters (target volume, prescriptions, number of fields, SFO vs. MFO), and treatment efficiencies (scheduled time slots, actual treatment time) are presented for 305 consecutive SBRT patients receiving 1507 fractions in the past three years. Thermoplastic masks or Vacuum-lock bags are used to immobilize SBRT patients and index the patients' treatment position. Imaging guidance of orthogonal kV images and volumetric cone-beam CT is routinely used for patient setup. SBRT patients are grouped based on the target locations: pelvis (31%), liver (17%), thoracic (13%), spine (8%), abdominal (8%), brain (7%), non-spine bone (7%), ocular (6%), and head and neck (2%). Only 112 patients (37%) were receiving their 1st RT course, whereas 113 (37%) had one prior in-field RT course, and 80 (26%) had multiple prior in-field RT courses. The median [IQR] target volume was 65.4 [29.3, 168] cc (range: 0.3-2475 cc). 72% of cases were planned with SFO and 28% with MFO. On average, 3.76 fields (range: 2 to 12) were planned for each treatment. 44% of the treatments were planned with three or fewer fields, and 10% received more than five fields, most of which involved repainting for moving targets. Over 97% of treatments were delivered in 5 fractions, with ∼3% delivered in 3 fractions. The median [IQR] prescription per treatment was 8 [7, 10] Gy (range: 5-18 Gy per treatment). 85% (84%) of the SBRT treatments were scheduled (delivered) in a 45-minute or shorter slot, and 6% (7%) of treatments were scheduled (delivered) in over a one-hour slot, most commonly for multiple isocenter treatments. 93% of treatments were delivered within 15 minutes of the planned treatment time or shorter. Deep-inspiration breath-hold (DIBH) was applied to 45% of liver SBRT cases, with the remaining 55% planned on 4D CT with (14%) or without (86%) abdominal compression. DIBH was applied in 13% of lung SBRT cases. The application of other motion mitigation approaches, such as volumetric repainting, was determined by the target motion amplitude and whether the patient could tolerate DIBH. In the most diverse and largest proton SBRT experience delivered in the world over the past 3 years, over 300 patients were treated, demonstrating the feasibility and efficiency of delivering proton SBRT in a very busy center. The planning and treatment parameter statistics reported serve as a helpful reference for the proton community.

Stereotactic Body Radiotherapy (SBRT) for Adrenal Metastases: Practice Patterns at Community-Based Radiotherapy Centers

To analyze SBRT of adrenal metastases at free-standing centers within a large network in the USA, in order to guide institutional recommendations. We interrogated records of patients treated with SBRT to adrenal metastases from January 2019 to June 2022 from a database of 13,363 patients who were treated with SBRT at 21 community-based centers clustered into five regions within a network. We reported patient characteristics, frequency, survival rate, and biologically effective dose (BED10) prescribed, respiratory motion capture according to region and treatment year. Survival was calculated by Kaplan-Meier estimates. A total of 271 patients were treated to metastatic adrenal lesions (2.0% of all SBRT patients). Median age was 69.8 years (range 32-96). Frequency of treatment increased by an average of 4.5% per year over the period. Table 1 gives the frequency of primary tumor sites, histological types, and dose fractionations. It also shows the range of BED10 used. 91% received five fractions, and 6% received 3 fractions. Median BED10 was 72 Gy (mean 68.0 Gy SD = 18.7). The most common regimen was 8 Gy x 5 (n = 75, 28%), but ranged from 5 Gy x 5 (n = 20) to 10 Gy x 5 (n = 34). BED10 varied according to geographic region ranging from 61.2 Gy to 73.0 Gy (p = 0.01). Median BED was 72 or above in 2 of 5 regions and less than 72 in 3 regions. Respiratory motion capture simulation was done in 65.1% of cases and frequency varied across the 5 locations as shown in Table1 from 93.3% in region 1 to 41.7% in region 5 (p<.0001). 4D CT simulation was used in 46.2% of cases and use was relatively stable over time: 52.8% in July to December 2020 and 40.9% from January to June 2022 with no trend over time: p = .7635 At median follow-up 6.6 months (range 0.3-48.5), 203 (74.9%) of patients were alive with a median overall survival of 24.3 months. 1-year and 2-year survival was 72.7% and 51.5% respectively. Use of respiratory motion simulation was not significantly associated with survival p = 0.47. Despite variation in BED10 and respiratory motion management, 2-year overall survival was over 50% in patients treated with SBRT for adrenal metastases in a large community network. Further study will address refinement of recommendations regarding dose and other treatment characteristics and expansion of clinical research in this setting.

Assessing Diagnostic Accuracy of Four-dimensional CT for Instable Scapholunate Dissociation: The Prospective ACTION Trial.

Background Timely treatment of scapholunate instability depends on early identification, but current imaging methods are either intricate or fail to demonstrate the dynamic stages. Purpose To calculate the diagnostic accuracy of four-dimensional (4D) CT for diagnosing instable scapholunate ligament (SLL) tears. Materials and Methods This prospective study enrolled consecutive participants with clinically suspected SLL tears who underwent 4D CT from July 2020 to May 2022. A historical study sample diagnosed at cineradiography served as a comparison, and wrist arthroscopy was the reference standard. Scapholunate joints greater than 3 mm were interpreted as instable at index 4D CT and cineradiography. Diagnostic accuracy was expressed as sensitivity and specificity. Areas under the receiver operating characteristic curve and cutoff values for both index tests were calculated. Intraclass correlation coefficients (ICCs) were computed to compare interrater reliability. Effective radiation doses at 4D CT were measured with thermoluminescent dosimeters. Results The study included 40 participants (mean age, 43 years ± 14 [SD]; 24 male) evaluated at 4D CT and 78 patients (mean age, 45 years ± 11; 50 male) historically evaluated at cineradiography. Four-dimensional CT helped detect instable tears in 26 of 35 participants (sensitivity, 74.3% [95% CI: 56.7, 87.5]. Cineradiography revealed instable tears in 52 of 63 patients (sensitivity, 82.5% [95% CI: 70.9, 91]). Four of five participants with stable scapholunate joints were identified at 4D CT (specificity, 80.0% [95% CI: 28.4, 99.5]), and 12 of 15 patients with stable SLLs were identified at cineradiography (specificity, 80.0% [95% CI: 51.9, 95.7]). Interrater agreement of radiologic measurements on 4D CT scans was good to excellent (ICC range, 0.89-0.96). The effective radiation dose ranged from 67 to 72 mSv at the wrist and was less than 1 mSv at the head. Conclusion Four-dimensional CT results are highly reproducible. Instable scapholunate joints greater than 3 mm were detected with a sensitivity of 74.3% and a specificity of 80% in an exploratory trial. Further evidence from larger randomized trials is warranted. German Register for Clinical Trials no. DRKS00021110 (Universal Trial Number U1111-1249-7884) Published under a CC BY 4.0 license. Supplemental material is available for this article. See also the editorial by Demehri and Ibad in this issue.

Assessment of Scapholunate Instability on 4D CT Scans in Patients with Inconclusive Conventional Images.

Background Initial imaging work-up using radiography and CT arthrography sometimes can be insufficient to identify a scapholunate (SL) instability (SLI) in patients suspected of having SL ligament tears. Purpose To determine the diagnostic performance of four-dimensional (4D) CT in the identification of SLI and apply the findings to patients suspected of having SLI and with inconclusive findings on radiographs and CT arthrograms. Materials and Methods This prospective single-center study enrolled participants suspected of having SLI (recent trauma, dorsal pain, positive Watson test results, decreased grip strength) between March 2015 and March 2020. Participants with wrist fractures, substantial joint stiffness, or history of wrist surgery were excluded. Each participant underwent radiography, CT arthrography, and 4D CT on the same day. Participants were divided into three groups: those with no SLI, those with SLI, and those with inconclusive results. SL gap and radioscaphoid and lunocapitate angle were measured using semiautomatic quantitative analysis of 4D CT images by two independent readers. Receiver operating characteristic curves were used to evaluate the diagnostic performance of 4D CT. Thresholds were determined with the Youden index and were applied to the inconclusive group. Results Of the 150 included participants (mean age, 41 years ± 14 [SD]; 102 male, 48 female), there were 63 with no SLI, 48 with SLI, and 39 with inconclusive results. The maximum value and range of SL gap measurements on 4D CT scans showed high sensitivity (83% [40 of 48] and 90% [43 of 48], respectively) and high specificity (95% [59 of 62] and 81% [50 of 62], respectively) in the identification of SLI. At least one of these parameters was abnormal on 4D CT scans in 17 of 39 (44%) participants in the inconclusive group, and 10 of 17 (59%) participants had confirmed SLI. In the 22 participants in the inconclusive group with no indication of SLI at 4D CT, follow-up showed no evidence of SLI in 10 (45%) and enabled confirmation of SLI via arthroscopy in three (14%). Conclusion Scapholunate gap measurements on kinematic 4D CT scans enabled correct identification of SLI in 59% of participants with inconclusive results on conventional images. ClinicalTrials.gov registration no. NCT02401568 © RSNA, 2023 Supplemental material is available for this article. See also the editorial by Demehri and Ibad in this issue.

The hemodynamics of adrenal veins with four-dimensional computed tomography using quantitative time-density curve: a study based on aldosteronism patients

Present study quantitatively analyzed adrenal venous flow using four-dimensional computed tomography (4D CT). We reviewed 4D CT images of 55 patients [mean age, 52 years ± 11 (standard deviation); 23 females] who underwent adrenal venous sampling between August 2017 and February 2021. Time–density curves were referred for the adrenal venous enhancement. The clinical factors affecting hemodynamics were assessed using uni- and multivariate linear regression analyses. The right and left adrenal veins (RAV and LAV, respectively) were visualized in all cases. Mean peak enhancement values in RAV and LAV were 247 ± 67 and 292 ± 70 Hounsfield units (P < 0.01), and were reached at 44.43 ± 6.86 and 45.39 ± 7.53 s (P < 0.01), respectively. The body mass index (BMI), plasma renin activity and potassium were significant factors influencing the peak enhancement of RAV blood flow [standardized regression coefficients, − 0.327 (P = 0.017), − 0.346 (P = 0.013), 0.426 (P = 0.016), respectively]. A linear relationship between sex and the time-to-peak was observed for RAV [standardized regression coefficient, 0.348 (P = 0.046)]. RAV had a lower contrast effect than LAV and reached its peak faster. BMI, plasma renin activity, and potassium were associated with flow density in RAV. Sex independently influenced the time-to-peak.

Quantitative analyzes of the variability in airways via four-dimensional dynamic ventilation CT in patients with chronic obstructive pulmonary disease: correlation with spirometry data and severity of airflow limitation.

In chronic obstructive pulmonary disease (COPD) patients, the diagnosis and assessment of disease severity are mainly based on spirometry, which may lead to misjudgments due to poor patient compliance. Thoracic four-dimensional dynamic ventilation computed tomography (4D-CT) provides more airway data approximating true physiological function than conventional CT. We aimed to determine dynamic changes in airways to elucidate the pathological mechanism underlying COPD and predict the severity of airflow limitation in patients. Forty-two COPD patients underwent 4D-CT and spirometry. The minimum lumen diameter changed with the breathing cycle in 4th-generation airways and was continuously measured in the apical (RB1), lateral (RB4) and posterior basal segments (RB10) of the right lung. The minimum lumen diameter in the peak inspiration and peak expiration as well as the peak expiratory/peak inspiratory ratio (E/I ratio), and dynamic coefficient of variance (CV) were calculated. Correlations of FEV1% with the CV of minimum lumen diameter in RB1 (ρ=-0.473, P=0.002) and in RB10 (ρ=-0.480, P=0.005) were observed, suggesting that the dynamic variability in 4th-generation airways was associated with airflow limitation in COPD patients. The CV of the minimum lumen diameter in RB1 significantly differed between the GOLD I + II and GOLD III + IV groups {8.59 [interquartile range (IQR), 6.63-14.86] vs. 14.64 (10.65-25.88), respectively; P=0.016}, suggesting that the dynamic CV in RB1 increased significantly in the GOLD III + IV group, which had worse pulmonary ventilation function. Based on the receiver operating characteristic (ROC) curve analysis, CV-RB1 predicted FEV1% <50% with an optimal cut-off of 9.43% [sensitivity 85.7%, specificity 57.1%, area under the curve (AUC) 0.717]. 4D-CT might be an available method to help diagnose and evaluate the severity of COPD.

Relative thoracic changes from supine to upright patient position: A proton collaborative group study.

This study presents position changes of a few radiotherapy-relevant thoracic organs between upright and typical supine patient orientations. Using tools in a commercial treatment planning system (TPS), key anatomical distances were measured for four-dimensional CT data sets and analyzed for the two patient orientations. The uncertainty was calculated as the 95% confidence interval (CI) on the relative difference for each of the four analyzed changes for upright relative to supine, as follows: the distance of the bottom of the heart to the top of the sternum, it changed +2.6% or +4mm (95% CI [+0.30%,+4.9%]); the distance of the center of the C3 vertebra to the backrest, it changed +29% (95% CI [+22%,+36%]); the contoured left and right lungs increased their volumes respectively: +17% (95% CI [+12%,+21%]) for the left, and +9.9% (95% CI [+4.1%,+16%]); and lastly, the distance from the top of the sternum to the top of the liver, but its uncertainty far exceeded the average change by a factor of two. This last result is therefore inconclusive, the others show that with 95% confidence that a change in internal positions is observed for lung volumes and heart position that could be important for upright treatments.

Impact of leaflet thrombosis on valve haemodynamic status after transcatheter aortic valve replacement

ObjectivesThe effect of subclinical leaflet thrombosis, characterised by hypoattenuated leaflet thickening (HALT), on the valve haemodynamic function and durability of the bioprosthetic valve, is not yet determined. We determined the...

Diaphragm displacement estimation based on subspace mapping from markerless abdominal surface measurement

Respiratory induced organ and tumor motion has great influence in radiation therapy. In order to estimate the inner structures’ movement by external observation, a novel two-step subspace mapping (TSSM) algorithm is proposed to estimate the diaphragm displacement from markerless abdominal surface measurement. We first incorporate 3D image segmentation to measure the displacement of the inner diaphragm and the external abdominal surface on 4D CT images. TSSM constructs eigenspaces by PCA and projects the two organs’ displacement data into their corresponding subspaces. Then, TSSM makes a mapping between the subspaces by a Ridge regression optimization to effectively characterize their correlation. Based on the trained correlation model, the diaphragm displacement can be estimated by the abdominal surface without markers. TSSM is further extended to kernel TSSM (kTSSM) to investigate the non-linear correlation. Experiments show the proposed method can accurately estimate the displacement of the internal diaphragm by the external abdominal surface.

Using Texture Analysis of Neck Computed Tomography Images to Differentiate Primary Hyperparathyroidism From Normal Controls.

To investigate the utility of texture analysis in detecting osseous changes associated with hyperparathyroidism on neck CT examinations compared with control patients and to explore the best regions in the head and neck to evaluate changes in the trabecular architecture secondary to hyperparathyroidism. Patients with hyperparathyroidism who underwent a 4D CT of the neck with contrast were included in this study. Age-matched control patients with no history of hyperparathyroidism who underwent a contrast-enhanced neck CT were also included. Mandibular condyles, bilateral mandibular bodies, the body of the C4 vertebra, the manubrium of the sternum, and bilateral clavicular heads were selected for analysis, and oval-shaped regions of interest were manually placed. These segmented areas were imported into an in-house developed texture analysis program, and 41 texture analysis features were extracted. A mixed linear regression model was used to compare differences in the texture analysis features contoured at each of the osseous structures between patients with hyperparathyroidism and age-matched control patients. A total of 30 patients with hyperparathyroidism and 30 age-matched control patients were included in this study. Statistically significant differences in texture features between patients with hyperparathyroidism and control patients in all 8 investigated osseous regions. The sternum showed the greatest number of texture features with statistically significant differences between these groups. Some CT texture features demonstrated statistically significant differences between patients with hyperparathyroidism and control patients. The results suggest that texture features may discriminate changes in the osseous architecture of the head and neck in patients with hyperparathyroidism.

Musculoskeletal CT Imaging: State-of-the-Art Advancements and Future Directions.

CT is one of the most widely used modalities for musculoskeletal imaging. Recent advancements in the field include the introduction of four-dimensional CT, which captures a CT image during motion; cone-beam CT, which uses flat-panel detectors to capture the lower extremities in weight-bearing mode; and dual-energy CT, which operates at two different x-ray potentials to improve the contrast resolution to facilitate the assessment of tissue material compositions such as tophaceous gout deposits and bone marrow edema. Most recently, photon-counting CT (PCCT) has been introduced. PCCT is a technique that uses photon-counting detectors to produce an image with higher spatial and contrast resolution than conventional multidetector CT systems. In addition, postprocessing techniques such as three-dimensional printing and cinematic rendering have used CT data to improve the generation of both physical and digital anatomic models. Last, advancements in the application of artificial intelligence to CT imaging have enabled the automatic evaluation of musculoskeletal pathologies. In this review, the authors discuss the current state of the above CT technologies, their respective advantages and disadvantages, and their projected future directions for various musculoskeletal applications.

Assessing four-dimensional CT stress maps derived from patient-specific biomechanical models of the lung with pulmonary function test data in lung cancer patients.

This study aims to retrospectively compare the stress map of the lung with pulmonary function test (PFT) results in lung cancer patients and to evaluate the potential of the stress map as an imaging biomarker for chronic obstructive pulmonary disease (COPD). 25 lung cancer patients with pre-treatment four-dimensional CT (4DCT) and PFT data were retrospectively analysed. PFT metrics were used to diagnose obstructive lung disease. For each patient, forced expiratory volume in 1 s (FEV1 % predicted) and the ratio of FEV1 and forced vital capacity (FEV1/FVC) were recorded. 4DCT and biomechanical model-deformable image registration (BM-DIR) were used to obtain the lung stress map. The relationship between the mean of the total lung stress and PFT data was evaluated, and the COPD classification grade was also evaluated. The mean values of the total lung stress and FEV1 % predicted showed a significant strong correlation [R = 0.833, (p < 0.001)]. The mean values and FEV1/FVC showed a significant strong correlation [R = 0.805, (p < 0.001)]. For the total lung stress, the area under the curve and the optimal cut-off value were 0.94 and 510.8 Pa for the classification of normal or abnormal lung function, respectively. This study has demonstrated the potential of lung stress maps based on BM-DIR to accurately assess lung function by comparing them with PFT data. The derivation of stress map directly from 4DCT is novel method. The BM-DIR-based lung stress map can provide an accurate assessment of lung function.

Poster 245: Clinical Measurement of the Standard Q-Angle Correlates Poorly with Tibial Tuberosity to Trochlear Groove Distance in Awake Patients and Anesthetized Patients with Patella Alta and Trochlear Dysplasia

Objectives: The quadriceps angle (Q-angle) measures the force vector of pull of the extensor mechanism of the knee. A larger Q-angle is thought to be a predisposing factor for patellar dislocation, but previous literature has reported poor reliability and validity of clinically measured Q-Angle. In response to poor reliability, a new “Standard Q-Angle” (SQA) was developed by Merchant et al. (Merchant 2020) in an attempt to create a standardized and repeatable method of clinically measuring the Q-Angle. The SQA may be a practical, inexpensive, and valuable part of physical examinations to help clinicians decide if concomitant medializing osteotomy is indicated in patellar stabilization procedures. However, SQA has not yet been validated in patients with anatomic risk factors for recurrent patellar instability such as patella alta and trochlear dysplasia. Furthermore, while SQA has previously been demonstrated to have strong interrater reliability, it has never been shown to correlate with standardized measurements for a lateralized tibial tuberosity, such as the Tibial Tuberosity – Trochlear Grove (TT-TG) distance. Therefore, the purpose of our study was to determine the correlation between SQA and TT-TG distance in patients with recurrent patellar instability. We hypothesized that there would be a positive correlation between SQA and TT-TG distance. 1. Merchant AC, Fraiser R, Dragoo J, Fredericson M. A reliable Q angle measurement using a standardized protocol. Knee. 2020;27(3):934-939. Methods: Patients at a single institution treated by a single surgeon with recurrent patellar instability who had previously obtained a dynamic 4D CT scan were included in this study. Patients who had previous patellar stabilization procedures were excluded. The Standard Q-angle was measured as previously described by Merchant et al. (Merchant 2020). The patient was placed in the supine position with the knee extended. A long-arm goniometer was centered over the patella with the distal arm over the tibial tuberosity and the proximal arm extended up to the anterior superior iliac spine (ASIS). The examiner then centered the patella within the trochlear groove and the SQA was measured. A second examiner stood at foot of the patient’s bed to confirm positioning. Measurements were taken in the office, as well as in the operating room after the induction of general anesthesia. All measurements were performed by the senior author (***). Utilizing 4D CT scans, the TT-TG, Caton-Deschamps index (CDI), and lateral trochlear inclination (LTI) were measured as previously described. Patients whose CDIs were between 0.8 and 1.2 were considered to have normal patellar height. Patients whose LTIs were &gt;11° were considered to have normal LTI, which has been shown to have a sensitivity of 93% and a specificity 87% for detecting trochlear dysplasia. Mean and standard deviation values were calculated for patient demographic information, and correlation coefficients were calculated to compare SQA with TT-TG distance in both awake and anesthetized patients. The statistical software Stata was utilized for all analyses (StataCorp. 2021. Stata Statistical Software: Release 17. College Station, TX). Results: Fifty-seven patient knees were included in the study. The mean age was 22 years-old (±6 years). For awake patients, the correlation coefficient (R2) between SQA and TT-TG was -0.006 (Figure 1), and in anesthetized patients R2 = 0.093 (Figure 2). In the “normal patellar height” group, the R2 value was higher in the anesthetized group (R2 = 0.334) than the awake group (R2 = 0.239). In the normal lateral trochlear inclination group, there was also a greater R2 value in the anesthetized group (R2 = 0.403) than the awake group (R2 =0.093). The correlation between SQA and TT-TG was the strongest in anesthetized patients with both a CDI &lt; 1.2 and LTI &gt;11° (R2 = 0.635). Conclusions: There was a strong positive association between SQA and TT-TG in anesthetized patients with normal patellar height and a normal lateral trochlear inclination. However, in awake patients and patients with anatomic risk factors for recurrent patellar instability there was only a weak association between SQA and TT-TG. The SQA may be able to provide useful information, but only in selected cases. Therefore, it remains important to have objective radiographic measurements to characterize the position of the tibial tuberosity when planning patellar stabilization surgery.