MR-based respiratory and cardiac motion correction for PET imaging.

PURPOSE: To develop a motion correction for Positron-Emission-Tomography (PET) using simultaneously acquired magnetic-resonance (MR) images within 90 s. METHODS: A 90 s MR acquisition allows the generation of a cardiac and respiratory motion model of the body trunk. Thereafter, further diagnostic MR sequences can be recorded during the PET examination without any limitation. To provide full PET scan time coverage, a sensor fusion approach maps external motion signals (respiratory belt, ECG-derived respiration signal) to a complete surrogate signal on which the retrospective data binning is performed. A joint Compressed Sensing reconstruction and motion estimation of the subsampled data provides motion-resolved MR images (respiratory + cardiac). A 1-POINT DIXON method is applied to these MR images to derive a motion-resolved attenuation map. The motion model and the attenuation map are fed to the Customizable and Advanced Software for Tomographic Reconstruction (CASToR) PET reconstruction system in which the motion correction is incorporated. All reconstruction steps are performed online on the scanner via Gadgetron to provide a clinically feasible setup for improved general applicability. The method was evaluated on 36 patients with suspected liver or lung metastasis in terms of lesion quantification (SUVmax, SNR, contrast), delineation (FWHM, slope steepness) and diagnostic confidence level (3-point Likert-scale). RESULTS: A motion correction could be conducted for all patients, however, only in 30 patients moving lesions could be observed. For the examined 134 malignant lesions, an average improvement in lesion quantification of 22%, delineation of 64% and diagnostic confidence level of 23% was achieved. CONCLUSION: The proposed method provides a clinically feasible setup for respiratory and cardiac motion correction of PET data by simultaneous short-term MRI. The acquisition sequence and all reconstruction steps are publicly available to foster multi-center studies and various motion correction scenarios.

Assessment of metastatic colorectal cancer with hybrid imaging: comparison of reading performance using different combinations of anatomical and functional imaging techniques in PET/MRI and PET/CT in a short case series.

PURPOSE: The purpose was to investigate the diagnostic performance of different combinations of anatomical and functional imaging techniques in PET/MRI and PET/CT for the evaluation of metastatic colorectal cancer lesions. METHODS: Image data of 15 colorectal cancer patients (FDG-PET/CT and subsequent FDG-PET/MRI) were retrospectively evaluated by two readers in five reading sessions: MRI (morphology) alone, MRI/diffusion-weighted MRI (DWI), MRI/PET, MRI/DWI/PET; and PET/CT. Diagnostic performance of lesion detection with each combination was assessed in general and organ-based. The reference standard was given by histology and/or follow-up imaging. Separate analysis of mucinous tumours was performed. RESULTS: One hundred and eighty lesions (110 malignant) were evaluated (intestine n = 6, liver n = 37, lymph nodes n = 55, lung n = 4, and peritoneal n = 74). The overall lesion-based diagnostic accuracy was 0.46 for MRI, 0.47 for MRI/DWI, 0.57 for MRI/PET, 0.69 for MRI/DWI/PET and 0.66 for PET/CT. In the organ-based assessment, MRI/DWI/PET showed the highest accuracy for liver metastases (0.74), a comparable accuracy to PET/CT in peritoneal lesions (0.55), and in lymph node metastases (0.84). The accuracy in mucinous tumour lesions was limited in all modalities (MRI/DWI/PET = 0.52). CONCLUSIONS: PET/MRI including DWI is comparable to PET/CT in the evaluation of colorectal cancer metastases, with a markedly higher accuracy when using combined imaging data than the modalities separately. Further improvement is needed in the imaging of peritoneal carcinomatosis and mucinous tumours.

[Multiparametric imaging with simultaneous MRI/PET: Methodological aspects and possible clinical applications]. / Multiparametrische Bildgebung mittels simultaner MR/PET: Methodische Aspekte und klinische Anwendungsmöglichkeiten.

BACKGROUND: Combined MRI/PET enables the acquisition of a variety of imaging parameters during one examination, including anatomical and functional information such as perfusion, diffusion, and metabolism. OBJECTIVE: The present article summarizes these methods and their applications in multiparametric imaging via MRI/PET. RESULTS: Numerous studies have shown that the combination of these parameters can improve diagnostic accuracy for many applications, including the imaging of oncological, neurological, and inflammatory conditions. Because of the amount and the complexity of the acquired multiparametric data, there is a need for advanced analysis tools, such as methods of parameter selection and data classification. DISCUSSION: Currently, the clinical application of this process still has limitations. On the one hand, software for the fast calculation and standardized evaluation of the imaging data acquired is still lacking. On the other hand, there are deficiencies when comparing the results because of a lack of standardization of the assessment and diagnostic procedure.

Automatic delineation of tumor volumes by co-segmentation of combined PET/MR data.

Combined PET/MRI may be highly beneficial for radiotherapy treatment planning in terms of tumor delineation and characterization. To standardize tumor volume delineation, an automatic algorithm for the co-segmentation of head and neck (HN) tumors based on PET/MR data was developed. Ten HN patient datasets acquired in a combined PET/MR system were available for this study. The proposed algorithm uses both the anatomical T2-weighted MR and FDG-PET data. For both imaging modalities tumor probability maps were derived, assigning each voxel a probability of being cancerous based on its signal intensity. A combination of these maps was subsequently segmented using a threshold level set algorithm. To validate the method, tumor delineations from three radiation oncologists were available. Inter-observer variabilities and variabilities between the algorithm and each observer were quantified by means of the Dice similarity index and a distance measure. Inter-observer variabilities and variabilities between observers and algorithm were found to be comparable, suggesting that the proposed algorithm is adequate for PET/MR co-segmentation. Moreover, taking into account combined PET/MR data resulted in more consistent tumor delineations compared to MR information only.

[Whole-body staging of malignant melanoma: advantages, limitations and current importance of PET-CT, whole-body MRI and PET-MRI]. / Ganzkörperdiagnostik beim malignen Melanom: Vorteile, Grenzen und aktueller Stellenwert von PET-CT, GK-MRT und PET-MRT.

Cross-sectional imaging methods are currently the standard methods for staging of advanced melanoma. The former time-consuming and expensive multimodality approach is increasingly being replaced by novel whole-body (WB) staging methods, such as 18F-fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG-PET-CT) and whole-body magnetic resonance imaging (WBMRI) because they offer a complete head-to-toe coverage of the patient in a single examination with an accurate and sensitive detection of tumor spread. Several studies in patients with advanced melanoma revealed that PET-CT is more sensitive and specific than conventional modalities, such as CT alone resulting in a change of management in up to 30 % of cases. Due to the limited sensitivity of PET for lesions smaller than 1 cm, PET-CT is not useful for the initial work-up of patients with stage I and II melanoma but has proven to be superior for detection of distant metastases, which is essential prior to surgical metastasectomy. If PET-CT is not available WB-CT or WB-MRI can alternatively be used and WB-MRI including diffusion-weighted imaging (DWI) has become a real alternative for staging of melanoma patients. So far, however, only few reports suffering from small numbers of cases and heterogeneous design have compared the diagnostic performance of WB-MRI and PET-CT. The preliminary results indicate a high overall diagnostic accuracy of both methods; however, these methods differ in organ-based detection rates: PET-CT was more accurate in N-staging and detection of lung and soft tissue metastases whereas WB-MRI was superior in detecting liver, bone and brain metastases. The value of PET-MRI for staging of advanced melanoma is the subject of ongoing clinical studies.

Assessment of relapse in patients with peritoneal carcinomatosis after cytoreductive surgery and hyperthermic intraperitoneal chemotherapy using F-18-FDG-PET/CT.

PURPOSE: In patients with peritoneal carcinomatosis (PC), cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy (HIPEC) is an evolving therapeutic approach with curative intention. The differentiation between posttherapeutic findings after HIPEC and relapse of PC is challenging. We evaluated the diagnostic value of F-18-FDG-PET/CT in patients with relapse of PC after HIPEC. MATERIALS AND METHODS: 36 patients with recurring PC after HIPEC were examined on a whole-body PET/CT system (44 examinations). The examination included 3 D F-18-FDG-PET and contrast-enhanced CT. Images were assessed by two experienced readers regarding the presence and the extent of PC using the peritoneal carcinomatosis index (PCI). Imaging results were correlated with surgical findings or follow-up. RESULTS: Relapse was suspected in 40 of 44 examinations. Relapse was missed by F-18-FDG PET/CT in 4 patients and significantly underestimated in 8 patients. The diagnostic accuracy for the detection of PC on a patient basis was 91 %, the sensitivity was 91 % and the positive predictive value was 100 %. The mean PCI was 11.4 ±â€Š11.9 for PET/CT, 8.4 ±â€Š10.3 for CT and 16.6 ±â€Š15.0 in the case of surgical exploration. The extent of PC was underestimated by PET/CT and even more by CT alone (p < 0.05). CONCLUSION: The diagnostic value of F-18-FDG PET/CT after cytoreductive surgery and HIPEC in the detection of recurring PC is superior to contrast-enhanced CT. However, the quantification of the extent of PC is limited due to post-therapeutic tissue alterations. KEY POINTS: • Imaging of recurrent PC after HIPEC is challenging due to posttherapeutic tissue alterations.• The extent of recurrent PC after HIPEC is systematically underestimated by F-18-FDG PET/CT.• F-18-FDG PET/CT provides improved sensitivity for recurrent PC compared to contrast-enhanced CT.• The correlation of the extent of recurrent PC depicted by F-18-FDG PET/CT and surgical exploration is better than that of contrast-enhanced CT and surgical exploration.

[Multiparametric imaging with simultaneous MR/PET. Methodological aspects and possible clinical applications]. / Multiparametrische Bildgebung mittels simultaner MR/PET. Methodische Aspekte und Möglichkeiten der klinischen Anwendungen.

Combined magnetic resonance imaging-positron emission tomography (MR/PET) enables acquisition of a variety of imaging parameters during a single examination including anatomical as well as functional information, such as perfusion, diffusion and metabolism. Numerous studies have shown that the combination of these parameters can improve the diagnostic accuracy for many applications especially in oncological imaging. Due to the amount and the complexity of the acquired multiparametric data there is a need for advanced analytical tools, such as methods of parameter selection and data classification. The present article summarizes these methods and their applications in multiparametric imaging via MR/PET.

Staging of neuroendocrine tumours: comparison of [68Ga]DOTATOC multiphase PET/CT and whole-body MRI.

PURPOSE: In patients with a neuroendocrine tumour (NET), the extent of disease strongly influences the outcome and multidisciplinary therapeutic management. Thus, systematic analysis of the diagnostic performance of the existing staging modalities is necessary. The aim of this study was to compare the diagnostic performance of 2 whole-body imaging modalities, [(68)Ga]DOTATOC positron emission tomography (PET)/computed tomography (CT) and magnetic resonance imaging (MRI) in patients with NET with regard to possible impact on treatment decisions. MATERIALS AND METHODS: [(68)Ga]DOTATOC-PET/CT and whole-body magnetic resonance imaging (wbMRI) were performed on 51 patients (25 females, 26 males, mean age 57 years) with histologically proven NET and suspicion of metastatic spread within a mean interval of 2.4 days (range 0-28 days). PET/CT was performed after intravenous administration of 150 MBq [(68)Ga]DOTATOC. The CT protocol comprised multiphase contrast-enhanced imaging. The MRI protocol consisted of standard sequences before and after intravenous contrast administration at 1.5 T. Each modality (PET, CT, PET/CT, wbMRI) was evaluated independently by 2 experienced readers. Consensus decision based on correlation of all imaging data, histologic and surgical findings and clinical follow-up was established as the standard of reference. Lesion-based and patient-based analysis was performed. Detection rates and accuracy were compared using the McNemar test. P values <0.05 were considered significant. The impact of whole-body imaging on the treatment decision was evaluated by the interdisciplinary tumour board of our institution. RESULTS: 593 metastatic lesions were detected in 41 of 51 (80%) patients with NET (lung 54, liver 266, bone 131, lymph node 99, other 43). One hundred and twenty PET-negative lesions were detected by CT or MRI. Of all 593 lesions detected, PET identified 381 (64%) true-positive lesions, CT 482 (81%), PET/CT 545 (92%) and wbMRI 540 (91%). Comparison of lesion-based detection rates between PET/CT and wbMRI revealed significantly higher sensitivity of PET/CT for metastatic lymph nodes (100% vs 73%; P < 0.0001) and pulmonary lesions (100% vs 87%; P = 0.0233), whereas wbMRI had significantly higher detection rates for liver (99% vs 92%; P < 0.0001) and bone lesions (96% vs 82%; P < 0.0001). Of all 593 lesions, 22 were found only in PET, 11 only in CT and 47 only in wbMRI. The patient-based overall assessment of the metastatic status of the patient showed comparable sensitivity of PET/CT and MRI with slightly higher accuracy of PET/CT. Patient-based analysis of metastatic organ involvement revealed significantly higher accuracy of PET/CT for bone and lymph node metastases (100% vs 88%; P = 0.0412 and 98% vs 78%; P = 0.0044) and for the overall comparison (99% vs 89%; P < 0.0001). The imaging results influenced the treatment decision in 30 patients (59%) with comparable information from PET/CT and wbMRI in 30 patients, additional relevant information from PET/CT in 16 patients and from wbMRI in 7 patients. CONCLUSION: PET/CT and wbMRI showed comparable overall lesion-based detection rates for metastatic involvement in NET but significantly differed in organ-based detection rates with superiority of PET/CT for lymph node and pulmonary lesions and of wbMRI for liver and bone metastases. Patient-based analysis revealed superiority of PET/CT for NET staging. Individual treatment strategies benefit from complementary information from PET/CT and MRI.

Correlation of preoperative magnetic resonance imaging of peritoneal carcinomatosis and clinical outcome after peritonectomy and HIPEC after 3 years of follow-up: preliminary results.

PURPOSE: In patients with peritoneal carcinomatosis, cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) is an evolving approach with curative intention. Previous studies indicate a correlation between preoperative magnetic resonance imaging (MRI) and surgical findings regarding the extent of peritoneal carcinomatosis. The aim of this study was to assess retrospectively whether preoperative MRI can predict the outcome and is therefore a suitable tool for patient selection. MATERIALS AND METHODS: Fifteen patients with laparoscopically proven peritoneal carcinomatosis were preoperatively examined using a 1.5-T whole-body MRI system. Results were correlated with surgical exploration. Follow-up was done by contrast-enhanced abdominal computed tomography and, if suspicious for recurring disease, laparoscopy or laparotomy. Survival time and interval to recurring disease were correlated with the preoperative peritoneal carcinomatosis index (PCI) on MRI (Spearman's rank correlation). RESULTS: In five patients radical resection could not be achieved (PCI 34 ± 6.9); survival time was 78.2 ± 54.1 days. In seven patients recurring disease was found 430 ± 261.2 days after initial complete cytoreduction (PCI 11.6 ± 6.9); survival time was 765.9 ± 355 days. Two patients are still alive after 3 years. Two patients with initially complete cytoreduction are without recurring disease after 3 years (PCI 5 and 12). One patient was lost for follow-up. CONCLUSIONS: Results of the preoperative MRI correlate well with the surgical PCI, postoperative resection status, and survival time. MRI might be a suitable technique for patient selection when considering peritonectomy and HIPEC. In our patients the outcome seems to correlate well with the extent of peritoneal carcinomatosis found by the preoperative MRI.

[Application of MR/PET in oncologic imaging]. / Einsatz von MR/PET in der onkologischen Bildgebung.

The present review aims to depict the possibilities offered by hybrid imaging with magnetic resonance positron emission tomography (MR/PET). Recently, new whole-body MR/PET scanners were introduced allowing for the combination of both modalities outside the brain. This is a challenge for both modalities: For MRI, it is essential to provide anatomical images with high resolution. Additionally, diffusion-weighted imaging (DWI), proton spectroscopy, but also dynamic contrast-enhanced imaging plays an important role. With regard to PET, the technical challenge mainly consists of obtaining an appropriate MR-based attenuation correction for the PET data. Using MR/PET, it is possible to acquire morphological and functional data in one examination. In particular, children and young adults will benefit from this new hybrid technique, especially in oncologic imaging with multiple follow-up examinations. However, it is expected that PET/CT will not be replaced completely by MR/PET because PET/CT is less cost-intensive and more widely available. Moreover, in lung imaging, MRI limitations still have to be accepted. Concerning research, simultaneous MR/PET offers a variety of new possibilities, for example cardiac imaging, functional brain studies or the evaluation of new tracers in correlation with specific MR techniques.

Simultaneous PET/MR imaging in a human brain PET/MR system in 50 patients--current state of image quality.

OBJECTIVES: The present work illustrates the current state of image quality and diagnostic accuracy in a new hybrid BrainPET/MR. MATERIALS AND METHODS: 50 patients with intracranial masses, head and upper neck tumors or neurodegenerative diseases were examined with a hybrid BrainPET/MR consisting of a conventional 3T MR system and an MR-compatible PET insert. Directly before PET/MR, all patients underwent a PET/CT examination with either [18F]-FDG, [11C]-methionine or [68Ga]-DOTATOC. In addition to anatomical MR scans, functional sequences were performed including diffusion tensor imaging (DTI), arterial spin labeling (ASL) and proton-spectroscopy. Image quality score of MR imaging was evaluated using a 4-point-scale. PET data quality was assessed by evaluating FDG-uptake and tumor delineation with [11C]-methionine and [68Ga]-DOTATOC. FDG uptake quantification accuracy was evaluated by means of ROI analysis (right and left frontal and temporo-occipital lobes). The asymmetry indices and ratios between frontal and occipital ROIs were compared. RESULTS: In 45/50 patients, PET/MR examination was successful. Visual analysis revealed a diagnostic image quality of anatomical MR imaging (mean quality score T2 FSE: 1.27±0.54; FLAIR: 1.38±0.61). ASL and proton-spectroscopy was possible in all cases. In DTI, dental artifacts lead to one non-diagnostic dataset (mean quality score DTI: 1.32±0.69; ASL: 1.10±0.31). PET datasets of PET/MR and PET/CT offered comparable tumor delineation with [11C]-methionine; additional lesions were found in 2/8 [(68)Ga]-DOTATOC-PET in the PET/MR. Mean asymmetry index revealed a high accordance between PET/MR and PET/CT (1.5±2.2% vs. 0.9±3.6%; mean ratio (frontal/parieto-occipital) 0.93±0.08 vs. 0.96±0.05), respectively. CONCLUSIONS: The hybrid BrainPET/MR allows for molecular, anatomical and functional imaging with uncompromised MR image quality and a high accordance of PET results between PET/MR and PET/CT. These results justify the application of this technique in further clinical studies and may contribute to the transfer into whole-body PET/MR systems.

Whole-body MR/PET: applications in abdominal imaging.

Over the last few decades it has been shown that novel technologies and technological progress rapidly change the working environment of radiologists and nuclear medicine physicians. Thus, new possibilities, e.g., in tumor staging and therapy monitoring, but also new challenges arise. Recently, it could be shown that the integration of magnetic resonance imaging (MRI) and positron emission tomography (PET) is technically possible. The evolvement of new dedicated hybrid MR/PET systems for whole-body imaging in humans offers new potential in multimodal imaging. Especially simultaneous measurement of PET and MRI datasets allows for insights in metabolic and functional processes, particularly in oncologic demands, but also in cardiovascular and cerebral imaging. In this work-in-progress review article, a technical summary including the method-inherent challenges are given. Furthermore, possible clinical applications and research interests are addressed.

[State-of-the-art imaging of peritoneal carcinomatosis]. / State-of-the-Art-Bildgebung bei Peritonealkarzinose.

Imaging studies are essential in the evaluation of patients with suspected or known peritoneal malignancy. Despite major advances in imaging technology in the last few years, the early and adequate detection of a peritoneal dissemination remains challenging because of the great variety in size, morphology and location of the peritoneal lesions. New therapeutic approaches in peritoneal-based neoplasms combining cytoreductive surgery and peritonectomy with hyperthermic intraoperative chemotherapy (HIPEC) suggest improved long-term survival, provided that a complete (macroscopic) cytoreduction is achieved. The preoperative radiological assessment of the extent and distribution of peritoneal involvement plays a vital role in the patient selection process. Despite its known limited accuracy in detecting small peritoneal lesions and the involvement of the small bowel/mesentery, contrast-enhanced MDCT remains the standard imaging modality in the assessment of peritoneal carcinomatosis. MRI, especially with diffusion-weighted images, and FDG-PET/CT are promising methods for the evaluation of peritoneal carcinomatosis with superior results in recent studies, but still have a limited role in selected cases because of high costs and limited availability. Generally, to obtain the most precise readings of peritoneal carcinomatosis, an optimized examination protocol and dedicated radiologists with a deep knowledge of peritoneal pathways and variable morphologies of peritoneal disease are required.

Facial acquisition by dynamic optical tracked laser imaging: a new approach.

Three-dimensional capture of the surface of soft tissue is a desirable support for documentation and therapy planning in plastic and reconstructive surgery concerning the complex anatomy of the face, particularly cleft lip and palate (CLP). Different scanning systems are used for capturing facial surfaces. These systems are mostly based on a static linear measuring arrangement. Established systems work on the basis of coded white light or linear laser triangulation and digital stereophotogrammetric approaches. Shadowing effects occur with these devices. These effects may be avoided by a radical new approach first used in automotive industries that employs a mobile, flexible handheld laser scanner with simultaneous registration by optical tracking. The aim of this study was to assess the suitability of this scanner for surgical procedures on the human face in operating theatre. Five babies aged about 3 months with cleft deformities (one CLP, one bilateral CLP, three isolated cleft lips) were captured directly: twice preoperatively, twice postoperatively and twice after 7 days. An industrial standard specimen and two plaster cast masks of CLP babies were taken and subsequently measured to assess reliability and validity of the device. Masks were measured to reflect the complex surface of the cleft deformity. Data evaluation was done with respect to completeness of the data sets, as well as reliability and validity of the system. Missing data caused by shadowing could be avoided in all images. Even complex areas with undercuts could be reproduced completely and precisely with an accuracy in the sub-millimetre range.

[Positioning of the premaxilla in cases of bilateral cleft lip, alveolus and palate using Latham's appliance]. / Positionierung der Oberkieferelemente mit der Latham-Appartur bei Patienten mit Lippen-Kiefer-Gaumen-Spalten.

UNLABELLED: SUBJECT MATTER: In cases of bilateral cleft lip, alveolus and palate, preoperative positioning of the premaxilla using Latham's appliance has been described. This method is controversial, since it may cause growth defects. PATIENTS AND METHODS: From 1992 to 2000, Latham's appliance was inserted preoperatively into 20 patients with bilateral lip, alveolus and palate clefts with extreme premaxillary protrusion. Pin fixation ensued at the age of 3 months. After adjustment of the premaxilla, the soft palate was closed and bilateral lip adhesion as well as bilateral gingivoperiosteoplasty were performed directly after the removal of the appliance. Final lip closure took place 4-6 weeks later. At the age of 2 years, the hard palate was closed. Evaluation was based on combined face-maxilla models, standard photographs and, when available, lateral skull x-rays showing the relative position of the segments, the influence of Latham's appliance on the nasal septum and the relation of the upper jaw to the skull base and mandibula. RESULTS: In all cases, a satisfactory alveolar alignment was achieved; thickening and curvature of the nasal septum occurred but receded. Neither growth disturbances nor dental germ damage were seen. In two cases, complications arose from suture dehiscence of the lip adhesion: in one patient, a screw defect caused a loosening of the appliance and there was also a transmigration of the postpremaxillary pin. CONCLUSIONS: On the basis of our experience, the use of Latham's appliance, combined with consistent orthodontic supervision and, if necessary, treatment, represents a practical option for the treatment of bilateral cleft lip, alveolus and palate, especially in cases with extreme protrusion of the premaxilla.

[History of the German Society of Oromaxillofacial Surgery]. / Geschichte der Deutschen Gesellschaft für Mund-, Kiefer- und Gesichtschirurgie.

The German Society of Oral and Maxillofacial Surgery was founded by Martin Wassmund in 1951. One of the main reasons was the need for scientific representation in the council at a medical convention. The Society, originally composed of 52 members, was first called "The German Society of Maxillofacial Surgery". In 1972, it extended its title to include the term "oral" ("Mund") and currently comprises 620 members. A scientific conference is held annually on a specific topic. The lectures given there have been published since 1954 in "Fortschritte der Kiefer- und Gesichts-Chirurgie" (Progress in Maxillofacial Surgery) by Thieme Verlag; since 1997, they have appeared as a Springer-Verlag supplement. Topics of choice are published in "Mund-, Kiefer- und Gesichtschirurgie" ("Oral and Maxillofacial Surgery"), originally by Hanser in Munich and now by Springer-Verlag in Heidelberg. In this manner, it was possible to completely document the scientific activities and progress in this specialty. Each year since 1957, a prize named after M. Wassmund, has been given for outstanding scientific accomplishment. The presidents, convention locations, topics, and prizewinners are listed in a table. Since the founding of the Society of Oral and Maxillofacial Surgery, close cooperation has existed with the National Association of German Oral and Maxillary-Facial Surgeons (Bundesverband der Deutschen Arzte für Mund-Kiefer-Gesichts-Chirurgie). In order to intertwine scientific and political interests, a fusion of these two organizations is planned for the year 2000.

Neo-osseous flaps using demineralized allogeneic bone in a rat model.

Surgical reconstruction with revascularized bone grafts can be compromised by donor tissue limitations and may be refined by prefabrication of compound neoflaps using bone substitutes. The principal suitability of demineralized allogeneic bone (DALB) slabs in fabricating neo-osseous flaps based on the inferior epigastric vascular system was studied and compared with neoflaps with autologous bone (AUB). In 45 rats, the histological pattern of bone formation in response to angiogenesis induced by vessel implantation was assessed, and characteristics of vascularization of the neoflap were studied microangiographically at 2, 4, 6, and 8 weeks. Histological techniques included decalcified and nondecalcified sections, as well as intravital polyfluorochrome labeling. Blood flow of the neoflap was also assessed quantitatively using 15-microm microspheres labeled with technetium 99-methylene diphosphate (99-MDP) 8 weeks after flap fabrication. Although the DALB neoflaps showed consistent bone formation and neovascularization, the bone regeneration process was delayed distinctly in comparison with AUB. Microangiographically, however, no differences between the two types of grafts became apparent during all time periods tested. Furthermore, the radioactivity of the DALB neoflap, which means bone blood flow per dry weight, was significantly higher than in AUB grafts and even more than that of intact iliac bone (p = 0.001). The exact meaning of elevated blood flow in DALB and similar degrees of vascularization corresponding to native AUB grafts remains to be determined, but may be a sign of ongoing bone formation resulting in a suitable DALB-containing neo-osseous flap in the long term. The authors findings support that allogeneic bone could be a potential substitute for AUB in creating a prefabricated neo-osseous flap.