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Design of a steerable needle for low dose rate brachytherapy of the prostate

Master thesis (2022) - H.M. Sickler, J.J. van den Dobbelsteen, M. de Vries

Prostate cancer is the most frequently diagnosed cancer type among men, and the third deathliest form of cancer. Several treatments are available to treat prostate cancer. Low Dose Rate Brachytherapy (LDR BT) is one of them, which inserts permanent radioactive seeds into the pros ...

Prostate cancer is the most frequently diagnosed cancer type among men, and the third deathliest form of cancer. Several treatments are available to treat prostate cancer. Low Dose Rate Brachytherapy (LDR BT) is one of them, which inserts permanent radioactive seeds into the prostate using a needle. The literature review performed prior to this thesis, investigates if LDR BT is an effective method and how the quality of life is affected by the treatment compared to other treatments. Furthermore, the various anatomical variations that could intervene with the procedure are analyzed and how they are currently dealt with. It was found that during this treatment multiple complications can arise; first pubic arch interference could prevent the needle from reaching all parts of the prostate. Second, unwanted needle deflection can cause incorrect dose distribution, and third, delicate tissues like the urethra can obstruct the path of the needle. The introduction of a steerable needle in the field of brachytherapy could have the potential of treating patients with particular anatomical variations, add more maneuverability for the surgeon to steer around certain tissues and adjust unwanted needle deflections. All contributing to an accurate dose distribution and therefore an improved quality of life of the patient.

This thesis aims to design and develop a steerable needle for LDR BT of the prostate along with defining the design parameters of the steering capabilities to predict the bending of the needle. The needle should have a lumen for radioactive seeds to pass through, should use the steering mechanism of the preceding high dose rate wire needle and it should be able to steer 30mm laterally over 150mm insertion in order to reach the entire prostate.

Multiple theories are developed to predict the deflection behaviour of the needle. A theory that can predict the needle tip path, two theories that predict the distal deflection in air, and lastly a theory that predicts the deflection in tissue. One of the theories that predict the distal deflection in air is based on the proximal angle and the other one on the proximal force. To test these theories, a steerable wire needle, made of spring steel, for high dose rate brachytherapy is borrowed. From these experiments it can be concluded that the theory for the prediction of the needle tip path gives results close to the measured values and the prediction of the distal deflection based on proximal force give adequate results with an error of 1.77mm ±1.6mm. This error is in between the acceptable threshold of 2mm-5mm. The other two models presented errors of 15.1mm ±15.2mm and 14.4mm ±14.6mm, which give inaccurate predictions and are therefore not used as basis for the design of the steerable needle. An analysis is performed on the individual parameters within the two models. This provides insight into which variables need to be adjusted to design a steerable needle that complies with the requirements.

Based on the two models and the analysis of the individual parameters, a steerable needle that complies with the requirements, is designed, manufactured and tested. The manufacturing of the needle was limited by the availability of materials, causing the inner lumen to be slightly smaller than initially designed. The first tests are performed in air to compare the results with the previous experiments done with the wire spring steel needle and to verify the prediction models. The needle tip path and distal deflection based on the proximal force predictions both proof to be adequate models with the latter having an error of 2.75mm ±2.99mm. The steerable nitinol needle with a lumen, is also tested in tissue stimulant to provide a proof of principle and verify the theory of deflection in tissue. It is demonstrated that the needle can steer within the tissue stimulant, and insert an object though its lumen into the tissue. The model for the prediction of the deflection in tissue can be proven empirically. In addition, the prediction of the distal deflection based on the proximal force can also be applied for bending in tissue, if a constant is added to account for the bevel tip of the needle.

To provide an additional substantiation for the prediction model, a third needle is tested in air. This needle is borrowed and is intended to be used in high dose rate brachytherapy. This needle, made of tungsten, also proofs that the model can make adequate predictions with an error of 1.76mm ±1.4mm.

One of the requirements of the needle is that the inner lumen must accommodate the passing of a radioactive seed. Due to the unavailability of certain materials this was not accomplished. Therefore, a theoretical design is made with a larger inner lumen. For further research this design can be manufactured and tested.

The steerable needle presented in this thesis provides a proof of principle for a steerable needle with a lumen. It could have the potential of overcoming the anatomical obstacles presented in the literature review and therefore aiding in an accurate dose distribution. Furthermore, it can also provide the surgeon with the capability of adjusting unwanted deflection created by the needle. In addition, by analyzing the variables that influence the steering, a model is made that can predict the deflection based on the proximal force applied.

Minimally Invasive Sentinel Lymph Node Biopsy

Finding a less invasive alternative to an existing procedure

Master thesis (2021) - M.I. Joosen, J.J. van den Dobbelsteen, E.E.A.P Mulder, M. de Vries, D.H. Plettenburg, D.J. Grünhagen

Sentinel lymph node biopsy (SLNB) is a procedure that is used to determine the stage of disease of melanoma patients and determine further treatment. However, the morbidities accompanied with this procedure are not negligible (e.g., wound infection, lymphoedema and seroma). With ...

Sentinel lymph node biopsy (SLNB) is a procedure that is used to determine the stage of disease of melanoma patients and determine further treatment. However, the morbidities accompanied with this procedure are not negligible (e.g., wound infection, lymphoedema and seroma). With the goal reduce the incidence of morbidities, this thesis investigated the possibility of minimally invasive sentinel lymph node biopsy (MISLNB). Preceding this thesis, a literature study was written by the writer of this thesis to examine whether there was already a possible solution for this problem. This literature study showed that there are no off the shelf available solutions for MISLNB. Therefore, three solution with the reduction of comorbidities and the importance of \textit{en bloc} excision at their core were proposed. These solutions were found through literature, patents, and some ingenuity. The solution with the highest probability was selected to develop further. This concept was then subjected to different experiments to determine whether it was viable option for MISLNB. This study also aimed to fill some of the missing data on the material behaviour of lymph nodes (LN), specifically stress-strain behaviour under compression. By using a set of requirements one solution was selected to be the most viable given the available information. This solution was called the Pull-and-Harvest method. This concept uses a vacuum to grip the sentinel lymph node (SLN) and stash it in a tube, hereafter a snare would cut the lymph ducts and blood vessels. This concept scored well mainly due to the low risk of damaging SLN and its simplicity. The next step was to determine whether this concept was a feasible solution to MISLNB. The problem was divided into three subproblems to estimate this feasibility. The first being the force required to separate the SLN from its surrounding tissue. Since no data on this subject was available a simplified model was created to estimate this value based on the stretch of lymph ducts. The second part of this problem was, determining the force required to stash the SLN inside the tubular volume. Finally, the maximal force of two silicon suction cups was determined. From these experiments several conclusions could be drawn: the conical silicon suction cups used in this study are very inefficient (10%) efficiency) for gripping LNs, these suction cups will stash the LNs but probably not with the additional estimated adherence force and the risk of damaging the LN using a vacuum seems to be low. Based on these observations during these experiments possible ways of were suggested and could make the Pull-and-Harvest a viable procedure. Lastly stress-strain behaviour of LNs could be described using an exponential relationship. This thesis outlines the problem of MISLNB and highlights the areas of interest for further research. However, there is more research and development needed to find a definitive solution for MISLNB.

The design of a brain and tumor phantom

Focused on mimicking the stiffness of the brain and glioblastoma multiforme tumor tissue

Master thesis (2021) - D.J. van der Molen, J.J. van den Dobbelsteen, B.H.W. Hendriks, M. de Vries

Glioblastoma multiforme tumors (GBM) are the most frequent and aggressive brain tumor type and have a very low survival rate. In order to improve the patient’s outcome for a patient suffering from GBM the production of brain phantoms can be of great help. A brain phantom can be u ...

Glioblastoma multiforme tumors (GBM) are the most frequent and aggressive brain tumor type and have a very low survival rate. In order to improve the patient’s outcome for a patient suffering from GBM the production of brain phantoms can be of great help. A brain phantom can be used for multiple purposes, such as neurological planning, training and for testing new medical devices. Nevertheless, no brain phantom has been created with realistic stiffness yet. Investigating the stiffness of the brain is challenging, due to the complexity of the brain and for not being able to touch it in person. However, through a relatively new technology called magnetic resonance elastography (MRE), it is possible to examine the stiffness of the brain. Hence, the
objective for this thesis was to develop a brain phantom with a GBM tumor with similar stiffness compared to the biological human brain and tumor tissue.

In the literatureMRE data can be found on the complex shear modulus of the brain and tumors, which can be converted to an indicative Young’s modulus (E*). The indicative Young’s modulus will be used as a guideline for the desired stiffness needed for the production of a brain phantom. First various polyvinyl alcohol (PVA) samples were made and a compression test was carried out to derive the Young’s modulus (E). By comparing E with E* , it can be seen which PVA sample most resembles the brain and tumor tissue. Thereafter, the head phantom is created, which consists of 3 different production processes; production of the mould, production of the skull and production of the brain phantom. Firstly, the moulds for the brain phantom and tumor are 3D printed using polylactic acid (PLA). The skull phantom is derived from a patient specific CT scan, and is 3D printed with PLA. The brain phantom itself is made of 4,8 wt% PVA and 2 freeze-thaw (FT) cycles, and the tumor phantom is made of 5,2 wt% PVA and 1 FT cycle. The mass fractions and FT cycles have the closest stiffness compared to real brain and tumor tissue and were therefore selected. Within the brain phantom a hollow space is created where the tumor can be placed in. For a parallel project of the TU Delft and Utrecht University a brain phantom was required. For this specific case a brain phantom was produced with barium sulfate (BaSO4), which functions as a contrast additive for CT and MRI. Therefore, the second brain phantom
was made of 4,8 wt% PVA, 1 wt% BaSO4 and 2 FT cycles. The tumor phantom with BaSO4 failed and therefore the first tumor without BaSO4 was used for this use case. An experiment was carried out where a HoMS substance was injected into the tumor phantom. During the experiment 9 CT scans and 2 MRI scans were carried out. Due to the MRI and CT scans it could be investigated whether the tumor was in place and
whether the brain phantom was visible in the CT and MRI. After the use case one more mechanical test was carried out consisting of PVA samples with BaSO4 to examine whether BaSO4 has an effect on the stiffness of the phantom.

The results of the mechanical test led to a desired mass fraction and FT cycle that can represent the brain and tumor phantom. These were immediately used for the production of the brain and tumor phantom. The Young’s modulus of the brain phantom (E = 8,9 kPa) is a little stiffer compared to the actual brain tissue (E* =
9,57 kPa). The Young’s modulus of the tumor phantom (E = 5,8 kPa) is softer compared to the GBM tissue (E* = 4,93 kPa). However, adding BaSO4 to the PVA solution changed the stiffness of the PVA samples, has had an effect on the compactness of the samples, and the BaSO4 did not dissolve properly. In the results of the CT and MRI scans it was found that the BaSO4 was only visible in the inferior part of the brain. In addition, the brain and tumor phantom were clearly visible in theMRI and CT scans. It is therefore not recommended to use BaSO4 for future research. Furthermore, the CT scan showed that the tumor phantom was well surrounded
by the brain phantom and stayed in place even when the tumor was inserted by a cannula. The results show that a brain phantom with a tumor phantom can be produced. However, some improvements to the design of the mould are needed, because the mould was leaking, which subsequently led to an anatomically incorrect brain phantom.

This thesis project leads to the following conclusion; it is possible to produce a brain phantom with a GBM tumor phantom with comparable stiffness to the actual brain and GBM tissue. However, it can not be concluded that the various stiffness’s are exactly the same as the actual brain and GBM tissue, but it is close to the values found in the literature.

The influence of rotation on the precision of needle end-point position in lateral direction for biopsy

Master thesis (2021) - L.P.N. Koopman, J.J. van den Dobbelsteen, M.C. Plooij, M. de Vries

Breast cancer is currently the most prevalent type of cancer. The concluding diagnosis can be obtained with an MRI-guided biopsy. However, due to respiratory movement and human error, the procedure can require multiple attempts, resulting in harmful consequences. To reach the tar ...

Design and Development of a prostate phantom model to mechanically mimic human tissue

To test new instruments developed for brachytherapy

Master thesis (2020) - E. Veldman, J.J. van den Dobbelsteen, M. de Vries, I. Apachitei

Prostate cancer is the most frequently diagnosed type of cancer among males. Brachytherapy has become a common treatment for this disease. In this form of radiotherapy, sealed radiation sources are placed through a implant catheters inside the prostate. This treatment affects the ...

Prostate cancer is the most frequently diagnosed type of cancer among males. Brachytherapy has become a common treatment for this disease. In this form of radiotherapy, sealed radiation sources are placed through a implant catheters inside the prostate. This treatment affects the tumor cells locally and reduces damage to healthy tissues. However, accessing all relevant areas is met by difficulties. Innovating brachytherapy instruments can overcome these challenges. These new instruments need to be tested in a lab environment before patient testing is allowed. Phantom models provide a good validation model for testing new medical instruments. The goal of this study is to design and develop a cancerous prostate phantom model which can be used to test newly developed instruments for brachytherapy.
A material study was conducted to find the best mechanically tissue-mimicking materials. The effects of different concentrations, varying volumes, coolant additive and dimethyl-sulfoxide additive on the Young's modulus of poly-vinyl alcohol was tested. Unconfined compression tests were performed after each freeze-thaw cycle for a total of 7 cycles. These results showed that poly-vinyl alcohol can form material which, based on its Young's modulus, can mimic prostate tissue and adipose tissue. An increase in poly-vinyl alcohol concentration, volume, coolant additive, dimethyl-sulfoxide additive and the number of freeze-thaw cycles were each found to increase the Young's modulus of the material.
Three cancerous prostate phantom models were made of poly-vinyl material with each a different stiffness value achieved by varying the poly-vinyl alcohol concentrations. A low Young's modulus for model 1, medium for model 2 and high for model 3. The poly-vinyl alcohol was solved in a mixture of distilled water:DMSO (10:90 ratio) to produce a transparent material. Each model included a prostate, urethra and surrounding adipose tissue. The models were surrounded by a transparent casing which included an opening and template for needle insertion at the front. A pubic bone was added to model 2 and 3 to simulate prostate blockage by this tissue. Model 1 and 2 did not achieve the transparency that was required. The transparency was found to be sufficient in model 3.
A needle insertion experiment was conducted to validate the prostate phantom models. An 18Gauge brachytherapy needle was inserted 13, 10 and 20 times in model 1, 2 and 3 respectively with a velocity of 5 mm/s. Mean peak forces, describing the force upon puncture of the prostate material, for model 1 (0.57 N) and 2 (3.54 N) were lower than multiple peak forces found in literature. The median peak force of model 3 (6.17 N) came close to the peak force found during in patients with prostate cancer (6.28 N) in the study of Podder et al. (2006). Higher Young's moduli values produced higher peak forces. The insertion force in the adipose tissue of the models was lower than the results found in literature.
This study has shown that poly-vinyl alcohol can function as an easily controlled tissue mimicking material. The material study created an overview of the effects of concentration, volume, coolant, DMSO and freeze-thaw cycles on the Young's modulus of poly-vinyl alcohol. An easy to manufacture cancerous prostate phantom model was made of poly-vinyl alcohol and DMSO. Model 3 developed in this project can function as a test model for newly developed instruments meant for brachytherapy.

The design of a manually operated compliant mechanism steerable needle for high dose-rate brachytherapy of the prostate

Master thesis (2020) - M.M. Nobel, J.J. van den Dobbelsteen, M. de Vries

Prostate cancer is the most common cancer in men and third in terms of mortality. High dose rate brachytherapy is a common and effective treatment to treat this cancer. High dose rate brachytherapy requires the implantation of several needles into the prostate trough which a radi ...

Prostate cancer is the most common cancer in men and third in terms of mortality. High dose rate brachytherapy is a common and effective treatment to treat this cancer. High dose rate brachytherapy requires the implantation of several needles into the prostate trough which a radiation source is introduced. This implantation can present a number of difficulties. Steerable needles have been proposed to address some of these difficulties. The literature review in Appendix A has identified a number of possible advantages using a steerable needle could have in high dose-rate brachytherapy of the prostate. This thesis aims to develop a steerable needle system enabling the surgeon to place a needle more accurately, combat pubic arch interference, and circumvent ureteral occlusion while not interfering in the general course of the procedure.

This steerable needle was developed according to several design guidelines and optimisation parameters. A mathematical model and simulation were used to predict the behaviour of the needle and identify which parameters influence its functioning. By developing a number of concepts and evaluating their performance according to the set design guidelines a final design was formulated. A phantom was developed to be able to evaluate the performance of the design. By comparing the performance of the developed steerable needle to commercially available non-steered needles we hope to show the possible performance benefit of the developed needle.

The steerable needle has shown to perform, at minimum, non-inferiorly to a commercially available non-steerable needle. A small cost-effectiveness analysis has shown the possibility of the developed system to be cost-effective. While the developed steerable needle allows a surgeon to steer a needle during needle implantation and possibly increase the needle endpoint accuracy, the question remains whether this will result in a more favourable outcome of the high dose-rate brachytherapy procedure.

The Design of an Anthropomorphic Brain Phantom

Containing Ventricles

Master thesis (2019) - M.L.I. Dik, J.J. van den Dobbelsteen, B.H.W. Hendriks, M. de Vries, Nazli Sarkalkan

Brain, outside the body, will decay quickly, causing ex vivo studies to be difficult. Having a phantom model has a great beneficial value for numerous reasons. Phantoms are, among others, used in research centres, to validate new equipment, to develop biomechanical models or to t ...

Brain, outside the body, will decay quickly, causing ex vivo studies to be difficult. Having a phantom model has a great beneficial value for numerous reasons. Phantoms are, among others, used in research centres, to validate new equipment, to develop biomechanical models or to test new treatment methods. They are representations of organs or tissues made from tissues that mimicking the desired properties of the organ. This thesis research is performed in collaboration with Philips Healthcare research department. They benefit from having a brain phantom for the development of a new endoscopic tool that incorporates virtual reality images in the view. Existing phantoms are usually expensive and are not meant for destruction by needle interventions or endoscopic interventions, or are a very rough representation of reality. For this study, it was the aim to develop an anthropomorphic brain phantom containing the hollow space of the ventricles of the brain, with the correct mechanical and optical characteristics. From a digital 3D mesh brain, moulds were made to assess different ways to produce a brain phantom with ventricles. From literature, the tissue mimicking material (TMM) PVA was selected to use for the production of the phantom. After evaluation of the different approaches to fabricate a phantom, it was decided to produce the hollow spaces of the ventricles by using 3D printed soluble PVA, to be removed out of the model after casting. This was done by 3D printing a brain mould in which a 3D printed PVA ventricle could be inserted. A solution of 6% PVA as tissue mimicking material was used. After the mould and production principle of the model was finalized, the imaging part was assessed. In order for the phantom to be used in CT imaging, barium sulphate was added to the PVA solution as a contrast enhancing material. Two phantoms were made with 1% and 2% barium sulphate. Finally, to assess the shape and the quality of the ventricles in the phantom, the phantom was scanned with a CT scan at Philips Healthcare in Best, the Netherlands. The CT files were evaluated using RadiAnt and 3D slicer to assess the ventricular shape and position. 3D slicer was also used to segment the ventricle shape out of the designed models to compare with the originally developed ventricle structure. This study functions as a proof of concept for the development of a PVA brain phantom containing ventricles produced with 3D printed soluble PVA. All in all, the overall evaluation of the prototypes have shown to be promising models for the development of a brain phantom using PVA and ‘homemade’ fabrication techniques. The use of 3D printed soluble PVA is a novelty in this field of application. It makes the design easy to develop and easily adjusted to patient-specific cases as personalized models can be made.

M. de Vries

Authored

Therapeutic prostate cancer interventions

A systematic review on pubic arch interference and needle positioning errors

Dosimetric benefits and preclinical performance of steerable needles in HDR prostate brachytherapy

Steerable needles in prostate brachytherapy

From sketch to MDR-compliant batch

MR-guided HDR prostate brachytherapy with teleoperated steerable needles

Axially rigid steerable needle with compliant active tip control

Dedicated holmium microsphere administration device for MRI-guided interstitial brain microbrachytherapy

Contributed