CT of blunt abdominal and pelvic vascular injury

Computed tomography (CT) has been shown to be increasingly useful in the evaluation of blunt trauma patients with suspected abdominopelvic vascular injuries. CT findings of abdominopelvic vascular insult may be broadly characterized as end-organ abnormalities or direct evidence of vascular injury. End-organ abnormalities implying an underlying vascular insult include identifying an area of relative hypoperfusion in solid organ injury. Direct evidence of a vascular injury includes identifying an irregular or thrombosed vessel or an area of active hemorrhage, among other findings. This review article aims to review and illustrate these findings of blunt abdominopelvic vascular trauma. Also, evolving lessons from our level I trauma center in the use of multiphasic imaging to further characterize sources of a vascular blush and the differentiation of arterial from venous sources of active hemorrhage are discussed.     

Helical computed tomography of liver injuries: A trial of dual phase imaging

This study was performed to evaluate whether consecutive arterial phase and portal venous phase scans of the upper abdomen are contributory in the evaluation of the liver in patients with blunt abdominal trauma. The purpose of the study was to determine whether such dual acquisition using helical computed tomography (HCT) provides improved definition of injuries and significant information about the dynamics of posttraumatic hemorrhage.During a 10-month period, all patients referred for evaluation of blunt abdominal trauma were scanned using a dual phase imaging technique. Two consecutive and comparable scan clusters were programmed to study the upper abdomen, with a slice collimation of 10 mm and a 11 pitch. Intravenous contrast medium was delivered at a rate of 2 ml/sec for a total of 125 ml, with scan delays of 30 and 70 seconds (arterial and venous phases of hepatic enhancement).Thirty-two patients with hepatic lacerations were encountered, and the images from both acquisitions were compared and graded according to lesion conspicuity. The presence of contrast medium extravasation associated with parenchymal injuries was also recorded.In 23 (72%) of the 32 patients, the liver injuries were better defined in the portal venous phase, and in eight (25%) patients, the lesions were equally shown in both phases. In only one case, the lesion was better demonstrated in the arterial phase. Contrast medium extravasation was noted in two patients at the site of liver laceration. In three additional cases, contrast medium extravasation was also noted in associated splenic injuries. In all of these patients, the extravasation (bleeding laceration) was seen only in the images corresponding to the portal venous phase.Dual phase HCT of the upper abdomen does not provide significant additional information in the evaluation of patients with liver injuries resulting from blunt abdominal trauma. With a single scan cluster through the upper abdomen after a 70-second injection-scan delay, lesion definition is optimal, and vascular opacification remains adequate.     

CT diagnosis of splenic infarction in blunt trauma: imaging features, clinical significance and complications

AIM: The object of this study is to describe the appearance, complications, and outcome of segmental splenic infarctions occurring after blunt trauma using computed tomography (CT). MATERIALS AND METHODS: Thirteen blunt trauma patients were identified with splenic infarction on contrast-enhanced CT. CT images were retrospectively reviewed and the percentage of infarcted splenic tissue and presence of splenic injury separate from the site of infarction were identified. Splenic angiograms were reviewed and follow-up CT images were assessed for interval change in the appearance of the infarcts. RESULTS: The mean age of patients was 32 years and the most common mechanism of injury was road traffic accident. The majority (54%) had 25-50% infarction of the spleen. Splenic angiograms were performed in nine patients and seven demonstrated wedge-shaped regions of decreased perfusion corresponding to the infarction seen on CT with no need for intervention. Eleven patients underwent a follow-up CT that demonstrated the following: no significant change in six, near-complete resolution in two, delayed appearance of infarction in one, abscess formation in one, and delayed splenic rupture in one. CONCLUSION: Segmental splenic infarction is a rare manifestation of blunt splenic trauma. The diagnosis is readily made using contrast-enhanced CT. The majority will decrease in size on follow-up CT and resolve without clinical sequelae. Resolution of infarction is also seen and these cases are best described as temporary perfusion defects. Splenic abscess or delayed rupture are uncommon complications that may necessitate angiographic or surgical intervention.     

Optimizing multidetector CT for visualization of splenic vascular injury. Validation by splenic arteriography in blunt abdominal trauma patients

Nonoperative management of blunt splenic injury is the treatment of choice in hemodynamically stable patients. Detection of vascular injury by multidetector CT (MDCT) is the most significant factor predicting the need for endovascular treatment. This study evaluated the timing of the appearance of vascular lesions during angiography. Images from 20 patients embolized for pseudoaneurysms (PSA) were evaluated. Angiograms were reviewed for phase and timing of PSA. Admission MDCT was reviewed for injury grade and PSA. Initial MDCT evaluation indicated grade III and IV splenic injuries in 9 and 11 patients, respectively. PSA was seen on MDCT in 14/20 (70%) patients. Time from opacification of the aorta to vascular injury was 1.32 s for arterial phase injuries compared with 2.05 s for postcapillary injuries (P = 0.097). Angiography demonstrated 15 vascular injuries during the arterial and 5 in the venous phase. Of injuries seen during arterial phase angiography, 10/15 (66%) were identified on MDCT. Of the five injuries that exhibited postcapillary-phase findings, 4/5 (80%) demonstrated PSA (P = 0.5). Vascular lesions are a better indicator of subsequent clinical deterioration than splenic injury grade. PSAs are more frequently seen in postcapillary vascular injuries than arterial phase lesions with the current timing of MDCT. In a subset of patients in whom splenic injury grades III and IV warrant angiography, PSAs are not initially demonstrated on MDCT. Therefore, alteration of MDCT timing parameters to better correlate with arterial phase angiography may improve initial diagnosis of vascular injury.     

Irreversible Electroporation Ablation of Malignant Hepatic Tumors: Subacute and Follow-up CT Appearance of Ablation Zones

PurposeTo describe findings on contrast-enhanced computed tomography (CT) images of malignant hepatic tumors 24–72 hours after percutaneous ablation by irreversible electroporation (IRE) and at midterm follow-up.Materials and MethodsRetrospective analysis of 52 malignant liver tumors—30 primary hepatic tumors and 22 hepatic metastases—in 34 patients (28 men and 6 women, mean age 64 y) treated by IRE ablation was performed. Ablation zones were evaluated by two examiners in a consensus reading by means of a dual-phase CT scan (consisting of a hepatic arterial and portal venous phase) performed 24–72 hours after IRE ablation and at follow-up.ResultsDuring the portal venous phase, ablation zones either were homogeneously hypoattenuating (n = 36) or contained heterogeneously isoattenuating or hyperattenuating (n = 16) foci, or both, in a hypoattenuating area. Of 52 lesions, 38 included gas pockets. Peripheral contrast enhancement of the ablation defect was evident in 23 tumors during the arterial phase and in 36 tumors during the portal venous phase. Four tumors showed intralesional abscesses after the intervention. At follow-up (mean, 4.7 mo), the mean volume of the ablation defects was reduced to 29% of their initial value.ConclusionsBecause normal findings on contrast-enhanced CT images after IRE ablation may be very similar to the typical characteristics of potential complications following ablation, such as liver abscesses, CT scans must be carefully analyzed to distinguish normal results after intervention from complications requiring further treatment.     

钝性肝脾肾损伤的CT平扫与增强扫描比较

目的:比较CT平扫与增强扫描对肝脾肾钝性损伤的诊断能力。方法:回顾性分析临床疑似钝性肝脾肾损伤,并经手术和临床观察证实的CT平扫和增强扫描的患者84例。结果:平扫确定的损伤:肝12例,脾25例,肾5例;平扫可疑损伤:肝22例,脾15例,肾5例。增强确定的损伤:肝32例,脾40例,肾12例(全肾梗塞1例,局限性梗塞3例);对比剂外溢(活动性出血)3例;无可疑损伤。平扫无异常而增强确定有损伤:肝10例,脾5例,肾2例。增强显示的损伤灶比平扫范围明显大、病灶多、界限清楚。结论:CT增强扫描显示肝脾肾损伤明显优于平扫,延时扫描有助于发现活动性出血,应常规增强扫描。     

Emergent transcatheter arterial embolization in hemodynamically unstable patients with blunt splenic injury

RATIONALE AND OBJECTIVES: Splenic preservation is currently the trend for treatment of patients with splenic trauma to avoid complications of splenectomy. This study aimed to evaluate the feasibility of emergent transcatheter arterial embolization (TAE) for hemodynamically unstable patients with blunt splenic injury. MATERIALS AND METHODS: In a period of 2 years, 65 patients of blunt splenic trauma were studied. Patients with initial systolic blood pressure < 90 mmHg and showed initial response including rapid response and transient response to the emergent fluid resuscitation were included. Angiography and TAE was undertaken if contrast medium extravasation or pseudoaneurysm formation was noted in the computed tomography (CT) images, according to the criteria of American Association for the Surgery of Trauma. All patients who underwent TAE were admitted for observation of the possibility of delayed rupture. RESULTS: Thirteen hemodynamically unstable patients who were responsive to initial fluid resuscitation received angiography due to abnormal CT findings including contrast agent extravasation in 12 patients, 2 patients with arteriovenous fistula, and 8 patients with pseudoaneurysm formation. TAE was successfully performed in all of these 13 patients, including 2 patients with associated left renal injuries and 1 patient associated with bilateral internal mammary arteries injuries, without complications. CONCLUSIONS: TAE is a safe and effective procedure for treating blunt splenic injury even in hemodynamically unstable patients who responded to initial fluid resuscitation.     

Nonsurgical management of blunt splenic injury: use of CT criteria to select patients for splenic arteriography and potential endovascular therapy

PURPOSE: To determine if contrast material-enhanced spiral computed tomography (CT) can be used to select patients with blunt splenic injuries to undergo arteriographic embolization. MATERIALS AND METHODS: During a 15-month period, 78 patients who were hemodynamically stable and required no immediate surgery underwent contrast-enhanced spiral CT followed by splenic arteriography. CT scans were assessed for splenic vascular contrast material extravasation or posttraumatic splenic vascular lesions. Medical records were reviewed for splenic arteriographic results and clinical outcome. RESULTS: There were 25 grade I, 12 grade II, 27 grade III, 12 grade IV, and two grade V splenic injuries. CT showed active contrast material extravasation in seven patients and splenic vascular lesions in 19 patients. At CT, splenic vascular contrast material extravasation was 100% (seven of seven patients) and a posttraumatic splenic vascular lesion was 83% (10 of 12 patients) sensitive on the basis of arteriographic or surgical outcome in predicting the need for transcatheter embolization or splenic surgery. Overall, CT had a sensitivity of 81% (17 of 21 patients), a specificity of 84% (48 of 57 patients), negative and positive predictive values of 92% (48 of 52 patients) and 65% (17 of 26 patients), respectively, and an accuracy of 83% (65 of 78 patients) in predicting the need for splenic injury treatment. CONCLUSION: Contrast-enhanced spiral CT plays a valuable role in selecting hemodynamically stable patients with splenic vascular injury who may be treated with transcatheter therapy and potentially improves the success rate of nonsurgical management.     

Detection of hepatocellular carcinoma: comparison of dynamic three-phase computed tomography images and four-phase computed tomography images using multidetector row helical computed tomography

PURPOSE: The purpose of our study was to assess the value of additional early arterial phase computed tomography (CT) imaging in the detection of hepatocellular carcinoma (HCC) by comparing three-phase and four-phase imaging by using multidetector row helical CT. METHODS: Twenty-five patients with 33 HCCs underwent four-phase helical CT imaging. The diagnosis was established by pathologic examination after surgical resection in 19 patients and by biopsy in six. Four-phase CT imaging comprises early arterial, late arterial, portal venous, and delayed phase imaging obtained 25 seconds, 45 seconds, 75 seconds, and 180 seconds after the start of contrast material injection using multidetector row helical CT. Three-phase CT images (late arterial, portal venous, and delayed phase) and four-phase CT images (early arterial, late arterial, portal venous, and delayed phase) were interpreted independently for the detection of HCC by three blinded observers on a segment-by-segment basis. Sensitivity, specificity, and area under the receiver operating characteristic (ROC) curve (Az) for three-phase CT images and four-phase CT images were calculated. The enhancement pattern of HCC was analyzed on early arterial and late arterial phase imaging. RESULTS: The mean sensitivity of three- and four-phase CT images was 94% and 93%, respectively. The differences between sensitivities were not statistically significant (all p > 0.05). The mean specificities of three- and four-phase CT images were 99% and 98%, respectively. The differences between the specificities were not statistically significantly (all p > 0.05). Neither were the mean areas under the ROC curve for four-phase CT images (Az = 0.976) and three-phase CT images (Az = 0.971) statistically significant (p > 0.05). On early arterial phase imaging, 16 HCCs were hyperattenuating and 17 HCCs were isoattenuating. On late arterial phase imaging, 24 HCCs were hyperattenuating and nine HCCs were isoattenuating. CONCLUSIONS: Additional early arterial phase imaging did not improve the detection of HCC compared with three-phase CT images, including late arterial, portal venous, and delayed phase imaging.     

Multidetector CT of blunt traumatic venous injuries in the chest, abdomen, and pelvis

Venous injuries as a result of blunt trauma are rare. Even though current protocols for multidetector computed tomography (CT) of patients with trauma are designed to evaluate primarily the solid organs and arteries, blunt venous injuries may nevertheless be identified, or at least suspected, on the basis of the multidetector CT findings. Venous injuries are associated with high morbidity and mortality rates. Diagnosis of a possible venous injury is crucial because the physical findings of a venous injury are nonspecific and may be absent. This article aims to make the radiologist aware of various venous injuries caused by blunt trauma and to provide helpful hints to aid in the identification of venous injuries. Multidetector CT technology, in combination with interactive manipulation of the raw dataset, can be useful in the creation of multiplanar reconstructed images and in the identification of a venous injury caused by blunt trauma. Familiarity with direct and indirect signs of venous injuries, as well as with examples of blunt traumatic venous injuries in the chest, abdomen, and pelvis, will help in the diagnosis of these injuries.     

Pelvic CT angiography: application to blunt trauma using 64MDCT

The evolution of multi-row detector computed tomography (MDCT) technology has resulted in evolving applications of CT angiography (CTA) in the trauma setting. In patients with significant blunt pelvic injuries, the immediate diagnosis and characterization of vascular injuries is of significant import given their morbidity and mortality in this patient population. The application of MDCT technology, specifically 64MDCT, to pelvic CTA is useful in evaluating for potential vascular injuries and may be integrated into admission trauma imaging in order to triage patients with blunt pelvic trauma to appropriate emergent intervention. This paper will discuss the use of pelvic CTA in blunt pelvic trauma and its utility in detecting and characterizing vascular injury, including the differentiation of arterial from venous hemorrhage. Protocol considerations in pelvic CTA using 64MDCT technology will be detailed as well as the integration of pelvic CTA into torso CT trauma protocols.     

Nonoperative management of traumatic splenic injuries: is there a role for proximal splenic artery embolization?

OBJECTIVE: The objective of our study was to evaluate our experience with transcatheter proximal (i.e., main) splenic artery embolization (TPSAE) in the nonsurgical management of patients with grade III-V splenic injuries, according to the American Association for the Surgery of Trauma (AAST) guidelines, and patients with splenic injuries associated with CT evidence of active contrast extravasation or blush (or cases meeting both criteria). MATERIALS AND METHODS: The records of patients with traumatic splenic injuries admitted during a 52-month period were retrospectively reviewed for patient age and sex, mechanism of injury, injury severity score (ISS), RBC transfusion requirements, AAST splenic injury CT grade, presence of active contrast extravasation or blush on CT examination, and amount of hemoperitoneum on CT examination. Demographics, CT findings, transfusion requirements, and outcome were compared using the Student's t test or chi-square test in patients undergoing standard nonoperative management and nonoperative management TPSAE-that is, TPSAE followed by nonoperative management. RESULTS: Of the 79 identified patients with splenic trauma, 67 were managed nonoperatively. Thirty-seven patients (28 men, nine women; mean age, 40 years; mean ISS, 28.8) underwent nonoperative management TPSAE and 30 patients (27 men, three women; mean age, 37 years; mean ISS, 25.1) underwent nonoperative management. Age, sex, and ISS were not significantly different between the two groups. TPSAE was always technically feasible. Splenic injuries were significantly more severe in the nonoperative management TPSAE group than in the nonoperative management group with respect to the mean splenic injury AAST CT grade (3.7 vs 2, respectively; p < 0.0001), active contrast extravasation or blush (38% [14/37] vs 3% [1/30], respectively; p = 0.0005), and hemoperitoneum grade (1.6 vs 0.8, respectively; p = 0.0006). Secondary splenectomy rate was lower in the nonoperative management TPSAE group (2.7% [1/37] vs 10% [3/30]). No procedure-related complications were encountered during early and delayed clinical follow-up. CONCLUSION: TPSAE is a feasible and safe adjunct to observation in the nonoperative management of severe traumatic splenic injuries. The secondary splenectomy rate using nonoperative management TPSAE (2.7%) is among the lowest reported despite a selection of severe injuries.     

Clinical outcome of active extravasation in splenic trauma

The purpose of this study was to determine the necessity for splenectomy in patients with active extravasation on contrast enhanced CT secondary to splenic trauma. We reviewed cases of splenic injury and classified these according to the American Association for the Surgery of Trauma (AAST) grading scale. The presence of active extravasation and associated injuries was assessed. Chart review was then performed to determine age, sex, mechanism of injury, indications for splenectomy, and clinical outcome. Of 82 cases evaluated, 12 grade I, 15 grade II, 30 grade III, 17 grade IV, and 8 grade V injuries were present. Eighteen patients were actively extravasating. Of extravasating patients, 13 eventually underwent open splenectomy or embolization and five (27.8%) were managed expectantly with success. Of grade IV injuries, 9/17 showed active extravasation, of which six underwent splenectomy. Of grade V injuries, 3/8 showed active extravasation, and all three underwent intervention. Splenectomy may not be necessary in appropriately chosen patients with active extravasation from the spleen in blunt abdominal trauma.     

CT detection of hepatic and splenic injuries: usefulness of liver window settings

OBJECTIVE. This study was designed to assess the usefulness of liver window settings when performing abdominal CT for the detection and characterization of hepatic and splenic injuries. SUBJECTS AND METHODS. We prospectively evaluated helical abdominal CT scans for hepatic and splenic injuries in 300 consecutive patients with blunt abdominal trauma over a 4-month period. There were 204 males and 96 females with a mean age of 34 years (age range, 1-87 years). For each patient, initial CT diagnosis of hepatic or splenic injury was made from images obtained with standard abdominal window settings. CT scans were then immediately reinterpreted using additional images obtained at narrow window width (liver windows). Changes in conspicuity and characterization of injury were recorded. All CT examinations were performed with helical 7-mm collimation at a pitch of 1.5 after oral ingestion of diluted barium and during bolus IV administration of 125 mL of ioversol at a rate of 2-3 mL/sec. RESULTS. We detected hepatic or splenic injuries in 34 patients (11.3%). There were 19 hepatic injuries and 18 splenic injuries. Three patients had injuries to both liver and spleen. Conspicuity of hepatic or splenic injuries was mildly increased (+1 H) on liver windows in 16 patients, whereas the injury was equally conspicuous on both liver window and standard window images in 19 cases. In no case did review of the liver windows result in a change in grade of injury or reveal an injury that was not seen on standard abdominal window images. The total increased cost for printing liver windows was $5748. CONCLUSION. Routine use of liver window settings for abdominal CT in trauma patients has little clinical usefulness and is not cost-effective.     

Blunt trauma to the spleen: ultrasonographic findings

The spleen is the most frequently injured organ in adults who sustain blunt abdominal trauma. Splenic trauma accounts for approximately 25% to 30% of all intra-abdominal injuries. The management of splenic injury has undergone rapid change over the last decade, with increasing emphasis on splenic salvage and non-operative management. Identifying the presence and degree of splenic injury is critical in triaging the management of patients. Imaging is integral in the identification of splenic injuries, both at the time of injury and during follow-up. Although CT remains the gold standard in blunt abdominal trauma, US continues to play an important role in assessing the traumatized spleen. This pictorial review illustrates the various ultrasonographic appearances of the traumatized spleen. Correlation with other imaging is presented and complications that occur during follow-up are described.     

Small (≤2 cm) atypical hepatic haemangiomas in the non-cirrhotic patient: pattern-based classification scheme for enhancement at triple-phase helical CT

Purpose

The aim of this study was to determine by triplephase helical computed tomography (CT) the appearance of atypical small (≤2 cm) hepatic haemangiomas (HHs) in the non-cirrhotic patient.

Materials and methods

We retrospectively reviewed the hepatic arterial-dominant phase (HAP), portal venous phase (PVP) and delayed-phase (DP) helical CT images of 47 patients with 52 atypical small (≤2cm) HHs associated with 34 typical small HHs. Images were assessed to identify the patterns of enhancement of atypical HHs and correlate their appearance with that of typical small HHs in the delayed phase. Interobserver variability and kappa value were calculated. Statistical significance was calculated by the Fisher exact test.

Results

The 52 atypical small HHs were categorised as follows: type 1a (hyperattenuating in the HAP, n=17), type 1b [hyperattenuating with transient hepatic attenuation difference (THAD) around the lesion in the HAP, n=12], type 2a (homogeneously hypoattenuating in the HAP or PVP, n=9), type 2b (hypoattenuating with “bright-dot” sign in the HAP or PVP, n=13) and type 3 (hypoattenuating with central enhancing area, n=1). Interobserver agreement was perfect for HHs of types 1a, 1b, 2a and 3. On DP images, the appearance of atypical small HHs was identical to that of typical small HHs in all cases (p<0.0001), with lesions showing homogeneous isoattenuation to the aorta or liver parenchyma without peripheral capsule.

Conclusions

Triple-phase helical CT scans can distinguish several types of atypical small HHs. The demonstration of patterns similar to those of typical forms on DP CT is fundamental for the diagnosis.     

增强CT对腹部实质脏器损伤的诊断价值

目的：探讨增强CT扫描检查对腹部实质脏器损伤的诊断价值。方法：回顾性分析63例经手术、血管造影及CT随访证为腹部钝性损伤病人的平扫及增强CT表现征象,并比较分析各种征象的作用。结果：本组63例中,11例（2例脾损伤,3例肝损伤,6例肾损伤）平扫换明显异常,增强CT扫描呈明显的低工改变;11例器官内或周围斑点状造影剂外渗,提示为活动性出血;29例增强 CT扫描后清楚显示裂伤部位,结论：增强CT检查对肝肾损伤的诊断明显优于平扫,还可以判断有无活动性出血等情况,对损伤程度的判断和治疗方案的制定较平扫更有价值。     

实验兔钝性肝损伤的CT动态增强表现

目的 探讨CT动态增强扫描在兔钝性肝损伤(rabbit hepatic injury,BHI)模型中的诊断价值.方法 新西兰大白兔40只,采用钢球自由落体对剑突直接撞击,建立兔BHI模型.采用美国通用(GE)公司Hispeed双螺旋CT机行肝脏平扫及增强,注射对比剂开始后8～10 s、35～40 s、120～150 s分别为肝动脉期、门脉期及平衡期.观察增强前后损伤的位置、范围、边界、肝包膜撕裂、有无活动性出血、主要肝静脉有无受累及腹腔积血的CT特征,并与大体解剖情况对比.结果 动态增强扫描显示率明显高于平扫,单一撕裂13只,多发性撕裂伤18只,肝包膜下血肿7处,肝实质内血肿9处,肝包膜裂口17只25处,活动性出血9处,主要肝静脉损伤5处;与大体解剖符合情况分别为13/13(只),18/18(只),7/9(处),9/9(处),25/30(处),9/5(处),5/4(处).按Moore分级,CT/剖腹探查结果分别为:Ⅰ级5/4只,Ⅱ级15/13只,Ⅲ级9/11只,Ⅳ级6/6只,Ⅴ级1/2只,Ⅵ级0只.结论 动态CT增强扫描尤其静脉期和平衡期对明确有无肝脏损伤及判断损伤程度具有重要的价值.     

Liver metastases from melanoma: detection with multiphasic contrast-enhanced CT.

PURPOSE: To assess the clinical utility of multiphasic computed tomography (CT) of the liver in patients with metastatic melanoma. MATERIALS AND METHODS: Nonenhanced and biphasic hepatic CT examinations were performed in 28 patients with metastatic melanoma, and liver lesion conspicuity was graded. CT studies in 20 patients met the eligibility criteria, and 13 patients had liver lesions. RESULTS: A total of 57 liver lesions were seen on CT studies: 48 on hepatic arterial phase images, 49 on portal venous phase phase images, and 30 on delayed phase images. Of eight lesions overlooked on portal venous phase images, six were seen on nonenhanced images, and six were seen on arterial phase images. Twenty-eight lesions were graded as more conspicuous on portal venous phase images; 10 were graded as more conspicuous on arterial phase images. CONCLUSION: CT images obtained only during the portal venous phase would have resulted in eight (14%) overlooked lesions, which implies that more than one phase is needed for hepatic CT in patients with malignant melanoma. The combination of nonenhanced and portal venous phase CT was as effective as the combination of arterial and portal venous phase CT in these patients. Delayed phase CT did not improve lesion detection either alone or in combination with CT at other phases.