Comparison of contrast-enhanced modified T1-weighted 3D TSE black-blood and 3D MP-RAGE sequences for the detection of cerebral metastases and brain tumours.

OBJECTIVES: To compare a modified T1-weighted 3D TSE black-blood sequence with sub-millimetre resolution (T1-mVISTA) with a magnetization-prepared rapid gradient echo (MP-RAGE) sequence for the diagnosis of cerebral malignomas. METHODS: Forty-six patients with known or suspected intracranial tumours and 15 control patients were included in this retrospective study. All patients underwent T1-mVISTA (0.75-mm isotropic resolution, 4:43 min) and MP-RAGE (0.8-mm isotropic resolution, 4:46 minutes) at 3-Tesla in random order after application of contrast agent. Two experienced radiologists determined the number of lesions. Maximum diameter, diagnostic confidence (DC), visual assessment of contrast enhancement (VCE) and CNRlesion/parenchyma were assessed for each lesion. RESULTS: Significantly more lesions were detected with T1-mVISTA compared to the MP-RAGE (61 vs. 36; p < 0.05). Further, DC and VCE was rated significantly higher in the T1-mVISTA (p < 0.05 and p < 0.001). Mean CNRlesion/parenchyma was twofold higher for T1-mVISTA (24.2 ± 17.5 vs. 12.7 ± 11.5, p < 0.001). The 25 lesions detected only in T1-mVISTA were significantly smaller than those detected in both sequences (4.3 ± 3.7 mm vs. 11.3 ± 10.7 mm; p < 0.01). CONCLUSIONS: T1-mVISTA increases the contrast of lesions significantly compared to MP-RAGE and might therefore improve detection rates of small lesions in early stages of disease. KEY POINTS: • T1-mVISTA leads to significantly higher contrast-to-noise ratios of cerebral malignomas. • T1-mVISTA detects significantly more metastatic lesions compared to 3D-MPRAGE. • Lesions detected only by T1-mVISTA are smaller than those detected in both sequences. • Diagnostic confidence is significantly higher for lesions detected by T1-mVISTA. • Application of T1-mVISTA might be of high relevance in early stages of disease.

Cystic fibrosis in adults: short-term and long-term reproducibility of the Brody score for lung morphology in low-dose MDCT scans.

PURPOSE: The semi-quantitative Brody score measures the severity of cystic fibrosis (CF)-related lung disease. We investigated the short-term (28 - 60 days) and long-term (2 - 7 years) intra- and inter-observer reproducibility of the Brody score in low-dose multidetector row computed tomography examinations performed in inspiration (LDCTs) of adult CF patients. MATERIALS AND METHODS: Composite Brody scores and respective underlying bronchiectasis, mucus plugging, peribronchial thickening, parenchymal opacity, and hyperinflation subscores were evaluated twice (time interval, 1 - 84 months) by each of 3 independent radiologists (1 - 20 years of professional diagnostic radiology experience) in LDCTs (4 - 64 rows, 120 KVp, 10 - 15  mAs/slice, CTDIw approx. 1.0  mGy, effective dose approx. 0.5  mSv) of 15 adult patients with CF-related lung disease (8 female, 7 male, age, 18 - 50 years, mean, 33 years). RESULTS: The average reproducibility of the Brody score was within +/-7 % (range, 2 - 30 %) between radiologists, and +/-6 % (3 - 12 %) within radiologists (short-term, 28 - 60 days, 4 %, 0 - 12 %, long-term, 2 - 7 years, 12 %, 1 - 36 %). For the different subscores, the reproducibility was within +/-25 % (15 - 41 %) between radiologists and +/-23 % (12 - 46 %) within radiologists. CONCLUSION: The Brody score shows high average inter-observer reproducibility in LDCTs of adult CF patients. The Brody score also demonstrates high average intra-observer reproducibility if subsequent assessments are made within 28 - 61 days. With time intervals of 2 - 7 years between subsequent evaluations, however, intra-observer reproducibility decreases. Respective subscores each demonstrate lower intra- and inter-observer reproducibility than does the composite Brody score.

Time-of-flight angiography: a viable alternative to contrast-enhanced MR angiography and fat-suppressed T1w images for the diagnosis of cervical artery dissection?

OBJECTIVES: To compare the use of an unenhanced high-resolution time-of-flight MR angiography sequence (Hr-TOF MRA) with fat-suppressed axial/coronal T1-weighted images and contrast-enhanced angiography (standard MRI) for the diagnosis of cervical artery dissection (cDISS). METHODS: Twenty consecutive patients (9 women, 11 men, aged 24-66 years) with proven cDISS on standard MRI underwent Hr-TOF MRA at 3.0 T using dedicated surface coils. Sensitivity (SE), specificity (SP), positive and negative predictive values (PPV, NPV), Cohen's kappa (к) and accuracy of Hr-TOF MRA were calculated using the standard protocol as the gold standard. Image quality and diagnostic confidence were assessed on a four-point scale. RESULTS: Image quality was rated better for standard MRI (P = 0.02), whereas diagnostic confidence did not differ significantly (P = 0.27). There was good agreement between Hr-TOF images and the standard protocol for the presence/absence of cDISS, with к = 0.95 for reader 1 and к = 0.89 for reader 2 (P < 0.001). This resulted in SE, SP, PPV, NPV and accuracy of 97 %, 98 %, 97 %, 98 % and 97 % for reader 1 and 93 %, 96 %, 93 %, 96 % and 95 % for reader 2. CONCLUSIONS: Hr-TOF MRA can be used to diagnose cDISS with excellent agreement compared with the standard protocol. This might be useful in patients with renal insufficiency or if contrast-enhanced MR angiography is of insufficient image quality. KEY POINTS: • New magnetic resonance angiography sequences are increasingly used for vertebral artery assessment. • A high-resolution time-of-flight sequence allows the diagnosis of cervical artery dissection. • This technique allows the diagnosis without intravenous contrast medium. • It could help in renal insufficiency or when contrast-enhanced MRA fails.

Modern nuclear medicine evaluation of neuroblastoma.

The neuroblastoma is an embryonic tumor of the peripheral sympathetic nervous system, and is metastatic or otherwise high risk for relapse in nearly 50% of cases, with a long-term survival of <40%. Therefore, exact staging with radiological and nuclear medicine imaging methods is crucial for finding the adequate therapeutic choice. The tumor cells express the norepinephrine transporter, which makes metaiodobenzylguanidine (MIBG), an analogue of norepinephrine, an ideal tumor specific agent for imaging. On the other hand, MIBG imaging has several disadvantages as limited spatial resolution, limited sensitivity in small lesions, need for two or even more acquisition sessions, and a delay between the start of the examination and result. Most of these limitations can be overcome with positron emission tomography (PET) using different radiotracers. Furthermore, MIBG imaging is not sufficient for operative or biopsy planning. With this regard, a combination with morphological imaging methods is indispensable. This article will discuss the therapeutic strategy for primary and follow-up diagnosis in neuroblastoma using different nuclear medicine and radiological imaging methods as well as multimodality imaging.

[Cross-sectional imaging in dentomaxillofacial diagnostics: dose comparison of dental MSCT and NewTom 9000 DVT]. / Schnittbildverfahren zur dentomaxillofazialen diagnostik: dosisvergleich von dental-MSCT und NewTom 9000 DVT.

PURPOSE: For nonsuperimposed and three-dimensional imaging of jaws and teeth, multislice computer tomography (MSCT) can be performed, or alternatively digital volume tomography as a cone beam technique can be applied. The radiation dose of both procedures should be evaluated with different methods of dose assessment. MATERIALS AND METHODS: A 4-row MSCT (Volume Zoom Siemens) and a cone beam CT (NewTom QR-DVT 9000) were compared regarding the radiation exposure of the patient during a dental examination. Organ dose and effective dose were estimated by thermoluminescence dosimetry (TLD) using an Alderson-Rando phantom for both devices. In addition the effective dose of MSCT was calculated from the CTDIvol-value at scanner display and by CT-Expo program. RESULTS: The effective dose of MSCT was 0.33 mSv for women (w) and 0.32 mSv for men (m) measured with TLD in the Alderson-Rando phantom, 0.39 / 0.35 mSv (w/m) by CTDI calculation and 0.39 / 0.33 mSv by CT-Expo program. The effective dose of NewTom QR-DVT 9000 from TLD measurement was 0.095 / 0.093 mSv (w/m). CONCLUSION: The radiation exposure of a typical dental examination with a NewTom cone beam DVT is about one third of the MSCT dose. Both techniques, however, moderate patient doses. Dosimetry methods as routinely used for MSCT cannot be applied to cone beam DVT.

[Chronic pulmonary embolism--radiological imaging and differential diagnosis]. / Chronische Lungenembolie--Radiologische Bildmorphologie und Differenzialdiagnose.

In chronic pulmonary embolism branches of the pulmonary arterial tree remain partially or totally occluded. This may lead to pulmonary hypertension with the development of right ventricular hypertrophy as well as structural changes of pulmonary arteries. Imaging of chronic pulmonary embolism should prove vessel occlusions (pulmonary angiography, MSCT, MRI) and reduction of regional lung perfusion (lung scanning, MSCT, MRI). According to current guidelines ventilation-perfusion lung scanning and pulmonary angiography are still recommended as the methods of choice. MSCT and MRI provide technical alternatives which are helpful in differential diagnosis versus other types of pulmonary hypertension. In spite of medical and surgical measures (in rare cases pulmonary thromboendarterectomy) the prognosis of chronic pulmonary embolism remains unfavourable.

Beam hardening artefacts occur in dental implant scans with the NewTom cone beam CT but not with the dental 4-row multidetector CT.

OBJECTIVES: The aim of this study was to examine beam hardening artefacts of the NewTom 9000 cone-beam computed tomography (CBCT) device compared with the Philips MX 8000 (4-row multidetector CT (MDCT)). METHODS: We modified a SawBone skull to become a standardized model for our study. The skull was used for scans with the NewTom 9000 CBCT device and a standard dental multi-detector CT (MDCT) at a comparable reconstruction resolution with a standard Straumann ITI 4.1 mm implant in four implant positions in the maxilla (first permanent premolar in the right maxilla region, second permanent molar in the right maxilla region, first permanent premolar in the left maxilla region and second permanent molar in the left maxilla region). Results were compared with construction data of the dental implant. An image quality assessment of the images from both devices was performed with four experienced physicians and statistically analysed with the two-tailed Wilcoxon test. RESULTS: Scans with the NewTom 9000 CBCT showed strong beam hardening artefacts in the form of a radiation beam shadow in all reconstructions compared with the MDCT. These imaging artefacts became stronger with greater distance from the centre of the scanned volume. These differences in the imaging quality were proved as significant in a quality evaluation by four experienced physicians (P<0.05). CONCLUSIONS: Visual spatial resolution of the NewTom 9000 CBCT was less accurate than the Philips MX 8000 MDCT in the imaging of metallic dental implants.

Multidetector CT of the kidney.

The technological development of multidetector CT offers new possibilities for better imaging of organic structures that can be used in diagnosis of the kidney. The thinner slices allow a better spatial resolution, and slice fusion allows improved contrast resolution. The isotropic voxel has been realized in the latest 64-channel scanners. The image quality of arbitrarily reconstructed planes has arrived at the image quality of the scan plane. Faster scanning allows studies in different contrast phases, which is helpful for better discrimination of benign or malignant lesions especially in the highly vascularized kidney. Different phases of contrast uptake can be differentiated (arterial, cortico-medullary, nephrographic, and excretory phase). Multidetector CT brings along the risk of increased dose due to thinner slice collimation and overranging phenomena. Indications for CT investigation of the kidney include urolithiasis, tumor diagnosis and staging, renal trauma, and vascular disease. Even in children, special indications for CT of the kidney remain in polytrauma and tumor staging. Multidetector CT of the kidney has become a very valuable tool in urology, but a careful protocol strategy is mandatory.

Dose reduction in multidetector CT of the urinary tract. Studies in a phantom model.

A novel ureter phantom was developed for investigations of image quality and dose in CT urography. The ureter phantom consisted of a water box (14 cm x 32 cm x 42 cm) with five parallel plastic tubes (diameter 2.7 mm) filled with different concentrations of contrast media (1.88-30 mg iodine/ml). CT density of the tubes and noise of the surrounding water were determined using two multidetector scanners (Philips MX8000 with four rows, Siemens Sensation 16 with 16 rows) with varying tube current-time product (15-100 mAs per slice), voltage (90 kV, 100 kV, 120 kV), pitch (0.875-1.75), and slice thickness (1 mm, 2 mm, 3.2 mm). Contrast-to-noise ratio as a parameter of image quality was correlated with dose (CTDI) and was compared with image evaluation by two radiologists. The CT densities of different concentrations of contrast media and contrast-to-noise ratio were significantly higher when low voltages (90 kV versus 120 kV, 100 kV versus 120 kV) were applied. Smaller slice thickness (1 mm versus 2 mm) did not change CT density but decreased contrast-to-noise ratio due to increased noise. Contrast phantom studies showed favourable effects of low tube voltage on image quality in the low dose range. This may facilitate substantial dose reduction in CT urography.

[Low-dose spiral CT of the lung in the follow-up of non-malignant lung disease]. / Niedrigdosis-Spiral-CT des Thorax in der Verlaufskontrolle nichtmaligner Lungenerkrankungen.

PURPOSE: To assess image quality of chest CT with an 80 to 90 percent dose reduction in follow-up studies of patients with lung disease, dose and image quality of a low-dose protocol was investigated. MATERIALS AND METHODS: A follow-up low-dose CT (ND-CT, 120 kV, 10 mAs/slice, 3 mm slice thickness) was performed on 35 patients with non-malignant lung disease and compared with the initial standard dose CT (= SD-CT, 100 mAs/slice, 3 or 5 mm slice thickness). The dose was measured by thermo-luminescence in an Alderson phantom. Image quality was assessed by four independent radiologists in six perihilar, central and peripheral lung regions using a 4-point-scale ("very good", "good", "moderate", and "poor"). RESULTS: Effective dose was 0.5 mSv for ND-CT and 4.0 - 5.0 mSv for SD-CT. The ratings "very good"/"good" were given in the perihilar regions in ND-CT 97.5 % versus SD-CT 99.3 % (n. s.), in the central regions in ND-CT 96.4 % versus SD-CT 94.6 % (n. s.), and in the peripheral regions in ND-CT 70.0 % versus SD-CT 88.2 % (p < 0.01). CONCLUSION: Follow-up CT of pulmonary structures in patients with chronic lung disease can be performed with substantial dose reduction. A decrease of image quality may result in peripheral lung regions.

Assessment of a theoretical formalism for dose estimation in CT: an anthropomorphic phantom study.

Dose assessment in computed tomography (CT) is challenging due to the vast variety of CT scanners and imaging protocols in use. In the present study, the accurateness of a theoretical formalism implemented in the PC program CT-EXPO for dose calculation was evaluated by means of phantom measurements. Phantom measurements were performed with four 1-slice, four 4-slice and two 16-slice spiral CT scanners. Firstly, scanner-specific nCTDIw values were measured and compared with the corresponding standard values used for dose calculation. Secondly, effective doses were determined for three CT scans (head, chest and pelvis) performed at each of the ten installations from readings of thermoluminescent dosimeters distributed inside an anthropomorphic Alderson phantom and compared with the corresponding dose values computed with CT-EXPO. Differences between standard and individually measured nCTDIw values were less than 16%. Statistical analysis yielded a highly significant correlation (P < 0.001) between calculated and measured effective doses. The systematic and random uncertainty of the dose values calculated using standard nCTDIw values was about -9 and +/- 11%, respectively. The phantom measurements and model calculations were carried out for a variety of CT scanners and representative scan protocols validate the reliability of the dosimetric formalism considered-at least for patients with a standard body size and a tube voltage of 120 kV selected for the majority of CT scans performed in our study.

[Spiral CT of the abdomen: weight-adjusted dose reduction]. / Spiral-CT des Abdomens: Gewichtsadaptierte Dosisreduktion.

AIM OF THE STUDY: The influence of weight-adjusted current application in spiral CT of the abdomen on noise was investigated in a clinical study. PATIENTS AND METHODS: In 77 routine abdominal CT investigations (120 kV, 8 mm, pitch 1.5) the patients were divided into three body-weight groups A (< 60 kg), B (60-80 kg), and C (> 80 kg). The tube current was randomized prospectively in low weight group A, either 125 mA or 150 mA, in middle and high weight groups B and C, 150, 175 or 200 mA, with a tube revolution time of one second. The noise was measured in liver, skeleton muscle, fat tissue, and bladder content for evaluation of image quality. RESULTS: The bodyweight groups differ significantly in noise, e.g., in the liver (150 mA): group A: 15.8 HU, group B: 18.9 HU, group C: 21.5 HU. The increase of tube current (150, 175, 200 mA) within a body weight group resulted in a minor decrease of noise (18.9 HU, 17.6 HU, 17.5 HU, respectively, in group B). There is a good correlation of noise with body weight, body mass index and body cross section, but not with body size. CONCLUSION: A body weight adjusted reduction of tube current is possible without an increase of noise.

Dose and image quality of electron-beam CT compared with spiral CT.

RATIONALE AND OBJECTIVES: To examine dose and image quality of electron-beam CT (EBCT) with continuous volume scan versus spiral CT. METHODS: An EBCT scanner was compared with a spiral CT (SCT) scanner. Three phantoms were used to measure low-contrast resolution, high-contrast resolution, slice width, and dose. RESULTS: The EBCT scans showed 30% lower high-contrast resolution for most settings. The dose was comparable to that of spiral CT with 3 mm collimation and 76%/106% higher with EBCT for 1.5 mm/6 mm collimation. Low-contrast resolution was comparable to that of spiral CT using 3 mm collimation, slightly worse for 1.5 mm, and bad for 6 mm EBCT collimation (four times higher dose to reach comparable contrast-to-noise ratio). CONCLUSIONS: Significant restrictions were found using EBCT with continuous volume scan. The authors found that 3 mm collimation can yield acceptable high-contrast resolution and good low-contrast resolution compared with spiral CT. The use of 6 mm or 1.5 mm collimation needs to be restricted to selected cases.

Radiation dose and image quality in spiral computed tomography: multicentre evaluation at six institutions.

The purpose of this study was to evaluate the correlation of radiation dose with image quality in spiral CT. Seven clinical protocols were measured in six different radiological departments provided with four different types of high specification spiral CT scanners. Central and surface absorbed doses were measured in acrylic. The practical CT dose index (PCTDI) was calculated for seven clinical examination protocols and one standardized protocol using identical parameters on four different spiral CT scanners with a dedicated ionization chamber inserted into PMMA phantoms. For low contrast measurements, a cylindrical three-dimensional (3D) phantom (different sized spheres of defined contrast) was used. Image noise was measured with a cylindrical water phantom and high contrast resolution with a Perspex hole phantom. Image quality phantoms were scanned using the parameters of the clinical protocols. Images were randomized, blinded and read by six radiologists (one from each institution). PCTDI values for four different scanners varied up to a factor between 1.5 (centre) and 2.2 (surface) for the standardized protocol. A greater degree of variation was observed for seven clinical examination protocols of the six radiological departments. For example, PCTDI varied up to a factor between 1.7 (cerebrum protocol) and 8.3 (abdomen paediatric protocol). Low contrast resolution correlates closely with dose. An improvement in detection from 8 mm to 4 mm sized spheres needs approximately a ten-fold increase in dose. Noise shows a moderate correlation with PCTDI. High contrast resolution of clinical protocols is independent of PCTDI within a certain range. Differences in modern CT scanner technology seem to be of less importance for radiation exposure than selection of protocol parameters in different radiological institutes. Future discussion on guidelines regarding optimal (patient adapted) tube current for clinical protocols is desirable.

[Dosimetry in conventional and spiral CT in 8 spiral CT scanners of the latest generation]. / Dosismessung für Einzelschicht- und Spiralmodus bei 8 Spiral-CT-Scannern der neuesten Generation.

PURPOSE: Measurement of scanner-dependent differences in PCTDI for conventional and spiral CT and evaluation of PCTDI/100 mAs in eight spiral CT scanners of the latest generation. METHODS: Central PCTDI was evaluated in a PMMA phantom for different scan lengths of conventional and spiral CT in four scanners. Central and peripheral PCTDI/100 mAs, average dose and the quotient between peripheral and central PCTDI/100 mAs were measured with a dedicated 10 cm ionisation chamber positioned within a PMMA phantom using the parameters of a standardised liver protocol and a high-resolution inner ear protocol for eight spiral CT scanners. RESULTS: Depending on scanner type and scan length PCTDI for the spiral mode is in a range between 11.3% higher and 4.3% lower than that for the conventional mode. PCTDI/100 mAs varies considerably between different CT scanners. For the standardised liver protocol PCTDI/100 mAs varies up to a factor of 2, for the inner ear protocol up to a factor of 4. CONCLUSION: Even in comparable modern CT scanners there are considerable protocol and scanner-dependent differences in PCTDI/100 mAs. The values for his own scanner should be known to each CT user so that he can develop a dose-optimised, patient and problem-orientated examination strategy.

[Performance of electron-beam CT: continuous-volume-scan compared to spiral CT]. / Abbildungseigenschaften der Elektronenstrahl-CT. Continuous-Volume-Scan im Vergleich zur Spiral-CT.

To compare patient dose and image quality of electron-beam-CT vs. spiral-CT by means of phantom measurements. An EBCT scanner (C-150 XP) and a spiral-CT scanner (GE HiSpeed Advantage) were used to scan three different phantoms. Administered dose, high contrast (HC) resolution, low contrast (LC) lesion detectability and the width of the radiation beams were measured. EBCT showed 25-35% lower HC resolution in comparison to spiral-CT. LC lesion detectability showed equivalent results for S/N vs. patient dose using 3 mm collimation with EBCT and spiral-CT, whereas spiral-CT was superior for 1.5 and 6 mm collimation. Dose measurements revealed a 2 fold higher patient dose using EBCT with 1.5 mm or 6 mm collimation compared to spiral-CT using equivalent scan parameters. No differences were seen using 3 mm collimation. Differences were due to insufficient beamside collimation of the EBCT. The use of EBCT with 6 mm collimation should be avoided, because of impaired performance. Using 3 mm collimation, EBCT showed comparable performance like state of the art spiral-CT despite lower HC resolution.

Photodynamic therapy of vascular stenosis: results from cell culture studies on human endothelial cells.

BACKGROUND: Experimental results from human cell culture studies have shown that smooth muscle cells derived from human atherosclerotic plaques react more sensitively to photoactivated dihematoporphyrin-ester and -ether (DHE) than smooth muscle cells from human nonatherosclerotic arteries. A therapeutic concept of photodynamic therapy of vascular stenosis appears, therefore, to be promising. The prerequisite for an intravascular application is a relatively harmless application of the photosensitizing agent to the luminal lining of endothelial cells. METHODS: The effect of DHE with and without photoactivation was examined on endothelial cell cultures from human saphenous veins. The cellular uptake of DHE in relation to the serum content of the culture medium was evaluated, as well as its effect on proliferative activity, cell size, cell volume, and cellular viability. RESULTS: Intracellular uptake of DHE decreased significantly when higher serum concentrations were present in the culture medium. Incubation of cells with the photosensitizer for 9 days in the dark without light activation resulted in a significant decrease of endothelial cell proliferation only at concentrations higher than 2.5 micrograms/mL (= 2.5 mg/kg body weight for systemic application in vivo). Additional photoactivation caused no reduction of cell viability at DHE concentrations of 1 microgram/mL, but at 2.5 micrograms/mL and 5 micrograms/mL, a reduction of viable cells within 24 hours was observed in relation to the energy densities used for irradiation. CONCLUSIONS: Because smooth muscle cells from atherosclerotic plaques are, however, much more sensitive to photodynamic treatment, the concept of a photodynamic therapy of vascular stenosis may provide a good tool in the reduction of restenosis rates after recanalization of severely stenosed or even occluded arteries.

Fibrin-fibronectin compounds in human ovarian tumor ascites and their possible relation to the tumor stroma.

Covalently linked heterogeneous fibrin-fibronectin compounds were detected in ascitic fluid of 31 patients with advanced ovarian cystadenocarcinoma by means of enzyme-linked immunosorbent assay techniques, immunoaffinity chromatography, and Western blot analysis. Deposition of fibrin and fibronectin could also be demonstrated immunohistochemically in Carnoy-fixed tissue sections. Fibrin and fibronectin were found in the tumor stroma within tumor nests and more prominently in stroma surrounding the tumor nests. The association of fibrin and fibronectin was especially pronounced in the stroma surrounding the tumor islands. Fibronectin was also found to be associated with stroma cells. Areas within the tumor stroma showed superimposed staining for both fibrin and fibronectin supporting the assumption that the covalently linked fibrin-fibronectin conjugates found in ascitic fluid may stem from the provisional tumor stroma by proteolytic release.