ABSTRACT
PURPOSE: To evaluate the feasibility of the classification of endoleaks following endovascular aortic aneurysm repair using the time-to-peak of the contrast agent in CEUS examinations. MATERIAL AND METHODS: In this retrospective study, a cohort of 171 patients with a total of 489 CEUS follow-up examinations after EVAR were included. In 254 of the 489 examinations, an endoleak was seen and the time-to-peak was measured in seconds. Existence of an endoleak was confirmed by CT as the gold standard. RESULTS: We evaluated 254 CEUS video sequences showing an endoleak out of a total of 489 examinations. Kruskal-Wallis test revealed with p = 0.001 differences between the single endoleak types based on the time to peak. Correction after Bonferroni showed significant differences between type Ia compared to Ib and to IIa over inferior mesenteric artery (IMA) and IIa over lumbar artery (LA). There are also disparities between type Ib and type IIa IMA and type III, furthermore between type IIa IMA compared to IIa LA and type III as well as type IIa LA matched to type III. CONCLUSION: CEUS is an important method for the follow-up after EVAR. The time-to-peak does not seem to be a useful additional feature in classifying endoleaks, although there are differences between the time-to-peak of the single endoleak types and it is possible to make an order of the different endoleak types referring to the mean values.
Subject(s)
Aortic Aneurysm, Abdominal/surgery , Endoleak/classification , Image Enhancement/methods , Ultrasonography, Interventional/methods , Aortic Aneurysm, Abdominal/diagnostic imaging , Cohort Studies , Contrast Media , Female , Follow-Up Studies , Humans , Male , Radiography , Retrospective StudiesABSTRACT
PURPOSE: Purpose of the study was to compare radiological treatment response according to RECIST, Choi and volumetry in GIST-patients under 2nd-line-sunitinib-therapy and to correlate the results of treatment response assessment with disease-specific survival (DSS). PATIENTS AND METHODS: 20 patients (mean: 60.7 years; 12 male/8 female) with histologically proven GIST underwent baseline-CT of the abdomen under imatinib and follow-up-CTs 3 months and 1 year after change to sunitinib. 68 target lesions (50 hepatic, 18 extrahepatic) were investigated. Therapy response (partial response (PR), stable disease (SD), progressive disease (PD)) was evaluated according to RECIST, Choi and volumetric criteria. Response according to the different assessment systems was compared and correlated to the DSS of the patients utilizing Kaplan-Meier statistics. RESULTS: The mean DSS (in months) of the response groups 3 months after therapy change was: RECIST: PR (0/20); SD (17/20): 30.4 (months); PD (3/20) 11.6. Choi: PR (10/20) 28.6; SD (8/20) 28.1; PD (2/20) 13.5. Volumetry: PR (4/20) 29.6; SD (11/20) 29.7; PD (5/20) 17.2. Response groups after 1 year of sunitinib showed the following mean DSS: RECIST: PR (3/20) 33.6; SD (9/20) 29.7; PD (8/20) 20.3. Choi: PR (10/20) 21.5; SD (4/20) 42.9; PD (6/20) 23.9. Volumetry: PR (6/20) 27.3; SD (5/20) 38.5; PD (9/20) 19.3. CONCLUSION: One year after modification of therapy, only partial response according to RECIST indicated favorable survival in patients with GIST. The value of alternate response assessment strategies like Choi criteria for prediction of survival in molecular therapy still has to be demonstrated.
Subject(s)
Gastrointestinal Stromal Tumors , Imaging, Three-Dimensional/methods , Indoles/therapeutic use , Liver Neoplasms , Peritoneal Neoplasms , Pyrroles/therapeutic use , Radiographic Image Interpretation, Computer-Assisted/methods , Tomography, X-Ray Computed/methods , Adolescent , Adult , Algorithms , Antineoplastic Agents/therapeutic use , Disease-Free Survival , Female , Gastrointestinal Stromal Tumors/diagnosis , Gastrointestinal Stromal Tumors/drug therapy , Gastrointestinal Stromal Tumors/secondary , Humans , Liver Neoplasms/diagnosis , Liver Neoplasms/drug therapy , Liver Neoplasms/secondary , Male , Middle Aged , Peritoneal Neoplasms/diagnosis , Peritoneal Neoplasms/drug therapy , Peritoneal Neoplasms/secondary , Reproducibility of Results , Sensitivity and Specificity , Sunitinib , Survival Analysis , Treatment Outcome , Tumor Burden , Young AdultABSTRACT
In morbidly obese patients, computed tomography frequently represents the only viable option for non-invasive imaging diagnostics. The aim of this study was to analyze the weight limits, dose and image quality with standard CT scanners and to determine the diagnostic value and dose with a dual source XXL mode.A total of 15 patients (average body weight 189.6 ± 42 kg) were retrospectively identified who had been examined with the XXL mode. Of these patients 7 (average body weight 176.4 ± 56 kg) had been examined using both the XXL and standard protocols allowing for an intraindividual comparison in this subcollective. Additionally 14 patients weighing between 90 and 150 kg (average 106.1 ± 19 kg) examined with standard protocols were included as references. Dose, image noise and subjectively assessed image quality (rating scale 1-4) were determined. Additionally, a large abdomen phantom of 48 cm diameter was examined with both protocols at equivalent tube current-time product in order to compare the dose efficiency.The patient groups differed significantly in dose (CTDI(vol) XXL 72.9 ± 23 versus standard 16.7 ± 11 mGy; intraindividual 64.1 ± 20 versus 27.0 ± 15 mGy). The image noise was generally somewhat higher in the XXL group but significantly lower in the intraindividual comparison (liver 24.2 ± 14 HU versus 36.3 ± 20 HU; p = 0.03; fat 15.5 ± 8 HU versus 26.2 ± 12 HU; p=0.02). With ratings of 1.9 ± 0.7 and 1.8 ± 0.7 image quality did not differ significantly in general, whereas there was a clear difference in the intraindividual comparison (1.8 ± 0.8 versus 3.0 ± 1.2) and only the XXL protocol achieved diagnostic quality in all cases, while 43% of the examinations with the standard protocol were rated as non-diagnostic. The quantification of dose efficiency in the phantom scans yielded no significant difference between the protocols.Up to 150 kg body weight, CT can be performed with the standard technique at 120 kVp with tube current modulation. In larger patients diagnostic image quality can only be achieved reliably with the dual source XXL mode, although at considerably increased calculated dose. However, standard conversion factors yield false high values so that the estimation of the biologically relevant equivalent dose is very difficult.
Subject(s)
Absorptiometry, Photon/methods , Algorithms , Overweight/diagnostic imaging , Radiographic Image Enhancement/methods , Radiographic Image Interpretation, Computer-Assisted/methods , Tomography, X-Ray Computed/methods , Female , Humans , Male , Middle Aged , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
The purpose of this study was to assess the diagnostic accuracy of whole-body MRI (WB-MRI) at 1.5 T or 3 T compared with FDG-PET-CT in the follow-up of patients suffering from colorectal cancer. In a retrospective study, 24 patients with a history of colorectal cancer and suspected tumour recurrence underwent FDG-PET-CT and WB-MRI with the use of parallel imaging (PAT) for follow-up. High resolution coronal T1w-TSE and STIR sequences at four body levels, HASTE imaging of the lungs, contrast-enhanced T1w- and T2w-TSE sequences of the liver, brain, abdomen and pelvis were performed, using WB-MRI at either 1.5 T (n = 14) or 3 T (n = 10). Presence of local recurrent tumour, lymph node involvement and distant metastatic disease was confirmed using radiological follow-up within at least 5 months as a standard of reference. Seventy seven malignant foci in 17 of 24 patients (71%) were detected with both WB-MRI and PET-CT. Both investigations concordantly revealed two local recurrent tumours. PET-CT detected significantly more lymph node metastases (sensitivity 93%, n = 27/29) than WB-MRI (sensitivity 63%, n = 18/29). PET-CT and WB-MRI achieved a similar sensitivity for the detection of organ metastases with 80% and 78%, respectively (37/46 and 36/46). WB-MRI detected brain metastases in one patient. One false-positive local tumour recurrence was indicated by PET-CT. Overall diagnostic accuracy for PET-CT was 91% (sensitivity 86%, specificity 96%) and 83% for WB-MRI (sensitivity 72%, specificity 93%), respectively. Examination time for WB-MRI at 1.5 T and 3 T was 52 min and 43 min, respectively; examination time for PET-CT was 103 min. Initial results suggest that differences in accuracy for local and distant metastases detection using FDG-PET-CT and WB-MRI for integrated screening of tumour recurrence in colorectal cancer depend on the location of the malignant focus. Our results show that nodal disease is better detected using PET-CT, whereas organ disease is depicted equally well by both investigations.
Subject(s)
Colorectal Neoplasms/diagnosis , Fluorodeoxyglucose F18 , Magnetic Resonance Imaging/methods , Neoplasm Recurrence, Local/diagnosis , Positron-Emission Tomography/methods , Tomography, X-Ray Computed/methods , Whole Body Imaging/methods , Aged , Aged, 80 and over , Female , Humans , Male , Middle Aged , Radiopharmaceuticals , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
BACKGROUND AND AIMS: This prospective trial was designed to compare the performance characteristics of five different screening tests in parallel for the detection of advanced colonic neoplasia: CT colonography (CTC), colonoscopy (OC), flexible sigmoidoscopy (FS), faecal immunochemical stool testing (FIT) and faecal occult blood testing (FOBT). METHODS: Average risk adults provided stool specimens for FOBT and FIT, and underwent same-day low-dose 64-multidetector row CTC and OC using segmentally unblinded OC as the standard of reference. Sensitivities and specificities were calculated for each single test, and for combinations of FS and stool tests. CTC radiation exposure was measured, and patient comfort levels and preferences were assessed by questionnaire. RESULTS: 221 adenomas were detected in 307 subjects who completed CTC (mean radiation dose, 4.5 mSv) and OC; 269 patients provided stool samples for both FOBT and FIT. Sensitivities of OC, CTC, FS, FIT and FOBT for advanced colonic neoplasia were 100% (95% CI 88.4% to 100%), 96.7% (82.8% to 99.9%), 83.3% (95% CI 65.3% to 94.4%), 32% (95% CI 14.9% to 53.5) and 20% (95% CI 6.8% to 40.7%), respectively. Combination of FS with FOBT or FIT led to no relevant increase in sensitivity. 12 of 45 advanced adenomas were smaller than 10 mm. 46% of patients preferred CTC and 37% preferred OC (p<0.001). CONCLUSIONS: High-resolution and low-dose CTC is feasible for colorectal cancer screening and reaches sensitivities comparable with OC for polyps >5 mm. For patients who refuse full bowel preparation and OC or CTC, FS should be preferred over stool tests. However, in cases where stool tests are performed, FIT should be recommended rather than FOBT.
Subject(s)
Adenoma/diagnosis , Colorectal Neoplasms/diagnosis , Aged , Aged, 80 and over , Colon/pathology , Colonic Polyps/diagnosis , Colonography, Computed Tomographic/methods , Colonoscopy/methods , Feces/chemistry , Female , Hemoglobins/analysis , Humans , Imaging, Three-Dimensional , Male , Middle Aged , Occult Blood , Prospective Studies , Rectum/pathology , Sample Size , Sensitivity and Specificity , Sigmoidoscopy/methods , Video RecordingABSTRACT
For patients with metastasized renal cell carcinoma (RCC), imaging techniques are of great importance. Currently, therapy widely relies on antiangiogenic factors, which frequently lead to relatively subtle changes in the size of lesions. From this aspect the commonly used RECIST criteria (response evaluation criteria in solid tumors) must be considered as imprecise for the evaluation of the response to therapy. This article gives a review on new software-based volumetric methods, which allow therapy-induced changes in the size of metastases from RCC to be detected with higher sensitivity and reproducibility. A comparison of RECIST and volumetry was carried out with data from patients with metastasized RCC to demonstrate the higher sensitivity of the 3D volumetric procedure.
Subject(s)
Algorithms , Carcinoma, Renal Cell/diagnosis , Carcinoma, Renal Cell/secondary , Image Interpretation, Computer-Assisted/methods , Imaging, Three-Dimensional/methods , Kidney Neoplasms/diagnosis , Software , Humans , Sensitivity and SpecificityABSTRACT
A quality control method is described for verifying that the coordinate systems of a PET and MR image from the same subject have the same relative left-right orientation. Such ambiguities can arise, for example, at the coordinating center receiving data from many institutions in large multisite studies. In this study, image registration was performed on the PET/MR image pair. The MR image was then reflected (left/right reversed) and the image registration was performed again. A comparison of the values of the cost function describing the accuracy of the registration was used to identify the correct relative orientation. In 122 studies using data with known orientations, 100% accuracy of the method was observed.
Subject(s)
Image Processing, Computer-Assisted/statistics & numerical data , Magnetic Resonance Imaging/statistics & numerical data , Positron-Emission Tomography/statistics & numerical data , Adult , Aged , Aged, 80 and over , Algorithms , Aniline Compounds , Data Interpretation, Statistical , Female , Fluorodeoxyglucose F18 , Functional Laterality/physiology , Humans , Male , Middle Aged , Quality Control , Radiopharmaceuticals , ThiazolesABSTRACT
CT colonography (CTC) is also referred to as virtual colonoscopy and is being used with increasing frequency in radiological practice. While there are still no generally accepted, clear-cut indications for its use in mass colorectal cancer screening, there is evidence that this investigation is useful in patients in whom colonoscopy has not been successful or who have known stenotic lesions in the colon. Recent results of significant comparative studies of CTC and conventional colonoscopy will have some influence on the future place of CTC in screening for cancer of the bowel; they show the great potential of CT-aided bowel examination.
Subject(s)
Colonic Neoplasms/diagnostic imaging , Colonic Polyps/diagnostic imaging , Colonography, Computed Tomographic , Mass Screening , Colonic Diseases/diagnostic imaging , Colonic Diseases/pathology , Colonic Neoplasms/pathology , Colonic Polyps/pathology , Colonoscopy , Crohn Disease/diagnostic imaging , Crohn Disease/pathology , Diagnosis, Differential , Humans , Intestinal Obstruction/diagnostic imaging , Intestinal Obstruction/pathology , Neoplasm Staging , Patient Acceptance of Health Care , Radiation Dosage , Sensitivity and SpecificityABSTRACT
Input functions required for positron emission tomography (PET) tracer kinetic modeling are often obtained from arterial blood. In some situations, using short-lived radiotracers, e.g. [(15)O]water, rapid sample handling is required. A method used at several facilities is to pump blood through a detector system at a constant rate. We investigate the suitability of a commercial radiochromatography module (IN/US Posi-RAM) for this new use. The Posi-RAM consists of two 2.5 cm (length) x 2.5 cm (diameter) cylindrical bismuth germanate (BGO) detectors that can operate in coincidence mode. Arterial blood is transported through the system via a length of tubing with flow rate controlled by a peristalsis pump. A custom-counting loop and support frame were designed for the Posi-RAM for PET studies. System sensitivity was determined to be 1.1 x 10(4) cps/(MBq ml(-1)). Dead time as a function of count-rate was found to be less than 1% for concentrations below 3.5 MBq ml(-1), a range encompassing all human-study values. In a human study, the performance of the device was found to be similar to that of the facility's current blood monitor (Siemens Fluid Monitor). We conclude that the Posi-RAM has the necessary sensitivity and count-rate capabilities to be used as a real-time blood activity monitor.
Subject(s)
Arteries/metabolism , Blood Chemical Analysis/instrumentation , Blood/diagnostic imaging , Chromatography/instrumentation , Positron-Emission Tomography/instrumentation , Radiometry/instrumentation , Radiopharmaceuticals/blood , Signal Processing, Computer-Assisted/instrumentation , Blood Chemical Analysis/methods , Chromatography/methods , Equipment Design , Equipment Failure Analysis , Humans , Radiochemistry/instrumentation , Radiochemistry/methods , Radiometry/methods , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
Computer-aided detection (CAD) algorithms help to detect colonic polyps at CT colonography (CTC). The purpose of this study was to evaluate the accuracy of CAD versus an expert reader in CTC. One hundred forty individuals (67 men, 73 women; mean age, 59 years) underwent screening 64-MDCT colonography after full cathartic bowel cleansing without fecal tagging. One expert reader interpreted supine and prone scans using a 3D workstation with integrated CAD used as "second reader." The system's sensitivity for the detection of polyps, the number of false-positive findings, and its running time were evaluated. Polyps were classified as small (< or =5 mm), medium (6-9 mm), and large (> or =10 mm). A total of 118 polyps (small, 85; medium, 19; large, 14) were found in 56 patients. CAD detected 72 polyps (61%) with an average of 2.2 false-positives. Sensitivity was 51% (43/85) for small, 90% (17/19) for medium, and 86% (12/14) for large polyps. For all polyps, per-patient sensitivity was 89% (50/56) for the radiologist and 73% (41/56) for CAD. For large and medium polyps, per-patient sensitivity was 100% for the radiologist, and 96% for CAD. In conclusion, CAD shows high sensitivity in the detection of clinically significant polyps with acceptable false-positive rates.
Subject(s)
Algorithms , Clinical Competence , Colonic Polyps/diagnostic imaging , Colonography, Computed Tomographic , Diagnosis, Computer-Assisted , Aged , Female , Humans , Male , Middle Aged , Reproducibility of ResultsABSTRACT
BACKGROUND: With the depiction of pulmonary arteries, coronary arteries, and the aorta, CT angiography of the chest offers a comprehensive diagnostic work-up of unclear chest pain. The aim of this study was to assess the diagnostic accuracy of dual-source CT in this patient group. MATERIALS AND METHODS: A total of 47 patients suffering from unclear chest pain were examined with a Siemens Somatom Definition. Volume and flow of contrast media (Ultravist, Schering) were adapted to the body weight. The examinations were evaluated with regard to image quality and contrast opacification and to the diagnostic accuracy with reference to the final clinical diagnosis. RESULTS: Adequate contrast opacification was achieved in all examinations. The depiction of the coronary arteries was diagnostic in all cases. The cause of chest pain could be identified in 41 cases. Among the diagnoses were coronary and myocardial pathologies, valvular disease, aortic aneurysms and dissections, pulmonary embolism, and pneumonic consolidation. CONCLUSION: DSCT angiography of the chest offers a very good image quality even at high heart rates so that a high diagnostic accuracy is achieved in patients with acute chest pain.
Subject(s)
Chest Pain/diagnostic imaging , Coronary Artery Disease/diagnostic imaging , Heart Valve Diseases/diagnostic imaging , Myocardial Infarction/diagnostic imaging , Pulmonary Embolism/diagnostic imaging , Tomography, X-Ray Computed/methods , Aged , Chest Pain/etiology , Coronary Artery Disease/complications , Diagnosis, Differential , Female , Heart Valve Diseases/complications , Humans , Male , Myocardial Infarction/complications , Pulmonary Embolism/complications , Radiographic Image Enhancement/methodsABSTRACT
In a newly developed dual-source computed tomography system (DSCT) the relation of heart rate and image quality and the possible advantages of the system's superior temporal resolution in the evaluation of left ventricular parameters as compared to results of cardiac magnetic resonance imaging (MRI) were assessed. Coronary CT angiography was performed using a DSCT (Somatom Defintion, Siemens Medical Solutions, Forchheim, Germany) in 21 patients (mean age 62+/-8; 15 male, 6 female). Image quality of the coronary arteries, the heart valves, and the left ventricular myocardium was assessed using a three-point grading scale. Ten of these patients also underwent cardiac MRI for the assessment of left ventricular function, using a SSFP (steady-state free precession) sequence. Left ventricular ejection fractions (LV-EF), the end-systolic volumes (ESV), and the end-diastolic volumes (EDV) were measured employing MRI and DSCT datasets. The image quality ratings for the coronary arteries at the optimal reconstruction interval were diagnostic even in patients with high heart rates (1.42+/-0.49). Analysis of global LV function using DSCT quantified from CTA datasets showed a good correlation with results of cardiac MRI [EF: r=0.75 (p=0.01); ESV: r=0.72 (p=0.19); EDV: r=0.71 (p=0.02)]. The dual-source CT system offers robust image quality of the coronary arteries, independent of the heart rate, and provides combined diagnostic imaging of coronary arteries, the heart valves, the myocardium, and the global left ventricular function.
Subject(s)
Coronary Angiography/methods , Coronary Artery Disease/diagnostic imaging , Radiographic Image Enhancement/methods , Tomography, X-Ray Computed/methods , Ventricular Dysfunction, Left/diagnostic imaging , Coronary Artery Disease/complications , Female , Humans , Male , Middle Aged , Reproducibility of Results , Sensitivity and Specificity , Ventricular Dysfunction, Left/etiologyABSTRACT
PURPOSE: The aim of this study was to evaluate the clinical potential of dual-source computed tomography (DSCT) in pre- and postsurgical diagnostics in the field of cardiac surgery. MATERIAL AND METHODS: A total of 20 patients underwent DSCT of the heart. This CT system with two rotating X-ray tubes (Somatom Definition, Siemens Medical Solutions, Forchheim, Germany) achieves a temporal resolution of 83 ms and a spatial resolution of 0.4 x 0.4 x 0.4 mm. The patient cohort consisted of two subgroups. In a group of ten patients with known coronary artery disease (CAD), scheduled for bypass surgery (i.e., high pretest likelihood for having significant CAD), the results of DSCT coronary angiography (CTA) and invasive quantitative catheter angiography (QCA) were compared to assess the diagnostic accuracy of DSCT in the detection of significant coronary artery stenoses (>50%). In a second group of ten patients with previous aortic valve replacement (homografts), the valve opening area of the transplanted aortic valve graft was measured by DSCT and compared with echocardiography as a standard of reference to exclude postsurgical restenosis of the valve. RESULTS: Of 150 coronary artery segments depicted by CT, 144 (96%) were classified as "assessable." A significant CAD was known in all patients, and altogether 43 significant stenoses were present according to the results of QCA. Blinded to these results, DSCTA reached a sensitivity and specificity of 95% (41/43) and 93% (103/111), yielding a positive and negative predictive value (PPV, NPV) of 79% (31/39) and 98% (103/105), respectively. In patients with aortic valve homografts, all DSCT datasets were considered as being of diagnostic image quality concerning valve depiction. The planimetric evaluation of the CT data as compared to results of echocardiography showed a significant correlation of the results (r=0.64, p=0.0467). A high-grade valve stenosis (opening area <1.0 cm(2)) could be correctly excluded by DSCT in all patients. CONCLUSIONS: Dual-source CT shows great diagnostic potential in patients before or after cardiac surgery. DSCT provides a high diagnostic accuracy for detection of coronary artery stenosis before bypass surgery. DSCT also proved to be accurate in the assessment of patients who received aortic valve replacement.
Subject(s)
Cardiac Surgical Procedures/methods , Cardiovascular Diseases/diagnostic imaging , Cardiovascular Diseases/surgery , Surgery, Computer-Assisted/methods , Tomography, X-Ray Computed/methods , Aged , Female , Humans , Male , Postoperative Care/methods , Preoperative Care/methods , Prognosis , Treatment OutcomeABSTRACT
OBJECTIVE: The purpose of our study was to evaluate the dose reduction potential of combined online (x- and y-axes) and topogram-based (l) X-ray tube current modulation in CT colonography in a screening population. MATERIALS AND METHODS: Eighty asymptomatic individuals underwent CT colonography screening for colon polyps. A 16-MDCT scanner (Somatom Sensation 16) was used. Forty patients were examined at 120 kVp and 120 effective mAs (supine) and 40 effective mAs (prone) using online x- and y-axis tube current modulation. Another 40 patients were scanned using combined x-, y-, and z-axis tube current modulation. Individual patient radiation exposure was determined using the dose-length product. Image noise was determined by Hounsfield unit measurements in the colonic lumen at four anatomic levels. Image quality was rated on a 5-point confidence scale by two independent reviewers. The unpaired Student's t test (for radiation dose, image noise) and Wilcoxon's test (for image quality) were used to test for statistically significant differences between these values. RESULTS: Radiation dose was significantly lower in the patient group scanned with x-, y-, and z-axis tube current modulation than in the group scanned with x- and y-axis tube current modulation (supine: 4.24 vs 6.50 mSv, p < 0.0001; prone: 1.61 vs 2.38 mSv, p < 0.0001). Radiation dose was reduced by 35% (supine) and 33% (prone). No statistically significant difference was seen in overall image noise (supine: 15.9 vs 16.3 H, p = 0.13; prone: 23.5 vs 24.8 H, p = 0.44) or image quality (supine: 4.6 vs 4.5, p = 0.62; prone: 3.5 vs 3.6, p = 0.54). CONCLUSION: Combined x-, y-, and z-axis tube current modulation leads to a significant reduction of radiation exposure in CT colonography without loss of image quality.
Subject(s)
Colonic Polyps/diagnostic imaging , Colonography, Computed Tomographic/methods , Aged , Female , Humans , Male , Mass Screening , Middle Aged , Radiometry , Sensitivity and Specificity , SoftwareABSTRACT
Ring structures fabricated from HgTe/HgCdTe quantum wells have been used to study Aharonov-Bohm type conductance oscillations as a function of Rashba spin-orbit splitting strength. We observe nonmonotonic phase changes indicating that an additional phase factor modifies the electron wave function. We associate these observations with the Aharonov-Casher effect. This is confirmed by comparison with numerical calculations of the magnetoconductance for a multichannel ring structure within the Landauer-Büttiker formalism.
ABSTRACT
The benefit of pulsatile lavage on cement penetration in femoral cancellous bone is well known. The aim of this study was to determine the influence of different jet-lavage systems on cement penetration in a standardized cadaver study. Four different jet-lavage systems were compared (right vs left) in 30 paired human femora. After broaching, the femoral canal was lavaged with 1 l saline. The specimens were embedded in plastic pots, bone cement was applied in a retrograde manner and cement was pressurized using a standard pressure protocol with a constant force of 3,000 N. Horizontal sections were obtained at predefined levels using an automatic saw. Microradiographs were taken and analysed using image analysis to assess the extent of cement penetration. There were no significant differences in cement penetration into cancellous bone using the different jet-lavage systems. This technique is of great importance for obtaining a good interdigitation with cancellous bone. The different jet-lavage systems investigated in our study, however, seemed to be equally effective.
Subject(s)
Bone Cements/chemistry , Femur/chemistry , Therapeutic Irrigation/methods , Absorption , Humans , In Vitro Techniques , Materials Testing , Pressure , Sodium Chloride/chemistryABSTRACT
Multifocal metastatic spread of solid tumours is often a diagnostic and therapeutic challenge. Those patients often cannot undergo curative surgery. Since several years, various types of interventional tumour therapy have been introduced, which may represent a promising option in those cases. In some cases morphological imaging is not able to assess the viability of a previously treated lesion. The combination of computed tomography and positron emission tomography has the potential to ease planning and guiding of interventional procedures and to improve postinterventional control. Due to its higher sensitivity and specificity, PET/CT enables for a more precise selection of patients for interventional tumor therapy. The success of a particular therapy could be assessed with greater accuracy using PET/CT as compared with the separate modalities. PET/CT was also able to improve planning and guiding interventional therapy. As of yet, no data are available concerning the success rate and long-term survival of PET/CT associated interventional procedures.
Subject(s)
Image Enhancement/instrumentation , Image Processing, Computer-Assisted/instrumentation , Neoplasms/therapy , Positron-Emission Tomography/instrumentation , Radiology, Interventional/instrumentation , Tomography, X-Ray Computed/instrumentation , Adult , Aged , Aged, 80 and over , Algorithms , Equipment Design , Female , Fluorodeoxyglucose F18 , Humans , Male , Middle Aged , Neoplasm Staging , Neoplasms/diagnosis , Neoplasms/pathology , Palliative Care , Sensitivity and Specificity , Therapy, Computer-Assisted/instrumentationABSTRACT
Electron beam tomography (EBT) has been scientifically evaluated to a much lesser degree for non-cardiac indications than for cardiac purposes. Therefore, four groups of investigators in Berlin (2), Mannheim and Munchen, which were supported by the Deutsche Forschungsgemeinschaft (DFG), included applications outside the heart in their evaluation of EBT technology. EBT has proven useful to look for pulmonary embolism and to assess other vessels (aorta, aortic branches, and intracranial arteries). Imaging of the lung parenchyma benefits from its intrinsic high contrast and from the fast data acquisition of EBT. Limited photon efficiency, higher radiation exposure, increased noise levels and other artifacts, however, markedly reduce the value of EBT for imaging of low contrast objects compared to conventional spiral CT and multislice CT (MSCT), compromising, in particular, the morphologic depiction of parenchymal abdominal organs and the brain. Consequently, scientific studies to further evaluate EBT for scanning of the brain and parenchymal abdominal organs were not pursued. Radiation exposure for non-cardiac EBT studies is up to three times higher than that for respective spiral CT studies, and in children EBT can only be advocated in select cases. Radiation exposure for the various prospectively triggered cardiac examination protocols of EBT is lower than that for conventional coronary angiography. Radiation exposure in cardiac multislice CT exceeds severalfold that of EBT, but the dose efficiency of EBT and MSCT are similar due to higher spatial resolution and less image noise of MSCT. In addition, modifications of MSCT (ECG pulsing) can further reduce radiation exposure to the level of EBT. Technical improvements of the EBT successor scanner "e-Speed" enable faster data acquisition at higher spatial resolution. Within comparative studies, the "e-Speed" will have to prove its value and competitiveness, particularly in comparison with multislice CT. After profound scientific assessment in a multicenter evaluation supported by the Deutsche Forschungsgemeinschaft (DFG) and regardless of the specific suitability of electron beam tomography for various cardiac and some non-cardiac indications, the investigators unanimously find the electron beam tomograph Evolution C150 XP not suitable as a whole body CT scanner.
Subject(s)
Radiography, Abdominal , Radiography, Thoracic , Tomography, Spiral Computed , Tomography, X-Ray Computed , Age Factors , Aged , Biomedical Research , Child , Coronary Angiography , Female , Germany , Heart Diseases/diagnostic imaging , Humans , Infant, Newborn , Male , Multicenter Studies as Topic , Pulmonary Embolism/diagnostic imaging , Radiation Dosage , Tomography, Spiral Computed/adverse effects , Tomography, Spiral Computed/methods , Tomography, X-Ray Computed/adverse effects , Tomography, X-Ray Computed/methods , Vascular Diseases/diagnostic imagingABSTRACT
Since the introduction of last generation multislice MSCT systems and the development of simultaneous electrocardiographic-tracing image acquisition and retrospective reconstruction techniques into clinical routine, cardiac MSCT has been considered a very useful non-invasive technique for the study of cardiac pathology in the daily clinical practice. One of the main clinical applications of this diagnostic technique is the evaluation of the coronary arteries including detection and quantification of coronary calcium, multislice CT coronary angiography (anatomy, anatomical variants and anomalies of the origin and course), the angiographic evaluation of the patency of aortocoronary by-pass grafts and coronary stents, and plaque characterization. The new reconstruction and postprocessing programs allow to obtain, in addition, parameters of myocardial morphology and contraction and cardiac function. Other clinical applications include the characterization of cardiac masses and the evaluation of the pericardium.