Evaluation of the Prognostic Value of Pretherapeutic Magnetic Resonance Imaging in Predicting Soft Tissue Sarcoma Radiation Response: A Retrospective Study from a Large Institutional Sarcoma Imaging Database.

Background: RT-induced hyalinization/fibrosis was recently evidenced as a significant independent predictor for complete response to neoadjuvant radiotherapy (RT) and survival in patients with soft tissue sarcoma (STS). Purpose: Non-invasive predictive markers of histologic response after neoadjuvant RT of STS are expected. Materials and Methods: From May 2010 to April 2017, patients with a diagnosis of STS who underwent neoadjuvant RT for limb STS were retrieved from a single center prospective clinical imaging database. Tumor Apparent Diffusion Coefficients (ADC) and areas under the time-intensity perfusion curve (AUC) were compared with the histologic necrosis ratio, fibrosis, and cellularity in post-surgical specimens. Results: We retrieved 29 patients. The median ADC value was 134.3 × 10-3 mm2/s. ADC values positively correlated with the post-treatment tumor necrosis ratio (p = 0.013). Median ADC values were lower in patients with less than 50% necrosis and higher in those with more than 50% (120.3 × 10-3 mm2/s and 202.0 × 10-3 mm2/s, respectively (p = 0.020). ADC values higher than 161 × 10-3 mm2/s presented a 95% sensitivity and a 55% specificity for the identification of tumors with more than 50% tumor necrosis ratio. Tumor-to-muscle AUC ratios were associated with histologic fibrosis (p = 0.036). Conclusions: ADC and perfusion AUC correlated, respectively, with radiation-induced tumor necrosis and fibrosis.

Olfactory cleft stenosis and obstruction on paranasal sinus CT scan in pre-septo-rhinoplasty patients: normal variants or pathologic findings?

OBJECTIVE(S): To determine the frequency of olfactory cleft (OC) stenosis and obstruction on paranasal sinus CT scans in pre-septorhinoplasty of patients who had septal deviation, septopyramidal deformation or nasal obstruction without other sinonasal conditions. METHODS: This retrospective study included patients referred to our institution between December 2013 and December 2021 for septorhinoplasty due to nasal obstruction without other sinonasal or neurological conditions. All patients underwent preoperative paranasal sinus CT scan and olfactory testing. OC stenosis was quoted as none, partial, or total (less than 1/3 contact between nasal septum and ethmoid turbinates, 1/3-2/3, more than 2/3, respectively), as well as OC obstruction as none, partial, or complete (obstruction of less than 1/3 of OC, 1/3-2/3, more than 2/3, respectively). Radiologic evaluation was validated by near perfect interobserver agreement. RESULTS: A total of 75 patients (32 women, 43 men) with a mean age of 44.2 ± 15.64 (23-74) years were included, of which 36 were normosmic and 39 hyposmic. OC stenosis was partial in 58.7% (n = 44) of the patients, absent in 28% (n = 21), and total in 13.3% (n = 10), without difference between normosmic and hyposmic patients (p = .66). OC obstruction was absent in 52% (n = 39) and partial in 46.7% (n = 35), without difference between normosmic and hyposmic patients (p = .51). Only one normosmic patient had complete OC obstruction. CONCLUSION: OC partial stenosis and partial obstruction were frequent findings in pre-septorhinoplasty patients without respiratory mucosa disease and did not influence their olfactory status. Total stenosis and complete obstruction were rarer and require further investigation. CLINICAL RELEVANCE STATEMENT: Isolated partial olfactory cleft stenosis and obstruction should be considered normal variants, whereas the impact of complete olfactory cleft stenosis and obstruction on patient's olfactory status remains to be determined. KEY POINTS: • The incidence of olfactory cleft stenosis and obstruction in asymptomatic patients remains unknown, even though it is encountered in clinical practice. • Partial and total olfactory cleft stenosis occurred in 58.7% and 13.3% of the patients; partial obstruction occurred in half of the cases, but complete obstruction was extremely rare. • There are frequent findings of partial olfactory cleft obstruction and stenosis, but complete obstruction and total stenosis should be further investigated.

Reconstruction of the ulnar artery in Guyon's canal with an arterial graft: Anatomical study.

Ulnar artery thrombosis in Guyon's canal can lead to vascular insufficiency in the fingers. The recommended treatment is resection and reconstruction of the pathological area. A bypass may be necessary, which may be venous or arterial. Arterial bypasses have better long-term patency; however, they are a source of donor-site complications. We carried out an anatomical study on 11 upper limbs and 7 lower limbs from cadavers to identify a technically accessible arterial graft, of a diameter suitable for bypassing the ulnar artery in Guyon's canal and with acceptable scar sequelae (few predicted postoperative complications, discreet size and/or location of scar). Three grafts were considered: anterior interosseous artery, radial recurrent artery and descending genicular artery. The various grafts were dissected and harvested from cadaver specimens, then their lengths and diameters were measured. The diameter of the candidate grafts was compared to the diameter of the distal ulnar artery. The diameter of the descending genicular artery matched the ulnar artery better than the radial recurrent artery or the anterior interosseous artery (103% vs 44% and 67%, respectively). Mean graft length was 6.6 cm. The anatomical configuration of the descending genicular artery allowed Y-shaped bypasses to be performed. Harvesting this artery appears to cause little damage and allows bypasses up to 6 cm to be performed. Despite its smaller diameter making it necessary to perform a microvascular size adjustment, the anterior interosseous artery is a candidate graft because it is long enough (119 mm) and located near the surgical site. LEVEL OF EVIDENCE: V.

Prevalence of abnormalities seen on orthopantomograms performed for forensic age estimation in unaccompanied minor asylum seekers.

OBJECTIVES: Evaluate the prevalence of radiological anomalies on orthopantomograms (OPT) performed as part of forensic age estimation in unaccompanied minors. METHODS: This is a retrospective study conducted on 208 OPT examinations requested by a magistrate. These OPTs were interpreted independently by two readers to establish the number of missing teeth (MT), presence of dental fillings (DF), and dental anomalies (DA). The presence of radiolucent (RL), radiopaque, and mixed lesions was also assessed. RESULTS: Most radiologic anomalies were RL, detected on 41% and 39% of the subjects evaluated for R1 and R2, respectively, with a mean of 1.3 ± 2.4 (1-16) and 1.1 ± 2 (1-13) RL lesions per subject. Among the RL identified, the majority were dental (70% for R1 and 65% for R2), all of which had a suspected infectious origin. Among readers, 43% and 41% of the subjects evaluated presented MT, 21% and 15% presented DF, and 22% and 20% presented DA for R1 and R2, respectively. The inter- and intra-observer reproducibility for OPT classification was considered excellent (Kappa = 0.84, 95% CI 0.78-0.90, and Kappa = 0, 95, 95% CI 0.86-0.99). DISCUSSION: There was a non-negligible prevalence of radiological anomalies in OPT studies performed for forensic age estimation. Most of these lesions were suspected to be infectious in origin, potentially requiring medical care. This constitutes an ethical dilemma inherent in the judicial expertise injunction requiring a limited specific response. CLINICAL RELEVANCE STATEMENT: This study highlights a non-negligible prevalence of supposedly infectious radiological abnormalities. The restricted possibility for the legal expert to declare these abnormalities raises ethical and medical questions. KEY POINTS: • Orthopantomograms can be performed as part of forensic age estimation. • Results indicate the majority of radiological anomalies detected on OPTs were of suspected infectious origin. • These findings give rise to ethical and medical questions about the way in which these forensic examinations are carried out.

Initial Evaluation of Focal Bone Lesions: How Do We Do It?

Focal bone lesions are frequent, and management greatly depends on the characteristics of their images. After briefly discussing the required work-up, we analyze the most relevant imaging signs for assessing potential aggressiveness. We also describe the imaging aspects of the various types of lesion matrices and their clinical implications.

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 effect of intercarpal arthrodeses on wrist kinematics during radial and ulnar deviation: a cadaveric study using four-dimensional CT.

In this cadaveric study, we report quantitative dynamic four-dimensional CT evaluation of the effect on wrist kinematics of three intercarpal arthrodeses during radial and ulnar deviation. In five wrists, we successively performed scaphocapitate, four-corner and two-corner fusions. Four-dimensional CT examinations were performed prior to dissection and after each arthrodesis. The lunocapitate gap, posterior lunocapitate angle, radiolunate radial gap, radiolunate ulnar gap and radiolunate angle were assessed. After scaphocapitate arthrodesis, in radial deviation, we noted midcarpal diastasis and dorsal displacement of the capitate. In ulnar deviation, there was correction of that incongruence. After four-corner and two-corner fusions, in radial deviation, we noted radial radiolunate impingement and ulnar radiolunate incongruence. In ulnar deviation, after two-corner fusion, ulnar radiolunate impingement and radial radiolunate incongruence were present contrary to four-corner fusion. Our findings confirm that the constant radiocarpal and midcarpal congruence during radioulnar deviation in normal wrists is no longer possible with intercarpal kinematic modifications after these arthrodeses.

Correlation Between Dynamic 4-Dimensional Computed Tomography Data and Arthroscopic Testing of Scapholunate Instability: A Preliminary Study.

PURPOSE: The aim of this study was to test the validity and reliability of the assessments of scapholunate (SL) instability status on 4-dimensional (4D) computed tomography (CT) using wrist arthroscopy as a reference standard. METHODS: Thirty-three patients (16 men, 17 women; mean age, 48 ± 13 years) with suspected SL instability were evaluated prospectively with 4D-CT and wrist arthroscopy. Based on the arthroscopic testing of SL joint, 2 groups were defined: group 1 (n = 8) consisted of patients who had no, or slight, SL malalignment in the midcarpal space and group 2 (n = 25) consisted of patients who had moderate or severe SL malalignment. Two independent readers, who did not know the arthroscopic findings, used 4D-CT to evaluate the SL gap, lunocapitate angle (LCA), and radioscaphoid angle (mean and range values) during radioulnar deviation. RESULTS: The interobserver reliability was deemed good or excellent for most of the 4D-CT variables, except for the LCA range (moderate) and SL gap range (poor). For both readers, the SL gap mean, maximum, and minimum values were significantly higher (+67%, +78%, and +39%, respectively) and the LCA mean was significantly lower (-17%) in group 2 than in group 1. The radioscaphoid angle range values were lower (-34%) and the radioscaphoid angle mean values slightly higher (+4%) in group 2, but there was no significant difference between the 2 groups. The SL gap range values were also higher (+86% for R1 and +40% for R2) and the LCA range values also lower (-50% for R1 and -31% for R2) in group 2. CONCLUSIONS: Quantitative 4D-CT data corresponded well with the arthroscopic dynamic analysis of the SL joint in patients with suspected chronic SL instability. TYPE OF STUDY/LEVEL OF EVIDENCE: Diagnostic II.

Association between opportunistic vertebral bone density measurements and new vertebral fractures after percutaneous vertebral cementoplasty: a case-control study.

OBJECTIVES: To study the relationship between opportunistic CT bone density measurements and the occurrence of new vertebral fractures after percutaneous vertebral cementoplasty (PVC) of osteoporotic vertebral compression fractures (OVCF). METHODS: A prospective analysis of retrospective data of 275 patients with OVCF treated by PVC between 2014 and 2019 with a clinico-radiological follow-up one year after treatment was conducted. Opportunistic bone density measurements were obtained at the trabecular bone of the L1 or an adjacent vertebra in Hounsfield units performed on the preoperative CT study. These density measurements values ​​were then compared between patients with and without new OCVF and in various population subgroups. RESULTS: There were 275 patients included, with 53 (19%) presenting a new OCVF and 24 (9%) developing a fracture cascade. The median opportunistic density measurements ​​in patients with recurrent OCVF were lower than those without (median 52[40.5]) HU and 77[49] HU)(p < 0.00001). Among the patients with new OVCF the median opportunistic density measurements in patients with fracture cascades were also lower than those without (44 HU and 62 HU, respectively) (p < 0.0096). Patients with density measurements under 61 HU were 3.6 times more likely to present recurrent fractures and those with density under 54 HU were 9.8 times more likely to develop a fracture cascade. The 36 HU threshold yielded a high specificity (90-91%) for the prediction of recurrent fractures and fracture cascade but with low sensitivity (respectively 26% and 37%). CONCLUSION: Low opportunistic vertebral density measurements are associated with a higher risk of OVCF and fracture cascades after PVC. KEY POINTS: • Low opportunistic density measurements are associated with a higher risk of OVCF and fracture cascades after PVC. • Measuring bone density before performing a PVC could help predict the risk of new vertebral fracture after treatment • Patient management could be adapted according to bone density.

Initial Characterization of Focal Bone Lesions with Conventional Radiographs or Computed Tomography: Diagnostic Performance and Interobserver Agreement Assessment.

Objectives: To ascertain the role of CT and conventional radiographs for the initial characterization of focal bone lesions.Methods: Images from 184 patients with confirmed bone tumors included in an ethics committee-approved study were retrospectively evaluated. The reference for benign-malignant distribution was based on histological analysis and long-term follow-up. Radiographs and CT features were analyzed by 2 independent musculoskeletal radiologists blinded to the final diagnosis. Lesion margins, periosteal reaction, cortical lysis, endosteal scalloping, presence of pathologic fracture, and lesion mineralization were evaluated. Results: The benign-malignant distribution in the study population was 68.5-31.5% (126 benign and 58 malignant). In the lesions that could be seen in both radiographs and CT, the performance of these methods for the benign-malignant differentiation was similar (accuracy varying from 72.8% to 76.5%). The interobserver agreement for the overall evaluation of lesion aggressiveness was considerably increased on CT compared to radiographs (Kappa of .63 vs .22). With conventional radiographs, 18 (9.7%) and 20 (10.8%) of the lesions evaluated were not seen respectively by readers 1 and 2. Among these unseen lesions, 50%-61.1% were located in the axial skeleton. Compared to radiographs, the number of lesions with cortical lysis and endosteal scalloping was 26-34% higher with CT. Conclusion: Although radiographs remain the primary imaging tool for lesions in the peripheral skeleton, CT should be performed for axial lesions. CT imaging can assess the extent of perilesional bone lysis more precisely than radiographs with a better evaluation of lesion fracture risk.

Quantitative dynamic contrast-enhanced MRI of bone marrow perfusion at the proximal femur: influence of femoral head osteonecrosis risk factor and overt osteonecrosis.

OBJECTIVE: To evaluate the MRI perfusion changes in patients with risk factors for osteonecrosis and normally appearing femoral heads prior to overt femoral head osteonecrosis. METHODS: Fifty-eight patients (105 hips) were prospectively included in this ethics committee-approved study. There were 46 hips with no image anomalies and no risk factors for osteonecrosis of the femoral head (ONFH) risk factors, 38 with ONFH risk factors and no image abnormalities, and 21 with overt ONFH. All patients underwent DCE-MRI. Semi-quantitative (peak enhancement [PE], area under the curve [AUC], time to maximum enhancement [TME]) and quantitative perfusion parameters (volume plasma, KTRANS, and KEP) were calculated. Excessive alcohol consumption, corticosteroid use, and trauma were considered major risk factors for osteonecrosis of the femoral head. RESULTS: Measured at the femoral neck and compared to the healthy hips without OFNH risk factors, PE was significantly lower in the hips of patients with OFNH risk factors. Moreover, the difference was greater in females with risk factors, who presented significantly lower PE values (p = 0.0096). A PE threshold of 1.4% yielded a 92% sensitivity and 54% specificity for the presence of associated ONFH risk factors. The hips with overt OFNH compared to those with normally appearing showed an increase of PE of 45% in the neck (p < 0.014). Various epiphyseal femoral head perfusion parameters (PE, TME, AUC, and Ktrans) presented statistically significant differences in hips with ONFH and those without (p < 0.0001). CONCLUSION: DCE-MRI can identify perfusion marrow changes related to the presence of ONFH risk factors and adjacent to osteonecrosis areas. KEY POINTS: • Bone marrow perfusion changes may occur prior to overt ONFH and extend beyond the osteonecrosis area to the entire femoral head and neck. • Peak enhancement values were significantly reduced in patients with ONFH risk factors, compared to those without. • The presence of ONFH led to a significant increase in marrow perfusion adjacent to the osteonecrosis area.

Imaging in Hip Arthroplasty Management-Part 1: Templating: Past, Present and Future.

Hip arthroplasty is a frequently used procedure with high success rates. Its main indications are primary or secondary advanced osteoarthritis, due to acute fracture, osteonecrosis of the femoral head, and hip dysplasia. The goals of HA are to reduce pain and restore normal hip biomechanics, allowing a return to the patient's normal activities. To reach those goals, the size of implants must suit, and their positioning must meet, quality criteria, which can be determined by preoperative imaging. Moreover, mechanical complications can be influenced by implant size and position, and could be avoided by precise preoperative templating. Templating used to rely on standard radiographs, but recently the use of EOS® imaging and CT has been growing, given the 3D approach provided by these methods. However, there is no consensus on the optimal imaging work-up, which may have an impact on the outcomes of the procedure. This article reviews the current principles of templating, the various imaging techniques used for it, as well as their advantages and drawbacks, and their expected results.

Imaging in Hip Arthroplasty Management Part 2: Postoperative Diagnostic Imaging Strategy.

Hip arthroplasty (HA) is a frequently used procedure with high success rates, but 7% to 27% of the patients complain of persistent postsurgical pain 1 to 4 years post-operation. HA complications depend on the post-operative delay, the type of material used, the patient's characteristics, and the surgical approach. Radiographs are still the first imaging modality used for routine follow-up, in asymptomatic and painful cases. CT and MRI used to suffer from metallic artifacts but are nowadays central in HA complications diagnosis, both having their advantages and drawbacks. Additionally, there is no consensus on the optimal imaging workup for HA complication diagnosis, which may have an impact on patient management. After a brief reminder about the different types of prostheses, this article reviews their normal and pathologic appearance, according to each imaging modality, keeping in mind that few abnormalities might be present, not anyone requiring treatment, depending on the clinical scenario. A diagnostic imaging workup is also discussed, to aid the therapist in his imaging studies prescription and the radiologist in their practical aspects.

Kinematic 4D CT case-control study of wrist in dart throwing motion "in vivo": comparison with other maneuvers.

OBJECTIVES: To compare the diagnostic performance of scapholunate gap (SLG) measurements acquired with dart throwing (DT), radio-ulnar deviation (RUD), and clenching fist (CF) maneuvers on 4D CT for the identification of scapholunate instability. METHODS: In this prospective study, 47 patients with suspected scapholunate interosseous ligament (SLIL) tears were evaluated from March 2015 to March 2020 with semiautomatic quantitative analysis on 4D CT. Five parameters (median, maximal value, range, and coefficient of variation) for SLG, lunocapitate angle (LCA), and radioscaphoid angle (RSA) obtained during DT maneuver were evaluated in patients with and without SLIL tears. CT arthrography was used as the gold standard for the SLIL status. The SLG values obtained were also compared with those obtained during CF and RUD maneuvers. RESULTS: Significant differences in all SLG- and LCA-derived parameters are found between patients with and without SLIL tears with DT (p < 0.003). The best diagnostic performance for the diagnosis of SLIL tears was obtained with median and maximal SLG values (sensitivity and specificity of 86-89% and 95%) and with maximal and range LCA values (sensitivity and specificity of 86% and 74%). No significant differences were observed for RSA values (p > 0.275). The SLG range obtained with DT maneuver was the only dynamic parameter statistically different between patients with partial and complete torn SLIL (p = 0.037). CONCLUSION: 4D CT of the wrist during DT showed a similar performance than RUD and a better performance than CF for the differentiation between patients with and without SLIL tears. KEY POINTS: • Four-dimensional computed tomography can dynamically assess scapholunate instability. • The best results for differentiating between patients with and without SLIL tears were obtained with SLG median and maximal values. • The dart throwing and radio-ulnar deviation maneuvers yielded the best results for the dynamic evaluation of scapholunate instability.

Imaging assessment of dorsal scaphoid displacement in patients with scapholunate ligament tears: what is the best option for quantitative assessment?

OBJECTIVE: To compare four different methods for the quantitative assessment of dorsal scaphoid displacement in patients with scapholunate ligament tears. METHODS: A total of 160 consecutive patients who underwent CT arthrography to evaluate a suspected scapholunate ligament tear were prospectively included in this study approved by the local ethics committee. MR images were available for 65 of these patients. Two readers independently evaluated the dorsal scaphoid displacement on conventional radiographs with the dorsal tangential line (DTL) method, the posterior radioscaphoid angle (PRSA) on both CT and MR, and the radioscaphoid congruency ratio on MR. These measurements were compared in groups of patients with and without scapholunate ligament tears. RESULTS: The measurement interobserver agreement was considered excellent for the DTL and the PRSA on CT (ICC = 0.93 and 0.88, respectively), good for the PRSA (ICC = 0.65) on MR, and moderate for the RSCR (ICC = 0.49). There was a significant increase in the values of DTL and PRSA on CT between patients with normal and ruptured SLIL (p < 0.0001). The same tendency was seen on MR-based methods, but these differences were only significant for one reader. The only method that allowed the differentiation between patients with normal and partially ruptured SLIL was the PRSA on CT. PRSA on CT yielded the best diagnostic performance for SLIL rupture (a sensitivity and a specificity of 70-82% and 70-72%). CONCLUSION: DTL on standard radiographs and the PRSA on CT are the most consistent imaging indicators of SDD with an excellent interobserver reproducibility. KEY POINTS: • Dorsal scaphoid displacement is an important prognostic factor in patients with scapholunate instability. • Quantitative assessment of dorsal scaphoid displacement can be performed on conventional radiographs and CT with an excellent reproducibility. • The posterior radioscaphoid angle on CT yielded the best diagnostic performance for the identification of scapholunate ligament tears and the only method allowing differentiation between patients with normal and partially torn ligaments.

Clinical acceptance of deep learning reconstruction for abdominal CT imaging: objective and subjective image quality and low-contrast detectability assessment.

OBJECTIVE: To evaluate the image quality and clinical acceptance of a deep learning reconstruction (DLR) algorithm compared to traditional iterative reconstruction (IR) algorithms. METHODS: CT acquisitions were performed with two phantoms and a total of nine dose levels. Images were reconstructed with two types of IR algorithms, DLR and filtered-back projection. Spatial resolution, image texture, mean noise value, and objective and subjective low-contrast detectability were compared. Ten senior radiologists evaluated the clinical acceptance of these algorithms by scoring ten CT exams reconstructed with the DLR and IR algorithms evaluated. RESULTS: Compared to MBIR, DLR yielded a lower noise and a higher low-contrast detectability index at low doses (CTDIvol ≤ 2.2 and ≤ 4.5 mGy, respectively). Spatial resolution and detectability at higher doses were better with MBIR. Compared to HIR, DLR yielded a higher spatial resolution, a lower noise, and a higher detectability index. Despite these differences in algorithm performance, significant differences in subjective low-contrast performance were not found (p ≥ 0.005). DLR texture was finer than that of MBIR and closer to that of HIR. Radiologists preferred DLR images for all criteria assessed (p < 0.0001), whereas MBIR was rated worse than HIR (p < 0.0001) in all criteria evaluated, except for noise (p = 0.044). DLR reconstruction time was 12 times faster than that of MBIR. CONCLUSION: DLR yielded a gain in objective detection and noise at lower dose levels with the best clinical acceptance among the evaluated reconstruction algorithms. KEY POINTS: • DLR yielded improved objective low-contrast detection and noise at lower dose levels. • Despite the differences in objective detectability among the algorithms evaluated, there were no differences in subjective detectability. • DLR presented significantly higher clinical acceptability scores compared to MBIR and HIR.

Ultra-high resolution computed tomography of joints: practical recommendations for acquisition protocol optimization.

BACKGROUND: To assess the influence on the spatial resolution of various Ultra-high-resolution computed tomography (CT) parameters and provide practical recommendations for acquisition protocol optimization in musculoskeletal imaging. METHODS: All acquisitions were performed with an Ultra-high resolution scanner, and variations of the following parameters were evaluated: field-of-view (150-300 mm), potential (80-140 KVp), current (25-250 mAs), focal spot size (0.4×0.5 to 0.8×1.3 mm2), slice thickness (0.25-0.5 mm), reconstruction matrix (512×512 to 2048×2048), and iso-centering (up to 85 mm off-center). Two different image reconstruction algorithms were evaluated: hybrid iterative reconstruction (HIR) and model-based iterative reconstruction (MBIR). CATPHAN 600 phantom images were analyzed to calculate the number of visible line pairs per centimeter (lp/cm). Task transfer function (TTF) curves were calculated to quantitatively evaluate spatial resolution. Cadaveric knee acquisitions were also performed. RESULTS: Under the conditions studied, the factor that most intensely influenced spatial resolution was the matrix size (additional visualization of up to 8 lp/cm). Increasing the matrix from 512×512 to 2048×2048 led to a 28.2% increase in TTF10% values with a high-dose protocol and a 5.6% increase with a low-dose protocol with no change in the number of visually distinguishable line pairs. The second most important factor affecting spatial resolution was the tube output (29.6% TTF10% gain and 5 additional lp/cm visualized), followed by the reconstruction algorithm choice and lateral displacement (both with a 4 lp/cm gain). Decreasing the slice thickness from 0.5 to 0.25 mm, led to an increase of 3 lp/cm (from 17 to 20 lp/cm) and a 17.3% increase in TTF10% values with no change in the "in-plane" spatial resolution. CONCLUSIONS: This study provides practical recommendations for spatial resolution optimization using Ultra-high-resolution CT.

Four-Dimensional CT Analysis of Dorsal Intercalated Segment Instability in patients with Suspected Scapholunate Instability.

Background In this study we sought to evaluate the contribution of dynamic four-dimensional computed tomography (4DCT) relative to the standard imaging work-up for the identification of the dorsal intercalated segment instability (DISI) in patients with suspected chronic scapholunate instability (SLI). Methods Forty patients (22 men, 18 women; mean age 46.5 ± 13.1 years) with suspected SLI were evaluated prospectively with radiographs, arthrography, and 4DCT. Based on radiographs and CT arthrography, three groups were defined: positive SLI ( n = 16), negative SLI ( n = 19), and questionable SLI ( n = 5). Two independent readers used 4DCT to evaluate the lunocapitate angle (LCA) (mean, max, coefficient of variation [CV], and range values) during radioulnar deviation. Results The interobserver variability of the 4DCT variables was deemed excellent (intraclass correlation coefficient = 0.79 to 0.96). Between the three groups, there was no identifiable difference for the LCA mean . The LCA max values were lower in the positive SLI group (88 degrees) than the negative SLI group (102 degrees). The positive SLI group had significantly lower LCA cv (7% vs. 12%, p = 0.02) and LCA range (18 vs. 27 degrees, p = 0.01) values than the negative SLI group. The difference in all the LCA parameters between the positive SLI group and the questionable SLI group was not statistically significant. When comparing the negative SLI and questionable SLI groups, the LCA cv ( p = 0.03) and LCA range ( p = 0.02) values were also significantly different. The best differentiation between patients with and without SLI was obtained with a LCA cv and LCA range threshold values of 9% (specificity of 63% and sensitivity of 62%) and 20 degrees (specificity of 71% and sensitivity of 63%), respectively. Conclusion In this study, 4DCT appeared as a quantitative and reproducible relevant tool for the evaluation of DISI deformity in cases of SLI, including for patients presenting with questionable initial radiography findings. Level of evidence This is a Level III study.