High CT Attenuation Research Articles

High CT attenuation of clear cell renal cell carcinoma as a possible radiogenomic sign of GPX8 gene mutation

High CT attenuation of clear cell renal cell carcinoma as a possible radiogenomic sign of GPX8 gene mutation

Unenhanced computed tomography radiomics help detect endoleaks after endovascular repair of abdominal aortic aneurysm

ObjectivesTo explore the feasibility of unenhanced CT images for endoleak detection of abdominal aortic aneurysm (AAA) after endovascular repair (EVAR).MethodsPatients who visited our hospital after EVAR from July 2014 to September 2021 were retrospectively collected. Two radiologists evaluated the presence or absence of endoleaks using the combination of contrast-enhanced and unenhanced CT as the referenced standard. After segmenting the aneurysm sac of the unenhanced CT, the radiomic features were automatically extracted from the region of interest. Histogram features of patients with and without endoleak were statistically analyzed to explore the differences between the two groups. Twelve common machine learning (ML) models based on radiomic features were constructed to evaluate the performance of endoleak detection with unenhanced CT images.ResultsThe study included 216 patients (69 ± 8 years; 191 men) with AAA, including 64 patients with endoleaks. A total of 1955 radiomic features of unenhanced CT were extracted. Compared with patients without endoleak, the aneurysm sac outside the stent of patients with endoleak had higher CT attenuation (41.7 vs. 33.6, p < 0.001) with smaller dispersion (51.5 vs. 58.8, p < 0.001). The average area under the curve (AUC) of the ML models constructed with unenhanced CT radiomics was 0.86 ± 0.05, the accuracy was 81% ± 4, the sensitivity was 88% ± 10, and the specificity was 78% ± 5. When fixing the sensitivity to > 90% (92% ± 2), the models retained specificity at 72% ± 10.ConclusionsUnenhanced CT features exhibit significant differences between patients with and without endoleak and can help detect endoleaks in AAA after EVAR with high sensitivity.Clinical relevance statementUnenhanced CT radiomics can help provide an alternative method of endoleak detection in patients who have adverse reactions to contrast media. This study further exploits the value of unenhanced CT examinations in the clinical management and surveillance of postoperative abdominal aortic aneurysm.Key Points• Unenhanced CT features of the aneurysm sac outside the stent exhibit significant differences between patients with and without endoleak. The endoleak group showed higher unenhanced CT attenuation (41.7 vs 33.6, p < .001) with smaller dispersion (51.5 vs 58.8, p < .001) than the nonendoleak group.• Unenhanced CT radiomics can help detect endoleaks after intervention. The average area under the curve (AUC) of twelve common machine learning models constructed with unenhanced CT radiomics was 0.86 ± 0.05, the average accuracy was 81% ± 4.• When fixing the sensitivity to > 90% (92% ± 2), the machine learning models retained average specificity at 72% ± 10.

Deep learning reconstruction allows for usage of contrast agent of lower concentration for coronary CTA than filtered back projection and hybrid iterative reconstruction.

The demand for homogeneous and higher vascular contrast enhancement is critical to provide an appropriate interpretation of abnormal vascular findings in coronary computed tomography angiography (CTA). To evaluate the effect of various contrast media concentrations (Iohexol-370, Iohexol-300, Iohexol-240) and image reconstructions (filtered back projection [FBP], hybrid iterative reconstruction [IR], and deep learning reconstruction [DLR]) on coronary CTA. A total of 63 patients referred for coronary CTA between July and October 2021 were enrolled in this prospective study, and they randomly received one of three contrast media. CTA images were reconstructed with FBP, hybrid IR, and DLR. The CT attenuation, image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were calculated for all three images. The images were subjectively evaluated by two radiologists in terms of overall image quality, artifacts, image noise, and vessel wall delineation on a 5-point Likert scale. The application of DLR resulted in significantly lower image noise; higher CT attenuation, SNR, and CNR; and better subjective analysis among the three different concentrations of contrast media groups (P < 0.001). There was no significant difference in the CT attenuation of the left ventricle (P = 0.089) and coronary arteries (P = 0.072) between hybrid IR at Iohexol-300 and DLR at Iohexol-240. Furthermore, application of DLR to the Iohexol-240 significantly improved SNR and CNR; it achieved higher subjective scores compared with hybrid IR at Iohexol-300 (P < 0.001). We suggest that using DLR with Iohexol-240 contrast media is preferable to hybrid IR with Iohexol-300 contrast media in coronary CTA.

Dose Reduction of Dynamic Computed Tomography Myocardial Perfusion Imaging by Tube Voltage Change: Investigation in a Swine Model.

BackgroundIt is unclear whether tube voltage influences the measurement of perfusion parameters. The present study sought to evaluate the influence of tube voltage change on myocardial blood flow (MBF) measurements in dynamic computed tomography myocardial perfusion imaging (CTP).Methods and ResultsSeven swine [mean weight 55.8 kg ± 1.6 (standard deviation)] underwent rest and stress dynamic CTP with tube voltages of 100 and 70 kV. The image noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), radiation dose and MBF value were compared. The 70 kV images had higher CT attenuation and higher image noise (27.9 ± 2.4 vs. 21.5 ± 1.9, P < 0.001) than the 100 kV images, resulting in a higher SNR (20.5 ± 1.6 vs. 15.6 ± 1.8, P < 0.001) and CNR (17.6 ± 1.5 vs. 12.4 ± 1.7, P < 0.001). Compared to the use of conventional 100 kV, 70 kV yielded an approximately 64.6% radiation dose reduction while generating comparable MBF values, both at rest (88.3 ± 14.9 ml/100 g/min vs. 85.6 ± 17.4 ml/100 g/min, P = 0.21) and stress (101.4 ± 21.5 ml/100 g/min vs. 99.6 ± 21.4 ml/100 g/min, P = 0.58) states.ConclusionDynamic CTP using 70 kV instead of 100 kV does not substantially influence the MBF value but significantly reduces the radiation dose. Additional research is required to investigate the clinical significance of this change.

Predicting recurrence of non-small cell lung cancer based on mean computed tomography value

BackgroundThe aim of this study was to assess the ability of using mean computed tomography (mCT) values to predict non-small cell lung cancer (NSCLC) tumor recurrence.MethodsA retrospective study was conducted on 494 patients with stage IA NSCLC. Receiver operating characteristics analysis was used to assess the ability to use mCT value, C/T ratio, tumor size, and SUV to predict tumor recurrence. Multiple logistic regression analyses were performed to determine the independent variables for the prediction of tumor recurrence.ResultsThe m-CT values were − 213.7 ± 10.2 Hounsfield Units (HU) for the recurrence group and − 594.1 ± 11.6 HU for the non-recurrence group (p < 0.0001). Recurrence occurred in 45 patients (9.1%). The tumor recurrence group was strongly associated with a high CT attenuation value, high C/T ratio, large solid tumor size, and SUV. The diagnostic value of mCT value was more accurate than the C/T ratio, excluding the pure ground-glass opacity and pure solid (0 < C/T ratio < 100) groups. The SUV and mCT are independent predictive factors of tumor recurrence.ConclusionsThe evaluation of mCT values was useful for predicting recurrence after the limited resection of small-sized NSCLC, and may potentially contribute to the selection of suitable treatment strategies.

SUN-928 Adrenal Plasmacytoma in Multiple Myeloma Patient-An Unusual Presentation

Introduction:Extramedullary plasmacytomas are plasma cell tumors that arise outside of the bone marrow. They are solitary lesions, and are most often located in the head and neck region, mainly in the upper aerodigestive tract. However, involvement of adrenal gland is extremely rare, with only nine case reports published to date. A mass in the adrenal gland carries a broad differential, and identification is important, as diagnosis drives treatment options. CT imaging with attenuation, timing of contrast medium washout, size, and shape, with biopsy is necessary for diagnosis of a high Hounsfield unit mass. Ruling out pheochromocytoma before biopsy of the adrenal glands is crucial.Clinical Case:A 64-year-old female was diagnosed with multiple myeloma after presenting with back pain and altered mental status. Imaging revealed diffuse lytic lesions in clavicles, pelvis, calvarium, long bones, ribs, and compression fractures of T8, T10, and T12 vertebral bodies. A 1.5 cm left adrenal nodule was also noted. She was treated with bortezemib, cyclophosphamide, lenalidomide, and dexamethasone, and clinically improved. Four months after initial presentation, patient was to undergo chemotherapy with melphalan and autologous stem cell transplantation. Further imaging was performed, and CT Chest revealed an enlarging left adrenal mass measuring 3.0 x 3.2 cm with increased attenuation at 37 Hounsfield units and lobulated borders with no invasion of adjacent structures. The endocrinology team was consulted for evaluation of the adrenal mass, as patient’s disease from multiple myeloma was presumed to be in remission. Differential for the adrenal mass included pheochromocytoma, primary adrenal carcinoma, and metastatic disease from multiple myeloma vs other primary. Plasma fractionated metanephrines and DHEAS were within normal range. CT guided core biopsy was performed. Cytology revealed diffuse infiltrate of atypical plasma cells. IHC studies were positive for CD138, CD56, and showed lambda light chain restriction. Cyclin D1 stain was negative, consistent with plasmacytoma. Clinically, the patient started developing progressive disease, including cutaneous plasmacytomas, and she was treated with additional chemotherapy.Conclusion:Adrenal plasmacytoma is extremely rare, and in a patient with multiple myeloma, should be considered in the differential diagnosis of a rapidly enlarging adrenal mass with high CT attenuation. CT guided biopsy is the definitive test for diagnosis.

CT imaging and quantitative analysis in the differential diagnosis of hepatic epithelioid hemangioendothelioma and hepatic metastasis

Objective To study the use of abdominal enhanced CT imaging and quantitative index analysis in the differential diagnosis of hepatic epithelioid hemangioendothelioma (HEH) and hepatic metastasis. Methods A study group of 12 patients with HEH who underwent abdominal enhanced CT scanning at the First Affiliated Hospital of Zhengzhou University from February 2014 to October 2018 was retrospectively compared with a control group of 52 patients with hepatic metastases diagnosed clinically and by imaging examinations. The general information and imaging data of these patients were collected and analyzed. Results The lesions in the 2 groups mainly presented as multiple and diffuse lesions. The diffuse lesions of HEH often fused into strips. The hepatic metastasis group showed a higher CT attenuation and TNR in the portal vein phase than the HEH group (P<0.05). The area under the ROC curves of the two indexes were 0.756 and 0.841 respectively. The centers of the lesions showed almost no or slightly homogeneous enhancement in the HEH group, while the liver metastasis group showed slightly and moderately heterogeneous enhancement, with a significant difference between the two groups (P<0.05). Female, subcapsular distribution, capsular contraction, target ring sign and lollipop sign were independent risk factors for HEH (P<0.05), while a high CT attenuation and TNR in the portal vein phase, elevated tumor markers and lymph node metastasis were independent risk factors for liver metastasis on logistic regression analysis (P<0.05). Conclusions CT attenuation, TNR, central enhancement features in the portal vein phase, special signs and secondary changes of lesions were helpful for the differential diagnosis between HEH and liver metastasis. Key words: Hemangioendothelioma, epithelioid; Hepatoma; Tomography, X-ray computed; Tumor metastasis; Differential diagnosis

Preoperative predictive factors of pancreatic fistula after pancreaticoduodenectomy: usefulness of the CONUT score.

PurposePostoperative pancreatic fistula (POPF) is the most important factor affecting morbidity and mortality after pancreaticoduodenectomy (PD). Patients with a high controlling nutritional status (CONUT) score, which is used to assess nutritional status, are expected to have high morbidity rates. This study aimed to determine the usefulness of the CONUT score.MethodsData from 97 consecutive cases of PD performed in the Department of Surgery of Iwakuni Clinical Center, from April 2008 to May 2018, were included. Preoperative patient data, including sex, age, and hypertension, and postoperative complication data were collected to analyze pancreatic fistula occurrence.ResultsOf the 97 patients, 2 9 patients (29.8%) were diagnosed with POPF ≥ B, with 26 cases (26.8%) classified as grade B and 3 (3.1%) as grade C. The mortality rate was 2.1% (2 of 97). In the univariate analysis, a significant association was observed between POPF and the following factors: body mass index (BMI) ≥ 22 kg/m2, high CONUT score, nonpancreatic carcinoma, and CT attenuation values. In multivariate analysis, BMI ≥ 22 kg/m2 (odds ratio [OR], 6.16; P < 0.001), high CONUT score (OR, 3.77; P = 0.009), nonpancreatic carcinoma (OR, 5.72; P = 0.009), and CT attenuation values (late/early ratio) in the pancreas (OR, 9.07; P = 0.006) were independent risk factors for POPF.ConclusionPatients with a high CONUT score are at high risk of POPF. Further study correlating preoperative nutritional intervention with risk of POPF is necessary.

High CT attenuation values relative to the brainstem may predict squamous cell carcinoma arising from inverted papilloma

Background: A diagnostic indicator for differentiating squamous cell carcinomas (SCCs) from inverted papillomas (IPs) has not been established.Objectives: This study aimed to evaluate whether CT attenuation values relative to those of the brainstem (relative CT number) could be useful in differentiating IPs from SCCs.Material and Methods: Consecutive patients who were pathologically diagnosed with IP or SCC between 2007 and 2017 were retrospectively identified. Relative CT numbers were compared between the two patient groups. The factors with predictive power for differentiating IPs from SCCs were identified by univariate and multivariate logistic regression analyses.Results: Fifty-four sinonasal tumour cases were finally analysed (IP, 25 cases; SCC, 29 cases). Relative CT numbers were significantly higher in SCC than in IP (p < .001). The univariate logistic regression analysis showed BMI, relative CT number, and disease duration to have predictive value for differentiating IPs from SCCs. In the multivariate logistic regression analysis, only the relative CT number had predictive value for distinguishing IP from SCC (odds ratio, 1.97), with a relative CT number of ≥1.4 being significantly associated with SCC.Conclusions: High relative CT numbers could potentially be used to identify SCCs, and their measurement could provide a basis for differentiating IPs from SCCs.

Differentiation of duodenal gastrointestinal stromal tumors from hypervascular pancreatic neuroendocrine tumors in the pancreatic head using contrast-enhanced computed tomography.

To determine useful contrast-enhanced computed tomography (CE-CT) features in differentiating duodenal gastrointestinal stromal tumors (duodenal GISTs) from hypervascular pancreatic neuroendocrine tumors in the pancreatic head (pancreatic head NETs). Seventeen patients with pathologically confirmed duodenal GISTs and 25 with pancreatic NETs underwent preoperative CE-CT. CT image analysis included tumor size, morphology, and contrast enhancement. Receiver operating characteristic curves were performed, and cutoff values were calculated to determine CT findings with high sensitivity and specificity. CT imaging showed duodenal GISTs with higher frequencies of tumor central location close to the duodenum and a predominantly solid tumor type when compared with pancreatic head NETs (p < 0.05 for both). Duodenal GISTs were larger than pancreatic head NETs (3.3 ± 0.9cm vs. 2.5 ± 1.1cm, p = 0.03). Duodenal GISTs had significantly lower CT attenuation values (112.9 ± 17.9HU vs. 137.4 ± 32.1HU, p < 0.01) at the arterial phase and higher CT attenuation values at the delayed phase (94.3 ± 7.9HU vs. 84.9 ± 10.4HU, p < 0.01) when compared with pancreatic head NETs. A CT attenuation value of ≤ 135 HU at the arterial phase (30s) was 76% sensitive, 94.1% specific, and 83.3% accurate for the diagnosis of duodenal GISTs, while a CT attenuation value of ≥ 89.5 HU at the delayed phase (120s) was 93.3% sensitive, 81.8% specific, and 76.2% accurate for the diagnosis of duodenal GISTs. Tumor central location, size, texture, and contrast enhancement are valuable characteristics for the differentiation between duodenal GISTs and hypervascular pancreatic head NETs during preoperative examination.

Improved image quality of low-dose CT combining with iterative model reconstruction algorithm for response assessment in patients after treatment of malignant tumor.

To evaluate the image quality and radiation dose of low-dose (LD) computed tomography (LD-CT) combining with iterative model reconstruction (IMR) algorithm for response assessment in patients after treatment of malignant tumor compared with routine-dose CT (RD-CT). Forty-seven patients [mean age 57.8±10.9 years, 30 males, body mass index (BMI) 22.09±2.35 kg/m2] after treatment of malignant tumor underwent contrast-enhanced chest and abdomen CT twice for response assessment with an interval of 6 months according to clinical routine. The first CT scans were performed with RD protocol at 120 kVp and images were reconstructed with filtered back projection (FBP) algorithm; while the second scans were performed with LD protocol at 100 kVp and images were reconstructed with FBP and IMR algorithm respectively. All scans were performed using an automatic tube current modulation technique with 150 mAs as reference. Objective image quality including CT attenuation, image noise, and contrast to noise ratio (CNR), and subjective image quality including artifacts, noise, visualization of small structures and confidence of targeted lesions, as well as lesion detection were assessed and compared. Effective radiation dose of LD-CT scans was reduced 54.8% compared to RD-CT scans (26.89±3.35 vs. 12.14±2.09 mSv). Higher CT attenuation was found in both LD-IMR and LD-FBP images compared to RD-FBP images. Better subjective image quality and CNR as well as lower objective noise were found in LD-IMR images (all, P<0.05). Two small lesions with the diameter less than 1 cm were missed in LD-FBP images, which were able to be observed in LD-IMR images. IMR is able to help more than half of reduction of radiation dose without compromising the quality of diagnostic information in patients after treatment of malignant tumors to chest and abdomen CT for response assessment.

Mean Computed Tomography Value to Predict the Tumor Invasiveness in Clinical Stage IA Lung Cancer

The purpose of this study was to validate the ability of the mean computed tomography (m-CT) value to predict tumor invasiveness and recurrence, and further, to compare with other measurements such as consolidation/tumor ratio and solid tumor size. A retrospective study was conducted of 494 patients with clinical stage IA lung cancer who had peripherally located lung adenocarcinoma. Receiver operating characteristic curve analysis was used to compare the ability to predict tumor invasiveness and recurrence between m-CT value, consolidation/tumor ratio, and tumor size. Multiple logistic regression analyses were performed to determine the independent variables for the prediction of pathologic, less invasive lung cancer. Disease-free survival was measured from the date of the operation until any recurrence. The m-CT values were 643.6 ± 9.4 Hounsfield units in the noninvasive cancer group and 365.9 ± 11.4 Hounsfield units in the invasive cancer group (p < 0.0001). The invasive cancer group was strongly associated with a high CT attenuation value, high consolidation/tumor ratio, large solid tumor size, large tumor size, and high standardized uptake value. Multiple logistic analyses, including the preoperatively determined variables, revealed that standardized uptake value and m-CT are independent predictive factors of less invasive lung cancer. In addition, the hazard ratio of the m-CT value was higher than that of the standardized uptake value value. The evaluation of m-CT value is useful in predicting less invasive lung cancer. The m-CT value can potentially determine operative procedure, particularly limited resection for peripheral lung adenocarcinoma.

Fabrication of Au@Ag core–shell NPs as enhanced CT contrast agents with broad antibacterial properties

Au@Ag core–shell nanoparticles (NPs) integrating both antibacterial and X-ray attenuation capabilities were facilely synthesized in aqueous solution. These NPs modified with methoxy-PEG-SH (m-PEG) on the surface rendered them favorable dispersity and stability in water, resulting in enhancement of their blood circulation time. X-ray photoelectron spectroscope (XPS) and high-resolution transmission electron microscope (HRTEM) results confirmed the core–shell structure of m-PEG-Au@Ag NPs. The m-PEG-Au@Ag NPs showed low cytotoxicity and strong X-ray absorption potency in vitro. Further in vivo study showed that as-synthesized NPs offered a pronounced contrast and prolonged their circulation time in the blood stream with negligible toxic effect in vivo. Besides, m-PEG-Au@Ag NPs had significant bacteriostatic effect toward common bacteria like Escherichia coli and Staphylococcus aureus as demonstrated by broth dilution assay. Given their low-cytotoxicity and high CT attenuation efficacy, m-PEG-Au@Ag NPs had a promising potential for use as CT enhancing and antibacterial agents.

Adrenocortical tumours: high CT attenuation value correlates with eosinophilia but does not discriminate lipid-poor adenomas from malignancy

BackgroundCharacterisation of adrenal tumours is an important clinical problem. Unenhanced CT is the primary imaging modality to assess the nature of these lesions.AimsTo study the correlation between unenhanced CT attenuation...

Clinical utility of FDG-PET for diagnosis of adrenal mass: a large single-center experience

To examine the clinical utility of 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET) for diagnosing whether an adrenal mass is malignant, in contemporary clinical practice. Retrospective medical record review of patients from 2 databases at a large hospital. The first database consisted of patients who underwent FDG-PET between the years 2009 to 2011 while the second database included patients who had histological diagnosis of adrenal mass between the years 1997 to 2011. 3.4% of 2921 patients had adrenal FDG uptake. Approximately 43% of them did not exhibit corresponding adrenal mass. FDG-PET performance parameters were better if a cutoff of SUV (standardized uptake value) ≥3 was used to define positivity. The imaging characteristics of malignant adrenal masses and pheochromocytoma were similar but differed remarkably compared to those of benign tumors. Serial imaging revealed that the malignant adrenal masses consistently exhibited high CT attenuation, while more than half of them initially exhibited SUV<3 and in some cases FDG uptake indistinguishable from the background. The FDG-PET results were confirmatory in 87% of patients, contributory in 11%, but definitely misleading in 2%. FDG-PET is not required for adrenal mass diagnosis in most patients in contemporary practice but may help clinical decision making in specific situations.

Prediction of calcium level in melamine-related urinary calculi with helical CT: diagnostic performance evaluation and clinical significance

The aim of the study was to investigate the relationship between CT-attenuation and stone calcium level in melamine-related urinary calculi (MRUC). A total of 25 MRUC with known composition and calcium level were included (11 uric acid stones, 2 calcium oxalate stones and 12 mixture stones of uric acid and calcium oxalate). Of all, 18 renal stones accepted alkalization therapy except for 5 lower urinary tract stones and 2 stones of unknown position. With well-matched composition, 61 adult urinary stones were included as controls. Every stone was scanned by helical CT (80 kV/120 kV, 300 mA, pitch 0.625 mm) and the highest CT-attenuation value measured. CT-attenuation values of MRUC increased gradually from uric acid stones, mixture stones to calcium oxalate stones, but were always lower than the values of controls. Furthermore, a strong positive correlation was found between stone CT-attenuation value and stone calcium level (n = 25, r (80kV) = 0.883, p = 0.000; r (120kV) = 0.855, p = 0.000). Compared with alkalization-therapy-alone group, stone CT-attenuation values and stone calcium level in the comprehensive-therapy group were significantly greater (CT(80kV) 1,057 ± 639 vs. 172 ± 61 HU, p = 0.001; CT(120kV) 783 ± 476 vs. 162 ± 60 HU, p = 0.001; Ca 19.83 ± 7.48% vs. 1.30 ± 1.51%, p = 0.000). Fisher's exact test suggested that the stones with higher CT-attenuation values tended to resist alkalization when 400 HU served as the cutoff value (P (80kV) = 0.002, P (120kV) = 0.000). In conclusion, the study was the first to illustrate that the CT-attenuation value could reflect calcium level in MRUC and found that stones with higher CT-attenuation value were not amenable to alkalization because they probably contained greater calcium. For those patients, we believe that comprehensive therapy will be the best choice.

Functional mechanism of lung mosaic CT attenuation: Assessment with deep-inspiration breath-hold perfusion SPECT-CT fusion imaging and non-breath-hold technegas SPECT

The functional mechanism of lung mosaic computed tomography attenuation (MCA) in pulmonary vascular disease (PVD) and obstructive airway disease (OAD) has not yet been fully clarified. To clarify the mechanism of MCA in these diseases by assessing the relationship between regional lung function and CT attenuation change at MCA sites with the use of automated deep-inspiratory breath-hold (DIBrH) perfusion single-photon emission computed tomography (SPECT)-CT fusion images and non-breath-hold Technegas SPECT. Subjects were 42 PVD patients (31 pulmonary thromboembolism, four primary/two secondary pulmonary hypertension, and five Takayasu arteritis), 12 OAD patients (five acute asthma, four obliterative bronchiolitis, and three bronchiectasis), and 12 normal controls, all of whom had MCA on DIBrH CT. The relationship between regional lung function and CT attenuation change at the lung slices with MCA was assessed using DIBrH perfusion SPECT-CT fusion images and non-breath-hold Technegas SPECT. The severity of perfusion defects with or without MCA was quantified by regions-of-interest analysis. On DIBrH CT and perfusion SPECT, in contrast to no noticeable CT attenuation abnormality and fairly uniform perfusion in controls, 60 MCA and 274 perfusion defects in PVD patients, and 18 MCA and 61 defects in OAD patients were identified, with a total of 77 ventilation defects on Technegas SPECT in all patients. SPECT-CT correlation showed that, throughout the 78 MCA sites of all patients, lung perfusion was persistently decreased at low CT attenuation and preserved at intervening high CT attenuation, while lung ventilation was poorly correlated with CT attenuation change. The radioactivity ratios of reduced perfusion and the intervening preserved perfusion at the 78 perfusion defects with MCA were significantly lower than those at the remaining 257 defects without MCA (P<0.0001). Although further validation is required, our results indicate that heterogeneous pulmonary arterial perfusion may be a dominant mechanism of MCA in PVD and OAD.

Dyspnea on Exertion and Ground-Glass Infiltrates in an Ex-Smoker

Dyspnea on Exertion and Ground-Glass Infiltrates in an Ex-Smoker

Travel patterns and risk behaviour of HIV-positive people travelling internationally

International travel is associated with an increased risk of enteric, vector-borne, sexually transmitted and blood-borne infections. These risks are even higher among immunocompromised people, such as those with HIV infection. We conducted a study to determine HIV-positive people's travel patterns and risk behaviours while abroad. We conducted an anonymous survey of HIV-positive people attending an HIV clinic in a tertiary care hospital in Toronto about their travel activities and pretravel precautions as well as their burden of illness and risk exposure during travel. We compared the characteristics of respondents who had travelled outside Canada and the United States (international travellers) with those of respondents who had not travelled internationally. Of 290 HIV-positive people who participated in the study, 133 (45.9%) indicated that they had travelled internationally in the 5 years before the survey. These people were predominantly men (93.2%) and well educated (60.0% had a university level education), and they had travelled mostly for personal reasons (89.5%) on trips that lasted 3.6 weeks on average. Only 58 (43.6%) sought health advice before travelling, and only 17 (12.8%) sought advice from a travel clinic. Five (3.8%) had received live vaccines before travel, and 9 (6.8%) had taken malaria chemoprophylaxis. Of the 119 international travellers who were taking antiretroviral therapy; 35 (29.4%) reported either discontinuing their medications or being poorly compliant with the therapy while travelling. Thirty-one (23.3%) of the 133 international travellers reported having had casual sexual activity with new partners while travelling, and only 18 (58.1%) of them reported always using a condom. Twenty-one (15.8%) of the 133 reported having had risky exposure to sharps. Twenty-four (18.0%) said they had become ill enough while travelling to require medical attention. Only one-fifth of HIV-positive people surveyed who travelled internationally sought advice from a health professional before their trip. Their travel was associated with poor adherence to antiretroviral therapy, risky sexual practices and risky exposure to sharps.

FDG uptake in the morphologically normal thymus: comparison of FDG positron emission tomography andCT

The purpose of this study was to evaluate the correlation between fluorine-18 fluorodeoxyglucose (FDG) thymic uptake and a normal appearing thymus on CT. Non-attenuation corrected FDG positron emission tomography (PET) data from 94 young persons (mean age 25.4 years, range 18-29 years) with a normal thymus diagnosed on CT were retrospectively evaluated. No subject had clinical symptoms suggestive of thymus-related disease or mediastinal tumour (follow-up period 6-69 months). PET images were visually assessed and the count ratio between the thymus and the lung (T/L ratio) was calculated. Increased FDG uptake occurred in 32 (34%) subjects. In these 32 cases, the T/L ratio was 2.86+/-0.49 (range 2.02-3.99). In 86 subjects whose CT images were available to calculate the CT attenuation of the thymus (CAT), the CAT value was -17.5+/-45.7 HU (range -103.6 HU to 79.9 HU). The T/L ratio correlated with the CAT value (r=0.58). CAT values in subjects with positive PET findings were significantly higher than CAT values in subjects with negative PET findings (p<0.001, unpaired t-test). These results suggest that even in young adults, if the thymus has a relatively high CT attenuation value, the presence of physiological thymic uptake in FDG-PET is a normal variant. In this study, the diagnosis of normal thymus was based on CT appearance and clinical course. Further studies are needed to clarify the relationship between histopathology and FDG uptake in the thymus.