Manfred Thelen

Pneumonia in Febrile Neutropenic Patients and in Bone Marrow and Blood Stem-Cell Transplant Recipients: Use of High-Resolution Computed Tomography

PURPOSE To obtain statistical data on the use of high-resolution computed tomography (HRCT) for early detection of pneumonia in febrile neutropenic patients with unknown focus of infection. MATERIALS AND METHODS One hundred eighty-eight HRCT studies were performed prospectively in 112 neutropenic patients with fever of unknown origin persisting for more than 48 hours despite empiric antibiotic treatment. Fifty-four of these studies were performed in transplant recipients. All patients had normal chest roentgenograms. If pneumonia was detected by HRCT, guided bronchoalveolar lavage was recommended. Evidence of pneumonia on chest roentgenograms during follow-up and micro-organisms detected during follow-up were regarded as documentation of pneumonia. RESULTS Of the 188 HRCT studies, 112 (60%) showed pneumonia and 76 were normal. Documentation of pneumonia was possible in 61 cases by chest roentgenography or micro-organism detection (54%) (P < 10(-6)). Sensitivity of HRCT was 87% (88% in transplant recipients), specificity was 57% (67%), and the negative predictive value was 88% (97%). A time gain of 5 days was achieved by the additional use of HRCT compared to an exclusive use of chest roentgenography. CONCLUSION The high frequency of inflammatory pulmonary disease after a suspicious HRCT scan (> 50%) proves that pneumonia is not excluded by a normal chest roentgenogram. Given the significantly longer duration of febrile episodes in transplant recipients, HRCT findings are particularly relevant in this subgroup. Patients with normal HRCT scans, particularly transplant recipients, have a low risk of pneumonia during follow-up. All neutropenic patients with fever of unknown origin and normal chest roentgenograms should undergo HRCT.

Bone age determination based on the study of the medial extremity of the clavicle.

Abstract. The development of the medial clavicular epiphysis and its fusion with the clavicular shaft have been a subject of medical research since the second decade of this century. Computed tomography provides the imaging modality of choice in analyzing the maturation process of the sternal end of the clavicle. In a retrospective study, we analyzed normal development in 380 individuals under the age of 30 years. The appearance of an epiphyseal ossification center occurred between ages 11 and 22 years. Partial union was found from age 16 until age 26 years. Complete union was first noted at age 22 years and in 100 % of the sample at age 27 years. Based on these data, age-related standardized age distributions and 95 % reference intervals were calculated. Compared to the experience recorded in the relevant literature, there are several landmarks that show no significant change between different ethnic groups and different periods of publication; these are the onset of ossification, the time span of partial union, and the appearance of complete union. Despite the relatively long time spans of the maturation stages, bone age estimation based on the study of the development of the medial clavicular epiphysis may be a useful tool in forensic age identification in living individuals, especially if the age of the subject is about the end of the second or the beginning of the third decade of life (e. g. in determining the applicability of adult or juvenile penal systems). Another possible use is in identifying human remains whose age is estimated at under 30 years.

Nuclear magnetic resonance imaging with hyperpolarised helium-3

BACKGROUND Magnetic resonance imaging (MRI) relies on magnetisation of hydrogen nuclei (protons) of water molecules in tissue as source of the signal. This technique has been valuable for studying tissues that contain significant amounts of water, but biological settings with low proton content, notably the lungs, are difficult to image. We report use of spin-polarised helium-3 for lung MRI. METHODS A volunteer inhaled hyperpolarised 3He to fill the lungs, which were imaged with a conventional MRI detector assembly. The nuclear spin polarisation of helium, and other noble gases, can be greatly enhanced by laser optical pumping and is about 10(5) times larger than the polarisation of water protons. This enormous gain in polarisation easily overcomes the loss in signal due to the lower density of the gas. FINDINGS The in-vivo experiment was done in a whole-body MRI scanner. The 3He image showed clear demarcation of the lung against diaphragm, heart, chest wall, and blood vessels (which gave no signal). The signal intensity within the air spaces was greatest in lung regions that are preferentially ventilated in the supine position; less well ventilated areas, such as the apices, showed a weaker signal. INTERPRETATION MRI with hyperpolarised 3He gas could be an alternative to established nuclear medicine methods. The ability to image air spaces offers the possibility of investigating physiological and pathophysiological processes in pulmonary ventilation and differences in its regional distribution.

Dynamic contrast‐enhanced myocardial perfusion imaging using saturation‐prepared TrueFISP

To develop and test a saturation‐recovery TrueFISP (SR‐TrueFISP) pulse sequence for first‐pass myocardial perfusion imaging.

Spiral Ct of Bronchial Arteries in Chronic Thromboembolism

Objective Computed tomography study of bronchial artery anatomy and evaluation of dilatation and tortuousity as indicators for pulmonary hypertension and surgical risk in patients with chronic thromboembolism were performed. Materials and Methods We retrospectively reviewed contrast-enhanced, thin section spiral CT scans of 39 patients undergoing pulmonary thromboendarterectomy. Findings were compared with mean pulmonary artery (PA) pressure in all, postoperative mortality in 33, and postoperative CT in 5 patients. Twenty patients without pulmonary hypertension served as controls. Results In the pulmonary hypertension group, 50 bronchial arteries were observed in 30 of 39 patients. Their prevalence was significantly higher than in the control group (p < 0.0001). Their proximal diameter measured ≥1.5 mm in 20 patients (51%); a tortuous course was found in 14 (36%). The correlation between total bronchial artery diameter and mean PA pressure was poor (r = 0.2). Patients with dilated bronchial arteries had a significantly lower risk for postoperative death than patients without (p < 0.05); positive predictive value was 100% and confidence interval 0.79–1.0. Despite normal postoperative PA pressures, bronchial arteries were still visible on follow-up studies. Conclusion The CT depiction of bronchial arteries, dilatation, and tortuousity provides indicators for chronic thromboembolic pulmonary hypertension. Its degree cannot be estimated. Dilated bronchial arteries are a significant predictor for survival of pulmonary thromboendarterectomy.

3He MRI in healthy volunteers: preliminary correlation with smoking history and lung volumes

MRI with hyperpolarized helium‐3 (3He) provides high‐resolution imaging of ventilated airspaces. The first aim of this 3He‐study was to compare observations of localized signal defects in healthy smokers and non‐smokers. A second aim was to describe relationships between parameters of lung function, volume of inspired 3He and signal‐to‐noise ratio. With Ethics Committee approval and informed consent, 12 healthy volunteers (seven smokers and five non‐smokers) were studied. Imaging was performed in a 1.5 T scanner using a two‐dimensional FLASH sequence at 30V transmitter amplitude (TR/TE/α = 11 ms/4.2 ms/<10°). Known amounts of 3He were inhaled from a microprocessor‐controlled delivery device and imaged during single breath‐holds. Images were evaluated visually, and scored using a prospectively defined ‘defect‐index’. Signal‐to‐noise ratio of the images were correlated with localization, 3He volumes and static lung volumes. Due to poor image quality studies of two smokers were not eligible for the evaluation. Smokers differed from non‐smokers in total number and size of defects: the ‘defect‐index’ of smokers ranged between 0.8 and 6.0 (median = 1.1), that of non‐smokers between 0.1 and 0.8 (median = 0.4). Intraindividually, an anteroposterior gradient of signal‐to‐noise ratio was apparent. Signal‐to‐noise ratio correlated with the estimated amount of hyperpolarization administered (r = 0.77), but not with static lung volumes. We conclude that 3He MRI is a sensitive measure to detect regional abnormalities in the distribution of ventilation in clinically healthy persons with normal pulmonary function tests. Copyright

Injuries of the lateral collateral ligaments of the ankle: assessment with MR imaging

Abstract. The aim of this study was to evaluate the ability of MRI to display injuries of the lateral collateral ligamentous complex in patients with an acute ankle distorsion trauma. The MR examinations of 36 patients with ankle pain after ankle distorsion were evaluated retrospectively without knowledge of clinical history, outcome and/or operative findings. The examinations were performed on a 1.5-T whole-body imager using a flexible surface coil. The signs for ligamentous abnormality were as follows: complete or partial discontinuity, increased signal within, and irregularity and waviness of the ligament. The results were compared with operative findings in 18 patients with subsequent surgical repair. Eighteen patients with conservative therapy had a follow-up MR examination after 3 months. There was 1 sprain, 3 partial and 32 complete tears of the anterior talofibular ligament, and 5 sprains, 5 partial, and 7 complete tears of the calcaneofibular ligament. There were no lesions of the posterior talofibular ligament. Compared with surgery, MRI demonstrated in 18 of 18 cases the exact extent of anterior talofibular ligament injuries and underestimated the extent in 2 of 8 cases of calcaneofibular ligament injury. In patients with follow-up MRI after conservative therapy, a thickened band-like structure was found along the course of the injured ligament in 17 of 18 cases. The absence of ligament repair after conservative treatment was confirmed during operative revision in one case. The MRI technique allows for grading of the extent of injury of the lateral collateral ligamentous complex after acute ankle strain. It seems to be suitable for monitoring the healing process after conservative-functional treatment of ligament tears.

Value of contrast-enhanced MR angiography and helical CT angiography in chronic thromboembolic pulmonary hypertension.

The aim of this study was to evaluate the diagnostic value of contrast-enhanced MR angiography (ce MRA) and helical CT angiography (CTA) of the pulmonary arteries in the preoperative workup of patients with chronic thromboembolic pulmonary hypertension (CTEPH). The ce MRA and CTA studies of 32 patients were included in this retrospective evaluation. Image quality was scored by two independent blinded observers. Data sets were assessed for number of patent segmental, subsegmental arteries, and number of vascular segments with thrombotic wall thickening, intraluminal webs, and abnormal proximal to distal tapering. Image quality for MRA/CTA was scored excellent in 16 of 16, good in 11 of 14, moderate in 2 of 5, and poor in no examinations. The MRA/CTA showed 357 of 366 patent segmental and 627 of 834 patent subsegmental arteries. CTA was superior to MRA in visualization of thrombotic wall thickening (339 vs 164) and of intraluminal webs (257 vs 162). Abnormal proximal to distal tapering was better assessed by MRA than CTA (189 vs 16). In joint assessment of direct and indirect signs, MRA and CTA were equally effective (353 vs 355). MRA and CTA are equally effective in the detection of segmental occlusions of the pulmonary arteries in CTEPH. CTA is superior for the depiction of patent subsegmental arteries, of intraluminal webs, and for the direct demonstration of thrombotic wall thickening.

Review article: Percutaneous transhepatic biliary drainage: Experience with 311 procedures

Percutaneous biliary drainage was performed in 296 patients on 311 occasions using a fineneedle puncture technique. In 59%, the procedure served as postoperative decompression, and in 35% for palliation of obstruction, particularly in malignant disease. Postoperative drainage for the management of postoperative complication accounted for 2.5%. In more than 80% of the patients treated, the underlying disease was malignant obstructive jaundice. In 257 retrospectively evaluated patients the following complications were observed: cholangitis (6.6%), sepsis (3.1%), bile leakage (1.6%) with two deaths (0.7%), and subcapsular hematoma and hematoma in the hepatoduodenal ligament (1.2%). Catheter dislocations accounted for 8.5% and were eliminated by the use of self-retaining catheters. In 51 prospectively studied patients pain was encountered in 55% and cholangitis in 11.8%. The procedure is most valuable for complicated biliary obstruction, palliative drainage, and endobiliary manipulations.

Dynamic 19F-MRI of pulmonary ventilation using sulfur hexafluoride (SF6) gas

A new method for dynamic imaging of pulmonary wash‐in and wash‐out kinetics of inhaled sulfur hexafluoride (SF6) gas was developed. Measurements at the fluorine‐19 Larmor frequency were performed in pigs using a gradient echo pulse sequence with 0.5 ms echo time and a measurement time of 9.1 s per image. Dynamic MRI was performed during wash‐in and wash‐out of SF6 gas in mechanically ventilated porcine lungs. A postprocessing strategy was developed for quantitative determination of wash‐out time constants in the presence of noise. Mean wash‐out constants were 4.78 ± 0.48 breaths vs. 4.33 ± 0.76 breaths for left and right lung when ventilation was performed with low tidal volume, and 1.73 ± 0.16 breaths vs. 1.85 ± 0.11 breaths with high tidal volume ventilation. In conclusion, breath‐hold MRI of SF6 gas is feasible in large animals. Moreover, regional wash‐in and wash‐out kinetics of SF6 can be determined noninvasively with this new method. Potential human applications are discussed. Magn Reson Med 45:605–613, 2001.