CT-guided procedures: an initial experience

A semi-automated robotic system for percutaneous interventions

PURPOSE

A robotic assistive device is developed for needle-based percutaneous interventions. The aim is a hybrid system using both manual and actuated robotic operation in order to obtain a device that has a large workspace but can still fit in the gantry opening of a CT scanner. This will enable physicians to perform precise and time-efficient CT-guided percutaneous interventions. The concept of the mechanics and software of the device is presented in this work.

METHODS

The approach is a semi-automated robotic assistive device, which combines manual and robotic positioning to reduce the number and size of necessary motors. The system consists of a manual rough positioning unit, a robotic fine positioning unit and an optical needle tracking unit. The resulting system has eight degrees of freedom, of which four are manual, which comprise encoders to monitor the position of each axis. The remaining four axes are actuated axes for fine positioning of the needle. Cameras are attached to the mechanical structure for 3D tracking of the needle pose. The software is based on open-source software, mainly ROS2 as robotic middleware, Moveit2 for trajectory calculation and 3D Slicer for needle path planning.

RESULTS

The communication between the components was successfully tested with a clinical CT scanner. In a first experiment, four needle insertions were planned and the deviation of the actual needle path from the planned path was measured. The mean deviation from the needle path to the target point was 21.9 mm, which is mainly caused both by translational deviation (15.4 mm) and angular deviation (6.8°) of the needle holder. The optical tracking system was able to detect the needle position with a mean deviation of 3.9 mm.

CONCLUSION

The first validation of the system was successful which proves that the proposed concept for both the hardware and software is feasible. In a next step, an automatic position correction based on the optical tracking system will be integrated, which is expected to significantly improve the system accuracy.

Rescue computed tomography-guided drainage of a giant mediastinal mature teratoma causing airway obstruction prior to surgical resection: a case report

BACKGROUND

Giant mediastinal mature teratomas may cause airway obstruction or decreased venous return due to the mass effect. Preoperative stabilization of the respiratory and circulatory systems is important for perioperative management to safely perform surgery, including general anesthesia. However, to the best of our knowledge, there are only a few reports regarding the preoperative computed tomography (CT)-guided drainage of mediastinal tumors.

CASE PRESENTATION

A 30-year-old woman was admitted to the emergency room with sudden dyspnea. CT findings revealed a giant cystic mass in the anterior mediastinum compressing the trachea and the right main bronchus. The patient was intubated and CT-guided drainage of the fluid content of the cyst was performed to decompress the airway obstruction. Thereafter, the mediastinal tumor was resected during elective surgery and pathologically diagnosed as a mature teratoma.

CONCLUSIONS

Rescue preoperative CT-guided drainage of a giant mediastinal mature teratoma allowed safe general anesthesia and surgery by releasing the airway obstruction.

Minimally invasive biopsy in retroperitoneal tumors

Minimally invasive biopsy procedures have proven over the years to be essential for obtaining a correct diagnosis of retroperitoneal tumors, that allows proper therapeutical conduct. These procedures offer valuable tissue fragments for histopathological examination, that permits the distinction between benign and malignant tumors, identifying the tumors that can benefit from neo-adjuvant treatments, such as chemotherapy or radiotherapy and those that have a direct surgical indication. We have searched the existing data regarding minimally invasive biopsy in retroperitoneal tumors using the PubMed database, in order to evaluate the role of this procedure in establishing a correct diagnosis, as well as to find out the risks of tumor cell seeding and local recurrence after needle biopsy. The risk of tumor cell seeding is very low (<2%) and in some cases, it is considered negligible (<0.5%). Compared to open biopsy, needle biopsy seems to be associated with a significantly lower risk of tumor cell seeding. According to the existing data, the incidence of needle track tumor cell seeding also depends on the histological type of the tumors. Image-guided retroperitoneal biopsy has proven to be low cost, accessible, and a reliable procedure (in terms of diagnostic accuracy), usually associating with a low rate of complications and a low risk of tumor seeding. Several authors have underlined the importance of the retroperitoneal approach and the association with a co-axial imaging technique in order to avoid potentially deadly complications.