COMPARISON OF TRANSPLENIC MULTIDETECTOR CT PORTOGRAPHY TO MULTIDETECTOR CT‐ANGIOGRAPHY IN NORMAL DOGS

The accuracy of multidetector computed tomographic (CT) angiography involving 64 detectors has not been well established. We conducted a multicenter study to examine the accuracy of 64-row, 0.5-mm multidetector CT angiography as compared with conventional coronary angiography in patients with suspected coronary artery disease. Nine centers enrolled patients who underwent calcium scoring and multidetector CT angiography before conventional coronary angiography. In 291 patients with calcium scores of 600 or less, segments 1.5 mm or more in diameter were analyzed by means of CT and conventional angiography at independent core laboratories. Stenoses of 50% or more were considered obstructive. The area under the receiver-operating-characteristic curve (AUC) was used to evaluate diagnostic accuracy relative to that of conventional angiography and subsequent revascularization status, whereas disease severity was assessed with the use of the modified Duke Coronary Artery Disease Index. A total of 56% of patients had obstructive coronary artery disease. The patient-based diagnostic accuracy of quantitative CT angiography for detecting or ruling out stenoses of 50% or more according to conventional angiography revealed an AUC of 0.93 (95% confidence interval [CI], 0.90 to 0.96), with a sensitivity of 85% (95% CI, 79 to 90), a specificity of 90% (95% CI, 83 to 94), a positive predictive value of 91% (95% CI, 86 to 95), and a negative predictive value of 83% (95% CI, 75 to 89). CT angiography was similar to conventional angiography in its ability to identify patients who subsequently underwent revascularization: the AUC was 0.84 (95% CI, 0.79 to 0.88) for multidetector CT angiography and 0.82 (95% CI, 0.77 to 0.86) for conventional angiography. A per-vessel analysis of 866 vessels yielded an AUC of 0.91 (95% CI, 0.88 to 0.93). Disease severity ascertained by CT and conventional angiography was well correlated (r=0.81; 95% CI, 0.76 to 0.84). Two patients had important reactions to contrast medium after CT angiography. Multidetector CT angiography accurately identifies the presence and severity of obstructive coronary artery disease and subsequent revascularization in symptomatic patients. The negative and positive predictive values indicate that multidetector CT angiography cannot replace conventional coronary angiography at present. (ClinicalTrials.gov number, NCT00738218.)

To explore flap thinning based on the study of the arterial structure and blood perfusion of the deep inferior epigastric artery perforator (DIEP) flap using computed tomography (CT) angiography. Clinical imaging study: Preoperative CT angiography was performed in 15 patients with DIEP flap reconstruction to investigate the vascular structure of arterial perforator. Cadaveric imaging study:10 abdominal specimens harvested from fresh cadavers were cannulated with trocar and injected with contrast medium in the deep inferior epigastric artery perforator. During the perfusion of the contrast medium in the flap,the flap was scanned by three-dimensional CT. The CT data was then sent to CT workstation and the images were processed and reformatted to study the vascular structure of arterial perforators and the blood perfusion. 75 artery perforators in clinical study and 40 artery perforators in cadaveric study were chosen and analyzed. The major deep inferior epigastric artery perforators run directly across the deep layer of adipose tissue without bifurcating beneath the Scarpa's fascia. Above the Scarpa's fascia, the artery perforators bifurcate and ultimately terminate in the subdermal vascular plexus. Blood perfusion mode: The subdermal vascular plexus served as the only pathway for blood perfusion between perforasomes. There are two different pathways for blood perfusion in the perforasome: the subdermal plexus and the existing vascular structure of perforator. Based on the vascular structure of arterial perforator and blood perfusion of the DIEP flap, thinning of the DIEP flap under the Scarpa's fascia is safe while thinning above the Scarpa's fascia should performed according to the blood supply zone of the DIEP flap.

Very short acquisition times and the increasing use of low-kilovolt protocols in standard computed tomographic (CT) angiography (CTA) examinations demand modifications in the contrast media (CM) injection regimen. The aim of this study was to optimize the use of tube voltage-adjusted CM delivery parameters, especially injection duration and iodine delivery rate (IDR), in thoracoabdominal CTA in a porcine model. Eight pigs (53-72 kg) were examined with a third-generation dual-source CT system with a dynamic CTA protocol (4-dimensional spiral, 454-mm scan length, 2.5-second temporal resolution, 70-second total acquisition time). Six CM injection protocols were applied in randomized order and intraindividually compared. The standard CTA protocol was performed at 120 kV, with an injection of 300 mg iodine/kg body weight and a flow of 5 mL/s (IDR, 1.5 g/s). On the basis of phantom measurements for the low-kilovolt CTA protocols, the iodine dosage was adjusted to 150 mg iodine/kg (70 kV) and 210 mg iodine/kg (90 kV). Therefore, either the IDR was kept constant and the injection time was reduced, or the injection time was kept constant and the IDR was reduced by modifying the CM flow or concentration. Time attenuation curves, time to peak, and peak enhancement were calculated for different locations within the aorta, renal arteries, and large veins. The heart rates were comparable among the different injection protocols (66.9-78.1 beats per minute). The average injection peak pressure depended on the flow rate and CM concentration and ranged from 42.9 to 114.7 psi. The average arterial peak enhancement was comparable for protocols with identical injection times and reduced IDR (362.4 HU [standard 120-kV protocol; 300 mg iodine/kg; IDR, 1.5 g/s], 360.0 HU [70 kV; 150 mg iodine/kg; IDR, 0.75 g/s], 365.4 HU [70 kV; 150 mg iodine/kg; IDR, 0.75 g/s; CM, 150 mg iodine/mL], 344.3 HU [90 kV; 210 mg iodine/kg; IDR, 1.1 g/s]). Higher peak enhancements could be achieved by applying protocols with identical IDR and a reduced injection time (502.5 HU [70 kV; 150 mg iodine/kg; IDR, 1.5 g/s] and 394.6 HU [90 kV; 210 mg iodine/kg; IDR, 1.5 g/s]). By adjusting the IDR, low-kilovolt CTA is able to achieve comparable aortic enhancement with a significant reduction in CM dosage. A shorter injection time at constant IDR results in higher enhancement and a narrower scan window and might be preferable for fast CTA acquisition techniques. The optimization of CM injection protocols is mandatory to achieve state-of the art CTA at low kilovolt and can reduce CM doses to patients.

To suggest a simple and robust technique used to reconstruct high-quality computed tomographic (CT) angiographic images from CT perfusion data and to compare it with currently used CT angiography techniques. Institutional review board approval was waived for this retrospective study, which included 25 consecutive patients who had had a stroke. Temporal maximum intensity projection (tMIP) CT angiographic images were created by using prior temporal filtering as a timing-insensitive technique to produce CT angiographic images from CT perfusion data. The temporal filter strength was optimized to gain maximal contrast-to-noise ratios (CNRs) in the circle of Willis. The resulting timing-invariant (TI) CT angiography was compared with standard helical CT angiography, the arterial phase of dynamic CT angiography, and nonfiltered tMIP CT angiography. Vascular contrast, image noise, and CNR were measured. Four experienced observers scored all images for vascular noise, vascular contour, detail of small and medium arteries, venous superimposition, and overall image quality in a blinded side-by-side comparison. Measurements were compared with a paired t test; P ≤ .05 indicated a significant difference. On average, optimized temporal filtering in TI CT angiography increased CNR by 18% and decreased image noise by 18% at the expense of a decrease in vascular contrast of 3% when compared with nonfiltered tMIP CT angiography. CNR, image noise, vascular noise, vascular contour, detail visibility of small and medium arteries, and overall image quality of TI CT angiograms were superior to those of standard CT angiography, tMIP CT angiography, and the arterial phase of dynamic CT angiography at a vascular contrast that was similar to that of standard CT angiography. Venous superimposition was similar for all techniques. Image quality of the arterial phase of dynamic CT angiography was rated inferior to that of standard CT angiography. TI CT angiographic images constructed by using temporally filtered tMIP CT angiographic data have excellent image quality that is superior to that achieved with currently used techniques, but they suffer from modest venous superimposition.

Computed tomographic (CT) angiography, the gold standard for diagnosing portal veinthrombosis (PVT) in humans, is poorly documented in dogs. Therefore, we retrospectivelyreviewed dogs with PVT diagnosed by CT angiography. Medical records of 13 client-owneddogs diagnosed with PVT by CT angiography were reviewed. All dogs had chronic PVT, and themost frequent clinical sign was vomiting (5/13), with pancreatitis the most frequentconcurrent disease (6/13). All dogs tested for plasma D-dimer concentration (12/12)revealed elevated levels. On CT angiography, a thrombus was detected as a non-contrastenhancement structure in the portal vessel of 13 dogs. There was no evidence of completeobstruction of the portal vein in any of the dogs. The median luminal filling of theportal vein was 60.4%. The thrombus extension was variable among dogs, with a median of34.9 mm. CT angiography identified the thrombus in the main portal vein of 12/13 dogs andmultiple thrombus formation other than the main portal vein in 9/13 dogs. CT angiographyprovided specific information such as detecting the presence, location, and number of PVTin dogs. Therefore, CT angiography might be useful for the diagnosis and follow-upevaluation of PVT in dogs.

Iodinated contrast medium (ICM) dose reduction is beneficial for decreasing potential health risk to renal-insufficiency patients in CT scanning. Due to the low-intensity vessel in ultra-low-dose-ICM CT angiography, it cannot provide clinical diagnosis of vascular diseases. Angiography reconstruction for ultra-low-dose-ICM CT can enhance vascular intensity for directly vascular diseases diagnosis. However, the angiography reconstruction is challenging since patient individual differences and vascular disease diversity. In this paper, we propose a Multiple Adversarial Learning based Angiography Reconstruction (i.e., MALAR) framework to enhance vascular intensity. Specifically, a bilateral learning mechanism is developed for mapping a relationship between source and target domains rather than the image-to-image mapping. Then, a dual correlation constraint is introduced to characterize both distribution uniformity from across-domain features and sample inconsistency within domain simultaneously. Finally, an adaptive fusion module by combining multi-scale information and long-range interactive dependency is explored to alleviate the interference of high-noise metal. Experiments are performed on CT sequences with different ICM doses. Quantitative results based on multiple metrics demonstrate the effectiveness of our MALAR on angiography reconstruction. Qualitative assessments by radiographers confirm the potential of our MALAR for the clinical diagnosis of vascular diseases.

Objective Original Rex shunt (mesenteric-to-left portal vein bypass) has been employed successfully for treating patients with extrahepatic portal vein obstruction.However, about 14% of children with extrahepatic portal vein obstruction suffered left portal vein agenesis and 4% to 28% patient had failed Rex shunt.Rex shunt became impossible for them.This study reports a novel approach of using portal-right portal vein bypass for treating extrahepatic portal vein obstruction after failed Rex shunt. Methods Four patients with failed Rex shunt underwent portal-right portal vein bypass.Their mean age was 6.1 (3.5-8.9) years.Primary Rex shunt was performed 1.1 to 2.5 years ago.Postoperatively, they developed recurrent gastrointestinal bleeding and hypersplenia not responding to conservative measures.After confirmation of blocked original shunt by dissection, cavernoma was bypassed by interposing a venous inferior mesenteric vein autograft between main portal vein in hepatoduodenal ligament and right portal vein. Results In 3/4 patients, right portal vein was well-developed with a diameter of 5 to 6 mm and another right portal vein became agenesic.Portal-right portal vein bypass was successfully conducted in 3 patients.Operative duration was 2.3(1.9-3.5) hours and bleeding volume was 50(30-80) ml without blood transfusion.After shunting, portal vein pressure decreased from 33 (26-45) to 18.7 (14-24) cmH2O.During a median follow-up period of 0.9 (0.5-1.5) years, there was no recurrence of gastrointestinal bleeding or hypersplenia after bypass.Postoperative Doppler and computed tomographic angiography confirmed shunt patency and satisfactory blood flow in shunts. Conclusions Direct bypass of portal cavemomata by right portal vein is efficacious for portal hypertension in children with failed Rex shunt.Patients with left portal vein agenesis or failed Rex shunt may benefit from this procedure.To our knowledge, this is the first report of treating extrahepatic portal vein obstruction via right portal vein bypass. Key words: Hypertension portal; Rex shunt

Branching variations of the left portal vein can be managed but they may require technical adaptation. The aim of the present study was to investigate the pattern of ramification of the left portal vein in vascular casts and in radiological images. 50 vascular casts and 200 computed tomography (CT) angiographies of the upper abdomen were analyzed. Analyses of the vascular casts and of the radiological images were conducted to evaluate the morphology of the left liver, the modality of division of the portal vein, and the number of branches destined for segments 2, 3, 4. In the vascular casts the portal vein presented bifurcation in 75%, trifurcation in 20%, and quadrifurcation in 5%, whereas in the radiological study the portal vein presented bifurcation in 90% and trifurcation in 10% of the cases. For segment 2 in the vascular casts, in their CT and in the radiologic in vivo study a number from 1 to 3 branches was found, coming from the medial or posterior aspects of the left portal vein. For segment 3 in the vascular casts, in their CT and in the radiologic in vivo study a number from 1 to 6 branches was found, coming from the posterior and medial aspects of the left portal vein and its the cul-de-sac. For segment 4 in the vascular casts, in their CT a number from 5 to 9 branches was found (in the radiologic in vivo study from 4 to 9), coming from the posterior and ventral aspects of the left portal vein and from its cul-de-sac. No branches were found to come from the lateral aspect of the left portal vein. Moreover, the modality of branching of the left portal vein correlated with the morphology of left liver. Knowledge of the pattern of branching of the left portal vein is important for surgical purpose. CT angiography is a valuable preoperative examination to visualize the branching pattern of adult patients.

Purpose: To measure patient skin dose from CT angiography (CTA) and CT exams of the head, and determine if patients having multiple exams could receive cumulative doses that approach or exceed deterministic thresholds. Methods: This study was HIPAA compliant and conducted with IRB approval. Patient skin doses were measured over a 4 month period using nanoDot OSL dosimeters placed on the head of 52 patients for two CT scanners. On each scanner, 26 patients received CT exams (scanner 1: 10 females, 16 males, mean age 64.2 years; scanner 2: 18 females, 8 males, mean age 61.2 years). CT exam dose metrics, CTDIvol and dose-length product (DLP) were recorded for each exam. Additionally, skin dose was measured on an acrylic skull phantom in each scanner and on a neuro-interventional imaging system using clinical protocols. Measured dose data was used to estimate peak skin dose (PSD) for 4 patients receiving multiple exams including CTA, head CT, and cerebral angiography. Results: For scanner 1, the mean PSD for CTA exams (98.9 ± 5.3 mGy) and for routine head CT exams (39.2 ± 3.7 mGy) agreed reasonably well with the PSD measured on the phantom, 105.4 mGy and 40.0 mGy, respectively. Similarly for scanner 2, the mean PSD for CTA exams (98.8 ± 7.4 mGy) and for routine head CT exams (42.9 ± 9.4 mGy) compared well with phantom measurements, 95.2 mGy and 37.6 mGy, respectively. In addition, the mean PSD was comparable between scanners for corresponding patient exams, CTA and routine head CT respectively. PSD estimates ranged from 1.9 – 4.5 Gy among 4 patients receiving multiple exams. Conclusion: Patients having several exams including both CTA and routine head CT may receive cumulative doses approaching or exceeding the threshold for single dose deterministic effects.

Preoperative delineation of any vascular anomalies offers planning for possible alteration of surgical procedures, especially in pediatric recipients undergoing living-related liver transplantation. We assess the efficacy of three-dimensional (3D) multislice computed tomography (CT) angiography in the hope of replacing conventional angiography as the pretransplant evaluation of the hepatic vascular system for potential recipients of liver transplantation. 3D CT angiography was performed in 38 children with biliary atresia. Conventional angiography was also performed in the first 15 patients. Twelve patients underwent living-related liver transplantation. The findings on 3D CT angiography were compared with conventional angiography and operative findings. 3D CT angiography was successfully performed in 37 pediatric patients. All findings of 3D CT angiography on hepatic artery, portal vein, and inferior vena cava paralleled those of catheter angiography and operative findings. Four patients were unsuitable to receive living grafts because of pathologic insults of the hepatic artery (one patient) and the portal vein (three patients). Three patients were advised to undergo a venous graft for portal anastomoses. Eight patients demonstrated portosystemic shunts that may require closure. 3D CT angiography proves to be a better tool in the demonstration of the vascular system and identification of pathologic insults in pediatric patients. It is superior to conventional angiography because it is less invasive, more convenient, and more efficient in providing thorough preoperative information that would have a major impact on patient selection and surgical planning.

The primary aim of this study was to evaluate whether the replacement of roughly one-decade-old computed tomography (CT) scanners with new-model CT scanners were associated with an additional reduction in the radiation dose delivered to oncological patients, in a radiological setting where the optimization of protocols had already reached very low radiation doses. An exploratory secondary objective was to evaluate the potential differences in the objective image quality between the CT scans obtained before and after the installation of the new-generation CT scanners. Chest and abdominal CT examinations conducted for oncologic purposes were retrospectively selected from two time periods-prior to scanner replacement (2022) and following an upgrade (2024)-after five CT systems in our radiology department were replaced. We extracted and compared the CT dose index (CTDI) and dose length product (DLP) for each CT phase. For the objective image quality evaluation, we calculated the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR) at the center of the liver and the aorta. An appropriate statistical analysis was performed and a p-value < 0.05 was considered significant. We included 14,601 CT acquisitions, of which 9013 (61.7%) were performed before and 5588 (38.3%) after the replacement of the CT scanners. There were significantly lower values for the CTDI and DLP with the new CT scanners compared to the old ones. The CTDI with the new CT scanners was significantly lower in all phases (p-value = 0.002 for unenhanced phase, and p < 0.001 for arterial, portal venous, and delayed phases). The DLP using the new CT scanners was significantly lower in the arterial, portal venous, and delayed phases (p < 0.001), and it was not significantly different in the unenhanced phase (p = 0.36). There was no significant difference in the SNR at the liver level (p = 0.72) or at the aorta level (p = 0.51). There was no significant difference in the CNR at the liver level (p = 0.24), whereas the CNR was higher with the new CT scanners at the aorta level (p = 0.03). The transition to new-model CT scanners resulted in a significant reduction in the radiation dose delivered by chest and abdomen CT scans, without compromising the objective image quality.

Objective To investigate the effect of split-bolus spectral computed tomography(CT) on the portal venography and radiation dose. Methods The prospective study was adopted. The clinical data of 119 patients who underwent spectral CT at China-Japan Union Hopital from September 2014 to March 2015 were collected. Patients were randomly divided into the portal venography with split-bolus spectral CT single-phase enhanced scan group and portal vein multi-phase scan group by random sequence method. In the portal venography with split-bolus spectral CT single-phase enhanced scan group, the spectral CT was used with the method of split-bolus single phase imaging, and in the portal vein multi-phase scan group, standard spiral CT was used to perform three-phase scan. Two observers evaluated CT portal venography subjectively and objectively, measured CT values, contrast to noise ratio (CNR), signal noise ratio (SNR), and calculated radiation dose. Observed indices included (1) choice of optimal monochromatic images. (2) CT values of portal veins, measurement of CNR and SNR. (3) Subjective scoring of portal venography quality. (4) Comparison of radiation dose. Measurement data with normal distribution were presented as±s, comparison between groups was analyzed by independent sample t test. Comparison of count data was analyzed by chi-square test. Results The 113 patients were screened for eligibility, including 59 in the portal venography with split-bolus spectral CT single-phase enhanced scan group and 54 in the portal vein multi-phase scan group. (1) Choice of optimal monochromatic images: optimal monochromatic images were abstracted at 60 keV from spectral CT portal venography. (2) CT values of portal veins and measurement of CNR and SNR: the CT values of intrahepatic portal vein, extrahepatic portal vein and branches of portal vein were (319±44)HU, (328±53)HU, (294±45)HU in the reconstructed images at the energy level of 60 keV in the portal venography with split-bolus spectral CT single-phase enhanced scan group and (213±41)HU, (228±49)HU, (210±41)HU in the portal vein multi-phase scan group, with significant differences between the 2 groups(t=8.04, 6.34, 6.82, P 0.05). The SNR of intrahepatic portal vein, extrahepatic portal vein and branches of portal vein were 31±6, 29±6, 27±6 in the portal venography with split-bolus spectral CT single-phase enhanced scan group and 29±7, 28±9, 26±6 in the portal vein multi-phase scan group, respectively, with no significant differences (t=-0.688, 0.615, 0.600, P>0.05). (3) Subjective scoring of portal venography quality: the subjective score of image quality of portal venography was 14.3±1.0 in the portal venography with split-bolus spectral CT single-phase enhanced scan group and 12.5±1.8 in the portal vein multi-phase scan group, with a significant difference (t=12.43, P<0.05). (4) Comparison of radiation dose: the radiation dose was (8.1±1.1)mSv of patients in the portal venography with split-bolus spectral CT single-phase enhanced scan group and (17.4±7.5)mSv in the portal vein multi-phase scan group, with a significant difference (t=24.14, P<0.05). Conclusion Spectral CT portal vein imaging combined with split-bolus protocol can achieve better manifestations of portal vein and its branches, and reduce radiation dose in the scanning process. Key words: Liver diseases; Portal vein; Spilt-bolus; Tomography, X-ray computed; Spectral imaging; Radiation dose

Renal artery stenosis is an important cause of hypertension in children, accounting for 5-10% of cases. When suspected, noninvasive imaging options include ultrasound (US), computed tomography (CT) angiography and magnetic resonance (MR) angiography. However, digital subtraction angiography (DSA) remains the gold standard. To investigate the accuracy and inter-reader reliability of CT angiography in children with suspected renal artery stenosis. This is a retrospective study of patients suspected of having renal artery stenosis evaluated by both CT angiography and DSA between 2008 and 2019 at a tertiary pediatric hospital. Only children who underwent CT angiography within 6months before DSA were included. CT angiography studies were individually reviewed by two pediatric radiologists, blinded to clinical data, other studies and each other's evaluation, to determine the presence of stenosis at the main renal artery and 2nd- and 3rd-order branches. The sensitivity, specificity and accuracy were calculated using DSA as the reference. The effective radiation dose for CT angiography and DSA was also calculated. Kappa statistics were used to assess inter-reader agreement. Seventy-four renal units were evaluated (18 girls, 19 boys). The patients' median age was 8years (range: 1-21years). Overall, CT angiography was effective in detecting renal artery stenosis with a sensitivity of 85.7%, specificity of 91.5% and accuracy of 88.9%. There was moderate inter-reader agreement at the main renal artery level (k=0.73) and almost perfect inter-reader agreement at the 2nd/3rd order (k=0.98). However, the sensitivity at the 2nd- and 3rd-order level was lower (14.3%). CT angiography provided excellent negative predictive value for evaluating renal artery stenosis at the main renal artery level (90.1%) and at the 2nd- or 3rd-order branches (82.7%). The median effective dose of CT angiography studies was 2.2mSv (range: 0.6-6.3) while the effective dose of DSA was 13.7mSv. CT angiography has high sensitivity and specificity at the main renal artery level with a lower radiation dose than previously assumed. Therefore, it can be used as a diagnostic tool in patients with low to medium risk of renal artery stenosis, and as a screening and treatment planning tool in patients at high risk.

BackgroundReducing radiation and contrast media (CM) doses in computed tomography angiography (CTA) is especially relevant for potentially vulnerable populations. Low tube voltage photon-counting detector CT (PCD-CT) offers an improved iodine contrast-to-noise ratio (CNR) as compared to conventional CT scanners. We investigated optimized radiation and CM doses of PCD-CT angiography at low tube voltage in an animal model.MethodsSix minipigs (median weight: 32.5 kg; IQR: 29.8–34.6 kg) underwent thoracoabdominal CTA using a clinical dual-source PCD-CT at 70 kVp with three scan protocols: (A) reference (100% CM and radiation dose), (B) increased radiation (233%) and reduced CM (56%) dose, and (C) reduced radiation (50%) and increased CM (141%) dose. CNR, subjective image quality, and radiation doses were assessed, with statistical analysis including Mann–Whitney U-test and Kruskal–Wallis tests.ResultsCTDIvol was 1.7 mGy (IQR: 1.5–1.8) for scan A, 4.3 mGy (IQR: 3.8–4.7) for scan B, and 0.9 mGy (IQR: 0.8–1.0) for scan C (p < 0.001). CM volumes were 16 mL (IQR: 15–17) for scan A, 10 mL (IQR: 8–10) for scan B, and 23 mL (IQR: 21–24) for scan C. No significant differences in CNR were found between scans, with medians of 26 (IQR: 24–28) for scan A, 23 (IQR: 22–26) for scan B, and 26 (IQR: 24–30) for scan C (p = 0.276). Subjective image quality was similar across scans (p = 0.342).ConclusionLow tube voltage PCD-CT angiography allows substantial reductions in radiation and CM dose while maintaining stable and improved CNR, which allows further dose flexibility for individualized CTA protocols.Relevance statementPCD-CT at low tube voltage provides a high CNR and great flexibility in dose optimization, making it particularly effective for applications where minimizing radiation and CM exposure is a priority.Key PointsLow tube voltage imaging with photon counting detector (PCD)-CT enables flexible contrast and radiation dose optimization strategies in thoracoabdominal CT angiography (CTA).The CNR for thoracoabdominal CTA remains stable with appropriate contrast and radiation dose adjustments at low tube voltage PCD-CT.Low tube voltage PCD-CT consistently yields diagnostic image quality in thoracoabdominal angiography even at reduced contrast or radiation doses.Graphical

Splenectomy is indicated after orthotopic liver transplantation (OLT) for various reasons, including left-sided portal hypertension, trauma, and hemorrhage prevention in patients with splenic artery aneurysms. Complications of splenectomy may include infections, bleeding, and portal vein thrombosis (PVT). The incidence of symptomatic postsplenectomy PVT ranges from 0.7% to 2%,1, 2 whereas the incidence of asymptomatic PVT can reach 7% to 10%.3 There is, however, limited literature pertaining to postsplenectomy PVT in recipients of OLT. The sequelae of PVT are particularly serious in OLT recipients. The reduction of the portal vein flow severely compromises allograft and patient survival.4, 5 In patients who have not undergone OLT, acute portal or mesenteric vein thrombosis is usually managed with anticoagulation alone, and this leads to recanalization in more than 90% of patients.6 Alternatively, thrombolysis or thrombectomy is performed, but this has not been widely reported and is not the standard of care.7 There are few studies addressing the management of postsplenectomy PVT in OLT recipients. Here we describe a case of acute postsplenectomy PVT in an OLT recipient who was successfully treated with both mechanical thrombolysis and directed and systemic anticoagulation. The patient was a 54-year-old male who suffered from end-stage liver disease secondary to complications from hepatitis C and alcohol abuse. He underwent OLT on March 5, 2007. The piggyback technique was used with a biliary duct-to-duct anastomosis. The operation and the postoperative course both went well without complications. Approximately 2 years later, he presented with increasing left upper quadrant pain. A computed tomography (CT) scan revealed an enlarged spleen with a calcified cyst that measured 17 cm. Therapeutic options were discussed with the patient, and splenectomy was planned. He received subcutaneous heparin perioperatively as deep venous thrombosis prophylaxis. The operation lasted 2 hours and was performed through an extension of the left subcostal incision from the initial OLT. An Endo GIA stapler was used to divide the hilum. Pathology revealed a 960-g spleen measuring 18.2 cm × 14.3 cm × 10.2 cm with capsular fibrosis indicating perisplenitis. Postoperative laboratory tests revealed a 5-fold rise in transaminase levels. An ultrasound examination of the liver was performed and revealed an absence of flow in the portal vein. Dual-phase CT of the liver showed complete thrombosis of the splenic and portal veins with extension into both right and left portal vein branches. The superior mesenteric vein was spared. An intravenous infusion of heparin was initiated. Complete thrombosis of the intrahepatic portal vein branches precluded percutaneous transhepatic cannulation of the portal system. The patient was taken immediately to the operating room in an attempt to salvage the hepatic allograft. A peripheral mesenteric venous branch was located and cannulated with a 5-Fr Fogarty catheter. An initial portogram confirmed the CT finding and revealed complete thrombosis of the main portal vein with some residual flow within the intrahepatic branches (Fig. 1A). Thrombectomy of the main portal vein was attempted via the catheter. With the assistance of interventional radiology, an infusion catheter was placed. Tissue plasminogen activator (t-PA) was injected through the catheter at a rate of 2.5 mg every 15 minutes. After the administration of a total of 16 mg of t-PA, only partial recanalization of the main portal vein was achieved (Fig. 1B). The catheter was withdrawn, the venotomy was ligated, and the abdomen was closed. The patient was extubated and then monitored in the intensive care unit. A postoperative ultrasound examination demonstrated no flow in the portal system. A follow-up CT scan revealed a filling defect in the portal vein and throughout the splenic vein. Interventional radiology was reconsulted, and the patient was taken to the angiography suite. This time, through a right internal jugular vein puncture, the right hepatic vein was cannulated, and the portal vein was accessed transhepatically. The portogram revealed thrombosis of the splenic vein stump, the main portal vein, and the intrahepatic portal veins extending beyond the bifurcation. The superior mesenteric vein was spared. A Trellis 8 pharmacomechanical thrombolysis device (Bacchus Vascular, Santa Clara, CA) was introduced into the portal vein. A total dose of 10 mg of t-PA was administered over 10 minutes, and mechanical thrombolysis was performed simultaneously from the portal confluence to the portal bifurcation. The device was then repositioned between the portal confluence and the inferior mesenteric vein, and another cycle of thrombolysis was undertaken with an additional 8 mg of t-PA. A subsequent portogram revealed significant improvement of the flow in the portal system, with residual thrombus in the splenic vein stump extending only along the medial wall of the main portal vein (Fig. 2A). A low-rate thrombolytic infusion of t-PA and heparin was administered overnight in an attempt to resolve the residual thrombus (0.5 mg/hour via an infusion catheter extending from the splenic vein stump to the main portal vein and 200 U/hour via a transjugular sheath in the main portal vein). The next day, the patient was taken back to the angiography suite, and a portogram revealed a patent portal vein with minimal residual nonocclusive thrombi in the main and right portal veins (Fig. 2B). A repeat ultrasound examination demonstrated recanalization of the portal venous system. Follow-up ultrasound examinations were performed 1 and 2 weeks after the procedure, and all revealed patent vessels. The transaminasemia returned to normal over a period of 5 days after splenectomy. The patient was maintained on a heparin infusion and was converted to warfarin for a total of 6 months after the procedure. The patient did well in the 3 years following this procedure with good allograft function, and portal vein patency was maintained, as demonstrated by follow-up imaging. This case demonstrates that mechanical and directed thrombolysis via a transjugular, transhepatic approach can be both safe and effective. It may represent another viable option when open thrombectomy is neither feasible nor effective. This is, however, only a single case. In order to determine the best therapeutic measures for this type of complication, multicenter experiences and studies are warranted. Lloyd Brown, M.D.1 Ahmad Abou Abbass, M.D.1 Shunji Nagai, M.D.1 Vrishali Patil, M.D.1 Marwan Abouljoud, M.D.1 Todd Getzen, M.D.2 Atsushi Yoshida, M.D.1 Marwan Kazimi, M.D.1 Dean Y. Kim, M.D.1 Divisions of 1Transplant and Hepatobiliary Surgery and 2Interventional Radiology Henry Ford Hospital Detroit, MI