Pyogenic Liver Abscess Complicating Acute Cholecystitis: Different Management Options.

Acute cholecystitis, which is usually associated with gallstones is one of the most common surgical causes of emergency hospital admission and may be further complicated by mural necrosis, perforation and abscess formation. Perforation of the gallbladder is a relatively uncommon complication of acute cholecystitis (0.8-3.2% in recent reviews). The intrahepatic perforation causing a liver abscess is an extremely rare condition, anecdotally reported in the scientific literature, even in the rare types of subacute or acute perforation. Liver abscess caused by gallbladder perforation can be a life-threatening complication with a reported mortality of 5.6%. The treatment of synchronous pyogenic liver abscess and acute cholecystitis may be challenging. We reported three cases of liver abscess due to acute cholecystitis in which different therapeutical approaches were employed. The first case was treated with antibiotics and interval laparoscopic cholecystectomy; the second case was treated with emergency cholecystectomy; and the third case with percutaneous aspiration of the abscess only. The appropriate therapeutical method in these cases depends on the patient's clinical condition, the on-site expertise that is available in the hospital, and the experience of the surgeon.

CT liver perfusion in patients with hepatocellular carcinoma: can we modify acquisition protocol to reduce patient exposure?

OBJECTIVES: To investigate the potential of decreasing the number of scans and associated radiation exposure involved in CT liver perfusion (CTLP) dynamic studies for hepatocellular carcinoma (HCC) assessment. METHODS: Twenty-four CTLP image datasets of patients with HCC were retrospectively analyzed. All examinations were performed on a modern CT system using a standard acquisition protocol involving 35 scans with 1.7 s interval. A deconvolution-based or a standard algorithm was employed to compute ten perfusion parametric maps. 3D ROIs were positioned on 33 confirmed HCCs and non-malignant parenchyma. Analysis was repeated for two subsampled datasets generated from the original dataset by including only the (a) 18 odd-numbered scans with 3.4 s interval and (b) 18 first scans with 1.7 s interval. Standard and modified datasets were compared regarding the (a) accuracy of calculated perfusion parameters, (b) power of parametric maps to discriminate HCCs from liver parenchyma, and (c) associated radiation exposure. RESULTS: When the time interval between successive scans was doubled, perfusion parameters of HCCs were found unaffected (p > 0.05) and the discriminating efficiency of parametric maps was preserved (p < 0.05). In contrast, significant differences were found for all perfusion parameters of HCCs when acquisition duration was reduced to half (p < 0.05), while the discriminating efficiency of four parametric maps was significantly deteriorated (p < 0.05). Modified CTLP acquisition protocols were found to involve 48.5% less patient exposure. CONCLUSIONS: Doubling the interscan time interval may considerably reduce radiation exposure from CTLP studies performed for HCC evaluation without affecting the diagnostic efficiency of perfusion maps generated with either standard or deconvolution-based mathematical model. KEY POINTS: • CT liver perfusion for HCC diagnosis/assessment is not routinely used in clinical practice mainly due to the associated high radiation exposure. • Two alternative acquisition protocols involving 18 scans of the liver were compared with the standard 35-scan protocol. • Increasing the time interval between successive scans to 3.4 s was found to preserve the accuracy of computed perfusion parameters derived with a standard or a deconvolution-based model and to reduce radiation exposure by 48.5%.

Diagnosing a Patient with Erdheim-Chester Disease during the COVID-19 Pandemic.

Background: Erdheim-Chester disease (ECD) is a rare hematopoietic neoplasm of histiocytic origin characterized by an insidious course. The coronavirus disease 2019 (COVID-19) pandemic has put an enormous strain on healthcare systems worldwide both directly and indirectly, resulting in the disruption of healthcare services to prevent, diagnose and manage non-COVID-19 disease. Case Presentation: We describe the case of a 58-year-old male patient with sporadic episodes of self-resolving mild fever and anemia of chronic disease with onset two years before the current presentation. Positron emission/computed tomography scan revealed the presence of moderately hypermetabolic perirenal tissue masses. In order to achieve diagnosis, repeated perirenal tissue biopsies were performed, and the diagnostic evaluation was complicated by the strain put on the healthcare system by the COVID-19 pandemic. The patient contracted SARS-CoV-2 and required hospitalization, but recovered fully. No further ECD target organ involvement was documented. Treatment options were presented, but the patient chose to defer treatment for ECD. Conclusion: A high index of suspicion and multidisciplinary team collaboration is paramount to achieve diagnosis in rare conditions such as ECD. Disruptions in healthcare services in the pandemic milieu may disproportionately affect people with rare diseases and further study and effort is required to better meet their needs in the pandemic setting.

CT Foot Perfusion Examination for Evaluation of Percutaneous Transluminal Angioplasty Outcome in Patients with Critical Limb Ischemia: A Feasibility Study.

PURPOSE: To evaluate foot perfusion in patients with critical limb ischemia (CLI) using quantitative perfusion multi-detector-row CT and estimate perfusion parameter changes before and after percutaneous transluminal angioplasty (PTA). MATERIALS AND METHODS: This prospective study investigated 13 patients (10 men; median age, 72 y; range, 51-84 y) with CLI who underwent CT foot perfusion examinations with a 128-slice dual-energy CT scanner 1 day before and 1 week after PTA. Key parameters such as permeability surface (PS), blood volume (BV), and blood flow (BF) were analyzed and compared statistically. The studies were also examined by a second observer to determine interobserver reproducibility. RESULTS: Revascularization was technically successful in all patients, and mean ankle-brachial index increased from 0.36 ± 0.16 to 0.75 ± 0.22. After revascularization, mean BV increased from 1.55 mL/100 g ± 0.83 to 4.51 mL/100 g ± 1.53, BF increased from 16.28 mL/100 g/min ± 4.97 to 31.49 mL/100 g/min ± 6.86, and PS increased from 3.1 mL/min/100 g ± 1.95 to 8.67 mL/min/100 g ± 3.85 (P < .05). Patients with poor response to revascularization who finally underwent amputation presented lower post-PTA perfusion parameters values than patients with significant clinical improvement (P < .05). All measurements demonstrated very good interobserver reproducibility, and intraclass correlation coefficients were 0.91 for BV, 0.94 for BF, and 0.95 for PS. The mean effective dose of the examination was estimated at 0.29 mSv. CONCLUSIONS: CT foot perfusion is a reproducible technique that may be a useful modality for the estimation of PTA outcome. Significant restitution of perfusion parameters was observed after successful revascularization.

Perfusion-CT analysis for assessment of hepatocellular carcinoma lesions: diagnostic value of different perfusion maps.

BACKGROUND: Computed tomography liver perfusion (CTLP) has been improved in recent years, offering a variety of perfusion-parametric maps. A map that better discriminates hepatocellular carcinoma (HCC) is still to be found. PURPOSE: To compare different CTLP maps, regarding their ability to differentiate cirrhotic or non-cirrhotic parenchyma from malignant HCC. MATERIAL AND METHODS: Twenty-six patients (11 cirrhotic) with 50 diagnosed HCC lesions, underwent CTLP on a 128-row dual-energy CT system. Nine different maps were generated. Regions of interest (ROIs) were positioned on non-tumorous parenchyma and on HCCs found on previous magnetic resonance imaging. Perfusion parameters for non-cirrhotic and cirrhotic livers were compared. Receiver operating characteristic (ROC) analysis was employed to evaluate each map's ability to discriminate HCCs from non-tumorous livers. Comparison of ROC curves was performed to evaluate statistical significance of differences in the discriminating efficiency of derived perfusion maps. RESULTS: Perfusion parameters for non-tumorous liver and HCCs recorded in cirrhotic patients did not significantly differ from corresponding values recorded in non-cirrhotic patients ( P > 0.05). The highest power for HCC discrimination was found for the maximum-slope-of-increase (MSI) parametric map, with estimated the area under ROC curve of 0.997. An MSI cut-off criterion of 2.2 HU/s was found to provide 96% sensitivity and 100% specificity. Time to peak, blood flow, and transit time to peak were also found to have high discriminating power. CONCLUSION: Among available CTLP-derived perfusion parameters, MSI was found to provide the highest diagnostic accuracy in discriminating HCCs from non-tumorous parenchyma. Perfusion parameters for non-tumorous livers and HCCs were not found to significantly differ between cirrhotic and non-cirrhotic patients.

Common left carotid bifurcation at C7-Th1 level: a rare anatomical variant.

The left common carotid artery usually bifurcates to the internal and external carotids at or near the superior border of thyroid cartilage. In head and neck surgery, the common carotid arteries are important landmarks, defining the plane of dissection during radical neck surgeries. According to the literature, many variations exist regarding the carotid bifurcation. Anatomical knowledge of these variants is important for surgical approaches in the head and neck regions, to avoid devastating complications that may occur, mainly during anterior neck dissections. We report an interesting case of a 75-year-old male patient with low bifurcation of the left common carotid artery, accidentally found during a routine carotid Doppler ultrasonography. Bifurcation was located at the C7-Th1 intervertebral disc height, approximately 4 cm from the aortic arch.

The effect of iodine uptake on radiation dose absorbed by patient tissues in contrast enhanced CT imaging: Implications for CT dosimetry.

OBJECTIVES: To investigate the effect of iodine uptake on tissue/organ absorbed doses from CT exposure and its implications in CT dosimetry. METHODS: The contrast-induced CT number increase of several radiosensitive tissues was retrospectively determined in 120 CT examinations involving both non-enhanced and contrast-enhanced CT imaging. CT images of a phantom containing aqueous solutions of varying iodine concentration were obtained. Plots of the CT number increase against iodine concentration were produced. The clinically occurring iodine tissue uptake was quantified by attributing recorded CT number increase to a certain concentration of aqueous iodine solution. Clinically occurring iodine uptake was represented in mathematical anthropomorphic phantoms. Standard 120 kV CT exposures were simulated using Monte Carlo methods and resulting organ doses were derived for non-enhanced and iodine contrast-enhanced CT imaging. RESULTS: The mean iodine uptake range during contrast-enhanced CT imaging was found to be 0.02-0.46% w/w for the investigated tissues, while the maximum value recorded was 0.82% w/w. For the same CT exposure, iodinated tissues were found to receive higher radiation dose than non-iodinated tissues, with dose increase exceeding 100% for tissues with high iodine uptake. CONCLUSIONS: Administration of iodinated contrast medium considerably increases radiation dose to tissues from CT exposure. KEY-POINTS: • Radiation absorption ability of organs/tissues is considerably affected by iodine uptake • Iodinated organ/tissues may absorb up to 100 % higher radiation dose • Compared to non-enhanced, contrast-enhanced CT may deliver higher dose to patient tissues • CT dosimetry of contrast-enhanced CT imaging should encounter tissue iodine uptake.

Adult-type ALCAPA syndrome: A rare coronary artery anomaly.

Anomalous origin of the left coronary artery arising from the pulmonary artery (ALCAPA or Bland-White-Garland syndrome) is a rare but serious congenital coronary artery anomaly, with a poor prognosis without surgical repair. There are two types of ALCAPA syndrome: infant type and adult type. We present a rare case of a 63-year-old female patient, with isolated left anterior descending artery origin from the pulmonary artery. Coronary computed tomography angiography revealed giant and tortuous coronary arteries with many collaterals between the left and right coronary system. The patient refused any surgical treatment.

Treat, follow-up, or discharge? An aid in sonographic decisions for the borderline centered neonatal/infantile hips.

Aim: To investigate whether linear measurements or ratios on the Graf's "standard plane" ultrasound images of the neonatal/infantile hip, can support the clinically important differentiation between type I and type II hips. Material and methods: A total of 60 Graf type II hips and 124 randomly selected Graf type I hips, matched to the gestational age at delivery, birth weight, delivery mode, and age at the time of the examination, were identified through our hip screening service, during a period of two years. The images were diagnostically suitable, following anatomical identification and usability check, according to Graf. Anatomical landmarks including the lower limb of the os ilium, the bony rim, the silhouette of the os ilium, the labrum and the femoral head's borders, were used to determine the measurements and ratios which quantified their inter-relationships. Results: The indices which differed significantly between type I and type II hips included: (a) the width of the "bony roof" (cut-off value 5.91 mm, sensitivity: 75%, specificity: 70%), (b) the ratio of the width of the "bony roof" to the femoral head's width (cut-off value 0.40, sensitivity 83%, specificity 71%), and (c) the ratio of the cartilaginous acetabular roof's width (including the labrum), to the width of the femoral head (cut-off value 0.450, sensitivity 82%, specificity 67%). Conclusions: Newly introduced measurements and calculated ratios on "standard plane" ultrasound images can be used as additional indices in the differentiation between Graf's types of "centered hips", thus increasing the diagnostic certainty of the examiner in borderline cases and limiting unnecessary re-examinations or treatment.

Comparative Assessment of Endoscopic Ultrasound-Guided Biopsies vs. Percutaneous Biopsies of Pancreatic Lesions: A Systematic Review and Meta-Analysis of Diagnostic Performance.

Introduction: Pancreatic cancer ranks as the fourth deadliest form of cancer. However, it is essential to note that not all pancreatic masses signal primary malignancy. Therefore, it is imperative to establish the correct differential diagnosis, a process further supported by pre-operative biopsy procedures. This meta-analysis aims to compare the diagnostic performance of two minimally invasive biopsy approaches for pancreatic tissue sampling: percutaneous biopsies guided by computed tomography or ultrasound, and transduodenal biopsies guided by endoscopic ultrasound (EUS). Methods: A systematic literature search was conducted in the MEDLINE and Scopus databases. The included studies analyzed the diagnostic performance of the two biopsy methods, and they were assessed for risk of bias using the Quality Assessment of Diagnostic Accuracy Studies-2 tool. Statistical analysis was carried out using the RevMan and MetaDisc software packages. Results: The statistical analysis of the results demonstrated the superiority of the percutaneous approach. Specifically, the pooled sensitivity, specificity, LR+, LR-and DOR for the percutaneous approach were 0.896 [95% CI: 0.878-0.913], 0.949 [95% CI: 0.892-0.981], 9.70 [95% CI: 5.20-18.09], 0.20 [95% CI: 0.12-0.32] and 68.55 [95% CI: 32.63-143.98], respectively. The corresponding values for EUS-guided biopsies were 0.806 [95% CI: 0.775-0.834], 0.955 [95% CI: 0.926-0.974], 12.04 [95% CI: 2.67-54.17], 0.24 [95% CI: 0.15-0.39] and 52.56 [95% CI: 13.81-200.09], respectively. Nevertheless, it appears that this statistical superiority is also linked to the selection bias favoring larger and hence more readily accessible tumors during percutaneous biopsy procedures. Conclusions: Concisely, our meta-analysis indicates the statistical superiority of the percutaneous approach. However, selecting the optimal biopsy method is complex, influenced by factors like patient and tumor characteristics, clinical resources, and other relevant considerations.

Local and Regional Therapies for Hepatocellular Carcinoma and Future Combinations.

BACKGROUND: Hepatocellular carcinoma (HCC) can be treated by local and regional methods of percutaneous interventional radiological techniques. Indications depend on tumor size, type and stage, as well as patient's condition, liver function and co-morbidities. According to international classification systems such as Barcelona Clinic Liver Cancer (BCLC) classification, very early, early or intermediate staged tumors can be treated either with ablative methods or with transarterial chemoembolization (TACE), depending on tumor characteristics. The combination of both allows for individualized forms of treatment with the ultimate goal of improving response and survival. In recent years, a lot of research has been carried out in combining locoregional approaches with immune therapy. Although recent developments in systemic treatment, especially immunotherapy, seem quite promising and have expanded possible combined treatment options, there is still not enough evidence in their favor. The aim of this review is to provide a comprehensive up-to-date overview of all these techniques, explaining indications, contraindications, technical problems, outcomes, results and complications. Moreover, combinations of percutaneous treatment with each other or with immunotherapy and future options will be discussed. Use of all those methods as down-staging or bridging solutions until surgery or transplantation are taken into consideration will also be reviewed. CONCLUSION: Local and regional therapies remain a mainstay of curative and palliative treatment of patients with HCC. Currently, evidence on potential combination of the local and regional treatment options with each other as well as with other treatment modalities is growing and has the potential to further individualize HCC therapy. To identify the most suitable treatment option out of these new various options, a repeated interdisciplinary discussion of each case by the tumor board is of utmost importance.

Haemoptysis in Pulmonary Arterial Hypertension Associated with Congenital Heart Disease: Insights on Pathophysiology, Diagnosis and Management.

Haemoptysis represents one of the most severe major bleeding manifestations in the clinical course of pulmonary arterial hypertension (PAH) associated with congenital heart disease (CHD). Accumulating evidence indicates that dysfunction of the pulmonary vascular bed in the setting of PAH predisposes patients to increased hemorrhagic diathesis, resulting in mild to massive and life-threatening episodes of haemoptysis. Despite major advances in PAH targeted treatment strategies, haemoptysis is still correlated with substantial morbidity and impaired quality of life, requiring a multidisciplinary approach by adult CHD experts in tertiary centres. Technological innovations in the field of diagnostic and interventional radiology enabled the application of bronchial artery embolization (BAE), a valuable tool to efficiently control haemoptysis in modern clinical practice. However, bleeding recurrences are still prevalent, implying that the optimum management of haemoptysis and its implications remain obscure. Moreover, regarding the use of oral anticoagulation in patients with haemoptysis, current guidelines do not provide a clear therapeutic strategy due to the lack of evidence. This review aims to discuss the main pathophysiological mechanisms of haemoptysis in PAH-CHD, present the clinical spectrum and the available diagnostic tools, summarize current therapeutic challenges, and propose directions for future research in this group of patients.

Current Imaging Diagnosis of Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer related death worldwide. Radiology has traditionally played a central role in HCC management, ranging from screening of high-risk patients to non-invasive diagnosis, as well as the evaluation of treatment response and post-treatment follow-up. From liver ultrasonography with or without contrast to dynamic multiple phased CT and dynamic MRI with diffusion protocols, great progress has been achieved in the last decade. Throughout the last few years, pathological, biological, genetic, and immune-chemical analyses have revealed several tumoral subtypes with diverse biological behavior, highlighting the need for the re-evaluation of established radiological methods. Considering these changes, novel methods that provide functional and quantitative parameters in addition to morphological information are increasingly incorporated into modern diagnostic protocols for HCC. In this way, differential diagnosis became even more challenging throughout the last few years. Use of liver specific contrast agents, as well as CT/MRI perfusion techniques, seem to not only allow earlier detection and more accurate characterization of HCC lesions, but also make it possible to predict response to treatment and survival. Nevertheless, several limitations and technical considerations still exist. This review will describe and discuss all these imaging modalities and their advances in the imaging of HCC lesions in cirrhotic and non-cirrhotic livers. Sensitivity and specificity rates, method limitations, and technical considerations will be discussed.

Institutional Diagnostic Reference Levels and Peak Skin Doses in selected diagnostic and therapeutic interventional radiology procedures.

PURPOSE: Institutional (local) Diagnostic Reference Levels for Cerebral Angiography (CA), Percutaneous Transhepatic Cholangiography (PTC), Transarterial Chemoembolization (TACE) and Percutaneous Transhepatic Biliary Drainage (PTBD) are reported in this study. MATERIALS AND METHODS: Data for air kerma-area product (PKA), air kerma at the patient entrance reference point (Ka,r), fluoroscopy time (FT) and number of images (NI) as well as estimates of Peak Skin Dose (PSD) were collected for 142 patients. Therapeutic procedure complexity was also evaluated, in an attempt to incorporate it into the DRL analysis. RESULTS: Local PKA DRL values were 70, 34, 189 and 54 Gy.cm2 for CA, PTC, TACE and PTBD respectively. The corresponding DRL values for Ka,r were 494, 194, 1186 and 400 mGy, for FT they were 9.2, 14.2, 27.5 and 22.9 min, for the NI they were 844, 32, 602 and 13 and for PSD they were 254, 256, 1598 and 540 mGy respectively. PKA for medium complexity PTBD procedures was 2.5 times higher than for simple procedures. For TACE, the corresponding ratio was 1.6. PSD was estimated to be roughly 50% of recorded Ka,r for procedures in the head/neck region and 10% higher than recorded Ka,r for procedures in the body region. In only 5 cases the 2 Gy dose alarm threshold for skin deterministic effects was exceeded. CONCLUSION: Procedure complexity can differentiate DRLs in Interventional Radiology procedures. PSD could be deduced with reasonable accuracy from values of Ka,r that are reported in every angiography system.

CT coronary angiography in asymptomatic male patients with high atherosclerosis risk: Is it justified?

PURPOSE: To study the necessity of coronary artery screening with computerized tomography coronary angiography (CTCA) in asymptomatic male patients. MATERIAL AND METHODS: A total of 226 asymptomatic male patients aged over 50 years were included in this prospective study, according to a clinical protocol approved by the Heraklion University Hospital's Ethics Committee. All participants had at least 3 or more known atherosclerosis risk factors. All patients had none or normal noninvasive cardiological tests in the past and had no contraindications for CTCA. All patients gave their informed consent after being notified regarding contrast medium and radiation dose risks. RESULTS: Significant stenoses were found in 52 asymptomatic males (23%). Out of them, 38 male patients underwent invasive coronography and 14 patients were lost in follow-up. In 18 patients, no lesions were found (47.4%). In the other 20 (52.6%) patients, 28 lesions were found. Stent placement was performed in 11 patients, bypass surgery was proposed in 3 patients, and in another 6 patients conservative treatment was suggested. Patients with findings in CTCA were more likely to have a family history of coronary artery disease, compared to patients with normal CTCA (P < 0.05 by using Fischer's Exact Test). Sensitivity of CTCA for significant stenosis was 74.3% with a specificity of 62%. CONCLUSION: CTCA may be used to screen for clinically significant coronary artery disease (CAD) in asymptomatic male patients, particularly those with positive family history or potentially high-risk patients with >3 risk factors for CAD.

CIRSE Standards of Practice on Percutaneous Transhepatic Cholangiography, Biliary Drainage and Stenting.

This CIRSE Standards of Practice document is aimed at interventional radiologists and provides best practices for performing percutaneous transhepatic cholangiography, biliary drainage and stenting. It has been developed by an expert writing group established by the CIRSE Standards of Practice Committee.

Cerebral CT Perfusion in Acute Stroke: The Effect of Lowering the Tube Load and Sampling Rate on the Reproducibility of Parametric Maps.

The aim of this study was to define lower dose parameters (tube load and temporal sampling) for CT perfusion that still preserve the diagnostic efficiency of the derived parametric maps. Ninety stroke CT examinations from four clinical sites with 1 s temporal sampling and a range of tube loads (mAs) (100-180) were studied. Realistic CT noise was retrospectively added to simulate a CT perfusion protocol, with a maximum reduction of 40% tube load (mAs) combined with increased sampling intervals (up to 3 s). Perfusion maps from the original and simulated protocols were compared by: (a) similarity using a voxel-wise Pearson's correlation coefficient r with in-house software; (b) volumetric analysis of the infarcted and hypoperfused volumes using commercial software. Pearson's r values varied for the different perfusion metrics from 0.1 to 0.85. The mean slope of increase and cerebral blood volume present the highest r values, remaining consistently above 0.7 for all protocol versions with 2 s sampling interval. Reduction of the sampling rate from 2 s to 1 s had only modest impacts on a TMAX volume of 0.4 mL (IQR -1-3) (p = 0.04) and core volume of -1.1 mL (IQR -4-0) (p < 0.001), indicating dose savings of 50%, with no practical loss of diagnostic accuracy. The lowest possible dose protocol was 2 s temporal sampling and a tube load of 100 mAs.

Curative embolization of iatrogenic inferior mesenteric arteriovenous fistula 14 years after right hemicolectomy.

Inferior mesenteric arteriovenous fistula (IMAVF) is a rare condition with 40 reported cases. It can be of congenital, idiopathic or acquired etiology. Acquired IMAVF occurs after trauma or has an iatrogenic origin due to abdominal interventions, mainly operations involving the left hemi-colon. A new case of iatrogenic IMAVF is described, which became symptomatic 13 years after right hemicolectomy and was diagnosed radiologically one year later. This case was treated successfully by means of endovascular arterial embolization. To our knowledge, this is only the second reported case of acquired IMAVF following right hemicolectomy.

Effect of scan projection radiography coverage on tube current modulation in pediatric and adult chest CT.

PURPOSE: To investigate the effect of scan projection radiography (SPR) coverage on tube current modulation in pediatric and adult thoracic CT examinations. METHODS: Sixty pediatric and 60 adult chest CT examinations were retrospectively studied to determine the incidence rate of examinations involving SPRs that did not include the entire image volume (IV) or the entire primarily exposed body volume (PEBV). The routine chest CT acquisition procedure on a modern 64-slice CT system was imitated on five anthropomorphic phantoms of different size. SPRs of varying length were successively acquired. The same IV was prescribed each time and the computed tube current modulation plan was recorded. The SPR boundaries were altered symmetrically by several steps of ±10mm with respect to the IV boundaries. RESULTS: The upper IV boundary was found to be excluded from SPR in 52% of pediatric and 40% adult chest CT examinations. The corresponding values for the lower boundary were 15% and 20%, respectively. The computed tube current modulation was found to be considerably affected when the SPR did not encompass the entire IV. SPR deficit of 3cm was found to induce up to 46% increase in the computed tube current value to be applied during the first tube rotations over lung apex. CONCLUSIONS: The tube current modulation mechanism functions properly only if the IV set by the operator is entirely included in the localizing SPR image. Operators should cautiously set the SPR boundaries to avoid partial exclusion of prescribed IV from SPRs and thus achieve optimum tube current modulation.

Comparison of patient dose from routine multi-phase and dynamic liver perfusion CT studies taking into account the effect of iodinated contrast administration.

OBJECTIVES: To accurately determine and compare patient radiation burden from routine multi-phase CT (MPCT) and dynamic CT liver perfusion (CTLP) studies taking into account the effect of iodine uptake of exposed tissues/organs. MATERIALS AND METHODS: 40 consecutive MPCT of upper abdomen and 40 consecutive CTLP studies performed on a modern CT scanner were retrospectively studied. Iodine uptake of radiosensitive tissues at the time of acquisition was calculated through the difference of tissues' CT numbers between NECT and CECT images. Monte Carlo simulation and mathematical anthropomorphic phantoms were employed to derive patient-size-specific organ dose data from each scan involved taking into account the effect of iodinated contrast uptake on absorbed dose. Effective dose estimates were derived for routine multiphase CT and CTLP by summing up the contribution of NECT and CECT scans involved. RESULTS: The mean underestimation error in organ doses from CECT exposures if iodine uptake is not encountered was found to be 2.2%-38.9%. The effective dose to an average-size patient from routine 3-phase CT, 4-phase CT and CTLP studies was found to be 20.6, 27.7 and 25.8 mSv, respectively. Effective dose from CTLP was found lower than 4-phase CT of upper abdomen irrespective of patient body size. Compared to 3-phase CT, the radiation burden from CTLP was found to be higher for average size-patients but again lower for overweight patients. CONCLUSIONS: Modern CT technology allows CTLP studies at comparable or even lower patient radiation burden compared to routine multi-phase liver CT imaging.