Volker Hietschold

Comment on "Developing DCE-CT to Quantify Intra-Tumor Heterogeneity in Breast Tumors With Differing Angiogenic Phenotype

The objective of this study is to evaluate the ability of dynamic contrast enhanced computed tomography (DCE-CT) to assess intratumor physiological heterogeneity in tumors with different angiogenic phenotypes. DCE-CT imaging was performed on athymic nude mice bearing xenograft wild type (MCF-7neo) and VEGF-transfected (MCF-7VEGF) tumors by using a clinical multislice CT, and compared to skeletal muscle. Parametrical maps of tumor physiology-perfusion (F), permeability-surface area (PS), fractional intravascular plasma (fp), and interstitial space ( fis)-were obtained by fitting the time-dependent contrast-enhanced curves to a two-compartmental kinetic model for each voxel (0.3 x 0.3 x 0.75 mm3). Mean physiological measurements were compared with positron emission tomography (PET) imaging, and the spatial distribution of tumor vasculature was compared with histology. No statistically significant difference was found in mean physiological values of F, PS, and fp in MCF-7neo and muscle, while fis of MCF-7neo was a factor of two higher (p<0.04). MCF-7neo tumors also showed a radial heterogeneity with significant higher physiological values in periphery than those in middle and core regions (p<0.01 for all physiological parameters). MCF-7VEGF tumors demonstrated significant increases in all physiological parameters compared with MCF-7neo tumors, and a distinct saccular heterogeneous pattern compared with MCF-7neo and muscle. Both PET imaging and histological results showed good correlation with the above results for this same mouse model. No statistically significant difference was found in the mean perfusion and intravascular volume measured by PET imaging and DCE-CT. Increases in cross-sectional area of blood vessels (p<0.002) were observed in MCF-7VEGF tumors than MCF-7neo, and their spatial distribution correlated well with the spatial distribution of fp obtained by DCE-CT. The results of this study demonstrated the feasibility of DCE-CT in quantification of spatial heterogeneity in tumor physiology in small animal models. Monitoring variations in the tumor environment using DCE-CT offers an in vivo tool for the evaluation and optimization of new therapeutic strategies.The objective of this study is to evaluate the ability of dynamic contrast enhanced computed tomography (DCE-CT) to assess intratumor physiological heterogeneity in tumors with different angiogenic phenotypes. DCE-CT imaging was performed on athymic nude mice bearing xenograft wild type (MCF-7neo) and VEGF-transfected (MCF-7VEGF) tumors by using a clinical multislice CT, and compared to skeletal muscle. Parametrical maps of tumor physiology-perfusion (F), permeability-surface area (PS), fractional intravascular plasma (fp), and interstitial space ( fis)-were obtained by fitting the time-dependent contrast-enhanced curves to a two-compartmental kinetic model for each voxel (0.3 x 0.3 x 0.75 mm3). Mean physiological measurements were compared with positron emission tomography (PET) imaging, and the spatial distribution of tumor vasculature was compared with histology. No statistically significant difference was found in mean physiological values of F, PS, and fp in MCF-7neo and muscle, while fis of MCF-7neo was a factor of two higher (p<0.04). MCF-7neo tumors also showed a radial heterogeneity with significant higher physiological values in periphery than those in middle and core regions (p<0.01 for all physiological parameters). MCF-7VEGF tumors demonstrated significant increases in all physiological parameters compared with MCF-7neo tumors, and a distinct saccular heterogeneous pattern compared with MCF-7neo and muscle. Both PET imaging and histological results showed good correlation with the above results for this same mouse model. No statistically significant difference was found in the mean perfusion and intravascular volume measured by PET imaging and DCE-CT. Increases in cross-sectional area of blood vessels (p<0.002) were observed in MCF-7VEGF tumors than MCF-7neo, and their spatial distribution correlated well with the spatial distribution of fp obtained by DCE-CT. The results of this study demonstrated the feasibility of DCE-CT in quantification of spatial heterogeneity in tumor physiology in small animal models. Monitoring variations in the tumor environment using DCE-CT offers an in vivo tool for the evaluation and optimization of new therapeutic strategies.

Skeletally-anchored Rapid Maxillary Expansion using the Dresden Distractor

Introduction:It was the aim of this study to carry out a 3-D analysis of the teeth, alveolar and skeletal structures during bone-borne, surgically-assisted rapid maxillary expansion (RME) with the Dresden Distractor (DD). We aimed to determine whether a translatory and skeletal movement of the segments would be possible while reducing the dento-alveolar side effects associated with tooth-borne RME.Materials and Methods:Standardized axial computed tomography (CT) was performed on twelve patients averaging 25.3 years of age prior to and after RME with the DD. Reference planes and the triple-0-ELSA were defined bilaterally referring to the following anatomic points: the foramina spinosa, external auditory meati and the anterior margin of the foramen magnum. We measured the amount of movement that occurred before and after RME with the DD against ELSA.Results:A screw activation of 6.0 mm led to a transverse expansion of 5.55 mm in the alveolar process in the premolar region, and of 4.87 mm in the molar region, with 8° to 9.8° of buccal tipping and an increase in width of 6.07 mm and 5.71 mm, respectively, occurred in conjunction with only slight buccal tipping of the premolars (3.1°–4.6°) and molars (1,1°–2.6°). These data signify, beyond the considerable skeletal efficacy, an uprighting of the teeth due to the multibracket appliances torque effect, and a direct transfer of the expansion forces onto the bone. Autorotation of the mandible in forward and upward directions was possible due to the considerably less dental tipping resulting from RME with the DD in comparison to tooth-borne RME. This fact demonstrated that the DD is also well-suited for patients with vertical growth pattern.Conclusion:The bone-borne DD is an effective therapeutic method that spares the patient the negative side effects associated with tooth-borne RME such as root resorption, bone dehis- cence, bite opening and excessive buccal tipping of the teeth. The prerequisites for stable occlusion are brought about by the fact that the expansion is skeletal in nature, with minimal dental tipping.ZusammenfassungZiel:Ziel der Studie war die 3-D-Analyse von Zähnen, alveolären und skelettalen Strukturen bei der knochenverankerten, chirurgisch unterstützten Gaumennahterweiterung (GNE) mit dem Dresden Distraktor (DD). Es sollte überprüft werden, ob eine körperliche und skelettale Bewegung der Segmente mit einer Reduktion der bei der zahngetragenen Gaumennahterweiterung auftretenden dentoalveolären Nebenwirkungen erreicht werden kann.Material und Methodik:Bei zwölf Patienten, Durchschnittsalter 25,3 Jahre, wurden vor und 6,8 Monate nach der GNE mit dem DD standardisierte axiale Computertomogramme (CTs) erstellt. Mittels der anatomischen Referenzpunkte Foramina spinosa und Pori acustici externi beidseits sowie dem Vorderrand des Foramen magnum wurden Referenzebenen und der Tripel-Nullpunkt ELSA definiert. Bewegungen der Messpunkte vor und nach GNE wurden gegen ELSA vermessen.Ergebnisse:Die Schraubenerweiterung von 6,00 mm führte am Alveolarfortsatz in der Prämolarenregion zu 5,55 mm und in der Molarenregion zu 4,87 mm transversaler Erweiterung mit 8°–9,8° Bukkalkippung. Die geringere Bukkalkippung der Prämolaren von 3,1°–4,6° und der Molaren von 1,1°–2,6° bei einer Breitenzunahme von 6,07 mm bzw. 5,71 mm verdeutlichte neben der großen skelettalen Effektivität eine Aufrichtung der Zähne durch den Torqueeffekt der Multibracketapparatur und die direkte Einleitung der Expansionskräfte auf den Knochen. Die im Gegensatz zur zahngetragenen GNE geringe Zahnkippung der GNE mit dem DD erlaubte eine Autorotation der Mandibula nach ventral und kranial, so dass der DD auch bei vertikalem Wachstum gut geeignet war.Schlussfolgerung:Der knochenverankerte DD ist eine effektive Therapiemethode, welche vor unerwünschten Nebenwirkungen zahngetragener GNE wie Wurzelresorptionen, Knochendehiszenzen, Bissöffnung und exzessiver Bukkalkippung der Zähne schützt. Die vorwiegend skelettale Expansion bei geringer Zahnkippung schafft die Voraussetzung für eine stabile Okklusion.

Regional lung aeration and ventilation during pressure support and biphasic positive airway pressure ventilation in experimental lung injury

IntroductionThere is an increasing interest in biphasic positive airway pressure with spontaneous breathing (BIPAP+SBmean), which is a combination of time-cycled controlled breaths at two levels of continuous positive airway pressure (BIPAP+SBcontrolled) and non-assisted spontaneous breathing (BIPAP+SBspont), in the early phase of acute lung injury (ALI). However, pressure support ventilation (PSV) remains the most commonly used mode of assisted ventilation. To date, the effects of BIPAP+SBmean and PSV on regional lung aeration and ventilation during ALI are only poorly defined.MethodsIn 10 anesthetized juvenile pigs, ALI was induced by surfactant depletion. BIPAP+SBmean and PSV were performed in a random sequence (1 h each) at comparable mean airway pressures and minute volumes. Gas exchange, hemodynamics, and inspiratory effort were determined and dynamic computed tomography scans obtained. Aeration and ventilation were calculated in four zones along the ventral-dorsal axis at lung apex, hilum and base.ResultsCompared to PSV, BIPAP+SBmean resulted in: 1) lower mean tidal volume, comparable oxygenation and hemodynamics, and increased PaCO2 and inspiratory effort; 2) less nonaerated areas at end-expiration; 3) decreased tidal hyperaeration and re-aeration; 4) similar distributions of ventilation. During BIPAP+SBmean: i) BIPAP+SBspont had lower tidal volumes and higher rates than BIPAP+SBcontrolled; ii) BIPAP+SBspont and BIPAP+SBcontrolled had similar distributions of ventilation and aeration; iii) BIPAP+SBcontrolled resulted in increased tidal re-aeration and hyperareation, compared to PSV. BIPAP+SBspont showed an opposite pattern.ConclusionsIn this model of ALI, the reduction of tidal re-aeration and hyperaeration during BIPAP+SBmean compared to PSV is not due to decreased nonaerated areas at end-expiration or different distribution of ventilation, but to lower tidal volumes during BIPAP+SBspont. The ratio between spontaneous to controlled breaths seems to play a pivotal role in reducing tidal re-aeration and hyperaeration during BIPAP+SBmean.

Quantitative modifications of TNM staging, clinical staging and therapeutic intent by FDG-PET/CT in patients with non small cell lung cancer scheduled for radiotherapy — A retrospective study

It is obvious that FDG-PET has added value to CT, but there is still insufficient data to define the role of FDG-PET/CT in clinical practice. Usually data are gathered from multiple sources and in consequence the information obtained is heterogeneous and not always comparable between patients. To alleviate this lack of data, we attempted to investigate the differences in staging and therapeutic intent as compared with conventional staging in non small cell lung cancer (NSCLC) patients scheduled for RT after adding FDG-PET/CT to conventional staging in 104 included subjects. In contrary to the multicentric studies relying on patients medical records from outside institutions, these data were generated entirely with the institutions PET/CT unit. Significant modifications of both, M-stage and clinical stage were detected after inclusion of FDG-PET/CT data (p<0.001), while there was no statistically significant T- and N-stage modification. Overall implenting FDG-PET/CT revised RT intention decision in 34% of patients. FDG-PET/CT provides enhanced staging capabilities compared to conventional CT in staging of non small cell lung carcinoma and allows improved selection of patients suitable for curative intention, while avoiding unnecessary irradiation and costs in patients eligible to palliative intention.

Changes in nasal volume after surgically assisted bone-borne rapid maxillary expansion

INTRODUCTION The purposes of this study were to detect, locate, and examine the changes in transverse nasal width, area, and volume from bone-borne, surgically assisted rapid maxillary expansion (SARME) with the Dresden distractor by using computer tomography (CT). METHODS Sixteen patients (average age, 28.7 years) underwent axial CT scanning before and 6 months after SARME. They also underwent CT fusion on specific bony structures. The nasal bone width was examined in the coronal plane. The cross-sectional images of the nasal cavity were taken of the area surrounding the apertura piriformis, the choanae, and in between. We calculated cross-sectional areas and nasal volume according to these data. RESULTS All but 2 patients had an increase in nasal volume of at least 5.1% (SD, 4.6%). The largest value of 35.3% (SD, 45.8%) was measured anteriorly on the nasal floor, decreasing cranially and posteriorly. This correlated with the V-shaped opening of the sutura palatina. There was no significant correlation between increase in nasal volume and transversal expansion. CONCLUSIONS Because most of the air we breathe passes over the lower nasal floor, SARME is likely to improve nasal breathing.

CT Analysis of Nasal Volume Changes after Surgically-assisted Rapid Maxillary Expansion

Objective:Aim of this study was to detect the changes in nasal volume due to bone-borne, surgically-assisted rapid palatal expansion (RPE) with the Dresden Distractor using computed tomography (CT).Materials and Methods:17 patients (mean age 28.8) underwent axial CT scanning before and 6 months after RPE. The nasal bone width was examined in the coronal plane. Cross-sectional images of the nasal cavity were taken of the area surrounding the piriform aperture, choanae and in between. Bony nasal volume was computed by connecting the three cross-sectional areas.Results:All but two patients showed a 4.8% increase in nasal volume (SD 4.6%). The highest value, 33.3% (SD 45.1%), was measured anteriorly at the level of the nasal floor. This correlated with the midpalatal suture’s V-shaped opening. There was no significant correlation between an increase in nasal volume and transverse dental arch expansion.Conclusion:As most of the air we breathe passes the lower nasal floor, an improvement in nasal breathing is likely.ZusammenfassungZiel:Ziel der Studie war die Messung der Vergrößerung des Nasenvolumens nach chirurgisch unterstützter, implantatgestützter forcierter Gaumennahterweiterung (RPE) mit dem Dresden Distraktor (DD) unter Verwendung der Computertomographie (CT).Material und Methodik:17 Patienten mit einem Durchschnittsalter von 28,8 Jahren wurden in die Auswertung der prächirurgischen und postoperativen (6 Monate) CT-Aufnahmen nach RPE einbezogen. Die transversale Expansion wurde in der Koronalebene vermessen. Die Querschnitte wurden auf der Höhe der Apertura piriformis, der Choanen und mittig dazu kalkuliert. Das Volumen wurde durch Verbindung der drei Querschnittsflächen berechnet.Ergebnisse:Alle Patienten mit Ausnahme von zwei zeigten eine Zunahme des Nasenvolumens um durchschnittlich 4,8% (SD 4,6%). Der größte Wert von 33,3% (SD 45,1%) wurde anterior am Nasenboden gemessen. Dies entspricht einer V-förmigen Öffnung der Sutura palatina mediana. Es bestand keine Korrelation zwischen der Zunahme des Nasenvolumens und der transversalen Expansion im Zahnbogen.Schlussfolgerung:Da die größte Menge der Atemluft den Nasenboden passiert und dort die größte Erweiterung zu verzeichnen war, ist mit einer allgemeinen Verbesserung der Nasenatmung bei den meisten Patienten zu rechnen.

Bone density of the midpalatal suture 7 months after surgically assisted rapid palatal expansion in adults

INTRODUCTION The aims of this study were to analyze changes in bone density of the midpalatal suture after surgically assisted rapid palatal expansion (SARPE) with the bone-borne Dresden Distractor (DD; ITU, Dresden, Germany) via computed tomography (CT) and to compare of preoperative surgical findings with a control group. METHODS Sixteen adult patients (mean age 24.5 years) underwent axial CT scans before and 7 months after SARPE. CT image fusion was performed for the midpalatal suture bone. Sixty-six controls (mean age 25.7 years) served for comparing age-related bone density. Bone structure and density were assessed in the coronal plane at the anterior, median, and posterior levels. RESULTS Highest density was found in the posterior part (1046 Hounsfield units [HU]) before expansion. Seven months after SARPE, bone density was 48% (anterior), 53% (median), and 75% (posterior) compared with preoperative values. The control group showed fairly equal Hounsfield units (889 HU to 900 HU) in all parts. CONCLUSIONS Seven months after SARPE, the midpalatal sutures density achieves just one half to three quarters of the pretreatment values. To maintain the resistance against forces from the unsplit posterior part, the retention time should be lengthened.

Dose reduction in computed tomography: the effect of eye and testicle shielding on radiation dose measured in patients with beryllium oxide-based optically stimulated luminescence dosimetry

The aim of this study was to assess the effect of eye and testicle shielding on radiation dose to the lens and the testes of patients undergoing CT examinations. Fifty-one male patients underwent CT twice with identical protocols initially without, the second time with protective garments. Doses to the testes and the lenses were recorded with beryllium oxide-based dosimeters. The dose to the testes and lenses from CT exposure was reduced by 96.2% ± 1.7% and 28.2% ± 18.5%, when testicle and eye shielding was used, respectively. The effect of the eye shielding on the eye lens dose was found to depend on the x-ray tube position when the eye is primarily exposed during the scan. The maximum eye lens dose reduction achieved was found to be 43.2% ± 6.5% corresponding to the anterior position of the tube. A significant correlation between the patient’s body mass index and dose exposure could not be found. Eye and testicle shields, apart from being inexpensive and easy to use, were proven to be effective in reducing eye lens and testicle radiation dose burden from CT exposures.

Frameless intraoperative navigation and referencing in maxillofacial surgery—advances and limitations

Abstract Computer-assisted surgery has found frequent application in oncological and reconstructive surgery of the maxillofacial region. For those indications, important features are a high degree of mobility of the patients head during navigation for a comfortable surgical handling and a high precision of the non-invasive referencing for a good surgical outcome. Common methods of reference-giving, such as applying surface skin markers or using anatomical landmarks, have not been proved accurate enough. Furthermore, a head frame is also inapplicable for complex surgical procedures and its use is reserved for computer-assisted endoscopy. In this study, the accuracy of various types of tooth borne reforming tools was assessed under experimental and clinical condition. Using individually manufactured dental mini-plastic splints and impression trays, we developed different methods for simultaneous dynamic patient tracking and non-invasive reference-giving in an experimental setting and in patients. The acquisition of CT data sets was aided by mini-titanium screws with center drive as fiducial markers, whereas for the magnetic resonance imaging (MRI), oil-containing capsules used as markers proved very useful. Each CT data set was recorded 10 times in the lab. In clinical application landmarks were traced repeatedly. Applying mini-plastic splints marked by titanium screws, we achieved a high accuracy of less than 1.0 mm deviation, which is comparable to that achieved via an invasive approach. The experimentally determined accuracy that includes all potential sources of error (CT-data acquisition, process of reference-giving and dynamic tracking) amounts to 0.68±0.63 mm. The studied system configuration proved to offer a sufficient accuracy for indications in the field of maxillofacial surgery. The method will further profit by improving the stability of the construction and specific adaptation of the program software. However, difficulties in drill and instrument calibration are further sources of error. Limitations arise in edentulous patients where the demanded accuracy can only be achieved by invasively inserted bone markers.

A 31P-magnet resonance spectroscopy study on the metabolism of human masseter in individuals with different vertical facial pattern

OBJECTIVE The objective of this study was to investigate differences in masseter metabolism by (31)P-Chemical Shift Imaging (CSI) in adult individuals with different vertical facial patterns. The clinical study should be supported by functional findings at the mRNA level after orthognathic surgery. STUDY DESIGN Twenty-two male volunteers (mean age 24.6) were divided into a deep-bite (NL/ML 11.8 ± 2.3°) and open-bite group (NL/ML 34.1 ± 2.6°). Vertical jaw relationship, gonial angle, and masseter volume were defined and compared with the phosphate values obtained from the (31)P spectra. Student t test and regression analysis were used. RESULTS Phosphocreatine related strongly to muscle volume (P < .001), gonial angle (P < .001), and ML/NL angle (P < .01). Pi was found to be related to gonial angle (P < .05). Muscle volume was found to be inversely related to ML/NL (P < .01) and to the gonial angle (P < .01). CONCLUSIONS A difference in masseter muscle metabolism between long- and short-faced subjects was confirmed at rest position.