Using "iDose4" iterative reconstruction algorithm in adults' chest-abdomen-pelvis CT examinations: effect on image quality in relation to patient radiation exposure.

OBJECTIVE: The aim of this study is to examine the effect of iDose4 hybrid iterative reconstruction algorithm (Philips Healthcare, Cleveland, OH) on radiation dose and image quality in chest­abdomen­pelvis (CAP) CT scanning of adult patients. METHODS: CAP CT examinations were performed on 99 patients with the use of the "old standard" protocol performing filtered back projection reconstruction algorithm (FBP protocol) and on 84 patients with the use of iDose4 protocol on a 64-multidetector CT. Patients were subdivided into three weight groups (Group 1, 41­60kg; Group 2, 61­90kg; and Group 3, .90kg). Volume CT dose index and dose length product (DLP) were recorded, while effective dose was calculated from DLP measurements. Objective image noise, signal-to-noise ratio and contrast-to-noise ratio were calculated. Two radiologists reviewed images to evaluate image quality. RESULTS: Compared with the FBP protocol, there was an overall 46.5% significant decrease in effective dose with the use of iDose4 protocol. CONCLUSION: Objective image quality was higher in iDose4 images than in FBP images. Subjective image noise, sharpness, contrast and diagnostic confidence scores tended to be better for iDose4 protocol at the decreased radiation exposure level. Artefacts were minor for both protocols. ADVANCES IN KNOWLEDGE: Our results suggest that the iterative acquisition protocol provides great potential for reducing radiation exposure and maintaining or improving image quality in CAP CT examinations.

[The transverse rectus abdominis muscle (TRAM) flap. A "second defensive line" in microvascular reconstructions of defects in the head and neck area]. / Der transversale Rectus-abdominis-Muskel- (TRAM-)Lappen "Second defensive line" zur mikrovaskulären Rekonstruktion von Defekten im Kopf-Hals-Bereich.

BACKGROUND: The microvascular anastomosed transverse rectus abdominis muscle (TRAM) island flap has been successfully used in plastic surgery for more than 10 years. In reconstructive head and neck surgery, however, it is not yet established. METHOD: We analysed the preparation and anatomical variation in TRAM flaps in an examination of eight cadavers. In a clinical case with complete reconstruction of the nose after nasal ablation and complete loss of a radial lower forearm flap that had been transplanted previously due to a recurrent tumor, the possibility of forming and modeling a TRAM flap is demonstrated. RESULTS: The flap vessels of the TRAM are comparable to the radial forearm flap, and the donor site may be primarily closed. The TRAM proved to be a suitable alternative to close lesions of the head and neck area in selected cases. The myocutaneous TRAM is bulkier than the fascio-cutaneous radial forearm flap. The subcutaneous abdominal fat of the TRAM can be reduced in relation to the vascular distribution of the perforator vessels. If the subcutaneous fat of the flap is reduced, the flap can be shaped and formed well. In the described case, it was used to close the lesion after ablation of the nose and middle face. CONCLUSION: The risk of an iatrogenic lesion of the peritoneal fascia or postsurgical herniation of the abdominal wall is low if several surgical prerequisites are taken into consideration. The myocutaneous TRAM will not replace the fascio-cutaneous radial forearm flap in microvascular head and neck surgery, but the large diameter of the donor vessels and the highly vascularized flap tissue makes it an alternative as a second line procedure in cases of unfavorable wound conditions.

[LED autoregistration in navigated endonasal sinus surgery]. / LED-Autoregistrierung in der navigierten endonasalen Nasennebenhöhlenchirurgie.

BACKGROUND: In endonasal sinus surgery, computer aided surgery (CAS) is a generally accepted method. Applying CAS, there are basic problems with the constancy of accuracy at a free mobile patient head as well as with extended referencing time. The navigation system manufacturer Stryker-Leibinger invented together with our working group a non-invasive, frameless, automatic patient registration and simultaneous tracking system for navigated endonasal sinus surgery. With this new user-friendly system it concerns an active, LED-based, self-adhesive on the surface of splanchnocranium autoregistration mask. MATERIAL AND METHOD: The LED autoregistration mask was tested in an anatomic cadaver study and an ongoing clinical patient study regarding manageability, applicability and accuracy. Accuracy measurements were accomplished on different control points of the head in the cadaver study. The determination of accuracy was calculated with the metric Euclidean distance. Further we report on our experiences with a total of 20 patients applying the new mask. To control the accuracy, anatomic landmarks of the patients were adducted. Goal of our study was to determine the accuracy of the LED mask and to compare it with titanium screw markers, the valid reference gold standard. RESULTS: The LED autoregistration mask convinced by a high precision with relatively simple useability. Total accuracy amounted to 2.22 +/- 0.91 mm. The LED system proved to be a valuable orientation guide mainly at revision surgeries with modified anatomy. CONCLUSIONS: LED surface autoregistration is especially suitable for endonasal sinus surgery and represents a very helpful tool for the rhinosurgeon. Our accuracy studies have shown that the LED autoregistration mask is comparable to the gold standard titanium screw markers and, in addition, very reliable.

[Information assisted surgery as a transdisciplinary surgical procedure]. / Informations-assistierte Chirurgie als ein transdisziplinäres Operationsverfahren.

BACKGROUND: Information assisted surgery (IAS) is a further development of the computer assisted surgery (CAS) exclusively for intraoperative localization serving as basis for future technologies such as mechatronic and robotic. It requires of the surgeon a turnaround from traditional surgical proviso as well as transdisciplinary knowledge in the areas of surgical medicine, radiological imaging and information. The advantage of IAS is the predictability of the surgical procedure according to the specifications of modern quality assessment. METHOD: We analyzed the possibilities for the application of IAS in interdisciplinary transfacial surgery of the frontobasis in 9 patients with different pathologies of the central skull base and the cranio-cervical junction and compared this to conventional CAS. RESULTS: We determined retrospectively with a quality assessment analysis that surgery planning is too time consuming in the moment, and that the necessary transdisciplinary knowledge for IAS cannot be taken for granted yet. IAS has not been consequently applied for the entire surgery process in any of the 9 cases. This was due to technical difficulties as well as large intraoperative accuracy deviations of more than 5 mm. CONCLUSION: Even though the highly-developed technology of IIAS -- intelligent information assisted surgery -- is available, with the possibility of half or fully automatic implementation of IIAS including a automatic re-referencing, this technology will not be used in medical navigation for strategic reasons.

[CAS in rhino-surgical procedures in the growing age]. / CAS bei rhinochirurgischen Operationen im Wachstumsalter.

BACKGROUND: Rhinosurgery in children and adolescents meets special requirements: Limited cooperation and reduced limits for the organ dose for ionizing radiological examinations aggravate diagnostics. On the other side, bone sutures and bone growth areas have to be respected intraoperatively, and regions of bones not yet calcified have to be distinguished from possible tumor infiltration. Computer assisted surgery (CAS) can help to identify these areas safely. METHOD: 5 patients, from the first to the 20 (th) year of life, suffering from tumors, malformation syndromes or therapy resistant nasal polyposis were treated with CAS in rhinosurgery. RESULTS: In addition to radiological diagnostics, we performed 3D computed tomography of the skull for CAS. CAS enabled us to intraoperatively respect possible areas of bone growth, to identify regions with thin, not bonily developed cranial vault and to safely distinguish bone sutures from ethmoidal cells. CAS helped the surgeon to navigate in the not yet developed paranasal sinus system. CONCLUSIONS: CAS is a useful complementary method in rhinosurgery of the developing skull of the child. In spite of the additional 3D computed tomography, the calculated organ dose of the ocular lense amounted to 5 millisievert, so a recommended maximal organ dose for the ocular lense of 15 millisievert was not exceeded.

[Electrophysiologic examinations in low frequency hearing impairment: clinical and prognostic aspects]. / Elektrophysiologische Diagnostik bei Tieftonschwerhörigkeit: Klinische und prognostische Aspekte.

INTRODUCTION: Low-frequency hearing impairment (LFHI) is mainly associated to endolymphatic hydrops and shows a high variety of possible outcomes. Electrophysiologic examinations are widely recommended in diagnostics of LFHI, wheras up to now no data exist about the prognostic value of these examinations in a conservative therapeutic regimen. METHODS: In a quality assessment, we retrospectively evaluated the records of 90 patients, and performed an audiometric follow-up for analysis of long-time hearing data. All patients had undergone diagnostic electrocochleographic examination (ECochG) and then had been treated with rheologic infusions, followed by dehydrating infusions in patients lacking complete remission. The results of both therapeutic strategies and of long-time results were correlated to electrophysiologic findings. RESULTS: The prognosis of LFHI is significantly reflected by pretherapeutic electrocochleographic data. All significant parameters were associated to compound action potential (CAP) whereas parameters associated to cochlear microphonics (CM) did not include any utilizable prognostic value. In patients with a good outcome, the latency of CAP complex was significantly shorter, and the width of CAP complex significantly smaller than in patients with poor hearing outcome after rheologic and after dehydrating therapy and in long time assessment. The relation of summating potential (SP) und CAP was significantly smaller when the outcome was sufficient or good for either therapy and in long time analysis. Steep CAP-input-output-curves were associated to insufficient outcome after rheologic therapy and in long time assessment, but not for dehydrating therapy. CONCLUSIONS: The results indicate that ECochG is of significant prognostic value concerning hearing outcome after conservative therapy in patients suffering from LFHI. It can help the physician to counsel the patient and perform an effective management of the disease. We conclude that ECochG should be performed before the onset of therapy, including collection of SP and CAP data whereas CM parameters may be omitted.

[Does computer-aided navigation of endonasal sinus surgery improve process quality and outcome quality?]. / Verbessert die computergestützte Navigation in der endonasalen Nasennebenhöhlenchirurgie die Prozess- und die Ergebnisqualität?

BACKGROUND: Ever since navigation technology was introduced into endonasal surgery, its impact on process and result of surgery has been debated. In this respect, factors of investment costs and additional costs for time exposure will be discussed as well. PATIENTS AND METHODS: In a retrospective analysis of quality assurance, the results of endonasal surgery by surgeons of different experience in 56 patients were evaluated. Preparation time, preoperative setup time as well as time of actual surgery were analysed and compared with possible indications for navigation. RESULTS: From our analysis a classification resulted dividing the indications for navigation into the following four different categories: redundant, reasonable, helpful, necessary. Navigation was redundant when it was dispensable and did not result in a clear improvement of process or outcome quality. Navigation has been proved reasonable when it helped to obtain additional information for improving process quality. It was considered helpful when the information obtained by navigation had an influence at least on the course and/or result of surgery. Navigation was necessary from the surgeon's point of view when the intervention in regard to the benefit-risk-ratio could not be justified without navigation, or only intraoperative slice imaging would allow surgery. CONCLUSION: Not only redundant, but also facultative and obligatory indications for navigation in endonasal surgery result from careful consideration of the risk-benefit-cost ratio. In standardized endonasal sinus surgery, like infundibulotomy or ethmoidectomy, however, navigation can be a hindrance to process quality and does not result in any advantage for outcome quality.

[Neurophysiologic intraoperative monitoring to preserve cranial nerve function in base of skull surgery]. / Neuromonitoring--Funktionssicherung und -erhalt bei schädelbasischirurgischen Eingriffen?

BACKGROUND: Neurophysiologic intraoperative monitoring (NIM) has gone through a renaissance since the advent of computer technology. Currently, both motor and sensory cranial nerves, including the IInd and VIIIth cranial nerves, can be intraoperatively controlled by means of small and mobile systems. PATIENTS AND METHODS: In order to estimate the value of NIM using the new generation of computer systems, we analyzed the records of 379 patients who underwent skull base surgery since 1996. These comprised NIM of the IInd, VIIth, VIIIth cranial nerves in most cases and of the IXth, Xth, XIth, and XIIth cranial nerves in selected cases. RESULTS: Whereas 72% of these cases demonstrated changes in the recorded intraoperative NIM signals, only 29% of them gave evidence of either clinical or electrophysiological neural function alterations during the postoperative follow-up. CONCLUSIONS: NIM is the only available system capable of providing the surgeon with instant intraoperative neural status-related feedback.

[Navigation-controlled cochleostomy. Is an improvement in the quality of results for cochlear implant surgery possible?]. / Navigiert-kontrollierte Kochleostomie. Ist eine Verbesserung der Ergebnisqualität in der Kochleaimplantatchirurgie möglich?

BACKGROUND: The correct positioning of the electrode, which is the limiting factor for the functional integrity of cochlear implants, is decisively influenced by the cochleostomy. Localisation and form of the drilling canal have been solely defined by the surgeon during the operation and an enlargement of the drilling canal is often necessary. Thanks to the improved resolution of new slice imaging techniques, computed tomography allows an exactly defined optimal point for cochleostomy. MATERIAL AND METHODS: In a cadaver study, we examined whether the target defined with computed tomography can be reached in a reproducible way with the help of navigated computer assisted surgery. We chose titanium screw markers as the gold standard for referencing. RESULTS: There was a real deviation of 1.6 mm in the target field. Thus, in a cochleostomy with a diameter of 0.5 mm the goal was not reached in a reproducible way. With this deviation a target of 2.56 mm(2) is defined. CONCLUSIONS: A target assessed by navigation is better than one reached without navigation in view of reproducibility and accuracy. With further technical progress navigated cochleostomy will be possible.

[Microsurgical resection of jugular foramen tumors with hearing preservation and without facial nerve palsy]. / Resektion von Foramen-jugulare-Tumoren mit vollständigem Hörerhalt. Mikrochirurgie ohne Transposition des N. facialis.

BACKGROUND: The juxtacondylar microsurgical approach is an adequate alternative to the classical infratemporal approach for the resection of tumors of the jugular foramen. PATIENTS AND METHODS: Retrospectively, we report on our experience with eight patients suffering from tumors of the jugular foramen with different etiologies, who were treated successfully via the juxtacondylar approach with interdisciplinary cooperation. RESULTS: The advantage of the juxtacondylar approach is that there is no need to expose and transpose the facial nerve. Additionally, reduction or translocation of the posterior wall of the auditory canal and removal of the ossicular chain are not necessary. CONCLUSIONS: Tumors of the jugular foramen can be safely removed without damaging the facial nerve or auditory capacity, with a comparatively much better overview over the vascular and neural structures of the jugular foramen. This more neurosurgically orientated skull base approach is not very well known in the ENT surgical literature.