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IntroductionComputed tomography and magnetic resonance imaging are able to demonstrate and to diagnose hepatic focal nodular hyperplasia when a typical pattern of a well-circumscribed lesion with a central scar is present.Our aim is to propose the split-bolus multidetector-row computed tomography technique as an alternative to the conventional triphasic technique in the detection and characterization of focal nodular hyperplasia to reduce the radiation dose to the patient.To the best of our knowledge, this is the first report regarding the application of the split-bolus computed tomography technique in the evaluation of hepatic focal nodular hyperplasia.Case presentationWe describe a case of focal nodular hyperplasia of the liver in a 53-year-old Caucasian woman (weight 75Kg) with a colorectal adenocarcinoma histologically confirmed. An innovative split-bolus multidetector-row computed tomography technique was used that, by splitting intravenous contrast material in two boli, combined two phases (hepatic arterial phase and portal venous phase) in a single pass; a delayed (5 minutes) phase was obtained to compare the findings with that of triphasic multidetector-row computed tomography.ConclusionsSplit-bolus multidetector-row computed tomography was able to show the same appearance of the lesion as the triphasic multidetector-row computed tomography technique.This is the first case demonstrating the effectiveness of the split-bolus multidetector-row computed tomography technique in the detection and characterization of focal nodular hyperplasia with a significant reduction in radiation dose to the patient with respect to triphasic multidetector-row computed tomography technique.

BackgroundIn oncologic patients, the liver is the most common target for metastases. An accurate detection and characterization of focal liver lesions in patients with known primary extrahepatic malignancy are essential to define management and prognosis.ObjectivesTo assess the diagnostic accuracy of the split-bolus multidetector-row computed tomography (MDCT) protocol in the characterization of focal liver lesions in oncologic patients.Patients and MethodsWe retrospectively analyzed the follow-up split-bolus 64-detector row CT protocol in 36 oncologic patients to characterize focal liver lesions. The split-bolus MDCT protocol by intravenous injection of two boluses of contrast medium combines the hepatic arterial phase (HAP) and hepatic enhancement during the portal venous phase (PVP) in a single-pass.ResultsThe split-bolus MDCT protocol detected 208 lesions and characterized 186 (89.4%) of them: typical hemangiomas (n = 9), atypical hemangiomas (n = 3), cysts (n = 78), hypovascular (n = 93) and hypervascular (n = 3) metastases. Twenty two (10.6%) hypodense lesions were categorized as indeterminate (≤5 mm). The mean radiation dose was 24.5±6.5 millisieverts (mSv).ConclusionThe designed split-bolus MDCT technique can be proposed alternatively to triphasic MDCT and in a single-pass to PVP in the initial staging and in the follow-up respectively in oncologic patients.

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Federico et al. concerning with the role of chest computed tomography (CT) in the surveillance of children affected by highrisk neuroblastoma.[1] According to the authors, the omission of surveillance chest CT imaging can save 35-42% of the radiation burden without compromising disease detection in those patients with non-thoracic high-risk neuroblastoma at diagnosis.[1] We have developed a novel split-bolus technique for multi-detector computer tomography (MDCT) able to reduce the radiation dose and to ensure diagnostic accuracy in case of non-thoracic neuroblastoma. It combines in a single pass the arterial and venous phases, allowing the detection of hypo-or hyper-vascular lesions, together with lymph node involvement and related distant metastases.[2-3] The split-bolus 64-detector row CT protocol is based on a single acquisition of the chest-abdomen-pelvis after intravenous injection of 2 ml/kg of contrast medium (Iopamiro 350 mg/ml; Bracco, Milan, Italy), split by an automatic power injector (Medrad Stellant, Indianola, PA) into two boluses. We have applied this protocol in a 45-kg and 14-year-old patient for the detection of a retroperitoneal neuroblastoma, whose diagnosis was subsequently confirmed on the surgical specimen by histology. The first bolus consisted of 54 ml contrast material injected at 1.3 ml/sec and followed by 15 ml saline solution at the same flow rate, in order to obtain an adequate parenchymal and venous enhancement. The second bolus consisted of 36 ml contrast material administrated at 1.3 ml/sec and followed by 15 ml saline solution at the same flow rate, in order to obtain the late arterial phase. A manual bolus tracking was set up, raising the threshold value at 500 HU, by placing a circular region of interest (ROI) in the descending aorta. The scan was cranio-caudally performed, starting from the pulmonary apex toward the pubic symphysis, after a 6 sec delay from the arrival of the contrast material in aorta. The inherent delay in the bolus tracking was necessary to move the scan table, give breath-hold instructions to the patient, and tune the gantry parameters. The following acquisition parameters were applied: gantry rotation speed 0.75 sec; slice thickness 2.5 mm; reconstruction index 1.25; pitch 0,935:1; tube voltage 120 kVp with automatic tube current (mA) using z-axis modulation. The examination was completed with axial, coronal and sagittal multiplanar reconstructions (Fig. 1).The split-bolus MDCT allowed tumor detection and its extension, without compromising the disease staging in this patient. The dose length product (DLP) was 98.1 mGy.cm and this led us to support the rationale proposed by Federico et al. aimed to possibly avoid a radiation burden, [1] in particular in children affected by non-thoracic neuroblastoma. Moreover, by combining the split-bolus MDCT in the diagnostic phase to the proposed surveillance criteria, a further radiation dose reduction could be Fig. 1. Split-bolus whole body MDCT: the axial (A), coronal (B), and sagittal (C) multiplanar reconstructi...