Visualization and quantification of coronary calcifications with electron beam and spiral computed tomography

This contribution reviews the pathology and morphology of coronary calcifications. It summarizes the indications for investigation of the coronary arteries. The standard protocols for scan acquisition using electron beam and conventional computed tomography are described as well as various methods for evaluation such as the traditional Agatston scoring method and the newer three-dimensional scoring algorithms. Guidelines for interpreting scores are also reviewed. Major limitations of the reproducibility of the calcium score measurement are summarized. Future aspects of multirow-detector spiral computed tomography with retrospective electrocardiographic triggering for quantifying coronary calcium are discussed. Received: 13 August 1999; Accepted: 30 September 1999     

Tumors of the cardiac valves: imaging findings in magnetic resonance imaging, electron beam computed tomography, and echocardiography

We describe the findings from various cross-sectional imaging modalities in patients with cardiac valve adherent masses. The techniques are discussed, and imaging findings are compared with the results of cardiac surgery. All three patients had neurological symptoms and/or cardiac murmurs. Transthoracic and/or transesophageal echocardiography revealed the cardiac mass in all three. For differentiation of thrombus and cardiac neoplasm magnetic resonance imaging (MRI) was also performed in all three patients and electron-beam computed tomography (EBCT) in two. Fast segmented cine gradient-echo MRI techniques provided mass depiction in all patients, while T1-weighted spin-echo imaging failed in mass detection in one patient. None of the patients showed evidence of valve regurgitation or stenosis in flow sensitive cine MRI. EBCT excluded mass calcifications in both patients and reliably demonstrated the valve attached lesions. Although echocardiography is the modality of choice in evaluating cardiac masses and especially valve attached masses, MRI and EBCT provide additional information about tissue characteristics and allows an excellent overview of the cardiac and paracardiac morphology. Fast segmented cine gradient-echo MRI is especially able to depict even small tumors attached to rapidly moving cardiac valves, and valve competence can be easily assessed within the same examination. Received: 17 December 1998; Revision received: 1 June 1999; Accepted: 10 August 1999     

Dose reduction in computed tomography by attenuation-based on-line modulation of tube current: evaluation of six anatomical regions

This study investigated the potential of attenuation-based on-line modulation of tube current to reduce the dose of computed tomography (in milliamperes) without loss in image quality. The dose can be reduced for non-circular patient cross-sections by reducing the tube current at the angular positions at which the diameter through the patient diameter is smallest. We investigated a new technical approach with attenuation-based on-line modulation of tube current. Computed tomographic projection data were analyzed to determine the optimal milliampere values for each projection angle in real time, instead of performing prior measurements with localizer radiographs. We compared image quality, noise pattern, and dose for standard scans and for scans with attenuation-based on-line modulation of tube current in a group of 30 radiation therapy patients. Six different anatomical regions were examined: head, shoulder, thorax, abdomen, pelvis, and extremities (knee). Image quality was evaluated by four radiologists in a blinded fashion. We found the dose to be reduced typically by 15–50 %. In general, no deterioration in image quality was observed. Thus the dose in computed tomography be reduced substantially by technical measures without sacrificing image quality. Attenuation-based on-line modulation of tube current is an efficient and practical means for this. Received: 15 July 1999; Revised: 22 October 1999; Accepted: 26 October 1999     

Multi-detector computed tomography (MDCT) imaging of cardiovascular effects of pulmonary embolism: What the radiologists need to know

Background

Patients with pulmonary embolism have high mortality and morbidity rate due to right heart failure and circulatory collapse leading to sudden death. Multi-detector computed tomography MDCT can efficiently evaluate the cardiovascular factors related to pulmonary embolism.

Great saphenous vein thrombosis causing acute pulmonary embolism suggested by combined CT venography and pulmonary angiography

Pulmonary embolism is a life-threatening condition, which is most commonly related to deep vein thrombosis. Varicose vein thrombosis, a very common disease, is seldom reported as being related to pulmonary embolism. We present combined computed tomography venography and pulmonary angiography findings suggesting that thrombosed varicosities of a great saphenous vein caused acute pulmonary embolism in a 30-year-old male.     

Detection of central pulmonary embolism on computed tomography densitometry images before computed tomography pulmonary angiography

OBJECTIVE: The purpose of this article is to describe the imaging findings of acute central pulmonary embolism on computed tomography (CT) densitometry images performed before contrast-enhanced CT pulmonary angiography. METHODS: A retrospective review was conducted of reports from all CT pulmonary angiograms performed at our institution, and cases of acute central pulmonary embolism, defined as those with clot in the main, left, or right pulmonary arteries, were identified. Images of positive studies were reviewed on a picture archiving and communications system (PACS) workstation. RESULTS: A total of 1282 CT pulmonary angiograms were obtained for evaluation of possible acute pulmonary embolism, and 1 combined CT aortogram and pulmonary angiogram was performed for aortic dissection and acute pulmonary embolism. Two hundred fourteen (16.7%) examinations positive for acute pulmonary embolism were identified, 26 (12.1%, 2.0% of total examinations) of which had central clots. Of the 26 patients with central acute pulmonary embolism, 12 (46.1%, 5.6% of all positive studies and 0.9% of all CT pulmonary angiograms) had clots that were visible on the densitometry images. CONCLUSION: Although an uncommon finding, acute central pulmonary embolism can be detected on CT densitometry performed to optimize opacification of the pulmonary arteries for CT pulmonary angiography and may prove useful in selected clinical situations.     

Vetting requests for body computed tomography

The aim of this study was to assess the process and outcome of hospitalised patients (inpatients) for whom whole-body CT was requested but not performed. For 6 months the reasons why CT was not performed were recorded, together with relevant discussions with clinicians. Subsequent referrals for alternative investigations were noted. The eventual outcome of the patients was monitored via the patients' records. Eighty-three (8 %) of 1001 inpatient requests were identified for which body CT was not performed after an electronically generated request. Fifty-five requests were not accepted by the radiology department during the vetting process for a variety of reasons (often more than one): criteria used for rejection often overlapped and included referrals outside national guidelines (n = 20), better alternative investigations (n = 29), time constraints (n = 19), over-zealous requests (n = 17) and clinicians' erroneous interpretation of preceding imaging investigations (n = 9). Sixteen CT exams were cancelled by a clinician. An additional 12 exams were not performed for miscellaneous non-medical reasons. In no case could a patient's death be ascribed to CT not being performed. Most (981 of 1001, 98 %) CT requests comply with current guidelines, disproving a perception that many radiological referrals are inappropriate. In our health care system radiologists have to turn down some appropriate CT referrals due to a lack of CT capacity. Although lack of CT contributed to delay in diagnosis, no patient died as a direct result of not having CT. Received: 15 June 1999; Revised: 4 October 1999; Accepted: 5 October 1999     

Feasibility of synchrotron radiation computed tomography on rats bearing glioma after iodine or gadolinium injection

The purpose of this work was to demonstrate the feasibility of a new imaging technique called synchrotron radiation computed tomography (SRCT). This technique leads to a direct assessment of the in vivo concentration of an iodine- or gadolinium-labeled compound. Rats bearing C6 glioma were imaged by MRI prior to the SRCT experiment. The SRCT experiments were performed after a 1.3 g I/kg (n = 5) or a 0.4 g Gd/kg (n = 5) injection. Finally, brains were sampled for histology. The SRCT images exhibited contrast enhancement at the tumor location. Ten minutes after injection, iodine and gadolinium tissular concentrations were equal to 0.80 ( ± 0.40) mg/cm³ and 0.50 ( ± 0.10) mg/cm³, respectively in the peripheral area of the tumor (respective background value: 0.20 ± 0.02 to 0.10 ± 0.01). Correlation to MRI and histology revealed that the contrast uptake occurred in the most vascularized area of the tumor. The present study summarizes the feasibility of in vivo SRCT to obtain quantitative information about iodine and gadolinium-labeled compounds. Beyond brain tumor pathology, the SRCT appears as a complementary approach to MRI and CT, for studying iodine- and gadolinium-labeled compounds by the direct achievement of the tissular concentration value in the tissue. Received: 8 September 1999; Revised: 3 May 2000; Accepted: 4 May 2000     

Computed chest tomography in an animal model for decompression sickness: radiologic, physiologic, and pathologic findings

This study was conducted to investigate the early pulmonary effects of acute decompression in an animal model for human decompression sickness by CT and light microscopy. Ten test pigs were exposed to severe decompression stress in a chamber dive. Three pigs were kept at ambient pressure to serve as controls. Decompression stress was monitored by measurement of pulmonary artery pressure and arterial and venous Doppler recording of bubbles of inert gas. Chest CT was performed pre- and postdive and in addition the inflated lungs were examined after resection. Each lung was investigated by light microscopy. Hemodynamic data and bubble recordings reflected severe decompression stress in the ten test pigs. Computed tomography revealed large quantities of ectopic gas, predominantly intravascular, in three of ten pigs. These findings corresponded to maximum bubble counts in the Doppler study. The remaining test pigs showed lower bubble grades and no ectopic gas by CT. Sporadic interstitial edema was demonstrated in all animals – both test and control pigs – by CT of resected lungs and on histologic examination. A severe compression–decompression schedule can liberate large volumes of inert gas which are detectable by CT. Despite this severe decompression stress, which led to venous microembolism, CT and light microscopy did not demonstrate changes in lung structure related to the experimental dive. Increased extravascular lung water found in all animals may be due to infusion therapy. Received: 7 December 1998; Revision received: 2 June 1999; Accepted: 9 June 1999     

Imaging of compressive vertebral haemangiomas

Compressive vertebral haemangiomas (VHs) are rare. Correct preoperative diagnosis is useful both for operative planning (since compressive VHs are extremely vascular lesions) and to allow preoperative embolisation. Numerous radiological signs for VHs have been described, but compressive VHs frequently have atypical features. In particular, magnetic resonance features are not well established. We present imaging features in three cases of compressive VH and review the imaging findings in an additional 106 previously published cases. Findings were typical in 52 of 80 plain film (65 %), 33 of 41 computed tomography (80 %) and 13 of 25 magnetic resonance examinations (52 %). The prevalence of previously described imaging features is reported. Awareness of the range of magnetic resonance features is important since this is frequently the initial investigation in patients presenting with symptoms of neural compression. Since computed tomography is typical in 80 % of cases, this is a useful confirmatory test if magnetic resonance features are suspicious but not diagnostic of compressive VH. Received: 6 August 1999; Revised: 4 November 1999; Accepted: 4 November 1999     

Transverse colon volvulus: appearance on computed tomography

Transverse colon volvulus is a rare but potentially fatal cause of intestinal obstruction. We report the case of a 72-year-old woman presenting with clinically suspected intestinal obstruction. She underwent abdominal and pelvic computed tomography (CT). The diagnosis was obtained preoperatively: CT showed “the whirl sign”, indicative of a volvulus.     

Ruptured adrenal artery aneurysm: a case report

A case of ruptured adrenal artery aneurysm is presented. The ultrasound, computed tomography and selective renal angiography findings are described in detail. Aneurysms of adrenal arteries are particularly rare. Early diagnosis is important because of their tendency towards rupture and subsequent high mortality rate. Received: 12 November 1998; Revised: 10 March 1999; Accepted: 13 April 1999     

The role of spiral CT using the pulmonary embolus protocol: a comparison of emergency department and hospitalized populations

Purpose: To compare the incidence of CT scan-detected pulmonary embolism, the CT scan-detected alternative findings (ancillary findings and alternative radiologic diagnoses), and the patient characteristics in emergency department and in hospitalized patients. Materials and methods: 81 spiral CT scans in 79 consecutive adult emergency department patients were retrospectively identified by computer search. During the same 9-month interval, 131 consecutive adult in-patients were similarly identified. The in-house and emergency department populations were compared in respect of incidence of pulmonary embolism and alternative findings using χ ² analysis. Results: 81 emergency department scans and 135 in-patient scans were evaluated. Of these, 22 emergency department scans (27.1 %) and 37 in-patient scans (27.4 %) were positive for pulmonary embolism. Of the scans that were negative for a pulmonary embolism, 45 emergency department scans (76.2 %) and 88 in-patient scans (89.8 %) were positive for alternative findings. These included atelectasis, adenopathy, metastatic disease, and pneumomediastinum. Alternative radiologic diagnoses on scans negative for pulmonary embolism occurred in 8/59 emergency department patients (13.5 %) and in 17/98 in-patients (17.3 %). These included pneumonia, tumor, mucus plugging, pericardial effusions, and thoracic aortic dissection. Conclusions: No significant difference exists between the emergency department and in-patient populations for the incidence of pulmonary embolism on spiral CT scans. Although a significant difference did exist between these populations in respect to alternative findings, the high percentage of alternative findings in both populations shows a possible advantage of CT over the traditional test, the ventilation-perfusion scan. Therefore, spiral CT should not be limited to the in-patient population as the first-line imaging modality for the diagnostic evaluation of pulmonary embolism.     

Comparison of computed tomography and cineangiography in the demonstration of central pulmonary arteries in cyanotic congenital heart disease

Purpose: To assess the diagnostic accuracy of contrast-enhanced computed tomography (CT) for central pulmonary artery pathology in patients with cyanotic congenital heart disease (CCHD) and right ventricular outflow obstruction. Methods: We compared contrast-enhanced CT and cine pulmonary arteriography in 24 patients with CCHD to assess central pulmonary arteries including the confluence. Both investigations were interpreted by a cardiac radiologist in a double-blinded manner at an interval of 3 weeks. Angiography was used as the gold standard for comparison. Results: The sensitivity for visualization of main pulmonary artery (MPA), right pulmonary artery (RPA), left pulmonary artery (LPA), and confluence on CT was 94%, 100%, 92.8%, and 92.8%, respectively. Diagnostic specificity for the same entities was 28.5%, 100%, 80%, and 50%, respectively. The positive predictive value for each was 76.2%, 100%, 94.1%, and 72.2%, respectively. The low specificity of CT in the evaluation of the MPA and the confluence is perhaps due to distorted right ventricular outflow anatomy in CCHD. Large aortopulmonary collaterals in this region were mistaken for the MPA in some patients with pulmonary atresia. Conclusion: CT is a useful, relatively noninvasive, imaging technique for the central pulmonary arteries in selected patients. It can supplement diagnostic information from angiography but cannot replace it. LPA demonstration on axial images alone is inadequate.     

多层螺旋CT在肺动脉栓塞诊断中的应用(附27例报告)

目的:探讨多层螺旋CT肺动脉成像(CTPA)对肺动脉栓塞的诊断价值.方法:对27例经MSCT确诊肺动脉栓塞患者进行回顾性分析.结果:多发肺动脉栓塞18例,其中双侧多发15例,左侧多发1例,右侧多发2例;单发9例,其中肺动脉干4例,叶动脉1例,段动脉4例.肺动脉栓塞的直接征象包括肺动脉主干或其分支的充盈缺损及肺动脉段面细小及管腔内不均匀密度减低;间接征象可以有肺内"马赛克征"、楔形影或索条状影,胸腔积液或胸膜肥厚.结论:CTPA对肺动脉栓塞的检查是一种价格便宜,无创伤的检查,诊断结果可靠,可作为急诊和普通临床工作中怀疑本病时首选的影像学检查方法.     

Helical computed tomography diagnosis of gastrointestinal perforation in the elderly patient

Purpose: To determine the value of helical CT in a consecutive series of elderly patients referred with clinically suspected gastrointestinal perforation. Methods: Our series comprised 34 consecutive elderly patients (mean age: 68 years) presenting with acute abdominal symptoms potentially suggestive of gastrointestinal perforation. All the patients were prospectively subjected to abdominal computed tomography (CT). On helical CT, the presence of free air was considered diagnostic of gastrointestinal perforation. Other findings such as intraperitoneal free fluid, thickening of bowel wall, streaky density within the mesentery, “dirty fat” sign, and focal collection of extraluminal fecal matter (“dirty mass”) were considered indirect findings of perforation. Results: At surgery, the following sites of perforation were found: duodenum (38.2 %), stomach (29.4 %), ileum (8.8 %), sigmoid colon (8.8 %), rectum (5.8 %), and jejunum, appendix, and transverse colon (2.9 % of cases each). CT demonstrated the presence of free air in 94.1 % of cases; intraperitoneal free fluid was present in 76.4 % of patients and thickening of bowel wall in 50 %. Streaky density within the mesentery was found in one patient. Conclusion: CT is a reliable diagnostic method by which to assess gastrointestinal perforation, because it provides excellent contrast resolution to depict the presence of even small amounts of free air in the abdomen. This is particularly helpful where elderly patients are concerned.     

实验性急性肺栓塞的比较影像学研究

目的　探讨核素肺灌注显像、增强螺旋CT及数字减影肺动脉造影对猪急性肺栓塞实验模型 (相当于人类亚肺段水平肺栓塞 )的影像学特点。方法　 13头中国实验用小型猪 ,经颈静脉注射明胶海绵栓子 (直径 3 8～ 4 2mm) ,制作肺栓塞模型后进行核素肺灌注显像、增强螺旋CT和数字减影肺动脉造影 ,以病理检查为标准 ,比较 3种检查方法的灵敏度和特异性。结果　对 195个肺段(动脉段 )进行分析 ,病理诊断阳性肺段 4 6个 ,阴性肺段 14 9个。核素肺灌注显像阳性肺段 5 1个 (包括假阳性肺段 11个 ) ,灵敏度为 87% ,特异性为 93% ;增强螺旋CT阳性肺段 4 4个 (包括假阳性肺段15个 ) ,灵敏度为 6 3% ,特异性为 90 % ;数字减影肺动脉造影阳性肺段 4 7个 (包括假阳性肺段 2个 ) ,灵敏度为 98% ,特异性为 99%。核素肺灌注显像病变检出率比增强螺旋CT高 (P <0 0 5 ) ,但与数字减影肺动脉造影相比差异无显著性 (P >0 0 5 )。增强螺旋CT可对栓子进行准确定位。结论　核素肺灌注显像对猪肺段 (相当于人类亚肺段 )肺栓塞的探测优于增强螺旋CT ,而后者对栓子定位优于前者 ;数字减影肺动脉造影对猪肺段肺栓塞诊断能力最强 ,但有创 ,应用受限。     

Magnetic resonance imaging of athlete's heart: myocardial mass, left ventricular function, and cross-sectional area of the coronary arteries

To evaluate left ventricular myocardial mass and function as well as ostial coronary artery cross-sectional area in endurance athletes, an athlete group of 12 highly trained rowers and a control group of 12 sedentary healthy subjects underwent MR examination. An ECG-gated breath-hold cine gradient-echo sequence was used to calculate myocardial mass, end-diastolic and end-systolic volumes, stroke volume, and cardiac output, all related to body surface area, as well as ejection fraction. A 3D fat-saturated ECG- and respiratory-triggered navigator echo sequence was used to evaluate coronary arteries: left main (LM), left anterior descending (LAD), left circumflex (LCx), and right coronary artery (RCA). Cross-sectional area was calculated and divided for body surface area. Myocardial mass was found significantly larger in athlete group than in control group (p = 0.0078), the same being for end-diastolic volume (p = 0.0078), stroke volume (p = 0.0055), LM (p = 0.0066) and LAD (p = 0.0129). No significant difference was found for all the remaining parameters. Significant correlation with myocardial mass was found for LM (p < 0.001) and LAD (p = 0.0340), not for LCx and RCA. Magnetic resonance imaging is a useful tool in evaluating the myocardial hypertrophy and function of athlete's heart. Magnetic resonance angiography is a valuable noninvasive method to visualize the correlated cross-sectional area increase of the left coronary artery system. Received: 25 March 1999; Revised: 31 August 1999; Accepted: 1 September 1999     

Sudden death due to rupture of major aortopulmonary collateral arteries in a patient with tetralogy of Fallot and pulmonary atresia

We report a case of fatal mediastinal hemorrhage in a 20-year-old man caused by rupture of the major aortopulmonary collateral arteries (MAPCAs). The patient had an unoperated tetralogy of Fallot with pulmonary atresia. Plain chest radiograph and computed tomography showed a large hematoma in the upper mediastinum. Previous cardiac angiography, performed 6 years previously, demonstrated markedly tortuous vascular structures arising from the inferior aspect of the aortic arch. In this case, the mediastinal hemorrhage was thought to be due to rupture of the MAPCAs. If a patient presents with sudden cardiac arrest and mediastinal dilatation, and unoperated congenital heart disease is suggested by a plain chest film, the radiologist should consider the possibility, although rare, of mediastinal hemorrhage resulting from rupture of the MAPCAs.     

Percutaneous nephrostomy: placement under laser guidance and real-time CT fluoroscopy

The purpose of this paper is to present our experience with real-time computed tomography (CT) fluoroscopy guided percutaneous nephrostomy (PNT) and to describe this technique involving puncture under laser guidance. We attempted 30 placements in 25 patients: puncture was directed by laser guidance and placement of the tube was made under real time CT fluoroscopy. 25 procedures were performed in prone position and 5 procedures in the supine position. The time necessary for the procedure ranged from 10 to 45 min (mean 25 min). The average duration of CT fluoroscopy per placement was 49 seconds (range 7–110 s). The PNT placement was successful as a sole procedure including puncture and catheter placement in 24 of 30 cases; in the remainder of cases, puncture was performed under CT guidance but the catheter was definitively positioned in conventional fluoroscopy. The CT fluoroscopy technique allows routine, efficient and safe PNT placement, especially when encountering difficult access to the pelvicaliceal system. Received: 9 June 1999; Revised: 12 November 1999; Accepted: 12 November 1999