Somatom Plus Research Articles

Comparison of computed tomography dose reporting software

Computed tomography (CT) dose reporting software facilitates the estimation of doses to patients undergoing CT examinations. In this study, comparison of three software packages, i.e. CT-Expo (version 1.5, Medizinische Hochschule, Hannover, Germany), ImPACT CT Patients Dosimetry Calculator (version 0.99×, Imaging Performance Assessment on Computed Tomography, www.impactscan.org) and WinDose (version 2.1a, Wellhofer Dosimetry, Schwarzenbruck, Germany), has been made in terms of their calculation algorithm and the results of calculated doses. Estimations were performed for head, chest, abdominal and pelvic examinations based on the protocols recommended by European guidelines using single-slice CT (SSCT) (Siemens Somatom Plus 4, Erlangen, Germany) and multi-slice CT (MSCT) (Siemens Sensation 16, Erlangen, Germany) for software-based female and male phantoms. The results showed that there are some differences in final dose reporting provided by these software packages. There are deviations of effective doses produced by these software packages. Percentages of coefficient of variance range from 3.3 to 23.4 % in SSCT and from 10.6 to 43.8 % in MSCT. It is important that researchers state the name of the software that is used to estimate the various CT dose quantities. Users must also understand the equivalent terminologies between the information obtained from the CT console and the software packages in order to use the software correctly.

Minimum slicing interval and frequency for CT-based prediction of pig’s body composition

The aims of our study were to test the effect of CT scanning protocol on the fattening performance of pigs, and the necessary scanning interval to accurately estimate tissue volumes in the body of pigs. A total of 16 Large White type pigs were used in this study. Pigs were kept individually and in concrete floor pen and fed at the level of 3.0 times of the maintenance energy requirements. Eight pigs were scanned at 30, 40, 50, 60, 75, 90 and 105kg live weight, while another eight pigs were not scanned during the fattening period. The scanning was performed with Siemens Somatom Plus spiral computer tomograph from head to tail with 10mm slice thickness and 10mm distances between the images. In conclusion restrictedly fed pigs can be examined with CT several times without negative effect on growing performance, but in the fattening phase some reduction in feed conversion can be expected. For the accurate determination of tissue volumes scanning of every 5th cm is sufficient in the 30-105 kg live weight range.

Radiation doses in examination of lower third molars with computed tomography and conventional radiography

To measure organ doses and calculate effective doses for pre-operative radiographic examination of lower third molars with CT and conventional radiography (CR). Measurements of organ doses were made on an anthropomorphic head phantom with lithium fluoride thermoluminescent dosemeters. The dosemeters were placed in regions corresponding to parotid and submandibular glands, mandibular bone, thyroid gland, skin, eye lenses and brain. The organ doses were used for the calculation of effective doses according to proposed International Commission on Radiological Protection 2005 guidelines. For the CT examination, a Siemens Somatom Plus 4 Volume Zoom was used and exposure factors were set to 120 kV and 100 mAs. For conventional radiographs, a Scanora unit was used and panoramic, posteroanterior, stereographic (scanogram) and conventional spiral tomographic views were exposed. The effective doses were 0.25 mSv, 0.060 mSv and 0.093 mSv for CT, CR without conventional tomography and CR with conventional spiral tomography, respectively. The effective dose is low when CT examination with exposure factors optimized for the examination of bone structures is performed. However, the dose is still about four times as high as for CR without tomography. CT should therefore not be a standard method for the examination of lower third molars. In cases where there is a close relationship between the tooth and the inferior alveolar nerve the advantages of true sectional imaging, such as CT, outweighs the higher effective dose and is recommended. Further reduction in the dose is feasible with further optimization of examination protocols and the development of newer techniques.

The Targeted Oncolytic Poxvirus JX-594 Demonstrates Antitumoral, Antivascular, and Anti-HBV Activities in Patients With Hepatocellular Carcinoma

JX-594 is a targeted oncolytic poxvirus that is designed to eradicate cancer cells having cell-cycle defects, through replication, cell lysis, and spread within tumors; oncolysis-induced tumor vascular shutdown and immunostimulation are augmented by granulocyte monocyte-colony-stimulating factor (GM-CSF) transgene expression. We have previously shown, in animal models of hepatocellular carcinoma (HCC), that JX-594 is a promising anticancer agent. We tested JX-594 in three patients with advanced refractory hepatitis B virus (HBV)-associated HCC through intratumoral administration. JX-594 treatment was well-tolerated and resulted in antitumoral efficacy in all three patients, despite the presence of high levels of neutralizing antibodies. JX-594 replication, its release into the circulation, distant tumor targeting were demonstrated. JX-594 administration resulted in the induction of antivascular cytokines, and was associated with tumor vascular shutdown. We also showed, for the first time, that oncolytic virotherapy can suppress underlying HBV replication in HCC patients, and that tumor tissue could be the primary source of acute HBV replication and acute post-treatment HBV release. JX-594 treatment in HBV-associated HCC warrants further clinical testing; a Phase II trial is underway.

TU-FF-A4-02: Impact of Sinogram Modeling Inaccuracies On Image Quality in X-Ray CT Imaging Using the Alternating Minimization Algorithm

Purpose: To provide a scientific basis for setting sinogram modeling accuracy targets based on impact of such errors on image quality. Modeling inaccuracies in photon spectrum and scatter distribution assumed by statistical image reconstruction (SIR) algorithms lead to systematic image artifacts. Methods and Materials: A synthetic two-dimensional phantom (25×35 cm) was used to generate both noiseless and noisy sinogram data, based upon a 120 kVp spectrum filtered by 12 mm Al (66.6 keV mean energy)and variable scatter levels (4%, 20%, and 100% of the minimum primary transmission through the phantom). A third generation Siemens Somatom Plus 4 scanner geometry was assumed. The SIR algorithm was the alternating minimization (AM) algorithm [IEEE TMI 26:283]. 500 AM iterations using 22 ordered subsets were applied to the data. Various mismatches between the assumptions in the algorithm and the truth were studied, including erroneous spectra (110kVp to 130kVp, filtration from 6 mm to 18 mm Al, or 62.2 to 69.7 keV mean energy) and erroneous scatter levels (0.25 to 4.0 times the actual sinogram scatter). Result: AM image quality was evaluated in terms of bias, noise, contrast ratio, etc. To assure +/−2% accuracy in the reconstructed attenuation image, photon spectrum uncertainties corresponding to 2 keV shifts in mean energy can be tolerated. For a 30 cm thick subject, this corresponds to errors in primary transmission of 6%–8%. For 20% scatter levels, the maximum tolerated discrepancy in scatter-to-primary ratio (SPR) is about 5% to 8%and 30%–50% for typical MSCT scatter levels. Conclusions: This work indicates AM and other SIR algorithm image estimates are sensitive to errors in the detector response models assumed by the algorithms. For thick patients, a sinogram modeling accuracy of 6% is needed to support reconstructed images of 2% accuracy. Supported in part by NIH grant R01 CA 075371.

SU‐FF‐I‐36: Improving Noise‐Resolution Tradeoffs in X‐Ray CT Imaging by Statistical Image Reconstruction

Purpose: To assess the potential of a statistical image reconstruction (SIR) algorithm, penalized alternating minimization (AM) [IEEE TMI 26: 283] for improving image quality, relative to filtered back projection (FBP), for a given imaging dose. Minimizing the x‐ray CT imaging dose is an important goal both for CT‐guided radiotherapy and for imaging of pediatric patients and screening healthy populations. Method and Materials: Synthetic datasets with Poisson noise were formed from cylindrical phantoms with a variety of simulated high and low contrast features. A penalized AM algorithm based on separable surrogate penalty functions was implemented and investigated for Good's roughness penalty, an edge‐preserving log‐cosh penalty, and a novel penalty on local transmission fluctuations, all of which were applied only to adjacent pixels. Simulations were performed for a Somatom Plus 4 third generation geometry. Image blur (resolution) was specified in terms of the FWHM (σ) of the Gaussian, which when convolved with the truth image, best matched the estimated image. Resolution was varied by adjusting the filter cutoff frequency for FBP and the Lagrange multiplier for AM. Noise was quantified by image intensity variance in a uniform region. Results: For a fixed photon fluence, penalized AM images had smaller variances than FBP at all image blur levels, although the differences were not significant for low spatial resolution and low contrast features. However, for clinically relevant σ < 2 mm, the advantage of AM increased with increasing spatial resolution and contrast. For example, at σ = 1 mm, FBP had 48% and 24% larger variances for 75% contrast inserts with 0.5 mm pixels and 10% contrast with 1 mm pixels. The three penalty functions had comparable performance. Conclusion: Regularized AM SIR has the potential to realize signal‐to‐noise ratio gains equivalent to 30% imaging dose increases.Supported in part by R01 CA075371.

A shift in the diagnostics of the small intestine tumors

Primary, secondary, benign or malignant tumorous diseases of the small intestine are rare. They are very often diagnosed by accident or as a cause of acute abdomen. This work should answer the question, whether there is a method of making the diagnosis earlier when the disease is limited and easy to cure. Methodology A retrospective study comprising 96 patients having undergone surgery for a small intestine tumor in our hospital from 1996 to 2005 is presented. An analysis of first symptoms, diagnostic methods and number of patients admitted during the years was made. In the year 1998 we changed our philosophy in trying to directly detect the small intestine pathology and not making the diagnosis by the exclusion only. Intestinal ultrasound was performed on the Ultramark 3000 HDI device with autofocussable convex 5 MHz and linear 7.5 MHz probes or nowadays ATL 5000 HDI, 7–12 MHz linear probe. No contrast enhancement was used. Abdominal CT engaged Somatom Plus appliance by Siemens, single detector with our conventional abdominal CT protocol. Enteroclysis was done with Micropaque suspension diluted 1:1 with HP-7000 300 ml with its application rate of 75 ml/min followed by HP-7000 solution 2000 ml, application rate of 120 ml/min. Results We treated surgically 96 patients with the small intestine tumor. A shift in the diagnostic algorithm was noticed in the bowel ultrasound now taking the lead. An enlarged portion of patients diagnosed by means of capsule endoscopy was also seen. An increase of surgically treated patients after 1998 was recorded and the majority of them could be offered an elective laparoscopic surgery in contrast to before 1998 when the majority of them had undergone surgery for an acute abdomen. Conclusion The small bowel ultrasound can be recommended as the first choice method. All patients with even very moderate abdominal symptoms ought to be examined for the small intestine pathology. As a result one can get higher rate of elective surgery, if possible laparoscopic and higher number of R0 resections accompanied by longer survival.

Amyloidosis of the small intestine

Amyloidosis is a rare disease characterized by forming pathological protein deposits – amyloid – in many organs and tissues. This decreases their functionality. The aim of this small study was to determine, whether the radiological picture of the small intestine involvement in amyloidosis is in some sense specific as sometimes described in literature giving rise to high suspicion for the disease in symptomatic patients. Material and methods The prospective study comprising seven patients hospitalized in surgical department is presented together with a survey on the disease, its appearance in radiological imaging. All patients underwent abdominal ultrasound (ATL 5000 HDI, 7–12 MHz linear probe, no contrast enhancement, supine position), abdominal CT (Somatom Plus, Siemens, single detector, conventional abdominal CT protocol) and enteroclysis (Micropaque suspension 300 ml, application rate of 75 ml/min, dilution with HP-7000 being 1:1 and HP-7000 solution 2000 ml, application rate of 120 ml/min.). Results The amyloid deposits in the small intestine could be visualized in five of seven patients with the disease. Enteroclysis revealed a diffuse slowed down intestinal motility with an obstruction-like picture in all of our seven patients. The intestinal secretion was normal, plicae were getting polyp-like shape in five of them forming so called “thumb printing” picture. CT showed thickening of the intestinal wall due to deposits with poor blood supply and contrast retention in five of seven patients. Ultrasound visualized thickened, hypoechoic nodular plicae and slowed down motility in these five patients. The most striking finding was the pathological deposits in the intestinal wall were highly hypo-vascular. However, this picture is very similar to that of ischemic enteritis. All seven patients had proven amyloid deposits from bioptic specimens. Conclusion The diagnosis of amyloidosis must be supported by bioptic examination as it has no pathognomic radiological picture. Nevertheless, it allows usually to rise a high suspicion for this and sometimes even guess the type of the pathological protein involved. This can start a search for the primary reason of possible amyloidosis and thus perhaps spear the patients quality of life.

Vergleichende computertomographische und kernspintomographische Beurteilung von Wirbelsäulenverletzungen der BWS und LWS anhand der Magerl-Klassifikation

A feasibility study of the classification of spine injuries by CT and MRI data according to the classification of Magerl for spine injuries. In 39 patients, 46 injured vertebrae were evaluated by means of CT and MRI. A single-slice helical CT (Somatom Plus S, Siemens, Erlangen, Germany) was used with a collimation and feed of 2 mm and 3 mm, respectively. Sagittal reformations were reconstructed from these data sets. MR imaging was performed with 1.5T and 1.0T machines (Magnetom Vision and Magnetom Impact, Siemens). Transverse and sagittal T1-w SE- images as well as sagittal T2-w TSE- and STIR-images were generated. Each fractured vertebra was independently categorized two times according to the classification of Magerl on the basis of CT- and MRI-images. The CT- and MRI-classifications were subsequently compared. Most fractures were classified as impaction fractures (A1) or burst fractures (A3). Only 5/46 injuries of vertebrae were not given the same classification by means of CT and MRI (r = 0.9). MRI showed more bony lesions than CT (n. s., p > 0.05) and was able to evaluate ruptures of the longitudinal ligaments in 5 patients. Classification of spine injuries according to the Magerl-classification showed a significant agreement between CT and MRI and therefore a comparable evaluation of stability. MRI was superior in delineating ligamental lesions.

Imaging After a Whipple Operation

Spiral computed tomography (CT) examination of patients after a Whipple operation often raises questions concerning the afferent loop. This study evaluates the efficiency of biliary contrast medium (BCM) in visualizing opacification of this loop. After undergoing a Whipple operation, 31 patients received 100 mL BCM before postoperative spiral CT (Somatom Plus 4; Siemens, Erlangen, Germany: 5- or 10-mm slices, feed of 7 or 12 mm/s; Volume Zoom; Siemens: 2.5 mm collimation, total feed of 15 mm/s). Semiquantitative evaluation included opacification of the jejunal loop and visibility of jejunostomies. Complications and tumor recurrences were recorded. In all patients, BCM was successfully administered without complications. Afferent loop opacification was seen in 95% of examinations with BCM versus 5% of examinations with oral contrast medium. Evaluation of jejunostomies was unequivocally facilitated by BCM. Three previously undetermined changes were identified as tumor recurrence, and recurrence was ruled out after examination with BCM in 7 cases. After a Whipple operation, opacification of the afferent loop can be regularly achieved by intravenous administration of BCM, which eases distinction of normal postoperative changes from local tumor recurrence. Administration of BCM is recommended as a standard diagnostic procedure in these patients.

Comparison of metric analysis of spinal structures, exemplarily of the ligamentum flavum, obtained with CT and MRI

Purpose: Comparison of metric analysis of spinal structures, exemplarily of the ligamentum flavum, obtained with computed tomography (CT) (soft tissue window and bone window) and magnetic resonance imaging (MRI) (T1 and T2 weighted images). Material and methods: Forty-six lumbar ligamenta flava of 46 patients (25 women and 21 men) were examined at a Somatom Plus 4 (Siemens, Erlangen, FRG) and at a 1.5 T clinical scanner (Magnetom Vision, Siemens, Erlangen, FRG). Two independent neuroradiologists measured the thickness of the ligamenta flava in mm. Statistics included Pearson’s correlation coefficient and the intra-class correlation coefficient. Results: Mean values did not differ significantly. The correlation coefficients varied between 0.69 and 0.98. The best correlation occurred comparing the same techniques in different windowing and weighting (CT: r=0.98; MRI: r=0.95). Correlating different techniques the combination of CT bone window and T1 weighted images presented the best result ( r=0.75). Conclusions: Because of the excellent correlation between the examined techniques CT as well as MRI can equally be used to measure distances of spinal structures.

Réalisation d’un banc de mesure dynamique pour estimer la fonction de transfert de modulation d’un scanner multicoupes

This paper describes a method for evaluation of the modulation transfer function (MTF) on a multislice CT (Somatom Plus 4 VZ, Siemens) with a dynamic test object. CT allows imaging of slices of the human body for diagnosis purposes. Multislice CT opens new diagnostic possibilities for imaging of moving organs. Clinical evaluations are done for the analysis of the heart and the coronary arteries. Commercially available phantoms for CT performance analysis are unfortunately only static devices. The presented dynamic test bench was developed to evaluate acquisition and reconstruction parameters on moving parts. The evaluations of the temporal and spatial resolutions are the two main criteria for coronary arteries imaging.

Multidetector-computed tomography for coronary artery operation planning: evaluation of the method

Background: Planning of coronary artery bypass grafting (CABG) in severe three-vessel-disease (3-CAD) needs three-dimensional (3D) information. We evaluated spiral multidetector-computed tomography (MDCT) as surgical planning tool. Methods: A total of 450 coronary segments was evaluated. The study (30 patients) used MDCT (Siemens, Somatom Plus 4 VZ, retrospective gating). 3D-reconstructions were used to score both, suitability for coronary anastomosis, and stenosis quantification. Influence of reconstruction time, heart rate, slice thickness (1.25 vs. 3 mm) was evaluated. Coronary angiography (angio) was carried out in each patient. Scorings were performed by three observers. Results: Temporal resolution was 170 ms. Mean sensitivity for correct bypass indication was 27.9% (1.25/3.0-mm slices: 22.2/17.1%), specificity 85.0% (93.5/88.9%). For detecting stenosis, sensitivity reached 32.3% (35.5/34.7%), specificity 88.5% (88.9/87.3%). Maximum κ-coefficient for MDCT was 0.25 (angio: 0.40). Visibility was best at reconstruction time 400 ms, heart rate <80 beats per minute, bpm ( p<0.0001 vs. >80 bpm), slice thickness of 3 mm ( p<0.05 vs. 1.25 mm). Agreement of stenosis grading was 48.9 %. Conclusions: Operation planning of CABG is facilitated using MDCT by providing data of high specificity. MDCT fails to provide reliable data on stenosis quantification. Interobserver variability is high. Modern cardiac surgery (navigation, robotics) may be facilitated.

Functional CT imaging: Load-dependent visualization of the subchondral mineralization by means of CT osteoabsorptiometry (CT-OAM)

Functional computed tomography for visualization and quantification of subchondral bone mineralization using CT osteoabsorptiometry (CT-OAM). Tarsometatarsal (TMT) and metatarsophalangeal (MTP) joints of 46 human hallux valgus (HV) specimens were examined (sagittal 1/1/1 mm) on a single slice CT scanner SCT (Somatom Plus 4, Siemens AG). Subchondral bone pixels were segmented and assigned to 10 density value groups (Delta 100 HU, range 200 - 1200 HU) the pixels using volume rendering technique (VRT). The data analysis considered the severity of HV as determined by the radiographically measured HV-angle (a. p. projection). CT-OAM could generate reproducible densitograms of the distribution pattern of the subchondral bone density for all four joint surfaces (TMT and MTP joints). The bone density localization enables the assignment to different groups, showing a characteristic HV-angle-dependent distribution of the maximum bone mineralization of the load-dependent densitogram (p < 0.001). CT-OAM is a functional CT technique for visualizing and quantifying the distribution of the subchondral bone density, enabling a noninvasive load-dependent assessment of the joint surfaces. Load-dependent densitograms of hallux valgus specimens show a characteristic correlation with an increase of the HV-angle.

CT calibration for two-dimensional scaling of proton pencil beams

For proton dose calculations in heterogeneous media, it was shown in a previous work that the conventional pencil beam approach based on pathlength scaling does not properly account for scattering effects in nonwater media (Szymanowski and Oelfke 2002 Phys. Med. Biol. 47 3313–30). A two-dimensional scaling method was therefore introduced, which is able to predict with high accuracy the propagation of proton pencil beams both along the depth and the lateral directions in inhomogeneous media. In order to integrate this improved pencil beam algorithm in a CT based treatment planning system, two CT calibration curves are needed. The first one relates the Hounsfield numbers to the relative stopping powers, as for the conventional pencil beam approach. The second curve is to relate the Hounsfield numbers to the material-specific lateral scaling factors. The purpose of this work is to provide the CT calibration curves needed for the integration of the pencil beam algorithm featuring the two-dimensional scaling method. Similarly to as suggested by Schneider et al (1996 Phys. Med. Biol. 41 111–24) for the calibration curve in terms of stopping powers, we follow a stoichiometric procedure to get the calibration curve in terms of material-specific lateral scaling factors. The calibration curves for a CT scanner of the type Siemens Somatom Plus 4 are obtained from the analytical calculation of the CT Hounsfield numbers, relative stopping powers and material-specific lateral scaling factors for human biological tissues.

Feasibility of ultra-low-dose multislice CT colonography for the detection of colorectal lesions: preliminary experience.

Our objective was to evaluate the feasibility of ultra-low-dose scanning for multislice CT colonography in the detection of colorectal lesions. Twenty-seven patients (14 men, 13 women) with clinical indication for conventional colonoscopy were recruited. Multislice spiral CT (Somatom Plus 4 Volume Zoom, Siemens, Germany) examinations were performed after standard oral colonoscopic preparation and colonic distension with room air. Images were acquired using 2.5-mm collimation, 3.0-mm slice thickness, standard reconstruction kernel, 140 kVp, and 10 mAs. Supine and prone acquisitions were obtained in all patients. Images were analyzed on a workstation by two gastrointestinal radiologists. Conventional colonoscopy was performed on the same day in all patients and represented the standard of reference. Total radiation exposure was also calculated. All colorectal cancers were correctly identified at CT colonography (9 of 9, sensitivity 100%). The CT colonography also detected 10 of 12 polyps (overall sensitivity 83.3%). Based on polyp diameter, the sensitivity for the detection of polyps 10 mm or larger was 100% (3 of 3); between 6 and 9 mm, 100% (3 of 3); and 5 mm or smaller, 66.6% (4 of 6). Total radiation exposure for prone and supine acquisitions combined was 1.7 mSv (for men) and 2.3 mSv (for women). Although preliminary, our experience suggests that ultra-low-dose scanning for multislice CT colonography is feasible. This technique provides a sensitivity comparable to that of previous experiences with CT colonography but with a 40-70% reduction of the radiation dose delivered to patients.

Experimental colonic phantom for the evaluation of the optimal scanning technique for CT colonography using a multidetector spiral CT equipment.

Our objective was to optimize a scanning protocol for CT colonography using a multidetector scanner with an adaptive-array matrix in a phantom study. A colonic phantom with 27 simulated lesions was examined using a multidetector CT scanner (Somatom Plus 4 Volume Zoom, Siemens, Erlangen, Germany). Three scanning protocols were tested: (a) collimation 1.0 mm, slice thickness 1.0 mm; (b) collimation 2.5 mm, slice thickness 3.0 mm; and (c) collimation 2.5 mm, slice thickness 5.0 mm. Image analysis was performed by two radiologists blinded to the construction of the phantom and to imaging parameters. Sensitivity for lesion detection and image quality was assessed. Computed tomographic colonography detected 27 of 27 lesions with protocol 1 (sensitivity 100%); 26 of 27 lesions with protocol 2 (sensitivity 96.3%); and 23 of 27 lesions with protocol 3 (sensitivity 85.2%). Image quality was graded as optimal for protocol 1, good for protocol 2, and poor for protocol 3. When multidetector CT equipment with an adaptive-array matrix is used, protocols with 1.0- or 3.0-mm slice thickness have a sensitivity for the detection of lesions higher than that obtained with a 5.0-mm slice thickness. Image quality decreases progressively when the slice thickness is increased; therefore, in a clinical setting, we recommend the use of a high-resolution protocol (1.0-mm effective slice thickness) with the highest pitch value in order to reduce scanning time. Dose exposure for such a protocol if combined with 80 mAs is within the range limits recommended by the ICRP for abdominal CT scanning.

Observing the density increase curve after intravenous contrast medium administration using a bolus triggering system: a method for detection cardiovascular disorders?

Recently bolus tracking systems were developed to improve the timing of intravenous contrast media application in helical computed tomography. We investigated the benefit of this new method as a parameter of the cardiac function. Retrospective analysis of 64 patients which incidentally underwent bolus triggered contrast enhanced helical CT and invasive investigation of the heart within one week. All examinations were performed on the CT scanner Somatom Plus 4 Volume Zoom (Siemens Corp., Forchheim, Germany) using the C.A.R.E. Bolus software. This performs repetitive low-dose test scans (e.g. for the abdomen: 140 kV, 20 mA, Tl 0.5 s) and measures the Hounsfield attenuation (increase over the baseline) in a preselected region of interest. The displayed increase of vascular density over the time after peripheral contrast media injection (75 ml lopromid (300 mg/ml), 2 ml/s) was categorised to three types: (a) rapid increase, (b) deceleration before a 100 HE threshold was reached and (c) one or more peaks. The findings of the invasive investigation of the heart were correlated to the findings of the bolus-tracking measurements. The examinations were categorized as follows: 19 type A, 34 type B, 11 type C. We found a high significant correlation between the type of the Hounsfield attenuation and systolic pressure in the left ventricle. There was no correlation between the type of the Hounsfield attenuation and the diastolic pressure in the left ventricle, the pressures related to the right ventricle or the ejection fraction. The bolus-tacking system showed a sensitivity of 53, a specificity of 82, an accuracy of 70%, a positive predictive value of 70% and a negative predictive value of 70% in detection of left heart failure. The bolus tracking system C.A.R.E.-bolus often shows atypical Hounsfield attenuation in cases of cardiac failure but is not suitable as a screening method of the cardiopulmonary function.

CT Fluoroscopy-assisted Puncture of Thoracic and Abdominal Masses: A Randomized Trial

PURPOSE: We investigated the benefit of real-time guidance of interventional punctures by means of computed tomography fluoroscopy (CTF) compared with the conventional sequential acquisition guidance. MATERIAL AND METHODS: In a prospective randomized trial, 75 patients underwent either CTF-guided (group A,n=50) or sequential CT-guided (group B,n=25) punctures of thoracic (n=29) or abdominal (n=46) masses. CTF was performed on the CT machine (Somatom Plus 4 Power, Siemens Corp., Forchheim, Germany) equipped with the C.A.R.E. Vision application (tube voltage 120kV, tube current 50mA, rotational time 0.75s, slice thickness 10mm, 8 frames/s). RESULTS: The average procedure time showed a statistically significant difference between the two study groups (group A: 564s, group B 795s,P=0.0032). The mean total mAs was 7089mAs for the CTF and 4856mAs for the sequential image-guided intervention, respectively. The sensitivity was 71% specificity 100% positive predictive value 100% and negative predictive value 60% for the CTF-guided puncture, and 68, 100, 100 and 50% for sequential CT, respectively. CONCLUSION: CTF guidance realizes a time-saving but increases the radiation exposure dosage .Kirchner, J. et al. (2002) Clinical Radiology57, 188–192

Dosisreduktion bei der Spiral-CT: Detektion von Lungenrundherden mit und ohne anatomisch angepasster Röhrenstrommodulation

To investigate the potential of projection angle-dependent anatomical adaptation of tube current to reduce dose in spiral CT examinations of the thorax without loss in detectability of pulmonary nodules and image quality. Dose can be reduced for non-circular patient cross-sections without an increase in noise if the tube current is reduced at those angular positions where the patient diameter and, consequently, attenuation are small. The examinations were dose with SOMATOM Plus 4 (Siemens AG). CT projection data were analysed to determine the optimum tube current for each projection angle in real time. We compared image quality, done, and detection rates of pulmonary nodules for thoracic spiral CT examinations with and without online anatomically adapted tube current control in a group of 38 patients. Three radiologists counted all intrapulmonary nodules in consensus separated in three different groups (< 5 mm, 5-10 mm, > 10 mm). Image quality was evaluated in a scale from 1-3 (1 = very good, 2 = good, 3 = worse). On average, the dose was reduced by 21% (15-34%). With a constant tube current, 704 pulmonary nodules were detected, with tube current modulation 707 pulmonary nodules. For three patients we saw more pulmonary nodules (five) with tube current modulation, for two patients we saw less pulmonary nodules (two). In a direct comparison, the missed intrapulmonary nodules were also detected in the respective method. Thus, the detection rate of intrapulmonary nodules was uninfluenced. In general, no deterioration of image quality was observed. On average, 21% dose reduction was achieved by an anatomically adapted tube current modulation in spiral CT examinations of the thorax without a loss in detectability of pulmonary nodules and image quality. This method is an important contribution to dose reduction in spiral CT.