A magnetic internal mechanism for precise orientation of the camera in wireless endoluminal applications

BACKGROUND AND STUDY AIMS

The use of magnetic fields to control operative devices has been recently described in endoluminal and transluminal surgical applications. The exponential decrease of magnetic field strength with distance has major implications for precision of the remote control. We aimed to assess the feasibility and functionality of a novel wireless miniaturized mechanism, based on magnetic forces, for precise orientation of the camera.

MATERIALS AND METHODS

A remotely controllable endoscopic capsule was developed as proof of concept. Two intracapsular moveable permanent magnets allow fine positioning, and an externally applied magnetic field permits gross movement and stabilization. Performance was assessed in ex vivo and in vivo bench tests, using porcine upper and lower gastrointestinal tracts.

RESULTS

Fine control of capsule navigation and rotation was achieved in all tests with an external magnet held steadily about 15 cm from the capsule. The camera could be rotated in steps of 1.8 degrees . This was confirmed by ex vivo tests; the mechanism could adjust the capsule view at 40 different locations in a gastrointestinal tract phantom model. Full 360 degrees viewing was possible in the gastric cavity, while the maximal steering in the colon was 45 degrees in total. In vivo, a similar performance was verified, where the mechanism was successfully operated every 5 cm for 40 cm in the colon, visually sweeping from side to side of the lumen; 360 degrees views were obtained in the gastric fundus and body, while antrally the luminal walls prevented full rotation.

CONCLUSIONS

We report the feasibility and effectiveness of the combined use of external static magnetic fields and internal actuation to move small permanent intracapsular magnets to achieve wirelessly controllable and precise camera steering. The concept is applicable to capsule endoscopy as to other instrumentation for laparoscopic, endoluminal, or transluminal procedures.

Wireless steering mechanism with magnetic actuation for an endoscopic capsule

This paper illustrates the design, development and testing of a miniature mechanism to be integrated in endoscopic capsules for precise steering capabilities (Magnetic Internal Mechanism, MIM). The mechanism consists of an electromagnetic motor connected to a couple of small permanent magnets and immersed in a static magnetic field produced by an external permanent magnet or a by an electromagnetic coil. The overall steering capsule, integrating the magnetic steering mechanism and the vision system is 15.6 mm in diameter, 48 mm in length, 14.4 g in weight and can be oriented with an accuracy of 0.01 degrees . As regards system scalability, the capsule size could be reduced down to 11 mm in diameter by optimizing some mechanical components. On the other hand, the magnets size cannot be reduced because the magnetic link between internal and external magnets at typical operation distances (about 15 mm) would be weak.

Wireless therapeutic endoscopic capsule: in vivo experiment

BACKGROUND AND STUDY AIM

Capsule endoscopy is becoming well established as a diagnostic technique for the gastrointestinal tract. Nevertheless swallowable capsule devices that can effectively perform surgical and therapeutic interventions have not yet been developed. Such devices would also be a valuable support for natural orifice transluminal endoscopic surgery (NOTES). The objective of this study was to assess the feasibility of using a swallowable wireless capsule to deploy a surgical clip under remote control.

MATERIALS AND METHODS

A wireless endoscopic capsule, diameter 12.8 mm and length 33.5 mm, was developed. The device is equipped with four permanent magnets, thus enabling active external magnetic steering. A nitinol clip is loaded on the topside of the capsule, ready to be released when a control command is issued by an external operator. Repeated ex vivo trials were done to test the full functionality of the therapeutic capsule in terms of efficiency in releasing the clip and reliability of the remote control. An in vivo test was then carried out in a pig: the capsule was inserted transanally and steered by means of an external magnetic arm towards an iatrogenic bleeding lesion. The clip, mounted on the tip of the capsule, was released in response to a remote signal. The procedure was observed by means of a flexible endoscope.

RESULTS

A wireless capsule clip-releasing mechanism was developed and tested. During ex vivo trials, the capsule was inserted into the sigmoid section of a phantom model and steered by means of the external magnet to a specific target, identified by a surgical suture at a distance of 3 cm before the left flexure. The capsule took 3 to 4 minutes to reach the desired location moving under external magnetic guidance, while positioning of the capsule directly on the target took 2 to 3 minutes. Successful in vivo clipping of an iatrogenic bleed by means of a wireless capsule was demonstrated.

CONCLUSIONS

This study reports the first successful in vivo surgical experiment using a wireless endoscopic capsule, paving the way to a new generation of capsule devices able to perform both diagnostic and therapeutic tasks.

Accuracy of multidetector spiral computed tomography in detecting significant coronary stenosis in patient populations with differing pre-test probabilities of disease

AIM

To investigate the clinical impact of multidetector computed tomography (MDCT) in patients with a low versus a high pre-test likelihood of coronary artery disease (CAD).

MATERIALS AND METHODS

A cohort of 120 patients with suspected CAD, scheduled for conventional coronary angiography, underwent MDCT. Using the American Heart Association (AHA)/American College of Cardiology (ACC) guidelines, the population was divided into two groups: patients with a low (group 1) and a high (group 2) likelihood of CAD.

RESULTS

Analysis of all segments showed a high feasibility (92%), and a patient based-model showed excellent sensitivity and negative predictive values (NPV; both 100%) and acceptable specificity and positive predictive values (PPV; 86 and 90%, respectively), with an accuracy of 94%. Using MDCT in patients with lower pre-test likelihoods of CAD, according to the ACC/AHA guidelines, the accuracy remained high (93%); conversely, in patient groups with a high prevalence of CAD, a non-significant reduction in accuracy (85%) occurred using MDCT. Particularly, MDCT can be used effectively to exclude a diagnosis of CAD because of its high sensitivity and NPV (100%), but shows a significant reduction in specificity (58%). This reduction was due to an increase in the false-positive:true-negative ratio because of the higher percentage of calcified plaque (a relative but non-significant increase in false positives), and the high prevalence of CAD (significant reduction in true negatives). No differences were found between MDCT and quantitative coronary angiography (QCA) concerning the number of vessels narrowed.

CONCLUSION

Because of its excellent sensitivity and specificity in patients with a low pre-test likelihood of CAD, MDCT could be helpful in clinical decision-making in this population.

Severe degenerative aortic stenosis: when a senile patient is a candidate for surgery

Senile aortic stenosis is characterized by calcific degeneration of the valve that prevents the full opening of the cusps in systole. The disease may be silent for many years despite the presence of severe flow obstruction and generally is associated with aortic regurgitation and calcification of the coronary arteries. The continuous increase of the aged population with aortic stenosis entails difficult decisions in selecting the candidates for aortic valve replacement in order to optimize the timing for surgery. Although clinical examination is still fundamental for the diagnosis of the disease and the screening of the population, noninvasive assessment by Doppler echocardiography has transformed the management of these patients. The procedure allows better identification of patients who may benefit from valve replacement in particular in the setting of a ''low output/low gradient'' state and permits a follow-up of the progression of the disease in patients who are not yet candidates for surgery. It also allows a decrease in the utilization of invasive hemodynamics becoming a cost benefit tool for the health system. When performed properly, it is relatively time consuming, needs experience but offers major anatomic and hemodynamic data. Under these circumstances, cardiac catheterization is required only in cases when there is discordance between the clinical assessment and cardiac ultrasound evaluation. In this review we summarize the prevalence and significance of the disease in the elderly population and the use of all recent echocardiographic data that may help select the true candidates for surgery.

When should asymptomatic patients with combined severe aortic stenosis and aortic insufficiency undergo valve replacement? A clinical case

Indications to prosthetic aortic valve implantation in patients with aortic stenosis or aortic regurgitation or both stenotic or regurgitant aortic valve, who present without symptoms, are controversial. We present the case of an asymptomatic patient with combined severe aortic stenosis and an equally important insufficiency, undergoing surgery for valve substitution with a bileaflet prosthesis. After surgery he was treated with warfarin according to the doses recommended and underwent follow-up with clinical and echocardiographic exams. Eight months after intervention the patient had an embolic stroke with aphasia and right hemiplegia, despite the therapeutic level of INR. At present, even though he has partly recovered motor function, he reports a noteworthy decline in life quality, because of the persistent speech difficulties. We use this case as the starting point for a discussion of the chance of referring patients affected by aortic valvulopathy to valve substitution, in the absence of symptoms.

Omega-3 polyunsatured fatty acids role in postmyocardial infarction therapy

Largely initiated by studies among Eskimos in the early 1970s, great attention has been given to possible effects of omega-3 polyunsatured fatty acids (PUFA) in cardiovascular diseases. A series of positive effects on pathogenetic mechanisms of cardiovascular disease has been discovered from laboratory studies in cell cultures, animal models and in humans. omega-3 PUFA can reduce platelets and leucocytes activities as well as plasma triglycerides. Moreover they can have antiarrhythmic properties. Nowadays patients who experienced myocardial infarction have decreased risk of total and cardiovascular mortality by treatment with omega-3 PUFA (1 g daily). This effect is present irrespective of high or low fish intake or simultaneous intake of other drugs for secondary prevention of coronary heart disease. Mainly on the basis of GISSI Prevention trial results, dietary supplementation with omega-3 PUFA is now recommended as a new component of secondary prevention after myocardial infarction in national and international guidelines.

Fibroblasts of patients affected by Down's syndrome oversecrete amyloid precursor protein and are hyporesponsive to protein kinase C stimulation

The present study investigates the ability of the pharmacologic activation of protein kinase C (PKC) to modulate amyloid precursor protein (APP) secretion in human skin fibroblasts from patients affected by Down's syndrome (DS). We assessed DS subjects at the Hospital Institute of Sospiro, Cremona, and at the Alzheimer's Disease Unit of the Sacred Heart Hospital in Brescia, and we subdivided them into nondemented (NDS) and demented (DDS) patients. All DS patients were trisomy 21 karyotype. DS fibroblasts had an increased content of APP immunoreactive material as revealed by immunocytochemistry analysis. The basal secretion of soluble APP was higher (+94.6%) in Down's cells with respect to controls. The observation on the fibroblasts prepared from DS is consistent with these patients' possessing an extra copy of the APP gene (mapped on chromosome 21) leading to increased APP expression. Phorbol-12,13-dibutyrate (PdBu, 9 to 150 nM) treatment promoted a dose-dependent increase of secreted APP in the conditioned medium of control fibroblasts. The peak response (+102.2%) was attained using 150 nM PdBu. In Down's fibroblasts, PdBu stimulated APP secretion already maximally at low concentrations (9 nM), but the peak response, due to the higher basal release, was lower on a percentage basis (+16.4%) than in control fibroblasts. The results indicate that in Down's fibroblasts the mechanisms controlling APP release are at least quantitatively altered. In addition, these results suggest caution when using information obtained from Down's patients to model Alzheimer's disease biochemical defects.

[Importance of the determination of fructosamine in monitoring diabetic patients]

Protein glycosylation plays a role in the metabolic control and in the pathogenesis of diabetic complications; indeed it has an important role in the process leading to micro- and macroangiography in diabetes. In an attempt to determine the clinical value of fructosamine assay for monitoring type II diabetic patients, the correlation of fructosamine and HbA1c, glycemia, cholesterol and triglycerides was studied. The results show that fructosamine is a good index for short-term metabolic control of diabetic patients.

[Clinical use of growth hormone and clonidine in growth disorders]

The aim of this study was to investigate the effects of the recombinant human growth hormone and of the alpha-2 adrenergic agonist clonidine in three groups of prepuberal children with growth disorders. Three children with GH-deficiency were treated with 0.5 U kg/week i.m. of recombinant growth hormone; 13 children (7 with constitutional delay of growth and 6 with familiar short stature) were treated with 0.08 mg/m2/die per os of clonidine. The results confirmed the growth promoting effect of GH in GH-deficiency. Clonidine restored GH-secretion in children with constitutional delay, but had a very poor or no effect in familiar short children.