We report that a 2,2':6',2″-terpyridylmacrocycle-Ni complex can efficiently mediate the threading of two alkyl chains with bulky end groups in an active metal template sp(3)-carbon-to-sp(3)-carbon homocoupling reaction, resulting in a rare example of a doubly threaded [3]rotaxane in up to 51% yield. The unusual architecture is confirmed by X-ray crystallography (the first time that a one-ring-two-thread [3]rotaxane has been characterized in the solid state) and is found to be stable with respect to dethreading despite the large ring size of the macrocycle. Through such active template reactions, in principle, a macrocycle should be able to assemble as many axles in its cavity as the size of the ring and the stoppers will allow. A general method for threading multiple axles through a macrocycle adds significantly to the tools available for the synthesis of different types of rotaxane architectures.

The objective of this study is to assess artifact reduction and image quality using dual-energy computed tomography (DECT) and metal artifact reduction techniques in patients with metallic implants. Methods: Forty patients with metallic implants, who had targeted CT performed by DECT during March to September 2018, were prospectively recruited. Post-processing with monoenergetic extrapolation at 70 and 150 keV was performed. Forty matched controls with metallic implants with single-energy CT (SECT) performed were selected. Attenuation value, noise, and signal-tonoise ratio (SNR) at the site of maximal artifact were measured at muscle and fat areas. Image quality of three sets of images (70 keV, 150 keV, and SECT) was assessed by two independent reviewers using a 5-point Likert-type scale. Statistical analysis of measured values, Likert-type scales, and radiation doses (volume CT dose index (CTDI vol)) of DECT and SECT were performed with Mann-Whitney U test. Results: As compared to SECT, high keV reconstruction of DECT show (1) significantly higher values within muscle and fat surrounding the implant (DECT vs. SECT-muscle: À96 Hounsfield units (HU) vs. À405 HU, fat: À115 HU vs. À301 HU; p < 0.001), (2) significantly lower mean image noise (75 HU vs. 129 HU; p ¼ 0.02), and (3) higher SNR (À0.8 vs. À4.3; p < 0.001). In addition, image quality of high keV reconstruction was rated superior to the other two groups on Likert-type scales (p < 0.001). The mean radiation doses (CTDI vol) were comparable between DECT and SECT (14.2 mGy vs. 19.3 mGy; p ¼ 0.08). Conclusion: For patients with metallic implants, monoenergetic extrapolation of DECT at high keV can reduce metal artifacts, increase SNR, and improve qualitative image quality at comparable radiation dose.

A 46-year-old man presented to the Department of Orthopaedics and Traumatology, Pamela Youde Nethersole Eastern Hospital in February 2004 with a 3-month history of self-detected left thigh mass. It was of spontaneous onset with no history of trauma, associated pain, weakness, or numbness. The patient had full range of movement and no lymphadenopathy was noted. Magnetic resonance imaging (MRI) [ Fig 1] revealed a large area of infiltrative soft-tissue Hong Kong Med J 2019;25:149-51 https://doi.org/10.12809/hkmj164921 thickening at the medial aspect of the left distal thigh and involved the subcutaneous layer. The lesion measured 8.4 × 3.4 × 11.2 cm (anteroposterior × transverse × longitudinal) and was characterised by T1-weighted (T1W) hypointense to isointense and T2-weighted (T2W) fat-suppressed hyperintense signals with internal heterogeneity. Internal foci of hypointensity in the T2W fat-suppressed images were noted. An internal reticular pattern of septal thickening was also found. There was enhancement after gadolinium contrast administration. The margin of the lesion was well delineated from the underlying vastus medialis and sartorius muscles with no features of muscular invasion or destruction. The knee joint was unremarkable and bone marrow signal was normal. The neurovascular bundle was also intact. Overall features were non-specific for either inflammatory or neoplastic pathology.Microscopic examination of an incisional biopsy over the left vastus medialis with a wedge of skin and subcutaneous tissue revealed infiltrate in the subcutis and to a lesser extent the deep dermis. The infiltrate consisted of lymphocytes and a low number of plasma cells. Immunohistochemical stains showed mainly T-cells and some B-cells. Occasional areas with aggregates of paler histiocytic cells were present and suggested granuloma formation. Stains for acid-fast bacilli and fungus were negative. The paler histiocytic cells were S100-positive and showed lymphophagocytosis (Fig 2). Molecular study by polymerase chain reaction showed no clonal T-cell proliferation. The overall features were suggestive of Rosai-Dorfman disease (RDD).Radical excision of the lesion was performed subsequently and included the epimysium of the gracilis, sartorius and aponeurosis of the vastus medialis. The excision margin in the radial excision of the lesion was 2 cm. Microscopic examination revealed that the mass in the subcutis was composed of nodules or aggregates of lymphohistiocytic cells separated by areas of fibrosis. The cellular aggregates were composed of dark areas with plasma cells and lymphocytes and pale areas with CASE REPORT FIG 1. (a) Axial T1-weighted magnetic resonance (MR) image showing a large area of infiltrative soft tissue thickening involving the subcutaneous layer at the medial aspect of the thigh with hypo-to iso-intense signals (arrow). (b) Axial T2-weighted fat-suppressed MR image showing hyperintense signals with internal heterogeneity and foci of hypointensities. Internal reticular pattern of septal thickening was pre...

Objective: The first objective of this study is to determine the reference Tibial Tubercle-Trochlear Groove (TT-TG) distance on MRI in Southern Chinese population. The second objective is to investigate the correlation between TT-TG distance and (i) age, (ii) sex, (iii) height, (iv) weight and (v) Body Mass Index (BMI) respectively. Method: Three hundred MRI knees performed in two different centres between August 2017 and October 2018 were included. All patients were prospectively recruited after MRI referral from Orthopaedics department. The TT-TG distances were measured by two radiologists independently. Measurement reliability was assessed using intraclass correlation coefficient (ICC). One sample t-test was used to compare the results between this study and other published studies. Spearman’s rank correlation coefficient was used to determine correlations between the TT-TG distance and age, sex, height, weight and BMI respectively. Result: There was no statistical significance between the mean of TT-TG distances from the two radiologists ( P-value = 0.32). The measurement reliability was excellent (ICC = 0.922 ± 0.02). The mean of averaged TT-TG distance was 8.32 ± 0.33 mm (range 2.01 to 17.48 mm). There were no statistical significant differences in means of TT-TG distance between laterality and gender. There were statistically significant correlations between (i) TT-TG distance and age ( p-value = 0.009), and (ii) TT-TG distance and height ( p-value = 0.014). Conclusion: The reference TT-TG distance on MRI in Southern Chinese population was 8.32 ± 0.33 mm. Statistically significant correlations were established between (i) TT-TG distance and age; and (ii) TT-TG distance and height.

Chronic tophaceous gout is a common disease but rarely found in the head and neck region. Here we report a case of a middle aged male who presented with a mass over the right side of the nasal bridge. CT of the paranasal sinuses revealed a tophi lesion in the right nasal bridge with erosion of the underlying nasal bone. The mass was excised and histologically confirmed to be a gouty tophus. This case report illustrates how a common disease presented in an uncommon location could pose a diagnostic challenge.