Pulmonary nodules: estimation of malignancy at thin-section helical CT--effect of computer-aided diagnosis on performance of radiologists

PURPOSE: To evaluate the effect of a computer-aided diagnosis (CAD) system on the diagnostic performance of radiologists for the estimation of the malignancy of pulmonary nodules on thin-section helical computed tomographic (CT) scans. MATERIALS AND METHODS: The institutional review board approved use of the CT database; informed specific study-related consent was waived. The institutional review board approved participation of radiologists; informed consent was obtained from all observers. Thirty-three (18 malignant, 15 benign) pulmonary nodules of less than 3.0 cm in maximal diameter were evaluated. Receiver operating characteristic (ROC) analysis with a continuous rating scale was used to compare observer performance for the estimation of the likelihood of malignancy first without and then with the CAD system. The participants were 10 board-certified radiologists and nine radiology residents. RESULTS: For all 19 participants, the mean area under the best-fit ROC curve (A(z)) values achieved without and with the CAD system were 0.843 +/- 0.097 (standard deviation) and 0.924 +/- 0.043, respectively. The difference was significant (P = .021). The mean A(z) values achieved without and with the CAD system were 0.910 +/- 0.052 and 0.944 +/- 0.040, respectively, for the 10 board-certified radiologists (P = .190) and 0.768 +/- 0.078 and 0.901 +/- 0.036, respectively, for the nine radiology residents (P = .009). CONCLUSION: Use of the CAD system significantly (P = .009) improved the diagnostic performance of radiology residents for assessment of the malignancy of pulmonary nodules; however, it did not improve that of board-certified radiologists.     

Comparison of neutral oral contrast versus positive oral contrast medium in abdominal multidetector CT

To determine whether neutral contrast agents with water-equivalent intraluminal attenuation can improve delineation of the bowel wall and increase overall image quality for a non-selected patient population, a neutral oral contrast agent (3% mannitol) was administered to 100 patients referred for abdominal multidetector row computed tomography (MDCT). Their results were compared with those of 100 patients given a positive oral contrast agent. Qualitative and quantitative measurements were done on different levels of the gastrointestinal tract by three experienced readers. Patients given the neutral oral contrast agent showed significant better qualitative results for bowel distension (P < 0.001), homogeneity of the luminal content (P < 0.001), delineation of the bowel-wall to the lumen (P < 0.001) and to the mesentery (P < 0.001) and artifacts (P < 0.001), leading to a significant better overall image quality (P < 0.001) than patients receiving positive oral contrast medium. The quantitative measurements revealed significant better distension (P < 0.001) and wall to lumen delineation (P < 0.001) for the patients receiving neutral oral contrast medium. The present results show that the neutral oral contrast agent (mannitol) produced better distension, better homogeneity and better delineation of the bowel wall leading to a higher overall image quality than the positive oral contrast medium in a non-selected patient population.     

中性口服对比剂和阳性口服对比剂在腹部多层CT(MDCT)中的应用比较

探讨在非选择性患病人群中应用等量水腔内稀释中性对比剂的方法能否改善肠管壁的显示和提高整体的成像质量。对100例行腹部多层CT(MDCT)检查的病人给     

Hypotensive shock associated with bradycardia after intravenous injection of contrast medium

A case of hypotensive shock associated with bradycardia that occurred after injection of nonionic monomeric contrast medium is described. Whether the pathogenesis of this type of reaction is solely vasovagal or is directly caused by the contrast medium is not known. The number of occurrences after administration of nonionic monomeric versus conventional contrast agents should be compared to solve this problem.     

Epilepsy in patients with brain metastases triggered by intravenous contrast medium

187 patients with histologically proven primary neoplasms underwent computed tomography (CT) of the brain following intravenous administration of contrast medium. Eight developed focal epileptic seizures 2 to 4 minutes after the start of the injection. In three of these patients, in whom there was CT evidence of bilateral mass lesions of the brain, this epileptic activity became generalised into grand mal seizures, and two died in status epilepticus. In the other five patients with unilateral deposits in the brain, the focal fits corresponded to the site of the lesion shown by CT. Three of the patients had follow-up electroencephalography (EEG) examinations which showed unilateral focal activity, and their EEG foci correlated with the CT findings.     

Bolus geometry and dynamics after intravenous contrast medium injection

Studies of contrast medium bolus geometry and dynamics were carried out to provide data for optimizing the use of contrast medium in digital subtraction angiography (DSA) and dynamic CT. Apparatus for fast digital recording of x-ray attenuation profiles was used; this is a new digital imaging mode (Chronogram) available on a CT scanner. Variables studied were injection site, injection speed, contrast medium volume, and subsequent saline injection; peak time, full width at half maximum, and maximum contrast enhancement were recorded. Positioning of the catheter in the vena cava reduced peak time and increased enhancement. High injection speeds led to shorter peak times. An increase in speed from 4 to 8 ml/s caused markedly higher enhancement, while further increase did not add significantly to enhancement. For a given injection speed, enhancement was increased and the peak time delayed by using larger injection volumes. Injection of saline solution after intravenous contrast medium did not change results significantly. There was a statistically significant correlation between pulse rate and peak time; the faster the pulse rate the shorter the peak time.     

Pulmonary nodule: evaluation with spiral volumetric CT

Spiral volumetric computed tomography (CT) was used prospectively in 20 patients with a suspected solitary pulmonary nodule less than 1 cm in diameter on plain chest radiographs. Four additional nodules were detected with spiral CT than were detected with conventional CT. This technique required a 12-second breath hold; patient cooperation was excellent.     

Subtracted 3D CT angiography for the evaluation of intracranial aneurysms in 256-slice multidetector CT: usefulness of the 80-kVp plus compact contrast medium bolus protocol

Objectives

To evaluate the usefulness of an 80-kVp and compact contrast material protocol for arterial phase subtracted cerebral 3D-CTA using 256-slice multidetector CT.

Methods

Thirty-two patients underwent CT with 100 kVp and received a contrast dose of 370 mgI/kg body weight over 15 s (protocol A). Thirty-three patients underwent CT with 100 kVp and received a contrast dose of 296 mgI/kg body weight over 10 s (protocol B). Thirty-three other patients underwent CT with 80 kVp and received a contrast medium dose of 296 mgI/kg body weight over 10 s (protocol C). We compared the arterial attenuation and contrast noise ratio (CNR) of each protocol. Two independent readers assessed overall image quality.

Results

Arterial attenuation was significantly higher under protocols A (418.6?±?71.1 HU) and C (442.7?±?79.3 HU) than under protocol B (355.8?±?107.2 HU; P?<?0.05). The CNR of protocol C (26.1?±?6.1) was higher than that of protocol A (20.7?±?8.4; P?<?0.05). The overall image quality of protocol A was higher than that of protocol C (P?<?0.01).

Conclusion

The 80-kVp plus compact contrast protocol is well suited to arterial phase subtracted cerebral 3D-CTA without confounding venous enhancement.

Key Points

? Subtracted 3D CT angiography is useful in the evaluation of intracranial aneurysms. ? A compact contrast material protocol increased arterial attenuation without venous contamination. ? Low-kVp CT compensated for the decreased amount of contrast medium. ? An 80-kVp CT with a compact enhancement bolus provides good intracranial 3D-CT angiography.     

CT study of the cervical spine with intravenous administration of the contrast medium

Computed tomography (CT) without contrast medium is largely applied to the study of intervertebral disk pathology in the lumbar spine, but has not been widely accepted in the cervical spine, due to technical and anatomical limitations. For these reasons many neuroradiologists still prefer myelography or myelo-CT. CT may yield better results if combined with iv contrast medium injection, which allows a better visualization of disk herniation. This technique is aimed at enhancing the density of the venous plexus which is located close to the intervertebral disk, the vertebral bodies and the neural foramina. A better contrast enhancement is thus obtained between the disk and the spinal cord. The authors' experience is based on 61 patients who underwent contrast enhanced CT; in 22 cases myelography and myelo-CT were also performed. The authors describe their technique and the most frequent CT findings of disk herniation: the typical finding includes a focal hypodensity surrounded by a linear blush, due to a posteriorly dislocated epidural vein. The posterior linear blush alone may be present in few cases. Contrast-enhanced CT is very useful in the study of disk pathology of the cervical spine, even when compared with myelography and myelo-CT, due the increase in the density of epidural plexus it allows. However, the technique must be very accurate if the same results as those of myelo-CT are to be obtained.     

计算机辅助诊断的三维体积测量技术在实性肺结节CT随诊中的价值

目的 评价计算机辅助诊断的三维体积测最技术在实性肺结节随诊中的价值.方法 行2次或2次以上胸部CT扫描的实性肺结节患者46例,共计58个结节.在CT工作站上用三维体积测量软件计算结节的体积、倍增时间(DTs)和体积增长率(VGBs).用非参数检验评价DTs在良恶性结节之间的差异有无统计学意义;用X2检验评价DTs阈值在良恶性结节之间的差异有无统计学意义.所有结果均经组织学、诊断性治疗或临床随诊证实.结果 (1)恶性结节13个.DTs为45～465 d(中位159 d),12个<400 d.VGRs为8%～329%(中位30.0%).(2)良性结节45个.VGRs为-38%～24%(中位0).①24个体积增大或不变的结节,DTs为302～55 158 d(中位2 704 d),22个>400 d,VGRs为0～24%(中位6.5%).②21个体积缩小的结节,无法计算DTs,VGRs为-38%～-4%(中位-16.0%).(3)DTs在良恶性结节之间的和差异有统计学意义(P<0.05).(4)以DTs≤500、400和300 d分别作为恶性结节的诊断阈值,各阈值在良恶性结节之间的差异均有统计学意义(P均<0.01),其敏感性分别为100.0%、92.3%、76.9%,特异性分别为87.5%、91.7%、100.0%,准确件分别为91.9%、94.6%、91.9%,阳性似然比分别为8、11、0.结论 (1)以DTs≤400 d作为恶性结节的诊断阈值,具有很高的诊断价值.(2)计算机辅助诊断的三维体积测量技术在实性肺结节的随诊中可早期发现病变大小的变化,对鉴别结节良恶性具有重要价值,可作为难以定性的实性肺结节随诊的常规方法 .