Assessment of image quality and low-contrast detectability in abdominal CT of obese patients: comparison of a novel integrated circuit with a conventional discrete circuit detector at different tube voltages.

OBJECTIVES: To compare image quality and low-contrast detectability of an integrated circuit (IC) detector in abdominal CT of obese patients with conventional detector technology at low tube voltages. METHODS: A liver phantom with 45 lesions was placed in a water container to mimic an obese patient and examined on two different CT systems at 80, 100 and 120 kVp. The systems were equipped with either the IC or conventional detector. Image noise was measured, and the contrast-to-noise-ratio (CNR) was calculated. Low-contrast detectability was assessed independently by three radiologists. Radiation dose was estimated by the volume CT dose index (CTDIvol). RESULTS: The image noise was significantly lower, and the CNR was significantly higher with the IC detector at 80, 100 and 120 kVp, respectively (P = 0.023). The IC detector resulted in an increased lesion detection rate at 80 kVp (38.1 % vs. 17.2 %) and 100 kVp (57.0 % vs. 41.0 %). There was no difference in the detection rate between the IC detector at 100 kVp and the conventional detector at 120 kVp (57.0 % vs. 62.2 %). The CTDIvol at 80, 100 and 120 kVp measured 4.5-5.2, 7.3-7.9 and 9.8-10.2 mGy, respectively. CONCLUSIONS: The IC detector at 100 kVp resulted in similar low-contrast detectability compared to the conventional detector with a 120-kVp protocol at a radiation dose reduction of 37 %.

[Rational imaging of hepatocellular carcinoma. The challenge of multimodal diagnostic criteria]. / Rationale Schnittbildgebung des hepatozellulären Karzinoms. Die Herausforderung multimodaler Diagnosekriterien.

CLINICAL/METHODICAL ISSUE: Both computed tomography (CT) and magnetic resonance imaging (MRI) constitute the gold standard in radiological imaging of hepatocellular carcinoma (HCC). In cases of typical contrast behavior each modality as a single dynamic technique allows the diagnosis of HCC. There is still a challenge in detection of small HCCs < 2 cm, in differentiating HCC and high-grade dysplasia from other benign liver lesions as well as the evaluation of hypovascular liver lesions in the cirrhotic liver. PERFORMANCE: Nowadays, both modalities achieve high detection rates of 90-100 % for lesions > 2 cm. Regarding lesions between 1 and 2 cm there is a higher sensitivity for MRI ranging between 80 and 90 % compared to 60-75 % with CT. Besides the multimodal diagnostic criteria, MRI provides significant benefits with the use of hepatobiliary contrast. Especially in combination with diffusion- weighted imaging (DWI) increased sensitivity and diagnostic accuracy compared to CT has been described for lesions sized < 2 cm. Regarding the differentiation from other hepatic nodules in the cirrhotic liver there is strong evidence that the coexistence of arterial enhancement and hypointensity on hepatobiliary imaging is specific for HCC. Moreover, hypointensity on hepatobiliary imaging is associated with a high positive predictive value (PPV) of up to 100 % for the presence of high-grade dysplasia and HCC. ACHIEVEMENTS: The use of MRI including hepatobiliary imaging and DWI has to be regarded as the best non-invasive imaging modality for the detection of HCC and for the characterization of nodules in patients with liver cirrhosis. In comparison to CT there are benefits regarding detection of small lesions < 2 cm and evaluation of hypovascular liver lesions in the context of the hepatocarcinogenesis including prognostic values of premalignant lesions. PRACTICAL RECOMMENDATIONS: Both MRI and CT provide a high diagnostic performance in evaluation of HCC in liver cirrhosis. With MRI there are considerable advantages regarding the detection rate and specificity. For daily clinical routine, CT offers a fast, reliable and easy available modality with benefits for patients in reduced general state of health and restricted compliance.

Computed tomography for pulmonary embolism: assessment of a 1-year cohort and estimated cancer risk associated with diagnostic irradiation.

BACKGROUND: The principal concern of any radiation exposure in computed tomography (CT) is the induction of stochastic risks of developing a radiation-induced cancer. The results given in this manuscript will allow to (re-)calculate yield of chest CT. PURPOSE: To demonstrate a method to evaluate the lifetime attributable risk (LAR) of cancer incidence/mortality due to a single diagnostic investigation in a 1-year cohort of consecutive chest CT for suspected pulmonary embolism (PE). MATERIAL AND METHODS: A 1-year cohort of consecutive chest CT for suspected PE using a standard scan protocol was analyzed retrospectively (691 patients, 352 men, 339 women). Normalized patient-specific estimations of the radiation doses received by individual organs were correlated with age- and sex-specific mean predicted cancer incidence and age- and sex-specific predicted cancer mortality based on the BEIR VII results. Additional correlation was provided for natural occurring risks. RESULTS: LAR of cancer incidence/mortality following one chest CT was calculated for cancer of the stomach, colon, liver, lung, breast, uterus, ovaries, bladder, thyroid, and for leukemia. LAR remains very low for all age and sex categories, being highest for cancer of the lungs and breasts in 20-year-old women (0.61% and 0.4%, respectively). Summation of all cancer sites analyzed raised the cumulative relative LAR up to 2.76% in 20-year-old women. CONCLUSION: Using the method presented in this work, LAR of cancer incidence and cancer mortality for a single chest CT for PE seems very low for all age groups and both sexes, but being highest for young patients. Hence the risk for radiation-induced organ cancers must be outweighed with the potential benefit or a treatment and the potential risks of a missed and therefore untreated PE.

Transthoracic sonography for the detection of pulmonary embolism--a meta-analysis.

PURPOSE: Radiation protection is a major issue since the implementation of MSCT technology and its widespread indication for the detection of various diseases. In a European-wide trial (SECT) meta-analyses of imaging alternatives to CT have been initiated. This paper focuses on the diagnostic performance of transthoracic ultrasound (TUS) for the diagnosis of pulmonary embolism (PE) (5 studies, 652 patients). MATERIALS AND METHODS: Medical literature (from 1990 to 2006) in PubMed and EMBASE databases was searched for articles on studies that used TUS as diagnostic tests for PE. Studies were included if they reported the positive and negative rates of PE diagnoses from TUS compared with the rates of PE in CT, MRI or a combination of diagnostic tests. Two readers assessed the quality of the studies. RESULTS: Pooled sensitivity and specificity of TUS for PE were 80 % (95 % CI: 75 %, 83 %) and 93 % (95 % CI: 89 %, 96 %), respectively. CONCLUSION: In the time of MSCT, TUS is an imaging modality that is no longer part of recent diagnostic algorithms for the diagnosis of PE. Considering the increasing number of requested CT examinations and therefore increasing collective radiation dose, this meta-analysis shows that TUS is a diagnostic alternative for special clinical settings in the work-up of suspected PE that seems to have fallen into oblivion.

Comparison of Optimized 3D-SPACE and 3D-TSE Sequences at 1.5T MRCP in the Diagnosis of Choledocholithiasis.

PURPOSE: The aim of the study was to evaluate whether or not MRCP using a 3D-SPACE sequence allows for better image quality and a higher level of diagnostic confidence than a conventional 3D-TSE sequence at 1.5 T regarding the diagnosis of choledocholithiasis in a routine clinical setting. MATERIALS AND METHODS: 3D-SPACE and 3D-TSE sequences were performed in 42 consecutive patients with suspected choledocholithiasis undergoing MRCP. Evaluation of image quality and diagnostic confidence was done on the pancreaticobiliary tree which was subdivided into 10 segments. They were scored and statistically evaluated separately for visibility and diagnostic certainty by three radiologists with differing levels of experience on a five-point scale of 1 to 5 and -2 to 2, respectively. Student t-test was performed, and the interobserver agreement was also calculated. RESULTS: Image quality for each segment was significantly better for the 3D-SPACE sequence compared to the 3D-TSE sequence (4.48 ±â€Š0.94 vs. 3.98 ±â€Š1.20; 5-point scale p < 0.01). Diagnostic confidence for the reporting radiologist was also significantly better for 3D-SPACE than for 3D-TSE (1.68 ±â€Š0.56 vs. 1.46 ±â€Š0.70; 3-point scale; p < 0.01). The interobserver agreement was high in both sequences, 0.62 - 0.83 and 0.64 - 0.82, respectively. CONCLUSION: The optimized 3D-SPACE sequence allows for better image quality in 1.5 T MRCP examinations and leads to a higher diagnostic confidence for choledocholithiasis compared to the conventional 3D-TSE sequence. KEY POINTS: • 3D-SPACE allows for better image quality in 1.5 T MRCP.• This leads to a higher diagnostic confidence particularly in the periampullary region.• 3D-SPACE should be considered to substitute conventional 3D-TSE sequences in clinical routine MRCP.

Gene therapy study of cytokine-transfected xenogeneic cells (Vero-interleukin-2) in patients with metastatic solid tumors.

On the basis of compelling preclinical data in cats and dogs, we initiated a clinical gene therapy study in nine patients with advanced solid tumors using xenogeneic fibroblasts secreting human interleukin (IL)-2 (Vero-IL-2 cells). Cohorts of three successive patients with tumors accessible to computed tomography- or ultrasound-guided injection were treated repeatedly with 5 x 10(5), 5 x 10(6), or 5 x 10(7) Vero-IL-2 cells. The endpoints of the study were feasibility, toxicity, and the clinical and biological effects of this novel approach to immunotherapy of cancer. Histopathological, immunological, and molecular analyses were performed on biopsy specimens of tumors and blood samples before, during, and after treatment. Treatment was well tolerated, and toxicity consisted of transient fever in one patient and short-lived, mild itching and erythema in two others. One patient with soft-tissue sarcoma showed a reduction of >90% and >50% of the volume of two distant, noninjected metastases, lasting for 29+ and 26 months, respectively. Four other patients showed stabilization of their disease for 3-9 months; of these patients, one with melanoma developed marked vitiligo. We conclude that repeated injections of < or =5 x 10(7) Vero-IL-2 cells are feasible and safe in heavily pretreated patients with advanced solid tumors. An additional evaluation of an intratumoral application of Vero-IL-2 seems warranted.

Contrast-enhanced magnetic resonance angiography of peripheral vessels. Different contrast agent applications and sequence strategies: a review.

In this article the relation between contrast medium (CM) application and sequence parameters will be discussed with respect to clinical use of the contrast-enhanced magnetic resonance angiography (CE-MRA) in the peripheral vessel region. The adjustment of the sequence parameters, the CM application timing and the bolus geometry is necessary for an effective use of CE-MRA. Investigation protocols for several vascular regions differ mainly corresponding to varying fields of view and slab thickness. Restrictions of increasing the measurement time are expected in peripherally localized vessels if fast arteriovenous transit time occurs. The vessel contrast depends from (1) optimal CM bolus timing and (2) bolus geometry defined by the parameters of the intravenous bolus injection (flow rate, dose and NaCl flush volume). Our study results have shown that the bolus remains compact but also shorter if a higher flow rate is being applied at equal dose. The enlargement of the NaCl flush volume has evidently caused an increased intraarterial CM concentration and a slightly bolus lengthening. The exact timing regimen requires an automated mechanical CM injection pump. In most countries, a total dose of 0.3 mmol/kg Gd is allowed for application during one investigation. Therefore, obtaining an angiogram of the entire iliac and leg region this total dose must be separated. 0.1 mmol/kg for each of the three measurements can be recommended. Otherwise, using this lower CM dose results in less spatial resolution. At least a dosage of 0.2 mmol/kg Gd is necessary to achieve a higher spatial resolution. The calculation of CM dosage should be also related to the dedicated vessel region of interest than to the body weight only.

The significance of three-dimensional MR-defined neurovascular compression for the pathogenesis of trigeminal neuralgia.

Three-dimensional MR tomography was used to examine the relationship between symptoms of trigeminal neuralgia and neurovascular compression of the nerve in 18 patients. The intensity of neurovascular interaction was classified according to neuroradiological criteria. We found that a radiologically defined compression or dislocation of the nerve by an artery was always associated with symptoms of trigeminal neuralgia. A simple contact between vessel and nerve, however, was also observed on the asymptomatic sides of 10 out of 18 patients. In 6 of 18 patients, in contrast, trigeminal neuralgia was present in spite of the absence of neurovascular contact. In accordance with a cited study based on autopsy and intraoperative findings, our findings indicate that, in a certain proportion of cases, trigeminal neuralgia may be caused by neurovascular compression alone, whereas in other cases, other pathogenetic factors may be involved to a varying degree or be even exclusively responsible for the development of trigeminal neuralgia. The possible significance of the method for a preoperative estimation of the success of microvascular decompression of the trigeminal nerve is discussed.

Anatomic evaluation of the circle of Willis: MR angiography versus intraarterial digital subtraction angiography.

PURPOSE: To evaluate the reliability of source images and maximum intensity projection images of MR angiography in showing the arterial segments of the circle of Willis. METHODS: In 62 patients, 526 arterial segments of the circle of Willis were determined to be present, partially present, or absent by blinded observers evaluating MR angiographic source images and maximum intensity projection images. Vessel diameter was measured on source images. These results were then compared with the results from intraarterial digital subtraction angiography. RESULTS: MR angiographic maximum intensity projection images had a sensitivity of 87% and a specificity of 88% and MR angiographic source images had a sensitivity of 89% and a specificity of 63% in depicting the presence of a vessel segment. The positive predictive value of an arterial segment with a diameter of at least 1 mm was 99%. CONCLUSION: MR angiography is a sensitive technique for detecting the anatomy of the circle of Willis. Maximum intensity projection images are more specific than source images. An arterial segment with a diameter of at least 1 mm on the source image is almost always present and patent.

Degenerative cartilage lesions of the hip--magnetic resonance evaluation.

The capability of magnetic resonance imaging (MRI) to visualize early degenerative arthritis of the hip was investigated. The study was performed on 8 healthy students and 45 elderly volunteers. Images were obtained by using an electronically variable Helmholtz coil (switched-array coil, SAC). In order to diagnose degenerative lesions of the joint cartilage, FISP sequences with a flip angle of 70 degrees were found preferable to compared sequences. MRI-detectable signs of degenerative arthritis of the hip were narrowed joint space due to partially thinned cartilage layers, focal areas of either increased or decreased signal intensity in the hyaline cartilage, complete loss of cartilage, and signal variation in the bone marrow. MRI of the hip may be appropriate to detect early degenerative changes in the hips of young high-risk patients to facilitate therapy planning.

Multi-centre clinical study evaluating the efficacy of SonoVue (BR1), a new ultrasound contrast agent in Doppler investigation of focal hepatic lesions.

OBJECTIVES: SonoVue is a new ultrasound contrast agent, which consists of stabilised microbubbles of a sulphur hexafluoride gas. The aim of the study was to assess its efficacy in the Doppler investigation of focal hepatic lesions. MATERIALS AND METHODS: Seventy patients with focal liver tumours were studied. Four doses (0.3, 0.6, 1.2 and 2.4 ml) of SonoVue were administered intravenously with at least 10 min delay between each injection. A complete colour/power and spectral Doppler imaging investigation of the lesions was performed at baseline pre-dosing and after each SonoVue injection. All examinations were recorded on SVHS videotapes. Baseline and post contrast videotapes were reviewed by the on-site (un-blinded) investigators and by two off-site blinded readers (a) to grade the global quality of the Doppler scans of the focal lesions vascularity and the normal parenchymal vessels (b) to measure the duration of clinically useful Doppler signal enhancement and (c) to determine the diagnostic accuracy and performance of the enhanced versus unenhanced scans using histopathology, tumour markers, CT and/or MR as the reference standard. RESULTS: A statistically significant improvement was observed at all four SonoVue doses in the off site assessment of global quality of the Doppler examination of tumoral and normal parenchymal vessels in comparison with the baseline (P < 0.05). The median duration of clinically useful enhancement was significantly increased with increasing doses (P < 0.001), ranging between 1.4-2.2 min for the lowest dose and 3.2-3.8 min for the highest dose for the off-site readers. On-site assessment of diagnostic accuracy showed a significant increase in the specificity of the Doppler diagnoses (P < 0.0016) with an increase in the positive and negative predictive values and in the likelihood ratio in differentiating between benign and malignant lesions. Off-site evaluation showed a significant increase in the accuracy of enhanced Doppler diagnosis in comparison with the baseline performance. CONCLUSION: The results suggest that SonoVue is effective in improving the display of tumoral vascularisation and may be useful in the characterisation of focal liver lesions.

[Magnetic resonance angiography of the arteries supplying the brain]. / Magnetresonanzangiographie der hirnversorgenden Arterien.

In a prospective study involving 52 patients, magnetic resonance angiography (MRA) was compared with arterial digital subtraction angiography (IA-DSA). MRA was performed within three days of the IA-DSA. It was carried out without knowledge of the findings on IA-DSA. Of 38 stenoses of the carotid arteries or their branches, demonstrated by IA-DSA, 33 could be seen on MRA; in four cases the stenosis was outside the imaging area of the coil. Sixteen out of 17 carotid occlusions were diagnosed by MRA. There was one false positive. In the vertebral artery territory, eleven out of 13 stenoses and three out of four occlusions were diagnosed by MRA. In evaluating the degree of stenosis, there was agreement in only 16 out of 33 cases. MRA over-estimated the severity of stenoses in 15 cases and under-estimated it in two. MRA is a new non-invasive method in the diagnosis of cerebro-vascular disease which must be evaluated by further studies.

[A simplified technic in high-resolution MR tomography of the shoulder: ZEPRA (Zoom of Eccentric Positioned Regions by active Aliasing)]. / Vereinfachte Technik bei der hochauflösenden MR-Tomographie der Schulter: ZEPRA.

A fairly easy method for high-resolution MR imaging of the shoulder is described. The combination of a defined arrangement of the gradients with a small-volume Helmholtz coil provides the possibility of a high zoom of structures apart from the magnet's centre. The maximal achievable zoom factor depends on the ratio of FOV/sensitive coil volume. The ZEPRA method acts by phase-encoded aliasing only. With this technique all interesting soft tissue of the shoulder may readily be visualized in every direction and with every type of sequence.

[The use of rapid sequences in craniocerebral MR diagnosis]. / Einsatz schneller Sequenzen bei der kraniozerebralen MR-Diagnostik.

MRI of the head is routinely performed with spin-echo sequences whereas gradient-echo sequences are still uncommon. Certain features of fast imaging sequences make them a promising tool for clinical investigations. The relative high signal-to-noise ratio/unit time demonstrates the usefulness of GE imaging as localising images. The extremely high contrast-flexibility is sometimes superior to SE imaging and may help to characterise structures and lesions. Flow dynamics are more clearly depicted than with SE sequences and lead to the dynamic evaluation of intracranial motion (CSF flow, blood flow). This information may be used in a special mode to achieve MR angiograms. Due to the very short repetition times, GE sequences are excellently suited to 3D application. This enables to reduce slice thickness to less than 1 mm with optional reconstructions in any virtual direction. In view of present developments in MR, GE imaging will be accepted in clinical diagnostic imaging in the near future.

[The MR tomographic findings in cranial manifestations of neurofibromatosis]. / MR-tomographische Befunde kranialer Manifestationen der Neurofibromatose.

Twelve patients with central neurofibromatosis underwent MR examination of the head. Among these, chiasma glioma was the most common CNS tumour (6/12). Seven patients had multifocal areas of increased T2-signal without mass effect predominantly involving the region of the basal ganglia. No corresponding CT abnormalities were present. These lesions may represent multifocal dysplasia and seem to be characteristic of central neurofibromatosis.

[MRT of the hypophysis: spin echo 2D or gradient echo 3D?]. / MRT der Hypophyse: Spinecho 2D oder Gradientenecho 3D?

Diagnostic efficacy of T1-weighted 3D gradient-echo and 2D spin-echo pulse sequences in the detection of adenomas were evaluated in a ROC study of 50 patients. Sensitivity, specificity and accuracy did not differ significantly, but in direct comparison gradient-echo received a clear lower rating due to susceptibility artifacts, lower signal-to-noise ratio, and inferior periglandular contrasts. Additional lesions could not be reliably detected in gradient-echo imaging at 1 mm slice thickness. A substitution of 2D spin-echo imaging by gradient-echo sequences cannot be recommended at present.

[Localization dependent patterns of findings in chondroblastoma]. / Lokalisationsabhängige Befundmuster beim Chondroblastom.

In a retrospective study the radiographs of 48 chondroblastomas from the files of the Bone Tumour Registry of Westphalia were evaluated. The purpose of the study was to investigate whether chondroblastomas display localisation-dependent radiographic patterns. All radiographs were analysed using the Lodwick criteria. All chondroblastomas (mean age: 18 y., m:f = 1.25:1) showed a geographic pattern of bone destruction. 32 lesions affected long bones, 10 short bones, and 6 flat bones. Chondroblastomas localised in flat bones (Lodwick IA: 0%, IB: 33%, IC: 67%) demonstrated more aggressive patterns of bone destruction compared to lesions affecting long bones (Lodwick IA: 56%, IB: 31%, IC: 13%) or short bones (Lodwick IA: 40%, IB: 50%, IC: 10%). There was no difference between the three bone types in other radiographic patterns (periostitis, calcification, trabeculation).

[Percutaneous stereotactic biopsy of non-palpable breast lesions using the Advanced Breast Biopsy Instrumentation (ABBI) system: critical evaluation of indication strategies]. / Perkutane stereotaktische Biopsie nicht palpabler Mammaläsionen mit dem Advanced Breast Biopsy Instrumentation (ABBI) System: Kritische Evaluation der Indikationsstellung.

PURPOSE: To compare the indications for biopsy with and without the use of the Breast Imaging Reporting and Data System. MATERIAL AND METHODS: Biopsies using the ABBI were performed in 62 patients with 64 non-palpable evident mammographic lesions. The initial decision for biopsy was made by non-radiologists due to suspicious microcalcifications (n = 53) and masses (n = 11). The indication was retrospectively reassessed by adopting the BI-RADS classification by three radiologists in consensus. The positive predictive value (PPV) of both indication strategies was assessed and compared. RESULTS: Biopsies adopting ABBI were performed without major side-effects and were diagnostic. Carcinoma was present in 14 lesions: nine specimens were diagnosed as DCIS and five as invasive carcinomas. For the 50 benign lesions histology revealed mastopathies (26/50) and fibroadenomas (8/50) as the most frequent diagnosis. The positive predictive value (PPV) for the initial indication was 22%, whereas PPV for BI-RADS based indications (categories 4 and 5) was 31%. CONCLUSION: ABBI enables stereotactically-guided procedures that result in representative and diagnostic biopsies. Standardized criteria like BI-RADS improve the PPV and should be a mandatory part of mammographic evaluation. Radiologists should remain involved in the decision making.

[The place of magnetic resonance tomography in the diagnosis of diseases of the shoulder joint]. / Stellenwert der Magnetresonanztomographie in der Diagnostik von Schultergelenkerkrankungen.

In a prospective study 43 patients with shoulder pain were examined by sonography and MRI. The findings were controlled by plain radiography, arthrography, and CT arthrography. Joint effusions and humeral head defects were equally identified by MR and sonography. In the diagnosis of labrum lesions, rotator cuff lesions, subacromial spurs, and synovial inflammatory disease sonography was not as accurate as MR. A special MR scoring system improved the diagnosis of an impingement syndrome.

Gene therapy with cytokine-transfected xenogeneic cells in metastatic tumors.

On the basis of compelling preclinical data in cats and dogs we initiated a clinical gene therapy study in nine patients with advanced solid tumors using xenogeneic fibroblasts secreting human IL-2 (Vero-IL-2 cells). Cohorts of three successive patients with tumors accessible to CT- or ultrasound-guided injection were treated repeatedly with 5 x 10(5), 5 x 10(6), or 5 x 10(7) Vero-IL-2 cells. Endpoints of the study were feasibility, toxicity, and clinical and biological effects of this novel approach to immunotherapy of cancer. Histopathological, immunological and molecular analyses were performed on biopsy specimens of tumors and blood samples from before, during and after treatment. Low levels of serum antibodies to Vero cells developed in 2/9 patients. Analysis of tumor biopsies showed increased expression of CD3 mRNA and enhanced tumor infiltration with varying lymphocyte subpopulations after treatment. In addition, monoclonal alterations of the TCR repertoire of blood and tumor lymphocytes were observed. Treatment was well tolerated and toxicity consisted of transient fever in one patient and short-lived, mild itching and erythema in two others. One patient with soft tissue sarcoma showed a more than 90% and more than 50% reduction of the volume of two distant, non-injected metastases, respectively, lasting for 22+ months. Four other patients showed stabilization of their disease for three to nine months, among whom was a patient with melanoma who developed marked vitiligo. We conclude that repeated injection of up to 5 x 10(7) Vero-IL-2 cells was safe and showed biological and clinical activity in heavily pretreated patients with advanced solid tumors. Further evaluation of intratumoral application of Vero-IL-2 seems warranted.