Image-to-patient registration techniques in head surgery.

Frame-based stereotaxy was developed in neurosurgery at the beginning of the last century, evolving from atlas-based stereotaxy to stereotaxy based on the individual patient's image data. This established method is still in use in neurosurgery and radiotherapy. There have since been two main developments based on this concept: frameless stereotaxy and markerless registration. Frameless stereotactic systems ('navigation systems') replaced the cumbersome stereotactic frame by mechanically and later also optically or magnetically tracked instruments. Stereotaxy based on the individual patient's image data introduced the problem of patient-to-image data registration. The development of navigation systems based on frameless stereotaxy has dramatically increased its use in surgical disciplines other than neurosurgery, but image-guided surgery based on fiducial marker registration needs dedicated imaging for registration purposes, in addition to the diagnostic imaging that might have been performed. Markerless registration techniques can overcome the resulting additional cost and effort, and result in more widespread use of image-guided surgery techniques. In this review paper, the developments that led to today's navigation systems are outlined, and the applications and possibilities of these methods in the field of maxillofacial surgery are presented.

Piezosurgery--a new safe technique in cranial osteoplasty?

All surgical interventions on the neurocranium bear the risk of injury of the dura mater and development of a cerebrospinal fluid fistula. Therefore, despite careful preparation, damage to the dura mater cannot always be omitted. Especially after surgery and in patients with increased intracranial pressure (craniosynostoses) there is a high risk of perforating the dura. In this article a new surgical technique for osteotomy (Piezosurgery) that avoids perforation of the dura is presented. Ultrasonic microvibrations allow a selective cut of only mineralized structures without damage to the soft tissue. Even in case of accidental contact the dura remains undamaged. This advantage is also useful for bone splitting, to separate the tabula externa from the tabula interna in situ, without any risk of dura perforation even in case of the very thin bones in an infantile skull. The present work shows the applicability of piezoelectric surgery in high-risk patients after osteotomy, avoiding perforation of the dura mater.

An augmented reality system for image-guided surgery.

The introduced new developed navigation system is a High Intensity Approach Light System for augmented reality in image-guided surgery. The surgeon follows the projected approach lights with his ordinary surgical instruments. Thus, tracked instruments are not necessary with this system.

Image-guided removal of foreign bodies.

Foreign bodies are common in the head and face. We investigated the use of image-guided navigation systems for the removal of foreign bodies in 10 patients between 1998 and 2004. In all cases foreign bodies were retrieved. There were no major complications. Image-guided removal of foreign bodies is safe and valuable.

Second malignant neoplasms after treatment of childhood cancer.

The aim of this study was to determine therapy-related risk factors for the development of second malignant neoplasm (SMN) after childhood cancer. The German Childhood Cancer Registry (GCCR) registers all childhood malignancies since 1980 including SMN. A nested case-control study with 238 SMN cases and 450 controls was conducted. A confirmatory, as well as an explorative, analysis was performed. Radiotherapy showed a small effect on the risk of SMN for doses >or=65 Gy. Regarding the chemotherapeutical agents, we saw increased Odds Ratios (OR) for high doses of cyclophosphamide (CP >8000 mg/m(2) OR=6.3 (95% Confidence Interval (CI): 1.3-30.2)), cisplatinum (DDP >435 mg/m(2) OR=2.8 (95% CI: 1.1-6.7)) and mercaptopurine (MP >5000 mg/m(2) OR=4.5 (95% CI: 1.1-18.9)). Patients jointly receiving high doses of MP (>5000 mg/m(2)) and dexamethasone (DEXA >or=1200 mg/m(2)) had an OR=6.9 (95% CI: 1.2-40.3). Our results could be added to those of other investigations to give indications for modifying future therapeutic strategies for childhood cancer.

Polyamine modulation of mitochondrial calcium transport. I. Stimulatory and inhibitory effects of aliphatic polyamines, aminoglucosides and other polyamine analogues on mitochondrial calcium uptake.

In this study, the regulation of mitochondrial Ca2+ transport by polyamines structurally related to spermine and by analogous polycationic compounds was characterized. Similar to spermine, a number of amino groups containing cationic compounds exerted a dual effect on Ca2+ transport of isolated rat liver mitochondria: a decrease in Ca2+ uptake velocity and an enhancement of Ca2+ accumulation. In contrast to the effects of spermine and other aliphatic polyamines, however, the accumulation-enhancing effect of aminoglucosides, basic polypeptides, and metal-amine complexes turned into an inhibition of Ca2+ accumulation at higher concentrations. Within groups of structurally related compounds, the potency to decrease Ca2+ uptake velocity and to enhance Ca2+ accumulation correlated with the number of cationic charges. The presence of multiple, distributed cationic charges was a necessary, but not sufficient criterion for effects on mitochondrial Ca2+ transport, because cationic polyamines and basic oligopeptides which did not enhance mitochondrial Ca2+ accumulation could be identified. Spermine was not able to antagonize the blocking of Ca2+ uptake by ruthenium red, but rather showed an apparent synergism, which can be explained as a displacement of membrane-bound Ca2+ by spermine. The aminoglucosides, gentamicin and neomycin, but not the inactive polyamine bis(hexamethylene)-triamine, inhibited the binding of spermine to intact mitochondria. Apparently, the binding of spermine, gentamicin, and a number of polyamine analogues to low-affinity binding sites at mitochondria, which have low, but distinct structural requirements and which may correspond to phospholipid headgroups, indirectly influences the activity state of the mitochondrial Ca2+ uniporter. The ability of aminoglucosides to displace spermine from the mitochondria and to inhibit mitochondrial Ca2+ accumulation may contribute to the mitochondrial lesions, which are known to occur early in the course of aminoglucoside-induced nephrotoxicity.

The effects of propofol anesthesia on transcortical electric evoked potentials in the rat.

The effects of halogenated anesthetic agents on somatosensory and motor evoked potentials (MEP) have been documented previously. Intravenous anesthetic propofol has not yet been used during MEP monitoring. This study investigates the effects of propofol on transcortical MEP in rats during bolus, infusion, and recovery conditions. After baseline MEP recordings, animals received a hetastarch bolus, followed by a propofol (10 mg/kg) bolus dose. A propofol infusion (10 mg/kg/h) and a hetastarch infusion were then begun. MEP recordings were obtained after the propofol bolus, during the infusion, and after a 30-minute recovery phase. Blood pressure readings remained stable. MEP onset latency increased, and amplitude decreased. Response duration diminished. All values returned towards the baseline during recovery. Our results show that the effects of propofol on MEPs are similar to its effects on somatosensory evoked potentials. Propofol seems to be a reasonable agent for use during intraoperative MEP monitoring and should be further investigated for use during spinal cord monitoring in humans.

Naloxone: report of a beneficial side effect.

We report two cases. The first was an unexpected, complete resolution of an acute unilateral neurologic deficit associated with anesthesia when naloxone was administered to reverse residual narcotic effect. The second was a complete resolution of postoperative unilateral electroencephalographic evidence of ischemia after naloxone administration in a patient following a carotid endarterectomy. A literature search suggests that naloxone may be useful in the treatment of acute and hyperacute stroke due to ischemia.

Anesthesia in 'stone man': myositis ossificans progressiva.

Myositis ossificans progressiva is a rare disease leading to complete ossification of the muscular system. Very little information about this rare disease and its anesthetic implications has appeared in anesthetic literature. This disease is felt to have an autosomal dominant pattern of inheritance and is usually associated with anomalies of the hands and feet. Afflicted patients are frequently misdiagnosed in childhood as having a rheumatologic disorder. Later in life (as true bone is formed in striated muscle, ligaments, and fascia), the correct diagnosis becomes obvious. Although muscles of the heart, diaphragm, larynx, and sphincters are spared, those of the chest wall are not, and pulmonary function progressively deteriorates. Death frequently occurs as a result of a pulmonary infection. Specific anesthetic considerations include positioning to avoid injury, potential need for fiberoptic intubation or tracheostomy, decreased thoracic compliance with the need for increased ventilating pressures, and the ultimate in disuse atrophy contraindicating the use of succinylcholine. Myositis ossificans progressiva can present the anesthesiologist with interesting challenges. Anesthetic management will need to be individualized according to the severity of the disease.

Intraoperative computed tomography and automated registration for image-guided cranial surgery.

OBJECTIVES: Two key problems for the use of navigation systems in image-guided surgery are accurate patient-to-image registration and the fact that with ongoing surgery the patient's anatomy is altered while the image data remains unchanged. A system for intraoperative CT imaging and fully automated registration of this image addresses both problems. It had been evaluated successfully in phantom studies. In this clinical study, we assessed the impact of the system on intraoperative workflow and registration accuracy in everyday patient care. METHODS: In ten patients who underwent image-guided surgery, CT image data were acquired intraoperatively and were automatically registered in the navigation system. Registration accuracy and surgical outcome were assessed clinically. In six of these patients, a maxillary splint with markers had been inserted to cross-check registration accuracy. The target registration error of these markers was measured. RESULTS: In all cases, registration accuracy was clinically sufficient and the surgical task could be performed successfully. In those cases where a maxillary template with target markers was attached for additional control of the registration accuracy, the target registration error was always better than 2 mm. Automated registration reduced the intraoperative registration time considerably and partially compensated for the time needed to perform the image data acquisition. CONCLUSIONS: Intraoperative CT imaging and automated registration successfully address the two key problems of image-guided surgery. The method is robust and accurate and proved its usability in everyday patient care.

Geometric accuracy of digital volume tomography and conventional computed tomography.

Digital volume tomography is a recently established imaging method that is based on the principle of cone beam computed tomography (CBCT). One of its main applications is imaging in dental and maxillofacial surgery. The objective of this study was to compare the geometric accuracy of digital volume tomographic imaging with that of conventional CT and to assess the suitability for image-guided operating. A calibration cube with a defined pattern of tubes inside was scanned using CT and digital volume tomography. Spatial accuracy was analysed with a software evaluation tool. The positions of the intersections of the tubes were detected in imaging data and registered to the real positions in the calibration body. The deviation was calculated and compared for CT and digital volume tomography. Resolution of spatial images was similar for both methods. However, the spatial accuracy in digital volume tomography was slightly lower than that of CT but still in the submillimetric range. The accuracy was better in the middle, but lower in the margins of the volume. This is a disadvantage in technical image quality, but does not affect the diagnostic image quality. The geometric accuracy is sufficient for digital volume tomography-based image-guided surgery.

Automated registration of intraoperative CT image data for navigated skull base surgery.

OBJECTIVES: With a new intraoperative computed tomography (CT) imaging system, patient-to-image registration without any invasive registration markers is possible. Furthermore, registration can be performed fully automatically. The accuracy of this method for skull base surgery was investigated in this study. METHODS: We employed a phantom study design. A phantom skull was equipped with 33 target markers in the regions of the anterior and lateral skull base. CT image data were acquired with an intraoperative CT suite. Image data were transferred as DICOM data to the navigation system, and registration was performed automatically. For registration, the position of the patient and the position of the CT gantry were monitored in the imaging process, using the infrared camera of a navigation system. Using the pointing device of the navigation system, the target markers were identified. The accuracy was measured as the spatial difference of the target markers in image space and on the phantom. RESULTS: Accuracy was always sufficient for image-guided surgery of any region of the skull base, with an average target registration error of below 1.2 mm. In contrast to traditional non-invasive registration methods, there was no difference in registration accuracy between the anterior skull base and the lateral skull base. CONCLUSIONS: Fully automated registration based on a tracked CT gantry is a robust and accurate registration method for skull base surgery.

Ultrasound guided lithotripsy of salivary calculi using an electromagnetic lithotriptor.

Sialolithiasis is a common disease of the major salivary glands. A supplement to the traditional therapies is extracorporeal shock wave lithotripsy of the calculus. This method has been adopted from the therapy of renal or bladder calculi. Patients with a solitary calculus of parotid or submandibular gland were treated with a specially designed lithotriptor. In a retrospective study the results of this therapy were analysed. The success rate was far better for parotid gland calculi than for submandibular calculi. We could not find better results than those published in literature with other devices. In our therapeutic concept, sialolithotripsy is the therapy of first choice for single parotid gland calculi. For submandibular gland calculus this method is advisable in selected cases only.

Laser surface registration for lateral skull base surgery.

OBJECTIVE: Logistics in the run-up to computer-assisted lateral skull base intervention can be reduced by markerless registration methods. So far, only the facial skin surface but not the skin surface that was near to the lateral skull base was used for markerless patient registration. The present study was designed to evaluate whether the auricles may serve as an accurate spatial reference for markerless patient registration in image-guided lateral skull base surgery. STUDY DESIGN: In a prospective clinical study, the precision of markerless patient registration was checked by using periauricular evaluation markers and additional distant oral evaluation markers that served as targets for the infrared pointer of a navigation system. Ten patients with cranial tumors, bony malformations, or foreign bodies who were planned for image-guided surgery were selected. Markerless patient registration was performed by laser-scanning with the SSN++ navigation system. RESULTS: Based on the auricle, a high accuracy (mean target detection error tde = 0.9 mm +/- s = 0.3 mm) was achieved in markerless patient registration as long as the auricle was not deformed during CT imaging or during laser scanning. However, the conventional CT acquisition with a head support caused temporary auricular deformations in half of the patients, which made a precise laser-scan registration impossible. CONCLUSIONS: Automated laser registration of the auricle reduces the logistical input in connection with computer-assisted lateral skull base surgery, ensuring the accuracy that has been achieved up to now with marker-based methods. Constantly good results can be achieved if the head support of the computer tomograph has an appropriate opening at the level of the auricles in order to avoid auricular deformations during CT acquisition.

Detection of foreign bodies of the head with digital volume tomography.

OBJECTIVES: Foreign bodies occur as a sequela of trauma or therapeutic interventions. If the risks are not too high, therapy of choice is the removal of the foreign body. This is only possible if the existence of a foreign body is detected and it is localized accurately. METHODS: The suitability of digital volume tomography (DVT) for the detection and localization of foreign bodies was investigated. Samples of various materials that are typically found as foreign bodies in the head and neck region were used. RESULTS: All materials investigated are principally detectable with DVT. Highly radiopaque material was detectable down to small sizes. The detectability of less radiopaque substances like wood and resins was poor when located in soft tissue. CONCLUSION: DVT is an appropriate tool for the detection of radiopaque foreign bodies. However, foreign bodies made of wood and resin, although detectable by DVT, can be missed when located in muscular tissue. The detectability decreases further when the foreign body is located adjacent to a highly radiopaque tissue like bone. This has to be taken into consideration when using DVT for foreign body detection.

[Markerless patient registration. A new technique for image-guided surgery of the lateral base of the skull]. / Markerlose Registrierung der Patientenlage. Ein neues Verfahren zur bildgestützten Chirurgie der lateralen Schädelbasis.

BACKGROUND: Markerless patient registration is a new procedure that may reduce logistical efforts and possibly also the radiation load on the patients prior to a computer-assisted intervention. Congruent surfaces, such as bone surfaces or skin surfaces, represented in a data set and in the surgical site, can be overlapped with the help of surface matching. Hitherto, these techniques were performed by using the periorbital and frontal skin of the face. The present clinical study assessed the usability of the auricle as a skin structure for markerless patient registration in lateral skull base surgery. PATIENTS AND METHODS: The periauricular precision of the navigation system SSN was investigated clinically in ten patients. Radiopaque registration markers in the periauricular region served as a target in order to evaluate the markerless registration method. RESULTS: Exact patient registration failed in five cases due to temporary deformation of the auricle caused by the head support during CT imaging. An excellent patient registration (mean target registration error = 0.9+/-0.2 mm) was found as long as the auricles had not been temporarily deformed during CT imaging. CONCLUSION: Laser-scan registration of the auricle reduces logistics in image-guided lateral skull base surgery. The problem of temporary deformation of the auricle during CT imaging might be solved by an appropriate opening in the head support at the level of the auricles.