Occult contrast retention post-thrombectomy on 24-h follow-up dual-energy CT: Associations and impact on imaging analysis.

BACKGROUND: Following reperfusion treatment in ischemic stroke, computed tomography (CT) imaging at 24 h is widely used to assess radiological outcomes. Even without visible hyperattenuation, occult angiographic contrast may persist in the brain and confound Hounsfield unit-based imaging metrics, such as net water uptake (NWU). AIMS: We aimed to assess the presence and factors associated with retained contrast post-thrombectomy on 24-h imaging using dual-energy CT (DECT), and its impact on the accuracy of NWU as a measure of cerebral edema. METHODS: Consecutive patients with anterior circulation large vessel occlusion who had post-thrombectomy DECT performed 24-h post-treatment from two thrombectomy stroke centers were retrospectively studied. NWU was calculated by interside comparison of HUs of the infarct lesion and its mirror homolog. Retained contrast was quantified by the difference in NWU values with and without adjustment for iodine. Patients with visible hyperdensities from hemorrhagic transformation or visible contrast retention and bilateral infarcts were excluded. Cerebral edema was measured by relative hemispheric volume (rHV) and midline shift (MLS). RESULTS: Of 125 patients analyzed (median age 71 (IQR = 61-80), baseline National Institutes of Health Stroke Scale (NIHSS) 16 (IQR = 9.75-21)), reperfusion (defined as extended-Thrombolysis-In-Cerebral-Infarction 2b-3) was achieved in 113 patients (90.4%). Iodine-subtracted NWU was significantly higher than unadjusted NWU (17.1% vs 10.8%, p < 0.001). In multivariable median regression analysis, increased age (p = 0.024), number of passes (p = 0.006), final infarct volume (p = 0.023), and study site (p = 0.021) were independently associated with amount of retained contrast. Iodine-subtracted NWU correlated with rHV (rho = 0.154, p = 0.043) and MLS (rho = 0.165, p = 0.033) but unadjusted NWU did not (rHV rho = -0.035, p = 0.35; MLS rho = 0.035, p = 0.347). CONCLUSIONS: Angiographic iodine contrast is retained in brain parenchyma 24-h post-thrombectomy, even without visually obvious hyperdensities on CT, and significantly affects NWU measurements. Adjustment for retained iodine using DECT is required for accurate NWU measurements post-thrombectomy. Future quantitative studies analyzing CT after thrombectomy should consider occult contrast retention.

Giant haemorrhagic hepatic cyst with flame-like morphology in a patient with polycystic kidney and liver disease.

INTRODUCTION: Intracystic haemorrhage is a rare complication of hepatic cysts, and is often mistaken for a malignant lesion. CASE REPORT: A 55-year-old female with a history of polycystic kidney and liver disease presented with a six-month history of abdominal distension, abdominal pain, early satiety, shortness of breath and 5 kg of weight loss. Imaging revealed a 20 cm mixed solid-cystic hepatic lesion containing peripheral avascular mobile echogenic material with a flame-like morphology. After experiencing symptomatic relief from ultrasound-guided aspiration, the patient underwent cyst fenestration for more definitive treatment. DISCUSSION: Haemorrhagic hepatic cysts are uncommon and may present on imaging as having lace-like retractile clot, internal layering or shading of separating blood products or avascular mobile flame-like excrescences. The presence of avascular mobile flame-like excrescences appears to be a unique feature of haemorrhagic hepatic cysts. CONCLUSION: While haemorrhagic hepatic cysts are rare and commonly mistaken for biliary cystadenomas or adenocarcinomas, the identification of particular features on high-resolution magnetic resonance imaging and contrast-enhanced ultrasound can lead to the correct diagnosis.

Identification of the lateral femoral safe zone for drilling during LISS plate fixation of distal femur fractures.

BACKGROUND: The incidence of arterial injury associated with femoral fractures is approximately 1%. Lateral sub-muscular plate fixation is gaining popularity for the management of distal femoral fractures. The objective of this study was to assess the iatrogenic risk to the superficial femoral artery (SFA) during Less Invasive Stabilisation System (LISS) plate fixation of distal femoral fractures by analysing the range of distances and angles between LISS plate screws and the drilling line to the SFA. MATERIALS AND METHODS: We identified all patients who underwent LISS plate fixation of distal femoral fractures between 2008 and 2018 in our level-1 trauma centre. Patients who underwent postoperative computed tomography for any reason were eligible for inclusion in the study. Twenty-five patients met the inclusion criteria. The sample comprised 10 male and 15 female patients with a mean age of 55 years. The most common fracture type was a supracondylar femur fracture (56%), followed by an intercondylar fracture (36%). A 13-hole LISS plate was the most common plate length used (44%). A consultant radiologist reviewed all scans to verify the visibility and marking of the SFA. RESULTS: The median distance between the screw tip and the SFA was 21 mm (range, 8-65 mm). There was a negative correlation between the LISS plate hole number and the trajectory of drilling (Pearson coefficient: -0.87, p < 0.001). Using a linear regression model, the SFA was more likely to be in the line of drilling when the 6th to 10th holes in the LISS plate were used. CONCLUSION: Extra care is needed when drilling into the LISS plate holes from the lateral to the medial direction in order to reduce the risk of iatrogenic injury to the SFA, especially in the high-risk plate zone where the artery can be close to the drilling line.

Dynamic CT for Parathyroid Adenoma Detection: How Does Radiation Dose Compare With Nuclear Medicine?

OBJECTIVE: Dynamic CT is increasingly used for preoperative localization of parathyroid adenomas, but concerns remain about the radiation effective dose of CT compared with that of 99mTc-sestamibi scintigraphy. The purpose of this study was to compare the radiation dose delivered by three-phase dynamic CT with that delivered by 99mTc-sestamibi SPECT/CT performed in accordance with our current protocols and to assess the possible reduction in effective dose achieved by decreasing the scan length (i.e., z-axis) of two phases of the dynamic CT protocol. MATERIALS AND METHODS: The effective dose of a 99mTc-sestamibi nuclear medicine parathyroid study performed with and without coregistration CT was calculated and compared with the effective dose of our current three-phase dynamic CT protocol as well as a proposed protocol involving CT with reduced scan length. RESULTS: The median effective dose for a 99mTc-sestamibi nuclear medicine study was 5.6 mSv. This increased to 12.4 mSv with the addition of coregistration CT, which is higher than the median effective dose of 9.3 mSv associated with the dynamic CT protocol. Reducing the scan length of two phases in the dynamic CT protocol could reduce the median effective dose to 6.1 mSv, which would be similar to that of the dose from the 99mTc-sestamibi study alone. CONCLUSION: Dynamic CT used for the detection of parathyroid adenoma can deliver a lower radiation dose than 99mTc-sestamibi SPECT/CT. It may be possible to reduce the dose further by decreasing the scan length of two of the phases, although whether this has an impact on accuracy of the localization needs further investigation.

Four-Dimensional Computed Tomography: Clinical Impact for Patients with Primary Hyperparathyroidism.

BACKGROUND: In recent years, four-dimensional computed tomography (4DCT) has emerged as a new localization study for primary hyperparathyroidism (pHPT). OBJECTIVE: We aimed to assess the added value of 4DCT in our institution in the first 4 years of use. METHODS: A retrospective cohort study was conducted from February 2004 to June 2015. Since 2011, patients over 50 years of age without concordant sestamibi-SPECT (SeS) and ultrasound (US) findings underwent 4DCT. Imaging results, surgical findings, histopathology, and postoperative biochemistry were collected. RESULTS: A total of 536 parathyroid operations in 510 patients were performed during the study period. The overall cure rate was 99.2% after reoperation in some patients, and the overall sensitivity for SeS was 76.0%, and 74.8% for US. Since 2011, 100 patients without concordant SeS/US findings have undergone 4DCT, with a sensitivity of 72.9%. This is in comparison to the sensitivities for SeS (48.3%) and US (52.3%). 4DCT was more sensitive in patients with persistent/recurrent disease (60.0% compared with SeS 43.8% and US 36.4%) and patients with multigland disease (67.4% compared with SeS 40.9% and US 42.1%). Comparison between outcomes in the pre- versus post-CT era demonstrated no difference in the initial cure rate (95.4 vs. 95.9%, p = 0.85) or the rate of minimally invasive parathyroidectomies (74.5 vs. 79.9%, p = 0.22). CONCLUSION: Parathyroid 4DCT can aid surgical planning in cases without concordant SeS/US findings; however, the introduction of 4DCT as a second-line test did not change our overall cure rate or rate of minimally invasive parathyroidectomy. The role of 4DCT as the primary localization study for pHPT merits further investigation.

Infiltrating caecal carcinoma versus appendicitis with caecal phlegmon-can computer tomography differentiate them?

Right iliac fossa pain is a common acute general surgery presentation, and computer tomography (CT) is often used as an aid in determining the diagnosis. CT can play an important role in differentiating malignant and inflammatory causes of caecal wall thickening if certain key features are identified. Two patients with similar presentations of right iliac fossa pain had pre-operative CT, which showed inflammation and caecal thickening, the first was focal with homogenous enhancement, and the second eccentric with stratification. At operation, these were proven to be malignant and inflammatory caecal thickening. Although the clinical presentation of appendicitis and caecal carcinoma may be similar, and the correct recognition and interpretation of differentiating CT characteristics enables the patient for an appropriately tailored operation.

CT brain perfusion: A static phantom study of contrast-to-noise ratio and radiation dose.

INTRODUCTION: Computed tomography perfusion (CTP) is increasingly employed in the diagnosis and management of ischaemic stroke but radiation dose can be significant and optimising contrast-to-noise ratio (CNR) is challenging. This study aimed to quantify and optimise the balance between CNR as a surrogate for image quality and radiation dose. METHODS: A perspex head phantom with vials of dilute contrast agent was scanned using a Siemens Definition Flash 128-slice scanner. The CTP protocol exposure parameters were adjusted over 70-120 kVp and 150-285 mAs. Measurements were obtained for the average dose per slice, Hounsfield Units (HU) for iodinated contrast agent, and the image noise for background regions of perspex. The CNR was measured as a function of the volumetric CT dose index (CTDIvol) and kVp. RESULTS: A change from 120 to 80 kVp, achieved the same CNR with 60% reduction in dose. Alternatively, for the same dose, the change from 120 to 80 kVp improved CNR by +58%. A change from 80 to 70 kVp while operating at the same CNR, led to 13% reduction in dose. Alternatively, maintaining the same dose while changing from 80 to 70 kVp improved the CNR by +7%. CONCLUSION: Lower beam energies achieved the same CNR with less dose, or improved CNR at the same dose. A reduction from 80 kVp to 70 kVp may be clinically useful to optimise CTP acquisitions.

Justifying the use of abdominal wall computed tomographic angiography in deep inferior epigastric artery perforator flap planning.

Abdominal wall computed tomography angiography (CTA) is used to guide preoperative planning and intraoperative technique for deep inferior epigastric artery perforator free flap breast reconstructive surgery. This study considers the amount of radiation delivered to the patient, outlining how scan parameters can be optimized to minimize the radiation exposure whilst maintaining image quality. Results of scan parameters and dose reports for 34 patients undergoing abdominal wall CTA are compared with those patients undergoing routine abdominal computed tomography. The links between computed tomography dose quantities are explained, including their conversion to effective dose (in mSv) and risk as the probability for inducing deterministic effects (eg, skin burns) and stochastic effects (ie, cancer induction). The mean effective dose by using our technique for routine abdominal computed tomography is 9.9 and for abdominal wall CTA is 6.0 mSv. All doses are far below the thresholds for deterministic effects to the skin. Abdominal wall CTA can be justified before major reconstructive surgery if the surgeon believes that the very low estimated risk of fatal radiation-induced cancer (1 in 4270 for 6 mSv) is outweighed by the benefits.

Diagnostic challenges and pitfalls in MR imaging with hepatocyte-specific contrast agents.

The use of gadolinium-based hepatocyte-specific contrast agents (HSCAs) has increased markedly since their introduction, and hepatocellular phase imaging performed with an HSCA is now a key part of the standard magnetic resonance (MR) imaging work-up for focal liver lesions. An understanding of the mechanisms of action of HSCAs helps ensure their effective use. The optimal delay for hepatocellular phase image acquisition differs between the two currently available HSCAs, gadoxetic acid and gadobenate dimeglumine, and MR imaging protocols must be adjusted accordingly. In addition, familiarity with typical and atypical appearances of benign and malignant focal liver lesions at HSCA-enhanced hepatocellular phase MR imaging, along with knowledge of the processes that are most likely to produce atypical appearances, is required to achieve optimal diagnostic accuracy.

Assessing signal intensity change on well-registered images: comparing subtraction, color-encoded subtraction, and parallel display formats.

PURPOSE: To assess the sensitivity, specificity, accuracy, and interobserver reliability of subtraction, color-encoded subtraction, and parallel display formats in assessing signal intensity (SI) differences between well-registered images. MATERIALS AND METHODS: Institutional ethics approval for the study and a waiver of individual patient consent were obtained. Five radiologists graded the severity of fatty liver by using a seven-point scale for four imaging sets created from 179 pairs of dual-echo in- and opposed-phase magnetic resonance images from 179 patients. The four sets contained images displayed in parallel, subtraction images, color-encoded subtraction images, and images from the three previous formats presented together. The order of the images and sets was randomized. Sensitivity and specificity were assessed with the McNemar test. Accuracy was assessed by using three-way analysis of variance, with Tukey post hoc methods used to assess differences between the four formats. Interobserver reliability was assessed by using the Fleiss κ value. RESULTS: Subtraction (P = .016 at a 5% SI difference threshold) and color-encoded subtraction (P = .031 at a 4% SI difference threshold) formats had higher sensitivity than did the parallel format. The accuracy of the subtraction format was superior to that of the parallel format (P < .0001). Interobserver reliability of the subtraction (κ = 0.53) and color-encoded subtraction (κ = 0.39) formats was superior to that of the parallel format (κ = 0.33) (P < .0001 and P = .0085, respectively). CONCLUSION: When images are well registered, subtraction and color-encoded subtraction techniques offer advantages over the traditional parallel presentation format for the assessment of SI differences.

Magnetic resonance colonography for colorectal cancer screening in patients with Lynch syndrome gene mutation.

Lynch syndrome gene carriers have a 50-80% risk of colorectal cancer (CRC). Current guidelines recommend yearly colonoscopy, with associated procedure-related risks. Magnetic resonance colonography (MRC) was evaluated as a non-invasive alternative for CRC screening in this high-risk population. Adult Lynch syndrome gene carriers underwent both screening procedures on the same day. MRI radiologists read the scans and rated image quality. Endoscopists performed colonoscopy unaware of MRC findings until after procedure completion. If lesions were detected, their number, size and location were noted. Post-procedure, patients compared discomfort and inconvenience of MRC and colonoscopy on a visual analogue scale. Thirty patients were recruited. 83% of the MRC scans were of adequate to good quality. MRC detected three lesions in three patients (70, 36, 17 mm). All 3 were independently detected on colonoscopy, excised and found to be CRC. MRC failed to detect a 3 mm CRC found on colonoscopy. CRC prevalence was 13%. Colonoscopy detected a further 30 polyps, all <10 mm. Of these, 17 were hyperplastic polyps and 10 normal mucosa. Colonoscopy had a false positive rate of 32% as defined by histology. MRC failed to detect any polyp <10 mm. Mean patient discomfort scores were 20% for MRC and 68% for colonoscopy, P = 0.003. Mean patient inconvenience scores were 54% for MRC and 52% for colonoscopy, P = 0.931. MRC was reliable in detecting large polyps, potentially CRC. However MRC currently has poor sensitivity in detecting small polyps, limiting its utility in adenoma screening at this time. MRC was associated with less discomfort than CC.

Torrential upper gastrointestinal bleeding from 'downhill' oesophageal varices complicating long term central venous access for total parenteral nutrition.

Oesophageal varices usually develop in the setting of portal hypertension secondary to chronic liver disease. However, superior vena cava (SVC) obstruction can result in 'downhill' varices forming in the upper oesophagus. A case of torrential upper gastrointestinal bleeding from SVC obstruction due to chronic central venous access for home total parenteral nutrition is described. It is suggested that in patients presenting with gastrointestinal bleeding in the setting of SVC obstruction, 'downhill' varices should be suspected. The current literature is discussed regarding management of such varices. It is recommended that endoscopic variceal surveillance be carried out in patients with known SVC obstruction.

Evaluating anatomical research in surgery: a prospective comparison of cadaveric and living anatomical studies of the abdominal wall.

BACKGROUND: Cadaveric research has widely influenced our understanding of clinical anatomy. However, while many soft-tissue structures remain quiescent after death, other tissues, such as viscera, undergo structural and functional changes that may influence their use in predicting living anatomy. In particular, our understanding of vascular anatomy has been based upon cadaveric studies, in which vascular tone and flow do not match the living situation. METHODS: An angiographic analysis of the abdominal wall vasculature was performed using plain film and computed tomography angiography in 60 cadaveric hemi-abdominal walls (from 31 cadavers) and 140 living hemi-abdominal walls (in 70 patients). The deep inferior epigastric artery (DIEA) and all of its perforating branches larger than 0.5 mm were analysed for number, calibre and location. RESULTS: Both large, named vessels and small calibre vessels show marked differences between living anatomy and cadaveric specimens. The DIEA was of larger diameter (4.2 mm versus 3.1 mm, P < 0.01) and had more detectable branches in the cadaveric specimens. Perforators were of greater calibre (diameter 1.5 mm versus 0.8 mm, P < 0.01) and were more plentiful (16 versus 6, P < 0.01) in cadaveric specimens. However, the location of individual vessels was similar. CONCLUSIONS: Cadaveric anatomy displays marked differences to in vivo anatomy, with the absence of living vascular dynamics affecting vessel diameters in cadaveric specimens. Blood vessels are of greater measurable calibre in cadaveric specimens than in the living. Consequently, cadaveric anatomy should be interpreted with consideration of post-mortem changes, while living anatomical studies, particularly with the use of imaging technologies, should be embraced in anatomical research.

Hepatic vein morphology: a new sonographic diagnostic parameter in the investigation of cirrhosis?

OBJECTIVE: The purpose of this study was to evaluate the accuracy of a new sonographic marker for the diagnosis of cirrhosis using hepatic vein wall changes. METHODS: A prospective pilot study evaluating 88 patients, 38 with cirrhosis and 50 with no evidence of liver disease, was undertaken. Hard copy sonograms of the hepatic veins were obtained and reviewed in a blinded fashion by 2 radiologists. The hepatic vein morphology was assessed by 3 parameters: hepatic vein wall straightness, uniformity of hepatic vein wall echogenicity, and visualization of a complete 1-cm hepatic vein segment. The 3 parameters were compared to evaluate sensitivity and specificity for the diagnosis of cirrhosis. Interobserver and intraobserver errors for each parameter were also calculated with kappa statistics to assess reproducibility. RESULTS: There was a strong correlation between altered straightness and nonuniformity of hepatic vein wall echogenicity and cirrhosis. The straightness parameter had superior sensitivity of 97% (95% confidence interval [CI], 85%-100%) and specificity of 91% (95% CI, 78%-97%) for diagnosis of cirrhosis. Uniformity of hepatic vein wall echogenicity was the next most useful parameter, with sensitivity of 88% (95% CI, 73%-97%) and specificity of 86% (95% CI, 72%-95%). The continuous 1-cm segment of the hepatic vein had sensitivity of 68% (95% CI, 49%-83%) and specificity of 91% (95% CI, 78%-97%). Hepatic vein evaluation was found to show both good intraobserver and interobserver error. CONCLUSIONS: Hepatic vein morphology on sonography, in particular, changes in the straightness and uniformity of hepatic vein wall echogenicity, is a new sign of cirrhosis, which may increase the overall accuracy of sonographic diagnosis of cirrhosis and which appears to have a moderately high degree of reproducibility.

A three-dimensional analysis of the lymphatics of a bilateral breast specimen: a human cadaveric study.

BACKGROUND: There is an increasing clinical need for evaluation of the lymphatic anatomy of the breast. Because of tissue putrefaction, previous studies have not been able to achieve radiographic analyses of bilateral breasts in cadaver specimens. The use of improved preservation techniques with computed tomographic lymphangiography (CT; CTL) has now allowed this analysis to be undertaken. MATERIALS AND METHODS: The bilateral breasts and anterior upper torso from a female unembalmed human cadaver was studied over an 8-week period. Using microsurgical techniques, lymphatic vessels were identified with hydrogen peroxide, injected with lead oxide mixture, and radiographed to demonstrate lymphatic vessels in both breasts. Multiple frozen domestic ice bricks were used to cover the contralateral side of tissues to keep them partially frozen during this lengthy process. The specimen was radiographed, CT scanned, cross-sectioned, and radiographed again, with images digitalized for analysis. RESULTS: A three-dimensional analysis of lymph collecting vessels in the breasts, anterior upper torso and the internal mammary vascular bundles was achieved using both plain radiography and CTL. The lymphatics of the breast and anterior upper torso drain radially into the axillary lymph nodes. A predominance of superficial lymphatics are noted. Importantly, lymphatic vessel patterns of the breast are asymmetric between breasts of each side. CONCLUSION: Three-dimensional images of the lymphatic drainage of the breasts using advanced imaging technologies are described, with lymphangiography achieved in bilateral cadaveric breasts and anterior upper torso for the first time. This has significant future application for clinical practice.

The in vivo anatomy of the deep circumflex iliac artery perforators: defining the role for the DCIA perforator flap.

The deep circumflex iliac artery (DCIA) provides a dependable option for use as an osteo-musculo-cutaneous flap, particularly in mandibular reconstruction. Modifications to flaps based on DCIA perforators have been sought to prevent donor site morbidity as a consequence of muscle cuff harvest. Previous studies have been inconsistent in their descriptions of perforator anatomy, and means of assessing these preoperatively have not been widely described. A clinical anatomical study was undertaken, with a cohort of 44 hemiabdominal walls in 22 consecutive patients undergoing preoperative computed tomographic angiography (CTA) before free flap surgery. The feasibility of CTA and the regional vascular anatomy were both assessed. The use of CTA was shown to demonstrate DCIA perforators with high resolution and to be able to assess vessel size and location. In 44 hemiabdominal walls, there were 44 perforators of >0.8 mm diameter. There were no suitable perforators in 40% of sides, with 32% of sides having one perforator >0.8 mm diameter, 16% having two perforators, <10% had three perforators, and only one side had over four perforators. Perforators emerged from the deep fascia on an average of 5.1 cm cranial and 3.9 cm posterior to the anterior superior iliac spine (ASIS). Of the 44 perforators identified, 82% of perforators were located within a 4 cm by 4 cm area, 3 cm superior, and 2 cm posterior to the ASIS. The current study has demonstrated the utility of preoperative CTA for identifying DCIA perforators, and for selecting patients who may be suitable for a DCIA perforator flap given the variable perforator anatomy.

Current state of the art in perforator flap imaging with computed tomographic angiography.

Computed tomographic angiography (CTA) has become increasingly adopted for preoperative imaging in perforator flap surgery, as it has been shown to improve operative outcomes and decrease operating times prior to deep inferior epigastric artery perforator (DIEP) flap and anterolateral thigh perforator flap surgery. Current technologies are readily available for the preoperative imaging of all perforator flaps, however only sporadic reports of the use of CTA for the imaging of other perforators have been described. We describe our experience with 325 CTAs performed for the preoperative imaging of perforators prior to 370 perforator flaps throughout several body regions. The scanning techniques, software reconstructions and technical issues are explored. In all cases, CTA was scored by the radiologist as at least "sufficient", and described as "optimal" in the majority of cases. Similarly, the surgeon described the correlation of imaging to operative findings as at least "good", and described the correlation as "optimal" in the majority of cases. As such, a standardized protocol for the use of CTA prior to perforator flap surgery is provided, which has been shown to be successful prior to a range of perforator flap operations.