Manuel Kramer

Validation of in vivo assessment of facial soft-tissue volume changes and clinical application in midfacial distraction: a technical report.

&NA; The purpose of this study was to validate the assessment of visible volume changes of the facial soft tissue with an optical three‐dimensional sensor and to introduce new parameters for the evaluation of the soft‐tissue shape achieved from three‐dimensional data of selected cases of midfacial distraction. Images of a truncated cone of known volume were assessed repeatedly with an optical three‐dimensional sensor based on phase‐measuring triangulation to calculate the volume. Two cubic centimeters of anesthetic solution was injected into the right malar region of 10 volunteers who gave their informed consent. Three‐dimensional images were assessed before and immediately after the injections for the assessment of the visible volume change. In five patients who underwent midfacial distraction after a high quadrangular Le Fort I osteotomy, three‐dimensional scans were acquired before and 6 and 24 months after the operation. The visible soft‐tissue volume change in the malar‐midfacial area and the mean distance of the accommodation vector that transformed the preoperative into the postoperative surface were calculated. The volume of the truncated cone was 235.26 ± 1.01 cc, revealing a measurement uncertainty of 0.4 percent. The injections of anesthetic solution into the malar area resulted in an average visible volume change of 2.06 ± 0.06 cc. The measurement uncertainty was 3 percent. In the five patients, the average distance of maxillary advancement was 6.7 ± 2.3 mm after 6 months and 5.4 ± 3.0 mm after 2 years. It was accompanied by a mean visible volume increase of 8.92 ± 5.95 cc on the right side and 9.54 ± 4.39 cc on the left side after 6 months and 3.54 ± 3.70 cc and 4.80 ± 3.47 cc, respectively, after 2 years. The mean distance of the accommodation vector was 4.41 ± 1.94 mm on the right side and 4.74 ± 1.32 mm on the left side after 6 months and 1.62 ± 1.96 mm and 2.16 ± 1.52 mm, respectively, after 2 years. The assessment of visible volume changes by optical three‐dimensional images can be carried out with considerable accuracy. The determination of volume changes and accompanying accommodation vectors completes the cephalometric analysis during the follow‐up of patients undergoing midfacial distraction. The new parameters will help to assess normative soft‐tissue data on the basis of three‐dimensional imaging with a view to an improved three‐dimensional prediction of the operative outcome of orthognathic surgery. (Plast. Reconstr. Surg. 112: 367, 2003.)

Carotid computed tomography angiography with automated bone suppression: a comparative study between dual energy and bone subtraction techniques.

Objectives:Computed tomography angiography (CTA) is a well-accepted imaging modality to evaluate the vessels of the head and neck. To improve the assessment of vessels at or within the skull base, different techniques to suppress bone in the final CTA image have been developed. We sought to compare the performance of fully automated bone removal based on dual energy (DE) and image registration (bone subtraction CTA [BSCTA]) for the supraaortic vasculature. Materials and Methods:Twenty-seven patients underwent carotid CTA on a dual source CT system. Two scans were performed, one before and one after contrast agent injection in DE mode (simultaneous acquisition of 80 and 140 kV scans). For each patient, data sets were reconstructed for post processing with DE and BSCTA. Two examiners evaluated overall bone suppression and image quality regarding integrity of the vessel lumen of different vessel segments (n = 19) with a 5-point scale (1 = poor, 5 = excellent), CTA source data served as the reference. Wilcoxon signed rank test was used to determine differences between the techniques. Cohens κ was used to determine interobserver agreement. Results:Both bone suppression techniques could be applied successfully in 25 patients with high overall image quality. Two patients were excluded from the evaluation for technical reasons. Interobserver agreement was excellent (κ = 0.85). Mean score of all vessel segments for overall bone removal was 4.45 ± 0.76 for DE and 4.33 ± 1.02 for BSCTA; DE performed better in the vessel segment of the neck (external carotid artery, common carotid artery, V1 to V3 segment of the vertebral artery, subclavian artery), whereas BSCTA was superior in the cranial vessels (C3–C6 segment of the internal carotid artery, ophthalmic artery). Vessel integrity was superior with BSCTA, the mean score of all vessel segments for overall vessel integrity was 3.97 ± 1.47 for DE and 4.49 ± 0.98 for BSCTA, the subclavian artery was most frequently truncated using DE post processing (mean score: 1.44 ± 1.2). Conclusions:Both techniques provided bone suppression in a fully automated way. DE provided more complete bone suppression in the neck, but at the cost of inferior vessel integrity, especially at the thoracic inlet. BSCTA showed excellent results for vessel integrity and was superior to DE in most of the vessels in or at the skull base.

Determination of facial symmetry in unilateral cleft lip and palate patients from three-dimensional data: technical report and assessment of measurement errors.

Objective To assess measurement errors of a novel technique for the three-dimensional determination of the degree of facial symmetry in patients suffering from unilateral cleft lip and palate malformations. Design Technical report, reliability study. Setting Cleft Lip and Palate Center of the University of Erlangen-Nuremberg, Erlangen, Germany. Patients The three-dimensional facial surface data of five 10-year-old unilateral cleft lip and palate patients were subjected to the analysis. Distances, angles, surface areas, and volumes were assessed twice. Main Outcome Measures Calculations were made for method error, intraclass correlation coefficient, and repeatability of the measurements of distances, angles, surface areas, and volumes. Results The method errors were less than 1 mm for distances and less than 1.5° for angles. The intraclass correlation coefficients showed values greater than .90 for all parameters. The repeatability values were comparable for cleft and noncleft sides. Conclusion The small method errors, high intraclass correlation coefficients, and comparable repeatability values for cleft and noncleft sides reveal that the new technique is appropriate for clinical use.

Contrast-enhanced T1-weighted fluid-attenuated inversion-recovery BLADE magnetic resonance imaging of the brain: an alternative to spin-echo technique for detection of brain lesions in the unsedated pediatric patient?

RATIONALE AND OBJECTIVES We compared contrast-enhanced T1-weighted magnetic resonance (MR) imaging of the brain using different types of data acquisition techniques: periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER, BLADE) imaging versus standard k-space sampling (conventional spin-echo pulse sequence) in the unsedated pediatric patient with focus on artifact reduction, overall image quality, and lesion detectability. MATERIALS AND METHODS Forty-eight pediatric patients (aged 3 months to 18 years) were scanned with a clinical 1.5-T whole body MR scanner. Cross-sectional contrast-enhanced T1-weighted spin-echo sequence was compared to a T1-weighted dark-fluid fluid-attenuated inversion-recovery (FLAIR) BLADE sequence for qualitative and quantitative criteria (image artifacts, image quality, lesion detectability) by two experienced radiologists. Imaging protocols were matched for imaging parameters. Reader agreement was assessed using the exact Bowker test. RESULTS BLADE images showed significantly less pulsation and motion artifacts than the standard T1-weighted spin-echo sequence scan. BLADE images showed statistically significant lower signal-to-noise ratio but higher contrast-to-noise ratios with superior gray-white matter contrast. All lesions were demonstrated on FLAIR BLADE imaging, and one false-positive lesion was visible in spin-echo sequence images. CONCLUSION BLADE MR imaging at 1.5 T is applicable for central nervous system imaging of the unsedated pediatric patient, reduces motion and pulsation artifacts, and minimizes the need for sedation or general anesthesia without loss of relevant diagnostic information.

Cranial Computed Tomography Angiography With Automated Bone Subtraction: A Feasibility Study

Objectives:Computed tomography angiography (CTA) is becoming an increasingly accepted noninvasive alternative to catheter angiography. To display continuous vessel contours without superimposed bone in a similar manner, postprocessing of the CTA data is necessary. Threshold-based techniques often fail in regions of close vessel-bone contact, which frequently requires user interaction to optimize the results. This may be laborious and time consuming. The aim of this study was to assess the feasibility of a fully automated algorithm for bone subtraction in cranial CT angiography. Materials and Methods:Forty-nine patients underwent cranial CT angiography on 64 slice CT systems. Two scans were performed, one before (mask) and one after (CTA) contrast agent administration. Images were processed with commercially available subtraction software. Two examiners rated the success of overall bone removal and image quality of different vessel segments (n = 34) with a 4-point scale (1 = poor; 4 = excellent); original CTA data served as the reference. Results:Subtraction was performed successfully in all cases, overall subtraction quality was high (82% of cases were rated good or excellent). Only 50 of 1666 arterial segments (3%) were rated nondiagnostic. No relevant artificial stenoses of the internal carotid artery (ICA) or vertebral artery along their way through the skull base were detected when comparing CTA source images to bone subtraction computed tomography angiography (BSCTA) images. Conclusions:Automatic subtraction provides diagnostic image quality for 3D visualization of intracranial vessels, free from over projecting bone in a fully automatic way. Aneurysms can be evaluated from all angles, and ICA stenoses at the skull base were easily visualized.

Vascular Mapping of Head and Neck : Computed Tomography Angiography Versus Digital Subtraction Angiography

PURPOSE The aim of the study was to compare multislice computed tomography angiography (MSCTA) to digital subtraction angiography (DSA) for vascular mapping of the head and neck. PATIENTS AND METHODS In 50 patients who were scheduled for microvascular reconstruction of the mandible with osteomyocutaneous flaps, MSCTA was carried out before surgery. DSA served as the method of reference. Selective common carotid angiograms were acquired in 2 projections for both sides of the neck. A 64-slice spiral computed tomography (CT) was carried out with a dual-phase protocol, using the arterial phase images for 3-dimensional CTA reconstruction. Volume rendering was used to visualize MSCTA data. RESULTS No adverse reactions or complications occurred during or after the procedures. All CT angiograms were of diagnostic quality. No statistically significant differences between MSCTA and DSA were found for the detection of branches of the external carotid artery that are relevant host vessels for microsurgery neither in the group of 26 patients who had not had surgical treatment before (P = .687), nor in the group of 24 patients who were affected by either a tumor recurrence or an infected osteoradionecrosis (P = .508). CONCLUSION MSCTA proved to be a reliable alternative to DSA in vascular mapping for planning of microvascular reconstruction of the mandible.

Secondary Reconstruction of Posttraumatic Enophthalmos Prefabricated Implants vs Titanium Mesh

OBJECTIVE To compare individually prefabricated computer-assisted designed/computer-assisted manufactured (CAD/CAM) glass-bioceramic implants with nonpreformed titanium meshes for orbital floor reconstruction in secondary correction of enophthalmos. METHODS In a nonrandomized, comparative, prospective cohort study, 2 groups of 10 patients received secondary correction of enophthalmos with CAD/CAM implants in one group and titanium meshes in the other. Relative enophthalmometry and exophthalmometry data were assessed preoperatively, at the end of the operation, at day 90 postoperatively, and at day 365 postoperatively. RESULTS In both groups, the globe position improved significantly at the end of the operation (P = .005 in both groups). At day 90, there was a significant tendency toward relapse of enophthalmos in both groups (P = .005 in the CAD/CAM group and P = .008 in the titanium mesh group). However, the globe position did not change significantly between postoperative days 90 and 365 in both groups (P = .57 in the CAD/CAM group and P = .35 in the titanium mesh group). CONCLUSIONS Individually prefabricated CAD/CAM glass-bioceramic implants and nonpreformed titanium meshes produce similar results in secondary enophthalmos correction. Because of higher costs, the use of CAD/CAM implants should be confined to selected cases in secondary enophthalmos correction.

Diaphragm Repair with a Novel Cross-Linked Collagen Biomaterial in a Growing Rabbit Model.

Background Neonates with congenital diaphragmatic hernia and large defects often require patch closure. Acellular collagen matrices (ACM) have been suggested as an alternative to synthetic durable patches as they are remodeled by the host or could also be used for tissue engineering purposes. Materials and Methods 2.0x1.0 cm diaphragmatic defects were created in 6-weeks old New-Zealand white rabbits. We compared reconstruction with a purpose-designed cross-linked ACM (Matricel) to 4-layer non-cross-linked small intestinal submucosa (SIS) and a 1-layer synthetic Dual Mesh (Gore-Tex). Unoperated animals or animals undergoing primary closure (4/0 polyglecaprone) served as age-matched controls. 60 (n = 25) resp. 90 (n = 17) days later, animals underwent chest x-ray and obduction for gross examination of explants, scoring of adhesion and inflammatory response. Also, uniaxial tensiometry was done, comparing explants to contralateral native diaphragmatic tissue. Results Overall weight nearly doubled from 1,554±242 g at surgery to 2,837±265 g at obduction (+84%). X-rays did show rare elevation of the left diaphragm (SIS = 1, Gore-Tex = 1, unoperated control = 1), but no herniation of abdominal organs. 56% of SIS and 10% of Matricel patches degraded with visceral bulging in four (SIS = 3, Matricel = 1). Adhesion scores were limited: 0.5 (Matricel) to 1 (SIS, Gore-Tex) to the left lung (p = 0.008) and 2.5 (Gore-Tex), 3 (SIS) and 4 (Matricel) to the liver (p<0.0001). Tensiometry revealed a reduced bursting strength but normal compliance for SIS. Compliance was reduced in Matricel and Gore-Tex (p<0.01). Inflammatory response was characterized by a more polymorphonuclear cell (SIS) resp. macrophage (Matricel) type of infiltrate (p<0.05). Fibrosis was similar for all groups, except there was less mature collagen deposited to Gore-Tex implants (p<0.05). Conclusions Matricel induced a macrophage-dominated inflammatory response, more adhesions, had appropriate strength but a lesser compliance compared to native tissue. The herein investigated ACM is not a viable option for CDH repair.

A Novel Pairwise Comparison-Based Method to Determine Radiation Dose Reduction Potentials of Iterative Reconstruction Algorithms, Exemplified Through Circle of Willis Computed Tomography Angiography.

ObjectivesThe aim of this study was to determine the dose reduction potential of iterative reconstruction (IR) algorithms in computed tomography angiography (CTA) of the circle of Willis using a novel method of evaluating the quality of radiation dose–reduced images. Materials and MethodsThis study relied on ReconCT, a proprietary reconstruction software that allows simulating CT scans acquired with reduced radiation dose based on the raw data of true scans. To evaluate the performance of ReconCT in this regard, a phantom study was performed to compare the image noise of true and simulated scans within simulated vessels of a head phantom. That followed, 10 patients scheduled for CTA of the circle of Willis were scanned according to our institutes standard protocol (100 kV, 145 reference mAs). Subsequently, CTA images of these patients were reconstructed as either a full-dose weighted filtered back projection or with radiation dose reductions down to 10% of the full-dose level and Sinogram-Affirmed Iterative Reconstruction (SAFIRE) with either strength 3 or 5. Images were marked with arrows pointing on vessels of different sizes, and image pairs were presented to observers. Five readers assessed image quality with 2-alternative forced choice comparisons. ResultsIn the phantom study, no significant differences were observed between the noise levels of simulated and true scans in filtered back projection, SAFIRE 3, and SAFIRE 5 reconstructions.The dose reduction potential for patient scans showed a strong dependence on IR strength as well as on the size of the vessel of interest. Thus, the potential radiation dose reductions ranged from 84.4% for the evaluation of great vessels reconstructed with SAFIRE 5 to 40.9% for the evaluation of small vessels reconstructed with SAFIRE 3. ConclusionsThis study provides a novel image quality evaluation method based on 2-alternative forced choice comparisons. In CTA of the circle of Willis, higher IR strengths and greater vessel sizes allowed higher degrees of radiation dose reduction.

Peripheral Intravenous Power Injection of Iodinated Contrast Media: The Impact of Temperature on Maximum Injection Pressures at Different Cannula Sizes

RATIONALE AND OBJECTIVES Modern computed tomographic scanners and examination protocols often require high injection rates of iodinated contrast media (CM). The purpose of this study was to investigate the maximum injection pressures (MIPs) with different CM at different temperatures in the most common intravenous cannula (IVC) sizes. MATERIALS AND METHODS Three IVC sizes, 22, 20, and 18 gauge, were evaluated. All examinations were performed with a pressure-limited (300 psi) power injector. The MIPs of three different CM (Solutrast 300, Imeron 350, and Imeron 400) were measured at room temperature (20 degrees C) and at 37 degrees C using increasing flow rates (1-9 mL/s). The intactness of the IVCs was checked after injection. RESULTS Heating the CM led to reductions in injection pressures (P < .001). Using constant flow rates, the difference in MIP between 20-gauge and 22-gauge IVCs was higher than that between 20-gauge and 18-gauge IVCs. By heating the CM, the manufacturers suggested operating pressure limit was exceeded at higher flow rates, such as with an 18-gauge cannula at 8 mL/s instead of 6 mL/s using warmed iomeprol 400. Even with pressures of up to 159.7 psi, none of the IVCs ruptured. CONCLUSIONS Heating of CM effectively reduces MIPs using power injection in common IVCs. Although the manufacturers suggested MIP was exceeded at higher flow rates, safe CM injection seems to be possible even in small cannulas using power injection. The compilation of the obtained data is meant to serve as guidance for future decisions on parameters of the power injection of iodinated CM.