Juergen F. Schaefer

Total-body MR-imaging in oncology

Although MRI is an effective modality in oncology, state-of-the-art total-body MRI (TB-MRI) in the past was infeasible in the diagnostic work-up, due to the need for repeated examinations with repositioning and separate surface coils to cover all body parts. To overcome this limitation, either a moving table platform in combination with the body-coil or a special designed rolling table platform with one body phased-array coil have been implemented with promising results for both tumor staging and metastases screening. Since 2004, state-of-the-art TB-MR imaging with high spatial resolution has become feasible using a newly developed 1.5 Tesla TB-MRI system with multiple receiver channels. This review gives an overview based on the recent literature as well as our own experience concerning the possibilities, challenges, and limitations of TB-MRI in oncology, emphasizing both oncological staging and early tumor detection in asymptomatic subjects.

Virtual positron emission tomography/computed tomography-bronchoscopy: possibilities, advantages and limitations of clinical application

The aim of this study was to demonstrate the possibilities, advantages and limitations of virtual bronchoscopy using data sets from positron emission tomography (PET) and computed tomography (CT). Twelve consecutive patients with lung cancer underwent PET/CT. PET was performed with F-18-labelled 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (18F-FDG). The tracheobronchial system was segmented with a volume-growing algorithm, using the CT data sets, and visualized with a shaded-surface rendering method. The primary tumours and the lymph node metastases were segmented for virtual CT-bronchoscopy using the CT data set and for virtual PET/CT-bronchoscopy using the PET/CT data set. Virtual CT-bronchoscopy using the low-dose or diagnostic CT facilitates the detection of anatomical/morphological structure changes of the tracheobronchial system. Virtual PET/CT-bronchoscopy was superior to virtual CT-bronchoscopy in the detection of lymph node metastases (P=0.001), because it uses the CT information and the molecular/metabolic information from PET. Virtual PET/CT-bronchoscopy with a transparent colour-coded shaded-surface rendering model is expected to improve the diagnostic accuracy of identification and characterization of malignancies, assessment of tumour staging, differentiation of viable tumour tissue from atelectases and scars, verification of infections, evaluation of therapeutic response and detection of an early stage of recurrence that is not detectable or is misjudged in comparison with virtual CT-bronchoscopy.

Magnetic resonance imaging of lung tissue: influence of body positioning, breathing and oxygen inhalation on signal decay using multi-echo gradient-echo sequences.

Purpose:To assess susceptibility related signal decay in lung tissue and to measure the influence of body positioning, together with inspiration and expiration, as well as oxygen inhalation. T2* maps and line shape maps of lung parenchyma were derived from datasets acquired at 0.2 T and compared with findings at 1.5 T. The line shape maps allow for a visualization of the intravoxel frequency distribution of lung parenchyma. Materials and Methods:A multiecho spoiled gradient-echo sequence with 16 echoes was implemented both on a 0.2 T [repetition time (TR) = 100 milliseconds, echo time (TE)1 = 2.15 milliseconds, &Dgr;TE = 2.94 milliseconds, flip angle 30 degrees] and on a 1.5 T magnetic resonance scanner (TR = 100 milliseconds, TE1 = 1.25 milliseconds, &Dgr;TE = 1.65 milliseconds, flip angle 30 degrees). Sagittal datasets were recorded in 8 healthy volunteers at 0.2 T in supine position under maximal expiration and inspiration and during oxygen breathing. Additional measurements were performed after 20 minutes inside the scanner in supine position and after prone repositioning. In 2 volunteers, further datasets were acquired at 1.5 T. Color-encoded T2* maps and full-width-at-half-maximum (FWHM) maps of the frequency distribution were computed on a pixel-by-pixel basis. T2* maps were generated by mono-exponential fitting and, additionally, with an extended nonexponential fitting approach. The FWHM maps were calculated with a model-free approach using a discrete Fast Fourier Transformation. Results:A notably slower T2* decay was found at 0.2 T (T2*: 5.9–11.8 milliseconds) when compared with 1.5 T (T2*: 1.0–1.4 milliseconds), allowing for the measurement of up to 6 to 8 gradient echoes above the noise level. The T2* maps and the FWHM maps computed from the datasets acquired at 0.2 T allowed regional comparison of the derived parameters. If volunteers were positioned in supine position, expiration resulted in a T2* of 10.9 ± 1.0 milliseconds and a FWHM of 47.1 ± 4.0 Hz in the dorsal lung. Significant changes (P < 0.05) were found, eg, in the ventral lung in expiration (T2*: 7.5 ± 0.8, FWHM: 76.7 ± 11.2) versus dorsal lung in expiration, in the dorsal lung in inspiration (T2*: 8.4 ± 1.0, FWHM: 67.8 ± 12.5) versus dorsal lung in expiration, in the dorsal lung during oxygen breathing (T2*: 8.7 ± 1.1, FWHM: 52.2 ± 5.2) versus dorsal lung while breathing room air, and in the dorsal lung in prone position (T2*: 8.5 ± 0.6, FWHM: 67.0 ± 9.2) versus dorsal lung in supine position. Conclusion:The proposed method allows for the computation of color-encoded T2* maps and FWHM maps of lung parenchyma in good image quality using datasets acquired at 0.2 T. The technique is robust and sensitive to physiological changes of lung magnetic resonance properties, eg, due to the type of body positioning or oxygen breathing.

Primary Repair of Esophageal Atresia in Extremely Low Birth Weight Infants: A Single-Center Experience and Review of the Literature

Background: Advances in neonatal intensive care have led to an increased survival of very low birth weight (VLBW, <1,500 g) and extremely low birth weight infants (ELBW, <1,000 g). Several abnormalities may occur in these children, e.g. esophageal atresia (EA), imperforate anus or abdominal wall defects. Correction of EA is often performed as a staged procedure in this group of patients. Objectives: To evaluate the feasibility of a primary correction of EA in 4 ELBW and VLBW infants. Methods: Between 2002 and 2004, 4 infants below 1,200 g were operated on in our institution with a diagnosis of EA with lower tracheoesophageal fistula. Birth weight ranged from 780 to 1,120 g (median: 920 g), gestational age from 28 to 30 weeks. Treatment included closure of the tracheoesophageal fistula and primary anastomosis of the esophagus in a one-step procedure. Results: Primary correction of EA and fistula repair was feasible in all children. Initially, all children had a normal passage of the esophagus as observed in barium swallowing. One child suffering from a leakage of the anastomosis was managed conservatively. Another infant suffered from spontaneous small bowel perforation 6 days after surgery, which was treated by laparotomy. One child developed stenosis of the esophagus and required a single dilatation 14 months after initial treatment. In the 4th child, a type II cleft syndrome was subsequently diagnosed, requiring secondary cleft repair together with semifundoplication. This child eventually died from cytomegalovirus pneumonia. Conclusions: Primary repair of EA and closure of a tracheoesophageal fistula is technically feasible and offers a good treatment option for ELBW and VLBW infants. Staged repair can be avoided. Infants with cleft syndrome are still a diagnostic and therapeutic challenge.

Outcome of augmentation cystoplasty and bladder substitution in a pediatric age group.

OBJECTIVE Aim of the study was to evaluate the outcome of augmentation cystoplasty and bladder substitution in a pediatric age group. METHODS Patient records of all children who underwent reconstructive bladder surgery between October 1999 and November 2007 were reviewed. Additionally, standardized interviews were performed to evaluate the postoperative outcome. RESULTS Augmentation cystoplasty and bladder substitution were performed in 19 and 6 patients, respectively. 21 patients underwent continent catheterizable vesicostomy. Postoperative urodynamics revealed a significant increase in bladder volume (median 400 ml) as well as a significant improvement in bladder compliance (median 13.5 ml/cmH2O). 90% of the patients were reported to be socially continent. Renal function remained stable in 95% and decreased in 5% of the children. Major complications were lower urinary tract calculi (39%), stricture or insufficiency of the continent vesicostomy (28%), and intestinal obstruction (9%). No malignancies associated to bladder augmentation or substitution were detected yet. CONCLUSION Augmentation cystoplasty and bladder substitution preserve renal function and provide urinary continence in most children with intractable lower urinary tract disease. However, the procedures remain associated with numerous complications.

Dynamic magnetic resonance nephrography: is saturation recovery TrueFISP advantageous over saturation recovery TurboFLASH?

Purpose:In this volunteer study, 2 navigator-gated strongly T1-weighted saturation-recovery (SR) sequences, a turbo fast low angle shot (TurboFLASH) and a new true fast imaging in steady precession (TrueFISP) readout technique, were compared for suitability in dynamic magnetic resonance nephrography. Materials and Methods:Ten healthy volunteers (mean age 26.1 ± 3.6) were equally divided into 2 subgroups. After bolus-injection of 3.75 mL of gadobutrol (approximately 0.05 mmol/kg body weight), slightly obliqued coronal single-slice images of the kidneys were recorded every 4–5 seconds during free breathing using 1 of the 2 sequences. Time-intensity curves were determined from manually drawn regions-of-interest over the kidney parenchyma. Both sequences were subsequently evaluated with regard to linearity of signal, signal to noise ratio (SNR), and time-dependent behavior of signal intensity curves. Results:The TurboFLASH readout showed better linearity of the signal behavior as compared with the TrueFISP technique (TurboFLASH: no deviation from linearity down to T1 = 400 milliseconds; TrueFISP at T1 = 700 milliseconds: 12% deviation, at T1 = 400 milliseconds: 19%). The time-intensity curves of the TrueFISP sequence exhibited distinctly lower variability than the TurboFLASH approach. The SNR increased with TrueFISP by 3.4 ± 0.5-fold for native renal parenchyma and by 3.3 ± 0.9 for contrast-enhanced renal parenchyma. For split renal function evaluation, the linear regression to the signal increase in the first minutes after the first pass could be performed with higher reliability using the TrueFISP technique (increase of correlation coefficient by 17.1%). Conclusion:A SR navigator-gated TrueFISP sequence seems most favorable for dynamic magnetic resonance nephrography due to the high signal yield and low curve variability.

Vascular encasement as element of risk stratification in abdominal neuroblastoma

BACKGROUND Vascular encasement of major vessels has been introduced as element of image defined risk factors (IDRF) for stratification of abdominal neuroblastoma. Some subgroups of this tumor entity are still subject of discussion regarding surgical approach and radicality. Aim of this study was to analyse a cohort of related patients. PATIENTS AND METHODS Children operated on for neuroblastoma with encasement of major abdominal vessels (April 2002-April 2009) were retrospectively evaluated regarding surgical procedures, intra- and postoperative complications, and outcome. RESULTS There were 18 patients with abdominal NB and encasement of major vessels. Mean age at operation was 43.5 months (2.5-113), mean operation time was 228 minutes (157-428). Complete macroscopic tumor resection was realised in 14 children. Vascular reconstruction was necessary in 5 patients. Tumor progression/relapses requiring further operation occurred in 3 patients. Major postoperative complications were 1 loss of unilateral renal function with subsequent nephrectomy, 1 renal vein thrombosis (operative revision), 1 renal artery embolism (operative revision), and 1 ureteral obstruction (stenting). Mean follow up was 34.8 months (2-78). CONCLUSIONS Vascular encasement as part of IDRF is a valuable tool for stratification of abdominal NB. Surgery of NB with vascular encasement includes divers and complex procedures. Children seem to benefit from complete tumor resection or at least relevant tumor reduction although operations can mean a relevant strain for the patients.

Treatment of benign bone defects in children with silicate-substituted calcium phosphate (SiCaP).

BACKGROUND In children with benign bone defects, various treatment options are recommended. Whether these defects should be curetted, osteosynthetically stabilized and/or filled with allogenic or synthetic bone material is still a matter of controversy. METHODS The reported study presents preliminary results of five children with benign bone lesions of the lower extremity. Curettage and filling of the defect with a commercially available silicate-substituted calcium phosphate (SiCaP) (Actifuse® by ApaTech Ltd., Elstree, United Kingdom) was performed. Patients were followed-up in the outpatient clinic. The healing process was assessed according to the clinical and radiological criteria. RESULTS Clinical and radiological follow-up showed uneventful healing without intraoperative and short-term complications. All patients were capable of full weight bearing after a few weeks and currently did not experience any decreased range of movement among adjacent joints. Growth disturbances did not occur. In all patients increasing cancellous bone reconstruction of the defect, without signs of osteolysis could be shown radiologically. CONCLUSION SiCaP represents a good and safe alternative to hitherto existing therapies in the management of defined symptomatic benign bone defects in the pediatric age group.

Comparison between High-Resolution CT and MRI Using a Very Short Echo Time in Patients with Cystic Fibrosis with Extra Focus on Mosaic Attenuation

Background: It would be beneficial to establish pulmonary MRI as a complementary approach to CT for direct visualization of mosaic perfusion, bullae, and emphysema in patients with cystic fibrosis. Objectives: The purpose of this study was to compare both modalities, CT and MRI, using the Helbich-Bhalla score with a special focus on reliable detection of a mosaic pattern. Methods: Out of 51 patients examined by MRI on a 1.5-Tesla system during a period of 2 years, 19 patients were scheduled for additional low-dose CT in a clinical context. The MRI protocol comprised a gradient echo (GRE) sequence with a very short echo time (TE = 0.8 ms) in inspiration and expiration, a 3-D GRE sequence in breath hold, and a fast spin echo sequence with respiration and ECG triggering. MDCT was carried out in inspiration and adapted to body weight using 100 or 120 kV, 30-60 mA, 1- and 3-mm slice thicknesses, as well as low and high kernels. Additionally incremental slices in 3 positions were recorded in expiration for distinct detection of air trapping. CT and MRI analyses were performed by two radiologic readers in consensus unaware of the clinical parameters. The Helbich-Bhalla score of both examinations was correlated. Mean difference and accordance were assessed in each category. Results: There was a strong correlation between CT and MRI (R = 0.87, p < 0.01). The mean Helbich-Bhalla score for CT was 12.2 (range 1-18) and for MRI it was 11.7 (range 2-19). The mean difference was 0.5 points. Besides this strong correlation for findings (bronchiectasis, mucus plugging, peribronchial thickening, and consolidation) with a prolonged T2 TE in MRI, we could also state a qualitative agreement of 95-100% in the categories with short T2 and low signal intensity in MRI as emphysema, bullae, and mosaic perfusion. Conclusions: These results suggest that in our patient group none of the relevant findings were missed by MR imaging and reading.

Synergistic effect between iron and gadolinium in MRI.

Different combinations of iron glycerophosphate (Fe) and gadolinium‐diethylene triamine pentaacetic acid (DTPA) (Gd) were imaged with a three‐dimensional (3D) gradient‐recalled echo (GRE), a 2D GRE, and a HASTE sequence on a 1.5‐T MR scanner. A combination of Fe and Gd results in a synergistic effect, which improves the signal gain for selective 3D imaging of the colon and simultaneously decreases the endoluminal signal on the HASTE and 2D GRE images for better visualization of water and Gd‐enhanced structures in the gut wall. J. Magn. Reson. Imaging 2000;12:358–362.