Liver transplantation: role of the radiologic methods in the postoperative period]

Some complications of liver transplantation appear as aspecific clinical and blood test abnormalities; others--e.g., hepatic artery thrombosis in the immediate postoperative period and stenosis of the biliary anastomosis before T-tube removal--require early diagnosis. These considerations justify the need of frequent radiologic examination in both the complicated course and the follow-up. The authors report their experience in 59 adult patients submitted to liver transplantation for irreversible liver disease in advanced stage (49 with cirrhosis, 10 with HCC; 5 with cholestatic hepatopathy; 3 with fulminant hepatitis; 1 with Budd-Chiari syndrome; 1 with metastatic APUDoma). Two hundred and sixty-three radiological examinations were performed (Doppler US, CT, angiography and cholangiography) which showed numerous early and delayed complications: 13 of them were treated with interventional radiology maneuvers (US-or CT-guided percutaneous drainage of fluid collections, biliary drainage, bilioplasty, arterial transcatheter embolization). Our results demonstrate that diagnostic and operative radiology are essential for the success of liver transplantation; integrated imaging is particularly important in the diagnosis of complications, while interventional radiology techniques can be usefully employed in their treatment.     

Helical CT in renal transplantation: normal findings and early and late complications.

Over a 5-year period, 346 helical computed tomographic (CT) studies were performed in renal transplant recipients. Helical CT proved useful in this context by depicting parenchymal, perirenal, renal sinus, pyeloureteral, and vascular complications in great detail. CT often delineates fluid collections and their anatomic relationship to adjacent structures better than ultrasonography (US), particularly in obese patients. CT-guided puncture and drainage can be performed in cases in which US is deemed inadequate. CT angiography can depict arterial diseases such as stenosis, thrombosis, arteriovenous fistulas, aneurysms, and pseudoaneurysms in the graft artery and in the recipient iliac arterial system, thereby obviating conventional angiography in some cases. Helical CT with three-dimensional image reformatting allows accurate imaging of the entire course of ureteral and periureteral diseases (eg, hydronephrosis, ureteral leak and stricture, pyeloureteral obstruction). CT can be used in the confirmation and staging of malignancies of the renal parenchyma and urothelium. It is also helpful in evaluating associated disease in the native kidneys, acute and chronic rejection, graft embolization, and end-stage disease. Although US and nuclear medicine examination are the imaging modalities of choice in renal transplantation, helical CT is a valuable alternative when these techniques are inconclusive.     

Orthotopic liver transplantation: reversible Doppler US findings in the immediate postoperative period

Orthotopic liver transplantation (OLT) is the only definitive treatment for irreversible acute liver failure and chronic liver disease. In the immediate postoperative period after OLT, patients are closely monitored with Doppler ultrasonography (US) to detect treatable vascular complications and ensure graft survival. The first postoperative Doppler US examination is performed fairly early on the first postoperative day, before surgical wound closure has been performed. The immediate postoperative images, obtained when the effects of surgery are very recent, often reveal an array of findings that may appear alarming but that tend to normalize within a few days and are compatible with changes related to the surgery itself. These findings include a starry-sky appearance of reperfusion hepatic edema, transient foci of increased echogenicity, pneumobilia, small fluid collections, perihepatic hematomas, pleural effusion, temporary elevation of hepatic arterial velocity, transient elevation of resistive index (RI), decreased RI with tardus parvus waveform, increased portal venous flow and mono- or biphasic waveforms of the hepatic veins. Most of these changes revert to normal in the first postoperative week; deterioration atypical of transient changes requires further evaluation.     

Pediatric liver transplantation. Part II. Diagnostic imaging in postoperative management

The postoperative diagnostic imaging examinations of 44 children who underwent 59 orthotopic liver transplantations were reviewed. The imaging modalities used for the evaluation of suspected complications include plain roentgenography, ultrasonography (US), computed tomography (CT), nuclear scintigraphy, arteriography, percutaneous and operative cholangiography, and endoscopic retrograde cholangiopancreatography. The main postoperative complications included ischemia, thrombosis (hepatic artery and portal vein), infarction, obstruction or leakage of the biliary anastomosis, hepatic and perihepatic infection, and allograft rejection. US, the most frequently used abdominal imaging modality, was best suited for detection of biliary duct dilatation, fluid collections in or around the transplanted liver, and hepatic arterial, inferior vena caval, and portal vein thrombosis. CT was especially helpful in corroborating findings of infection and in locating abscesses. Technetium 99m sulfur colloid (early- and late-phase imaging) provided a sensitive, although nonspecific, means of assessing allograft vascularization and morphology. Angiography showed vascularity most clearly, and cholangiography was the most useful in the assessment of bile duct patency. A diagnostic imaging algorithm is proposed for evaluation of suspected complications.     

Ultrasound and computed tomographic evaluation in hepatic transplantation

Ultrasound and CT are valuable in the non-invasive evaluation of complications of hepatic transplantation. Ultrasound is particularly helpful in detecting biliary obstruction and in documenting vascular patency. As with renal transplantation, the value of US in the assessment of rejection will likely increase with time. Computed tomography is most valuable in identifying large parenchymal abnormalities and abdominal fluid. Both US and CT can be used to guide diagnostic and therapeutic percutaneous procedures in hepatic transplant recipients.     

肝移植术后并发症的CT和MRI诊断

目的:分析肝移植术后各种并发症的CT、MRI表现,评价CT、MRI在肝移植术后并发症中的诊断价值。方法:回顾性分析24例肝移植术后发生并发症的患者的CT、MRI资料,全部病例并发症均经手术、肝组织活检或血管、胆道造影证实。结果:24例患者CT、MRI诊断门脉主干吻合口狭窄4例;肝动脉狭窄3例;下腔静脉吻合口狭窄1例;胆管吻合口狭窄4例;肝门水平非吻合口狭窄5例;移植排异反应4例,肝癌复发7例。结论:CT、MRI能发现大部分肝移植术后并发症,是诊断肝移植术后并发症的有效方法。     

Imaging of liver transplantation

Liver transplantation (LT) is the treatment of choice for end-stage chronic liver disease, fulminant liver failure and early stage hepatocellular carcinoma. As discussed in this review, state-of-the-art imaging modalities including ultrasonography (US), computed tomography (CT) and magnetic resonance imaging (MRI) play a pivotal role in the selection of patients and donors, as well as in early detection of those complications at risk of impairing graft function and/or survival. We also illustrate main imaging findings related to the wide spectrum of clinical problems raised by LT.     

Multidetector CT in pre- and post-operative evaluation of living-related liver transplantation

Objective

To assess the role of multi-detector CT (MDCT) in the pre and post operative evaluation of both potential donors and recipients for living related liver transplantation (LRLT).

Material and Methods

This prospective study included 26 patients for LRLT and their corresponding donors. For preoperative assessment, all subjects were evaluated by triphasic CT abdomen. CT angiography (CTA) with 3D reconstruction and CT volumetry was additionally done for donors. CT findings were compared to surgical results as gold standard reference. In post-operative evaluation, CT abdomen was performed at least once after transplantation for all recipients and for indicated donors. CTA was done for indicated recipients when US findings were inconclusive.

Results

No statistically significant difference was found between CT volumetry and intraoperative findings. Compared to surgical findings, MDCT identified hepatic arterial and portal venous anatomy with 100% sensitivity and specificity, while for hepatic venous anatomy; it showed sensitivity and specificity of 85.7% and 84.2%. Biliary complications and fluid collections were the commonest in recipients and donors respectively.

Conclusion

MDCT is a single comprehensive non-invasive and accurate imaging modality for preoperative evaluation of liver parenchyma, hepatic vascular anatomy and graft volume and postoperative complications in donors and recipients of LRLT.     

Liver transplantation: diagnostic imaging in the preoperative assessment]

The correct selection of patients for liver transplantation, which is essential for surgical success, requires thorough radiological evaluation. The authors present their experience on 94 pretransplant adult patients that underwent a total of 251 diagnostic exams (Doppler US, CT, angiography and cholangiography) and interventional radiology maneuvers (biopsy, chemoembolization, biliary drainage). Three sclerosing cholangitis, 3 Budd-Chiari syndromes and 20 hepatocellular carcinomas in cirrhotic patients were identified; venous collaterals were present in 62.7% of the cases, 12.8%, of which had important spontaneous porto-systemic shunts; 6 patients had portal thrombosis; 20 arterial variations were found. Interventional maneuvers were useful and free of complications. US, CT and angiographic findings of each patient were compared. Integrating informations from different exams allowed a significant increase in the accuracy of diagnostic conclusions. Thanks to interventional maneuvers 5 patients could be selected for transplantation (hepatic arterial lipiodolization stopped the growth of 4 hepatic neoplasms; 2 infected fluid collections were sterilized by percutaneous US-guided drainage and topic therapy.     

Lipiodol UltraFluid in the imaging diagnosis of hepatocarcinoma with cirrhosis

Fifty patients with HCC associated with hepatic cirrhosis underwent intra-arterial injection of Lipiodol UltraFluid (LUF) during diagnostic DSA of liver parenchyma, 42 of them for a complete chemotherapeutic treatment, 8 for an isolated diagnostic control. LUF is known to be specifically captured by HCC neoplastic tissue, with long-term persistence in the lesion if injected in the arterial hepatic tree; this is not the case with other focal hepatic masses. Therefore LUF opacification can be used to demonstrate small daughter tumors not shown by CT or US in cases with evidence of HCC, or to diagnosis HCC in clinically positive patients with no evidence of tumor at non-invasive screening. In our series of patients, accumulation of LUF in the HCC was observed in 100% of the cases, with no false negatives. Two false positives (4%) were observed, due to CT being performed too early (it should be performed not sooner than 10 days after the injection). Overall DSA accuracy was 78%, with 22% false negatives. In 14% of the cases DSA was positive for HCC in patients with aspecific noninvasive screening. CT, performed 10 days after LUF injection, demonstrated HCC daughter tumors not depicted by US, conventional CT, and angiography, in 34% of the cases, and in 9% of the patients only CT/LUF was able to show HCC in clinically positive cases with no evidence of tumor on other imaging techniques. Specificity, sensitivity and over-all accuracy were thus 100% in our series; LUF was well tolerated by the patients, and no technical complications were observed. In our opinion, the diagnostic DSA and CT/LUF is justified only for the typification of suspected focal nodules unsuitable for biopsy: in other instances, especially in case of HCC with positive biopsy/clinical findings and focal nodular mass, the technique should be directly employed as a therapeutic approach, with the injection of lipiodolized agents to treat both primary and daughter nodules after surgery in operable patients, and to begin chemoembolization treatment in patients with intrahepatic polyfocal diffusion. DSA and LUF are therefore of primary importance in the diagnosis and therapeutic flow-chart of HCC associated with hepatic cirrhosis.     

Advanced dynamic flow imaging with contrast-enhanced ultrasonography for the evaluation of tumor vascularity in liver tumors

To examine the usefulness of advanced dynamic flow imaging in diagnosing hepatic tumor and in assessing therapeutic effects in patients with hepatocellular carcinoma (HCC) and metastatic hepatic tumor, we performed contrast-enhanced ultrasonography (US) with Levovist, a microbubble contrast agent. Twenty-two patients of 35 HCC nodules infected with hepatitis C virus (HCV) and six patients with metastatic liver nodules were studied. They were diagnosed as having HCC or metastasis with helical dynamic computed tomography (CT) and/or celiac angiography. Tumor vascularities in the early arterial and postvascular phases were assessed by real-time scanning of advanced dynamic flow imaging and intermittent interval-delay scanning of contrast pulse subtraction imaging with a wide-band power Doppler technology. All patients showed hypervascular enhancement of HCC on contrast-enhanced US and/or dynamic CT. The advanced dynamic flow could be obtained as vascular and perfusion images of hepatic tumors. Tumor vascularities, including tumor vessels and parenchymal flow, were able to demonstrate in 27 of 29 nodules including 17 patients with 27 HCC nodules and 2 patients with 2 metastatic nodules before radiofrequency ablation (RFA) treatment by the advanced dynamic flow on contrast-enhanced harmonic US. Two nodules gave insufficient dynamic flow which were located approximately 12 cm in depth from the body surface. The advanced dynamic flow, which was done 7-10 days after RFA, indicated disappearance of the tumor vessels in 27 of visible 27 nodules. The study on early phase of helical dynamic CT revealed the same results as noted in early vascular phase of dynamic flow US. No major complication of RFA procedure was noted. The results indicated that contrast-enhanced advanced dynamic flow imaging on US clearly depicted intratumoral vascularity in real time and thus it is useful to diagnose and assess therapeutic efficacy in patients with HCC and metastatic liver tumor.     

Hepatic adenomas: imaging and pathologic findings.

Hepatocellular adenoma is a rare benign lesion that is most often seen in young women with a history of oral contraceptive use. It is typically solitary, although multiple lesions have been reported, particularly in patients with glycogen storage disease and liver adenomatosis. Because of the risk of hemorrhage and malignant transformation, hepatocellular adenomas must be identified and treated promptly. At pathologic analysis, hepatocellular adenoma is usually a well-circumscribed, nonlobulated lesion, and at gross examination, resected adenomas frequently demonstrate areas of hemorrhage and infarction. Most adenomas are not specifically diagnosed at ultrasonography (US) and are usually further evaluated with computed tomography (CT) or other imaging modalities. Color Doppler US may help differentiate hepatocellular adenoma from focal nodular hyperplasia. Multiphasic helical CT allows more accurate detection and characterization of focal hepatic lesions. Hepatocellular adenomas are typically bright on T1-weighted magnetic resonance images and predominantly hyperintense relative to liver on T2-weighted images. The prognosis of hepatic adenoma is not well established. Criteria that guide treatment include the number and size of the lesions, the presence of symptoms, and the surgical risk incurred by the patient. Understanding the imaging appearance of hepatocellular adenoma can help avoid misdiagnosis and facilitate prompt, effective treatment.     

The radiologist’s role in managing paediatric liver transplantation: personal experience with 40 patients

PURPOSE: The aim of our study was to evaluate the radiologist's role in managing paediatric orthotopic liver transplantation (OLT) through a retrospective review of our experience in diagnosing and treating post-OLT complications. MATERIALS AND METHODS: Forty children (mean age 4.6 years) underwent 44 OLTs over 71 months. The follow-up period (mean 724 days) was divided into three phases: hospital stay, up to three months after discharge and subsequent period. The number and type of radiological examinations, radiologically detectable complications and interventional procedures were analysed. RESULTS: Most examinations were carried out with ultrasound (US) (859/931 of all radiological studies performed during the first two phases, 92.3%). Colour-Doppler US enabled early detection and treatment of all vascular complications (9/40, 22.5% of patients; 13 complications in nine patients, eight arterial and five portal complications; 1.4 for each patient with complications). Computed tomography (CT) or angiography was very rarely employed. US also detected biliary complications (11 patients, 27.5%: three cases of segmental ducts excluded from the anastomosis, four cases of stenosis of the biliodigestive anastomosis, one lithiasis, three stenoses associated with lithiasis), which were successfully managed in 75% of the cases treated with interventional radiology procedures (percutaneous bilioplasty and/or lithotripsy). At the time of writing this paper, the patient survival rate was 100%, and the organ survival rate was 91% (40/44). There were four re-transplantations: three due to hepatic artery thrombosis and one to biliary stenosis with lithiasis. CONCLUSIONS: The radiologist's role is fundamental for early sonographic diagnosis of post-OLT complications in children. Vascular complications are often associated in a single patient, and early treatment may improve the prognosis. Interventional radiology represents a safe and effective treatment for many biliary complications.     

Evaluation of peripheral arterial bypass grafts with multi-detector row CT angiography: comparison with duplex US and digital subtraction angiography

PURPOSE: To assess the technical feasibility of multi-detector row computed tomographic (CT) angiography in the assessment of peripheral arterial bypass grafts and to evaluate its accuracy and reliability in the detection of graft-related complications, including graft stenosis, aneurysmal changes, and arteriovenous fistulas. MATERIALS AND METHODS: Four-channel multi-detector row CT angiography was performed in 65 consecutive patients with 85 peripheral arterial bypass grafts. Each bypass graft was divided into three segments (proximal anastomosis, course of the graft body, and distal anastomosis), resulting in 255 segments. Two readers evaluated all CT angiograms with regard to image quality and the presence of bypass graft-related abnormalities, including graft stenosis, aneurysmal changes, and arteriovenous fistulas. The results were compared with McNemar test with Bonferroni correction. CT attenuation values were recorded at five different locations from the inflow artery to the outflow artery of the bypass graft. These findings were compared with the findings at duplex ultrasonography (US) in 65 patients and the findings at conventional digital subtraction angiography (DSA) in 27. RESULTS: Image quality was rated as good or excellent in 250 (98%) and in 252 (99%) of 255 bypass segments, respectively. There was excellent agreement both between readers and between CT angiography and duplex US in the detection of graft stenosis, aneurysmal changes, and arteriovenous fistulas (kappa = 0.86-0.99). CT angiography and duplex US were compared with conventional DSA, and there was no statistically significant difference (P >.25) in sensitivity or specificity between CT angiography and duplex US for both readers for detection of hemodynamically significant bypass stenosis or occlusion, aneurysmal changes, or arteriovenous fistulas. Mean CT attenuation values ranged from 232 HU in the inflow artery to 281 HU in the outflow artery of the bypass graft. CONCLUSION: Multi-detector row CT angiography may be an accurate and reliable technique after duplex US in the assessment of peripheral arterial bypass grafts and detection of graft-related complications, including stenosis, aneurysmal changes, and arteriovenous fistulas.     

Infected bilomas and hepatic artery thrombosis in infant recipients of liver transplants. Interventional radiology and medical therapy as an alternative to retransplantation

Fifteen children less than 12 kg in weight underwent transplantation of the liver for biliary atresia; eight survived. Five of the eight survivors had thrombosis of the hepatic artery without portal vein thrombosis. Three of the five patients with hepatic artery thrombosis developed infected bilomas, which were drained percutaneously under ultrasonographic (US) or computed tomographic (CT) guidance. Concurrent therapy with antibiotics and hyperoxygenation resulted in resolution of these intrahepatic collections. Although it had been thought that thrombosis of the hepatic artery most often results in necrosis of the graft and requires retransplantation, the five patients in this study survived without retransplantation. Diagnosis of hepatic artery thrombosis was achieved with the use of Doppler US in four cases, CT in four cases, and angiography in two cases. Duplex Doppler US is the preferred imaging modality.     

Hepatic haemodynamics: interrelationships between contrast enhancement and perfusion on CT and Doppler perfusion indices.

This study compares three techniques that evaluate hepatic haemodynamics for the detection of metastatic liver disease to determine the interrelationships between the techniques and to assess their equivalence. The three techniques studied were dedicated CT measurements of hepatic enhancement, CT measurements of perfusion and Doppler perfusion indices. 53 patients with proven malignancies of either breast or colon underwent a single location dynamic CT for measurement of hepatic perfusion and enhancement, whilst a subset of 12 patients underwent both CT perfusion and Doppler perfusion studies. Statistically significant correlations were found between CT arterial phase enhancement and CT arterial perfusion (r=0.612, p<0.001), and between both of these parameters and Doppler arterial flow (r=0.867, p<0.001 and r=0.842, p<0.001, respectively). Significant correlations were also found between both the ratio of CT arterial enhancement to peak enhancement and the CT arterial perfusion with the Doppler perfusion index (r=0.797, p=0.002 and r=0.725, p=0.008, respectively). Combined CT arterial and portal perfusion correlated with peak liver enhancement (r=0.614, p< 0.001), but Doppler measurements of portal flow did not correlate with any CT parameter. Increased arterial enhancement, perfusion or flow are valuable additional radiological signs for the presence of hepatic metastases that can be elicited by incorporating any one of these methods into existing imaging protocols.     

Transient hepatic attenuation difference (THAD) in patients without neoplasm: frequency, shape, distribution, and causes.

Transient hepatic attenuation difference (THAD) is a valuable finding in detecting hypervascular lesions. However, similar findings are also observed in patients even without known hepatic diseases. We elucidate the characteristic findings and the causes of THAD in patients without hepatic neoplasm in this article. Dual-phased contrast-enhanced CT studies performed in 450 patients were reviewed, and THAD was observed in 42 (9.3%). THAD was linear or wedge-shaped and was seen contiguous to the liver surface with a relatively obscure margin in 40 of the 42 cases. The most common cause of THAD was chronic cholecystitis followed by previous biliary surgery. THAD was also seen in 30 patients with no hepatic diseases in whom it had a tendency to locate around the gallbladder fossa or in the periphery of the liver particularly in the left lobe. The knowledge of the prevalence, shape, distribution and causes of THAD is essential for the evaluation of contrast-enhanced CT images obtained during the arterial phase.     

Imaging of vascular complications after hepatic transplantation

Vascular complications after hepatic transplantation can compromise graft and patient survival. Angiography defines the need for revascularization or retransplantation, but the value of noninvasive imaging in this setting is not clear. To assess the relative merit of noninvasive imaging techniques (sonography, scintigraphy, CT, and MR), we retrospectively reviewed 19 major vascular complications that occurred in 15 of 98 hepatic recipients over a 3 1/2-year period. Portal venous thrombosis was seen in seven patients, donor aortic or hepatic arterial thrombosis in seven, and inferior vena caval thrombosis in five. Sonography provided the initial diagnosis of portal venous thrombosis in three, arterial compromise in five, and caval obstruction in four. CT was the first diagnostic examination to identify portal occlusion in two, donor aortic thrombosis in one, and inferior vena caval thrombosis in one. Scintigraphy and MR imaging provided complementary data. Both sonography and CT are useful in the evaluation of vascular complications that occur after hepatic transplantation; however, neither is sufficiently sensitive to obviate angiographic assessment.     

Retrospective study of 23 cases of hepatic infarction: CT findings and pathological correlations

PURPOSE: The aim of this study was to retrospectively review the cases of hepatic infarction diagnosed at our institute using conventional, spiral and multislice computed tomography (CT) over the last decade in order to describe its morphological and density characteristics and define its possible etiopathogenesis. MATERIALS AND METHODS: Twenty-three consecutive patients aged 27-65 years with hepatic infarction were studied by CT at our institute over a period of about 10 years. A conventional CT unit was used in seven patients, a helical CT scanner in ten and a multislice CT in six. CT was performed before and after the administration of 130-150 cc of contrast material infused at a rate of 3-3.5 ml/s. RESULTS: CT showed hepatic infarction due to arterial causes in 19 cases, 11 of which were in liver transplant patients. The infarction was related to right hepatic artery embolisation to control haemorrhage (one case), chemoembolisation of a multifocal hepatocarcinoma in a cirrhotic liver (one case), arterial mesenteric infarction due to thromboembolism (two cases), necrotising pancreatitis (one case), surgery in pancreatic cancer invading the hepatic artery (one case), pancreaticoduodenectomy (two cases), portal thrombosis in a young woman with pregnancy-related clotting disorder (one case), haemolytic anaemia, elevated liver enzymes, low platelet count (HELLP) syndrome (one case); eclampsia and disseminated intravascular coagulation (DIC) (one case) and acute exacerbation of Budd-Chiari syndrome (one case). At CT scans, hepatic infarction was depicted as a hypodense parenchymal area, at times triangular in shape, with sharp peripheral contours (12 cases) or as a rounded central or marginal area (four cases) with irregular appearance (three cases), with lobar extension (two cases) and ill-defined shape (two cases). Moreover, CT showed intralesional gas not correlated to bacterial infection (two cases). In all surgical cases, the results were confirmed by pathology. CONCLUSIONS: CT is the method of choice in the diagnosis of hepatic infarction, providing useful information regarding site, morphology, and extent of the lesion. Furthermore, in most cases, CT is able to suggest the possible aetiology and guide appropriate management.     

螺旋CT动脉门脉造影在小肝癌诊断中的价值

目的：用螺旋ＣＴ动脉门脉造影（ＳＣＴＡＰ）评价肝癌并与超声（ＵＳ）及螺旋ＣＴ双期扫描进行检出敏感性和定性准确性比较研究。方法：肝癌４１例,行ＳＣＴＡＰ后分析病灶灌注特征,统计各种方法病灶检出数,计算检出敏感性及定性准确性并行统计学处理。结果：４１例共检出≤３ｃｍ病灶４５个,ＳＣＴＡＰ检出敏感性为９５．５％,双期扫描肝动脉期、门静脉期及双期合计的检出敏感性分别为：８８．８％、６８．８％、９１．１％,ＳＣＴＡＰ与ＵＳ（６６．６％）和双期扫描门脉期相比有显著性差异（ｐ＜０．０１）。其定性准确性为（９５．３％）,明显高于ＵＳ（８０．０％）。结论：ＳＣＴＡＰ能可靠反映小肝癌、肝实质血流灌注特征,明显提高病灶检出敏感性及定性准确性。螺旋ＣＴ动脉造影（ＳＣＴＡ）显示病变动脉血管最佳,两者结合可增加诊断特异性。