Acoustic shadowing due to refractive and reflective effects.

Acoustic shadowing may be seen distal to the margins of rounded structures having different acoustic velocities from the surrounding tissue. Refractive and reflective mechanisms for such shadowing are reviewed and in vitro demonstrations of such shadowing are presented. Clinical examples of refractive and reflective shadows are given, and their importance is discussed.     

False diagnosis of acoustic neuroma due to subdural injection during gas CT cisternogram

Gas CT cisternography is a reliable examination for the detection of small acoustic neuromas. False-positive or equivocal findings do result, however, from a small number of these examinations. In this case report inadvertent subdural injection of gas caused diagnostic difficulties.     

飞行员听神经病停飞一例

患者男性，36岁，歼-7飞行员，飞行时间1530h。因听力逐渐下降两年于2002年7月14日入院。患者自觉近两年来：双耳听力下降，逐渐加重，左耳较重，并有两次短暂性视物旋转性眩晕。入院查体：双外耳、鼓膜正常，音叉检查(512Hz)示双耳感音性聋，左耳较重，无自发性眼震。纯音听阈检查：双耳上升型感=旨性聋曲线，左耳平均气导听阈为47．5dB，右耳25dB。双耳声导抗图为     

Pathologic gas collections on abdominal computed tomography: Differential diagnosis and physiologic correlation

Abdominal computed tomography is often the critical step in the evaluation of patients presenting in the emergency department with abdominal pain and/or suspected intra-abdominal infection. Gas is normally found in the stomach, small bowel, colon, rectum, and occasionally the appendix. However, extraluminal gas collections can be identified on abdominal radiographs or computed tomographic examinations, and their presence often suggests specific pathology. Knowledge of different intra-abdominal pathologic gas collections and the underlying physiology contributing to each is important in understanding the clinical significance of each entity. The spectrum of intra-abdominal gas collections, as well as their clinical significance, will be described.     

Multiple percutaneous access routes to multiple calculi, calculi in caliceal diverticula, and staghorn calculi

For expeditious removal of multiple calculi from certain locations in the pyelocaliceal system, the use of multiple percutaneous entry routes is advocated. The accessibility of different regions of the pyelocaliceal system from different percutaneous entry sites was mapped out after experience with the percutaneous removal of 87 solitary and 37 multiple renal calculi. A technique allowing limited access to calculi in caliceal diverticula and hydrocalices distal to stenotic infundibula was used, along with a technique for percutaneous infundibuloplasty, which is necessary to ensure drainage of such obstructed calices or caliceal diverticula after percutaneous lithotripsy. In 34 of 37 patients with multiple or staghorn calculi, all calculi were eventually removed by these methods. The use of multiple entry routes did not increase the risk of reduced renal function. Moreover, improved drainage through the resultant multiple nephrostomy tubes and transinfundibular stents has reduced the incidence of postoperative septicemia.     

Differentiation at autopsy between in vivo gas embolism and putrefaction using gas composition analysis

Gas embolism can arise from different causes (iatrogenic accidents, criminal interventions, or diving related accidents). Gas analyses have been shown to be a valid technique to differentiate between putrefaction gases and gas embolism. In this study, we performed systematic necropsies at different postmortem times in three experimental New Zealand White Rabbits models: control or putrefaction, infused air embolism, and compression/decompression. The purpose of this study was to look for qualitative and quantitative differences among groups and to observe how putrefaction gases mask in vivo gas embolism. We found that the infused air embolism and compression/decompression models had a similar gas composition prior to 27-h postmortem, being typically composed of around 70–80 % of N₂ and 20–30 % of CO₂, although unexpected higher CO₂ concentrations were found in some decompressed animals, putting in question the role of CO₂ in decompression. All these samples were statistically and significantly different from more decomposed samples. Gas composition of samples from more decomposed animals and from the putrefaction model presented hydrogen, which was therefore considered as a putrefaction marker.     

Differentiation of hemopericardium due to ruptured myocardial infarction or aortic dissection on unenhanced postmortem computed tomography

The aim of the study was to evaluate unenhanced postmortem computed tomography (PMCT) in cases of non-traumatic hemopericardium by establishing the sensitivity, specificity and accuracy of diagnostic criteria for the differentiation between aortic dissection and myocardial wall rupture due to infarction. Twenty six cases were identified as suitable for evaluation, of which ruptured aortic dissection could be identified as the underlying cause of hemopericardium in 50% of the cases, and myocardial wall rupture also in 50% of the cases. All cases underwent a PMCT and 24 of the cases also underwent one or more additional examinations: a subsequent autopsy, or a postmortem magnetic resonance (PMMR), or a PMCT angiography (PMCTA), or combinations of the above. Two radiologists evaluated the PMCT images and classified each case as “aortic dissection”, “myocardial wall rupture” or “undetermined”. Quantification of the pericardial blood was carried out using segmentation techniques. 17 of 26 cases were correctly identified, either as aortic dissections or myocardial ruptures, by both readers. 7 of 13 myocardial wall ruptures were identified by both readers, whereas both readers identified correctly 10 of 13 aortic dissection cases. Taking into account the responses of both readers, specificity was 100% for both causes of hemopericardium and sensitivity as well as accuracy was higher for aortic dissections than myocardial wall ruptures (72.7% and 87.5% vs 53.8% and 75% respectively). Pericardial blood volumes were constantly higher in the aortic dissection group, but a statistical significance of these differences could not be proven, since the small count of cases did not allow for statistical tests. This study showed that diagnostic criteria for the differentiation between ruptured aortic dissection and myocardial wall rupture due to infarction are highly specific and accurate.     

Differentiation of benign from malignant thyroid nodules with acoustic radiation force impulse technique

Objective:

The aim of our study was to assess the performance of acoustic radiation force impulse (ARFI) imaging to differentiate benign from malignant thyroid nodules.

Methods:

182 patients who needed thyroid surgery were examined. All patients and 50 healthy volunteers underwent ARFI sonoelastography, which quantitatively analysed the elasticity and hardness of the nodule''s centre and periphery.

Results:

ARFI values showed a statistical significance between malignant nodules and benign nodules and common thyroid parenchyma, in both the centre and periphery of nodules (p < 0.01). There was no significant difference between benign nodules and common thyroid parenchyma in either the nodule''s centre or periphery (p > 0.05). There was no significant difference between the nodule''s centre and periphery of the elastic parameters in both the benign and malignant nodules. There was a statistically significant difference among the two areas (the central group and the peripheral group) under the receiver operating characteristic curve, and the optimal model was the peripheral group. For differentiation of malignant from benign nodules, the sensitivity and specificity were 96.3% and 96.2%, respectively, when 2.545 m s⁻¹ was chosen as a cut-off value in the peripheral group.

Conclusion:

ARFI imaging may be helpful to differentiate benign nodules from malignant thyroid nodules. The selecting measurement position is important in ARFI imaging, and it has good diagnostic value in clinical applications.

Advances in knowledge:

This study shows the diagnostic contribution of ARFI imaging in thyroid lesions.Thyroid cancer is the most common endocrine malignancy, and its incidence has increased in recent years.¹ It comprises different clinical and histological features in respect to different treatments.² The diagnostic method for thyroid cancer has very quickly progressed in recent years, but the pre-operative misdiagnosis rate is 40–70%.A newer ultrasound elastography technique called acoustic radiation force impulse (ARFI), which is performed under direct visual guidance, has recently been verified to measure the stiffness of many tissues in vivo, for example in the liver.^3,4 In our study, we investigated the mechanical properties of focal thyroid disease with ARFI. The purposes of this study were to assess the effectiveness of ARFI quantification in the diagnosis of focal thyroid nodules and differentiation of benign from malignant thyroid lesions by quantification of their stiffness.     

Percutaneous drainage and aspiration of fluid collections: emphasis on pancreatic collections and transplant patients

Percutaneous aspiration or drainage was the initial treatment of 104 fluid collections in 92 patients. Our success rate was 91%, with a 7% recurrence, 3% complication rate, and 4% mortality rate. Percutaneous drainage (PD) was beneficial in all but two patients, and open surgical drainage was avoided in 84 patients. Included are 18 patients who had pancreatic fluid collections treated, with one drainage failure and one death in this subgroup. Of these patients, 50% had fistulae discovered after drainage, a higher rate than in the patients without pancreatic disease (33%). There are also 10 patients with transplants and subsequent fluid collections, all successfully treated by PD. We conclude that percutaneous abscess drainage techniques are as valuable in the more difficult pancreatic and transplant patients as they are in other patients.     

上消化道穿孔致肝包膜下积液积气1例

患者 女性,65岁。无明显诱因出现腹部疼痛1天,伴腹胀、恶心、呕吐（胃内容物）,既往有胃溃疡病史。体检：全腹压痛及反跳痛阳性,肠鸣音减弱,实验室检查：WBC：13．8×10^9/L。腹部立位平片：右侧中上腹部一气液腔影,     

Growth dynamics and the largest size of gas bubbles emerging in body tissues due to decompression]

Symptoms of decompression sickness (DCS) develop when the total volume of gas bubbles due to decompression reaches the magnitude critical for a body tissue. Number of the bubbles is a function of random nucleation intensity before, during or after decompression and tissue superaeration dynamics, whereas their size is unambiguously dependent on a tissue, decompression phase and bubbling time. A mathematical model of bubble tissue dynamics has been proposed for calculating the dynamics of mathematical expectation of the total gas in tissues and mounting a method for comparative analysis of the maximal DCS probability as a result of implementation of different decompression tables. Unequal intensity of nucleation during spaceflight EVA and its ground simulation w/o spacesuit is the course of inequality of decompression safety of these operations.     

Appearance of gas collections after scuba diving death: a computed tomography study in a porcine model

Introduction

Postmortem computed tomography can easily demonstrate gas collections after diving accidents. Thus, it is often used to support the diagnosis of air embolism secondary to barotrauma. However, many other phenomenons (putrefaction, resuscitation maneuvers, and postmortem tissue offgassing) can also cause postmortem gas effusions and lead to a wrong diagnosis of barotrauma.

Objectives

The aim of this study is to determine topography and time of onset of postmortem gas collections respectively due to putrefaction, resuscitation maneuvers, and tissue offgassing.

Materials and methods

A controlled experimental study was conducted on nine pigs. Three groups of three pigs were studied postmortem by CT from H0 to H24: one control group of nonresuscitated nondivers, one group of divers exposed premortem to an absolute maximal pressure of 5 b for 16 min followed by decompression procedures, and one group of nondivers resuscitated by manual ventilation and thoracic compression for 20 min. The study of intravascular gas was conducted using CT scan and correlated with the results of the autopsy.

Results

The CT scan reveals that, starting 3 h after death, a substantial amount of gas is observed in the venous and arterial systems in the group of divers. Arterial gas appears 24 h after death for the resuscitated group and is absent for the first 24 h for the control group. Concerning the putrefaction gas, this provokes intravenous and portal gas collections starting 6 h after death. Subcutaneous emphysema was observed in two of the three animals from the resuscitated group, corresponding to the thoracic compression areas.

Conclusion

In fatal scuba diving accidents, offgassing appears early (starting from the first hour after death) in the venous system then spreads to the arterial system after about 3 h. The presence of intra-arterial gas is therefore not specific to barotrauma. To affirm a death by barotrauma followed by a gas embolism, a postmortem scanner should be conducted very early. Subcutaneous emphysema should not be mistaken as diagnostic criteria of barotrauma because it can be caused by the resuscitation maneuvers.     

Adjuncts and modifications to basket retrieval of retained biliary calculi

Although current techniques for percutaneous biliary stone extraction are highly successful, many patients require manipulation of the calculi before such extraction is possible. This article describes several adjunctive techniques for biliary stone retrieval that have proven to be effective. These include the modification of angiographic catheters for catheterization of ipsilateral ducts from the transhepatic approach, extractions of calculi from smaller ducts using constant irrigation and balloon catheters, and balloon-aidėd transampullary expulsion.     

Postmortem computed tomography evaluation of fatal gas embolism due to connection of an intravenous cannula to an oxygen supply

An 84-year-old man who had suffered from chronic obstructive pulmonary disease accompanied by moderate pneumonia as well as gastric cancer with liver metastasis was found dead by a nurse, who noticed that the patient’s intravenous catheter in the left forearm had been erroneously connected to an oxygen supply in his hospital room, leading to infusion of oxygen into a vein. Postmortem CT scanning demonstrated multiple accumulations of gas in the pulmonary artery, the right atrium and ventricle, as well as the left subclavian and brachiocephalic veins, corresponding to the route that the infused gas would have taken to the heart and pulmonary artery. Conventional autopsy revealed the presence of gas in the right ventricle. These findings suggested that the immediate cause of death was a gas embolus due to oxygen that had entered the cardiopulmonary circulation via the intravenous catheter. This case highlights the usefulness of postmortem imaging as an aid to conventional autopsy for demonstrating gas embolism.