Algorithmic transparency and interpretability measures improve radiologists' performance in BI-RADS 4 classification

OBJECTIVE

To evaluate the perception of different types of AI-based assistance and the interaction of radiologists with the algorithm's predictions and certainty measures.

METHODS

In this retrospective observer study, four radiologists were asked to classify Breast Imaging-Reporting and Data System 4 (BI-RADS4) lesions (n = 101 benign, n = 99 malignant). The effect of different types of AI-based assistance (occlusion-based interpretability map, classification, and certainty) on the radiologists' performance (sensitivity, specificity, questionnaire) were measured. The influence of the Big Five personality traits was analyzed using the Pearson correlation.

RESULTS

Diagnostic accuracy was significantly improved by AI-based assistance (an increase of 2.8% ± 2.3%, 95 %-CI 1.5 to 4.0 %, p = 0.045) and trust in the algorithm was generated primarily by the certainty of the prediction (100% of participants). Different human-AI interactions were observed ranging from nearly no interaction to humanization of the algorithm. High scores in neuroticism were correlated with higher persuasibility (Pearson's r = 0.98, p = 0.02), while higher consciousness and change of accuracy showed an inverse correlation (Pearson's r = -0.96, p = 0.04).

CONCLUSION

Trust in the algorithm's performance was mostly dependent on the certainty of the predictions in combination with a plausible heatmap. Human-AI interaction varied widely and was influenced by personality traits.

KEY POINTS

• AI-based assistance significantly improved the diagnostic accuracy of radiologists in classifying BI-RADS 4 mammography lesions. • Trust in the algorithm's performance was mostly dependent on the certainty of the prediction in combination with a reasonable heatmap. • Personality traits seem to influence human-AI collaboration. Radiologists with specific personality traits were more likely to change their classification according to the algorithm's prediction than others.

Lung nodule detection in chest X-rays using synthetic ground-truth data comparing CNN-based diagnosis to human performance

We present a method to generate synthetic thorax radiographs with realistic nodules from CT scans, and a perfect ground truth knowledge. We evaluated the detection performance of nine radiologists and two convolutional neural networks in a reader study. Nodules were artificially inserted into the lung of a CT volume and synthetic radiographs were obtained by forward-projecting the volume. Hence, our framework allowed for a detailed evaluation of CAD systems' and radiologists' performance due to the availability of accurate ground-truth labels for nodules from synthetic data. Radiographs for network training (U-Net and RetinaNet) were generated from 855 CT scans of a public dataset. For the reader study, 201 radiographs were generated from 21 nodule-free CT scans with altering nodule positions, sizes and nodule counts of inserted nodules. Average true positive detections by nine radiologists were 248.8 nodules, 51.7 false positive predicted nodules and 121.2 false negative predicted nodules. The best performing CAD system achieved 268 true positives, 66 false positives and 102 false negatives. Corresponding weighted alternative free response operating characteristic figure-of-merits (wAFROC FOM) for the radiologists range from 0.54 to 0.87 compared to a value of 0.81 (CI 0.75-0.87) for the best performing CNN. The CNN did not perform significantly better against the combined average of the 9 readers (p = 0.49). Paramediastinal nodules accounted for most false positive and false negative detections by readers, which can be explained by the presence of more tissue in this area.

Coronary calcium scoring assessed on native screening chest CT imaging as predictor for outcome in COVID-19: An analysis of a hospitalized German cohort

BACKGROUND

Since the outbreak of the COVID-19 pandemic, a number of risk factors for a poor outcome have been identified. Thereby, cardiovascular comorbidity has a major impact on mortality. We investigated whether coronary calcification as a marker for coronary artery disease (CAD) is appropriate for risk prediction in COVID-19.

METHODS

Hospitalized patients with COVID-19 (n = 109) were analyzed regarding clinical outcome after native computed tomography (CT) imaging for COVID-19 screening. CAC (coronary calcium score) and clinical outcome (need for intensive care treatment or death) data were calculated following a standardized protocol. We defined three endpoints: critical COVID-19 and transfer to ICU, fatal COVID-19 and death, composite endpoint critical and fatal COVID-19, a composite of ICU treatment and death. We evaluated the association of clinical outcome with the CAC. Patients were dichotomized by the median of CAC. Hazard ratios and odds ratios were calculated for the events death or ICU or a composite of death and ICU.

RESULTS

We observed significantly more events for patients with CAC above the group's median of 31 for critical outcome (HR: 1.97[1.09,3.57], p = 0.026), for fatal outcome (HR: 4.95[1.07,22.9], p = 0.041) and the composite endpoint (HR: 2.31[1.28,4.17], p = 0.0056. Also, odds ratio was significantly increased for critical outcome (OR: 3.01 [1.37, 6.61], p = 0.01) and for fatal outcome (OR: 5.3 [1.09, 25.8], p = 0.02).

CONCLUSION

The results indicate a significant association between CAC and clinical outcome in COVID-19. Our data therefore suggest that CAC might be useful in risk prediction in patients with COVID-19.

A robust convolutional neural network for lung nodule detection in the presence of foreign bodies

Lung cancer is a major cause of death worldwide. As early detection can improve outcome, regular screening is of great interest, especially for certain risk groups. Besides low-dose computed tomography, chest X-ray is a potential option for screening. Convolutional network (CNN) based computer aided diagnosis systems have proven their ability of identifying nodules in radiographies and thus may assist radiologists in clinical practice. Based on segmented pulmonary nodules, we trained a CNN based one-stage detector (RetinaNet) with 257 annotated radiographs and 154 additional radiographs from a public dataset. We compared the performance of the convolutional network with the performance of two radiologists by conducting a reader study with 75 cases. Furthermore, the potential use for screening on patient level and the impact of foreign bodies with respect to false-positive detections was investigated. For nodule location detection, the architecture achieved a performance of 43 true-positives, 26 false-positives and 22 false-negatives. In comparison, performance of the two readers was 42 ± 2 true-positives, 28 ± 0 false-positives and 23 ± 2 false-negatives. For the screening task, we retrieved a ROC AUC value of 0.87 for the reader study test set. We found the trained RetinaNet architecture to be only slightly prone to foreign bodies in terms of misclassifications: out of 59 additional radiographs containing foreign bodies, false-positives in two radiographs were falsely detected due to foreign bodies.

Acceleration of chemical shift encoding-based water fat MRI for liver proton density fat fraction and T2* mapping using compressed sensing

Objectives

To evaluate proton density fat fraction (PDFF) and T2* measurements of the liver with combined parallel imaging (sensitivity encoding, SENSE) and compressed sensing (CS) accelerated chemical shift encoding-based water-fat separation.

Methods

Six-echo Dixon imaging was performed in the liver of 89 subjects. The first acquisition variant used acceleration based on SENSE with a total acceleration factor equal to 2.64 (acquisition labeled as SENSE). The second acquisition variant used acceleration based on a combination of CS with SENSE with a total acceleration factor equal to 4 (acquisition labeled as CS+SENSE). Acquisition times were compared between acquisitions and proton density fat fraction (PDFF) and T2*-values were measured and compared separately for each liver segment.

Results

Total scan duration was 14.5 sec for the SENSE accelerated image acquisition and 9.3 sec for the CS+SENSE accelerated image acquisition. PDFF and T2* values did not differ significantly between the two acquisitions (paired Mann-Whitney and paired t-test P>0.05 in all cases). CS+SENSE accelerated acquisition showed reduced motion artifacts (1.1%) compared to SENSE acquisition (12.3%).

Conclusion

CS+SENSE accelerates liver PDFF and T2*mapping while retaining the same quantitative values as an acquisition using only SENSE and reduces motion artifacts.

Volume versus standard coils in the treatment of intracranial aneurysms

BACKGROUND

Volume coils were developed to improve occlusion rates of intracranial aneurysms. Previous studies have shown increased packing density and comparable occlusion rates, but subgroup analyses of aneurysm size have not been carried out.

OBJECTIVE

To evaluate the safety and efficacy of the Penumbra Coil 400 (PC400) system in treating intracranial aneurysms compared with standard diameter coils.

METHODS

A monocentric retrospective case review of 260 aneurysms in 233 patients was carried out. In 37 aneurysms the PC400 system was used, while 223 aneurysms were treated with conventional coils. Previously treated aneurysms and aneurysms treated with flow diverters were excluded. Aneurysm and procedure characteristics, packing density, postprocedural and follow-up occlusion grades as well as coil compaction were evaluated.

RESULTS

Aneurysms treated with PC400 coils had higher volume (218.9 vs 47.1 mm(3), p<0.001), wider necks (3.0 vs 2.5 mm, p=0.005), and greater dome/neck ratio (2.0 vs 1.6, p=0.001) in comparison with aneurysms treated with conventional coils. Compared with controls, in the PC400 group we achieved higher packing densities (43.2% vs 34.4%, p<0.001; in aneurysms ≥7 mm 42.2% vs 27.8%, p<0.001). On follow-up angiography we observed less coil compaction (23.8% vs 64.3%, p=0.003) and less aneurysm recurrence (14.3% vs 40.5%, p=0.046) in aneurysms ≥7 mm when using the PC400 system.

CONCLUSIONS

Use of the PC400 system as opposed to conventional coils suggests that the PC400 system is safe and effective in treating intracranial aneurysms. Despite having been applied in a potentially more difficult-to-treat group, the use of PC400 was associated with less coil compaction and aneurysm recurrence in aneurysms ≥7 mm.

[Long iliac artery occlusions: Feasibility, short- and mid-term outcome]

PURPOSE

It was the aim of the following study to determine the feasibility of the recanalization of long occlusions in iliac arteries and to establish its patency rate.

MATERIAL AND METHODS

We retrospectively evaluated the data of 23 patients (15 male and 8 female) with occlusions of the iliac arteries with a mean length of 12 cm (range: 9-15 cm). The occlusions were situated either in the common iliac artery (CIA) (n = 3), in the external iliac artery (EIA) (n = 12) or in both CIA and EIA (n = 7). In one patient three vessels, the common femoral artery included, were involved. The recanalization procedure was performed with wire and catheter from retrograde and, in case of a failure, from antegrade in a cross-over technique.

RESULTS

Recanalization succeeded in all patients. Technical success defined as residual stenosis < 30 % was seen in 20 of 23 patients. Early reocclusions were seen in four patients, in three of whom, the stent dilatation had been incomplete. Late reocclusions were observed in three patients, one of whom had already had early reocclusion. The reason was stent breakage in one, stent dehiscence in the second and restenosis in the third patient. All of the patients with reocclusion either early or late, had received covered stents. In four patients restenosis developed within 30 months: It was successfully treated by ballon dilatation or stent. Embolism during the recanalization procedure was observed in six patients. Embolism was observed on the ipsilateral side in five, and on the contralateral side in one patient. In each patient who had experienced embolism, balloon dilatation had been performed before stent implantation.

CONCLUSION

1) There is some evidence that the recanalization of long iliac artery occlusions is feasible. 2) The main reason for early and late reocclusions is either rest stenosis or restenosis. 3) Covered stents should only be used in selected cases. 4) Primary stenting is the treatment of choice in order to prevent embolism.

Anterior disk displacement of the temporomandibular joint. Significance of clinical signs and symptoms in the diagnosis

In order to examine the diagnostic significance of typical clinical symptoms in temporomandibular joint (TMJ) disorders for diagnosis of anterior disk displacement, clinical findings were compared with the degree of disk displacement in 84 TMJs of 59 patients with TMJ disorders, who were examined clinically and by means of magnetic resonance imaging (MRI). The control group consisted of 31 subjects with no TMJ symptoms. No significant correlation between the degree of anterior disk displacement and palpation pain of the masticatory muscles or clicking/crepitus of the TMJ could be found. Joint clicking was observed in 65% of patients with TMJ symptoms in normal disk position (NDP). The percentage of joint clicking was almost the same in patients with anterior disk displacement with reposition (ADWR) (68%). There were significant correlations between active mouth opening and disk position as well as between a history of pain and disk position. Patients with NDP and ADWR had almost identical mouth opening values: 48 (+/- 5) mm and 46 (+/- 5) mm respectively. In contrast to these groups the mean values decreased significantly to 42 (+/- 6) mm in patients with anterior disk displacement without reposition (ADWOR). There were no significant correlations between occlusal findings (centric relation and habitual relation, early occlusal contacts, abrasion facets) and disk position when viewed either collectively or individually.

[The recording of parenchymal lung changes in smokers by high-resolution computed tomography]

PURPOSE

It has been the aim of the study to assess parenchymal changes in the lung with high-resolution CT in healthy heavy, moderate, and non-smokers.

MATERIAL AND METHODS

We prospectively evaluated CT changes in 42 healthy heavy smokers (gr. (group) 2, > or = 30 pack-years), 40 moderate smokers (gr. 1, < 30 pack-years) and 38 non-smokers (gr. 0). For CT-analysis, we used a visual grading and computer-based analysis system (Mipron, Kontron GmbH, Munich, Germany).

RESULTS

Productive cough, dyspnoea and chronic bronchitis were more common in smokers than in non-smokers (p < 0.05). Pathological CT-findings were found in 6/38 non-smokers and in 71/82 smokers (p < 0.01). In particular, in smokers (gr. 1 [%], gr. 2 [%]) the following pathological findings were found: dystelectases in dependent lung areas in 50% (62, 38), centrilobular emphysema in 44% (43, 20), pleural thickening in 38% (38, 38), panlobular emphysema in 36% (52, 20), ground-glass pattern in 33% (36, 30), paraseptal emphysema in 21% (31, 10), prominent or thickened interlobular septa in 18% (29, 8) and centrilobular micronodules in 13% (10, 18). Computer-based analysis demonstrated thicker bronchial walls in smokers as compared to non-smokers.

CONCLUSION

Although feeling healthy, smokers demonstrate various parenchymal abnormalities in the lung. In smokers, subpleural dystelectases, centrilobular and panlobular emphysema are dependent on cigarette consumption, ground glass pattern, centrilobular micronodules, pleural thickening and bronchial wall thickening are independent on cigarette consumption.

[Temporomandibular joint morphology and morphometric findings in relation to degree of disk displacement. Comparative magnetic resonance tomography studies]

In order to evaluate magnetic resonance imaging (MRI) changes in correlation with different degrees of internal derangement of the temporomandibular joint, we evaluated 117 joints of 59 symptomatic patients and 31 volunteers. Data analysis included morphologic and morphometric characteristics. Sixteen joints (19%) were considered normal, 40 demonstrated anterior displacement with reduction (47%) and 27 anterior displacement without reduction (32%). In three of the volunteers anterior displacement with reduction was noted. Advancing anterior position of the disk was associated with reduced ability to open the mouth, progressive deformity and shortening of the disk, thinning of the bilaminar zone, regressive and proliferative bony changes of the condyle, reduced translatory movement of the disk and condyle, thinning of joint space, cranial and dorsal displacement of the condyle and flattening of the slope of the tuberculum. In addition to alterations in condylar and disk morphology, MRI can demonstrate various additional measurable changes that correlate well with the degree of anterior disk displacement.

Hemodialysis fistulas and grafts: use of cutting balloons to dilate venous stenoses

To evaluate percutaneous transluminal angioplasty (PTA) with a cutting balloon performed in stenosed hemodialysis fistulas and grafts, 19 venous lesions in 15 patients were treated with a cutting balloon with an inflated diameter of 3-6 mm. The grade of stenosis ranged from 40% to 90% (mean, 65% +/- 15 [standard deviation]). Cutting PTA was performed before conventional PTA in seven patients and was followed with conventional PTA with larger balloons in seven patients. The balloon expanded completely in all patients, and no balloon waist remained. The mean grade of stenosis decreased to 14% +/- 9. Cutting PTA increased the technical success of balloon dilation of hemodialysis fistulas and grafts.

[Pulmonary manifestations in rheumatoid arthritis: high-resolution computed tomography in correlation with the skeletal changes and the laboratory chemical changes]

PURPOSE

It has been the aim of the following study to evaluate pulmonary changes in rheumatoid arthritis with high-resolution CT and to assess their correlation with joint manifestation and laboratory parameters.

MATERIAL AND METHODS

The authors prospectively performed computed tomography (CT) in 83 patients with rheumatoid arthritis and graded pulmonary changes for frequency and severity. Included were patients with 6-7/7 ARA, BSR > 25/1 min and mean disease duration of 12 years (range, 1-44). Data of medical and drug histories, smoking habits, blood levels of rheumatoid factor (RF), antinuclear antibodies (ANA) and C-reactive protein as well as the degree of joint involvement were taken into account.

RESULTS

58 patients (70%) had pathological CT scans showing the following abnormalities: interlobular thickening (44.5%), intralobular thickening (34%), nonseptal linear attenuation (35%), nodular or linear pleural thickening (32.5%), ground-glass pattern (19%), centrilobular nodules (13%), honeycombing (13%) and bronchiolectasis (9%). Intralobular thickening, honeycombing and pleural thickening were associated with a higher degree of joint manifestation; pleural thickening, honeycombing and ground-glass pattern were associated with a higher level of rheumatoid factor. There was no relationship between pulmonary changes and either the duration of the disease, antinuclear antibodies (ANA) or C-reactive protein.

CONCLUSION

CT may be a useful noninvasive tool for recognition of RA-associated lung disease. Interstitial lung changes are frequent and they are independent of the duration of the disease. Pulmonary interstitial changes are more frequent and more severe in RF-positive patients and in case of more severe joint involvement.

Anterior disc displacement without reduction in the temporomandibular joint: MRI and associated clinical findings

To determine the value of MRI in temporomandibular joint (TMJ) disorders, the data of MRI-proven anterior disc dislocation without reduction (ADWOR) were correlated with clinical history and clinical data. MRI demonstrated degenerative bony changes and a reduced sagittal diameter of the condyle, a variable degree of disc deformation, and a thinned bilaminar zone in each of the joints with ADWOR, which clearly differed from patients with anterior disc dislocation with reduction (ADWR) (P = .01) and normal disc position (NDP) (P < .001). Of 59 patients and 83 TMJs that had been investigated in a 2-year period, as shown by MRI, 22 patients (27 TMJs) had ADWOR (32%), 16 joints had NDP (19%), and 40 patients had ADWR (49%). In patients with ADWOR, the clinical history revealed pain in either of the joints and/or cervical or masticatory muscles in 25 (93%) joints. Clinical investigation revealed various abnormalities in 22 joints; five of those presented without any pathologic clinical finding. Mouth opening was unlimited in nine patients (47%), palpation of the muscles of mastication was painless in 13 patients (52%), and joint noises during mouth opening or closing were noted in 14 patients (56%). According to clinical histories, four patients were suspected to have become symptomatic only after dental treatment. ADWOR is difficult to diagnose with clinical methods alone. The indication for MRI evaluation of the TMJ should be extended for asymptomatic patients with a history of limitation in mouth opening and pathologic x-ray morphology of the condyle. Because symptoms may arise after dental treatment in these patients, aggravation of internal derangement may be avoided by careful handling.

[Disk displacement of the temporomandibular joint: correlation of magnetic resonance tomography and clinical findings]

PURPOSE

To evaluate the value of magnetic resonance imaging (MRI) in symptomatic patients with different degrees of internal derangement.

MATERIAL AND METHODS

We prospectively investigated 117 temporomandibular joints (TMJ) of 59 symptomatic patients and 31 asymptomatic volunteers and correlated this with clinical parameters.

RESULTS

There was a positive correlation between the degree of internal derangement and deformity of the disc, maximal mouth opening, signal intensity of the posterior band, thickness of the bilaminar zone, proliferative bony changes, size of the condyle and reduced translation movement of the condyle, which in addition moved upward and backward. Patients most often complained of pain which was dependent on the degree of disc displacement and condylar changes. Clinical parameters were found to be inaccurate in predicting disc displacement.

CONCLUSION

Patients with internal derangement of the temporomandibular joint may be asymptomatic. Patients history may give the only pointer to the disorder.

Hydrodynamic thrombectomy of haemodialysis grafts and fistulae: results of 51 procedures

PURPOSE

To describe efficacy of hydrodynamic thrombectomy for occluded dialysis native and graft fistulae in 51 instances.

MATERIALS AND METHODS

Fifty-one hydrodynamic thrombectomies of 34 native and graft a-v fistulae were performed. There were 32 thrombectomies in PTFE grafts and 19 procedures in native Brescia-Cimino fistulae. Multiple thrombectomies were performed in 11 of 34 fistulae. The estimated occlusion time was 36.4+/-22 h. The length of the occluded segment ranged from 2 to 50 cm (mean 28.8 cm). In all cases, a 7 F hydrodynamic thrombectomy catheter was used. Double-cannulation technique was used for graft fistulae, single-cannulation for native fistulae. Additionally, balloon dilatation was performed in all 51 cases, stenting in six, and aspiration thrombectomy in two cases.

RESULTS

Arterialized flow was re-established by hydrodynamic thrombectomy and PTA in 43 of 51 cases (84%). By additional use of other techniques, technical success improved to 46 of 51 procedures (90%). Early re-thrombosis occurred in six cases within 24 h of thrombectomy (11%). Clinical success was achieved in 39 of 46 technically successful cases (85%). Cumulative patency was calculated at 63% after 1 week, 57% after 1 month, 48% after 3 months, 37% after 6 months, and 32% after 12 months. Patency of native fistulae after thrombectomy was better than patency of grafts.

CONCLUSIONS

Hydrodynamic thrombectomy is an effective percutaneous technique for declotting haemodialysis fistulae and grafts recently thrombosed.

[Findings in the panoramic tomogram in orthodontic patients with functional disorders]

In our study of 107 patients, for whom data derived from clinical functional analysis, axiography and, in part magnet resonance imaging, were present, we were able to show that in routine orthodontic diagnosis the use of panoramic X-ray in the normal course of a general examination of the mandibular joint can also provide important indications of the presence of cranio-mandibular disorders. The panoramic X-ray revealed that in patients with Angle class II and front deep and open bite there were significantly mor changes in the form of the condyles. A definite morphologic finding of a retracted fovea pterygoidea was found frequently in patients with anterior disk replacement with or without reduction. Lastly, the panoramic X-ray showed that a change in form of the condyles, with in some cases a serious arthrosis, occurs significantly most frequent in patients with anterior displacement without reduction.

[High-resolution computed tomography (HRCT) of the lung in collagenoses: a prospective study of 73 patients]

To determine pulmonary features of collagenous vascular diseases as assessed by high resolution computed tomography (HRCT) we performed a prospective study of 73 consecutive patients, 44 with rheumatoid arthritis (ra), 11 with progressive systemic sclerosis (pss), 8 with systemic lupus erythematosus (sle), 5 with sjögren's syndrome, 3 with dermato-/polymyositis and 2 with mixed connective-tissue disease. Pathological lung changes were demonstrated in 70% of patients with ra, 91% with pss, 63% with sle and 60% with the rest. HRCT features included: intralobular thickening (48%) with a predominance in posterior lower and middle lung areas, pleural thickening (48%) with a predominance in upper lung areas, prominent interlobular septa (37%), subpleural lines (33%), parenchymal bands (33%) with a predominance in lower and anterior lung areas, honeycombing (33%), ground glass pattern (29%) with a predominance in upper and middle, micronodules (18%) with a predominance in upper lung areas and bronchiectasis (14%). HRCT is an important means for the assessment of lung changes associated with collagenous vascular diseases and a definite diagnosis is possible in most cases.

[Ultrasound screening of vesico-uretero-renal reflux]

A prospective study of detecting vesicoureteric reflux (VUR) by ultrasound is to be presented. In case of reflux, gas bubbles can be seen in the renal pelvis during the filling phase of a gas cystogram and during micturition, utilizing ultrasound as the imaging modality. In children under two years 52 sonographic reflux studies were performed and compared with radiographic voiding cystourethrograms (VCUG). All higher grade VUR (grades II-IV) have been detected by our method.

Gadolinium-enhanced T1-weighted versus T2-weighted imaging of scrotal disorders: is there an indication for MR imaging?

To evaluate the use of gadopentetate dimeglumine in magnetic resonance (MR) imaging of scrotal disorders, the clinical, ultrasound, and MR imaging data of 29 patients (age range, 19-75 years) with various intra- and extratesticular disorders were retrospectively analyzed. T1- and T2-weighted spin-echo images (T1-T2 group) were compared with T1-weighted spin-echo images before and after intravenous administration of gadopentetate dimeglumine (T1-Gd group). A receiver operating characteristic (ROC) analysis of the findings was undertaken. Better contrast between tumor and parenchyma and a clearer demonstration of the tunica albuginea were noted in the T1-T2 group (although not of diagnostic relevance). ROC analysis revealed no differences between the two imaging groups in the diagnosis of tumor, trauma, hydrocele, or hemorrhage; however, epididymitis was diagnosed more easily with contrast enhancement (0.8834 vs 0.7759, P = .04) and the diagnosis of orchitis was expressed more strongly (0.8221 vs 0.7184, P = .17). Four of the five observers were more confident in making the diagnosis with contrast enhancement. With MR imaging, the diagnosis was correctly suggested in three patients in whom clinical and ultrasound data were inconclusive. Gadolinium-enhanced MR imaging gives additional information in scrotal disorders and facilitates diagnosis. It may be helpful when findings at physical examination and ultrasound differ and when plain T1- and T2-weighted images are equivocal.

[The diagnosis and orthodontic relevance of anterior disk displacement without reduction. Clinical, axiographic and magnetic resonance tomographic studies]

Magnet resonance imaging was used to diagnose 24 temporomandibular joints of 18 patients as having anterior disk displacement without reduction. By comparing clinical functional analysis, axiography, and magnet resonance imaging it was demonstrated that a valid diagnosis could be made on the basis of magnet resonance imaging alone. Former joint clicking and limitation and a dental Angle Class II were diagnostic indications of a disk displacement without reduction. Because of often only slight clinical symptoms or their absence, there is always a danger that disk displacement without reduction will go undiagnosed. In relation to orthodontic therapy, such patients are at risk, because pain can arise during treatment.

Effectiveness and safety of ultrasonic atherosclerotic plaque ablation: in vitro investigation

Ultrasound energy was applied to 137 segments of human cadaver atherosclerotic arteries, 90 with calcified and 47 with noncalcified atheromatous plaque, and to 100 segments of healthy swine aorta. The average depth of penetration was dependent on the forward force of the ultrasonic probe, the duration of treatment, and the degree of atherosclerosis. There was one perforation of a fibrous plaque using a forward force of 2 Newton and 45 sec of application time. Injury of healthy intima was minimal. It is concluded that catheter-delivered ultrasound is effective and safe for the disintegration of atherosclerotic plaques. Presently, the main limitations of the system are the lack of flexibility and steerability.

[Occlusal splint therapy in reciprocal TMJ clicking. A critical observation within a follow-up study]

During post-treatment examination the effect of splint therapy on 14 temporomandibular joints (TMJ) with anterior disk displacement were examined using clinical and instrumental findings and magnet resonance imaging (MRI) to judge the therapeutical success of the treatment from an orthodontic perspective. A stable reposition of the TMJ disk was achieved in four joints, which showed no relapse over a two-year period of observation. The success of the therapy was dependent on the extent of the tissue damage to the TMJ and also on patient compliance. The MRI yielded therapeutically valuable information, which is not revealed in the clinical-instrumental analysis, on the tissue structure of the disk and the ligaments. In certain cases the use of MRI is necessary to confirm the clinical diagnosis.

Computed tomography and histologic results in the early stages of endotoxin-injured pig lungs as a model for adult respiratory distress syndrome

RATIONALE AND OBJECTIVES

To determine early radiographic changes in diffuse alveolar injury, the authors correlated computed tomography (CT) and histopathology in pigs with recurrent endotoxinemia.

METHODS

Five pigs received recurrent endotoxin over a 17-hour period. Three pigs received physiologic saline and served as controls. Hemodynamic and blood-gas data were analyzed. CT was performed immediately before killing the animals. The lungs were cut into 5-mm-thick slices in the same axis as the CT scans and were investigated by light and electron microscopy.

RESULTS

Hemodynamic data, blood-gas analysis, and morphologic changes closely simulated the clinical situation of septic shock in the five pigs that had received endotoxin. Results of histologic examination depicted changes similar to those associated with adult respiratory distress syndrome (ARDS). CT clearly demonstrated both interstitial, and to a minor degree, intra-alveolar lesions in the endotoxin-injected group, which correlated well with dilated lymph vessels, thickened interstitium, and areas of dystelectasis on histologic examination. Although there was a rather uniform clinical picture, CT and histologic findings showed different degrees of involvement.

CONCLUSIONS

CT clearly depicts changes in endotoxin-injured pig lungs in an early clinical state, which are similar to changes associated with ARDS on histologic examination.

Ovarian cysts in the fetus and neonate--changes in sonographic pattern in the follow-up and their management

In a multicenter trial we retrospectively evaluated the clinical and sonographic data of 49 neonatal ovarian cysts, 44 of which were detected prenatally and 5 on the first day after delivery. Of the 44 prenatally detected cysts 39 were purely cystic, 5 echogenic or had a mixed pattern. In 20 patients the cystic appearance changed during delivery from purely cystic to a mixed pattern being independent on the size of the cyst. 26 of the 44 cysts were treated surgically. Salpingotorsion was found in 8 and was independent on the size of the cyst. In 15 a salpingo-oophorectomy or oophorectomy was performed, in 11 the ovary was saved. 23 patients were followed sonographically: 15 cysts showed complete resolution within 14 months without correlation to the sonographic pattern. The volume of these cysts varied between 5 and 71 ml. Neonatal ovarian cysts disappear spontaneously frequently and rarely cause severe symptoms. The authors recommend follow-up by ultrasound as the primary modality. Surgical intervention is recommended only if the cyst is space-occupying and percutaneous puncture can not be performed or in the case of emergency.

Therapeutic use of surfactant in neonatal respiratory distress syndrome. Correlation between pulmonary X-ray changes and clinical data

As part of a multicenter surfactant rescue study, the chest X-rays of 239 preterm and term infants were analyzed. To study the influence of surfactant administration on radiographic appearance, 130 patients with a clinical and radiological diagnosis of typical respiratory distress syndrome were selected, in whom adequate chest x-rays before and within 48 h after treatment were available. Median gestational age was 30 weeks (range 25-38 weeks), median birth weight was 1335 g (range 625-3450). The time of surfactant application ranged between 90 min and 24 h after birth (median 6 h). The most common finding after surfactant administration was uniform (n = 47) or disproportionate (n = 46) improvement of pulmonary aeration, which showed a significant correlation to posttreatment reduction of oxygen requirement (p less than 0.0001). Asymmetric clearance was more often localized on the right side and usually disappeared within two to five days. Only in 13 patients no change of ventilation was found. Development of interstitial emphysema (n = 24, including three patients with pneumothorax) after surfactant treatment was an unfavourable prognostic sign. 54% of these patients (13 of 24) died within the first month of life, compared to 8% (7 of 93) in the group of patients with initial improvement of ventilation.

US-assisted aspiration thrombectomy: in vitro investigations

The authors describe the use of a new ultrasound (US)-aspiration thrombectomy technique. An oscillating US probe was inserted into a thin-walled, large-bore aspiration catheter. Experiments tested the ability of the new device and other catheter combinations to remove clot material from a Petri dish, as well as from small and large vessel models made of silicone and glass tubes, respectively. Results of the experiments demonstrated that an oscillating 1.0-mm US probe inserted into an aspiration catheter (7-9 F in diameter) promoted clot fragmentation and allowed continuous aspiration of thrombi of any size. When compared with simple large-bore catheter aspiration and with mechanical fragmentation by means of a US probe within a catheter that was flushed to cool the probe, US-assisted aspiration thrombectomy demonstrated significantly better results for percutaneous transcatheter removal of fresh thrombi.

Comparative examination of various rectal tubes and contrast media for the reduction of intussusceptions

The hydrodynamic influence of different rectal tube sizes, contrast media, and heights of the fluid column on hydrostatic reduction of intussusception was analyzed in vitro. Enemas were performed in dead rabbits to compare the filling speed of bowel with a liquid and a gaseous contrast medium. For hydrostatic reduction, tubing and rectal tube with a large caliber and a low viscosity contrast medium achieved a higher filling speed of colon and are expected to provide a higher force of reduction on the intussusceptum. A rectal tube with a large caliber can be more useful than an increase of the column height. Filling bowel with carbon dioxide was approximately 7 times faster than with meglumine sodium diatrizoate. Theoretical considerations allow the hypothesis that a gaseous medium provides a faster and steadier reduction than a liquid.

[Medullary carcinoma of the thyroid and 99mTc(V)-DMSA scintigraphy. Clinical results with a new radiopharmaceutical]

99mTc(V)-DMSA scintigraphy is a non-invasive diagnostic tool for diagnostic differentiation and localisation of medullary carcinoma of the thyroid. For primary tumours its sensitivity is 77%. This diagnostic means is not only helpful for the diagnosis of primary tumours, but is especially informative for recidives and metastases of the medullary carcinoma of the thyroid. Its sensitivity for recidives and metastases is 66%. The sensitivity obtained in our study, which included four patients, corresponded to that reported in the literature.

Ultrasonography of the hip in preterm neonates

Over the period of one year, the hips of 92 preterm neonates were examined by ultrasound. Using the Graf classification only 7% showed an angle alpha between 50 and 60 degrees, which is characteristic of type IIa hips. In all other cases the angle alpha was above 60 degrees (type I). Sonographically there were no pathological cases (type IIg or worse). A reason for the relatively low number of type IIa hips could be that the short osseous acetabular rim and the broad cartilagenous Y-joint in this age group result in a "false" increase of the angle alpha.

[Normal values of thyroid gland volume. Ultrasound measurements in schoolchildren 7 to 20 years of age]

Thyroid gland volume was calculated from ultrasound data (using the ellipsoid formula) in 1080 apparently healthy schoolchildren, aged 7-20 years, from Speyer and Neckargemünd in the Federal Republic of Germany. Thyroid volume was found to increase with age: mean of 4.34 ml (single standard deviation [SD] 1.55) in seven-year olds, 13.6 ml (SD 6.2) in 16-year olds. No measurable increase was found from the 16th year onwards. No sex-related differences in size were found before the age of ten years, with a slight size increase in girls at the time of puberty. The right lobe was significantly larger than the left one (mean difference of 0.8 ml) in all age groups. There was a weakly positive correlation between thyroid volume and age, body weight, height and surface area, respectively, the best correlation for both sexes being between thyroid volume and body surface area. Among the 1080 children and juveniles of both ages there were eight with abnormal findings, all of them girls aged 16-18 years old.

[Invagination. The present status of diagnostic imaging and therapy]

The use of ultrasound techniques has brought about considerable changes in the diagnosis and therapy of intussusception in the past few years. (1) Whenever intussusception is suspected ultrasound examination of the abdomen is the diagnostic procedure of choice; a diagnosis of intussusception can be made or excluded with an adequate degree of accuracy. (2) Ultrasound monitoring is also good for the follow-up of cecal edema after reduction of intussusception, making it possible to check that there are no pathological lead points and that complete restoration of function has been achieved. (3) There are only three absolute contraindications for attempting an enema: peritonitis, shock, and perforation. (4) Whenever there are relative contraindications for administration of an enema, e.g., long duration of symptoms, complete small-bowel obstruction, it is of the utmost importance to inform the pediatrician and the surgeon and to discuss with them the potential benefits and risks involved in an attempt at hydrostatic reduction.

[Ureterocele in childhood. Clinical and radiologic picture]

This is a retrospective analysis of the clinical and radiological data recorded in 45 children with ectopic and 5 children with orthotopic ureteroceles diagnosed from 1965 to 1982. As shown in this article, it is mandatory to perform an ultrasonic examination of kidney and bladder whenever there are signs of urinary tract infection or any abnormalities of voiding. Ureterocele is diagnosed by i.v. urogram in more than 90% of cases; before treatment it is obligatory to perform a voiding cystourethrogram in addition.