Takefumi Yasunaga

Nanoparticles of Adaptive Supramolecular Networks Self-Assembled from Nucleotides and Lanthanide Ions

Amorphous nanoparticles of supramolecular coordination polymer networks are spontaneously self-assembled from nucleotides and lanthanide ions in water. They show intrinsic functions such as energy transfer from nucleobase to lanthanide ions and excellent performance as contrast enhancing agents for magnetic resonance imaging (MRI). Furthermore, adaptive inclusion properties are observed in the self-assembly process: functional materials such as fluorescent dyes, metal nanoparticles, and proteins are facilely encapsulated. Dyes in these nanoparticles fluoresce in high quantum yields with a single exponential decay, indicating that guest molecules are monomerically wrapped in the network. Gold nanoparticles and ferritin were also wrapped by the supramolecular shells. In addition, these nucleotide/lanthanide nanoparticles also serve as scaffolds for immobilizing enzymes. The adaptive nature of present supramolecular nanoparticles provides a versatile platform that can be utilized in a variety of applications ranging from material to biomedical sciences. As examples, biocompatibility and liver-directing characteristics in in vivo tissue localization experiments are demonstrated.

Construct validity for eye-hand coordination skill on a virtual reality laparoscopic surgical simulator.

BackgroundThis study was carried out to investigate whether eye-hand coordination skill on a virtual reality laparoscopic surgical simulator (the LAP Mentor) was able to differentiate among subjects with different laparoscopic experience and thus confirm its construct validity.MethodsA total of 31 surgeons, who were all right-handed, were divided into the following two groups according to their experience as an operator in laparoscopic surgery: experienced surgeons (more than 50 laparoscopic procedures) and novice surgeons (fewer than 10 laparoscopic procedures). The subjects were tested using the eye-hand coordination task of the LAP Mentor, and performance was compared between the two groups. Assessment of the laparoscopic skills was based on parameters measured by the simulator.ResultsThe experienced surgeons completed the task significantly faster than the novice surgeons. The experienced surgeons also achieved a lower number of movements (NOM), better economy of movement (EOM) and faster average speed of the left instrument than the novice surgeons, whereas there were no significant differences between the two groups for the NOM, EOM and average speed of the right instrument.ConclusionsEye-hand coordination skill of the nondominant hand, but not the dominant hand, measured using the LAP Mentor was able to differentiate between subjects with different laparoscopic experience. This study also provides evidence of construct validity for eye-hand coordination skill on the LAP Mentor.

Quantitative assessment of rotatory instability after anterior cruciate ligament reconstruction

Background Anterior cruciate ligament reconstruction successfully reduces anterior knee instability, but its effect on rotatory stability is not fully understood. In addition, a definitive method for the quantitative evaluation of rotatory instability remains to be established. Hypothesis Measurement of anterolateral tibial translation by open magnetic resonance imaging could positively correlate with the clinical grading of the pivot-shift test and would clarify residual rotatory abnormalities not shown by conventional methods for measurement of anterior stability. Study Design Controlled laboratory study. Methods An anterior cruciate ligament—reconstructed group (n = 21) and an anterior cruciate ligament—deficient group (n = 20) were examined using a Slocum anterolateral rotatory instability test in open magnetic resonance imaging. Anterior tibial translation was measured at the medial and lateral compartments by evaluating sagittal images. Clinical knee stability was evaluated before the above measurement using the pivot-shift test, KT-2000 arthrometer, and stress radiography. A cutoff value for anterolateral tibial translation relating to pivot-shift was determined using a receiver operating characteristic curve. Results Side-to-side differences of anterolateral tibial translation correlated with clinical grade of the pivot-shift test and stress radiography but not with KT-2000 arthrometry in both groups. The cutoff value was established as 3.0 mm. Although the mean anterolateral translation showed no difference, 9 reconstructed knees revealed greater than 3 mm of anterolateral tibial translation, whereas only 3 uninjured knees did. Conclusion Measurement using an open magnetic resonance imaging successfully quantified the remaining rotatory instability in anterior cruciate ligament—reconstructed knees. Clinical Relevance This method is a useful means for quantifying anterior cruciate ligament function to stabilize tibial rotation.

Objective assessment of laparoscopic suturing skills using a motion-tracking system

BackgroundLaparoscopic suturing skills are important for advanced laparoscopic surgery. However, objective assessment of these skills has not yet been established. The aim of this study was to assess the laparoscopic suturing skills of novice and experienced surgeons using an electromagnetic motion-tracking system.MethodsA total of 18 surgeons, who were all right-handed, were divided into the following two groups according to their experience as an operator in laparoscopic surgery: 9 novice surgeons (fewer than 10 laparoscopic procedures) and 9 experienced surgeons (more than 50 laparoscopic procedures). The subjects performed an intracorporeal suturing task in an inanimate box laparoscopic trainer while the movements of their forceps were evaluated using an electromagnetic motion-tracking system. Their laparoscopic skills were assessed on the basis of the time, path length, and average speed of the forceps in each hand.ResultsExperienced surgeons completed the suturing task significantly faster than novice surgeons did. The left path length was significantly shorter for experienced surgeons than for novice surgeons, whereas the right path lengths did not differ. The right average speed of knot tying was significantly faster for experienced surgeons than for novice surgeons, whereas the left average speeds did not differ.ConclusionsEvaluation of psychomotor skills in laparoscopic suturing using an electromagnetic motion-tracking system revealed better results for experienced surgeons than for novice surgeons in terms of the time taken, left path length, and right speed of knot-tying. Furthermore, surgical proficiency due to experience can affect surgical dexterity of each hand differently. The present study also demonstrates the efficacy of this system for objective evaluation of laparoscopic suturing skills.

Assessment of Anterolateral Rotatory Instability in the Anterior Cruciate Ligament–Deficient Knee Using an Open Magnetic Resonance Imaging System

Background In the clinical evaluation of the anterior cruciate ligament—deficient knee, anterolateral rotatory instability is assessed by manual tests such as the pivot-shift test, which is subjective and not quantitative. Hypothesis The anterolateral rotatory instability in an anterior cruciate ligament—deficient knee can be quantified by our newly developed method using open magnetic resonance imaging. Study Design Controlled laboratory study. Methods Eighteen subjects with anterior cruciate ligament—deficient knees and 18 with normal knees were recruited. We administered the Slocum anterolateral rotatory instability test in the open magnetic resonance imaging scanner and scanned the sagittal view of the knee. The anterior displacements of the tibia at the medial and lateral compartments were measured. Furthermore, we examined 14 anterior cruciate ligament—deficient knees twice to assess intraobserver and interobserver reproducibility and evaluated the difference and interclass correlation coefficient of 2 measures. Results In the anterior cruciate ligament—deficient knee, displacement was 14.4 ± 5.5 mm at the lateral compartment and 1.6 ± 2.3 mm at the medial compartment; in the normal knee, displacement was 0.7 ± 1.9 mm and —1.1 ± 1.2 mm, respectively. The difference and interclass correlation coefficient between 2 repeated measures at the lateral compartment were 1.0 ± 0.7 mm and .98 for intraobserver reproducibility and 1.1 ± 0.7 mm and .91 for interobserver reproducibility. Conclusion This method is useful to assess the anterolateral rotatory instability of the anterior cruciate ligament—deficient knee. Clinical Relevance This method can be used in the clinical assessment of anterior cruciate ligament stability, such as comparing studies of graft positions or 2-bundle anatomic reconstruction and the conventional 1-bundle technique.