Impact of increasing levels of advanced iterative reconstruction on image quality in low-dose cardiac CT angiography.

PURPOSE: To investigate the effects of an advanced iterative reconstruction (IR) technique on subjective and objective image quality (IQ) in low-dose cardiac CT angiography (CCTA). MATERIALS AND METHODS: 30 datasets of prospectively triggered "step-and-shoot" CCTA scans acquired on a 256-slice CT scanner with optimized exposure settings were processed on a prototype IR system using filtered back-projection (FBP) and 4 levels of advanced IR (iDose4, Philips) providing incremental rates of IR (level 2, 4, 6, 7). In addition, the effects of different reconstruction kernels (semi-smooth [CB], standard with edge-enhancement [XCB]) and a "multi-resolution" feature [MR] to preserve the noise power spectrum were evaluated resulting in a total of n = 480 image sets. Contrast-to-noise ratios (CNR) were computed from regions of interest at 9 coronary locations. The subjective IQ was rated on a 4-point-scale with "classic" image appearance and noise-related artifacts as main criteria. RESULTS: At an effective dose of 1.7 ±â€Š0.7 mSv, the CNR significantly improved with every increasing level of IR (range: 14.2 - 27.8; p < 0.001) with the best objective IQ at the highest level of IR (level 7). The subjective IQ, however, was rated best at the medium level of IR (level 4) with minimal artifacts and a more "classic" image appearance when compared to higher IR levels. The XCB kernel provided better subjective ratings than CB (p < 0.05) and the MR feature further increased the IQ at a high level of IR. CONCLUSION: The objective IQ of low-dose CCTA progressively improves with an increasing level of IR. The best subjective IQ, however, is reached at medium levels of IR combined with an edge-enhancing kernel allowing for preservation of a "classic" image appearance suggesting application in the clinical routine. KEY POINTS: • iterative reconstruction (IR) improves image quality in low-dose coronary CTA• objective image quality (CNR) enhances with increasing level of IR• best subjective image quality is reached at medium level of IR• "multi-resolution" algorithm further improves image quality at a higher level of IR.

Structural white matter changes in adolescents and young adults with maple syrup urine disease.

OBJECTIVE: To get insight into the nature of magnetic resonance (MR) white matter abnormalities of patients with classic maple syrup urine disease (MSUD) under diet control. METHODS: Ten patients with classic MSUD and one with a severe MSUD variant (mean age 21.5 ± 5.1 years) on diet and 11 age and sex-matched healthy subjects were enrolled. Apart from standard MR sequences, diffusion weighted images (DWI), diffusion tensor images (DTI), and magnetization transfer images (MT) were obtained and comparatively analyzed for apparent diffusion coefficient (ADC), tensor fractional anisotropy (FA) and MT maps in 11 regions of interest (ROI) within the white matter. RESULTS: In MSUD patients DWI, DTI and FA showed distinct signal changes in the cerebral hemispheres, the dorsal limb of internal capsule, the brain stem and the central cerebellum. Signal intensity was increased in DWI with a reduced ADC and decreased values for FA. MT did not reveal differences between patients and control subjects. CONCLUSION: Signal abnormalities in the white matter of adolescents and young adults under diet control may be interpreted as consequence of structural alterations like dysmyelination. The reduced ADC and FA in the white matter with preserved MT indicate a reduction in fiber tracks.

[Radiological diagnosis of the paranasal sinuses]. / Radiologische Diagnostik der Nasennebenhöhlen.

Although diseases of the paranasal sinuses have a relatively homogeneous clinical presentation, their causes can vary considerably. Radiological imaging only became relevant in paranasal sinus diagnostics following the introduction of cross-sectional imaging. In addition to technical details on imaging procedures and the individual criteria of the different modalities, anatomic details and congenital variations are presented. Particularly in acute inflammatory diseases as well as traumatic lesions, imaging is essential in preoperative planning and postoperative control. The article gives a detailed description of options in radiologic imaging of the paranasal sinuses.

[Image quality in multidetector CT of paranasal sinuses: potential of dose reduction using an adaptive post-processing filter]. / Bildqualität in der Multidetektor-CT der Nasennebenhöhlen: Potenzial zur Dosisreduktion bei Anwendung eines adaptiven Nachverarbeitungsfilters.

PURPOSE: Evaluation of subjective image quality in dose-reduced multi-detector CT (MDCT) of paranasal sinuses using a 2D non-linear adaptive post-processing filter (2D-NLAF). MATERIALS AND METHODS: MDCT of paranasal sinuses was simulated using a human head phantom at a Somatom Sensation Cardiac 64 (Siemens, Erlangen). At constant collimation (64 × 0.6 mm) und pitch (p = 1), the tube current (50, 100, 200 mAs) and tube potential (80, 100, 120 kVp) were modified. The radiation exposure was represented by CTDIvol. Four independent blinded radiologists evaluated the image quality of axial 2 mm images and coronal reformations concerning the assessment of "fractures" and "soft tissue processes". The subjective image quality of original and post-processed images using a 2D-NLAF (SharpViewCT®, Sweden) was graded on a 5-point scale ("1" excellent - "5" not adequate) and compared. RESULTS: Compared to the protocol with the best image quality (120kVp/ 200 mAs) 2D-NLAF led to a significant improvement in the subjective image quality at 100 kVp/ 100 mAs (score "1.4" with filter versus "2.2" without) and 120 kVp/ 50 mAs ("1.6" versus "2.0") (p < 0.03) particularly for high contrasts ("fractures", p < 0.001). In "soft tissue processes", 2D-NLAF provided improved quality from "2.1" to "1.4" (p < 0.04) at 100 kVp/ 100 mAs. Down to a CTDIvol of 8 mGy, the image quality was rated "good", and down to 5 mGy "diagnostic". CONCLUSION: The phantom study indicates a dose reduction potential in MDCT of paranasal sinuses up to 58% compared to a standard dose protocol using a 2D-NLAF without an essential loss of image quality. 2D-NLAF is particularly effective at 100 kVp/ 100 mAs and 120 kVp/ 50 mAs.

A novel MRI-biomarker candidate for Alzheimer's disease composed of regional brain volume and perfusion variables.

BACKGROUND: Earlier evidence indicates that regional cerebral volume (rVOL) and blood flow (rCBF) variables carry independent information on incipient and early Alzheimer's disease (AD) and combining these modalities may increase discriminant performance. We compared single variables and combinations regarding their power for optimizing diagnostic accuracy. METHODS: Twelve cognitively normal elderly controls (CN), 30 subjects with mild cognitive impairment (MCI) and 15 with mild AD were examined by structural and perfusion-weighted magnetic resonance imaging (MRI) in single sessions at 1.5 Tesla. rVOLs were measured by manual volumetry, and rCBFs were calculated with a ROI-based co-localization technique. RESULTS: Applying single MRI variables for the differentiation of AD versus CN, the area under curve (AUC) of receiver operating characteristic curves (ROCCs) was highest for rVOL variables (maximum of 0.972 for right amygdala). A composite marker selected and weighted by logistic regression containing left amygdalar rCBF, left hippocampal and right amygdalar rVOLs gave a diagnostic accuracy for AD versus CN of 100%. Internal cross-validation revealed a reliability of 88.9%. CONCLUSIONS: Whilst external revalidation is mandatory employing a naturalistic sample containing disease controls, our phase I/II findings demonstrate that deducing composite markers from multimodal MRI acquisitions can optimize diagnostic accuracy for AD.

[Radiological diagnosis of the paranasal sinuses]. / Radiologische Diagnostik der Nasennebenhöhlen.

Although diseases of the paranasal sinuses have a relatively homogeneous clinical presentation, their causes can vary considerably. Radiological imaging only became relevant in paranasal sinus diagnostics following the introduction of cross-sectional imaging. In addition to technical details on imaging procedures and the individual criteria of the different modalities, anatomic details and congenital variations are presented. Particularly in acute inflammatory diseases as well as traumatic lesions, imaging is essential in preoperative planning and postoperative control. The article gives a detailed description of options in radiologic imaging of the paranasal sinuses.

[Dose reduction and image quality in MDCT of the upper abdomen: potential of an adaptive post-processing filter]. / Dosisreduktion und Bildqualität in der MDCT des Oberbauchs: Potenzial eines adaptiven Nachverarbeitungsfilters.

PURPOSE: To evaluate the effects of a 2D non-linear adaptive post-processing filter (2D-NLAF) on image quality in dose-reduced multi-detector CT (MDCT) of the upper abdomen. MATERIALS AND METHODS: MDCT of the upper abdomen was simulated on a 64-slice scanner using a multi-modal anthropomorphic phantom (CIRS, Norfolk, USA). While keeping the collimation (64 x 0.6 mm) and pitch (p = 1) unchanged, the tube current (100 - 500 mAs) and tube potential (80 - 140 kVp) were varied to perform MDCT as high dose (CTDI > 20), middle dose (CTDI 10 - 20) and low dose (CTDI < 10) level protocols. Four independent blinded radiologists evaluated axial images with a thickness of 7 and 3 mm with respect to the presentation of "mesenteric low contrast lesions", "liver veins", "liver cysts", "renal cysts" and "big vessels". The subjective image quality of original data and post-processed images using a 2D-NLAF (SharpViewCT, Linköping, Sweden) was graded on a 5-point scale (from "1" not visible to "5" excellent) and statistically analyzed. The effective dose (E) was estimated using commercial software (CT-EXPO). RESULTS: For all protocol groups, 2D-NLAF led to a significant improvement in subjective image quality for all examined lesions (p < 0.01), particularly at the protocols of middle dose (E: 5 - 8 mSv) and low dose level (E: 1 - 5 mSv). A maximum effect was seen in middle dose protocols for "low contrast lesions" (score "3.3" with filter versus "2.5" without) and "liver veins" ("4.5" versus "3.9"). CONCLUSION: The phantom study indicates a potential dose reduction of up to 50 % in MDCT of the upper abdomen by use of a 2D-NLAF, which should be further examined in clinical trails.

Renal transplant failure due to urologic complications: Comparison of static fluid with contrast-enhanced magnetic resonance urography.

PURPOSE: Postrenal reasons of renal transplant failure can be assessed by magnetic resonance urography. This study was designed to retrospectively compare the diagnostic accuracy of static fluid (T2-)MRU compared to contrast enhanced (CE-)MRU in patients with renal transplant failure. MATERIAL AND METHODS: Thirty-five consecutive patients (14 female, 21 men; mean age 48.6 years) with renal transplant failure and sonographically detected hydronephrosis were examined both with T2-MRU as well as CE-MRU resulting in 39 MRU examinations. MRU was performed both using T2-weighted HASTE-sequence (T2-MRU) as well as Gadolinium-enhanced 3D-FLASH-sequence (CE-MRU) on a 1.5-T clinical MRI scanner (Magnetom Vision, Siemens Medical Solutions). Subjective image quality of resulting maximum intensity projection was assessed in consensus by two readers blinded to the final diagnosis, using a five point scale. MRU findings were correlated to sonography, operative results or clinical follow up. RESULTS: CE-MRU yielded a sensitivity of 85.7% (T2-MRU 76.2%), and a specificity of 83.3% (T2-MRU: 73.7%), however statistical significance was not reached. The subjective image quality was significantly better in CE-MRU. CONCLUSIONS: Only concerning subjective image quality CE-MRU proved superior to T2-MRU. Yet, there was no significant difference in diagnostic accuracy between T2- and CE-MRU. Thinking of incipient nephrogenic systemic fibrosis, T2-MRU can be used as reliable alternative in patients with decreased renal transplant function due to urological complications.

Assessment of three different software systems in the evaluation of dynamic MRI of the breast.

OBJECTIVE: The aim was to compare the diagnostic performance and handling of dynamic contrast-enhanced MRI of the breast with two commercial software solutions ("CADstream" and "3TP") and one self-developed software system ("Mammatool"). MATERIALS AND METHODS: Identical data sets of dynamic breast MRI from 21 patients were evaluated retrospectively with all three software systems. The exams were classified according to the BI-RADS classification. The number of lesions in the parametric mapping was compared to histology or follow-up of more than 2 years. In addition, 25 quality criteria were judged by 3 independent investigators with a score from 0 to 5. Statistical analysis was performed to document the quality ranking of the different software systems. RESULTS: There were 9 invasive carcinomas, one pure DCIS, one papilloma, one radial scar, three histologically proven changes due to mastopathy, one adenosis and two fibroadenomas. Additionally two patients with enhancing parenchyma followed with MRI for more than 3 years and one scar after breast conserving therapy were included. All malignant lesions were classified as BI-RADS 4 or 5 using all software systems and showed significant enhancement in the parametric mapping. "CADstream" showed the best score on subjective quality criteria. "3TP" showed the lowest number of false-positive results. "Mammatool" produced the lowest number of benign tissues indicated with parametric overlay. CONCLUSION: All three software programs tested were adequate for sensitive and efficient assessment of dynamic MRI of the breast. Improvements in specificity may be achievable.

Modern therapy of rectal carcinoma.

Throughout the past decade the treatment of rectal carcinoma has improved remarkably. Today, individualized multimodality treatment allows local and distant tumor freedom with preservation of anorectal and genitourinary function in a majority of patients. Radiotherapy is elementary in reducing the risk of local recurrence whereas chemotherapy including promising novel agents prevents or eliminates distant metastases. However, surgery revolutionized by TME (total mesorectal excision) remains the only curative treatment for rectal carcinoma. In this study the authors review the developments as well as the current status of modern treatment for rectal carcinoma.

[Angiosarcoma of the temporal bone]. / Angiosarkom des Os temporale.

Angiosarcoma of the temporal bone is an extremely rare malignant tumor, which originates from vascular endothelium. We describe a case of a 57-year-old woman, initially presenting with progressive hearing loss, otorrhea as well as facial palsy diagnosed as a mastoiditis elsewhere. After subtotal mastoidectomy histological examination revealed an angiosarcoma of the mastoid. Since the tumor was not completely removed lateral petrosectomy and postoperative radiotherapy were performed. Afterwards the patient developed local recurrence with intracerebral tumor extension. During palliative polychemotherapy the patient developed a pneumonia and deceased. In this manuscript the morphology, imaging characteristics and current treatment options of angiosarcomas of the lateral skull base are reviewed and discussed.

[Analysis of 64-row multidetector CT images for preoperative angiographic evaluation of potential living kidney donors]. / Analyse der mehrphasigen 64-Zeilen-Multidetektor-Computertomographie zur präoperativen angiographischen Evaluation potenzieller Lebendnierenspender.

BACKGROUND: Anatomical imaging and the ascertainment of any anomalies in the renal vessels and the ureters are essential in the planning of a kidney donation. The aim of the present study was to assess the value of 64-row multidetector CT in noninvasive examination of the renal vessels and ureters of potential living kidney donors. METHODS: The evaluation embraced 63 living renal donors (LNS) who underwent preoperative CT examination from December 2004 to January 2007. The examinations were all carried out using a Somatom Sensation -Cardiac 64 (Siemens Medical Solutions, Germany). As well as CT angiography (CTA), a venous phase of the abdomen and a late phase after 15 min using low-dose technique were performed for CT urography (CTU). The radiological findings were compared with the surgical results, or with the angiograms in 2 cases. Sensitivity, specificity and both negative and positive predictive value were calculated. RESULTS: In the 63 (31 female, 32 male) donors CTA had a sensitivity of 100% in examination of the main and accessory renal arteries and of 98.3% when the venous and ureteric anatomy were assessed. The sensitivity of low-dose CTU was also 100%. CONCLUSION: The findings recorded in this study indicate that noninvasive preoperative planning with 64-row multidetector CTA and CTU is a reliable "one-stop shopping" method of examination for potential living kidney donors.

CT-perfusion imaging of the human brain: advanced deconvolution analysis using circulant singular value decomposition.

According to indicator dilution theory tissue time-concentration curves have to be deconvolved with arterial input curves in order to get valid perfusion results. Our aim was to adapt and validate a deconvolution method originating from magnetic resonance techniques and apply it to the calculation of dynamic contrast enhanced computed tomography perfusion imaging. The application of a block-circulant matrix approach for singular value decomposition renders the analysis independent of tracer arrival time to improve the results.

Radiation exposure of patients in comprehensive computed tomography of the head in acute stroke.

BACKGROUND AND PURPOSE: To assess patient radiation exposure in comprehensive stroke imaging using multidetector row CT (MDCT) combining standard CT of the head, cerebral perfusion (CTP), and CT angiography (CTA) studies. METHODS: Examination protocols for CT and CTA of cerebral and cervical vessels, as well as CTP were simulated using a Somatom Sensation Cardiac 64. Effective doses were derived from measurements with the use of lithium-fluoride thermoluminescent dosimeters (LiF-TLD) at several organ sites using an Alderson-Rando phantom. RESULTS: LiF-TLD measurements resulted in effective doses of 1.7 mSv for CT, 1.9 mSv for CTA of intracranial vessels, and 2.8 mSv for CTA of cervical vessels, respectively. Depending on examination parameters, effective doses varied between 1.1 and 5.0 mSv for cerebral CTP. For CTP, local doses in the area of the primary beam ranged between 114 and 444 mGy. CONCLUSIONS: Comprehensive stroke imaging may result in up to 9.5 mSv with possible local doses of 490 mGy. Although critical doses for organ damage (eg, cataract formation or hair loss) are not reached, physicians need to be aware of possible radiation induced sequelae particularly in repetitive examinations.

[Interactive thresholded volumetry of abdominal fat using breath-hold t1-weighted magnetic resonance imaging]. / Interaktive Schwellenwert-basierte Volumetrie des abdominalen Fettgehaltes mittels atemgehaltener T1-gewichteter Magnetresonanztomographie.

PURPOSE: Development of a feasible and reliable method for determining abdominal fat using breath-hold T1-weighted magnetic resonance imaging. MATERIALS AND METHODS: The high image contrast of T1-weighted gradient echo MR sequences makes it possible to differentiate between abdominal fat and non-fat tissue. To obtain a high signal-to-noise ratio, the measurements are usually performed using phased array surface coils. Inhomogeneity of the coil sensitivity leads to inhomogeneity of the image intensities. Therefore, to examine the volume of abdominal fat, an automatic algorithm for intensity correction must be implemented. The analysis of the image histogram results in a threshold to separate fat from other tissue. Automatic segmentation using this threshold results directly in the fat volumes. The separation of intraabdominal and subcutaneous fat is performed by interactive selection in a last step. RESULTS: The described correction of inhomogeneity allows for the segmentation of the images using a global threshold. The use of semiautomatic interactive volumetry makes the analysis more subjective. The variance of volumetry between observers was 4.6 %. The mean time for image analysis of a T1-weighted investigation lasted less than 6 minutes. CONCLUSION: The described method facilitates reliable determination of abdominal fat within a reasonable period of time. Using breath-hold MR sequences, the time of examination is less than 5 minutes per patient.