[Lower leg, ankle and foot]

CLINICAL/METHODICAL ISSUE

Bipedal locomotion means high mechanical stress on the lower extremities and susceptibility to fractures. On the one hand, these can be the result of a one-time traumatic stress in the context of high speed traumas or falls, but can also result from repetitive microtraumas with subsequent stress fractures.

STANDARD RADIOLOGICAL METHODS

For all fracture entities and localizations, X‑ray diagnostics is the basic modality.

METHODICAL INNOVATIONS

For optimal surgical reconstruction of intra-articular fractures or in complex fracture configurations, computed tomography should be generously used to improve postoperative outcome.

PERFORMANCE

The classification of the individual fractures should enable standardised further therapy planning, especially with regard to conventional or surgical treatment.

ACHIEVEMENTS

The combination of X‑ray, magnetic resonance imaging and computed tomography makes a reliable diagnosis regarding foot fractures possible.

PRACTICAL RECOMMENDATIONS

Important for the use of individual classification systems is always, in addition to clinical relevance, the safe and equal understanding of the individual types and degrees by the radiologist and the referring colleague.

Virtual mono-energetic images and iterative image reconstruction: abdominal vessel imaging in the era of spectral detector CT

AIM

To compare the quality of virtual mono-energetic (VMI) and polychromatic images reconstructed with hybrid iterative (PCI_HIR) or model-based reconstruction (PCI_MBR) derived from dual-layer spectral detector computed tomography (SDCT) in arterial phase images to visualise the aorta and abdominal main branches.

MATERIAL AND METHODS

A retrospective review of 50 patients with abdominal arterial phase scans was undertaken. Attenuation, intraluminal noise, and signal-/contrast-to-noise ratio (S-/CNR) were assessed in the PCI_HIR, PCI_MBR and VMI_40keV, VMI_70keV, and VMI_100keV images. Contrast, noise, and visualization of soft-plaque, and macro-/micro-calcifications were scored in a blinded reading by two radiologists.

RESULTS

VMI_40keV yielded highest S-/CNR (p≤0.001). VMI_70keV and PCI_MBR showed comparable SNR (p≥0.999) and yielded higher SNR than PCI_HIR. VMI_70keV yielded higher CNR than PCI_HIR (p<0.001) and PCI_MBR (p<0.045). VMI_100keV yielded lowest CNR (p≤0.001) and SNR (p≥0.104). In the subjective analysis, VMI_40keV outperformed PCI_MBR for contrast and noise, PCI_MBR scored better than VMI_70keV, and the latter scored better than PCI_HIR for these categories (all p<0.001). PCI_MBR was superior for depiction of soft-plaque and micro-calcifications (p<0.001). VMI_100keV visualized micro-calcifications second best (p<0.001) and matched PCI_MBR for the depiction of macro-calcifications (p>0.999), while VMI_40keV scored second best for depiction of soft-plaque (p<0.020).

CONCLUSIONS

VMI_40keV and VMI_70keV yield better S-/CNR than PCI_HIR and PCI_MBR; however, PCI_MBR visualized arteriosclerotic plaques best, followed by VMI_40keV for depiction of soft-plaque and VMI_100keV for macro- and micro-calcification. Based on the present findings, PCI_MBR on conventional CT and VMI_40keV supplemented by VMI_100keV on SDCT are recommended for the diagnostic assessment of abdominal arteries.

Assessment of arterially hyper-enhancing liver lesions using virtual monoenergetic images from spectral detector CT: phantom and patient experience

PURPOSE

To investigate a benefit from virtual monoenergetic reconstructions (VMIs) for assessment of arterially hyper-enhancing liver lesions in phantom and patients and to compare hybrid-iterative and spectral image reconstructions of conventional images (CI-IR and CI-SR).

METHODS

All imaging was performed on a SDCT (Philips Healthcare, Best, The Netherlands). Images of a non-anthropomorphic phantom with a lesion-mimicking insert (containing iodine in water solution) and arterial-phase images from contrast-enhanced patient examinations were evaluated. VMIs (40-200 keV, 10 keV increment), CI-IR, and CI-SR were reconstructed using different strengths of image denoising. ROIs were placed in lesions, liver/matrix, muscle; signal-to-noise, contrast-to-noise, and lesion-to-liver ratios (SNR, CNR, and LLR) were calculated. Qualitatively, 40, 70, and 110 keV and CI images were assessed by two radiologists on five-point Likert scales regarding overall image quality, lesion assessment, and noise.

RESULTS

In phantoms, SNR was increased threefold by VMI_40keV compared with CI-IR/SR (5.8 ± 1.1 vs. 18.8 ± 2.2, p ≤ 0.001), while no difference was found between CI-IR and CI-SR (p = 1). Denoising was capable of noise reduction by 40%. In total, 20 patients exhibiting 51 liver lesions were assessed. Attenuation was the highest in VMI_40keV, while image noise was comparable to CI-IR resulting in a threefold increase of CNR/LLR (CI-IR 1.3 ± 0.8/4.4 ± 2.0, VMI_40keV: 3.8 ± 2.7/14.2 ± 7.5, p ≤ 0.001). Subjective lesion delineation was the best in VMI_40keV image (p ≤ 0.01), which also provided the lowest perceptible noise and the best overall image quality.

CONCLUSIONS

VMIs improve assessment of arterially hyper-enhancing liver lesions since they increase lesion contrast while maintaining low image noise throughout the entire keV spectrum. These data suggest that to consider VMI screening after arterially hyper-enhancing liver lesions.

[Infectious diseases and injuries of bladder and urinary tract]

Urinary tract infections are the most common infectious diseases in Germany. In most cases clarification does not rely on imaging techniques other than sonography and is made mostly based on clinical symptoms. Computed tomography (CT) and magnetic resonance imaging (MRI) can be used in selected cases to find the cause and detection or exclusion of complications, e.g. recurrent or atypical and complicated courses. The method of choice for clarification of urolithiasis is CT. Using low-dose techniques, detection or exclusion of urinary stones can be achieved with a high sensitivity and specificity as well as an acceptable level of radiation exposure. Native stone CT supplies additional fundamental information that can substantially influence further therapy planning. The diagnosis of ureteral injuries is clinically and radiologically not trivial and clarification is aided by urographic contrast media. The method of CT cystography has an important role in the diagnostics of urinary bladder injuries.

[Oncological diseases and postoperative alterations of the bladder and urinary tract]

In the challenging evaluation of upper urinary tract malignancies multidetector computed tomography (CT) has become the standard imaging method. Cross sectional imaging not only allows the detection and visualization of the tumor itself but also provides nodal and metastasis staging in one examination (one-stop-shop). The majority of urothelial carcinomas are located in the urinary bladder. In this case, CT and more recently magnetic resonance imaging (MRI) can also deliver decisive information regarding TNM classification. A combination of clinical, histological, morphological and functional parameters allows both risk stratification and a targeted therapy based on the individual tumor stage.

Silicone implants--a possible confounder for urinary platinum background concentrations?

INTRODUCTION

Urinary platinum excretion from occupationally unexposed population is very low. Up to now, in Germany, dental noble metal alloys and a platinum based chemotherapy have been identified as reason for elevated urine concentrations. As fabrication of silicone involves platinum as catalyst, this study examines the potential release of platinum from silicone breast implants by quantifying urinary platinum concentration.

METHODS AND RESULTS

Platinum release from three different types of silicone implants into saline solution was measured in a laboratory experiment. It showed a strong increase of platinum concentration during the first 30 min and high platinum concentrations even after 60 h. In the following field study urinary platinum concentrations were determined from 30 women with dental gold alloy restorations and 28 women without such dental inlays. Median platinum concentrations were 5.2 ng/l urine (21.2 ng/g creatinine) for the women with dental gold inlays and 6.0 ng/l urine (5.4 ng/g creatinine) for those without. Compared with the urinary platinum concentrations provided by the German Environmental Survey (GerES) for the general female population the urinary platinum levels of women with silicone implants of the presented study were significantly higher, both for the study groups with and without dental gold alloy inlays.

CONCLUSIONS

Silicone breast implants must be considered as a new confounder and as a further contributor to elevated urinary platinum concentrations in human platinum background reference values of women.

Assessment of renal function after conformal radiotherapy and intensity-modulated radiotherapy by functional 1H-MRI and 23Na-MRI

PURPOSE

Adjuvant radiochemotherapy (RCHT) improves survival of patients with locally advanced gastric cancer. Conventional three-dimensional conformal radiotherapy (3D-CRT) results in ablative doses to a significant amount of the left kidney, while image-guided intensity-modulated radiotherapy (IG-IMRT) provides excellent target coverage with improved kidney sparing. Few long-term results on IMRT for gastric cancer, however, have been published. Functional magnetic resonance imaging (fMRI) at 3.0 T including blood oxygenation-level dependent (BOLD) imaging, diffusion-weighted imaging (DWI) and, for the first time, (23)Na imaging was used to evaluate renal status after radiotherapy with 3D-CRT or IG-IMRT.

PATIENTS AND METHODS

Four disease-free patients (2 after 3D-CRT and 2 after IMRT; FU for all patients > 5 years) were included in this feasibility study. Morphological sequences, axial DWI images, 2D-gradient echo (GRE)-BOLD images, and (23)Na images were acquired. Mean values/standard deviations for ((23)Na), the apparent diffusion coefficient (ADC), and R2* values were calculated for the upper/middle/lower parts of both kidneys. Corticomedullary (23)Na-concentration gradients were determined.

RESULTS

Surprisingly, IG-IMRT patients showed no morphological alterations and no statistically significant differences of ADC and R2* values in all renal parts. Values for mean corticomedullary (23)Na-concentration matched those for healthy volunteers. Results were similar in 3D-CRT patients, except for the cranial part of the left kidney. This was atrophic and presented significantly reduced functional parameters (p = 0.001-p = 0.033). Reduced ADC values indicated reduced cell density and reduced extracellular space. Cortical and medullary R2* values of the left cranial kidney in the 3D-CRT group were higher, indicating more deoxygenated hemoglobin due to reduced blood flow/oxygenation. ((23)Na) of the renal cranial parts in the 3D-CRT group was significantly reduced, while the expected corticomedullary (23)Na-concentration gradient was partially conserved.

CONCLUSIONS

Functional MRI can assess postradiotherapeutic renal changes. As expected, marked morphological/functional effects were observed in high-dose areas (3D-CRT), while, unexpectedly, no alteration in kidney function was observed in IG-IMRT patients, supporting the hypothesis that reducing total/fractional dose to the renal parenchyma by IMRT is clinically beneficial.

[Functional magnetic resonance imaging for evaluation of radiation-induced renal damage]

The diagnosis of radiation-induced (especially chronic) renal alterations/damage is difficult and currently relies primarily on clinical evaluation. The importance of renal diagnostic evaluation will increase continuously due to the increasing number of long-term survivors after radiotherapy. This article evaluates the potentia diagnostic contribution of magnetic resonance (MR) imaging with a focus on functional MRI. The following functional MRI approaches are briefly presented and evaluated: blood oxygenation level-dependent imaging (BOLD), diffusion-weighted imaging (DWI) or diffusion tensor imaging (DTI), MR perfusion measurements and (23)Na imaging. In summary, only DWI and contrast-enhanced MR perfusion currently seem to be suitable approaches for a broader, clinical implementation. However, up to now valid data from larger patient studies are lacking for both techniques in regard to radiation-induced renal alterations. The BOLD and (23)Na imaging procedures have a huge potential but are currently neither sufficiently evaluated with regard to radiation-induced renal alterations nor technically simple and reliable for implementation into the clinical routine.

"Number needed to read"--how to facilitate clinical trials in MR-angiography

Purpose

To evaluate the effect of the number of readers on the statistical results in peripheral MRA.

Materials and methods

40 patients with peripheral arterial occlusive disease were included as a sample dataset in this study, randomly separated into two matched groups with n = 20 patients (group 1—gadobutrol, group 2—gadoterate meglumine) who underwent a continuous table movement MRA of the peripheral vessels at 3 T. Image quality (IQ) of 17 vessel segments was evaluated by 5 independent readers. The effect of the number of readers on significance and statistical power was statistically analyzed.

Results

Image quality in group 1 (gadobutrol) ranks significantly higher compared to group 2 (gadoterade meglumine) with a diagnostic IQ in 97% vs. 78% (p < 0.0001). For the diagnostic/non-diagnostic IQ assessment significance was reached with one reader 1/5 times (20%), with two readers in 4/10 (40%), with three readers in 6/10 (60%), with four readers in 4/5 (80%), with five readers in 1/1 (100%). Power considerations showed considerable gain when increasing the number of readers.

Conclusion

Increasing the number of readers in a diagnostic MRA-study can be used to achieve a higher power or to decrease the number of subjects included with maintained statistical validity.