Radiochemotherapy-induced changes of tumour vascularity and blood supply estimated by dynamic contrast-enhanced CT and fractal analysis in malignant head and neck tumours.

OBJECTIVE: To investigate radiochemotherapy (RChT)-induced changes of transfer coefficient (K(trans)) and relative tumour blood volume (rTBV) estimated by dynamic contrast-enhanced CT (DCE-CT) and fractal analysis in head and neck tumours (HNTs). METHODS: DCE-CT was performed in 15 patients with inoperable HNTs before RChT, and after 2 and 5 weeks. The dynamics of K(trans) and rTBV as well as lacunarity, slope of log(lacunarity) vs log(box size), and fractal dimension were compared with tumour behaviour during RChT and in the 24-month follow-up. RESULTS: In 11 patients, an increase of K(trans) and/or rTBV after 20 Gy followed by a decrease of both parameters after 50 Gy was noted. Except for one local recurrence, no tumour residue was found during the follow-up. In three patients with partial tumour reduction during RChT, a decrease of K(trans) accompanied by an increase in rTBV between 20 and 50 Gy was detected. In one patient with continuous elevation of both parameters, tumour progressed after RChT. Pre-treatment difference in intratumoral heterogeneity with its decline under RChT for the responders vs non-responders was observed. CONCLUSION: Initial growth of K(trans) and/or rTBV followed by further reduction of both parameters along with the decline of the slope of log(lacunarity) vs log(box size) was associated with positive radiochemotherapeutic response. Increase of K(trans) and/or rTBV under RChT indicated a poor outcome. ADVANCES IN KNOWLEDGE: The modification of K(trans) and rTBV as measured by DCE-CT may be applied for the assessment of tumour sensitivity to chose RChT regimen and, consequently, to reveal clinical impact allowing individualization of RChT strategy in patients with HNT.

Comparison of reference points in different methods of temporomandibular joint imaging.

PURPOSE: Conventional radiography is a well-established method for imaging of the temporomandibular joint (TMJ) structures. However, the dental computer tomography becomes more important for the visualization of teeth in the jaw-bone. The applicability of dental computer tomography for the visualization of the TMJ it not yet been proven. The aim of the study was to identify TMJ structures using reference points with the magnetic resonance imaging (MRI) and the computed tomography (CT). METHODS: In order to compare the visualization and measurement of the TMJ a total of eight human cadaver heads was examined with CT and MRI and analysed using reference points. RESULTS: In both imaging techniques the selected reference points and distances are well definable and allow objective evaluation of anatomical structures. The CT images display a clearly better contrast to noise ratio than the MR images. The distance measurement of different width and length showed significant correlation of both images techniques. CONCLUSIONS: In TMJ diagnostics, maximum information could be obtained using both imaging techniques together due to synergistic effects.

[Computed tomography: influence of varying tube current on patient dose and correctness of effective dose calculations]. / Computertomografie: einfluss des variablen röhrenstroms auf die patientendosis und die genauigkeit von berechnungen der effektiven dosis.

PURPOSE: Determination of the influence of tube currents varying during a CT scan on organ doses and on the effective dose as a function of patient constitution. Evaluation of the accuracy of effective dose calculations based on summarizing parameters (effective mAs, dose length product [DLP]) compared to calculations based on slice-specific tube currents. MATERIALS AND METHODS: Investigation of the CT datasets of 806 patients acquired from the skull base to the proximal thigh with respect to the body mass index (BMI). The effective dose was calculated by means of slice-specific as well as region-specific conversion factors. RESULTS: Dose optimization by means of variable tube current resulted in a reduction of the gonad dose in patients with BMI < or = 20 ... 21 kg/m (2) and of the effective dose in patients with BMI < or = 26 kg/m (2). Effective dose values calculated with the DLP for 90 % of the patients are within an interval of +/- 20 % of the values calculated using slice-specific tube currents. CONCLUSION: If tube current optimization during the CT scan was applied, for the scan region under investigation, at a BMI already below the German mean value, an increased effective dose was observed. Calculations of the effective dose on the basis of summarizing values such as DLP or effective mAs are of sufficient accuracy.

MR-based coronary artery blood velocity measurements in patients without coronary artery disease.

To evaluate the feasibility of MR-based coronary blood velocity measurements (MRvenc) in patients without coronary artery disease (CAD). Eighty-three patients with angiographically excluded CAD received MRvenc of the proximal segments of both coronary arteries (CAs). Using a retrospectively ECG-gated breath-hold phase-contrast FLASH sequence with high temporal resolution, flow data were technically acquirable in 137/166 (83%) CAs. Quantification and analysis of blood velocities in systole and diastole of both CAs were performed. Biphasic velocity profiles were found in 83/100 CAs. Median systolic and diastolic velocities differed significantly in LCA (19 cm/s, 24 cm/s; P<0.0001) and RCAs (14 cm/s, 16 cm/s; P<0.01). The diastolic/systolic velocity ratio was calculated in LCAs and RCAs with a median of 1.3 and 1.1, respectively. The velocity profiles of the remaining CAs were monophasic (17 CAs) or revealed severe alterations of the physiologic velocity profile with reduced flow undulations and steady velocities (37 CAs). Optimized clinical MRvenc is feasible to quantify blood velocities in the CAs. Potential indications are (1) non-invasive monitoring of patients after aortic valve reconstruction as well as (2) detection of asymptomatic CAD patients.

An evaluation of resonance frequency analysis for the determination of the primary stability of orthodontic palatal implants. A study in human cadavers.

BACKGROUND: The primary stability of short orthodontic implants is important for anchorage. METHODS: For this study 14 cadaveric human heads were used. The stability of orthodontic implants (Straumann) with lengths of 4 and 6 mm and different localization (palatal suture or paramedially) were evaluated. The implants with length of 6 mm were only placed in the suture and primary stability was non-invasively determined with the resonance frequency (Osstell). The invasive method for the analysis of the morphometric parameters of the implant/bone contact was carried out by means of histological and radiological examinations. RESULTS: The 6 mm implants have significant better primary stability in the palatal suture as 4 mm implants paramedially (P<0.05). No differences were found between 6 and 4 mm implants in the palatal suture and between 4 mm implants in palatal suture to paramedially. The histological and radiological results demonstrate the ability to measure the implant stability by investigation of the bone offer and density around the implant. Bone structure, especially the pore size in the trabecular bone and the precision of placement may influence the stability. CONCLUSION: This study shows that the short implant gives sufficient bone fixation, independently of placement. The quality of implantation and bone structure are more important than the length of the orthodontic implant.

[Computed tomographic examination of muscle volume, cross-section and density in patients with dysgnathia]. / Computertomographische Untersuchung von Muskelvolumen, -querschnitt und -dichte bei Dysgnathiepatienten.

PURPOSE: The individual jaw position is determined by the masticatory muscle among other factors. Before surgical treatment of malocclusions, thorough evaluation of the muscles is required to estimate the relapse risk. MATERIALS AND METHODS: By means of computer tomography, lateral radiographs of the skull and denture models, the relationships between morphological parameters of the masticatory muscles and the jaw bone were analyzed. Furthermore, possible causes for the extent of the malocclusion are described. RESULTS: A patient group with deep overbite was found to have significantly higher muscle densities (measured in Hounsfield units [HU]) in the medial pterygoideus muscle (59.89 +/- 3.91 HU to 48.94 +/- 4.14 HU, p < 0.01), masseter muscle, and genioglossus muscle (p < 0.05) in comparison to open bite patients. Significant differences of the muscle cross-section were measured in the masseter muscle between patients with retroclined maxillary incisors and with an open bite (5.4 +/- 0.7 cm (2) to 3.8 +/- 0.4 cm (2), p < 0.05). CONCLUSION: The results show a correlation between different jaw positions and masticatory muscles. They also suggest that the function of each muscle may be different. Additional examinations of the muscle structures are required for verification of the influence of the masticatory muscles on facial morphology.

MR perfusion measurement of contrast uptaking lesions: consideration of T2* shortening due to interstitial contrast agent.

AIM: In MR perfusion measurements of contrast uptaking lesions, time intensity curves are hampered by T 1 shortening as well as by the change of T 2 * due to interstitial contrast material (CM). Using double echo sequences, the influence of T 1 can be mathematically eliminated. For correction of the T 2 * influence an empirical algorithm using time-intensity-curves exclusively measured in the suspected lesion is proposed. METHODS: The interstitial CM concentration is assumed to be proportional to the change of the intensity for T E = 0 or to the change of the relaxation rate DeltaR 1 respectively. The intravascular CM concentration is estimated from DeltaR 2 *. It is adjusted to zero for a time point sufficiently late after the bolus injection by subtraction of the interstitial concentration. This method was applied to double echo FLASH measurements on 15 pharyngeal tumors. RESULTS: The proposed correction transforms the time dependence of the estimated intravascular CM concentration into a plausible course. CONCLUSION: Double echo perfusion measurements can be corrected for the interstitial CM induced T 2 * shortening without additional measurements with proneness to errors. This does not necessarily improve the diagnostic value, since possibly "implied multivariate aspects" of uncorrected parameters (here: contrast uptake of the lesion is related to tumor neoangiogenesis as well) are eliminated.

Relations between IL-3-induced proliferation and in vitro cytokine secretion of bone marrow cells from AML patients.

The influence of IL-3 on the bone marrow cells of 53 patients with acute myeloid leukaemia (AML) was investigated after 72 h suspension in cultures by analysing the proliferation of blasts and the secretion of cytokines. The titres of IL-1beta IL-6, TNF-alpha and IL-3 were measured in the supernatants of these cultures with ELISA tests. Comparing the percentage of cells in S-phases of control cultures and cultures with IL-3, the leukaemias were divided into two growth pattern groups: IL-3-insensitive (n=19) and IL-3-sensitive (n=34) leukaemias. The IL-3-insensitive AML cells show a greater ability for autonomous growth, first by the increase of S-phase in the control culture compared with the S-phase in vivo (P=0.0486) and second, by the higher constitutive secretion (control culture) of IL-1beta P =0.0004), IL-6 ( P =0.0395) and TNF-alpha P=0.0005). The IL-3-induced secondary cytokine secretion is also different in the two growth pattern groups. Whereas in the IL-3-insensitive AML cells a moderate increase of IL-1beta (1.48-fold increase) was present, in the IL-3-sensitive AML cells a 4.72-fold increase of IL-1beta 2.71-fold increase of IL-6 and 11.81-fold increase of the TNF-alpha titre could be detected. Overall, the data show an inverse correlation between the ability of AML cells to respond to IL-3 with increase of an S-phase and the constitutive secretion of IL-1beta, II-6 and TNF-alpha. A further effect of IL-3 is the induction of secondary cytokine secretion in the bone marrow of IL-3-sensitive growing AML cells.

[Detection of aneurysm in subarachnoid hemorrhage--CT angiography vs. digital subtraction angiography]. / Aneurysmanachweis bei Subarachnoidalblutung--CT-Angiographie versus digitale Subtraktionsangiographie.

PURPOSE: The value of CT-angiography (CT-A) for the visualization of intracranial aneurysms was more closely defined by comparison with digital subtraction angiography (DSA). METHODS: Over a period of 18 months a total of 106 patients in whom a subarachnoidal hemorrhage had been detected on native CT were examined in parallel by spiral CT and DSA. CT-angiography was performed under standardized parameters and included processing with 3D surface reconstructions. RESULTS: In 64 patients (60.4%) a total of 72 aneurysms were detected. In four cases (6.2%) there were two and in two cases (3.1%) even three aneurysms. The findings of DSA and CTA agreed in 98 cases (92.5%). In four patients (3.8%) a false negative result was obtained in CTA and the initial DSA. CONCLUSIONS: Digital subtraction angiography must still be considered as the gold standard in the diagnosis of cerebral aneurysms. On account of its excellent spatial delineation of aneurysms and possibilities for exact measurements, CT-angiography represents a valuable, supplementary method--in some cases also an alternative method--to digital subtraction angiography.