Florian Dammann

Computer-assisted surgical treatment of orbitozygomatic fractures.

Orbitozygomatic fractures pertain to the most common injuries in craniofacial trauma patients. Accurate fracture reduction is of high importance for a successful outcome. This pilot study was performed to assess the potential benefit of surgical navigation to aid in orbitozygomatic fracture reduction. A non-comparative series of five consecutive patients with severely displaced orbitozygomatic fractures was treated using the guidance of computed tomography (CT)-based surgical navigation. Using a previously developed software platform, the fracture was reduced virtually by a three-dimensional shifting of the orbitozygomatic complex within the patients preoperative multimodal CT data set. This treatment plan was transferred to a navigation system. Fracture reduction was performed according to the treatment plan using surgical navigation. Intraoperative control of fracture reduction by comparing the real with the virtual bone position using surgical navigation showed up as a helpful tool. Accurate treatment planning and immediate evaluation of craniofacial surgery outcome are the benefits of the new approach demonstrated. A major drawback of the presented approach is a high consumption of human and financial resources. A larger clinical series with long-term follow-up will be needed to determine reproducibility and cost-effectiveness. In addition to bone repositioning, a future application may include simulation of craniofacial osteotomies.

Ossifying fibroma of the ethmoid involving the orbit and the skull base.

c p u w ssifying fibroma is a rare, benign fibroosseus tumor. The average age at diagnosis is 31 years, with a range f 3 to 63 years, and a female-to-male ratio of 1.6:1. It is sually found in the craniofacial bones, with the mandible eing the most common site, accounting for 75% to 89% of ases. Less commonly, the orbit, paranasal sinuses, or axilla have also been involved. Total removal must be erformed to avoid recurrences. We report a case of an ssifying fibroma of the ethmoid with involvement of the rbit, the frontal bone, and the skull base.

Rationelle CT-diagnostik vor Operationen an den Nasennebenhöhlen

ZusammenfassungDie Darstellung der intraoperativ wichtigen Landmarken kann in der Computertomographie (CT) je nach Bildebene unbefriedigend sein. Die Spiral-CT-Technik verspricht durch die Möglichkeit der Rekonstruktion von sekundären Bildebenen diagnostische Vorteile ohne zusätzliche Strahlenbelastung.Ziel dieser Arbeit war es, HNO-Chirurgen und Radiologen unabhängig voneinander die Abbildungsqualität von primären Aufnahmen und sekundären Rekonstruktionen aus Spiral-CT-Datensätzen der Nasennebenhöhlen vergleichen zu lassen, um die diagnostische Wertigkeit zu bestimmen.Bei insgesamt 80 Patienten wurden je eine koronare und eine axiale Spiral-CT der NNH durchgeführt. Aus den axialen Spiral-CT wurden sekundär koronare Rekonstruktionen und entsprechend aus den koronaren Originalaufnahmen sekundär axiale Rekonstruktionen in 2 mm Abstand berechnet.Im Vergleich zu den primären Aufnahmen wiesen die Sekundärrekonstruktionen zwar Konturstufen und eine reduzierte Ortsauflösung auf, die Erkennbarkeit relevanter Befunde war hierdurch jedoch nicht beeinträchtigt. Als Vorteil der sekundär koronaren Rekonstruktionen erwies sich das Fehlen von Zahnmetallartefakten.AbstractMovement or metal artefacts as well as the relatively high radiation exposure of both the axial and the coronal scan are disadvantages of computed tomography. A single spiral CT scan with a secondary reformation replacing the second CT scan might solve these problems.The goal of this project was to compare the diagnostic value of primary spiral CT scans of paranasal sinuses with secondary reformations. These were evaluated by ENT surgeons as well as radiologists.We performed axial and coronal spiral-CTs of paranasal sinuses in 80 patients. The secondary coronal and axial reformations were calculated with 2 mm image sections.Although a reduced resolution was observed in the secondary reformations, this did not compromise the detection of important anatomical features. Image deterioration due to artifacts was significantly reduced.

Computer-aided surgical treatment of bilateral choanal atresia.

Transnasal surgical treatment of congenital choanal atresia is difficult. A limited view to the surgical field often accounts for poor results. An occurrence of a restenosis is frequently observed requiring difficult revision surgery. Severe complications include bleeding, skull base and intracranial injuries as well as orbital injuries. We describe the use of an optical computed tomography data-based navigation system for surgical planning and intraoperative guidance to improve treatment outcome. Computer-assisted planning and computed tomography data-based navigation was used in the case of a 2-year-old infant with a history of Treacher Collins syndrome associated with bilateral choanal atresia. To reduce target registration error, registration markers were fixed to a maxillary dental splint that was inserted intraorally during image data acquisition and patient registration. A combined technique using navigational guidance and nasal and retropalatal endoscopy was used for instrument navigation successfully removing the bony atretic plates. This clinical report demonstrates the feasibility of a combined approach with surgical navigation. A larger clinical series with long-term follow up will be needed to determine the reproducibility and validation of potential benefits.

Adapted techniques for clinical MR imaging of tendons

To determine whether the echo time of magnetic resonance gradient-echo and spin-echo imaging sequences may be important for the occurrence of high signal strength from tendon with pathological alterations, imaging sequences with sufficient spatial resolution and very short echo times were developed for whole-body imagers with standard gradient system. The sequences were applied on the Achilles tendons of five healthy volunteers and seven patients with achillodynia. Some affected regions inside tendon, probably corresponding with tissue with subtle edema in the collagen bundles were only revealed in images recorded with very short echo times TE<5 ms, whereas stronger affections and protons in liquids between the fiber bundles were also shown in images with longer echo times TE>10 ms. Gradient-echo methods allow shorter echo times than spin-echo techniques for a given gradient system of the imager and given spatial resolution. So minimum echo time gradient-echo sequences should be used for sensitive imaging of tendon alterations, because no considerable signal dephasing due to susceptibility effects were found in tendon.

Noise in magnetic resonance imaging: no risk for sensorineural function but increased amplitude variability of otoacoustic emissions.

Objectives Objectives were to perform exact measurements of the noise exposure in a magnetic resonance imager and to investigate the effects of magnetic resonance imaging (MRI) noise on hearing sensitivity, which are still controversial, in a large number of patients.

Ossifying fibroma of the skull: interactive image-guided minimally invasive localization and resection.

Ossifying fibroma is a benign fibro-osseous tumor commonly affecting the craniofacial bones. It is considered to be a locally aggressive and quickly expansible bone lesion. Because of its aggressive nature and high recurrence rate, early detection and complete surgical removal are essential. Usually, these lesions are excised extensively by craniectomy, and bone loss is reconstructed by cranioplasty using acrylic resin or titanium implants. Alternatively, in the management of skull-ossifying fibroma, an image-guided technique using surgical navigation may provide precise information about localization, enabling complete removal, thereby operating with minimal exposure and within narrow resection borders and avoiding significant bone deformity. A 39-year-old male patient with a history of renal cell carcinoma was admitted to our hospital because a radionuclide scintigraphic bone scan revealed increased uptake in a small area located at the left lateral skull bone. The high-resolution computed tomography scan showed that the lesion was located inside the diploe, destroying the inner table of the calvarium. The patient underwent minimally invasive bone lesion removal using an interactive image-guided approach. Complete resection of the neoplastic lesion was achieved. The histopathological examination revealed an ossifying fibroma. The postoperative course was uneventful, and the patient was discharged 3 days after intervention. To date, there has been no evidence of local recurrence. Interactive multimodal planning and intraoperative image guidance offer an interesting approach for biopsy and minimally invasive removal of small ossifying fibroma lesions of the skull, especially in less accessible locations.

A functioning adrenocortical hemangioma

A 60-year-old woman with hypertension (160/90 mm. Hg) who was receiving a &blocker, amiloride and potassium supplement underwent routine abdominal ultrasound, which revealed a spherical mass on the upper pole of the right kidney. Computerized tomography showed a heterogeneous mass 8 cm. in diameter clearly demarcated from the liver and kidney (see figure). The patient had borderline hypokalemia (3.7 mmol.fl., normal 3.6 to 5.5), hypernatremia (146 mmol.fl., normal 132 to 145) and increased urinary potassium excretion (143 mmo1./24 hours, normal 20 to 90). Adrenocortimtropic hormone levels were undetectable and partially suppressed aRer stimulation with corticotropin releasing fador while serum cortisol was elevated without diurnal variation. Urinary deoxycorticosterone levels were markedly elevated, while plasma aldosterone was normal and plasma renin activity was derreased (see table). The patient underwent partial adrenalectomy. Histology demonstrated a cavernous hemangioma with blood filled lacunae, benign endothelial lining and areas with necrosis, hemor-

Preoperative planning of a complete mastoidectomy: semiautomatic segmentation and evaluation

AbstractObjective Preoperative planning of complete mastoidectomy based on postprocessing, interactive processing, and visualization of CT datasets was implemented and tested. The synthesized images are used to define an access path for the operative treatment of diseases at the lateral skull base. Alternatively, the mastoid may be resected to allocate space for implants such as hearing aids. Methods For the preoperative planning of such surgery, accurate segmentation of the mastoid is required. A semiautomatic pipeline for segmentation of the mastoid was developed. The approach requires minimal user interaction, using a method based on generating a fast 3D-oriented primary segmentation, which (if necessary) can be refined interactively, both in 3D- and slice-based manner. Results To verify the usability of the segmentation and visualization tools for surgery planning, an evaluation study was conducted with datasets of 16 operated patients. For each patient, at least on preoperative CT scan of the skull, with focus on the region of the mastoid to be operated, was available. Qualitative and quantitative evaluation of the images was performed, and the results were tabulated. Conclusion Semiautomated mastoid segmentation provides a feasible means for preoperative planning, based on postprocessing analysis and visualization of CT datasets.

Preoperative imaging of chronic sinusitis by multislice computed tomography.

The aim of this study was to evaluate whether multislice CT enables quality improvement and dose reduction in the imaging of the paranasal sinuses, especially when using secondary reconstructions. We compared the imaging quality of direct CT scans and secondary reconstructions of single-slice CT (SSCT) as a criterion standard with multislice CT (MSCT) of the paranasal sinuses in 80 patients suspected of having chronic sinusitis. Coronary secondary reconstructions were calculated from all transversal CT data sets. Coronary reconstructions of transversal MSCT showed a significantly better image quality compared with coronary reconstructions of SSCT. Because of the absence of dental metal artifacts, coronary reconstructions of MSCT were superior even to direct coronary images of SSCT. MSCT offered a superior examination quality compared to SSCT. A halving of radiation dosage can be reached by eliminating one examination plane.