Adaptive Control Systems for Medical Robots in Neurosurgery: A Review

According to Avgousti et al. [1], medical surgery has advanced in various aspects of innovation and treatment. The technology used during the surgery depends on the type of surgery involved and the complexity of the procedure [2]. Neurosurgery consists of the medicine of the brain and complications associated with brain surgery [3]. However, there are limitations, such as detailed neural structures and various anatomical aspects [1,4]. Medical robots do not work autonomously. 

It should be noted that medical robots were pioneered by neurosurgery. Depending on the interaction between the surgeon and the robot, there are three models of robotic surgery [5]. The three models include a supervisory control system, a telesurgery system, and a shared control system [6]. As stated by Chumnanve, Pillai, and Suthakorn [7], in robotics, an adaptive control system is essential to track the required trajectory in detail. Upon detailed analysis, it is determined that an adaptive control system should be incorporated into medical robots, specifically in robots that assist in neurosurgery. 

Methods 

Various methods are involved in the development and incorporation of an adaptive control system in medical robots. 4-Channel Architecture is used where it includes impedances, exogenous forces, and forces involving the operator and its environment [8]. There are various inputs from the slave robot and master robot. Also, their controllers, such as the local force and the local position [9]. The architecture has various aspects that aid in the stability of the medical robot during operation. Before surgery, errors associated with position tracking and force tracking should be considered. The errors should be as minimal as zero [10]. Also, all the signals should be bound during operation. The errors should be found for the controllers to function effectively and for the entire system to be stable and efficient in action [2]. 

Results 

The study involves various parts such as a hard cube, a phantom tissue, and a soft cube. A hard cube is used to control the system while the soft cube is a contact material. In this case, the phantom tissue functions as the environment for the operation of the controllers. A hard cube does not get deformed easily as compared to the soft cube. The tracking of position and force is excellent during contact [9]. There are minimum errors. Therefore, the system performs adequately in a non-linear model. From observation, it is determined that proper tracking of position can be well-achieved in both soft and hard tissue [11]. When free motion is used, adequate position tracking is accomplished. Therefore, the adaptive control system proves stability during operation.

Pathophysiology of the disease 

An instance where medical robots can be applied during surgery is when performing surgery on an Alzheimer’s patient. Alzheimer’s disease is a neural disorder that is an irreversible disorder that progresses spontaneously over time [12]. As suggested by Desai, Agrawal, and Ferreira [13], symptoms associated with Alzheimer’s disease are classified as being cognitive or non-cognitive dysfunctions. Cognitive dysfunction includes symptoms such as memory loss, difficulty in languages, and executive dysfunctions [14]. Non-cognitive include symptoms such as, disturbances in behavior and some psychiatric symptoms, which include hallucinations, agitation, delusion, and depression [15]. The patient's cognitive performance dramatically decreases during the last stages. In the previous stages of such a patient, he or she needs assistance in performing their daily activities. Various hypotheses are used to describe the pathophysiology [16]. The explanations include cholinergic hypothesis and genetic study. 

Biochemistry of the disease 

Alzheimer’s disease is believed to be a disease that involves a protein misfolding. The disease results from the accumulation of a protein referred to as amyloid-beta protein [17]. This protein accumulates in the patient’s brain. It is a byproduct of the precursor protein. The precursor protein takes part in neural development [18]. The protein causing Alzheimer’s is a monomer and is soluble. Also, the disease is known to be a tauopathy; this is because tau protein aggregates abnormally [19]. Tau protein is shown in neurons. The neurons are a stabilizer of the microtubules, found in the cytoskeleton of the brain. The level of neurotransmitters in Alzheimer's patients is significantly reduced (10). However, the FDA has approved a method that involves replenishing the level of neurotransmitters. 

Genetics of the disease 

Over 90% of Alzheimer’s patients seem sporadic. Alzheimer’s disease is believed to onset from 60 years patients to 65 years old patients [20]. Alzheimer’s disease is classified into familial and sporadic, which is also referred to as Late-Onset Alzheimer’s Disease (LOAD). Familial is inherited and not affected by the environment. In LOAD, no gene has been identified as the cause of Alzheimer’s disease [21]. However, some studies suggest that there could be a gene component found in LOAD. Apolipoprotein gene is often associated with sporadic LOAD. Yet, individuals with APOE were found to live before 90 years of age; this shows that there could be a different gene component that is associated with Alzheimer's disease. 

Clinical implication and impaction 

Alzheimer’s disease affects the quality of life of the patient as well as the people who take care of the patient. The health-care facilities that attempt to treat AD patients experience a strain on their resources [22,23]. Funds that would have been used to upgrade the facility’s equipment are transferred for use in AD research. People with Alzheimer’s disease frequently visit the health-care facility for treatment [24]. However, their health deteriorates with time as some of the patients may be involved in accidents. As the burden of caring for the patients' increases, many families prefer to send the patient to nursing homes to lower the psychological weight [25]. Facilities that handle Alzheimer’s disease often experience an increase in the patient population. 

The unanswered questions 

 Even as various research studies are undertaken on Alzheimer's disease, there are many unclear and unanswered questions concerning the condition [26]. For instance, how can Alzheimer’s disease be predicted or diagnosed? Are there genetic factors that contribute to the severity of the disease? Maki [27], in the study, queries if safe and efficient treatment exists for Alzheimer’s disease? Why do highly effective clinical trials not show any positive impact on the treatment of Alzheimer’s disease? How do brain cells loose function once the amyloid protein accumulates in the brain?

Over time, various scientific research studies have been done in an attempt to understand Alzheimer’s disease [28]. Many characteristics are associated with Alzheimer’s disease. Alzheimer’s disease progresses in stages [29]. The steps include Mild Cognitive Impairment, bettering the diagnostic options. AD is believed by some researchers to be associated with some genetic components [30]. However, the causative gene has not been proved since some individuals carrying the gene survive past 90 years old [31]. The ability to discover the cure depends on a detailed view of various processes in the brain. The procedures could be cellular or molecular [32].

In conclusion, the AD treatment can be advanced by surgery. The surgery can be done using a medical robot that incorporates an adaptive control system [11]. The system is detailed can result in a clear trajectory and navigation during surgery [33]. Alzheimer's disease is a neural disorder that presents specific symptoms such as memory loss during the early stages. However, as the disease advances, it offers more severe symptoms such as hallucinations [12,34]. Even though research has been done on the disease, there are many unanswered questions concerning the condition. There should be more detailed research associated with the genetics of Alzheimer’s disease [35]. Also, research should be undertaken on highly effective treatment of the disease; this is because it is not genuinely useful yet approved by the FDA.