Wolfgang Puelacher

Preoperative autologous blood donation in orthognathic surgery: a follow-up study of 179 patients

Although there have been recent advances in maxillofacial surgery and anaesthetic techniques, blood replacement is still common in orthognathic surgery. 179 patients underwent elective orthognathic surgery and donated autologous blood preoperatively. Standardized questionnaires about the preoperative blood donation were distributed to the patients. Haemoglobin, haematocrit, red blood cells and platelets were measured before blood donation, presurgically and postsurgically, as well as one year after surgery. Nearly all patients (98%) would recommend preoperative autologous blood donation. 97% of the patients saw the benefits of autologous blood donation in avoiding transfusion-transmitted infectious diseases such as acquired immune deficiency syndrome (AIDS) and hepatitis. No serious side-effects have been observed after blood donation. In patients with bimaxillary osteotomies (65% of the predeposited autologous blood units) 41% were in cases having upper jaw osteotomies and only 22% of the preoperatively donated units were retransfused in patients having lower jaw osteotomies. After a postsurgical decrease, the mean haemoglobin and mean haematocrit levels regained the levels determined prior to the donation. Preoperative autologous blood donation of 2 to 3 units (900-1350 ml +/- 10%) of blood is recommended in bimaxillary osteotomies and 1 to 2 units (450-900 ml +/- 10%) of blood for upper jaw osteotomies. In lower jaw surgery, the acute isovolaemic haemodilution should be considered.

Flapless implant surgery in the edentulous jaw based on three fixed intraoral reference points and image‐guided surgical templates: accuracy in human cadavers

OBJECTIVES In edentulous patients, accurate and stable positioning of a surgical template is impeded by the mobile mucosal tissue. The objective was to evaluate the accuracy of flapless computer-assisted template-guided surgery in an edentulous human cadaver specimen using three fixed oral reference points (FRP) for fixation of the registration mouthpiece and the consecutive surgical template. MATERIAL AND METHODS Oral implants were planned on the computed tomography (CT) of an edentulous human cadaver specimen. Surgical templates have been fabricated using a multipurpose navigation system. Both the registration mouthpiece and consecutive surgical template were supported via three FRP. Study implants were inserted through the guide sleeves and the accuracy was evaluated on a post-surgical CT of the cadaver jaws fused with the pre-surgical planning CT. A Matlab script enabled comparison of the planned surgical path with the study implants. RESULTS In five maxillary and three mandibular edentulous human cadaver specimens, a total of 51 implants (35 implants in the maxilla and 16 implants in the mandible) have been placed. The mean+/-standard deviation total error (Euclidean distance)/lateral error (normal deviation) were 1.1+/-0.6/0.7+/-0.5 mm at the implant base and 1.2+/-0.7/0.9+/-0.7 mm at the implant tip. The mean angular error was 2.8+/-2.2 degrees. CONCLUSIONS Flapless surgery based on FRP-supported image-guided surgical templates may provide similar accuracy as reported for tooth-supported surgical templates or surgical navigation.

Ultralow-dose computed tomography imaging for surgery of midfacial and orbital fractures using ASIR and MBIR

The influence of dose reductions on diagnostic quality using a series of high-resolution ultralow-dose computed tomography (CT) scans for computer-assisted planning and surgery including the most recent iterative reconstruction algorithms was evaluated and compared with the fracture detectability of a standard cranial emergency protocol. A human cadaver head including the mandible was artificially prepared with midfacial and orbital fractures and scanned using a 64-multislice CT scanner. The CT dose index volume (CTDIvol) and effective doses were calculated using application software. Noise was evaluated as the standard deviation in Hounsfield units within an identical region of interest in the posterior fossa. Diagnostic quality was assessed by consensus reading of a craniomaxillofacial surgeon and radiologist. Compared with the emergency protocol at CTDIvol 35.3 mGy and effective dose 3.6 mSv, low-dose protocols down to CTDIvol 1.0 mGy and 0.1 mSv (97% dose reduction) may be sufficient for the diagnosis of dislocated craniofacial fractures. Non-dislocated fractures may be detected at CTDIvol 2.6 mGy and 0.3 mSv (93% dose reduction). Adaptive statistical iterative reconstruction (ASIR) 50 and 100 reduced average noise by 30% and 56%, and model-based iterative reconstruction (MBIR) by 93%. However, the detection rate of fractures could not be improved due to smoothing effects.

Computer-Assisted Surgery in the Edentulous Jaw Based on 3 Fixed Intraoral Reference Points

PURPOSE In computer-assisted implantation surgery, the transfer of prosthodontic-guided planning to the operative site is usually based on a registration template. The precise repositioning of the registration template is crucial for high accuracy and is compromised in edentulous jaws. The purpose was to determine the in vitro registration and targeting accuracy for surgical navigation in the edentulous jaw based on 3 fixed intraoral reference points. MATERIALS AND METHODS Edentulous maxilla and mandible cadaver specimens were provided with 3 fixed reference-point screws. A resin template with matrices for the fixed reference-point screws was produced and connected to a Vogele-Bale-Hohner registration mouthpiece and external registration frame with a snap-lock system. Surgical implants were planned on computed tomographic data and the corresponding dental stone casts were drilled under guidance of an optical navigation system. For evaluation of the registration accuracy, fiducial registration error was recorded and application accuracy was evaluated by fusion of postsurgical computed tomographic scans of the drilled dental stone casts with the presurgical planning computed tomogram. RESULTS In 9 maxillas and 5 mandibles, 14 registrations and 104 stone cast drillings were performed. The mean fiducial registration error was 0.49 +/- 0.14 mm (0.37 to 0.9 mm). The mean total error at the tip of the borehole was 0.88 +/- 0.65 mm (0.0 to 4.24 mm). The mean lateral errors were 0.51 +/- 0.49 mm (0.0 to 2.80 mm) at the base and 0.46 +/- 0.34 mm (0.0 to 1.5 mm) at the tip of the borehole, respectively. The mean angular error was 0.83 +/- 0.60 degrees (0.0 to 2.5 degrees ). CONCLUSION Three fixed intraoral reference points successfully support a registration mouthpiece and provide in vitro registration and targeting accuracy that is comparable to tooth-supported registration templates or bone marker registration.

Comparison of the prevalence of human papilloma virus infection in histopathologically confirmed premalignant oral lesions and healthy oral mucosa by brush smear detection

OBJECTIVE The role of human papilloma virus (HPV) infections in oral carcinogenesis is an important topic of research in maxillofacial oncology. Nevertheless, the association between such infections in the oral cavity and the development of oral precancerous lesions remains unclear. The aim of this study was to evaluate the association between oral HPV infections and oral leukoplakia or erythroplakia. STUDY DESIGN The case control study included 118 patients with manifest oral leukoplakia or erythroplakia, who underwent surgical biopsy, including a histopathologic grading of the lesion, and 100 control patients without any oral lesions. HPV detection was achieved with a noninvasive brush smear method (Digene Cervical Sampler, Hybrid Capture II-Test). Logistic regression analysis was performed to assess the associations. RESULTS A significant association was found between high-risk oral HPV infection and the presence of oral premalignant lesions (P = .001). Among all other evaluated parameters, only smoking showed a significant association with the presence of oral lesions. CONCLUSIONS Oral HPV infections may play a role in the pathogenesis of premalignant oral lesions.

Ultralow-Dose CT of the Craniofacial Bone for Navigated Surgery Using Adaptive Statistical Iterative Reconstruction and Model-Based Iterative Reconstruction: 2D and 3D Image Quality

OBJECTIVE. The purpose of this article is to evaluate 2D and 3D image quality of high-resolution ultralow-dose CT images of the craniofacial bone for navigated surgery using adaptive statistical iterative reconstruction (ASIR) and model-based iterative reconstruction (MBIR) in comparison with standard filtered backprojection (FBP). MATERIALS AND METHODS. A formalin-fixed human cadaver head was scanned using a clinical reference protocol at a CT dose index volume of 30.48 mGy and a series of five ultralow-dose protocols at 3.48, 2.19, 0.82, 0.44, and 0.22 mGy using FBP and ASIR at 50% (ASIR-50), ASIR at 100% (ASIR-100), and MBIR. Blinded 2D axial and 3D volume-rendered images were compared with each other by three readers using top-down scoring. Scores were analyzed per protocol or dose and reconstruction. All images were compared with the FBP reference at 30.48 mGy. A nonparametric Mann-Whitney U test was used. Statistical significance was set at p < 0.05. RESULTS. For 2D images, the FBP reference at 30.48 mGy did not statistically significantly differ from ASIR-100 at 3.48 mGy, ASIR-100 at 2.19 mGy, and MBIR at 0.82 mGy. MBIR at 2.19 and 3.48 mGy scored statistically significantly better than the FBP reference (p = 0.032 and 0.001, respectively). For 3D images, the FBP reference at 30.48 mGy did not statistically significantly differ from all reconstructions at 3.48 mGy; FBP and ASIR-100 at 2.19 mGy; FBP, ASIR-100, and MBIR at 0.82 mGy; MBIR at 0.44 mGy; and MBIR at 0.22 mGy. CONCLUSION. MBIR (2D and 3D) and ASIR-100 (2D) may significantly improve subjective image quality of ultralow-dose images and may allow more than 90% dose reductions.

Multipurpose navigation system-based concept for surgical template production.

PURPOSE We present a concept that uses the multipurpose navigation equipment of a university hospital for computed tomography (CT)-guided surgical template production, to improve the preclinical accuracy of the templates. MATERIALS AND METHODS Oral implants are planned on CT images with respect to the prosthodontic goal and anatomical considerations. Registration is performed via a modified Vogele-Bale-Hohner (VBH) mouthpiece (Medical Intelligence GmbH, Schwabmuenchen, Germany) and an external registration frame. In the laboratory, an optical navigation system is used to transfer the plan to the patients registered dental stone cast for surgical template production. During preclinical evaluation, duplicated stone casts were drilled via the obtained surgical templates. Accuracy was evaluated by matching the preoperative CT to the CT of the drilled stone casts. RESULTS Compared with present registration mouthpieces, the VBH mouthpiece requires only the dental impression of the patients stone cast. In contrast to surgical navigation, an aiming device is used for navigated trajectory-alignment at the best technical level. There is no need for a positioning device, and the template can be immediately fabricated in a standard laboratory. The accuracy of 5 surgical templates showed a maximum normal deviation of 1.4 mm, and maximum angular deviations of 2.8 degrees . CONCLUSION The presented concept allows for successful production of CT-guided surgical templates, and may show sufficient accuracy for clinical use.

Substantial dose reduction in modern multi-slice spiral computed tomography (MSCT)-guided craniofacial and skull base surgery.

PURPOSE Reduction of the radiation exposure involved in image-guided craniofacial and skull base surgery is an important goal. The purpose was to evaluate the influence of low-dose protocols in modern multi-slice spiral computed tomography (MSCT) on target registration errors (TREs). MATERIALS AND METHODS An anthropomorphic skull phantom with target markers at the craniofacial bone and the anterior skull base was scanned in Sensation Open (40-slice), LightSpeed VCT (64-slice) and Definition Flash (128-slice). Identical baseline protocols (BP) at 120  kV/100  mAs were compared to the following low-dose protocols (LD) in care dose/dose modulation: (LD-I) 100  kV/35ref. mAs, (LD-II) 80  kV/40 - 41ref. mAs, and (LD-III) 80  kV/15 - 17ref. mAs. CTDIvol and DLP were obtained. TREs using an optical navigation system were calculated for all scanners and protocols. Results were statistically analyzed in SPSS and compared for significant differences (p ≤ 0.05). RESULTS CTDIvol for the Sensation Open/LightSpeed VCT/Definition Flash showed: (BP) 22.24 /32.48 /14.32 mGy; (LD-I) 4.61 /3.52 /1.62 mGy; (LD-II) 3.15 /2.01 /0.87 mGy; and (LD-III) na/0.76 /0.76 mGy. Differences between the BfS (Bundesamt für Strahlenschutz) reference CTDIvol of 9 mGy and the lowest CTDIvol were approximately 3-fold for Sensation Open, and 12-fold for the LightSpeed VCT and Definition Flash. A total of 33 registrations and 297 TRE measurements were performed. In all MSCT scanners, the TREs did not significantly differ between the low-dose and the baseline protocols. CONCLUSION Low-dose protocols in modern MSCT provided substantial dose reductions without significant influence on TRE and should be strongly considered in image-guided surgery.

Do Image Modality and Registration Method Influence the Accuracy of Craniofacial Navigation

PURPOSE Cone-beam computed tomography (CBCT) is increasingly used in craniofacial imaging and may be an interesting option for navigated surgery. The purpose of this study was to evaluate the accuracy of various registration techniques in CBCT compared with intraoperative and diagnostic multislice spiral computed tomography (MSCT). MATERIALS AND METHODS High-resolution images of an anthropomorphic skull phantom with target markers were obtained using 2 CBCT machines (KaVo 3D eXam, ILUMA), an intraoperative MSCT (Sensation Open), and the standard diagnostic MSCT (LightSpeed VCT). Bone markers, a registration template, and an external registration frame were used for registration with an optical-based navigation system. Target registration errors (TREs) were evaluated and statistically analyzed in SPSS (P < .05). RESULTS The mean ± standard deviation for overall TREs of the KaVo 3D eXam, ILUMA, Sensation Open, and LightSpeed VCT devices were 1.37 ± 0.54, 1.67 ± 0.65, 1.27 ± 0.52, and 1.31 ± 0.30 mm, respectively. The KaVo 3D eXam showed no significant differences compared with the MSCTs. The ILUMA imaged the external registration frame only marginally and showed significant higher TREs compared with the other registration methods (P < .001). In the 2 MSCTs, no significant differences between the registration methods were found. CONCLUSIONS CBCT and intraoperative MSCT may show comparable TREs as standard diagnostic MSCT. Bone markers are the gold standard. Registration templates and external registration frames are valuable alternatives. When using only external registration frames, CBCTs with a large scan field are recommended.

Ultralow dose dentomaxillofacial CT imaging and iterative reconstruction techniques: variability of Hounsfield units and contrast-to-noise ratio.

OBJECTIVE The aim of this study was to evaluate whether application of ultralow dose protocols and iterative reconstruction technology (IRT) influence quantitative Hounsfield units (HUs) and contrast-to-noise ratio (CNR) in dentomaxillofacial CT imaging. METHODS A phantom with inserts of five types of materials was scanned using protocols for (a) a clinical reference for navigated surgery (CT dose index volume 36.58 mGy), (b) low-dose sinus imaging (18.28 mGy) and (c) four ultralow dose imaging (4.14, 2.63, 0.99 and 0.53 mGy). All images were reconstructed using: (i) filtered back projection (FBP); (ii) IRT: adaptive statistical iterative reconstruction-50 (ASIR-50), ASIR-100 and model-based iterative reconstruction (MBIR); and (iii) standard (std) and bone kernel. Mean HU, CNR and average HU error after recalibration were determined. Each combination of protocols was compared using Friedman analysis of variance, followed by Dunns multiple comparison test. RESULTS Pearsons sample correlation coefficients were all >0.99. Ultralow dose protocols using FBP showed errors of up to 273 HU. Std kernels had less HU variability than bone kernels. MBIR reduced the error value for the lowest dose protocol to 138 HU and retained the highest relative CNR. ASIR could not demonstrate significant advantages over FBP. CONCLUSIONS Considering a potential dose reduction as low as 1.5% of a std protocol, ultralow dose protocols and IRT should be further tested for clinical dentomaxillofacial CT imaging. ADVANCES IN KNOWLEDGE HU as a surrogate for bone density may vary significantly in CT ultralow dose imaging. However, use of std kernels and MBIR technology reduce HU error values and may retain the highest CNR.