Ralph Gnannt

Quantitative radiologic criteria for the diagnosis of lumbar spinal stenosis: a systematic literature review

BackgroundBeside symptoms and clinical signs radiological findings are crucial in the diagnosis of lumbar spinal stenosis (LSS). We investigate which quantitative radiological signs are described in the literature and which radilogical criteria are used to establish inclusion criteria in clincical studies evaluating different treatments in patients with lumbar spinal stenosis.MethodsA literature search was performed in Medline, Embase and the Cochrane library to identify papers reporting on radiological criteria to describe LSS and systematic reviews investigating the effects of different treatment modalities.Results25 studies reporting on radiological signs of LSS and four systematic reviews related to the evaluation of different treatments were found. Ten different parameters were identified to quantify lumbar spinal stenosis. Most often reported measures for central stenosis were antero-posterior diameter (< 10 mm) and cross-sectional area (< 70 mm2) of spinal canal. For lateral stenosis height and depth of the lateral recess, and for foraminal stenosis the foraminal diameter were typically used. Only four of 63 primary studies included in the systematic reviews reported on quantitative measures for defining inclusion criteria of patients in prognostic studies.ConclusionsThere is a need for consensus on well-defined, unambiguous radiological criteria to define lumbar spinal stenosis in order to improve diagnostic accuracy and to formulate reliable inclusion criteria for clinical studies.

Dual-energy CT for characterization of the incidental adrenal mass: preliminary observations.

OBJECTIVE The purpose of our study was to evaluate the accuracy of virtual unenhanced images reconstructed from contrast-enhanced dual-energy CT for the differentiation of incidental adrenal masses in comparison with standard unenhanced CT. MATERIALS AND METHODS One hundred-forty patients (mean age, 74±9 years) underwent unenhanced and contrast-enhanced CT of the abdomen, the latter acquired with dual-energy for reconstruction of virtual unenhanced images. Two blinded and independent readers (R1 and R2) measured attenuation of each incidental adrenal mass on standard unenhanced and virtual unenhanced images using an optimized dual-energy three-material decomposition algorithm. RESULTS Fifty-one incidental adrenal masses were found in 42 of 135 patients (31%); 39 incidental adrenal masses were ≥1 cm. On the basis of unenhanced CT, 29 of 51 incidental adrenal masses and 22 of 39 incidental adrenal masses≥1 cm were classified as benign (HU<10). Virtual unenhanced image quality was rated as good or with mild impairment (2.45±0.83 for R1, 2.45±0.99 for R2). Image noise was 12.7±3.6 HU in unenhanced images and 8.8±2.0 HU in virtual unenhanced images (p<0.001). There was no significant difference in incidental adrenal mass attenuation between unenhanced and virtual unenhanced images for all incidental adrenal masses (5.9±21.0 HU vs 7.0±20.6 HU, p=0.48) and for those≥1 cm (6.6±18.5 HU vs 7.9±18.3 HU, p=0.87). Sensitivity, specificity, and accuracy of virtual unenhanced images for the characterization of incidental adrenal masses as probably benign were 76%, 82%, and 78% for R1 and 79%, 95%, and 86% for R2, respectively. For incidental adrenal masses≥1 cm, sensitivity, specificity, and accuracy increased to 95%, 100%, and 97% for R1 and 91%, 100%, and 95% for R2. CONCLUSION Reconstruction of virtual unenhanced images from contrast-enhanced dual-energy CT of the abdomen allows the characterization of the incidental adrenal masses with a good accuracy compared with standard unenhanced CT, with the most favorable results in incidental adrenal masses measuring≥1 cm.

Quantification of liver fat in the presence of iron and iodine: an ex-vivo dual-energy CT study.

Purpose:Iodinated contrast media (CM) and iron in the liver are known to hinder an accurate quantification of liver fat content (LFC) with single-energy computed tomography (SECT). The purpose of this study was to evaluate the feasibility and accuracy of dual-energy CT (DECT) for ex vivo quantification of LFC, in the presence of iron and CM, compared with SECT. Materials and Methods:Sixteen phantoms with a defined LFC of 0%, 10%, 30%, and 50% fat and with varying iron content (0, 1.5, 3, and 6 mg/mL wet weight liver) were scanned with a second-generation dual-source 128-slice CT system. Phantoms were scanned unenhanced and contrast-enhanced after adding 1.0 mg/mL iodine to each phantom. Both SECT (120 kV) and DECT (tube A: 140 kV, using a tin filter 228 mAs; tube B: 80 kV, 421 mAs) data were acquired. An iron-specific dual-energy 3-material decomposition algorithm providing virtual noniron images (VNI) was used to subtract iron and CM from the data. CT numbers (Hounsfield units) were measured in all data sets, including 120 kV from SECT, as well as 140 kV, 80 kV, 50%:50% weighted 80 kV/140 kV, and VNI derived from DECT. The dual-energy index was calculated from 80 kV and 140 kV data. SECT and DECT measurements (Hounsfield units) including the dual-energy index of unenhanced and contrast-enhanced phantoms were compared with the known titrated LFC, using Pearson correlation analysis and Student t test for related samples. Results:Inter-reader agreement was excellent for all measurements of CT numbers in both SECT and DECT data (Pearson r, 0.965–1.0). For fat quantification in the absence of iron and CM, CT numbers were similar in SECT and DECT (all, P > 0.05), showing a linear correlation with titrated LFC (r ranging from 0.981 to 0.999; P < 0.01). For fat quantification in the presence of iron but without CM, significant underestimation of LFC was observed for all measurements in SECT and DECT (P < 0.05), except for VNI. Measurements in VNI images allowed for an accurate LFC estimation, with no significant differences compared with measurements in iron-free phantoms (all, P > 0.25). For fat quantification in the presence of iron and CM, further underestimation of LFC was seen for measurements in SECT and DECT (P < 0.015), except for VNI. Measurements in VNI images showed a high accuracy for estimating the LFC, with no significant difference compared with measurements in iron- and CM-free phantoms (P > 0.2). Conclusions:Our ex vivo phantom study indicates that DECT with the use of a dedicated, iron-specific 3-material decomposition algorithm allows for the accurate quantification of LFC, even in the presence of iron and iodinated CM. VNI images reconstructed from DECT data equal nonenhanced SECT data of liver without CM by eliminating iron and iodine from the images. No added value was seen for DECT as compared with SECT for quantification of LFC in the absence of iron and iodine.

Diagnostic Performance of Dual-Energy CT for the Detection of Traumatic Bone Marrow Lesions in the Ankle: Comparison with MR Imaging

PURPOSE To evaluate prospectively the performance of noncalcium images reconstructed from dual-energy (DE) computed tomography (CT) for the diagnosis of bone marrow lesions in patients with acute ankle joint trauma in comparison with magnetic resonance (MR) images. MATERIALS AND METHODS The study had local ethics board approval, and written informed consent was obtained. Thirty consecutive patients (15 women; mean age, 34 years±11.8 [standard deviation]) underwent dual-source DE CT (80 kVp and 140 kVp with tin filter) and MR imaging within 1 day following acute ankle trauma. DE CT data were postprocessed by using a three-material decomposition algorithm for generating noncalcium images. MR and noncalcium images were graded by two blinded, independent readers using a four-point system (1=distinct bone marrow lesion, 4=no lesion); CT numbers in noncalcium images were calculated by a third reader. MR imaging interpretations served as the reference standard. RESULTS Interreader agreement for qualitative grading of DE CT images was substantial (κ=0.66). The respective sensitivity, specificity, positive predictive value, and negative predictive value of DE CT for depicting distinct bone marrow lesions for both readers were 90.0% each, 80.5% and 81.6%, 25.4% and 26.5%, and 99.1% each. In regions without abnormality, CT numbers in noncalcium images gradually increased from proximal to distal location (P<.001). Significant differences in CT numbers were found in regions positive for bone marrow lesions compared with those that were negative (P<.001). CT numbers for the diagnosis of distinct bone marrow lesions according to MR imaging revealed areas under the receiver operating characteristic curve of 0.973, 0.813, and 0.758 for ankle mortise, talar dome, and talar body/head, respectively. CONCLUSION Compared with MR images, distinct traumatic bone marrow lesions of the ankle joint can be diagnosed on noncalcium images reconstructed from DE CT with high sensitivity and excellent negative predictive value, but with moderate specificity and low positive predictive value.

Low Kilovoltage CT of the Neck with 70 kVp: Comparison with a Standard Protocol

These authors imaged 27 patients with neck CT using 70 kVp and compared the scans with previous studies obtained using the typical 120-kVp technique on the same scanner. Two observers studied image quality and artifacts in 3 neck regions (upper, middle, and lower). They concluded that CT of the cervical soft tissues at 70 kVp is feasible, provides diagnostic image quality with improved contrast to noise, and reduces radiation dose by approximately 34% compared with a standard protocol at 120 kVp. In contrast, low kVp CT of the lower cervical spine suffers from compromised image quality. BACKGROUND AND PURPOSE: CT protocols should aim for radiation doses being as low as reasonably achievable. The purpose of our study was to assess the image quality and radiation dose of neck CT at a tube potential of 70 kVp. MATERIALS AND METHODS: Twenty patients (7 female, mean age 51.4 years, age range 19–81 years) underwent contrast-enhanced 64-section CT of the neck at 70 kVp (ATCM, effective tube current-time product 614 eff.mAs, range 467–713 eff.mAs). All 20 patients had a previous neck CT at 120 kVp on the same scanner. Two radiologists assessed image quality and artifacts in the upper, middle, and lower neck. Image noise and attenuation were measured, and the CNR was calculated. Effective radiation dose was calculated. RESULTS: Interobserver agreement regarding image quality of soft tissue for 70-kVp and 120-kVp scans was good to excellent. At 70 kVp, soft tissues were of diagnostic image quality in all scans, whereas the lower cervical spine was not of diagnostic quality in 3 and 4 scans per both readers. No difference was found among 70-kVp and 120-kVp scans for soft tissue image quality in the upper neck, while image quality was significantly better in the middle at 70 kVp (P < .05) and better in the lower third at 120 kVp (P < .05). CNR was significantly higher at 70 kVp in all levels for both readers (P < .001). Effective radiation dose at 70 kVp was significantly lower (0.88 ± 0.2mSv) than at 120 kVp (1.33 ± 0.2mSv, P < .001). CONCLUSIONS: CT of the cervical soft tissues at 70 kVp is feasible, provides diagnostic image quality with improved CNR, and reduces radiation dose by approximately 34% compared with a standard protocol at 120 kVp. In contrast, low kVp CT of the lower cervical spine suffers from compromised image quality.

Effect of automatic tube voltage selection on image quality and radiation dose in abdominal CT angiography of various body sizes: A phantom study

AIM To assess the effect of an automatic tube voltage selection technique on image quality and radiation dose in abdominal computed tomography (CT) angiography of various body sizes. MATERIALS AND METHODS An abdominal aortic phantom was filled with iodinated contrast medium and placed into three different cylindrical water containers, which simulated a small, intermediate-sized, and large patient. The phantom was scanned with a standard 120 kVp abdominal CT angiography protocol and with an optimized tube voltage protocol that was modulated by an automatic tube voltage technique. The attenuation of the aorta, background, and image noise was measured, and the contrast-to-noise ratio (CNR) was calculated. Three independent readers assessed the overall image quality. RESULTS The automatic tube voltage technique selected 70 kVp as the optimal tube voltage for the small phantom, 80 kVp for the intermediate phantom, and 100 kVp for the large phantom. Compared to the standard 120 kVp protocol, the automatic tube voltage selection yielded significantly increased CNR values in the small phantom (15.8 versus 19.4, p < 0.001), intermediate phantom (8.4 versus 8.7, p < 0.05), and large phantom (4.3 versus 4.6, p < 0.01). The automatic tube voltage selection resulted in a 55%, 49%, and 39% reduction in the volume CT dose index (CTDI(vol)) in the small, intermediate, and large phantoms, respectively. The subjective overall image quality of the three phantom sizes at different tube voltages ranged between poor and good. CONCLUSION Compared to a standard 120 kVp abdominal CT angiography protocol, the automatic tube voltage selection substantially reduced the radiation dose without compromising image quality in various simulated patient sizes.

MR imaging of the postoperative knee.

Advances in orthopedic and arthroscopic surgical procedures of the knee such as, knee replacement, ligamentous reconstruction as well as articular cartilage and meniscus repair techniques have resulted in a significant increase in the number of patients undergoing knee arthroscopy or open surgery. As a consequence postoperative MR imaging examinations increase. Comprehensive knowledge of the normal postoperative MR imaging appearances and abnormal findings in the knee associated with failure or complications of common orthopedic and arthroscopic surgical procedures currently undertaken is crucial. This article reviews the various normal and pathological postoperative MR imaging findings following anterior and posterior cruciate ligament, medial collateral ligament and posterolateral corner reconstruction, meniscus and articular cartilage surgery as well as total knee arthroplasty with emphasis on those surgical procedures which general radiologists will likely be faced in their daily clinical routine. J. Magn. Reson. Imaging 2011;.

Prospective Morphologic and Dynamic Assessment of Deep Flexor Tendon Healing in Zone II by High-Frequency Ultrasound: Preliminary Experience

OBJECTIVE The purpose of this article is to prospectively evaluate early postoperative morphologic and functional changes after deep flexor tendon repair in zone II using ultrasound and to correlate findings from ultrasound with the clinical outcome. SUBJECTS AND METHODS Ten patients (mean age, 34 years; range, 19-55 years) with 11 injured deep flexor tendons of the hand underwent surgical tendon repair. Postoperative tendon morphology was assessed with gray-scale and power Doppler ultrasound over a period of 3 months. Tendon excursion over the proximal interphalangeal joint was assessed by sonographic scar tracking. Correlation of ultrasound findings with clinical outcome was performed. RESULTS Almost all repaired tendons exhibited a spindlelike shape after 1 week, of which 50% developed a normal shape after 12 weeks. A persisting spindlelike shape over 3 months was associated with a significantly increased tendon excursion (p < 0.05) and a trend toward better active motion of the fingers (p = 0.056). Tendons with increased power Doppler signal showed a significantly better tendon excursion and active motion after 12 weeks (all p < 0.05). Tendon excursion measurements obtained by scar tracking showed excellent correlation (r = 0.84; p < 0.05) with total active finger motion. CONCLUSION Preliminary data of this study indicate a better clinical outcome if a sutured tendon maintains a spindlelike shape and increased power Doppler signal. This might indicate a predominantly intrinsic healing pattern with reduced adhesion formation. Ultrasound morphology, power Doppler signal, and tendon excursion may be helpful tools to rate tendon healing and to establish individually modified rehabilitation protocols.

Distinguishing infected from noninfected abdominal fluid collections after surgery: an imaging, clinical, and laboratory-based scoring system.

ObjectivesMortality from abdominal abscesses ranges from 30% in treated cases up to 80% to 100% in patients with undrained or nonoperated abscesses. Various computed tomographic (CT) imaging features have been suggested to indicate infection of postoperative abdominal fluid collections; however, features are nonspecific and substantial overlap between infected and noninfected collections exists. The purpose of this study was to develop and validate a scoring system on the basis of CT imaging findings as well as laboratory and clinical parameters for distinguishing infected from noninfected abdominal fluid collections after surgery. Materials and MethodsThe score developmental cohort included 100 consecutive patients (69 men, 31 women; mean age, 58 ± 17 years) who underwent portal-venous phase CT within 24 hours before CT-guided intervention of postoperative abdominal fluid collections. Imaging features included attenuation (Hounsfield unit [HU]), volume, wall enhancement and thickness, fat stranding, as well as entrapped gas of fluid collections. Laboratory and clinical parameters included diabetes, intake of immunosuppressive drugs, body temperature, C-reactive protein, and leukocyte blood cell count. The score was validated in a separate cohort of 30 consecutive patients (17 men, 13 women; mean age, 51 ± 15 years) with postoperative abdominal fluid collections. Microbiologic analysis from fluid samples served as the standard of reference. ResultsDiabetes, body temperature, C-reactive protein, attenuation of the fluid collection (in HUs), wall enhancement and thickness of the wall, adjacent fat stranding, as well as entrapped gas within the fluid collection were significantly different between infected and noninfected collections (P < 0.001). Multiple logistic regression analysis revealed diabetes, C-reactive protein, attenuation of the fluid collection (in HUs), as well as entrapped gas as significant independent predictors of infection (P < 0.001) and thus was selected for constructing a scoring system from 0 to 10 (diabetes: 2 points; C-reactive protein, ≥100 mg/L: 1 point; attenuation of fluid collection, ≥20 HU: 4 points; entrapped gas: 3 points). The model was well calibrated (Hosmer-Lemeshow test, P = 0.36). In the validation cohort, scores of 2 or lower had a 90% (95% confidence interval [CI], 56%–100%) negative predictive value, scores of 3 or higher had an 80% (95% CI, 56%–94%) positive predictive value, and scores of 6 or higher a 100% (95% CI, 74%–100%) positive predictive value for diagnosing infected fluid collections. Receiver operating characteristic analysis revealed an area under the curve of 0.96 (95% CI, 0.88–1.00) for the score. ConclusionsWe introduce an accurate scoring system including quantitative radiologic, laboratory, and clinical parameters for distinguishing infected from noninfected fluid collections after abdominal surgery.