An innovative modification of the retrograde approach to angioplasty and recanalization of the superficial femoral artery

Endovascular therapy has been performed for chronic limb ischemia for nearly 50 years. Superficial femoral artery occlusions can be managed by the retrograde contralateral (“crossover”), antegrade ipsilateral, or retrograde popliteal (“facedown”) approaches. The retrograde approach was initially fraught with limitations and served as a backup option. Refinements to this technique have made it an enticing option and possibly the first choice in selected patients. We herein describe an innovative modification of this method.Endovascular therapy has been performed for chronic limb ischemia since 1964, with intraluminal and subintimal angioplasty of the superficial femoral artery (SFA) gaining popularity in the last decade (1). SFA occlusions can be managed by retrograde contralateral or antegrade ipsilateral approaches (2, 3); when these approaches fail, some practitioners resort to using a re-entry device (4, 5). The retrograde popliteal approach was initially fraught with limitations and served as a backup option (1, 4, 6). However, refinements to this technique have made this an enticing option (2–7), and it has been advocated as a first-line treatment in select patients (3). We herein describe another modification of this method.     

Development,growth, propagation,and angiographic utilization of the rabbit VX2 model of liver cancer: a pictorial primer and “how to” guide

The VX2 tumor is a leporine anaplastic squamous cell carcinoma characterized by rapid growth, hypervascularity, and facile propagation in the skeletal muscle. Since its introduction over 70 years ago, it has been used to model a variety of malignancies, and is commonly employed by interventional radiologists in preclinical investigations of hepatocellular carcinoma. However, despite the widespread and lasting popularity of the model, there are few technical resources detailing its use. Herein, we present a comprehensive pictorial outline of the technical methodology for development, growth, propagation, and angiographic utilization of the rabbit VX2 liver tumor model.The rabbit VX2 tumor model has played a longstanding role in experimental oncology. Developed in 1930–1940 by Rous et al. (1, 2), the VX2 tumor is a virus-induced anaplastic squamous cell carcinoma characterized by hypervascularity, rapid growth, and easy propagation in the skeletal muscle (3, 4). Since its introduction, the tumor has been used to model cancers of the head and neck (5), kidney (6), brain (7), lung (8), urinary bladder (9), uterus (10), liver (11, 12), bone (13), and pancreas (14). The high growth rate and the relatively large size of rabbit vasculature render the model particularly well suited for use by interventional radiologists, and in recent years the model has been employed in numerous studies pertaining to the imaging and locoregional treatment of hepatocellular carcinoma (15–19). However, despite the widespread and lasting popularity of the model, there are few, if any, comprehensive technical resources detailing its use, leaving many key procedural details to be conveyed anecdotally. Lack of a technical guide may also represent a barrier to entry of interventional radiologists into translational research. With that in mind, this review is intended to provide a complete pictorial overview of the development, growth, propagation, and angiographic utilization of the rabbit VX2 tumor model based on the experience of a single operator in order to serve as a reference for novice and experienced investigators alike.     

CT-guided percutaneous cryoablation of central lung tumors

PURPOSE

Cryoablation has been successfully used to treat lung tumors. However, the safety and effectiveness of treating tumors adjacent to critical structures has not been fully established. We describe our experience with computed tomography (CT)-guided percutaneous cryoablation of central lung tumors and the role of ice ball monitoring.

MATERIALS AND METHODS

Eight patients with 11 malignant central lung tumors (nine metastatic, two primary; mean, 2.6 cm; range, 1.0–4.5 cm) located adjacent to mediastinal or hilar structures were treated using CT-guided cryoablation in 10 procedures. Technical success and effectiveness rates were calculated, complications were tabulated and intraprocedural imaging features of ice balls were described.

RESULTS

All procedures were technically successful; imaging after 24 hours demonstrated no residual tumor. Five tumors recurred, three of which were re-ablated successfully. A hypodense ice ball with well-defined margin was visible during the first (n=6, 55%) or second (n=11, 100%) freeze, encompassing the entire tumor in all patients, and abutting (n=7) or minimally involving (n=4) adjacent mediastinal and hilar structures. Pneumothorax developed following six procedures (60%); percutaneous treatment was applied in three of them. All patients developed pleural effusions, with one patient requiring percutaneous drainage. Transient hemoptysis occurred after six procedures (60%), but all cases improved within a week. No injury occurred to mediastinal or hilar structures.

CONCLUSION

CT-guided percutaneous cryoablation can be used to treat central lung tumors successfully. Although complications were common, they were self-limited, treatable, and not related to tumor location. Ice ball monitoring helped maximize the amount of tumor treated, while avoiding critical mediastinal and hilar structures.Malignant lung tumors represent a major cause of morbidity and mortality in developed nations (1). While surgical resection remains the treatment of choice for the local control of both non-small cell lung cancer and metastases to the lung, percutaneous image-guided ablative therapies, particularly heat-based ablation techniques such as radiofrequency (RF) ablation, have emerged as safe and effective alternatives in patients who are not surgical candidates (2–7). However, treatment of lung tumors using RF ablation presents technical challenges, including high electrical resistance of alveolar air, poor thermal conductivity of aerated lung, and the heat-sink effect of blood and air flow in well-perfused and aerated lung tissue (8, 9). In addition, RF ablation has a limited role in the treatment of tumors that are close to mediastinal and hilar structures (2–9). Since intraprocedural visualization of ablation zone margins is not possible during heat-based ablation procedures, treatment of central tumors could harm mediastinal and hilar structures, including the tracheobronchial tree. As a result, tumors close to central structures are generally not amenable to treatment using percutaneous heat-based ablation techniques (2–10). Also, RF ablation may interfere with conduction system of the heart and function of the pacemakers (11).A growing body of literature describes the successful use of cryoablation in the treatment of malignancies in the liver, kidneys, and soft tissues (12–14). The ability to deploy multiple, individually-controlled cryoablation applicators facilitates the creation of ablation zones of desired shapes and sizes that can be tailored to the morphology of the tumor being ablated (15, 16). Cryoablation is also monitorable; ice balls can be visualized by computed tomography (CT) as a distinct ovoid area of low attenuation during the procedure. As a result, the treatment can be optimized while minimizing the risk of harming nearby critical structures (12–16). Also, cryoablation may be less painful than RF ablation (17). Finally, it has been suggested that cryoablation may be better suited for the treatment of thoracic tumors adjacent to the mediastinum because it spares the architecture of collagen-containing structures relative to RF ablation and enables preservation of the integrity of the tracheobroncheal tree (18). Heat-based ablation methods may not be safe in the treatment of central lung tumors because of a possibility of bronchial disruption or perforation, which may result in bronchopleural fistula formation (19). Although cryoablation has been used to treat lung malignancies (19–31), there are limited data on the safety and effectiveness of percutaneous cryoablation of central lung tumors. In this study, we describe our experience with CT-guided percutaneous cryoablation of central lung tumors and the role of ice ball monitoring.     

Diffusion-weighted MRI findings of treated and untreated retroperitoneal fibrosis

PURPOSE

We aimed to evaluate diffusion-weighted imaging (DWI) findings in patients with treated and untreated retroperitoneal fibrosis (RPF).

METHODS

We analyzed magnetic resonance imaging examinations of 44 RPF patients (36 male, 8 female), of which 15 were untreated and 29 were under therapy. Qualitative DWI and T1 postcontrast signal intensities and the largest perivascular extent of RPF were compared between treated and untreated groups and correlated to erythrocyte sedimentation rate and C-reactive protein values. Quantitative DWI signal intensities and apparent-diffusion-coefficients were calculated in regions-of-interest, together with a relative index between signal intensities of RPF and psoas muscle in 15 untreated patients and 14 patients under treatment with remaining perivascular fibrosis of more than 5 mm.

RESULTS

The extent of RPF in untreated patients was significantly larger compared with the extent of RPF in treated patients (P < 0.0001). DWI signal intensities were significantly higher in untreated patients than in patients under therapy (mean, 27 s/mm² vs. 20 s/mm²; P = 0.009). The calculated DWI-index was significantly higher in untreated patients than in patients under therapy (P = 0.003).

CONCLUSION

Our data show significant differences in the DWI findings (b800 signal intensities and relative DWI-index) of patients with treated and untreated RPF. DWI is a promising technique in the assessment of disease activity and the selection of patients suitable for medical therapy.Retroperitoneal fibrosis (RPF) is a rare disease affecting the retroperitoneal space (1–3). It presents as retroperitoneal proliferation of fibrous tissue surrounding the retroperitoneal vascular structures and abutting the medial aspect of the ureters. Clinical findings of RPF are non-specific; the most common symptom is chronic back pain. Further symptoms include lower extremity edema, deep vein thrombosis, oliguria, and urinary tract infection (3). Computed tomography (CT) and magnetic resonance imaging (MRI) are the preferred imaging modalities for the diagnosis of RPF (3). Retroperitoneal fibrosis shows contrast enhancement of gadolinium containing contrast media in MRI (4). Medical treatment is classically based on steroids like prednisone (3). Recent studies suggested tamoxifen as another safe and effective treatment alternative (5).The assessment of disease activity is relevant for planning of further medical or surgical therapy (6, 7). Nowadays the disease activity is assessable by positron emission tomography tracer uptake (3), with a relatively low resolution and the need of ionized radiation. As an alternative, dynamic contrast-enhanced MRI was suggested for the evaluation of disease activity (7, 8). However, gadolinium may be contraindicated in patients with impaired renal function due to the potential development of nephrogenic systemic fibrosis (NSF) (9). This is especially relevant in RPF patients with postrenal failure due to ureteral compression. For those cases a supplemental method for the determination of disease activity would be helpful.Diffusion-weighted imaging (DWI) is a radiation-free unenhanced MRI modality that has been applied for the detection of bowel inflammation in patients with chronic inflammatory bowel diseases (10, 11), as well as for oncological retroperitoneal and abdominal applications (12–14). Therefore, we aimed to evaluate the application and findings of DWI in patients with treated and untreated RPF disease.     

Clinical,pathological, and imaging characteristics of primitive neuroectodermal tumors of the spine

Primitive neuroectodermal tumors (PNETs) located in the spine are extremely rare, and information concerning these tumors in the medical literature is limited to single case reports. This pictorial essay presents the clinical, pathological, and imaging characteristics of PNET of the spine.Primitive neuroectodermal tumors (PNETs) are malignant tumors thought to arise from the neural ectoderm and comprise undifferentiated small round cells (1–3). PNETs located in the spine are extremely rare, and information concerning these tumors in the medical literature is limited to single case reports (4–5). This pictorial essay presents the clinical, pathological, and imaging characteristics of PNET of the spine.     

MRI features of breast lymphoma: preliminary experience in seven cases

PURPOSE

We aimed to evaluate the imaging features of breast lymphoma using magnetic resonance imaging (MRI).

METHODS

This retrospective study consisted of seven patients with pathologically confirmed breast lymphoma. The breast lymphomas were primary in six patients and secondary in one patient. All patients underwent preoperative dynamic contrast-enhanced MRI and one underwent additional diffusion-weighted imaging (DWI) with a b value of 600 s/mm². Morphologic characteristics, enhancement features, and apparent diffusion coefficient (ADC) values were reviewed.

RESULTS

On MRI, three patients presented with a single mass, one with two masses, two with multiple masses, and one with a single mass and a contralateral focal enhancement. The MRI features of the eight biopsied masses in seven patients were analyzed. On MRI, the margins were irregular in six masses (75%) and spiculated in two (25%). Seven masses (87.5%) displayed homogeneous internal enhancement, while one (12.5%) showed rim enhancement. Seven masses (87.5%) showed a washout pattern and one (12.5%) showed a plateau pattern. The penetrating vessel sign was found in two masses (25%). One patient with two masses underwent DWI. Both masses showed hyperintense signal on DWI with ADC values of 0.867×10⁻³ mm²/s and 0.732×10⁻³ mm²/s, respectively.

CONCLUSION

Breast lymphoma commonly presents as a homogeneously enhancing mass with irregular margins and displays a washout curve pattern on dynamic MRI. A low ADC value may also indicate a possible diagnosis of breast lymphoma.Breast lymphoma, which constitutes only 0.04%–0.5% of all breast malignancies (1), can be divided into primary or secondary breast lymphoma (2). The majority of breast lymphomas are diffuse large B-cell lymphoma (3). The spontaneous regression of a breast lymphoma is rare and the five-year overall survival rate is 53% (1, 4). Early-stage identification and the use of radiotherapy are favorable prognostic factors, while mastectomy is associated with a poorer survival (1, 5). Therefore, a preoperative diagnosis of breast lymphoma would mean an earlier diagnosis and likely avoid unnecessary aggressive procedures.Previous studies demonstrated mammographic and ultrasonographic findings of breast lymphoma (6–8). Most lesions were high-density masses without spiculated margins and calcifications on mammography and noncircumscribed hypoechoic masses on ultrasonography (6–8). However, none were pathognomonic.Data on the magnetic resonance imaging (MRI) of breast lymphoma are limited to some single case reports (4, 7, 9–19) and small sample size case series (8, 20–23). The morphology and time-signal intensity curve (TIC) of breast lymphoma on MRI are variable. Diffusion-weighted imaging (DWI) is a functional imaging technique that is useful for distinguishing lymphoma from other malignant tumors in other systems (24, 25). However, to the best of our knowledge, the value of DWI in differentiating breast lymphoma from other malignant breast lesions has not been discussed. Therefore, the purpose of this study is to assess the MRI and DWI features of breast lymphoma.     

Targeted endovenous treatment of Giacomini vein insufficiency-associated varicose disease: considering the reflux patterns

PURPOSE

We aimed to assess the technical feasibility of targeted endovenous treatment of Giacomini vein insufficiency (GVI)-associated varicose disease and report our early results.

METHODS

We retrospectively screened 335 patients with varicose disease who underwent endovenous laser ablation from September 2011 to January 2013, and determined 17 patients who underwent Giacomini vein ablation. Using a targeted endovenous treatment approach considering the reflux pattern, all healthy great saphenous veins (GSV) or vein segments were preserved while all insufficient veins (Giacomini vein, perforator veins, small saphenous vein, anterior accessory GSV, major tributary veins, or incompetent segments of the GSV) were ablated. Treatment success was analysed using Doppler findings and clinical assessment scores before and after treatment.

RESULTS

Targeted endovenous treatment was technically successful in all cases. Seven GSVs were preserved totally and three GSVs were preserved partially (10/17, 58%), with no major complications. Clinical assessment scores and Doppler findings were improved in all cases.

CONCLUSION

Targeted endovenous treatment of GVI-associated varicose disease is safe and effective. In majority of GVI cases saphenous vein can be preserved using this approach.The Giacomini vein (GV) is defined as a branch of cranial extension of the small saphenous vein (SSV) that connects the SSV with the posterior thigh circumflex vein (PTCV) (1). In 14% of the population, SSV continues directly as the GV (2). Although most varices are caused by reflux originating from the great saphenous vein (GSV), SSV, or accessory saphenous branches, varicose disease caused by a Giacomini vein insufficiency (GVI) is not a rare condition (3, 4). GVI is commonly seen with varices that arise on the posterior thigh or calf and accounts for 4%–6% of cases treated by endovenous laser ablation (ELA) (5–8). There is no defined standard treatment for GVI-associated varicose disease. Performing a phlebectomy as the only treatment may result in recurrent varicose disease for some patients. Classical saphenous vein-focused surgical therapies may result in overtreatment or undertreatment. Targeted endovenous treatment (TET) differs from surgical treatments by focusing on the reflux sources and preserving healthy GSV, either totally or partially, while ablating insufficient segments of the vein. The ablation may be applied to any vein including the GV, perforator vein, SSV, and anterior accessory GSV, except the deep veins.ELA has recently evolved into an accepted option for eliminating truncal reflux for an incompetent GSV or SSV, with successful saphenous vein ablation rates ranging from 88% to 100% (9–12). However, reports of ELA treatment of the GVI are rare (3, 4, 7, 13). Some authors recommend only GSV ablation (4), while others ablate the insufficient GV (3). To the best of our knowledge, there is only one study on treatment of GVI considering the reflux pattern, which used both ELA and sclerotherapy (13). The present study focuses on the saphenous vein sparing effect of TET while treating the GVI by ELA and sclerotherapy.Today, reflux sources other than the saphenous veins, such as the perforator veins or GVs, are also accessible and can be treated selectively with the help of new endovenous techniques. TET considering the various reflux patterns is a minimally invasive and selective treatment method for GVI that may prevent unnecessary saphenous ablations in some cases. The purpose of this study was to evaluate the technical feasibility of TET and report early treatment results of 17 patients who had GVI with various reflux sources.     

Adverse effects of irreversible electroporation of malignant liver tumors under CT fluoroscopic guidance: a single-center experience

PURPOSE

We aimed to describe the frequency of adverse events after computed tomography (CT) fluoroscopy-guided irreversible electroporation (IRE) of malignant hepatic tumors and their risk factors.

METHODS

We retrospectively analyzed 85 IRE ablation procedures of 114 malignant liver tumors (52 primary and 62 secondary) not suitable for resection or thermal ablation in 56 patients (42 men and 14 women; median age, 61 years) with regard to mortality and treatment-related complications. Complications were evaluated according to the standardized grading system of the Society of Interventional Radiology. Factors influencing the occurrence of major and minor complications were investigated.

RESULTS

No IRE-related death occurred. Major complications occurred in 7.1% of IRE procedures (6/85), while minor complications occurred in 18.8% (16/85). The most frequent major complication was postablative abscess (4.7%, 4/85) which affected patients with bilioenteric anastomosis significantly more often than patients without this condition (43% vs. 1.3%, P = 0.010). Bilioenteric anastomosis was additionally identified as a risk factor for major complications in general (P = 0.002). Minor complications mainly consisted of hemorrhage and portal vein branch thrombosis.

CONCLUSION

The current study suggests that CT fluoroscopy-guided IRE ablation of malignant liver tumors may be a relatively low-risk procedure. However, patients with bilioenteric anastomosis seem to have an increased risk of postablative abscess formation.About 70% of hepatic metastases are nonresectable because of their anatomic location, the presence of comorbidities, or limited hepatic functional reserve (1). In these patients and in case of nonresectable primary liver tumors, percutaneous thermal ablation procedures, such as radiofrequency (RF) and microwave ablation, have become effective tools for treating hepatic malignancies (2–4). However, the effectiveness of RF and microwave treatment may be limited, either because of thermal damage to temperature-sensitive structures located in close proximity to the target tissue (5) or because of incomplete ablation of tumors adjacent to major hepatic vessels due to a phenomenon commonly termed “heat-sink effect” (6–10) which describes the loss of the applied thermal energy through the blood flow in those major vessels, whereby the effective energy application remains inadequate to ablate the target lesion.Irreversible electroporation (IRE) is a theoretically nonthermal ablation technique that delivers a series of high-voltage millisecond electrical pulses to the surrounding tissue, thus leading to irreversible disruption of the integrity of cell membranes and subsequent cell death by apoptosis (11–14). IRE may overcome the problems raised with thermal ablation: previous animal studies reported that bile ducts, blood vessels, nerves, and connective tissues are affected by IRE; however, regeneration is possible to some extent due to preservation of the tissue architecture (12, 13, 15–19). Moreover the feasibility of inducing cell death up to a vessel wall without any perivascular sparing was shown with IRE (12, 13, 18). The safety of IRE in the treatment of humans has been described (20). First reports have described potential complications after IRE, such as hemorrhage requiring blood transfusion (1.2%, two of 167 ablation procedures), portal vein thrombosis (3.2%, one of 31 ablation procedures), injury to bile ducts (1.8%, three of 167 ablation procedures), and infection (3.6%, six of 167 ablation procedures) (21, 22). However, few data are available for evaluating the potential risk factors associated with the occurrence of post-IRE complications.The purpose of this study was to review the frequency of mortality and morbidity after computed tomography (CT) fluoroscopy-guided liver IRE conducted at a single center and assess the factors influencing the occurrence of major complications.     

Genotype-phenotype correlations in hepatocellular adenoma: an update of MRI findings

Hepatocellular adenoma (HCA) is a generally benign liver tumor with the potential for malignancy and bleeding. HCAs are categorized into four subtypes on the basis of genetic and pathological features: hepatocyte nuclear factor 1α-mutated HCA, β-catenin-mutated HCA, inflammatory HCA, and unclassified HCA. Magnetic resonance imaging (MRI) plays an important role in the diagnosis, subtype characterization, and detection of HCA complications; it is also used to differentiate HCA from focal nodular hyperplasia. In this review, we present an overview of the genetic abnormalities, oncogenesis, and typical and atypical MRI findings of specific subtypes of HCA using contrast-enhanced MRI with or without hepatobiliary contrast agents (gadobenate dimeglumine and gadoxetate disodium). We also discuss their different management implications after diagnosis.Hepatocellular adenoma (HCA) is a rare, benign tumor of the liver that occurs predominantly in young and middle-aged women (1). In contrast to focal nodular hyperplasia (FNH), HCA may involve complications, such as a life-threatening bleeding and malignant degeneration (1–3). The strong association between the occurrence of HCA and the use of oral contraceptives was first acknowledged in 1970s (4), and the incidence of HCA is now thought to be 30 times greater in oral contraceptive users compared to nonusers (5, 6). A dose-dependent association and spontaneous regression following the withdrawal of estrogens have also been described (4, 7). However, the exact role of estrogen in HCA is still poorly understood.In this review, we present an overview of the typical and atypical magnetic resonance imaging (MRI) findings of different HCAs compared to FNH, and discuss various pitfalls that may be encountered with MRI.     

The potential role of modern US in the follow-up of patients with retroperitoneal fibrosis

PURPOSE

We aimed to evaluate a standardized ultrasonography (US) algorithm for the visualization of pathologic para-aortic tissue in retroperitoneal fibrosis (RPF).

MATERIALS AND METHODS

Thirty-five patients with lumbar RPF of typical extent, as determined by abdominal magnetic resonance imaging, were included. Examinations were conducted using standardized abdominal US with axial sections obtained at the levels of the renal arteries, aortic bifurcation, and both common iliac arteries. Imaging of each section was acquired with fundamental B-mode (US) and tissue harmonic imaging, respectively. In addition, we examined RPF visualized using extended field-of-view US.

RESULTS

Tissue harmonic imaging adequately visualized RPF of typical extent in 33 patients (94.2%). Excellent and good visualization with mild artifacts were achieved in 25 (71.4%) and six (17.1%) patients, respectively. When RPF spread along the iliac arteries, excellent visualization was achieved in 38.7% for the left side and 34.5% for the right side. There were significantly fewer diagnostic examinations for the right iliac (27.6%) than for the left one (9.7%) (P = 0.016). Overall, harmonic imaging achieved significantly better visualization than fundamental B-Mode (P < 0.001).

CONCLUSION

We described the first systematic evaluation of RPF visualization by modern US techniques. The best imaging quality was found in the typical RPF location, at the level of the aortic bifurcation. These results advocate for the presented US algorithm as an efficient follow-up alternative to cross-sectional imaging in RPF patients.Chronic periaortitis or retroperitoneal fibrosis (RPF) is a rare fibrosing disease that affects para-aortic tissues (1–3). It typically presents as a proliferating lumbar process surrounding the ureters and retroperitoneal vascular structures (Fig. 1) (2, 4). Sporadic, atypical manifestations in pelvic and mesenteric regions are also possible (5).Open in a separate windowFigure 1. a–c.Typical extent of the retroperitoneal fibrosis surrounding the infrarenal aorta (a). Spreading of the fibrosis to the renal arteries and along the common iliac arteries (b). Standardized US examination with four transverse sections (c). AO, aorta; AIC, common iliac artery; RA, renal artery; RPF, retroperitoneal fibrosis.Magnetic resonance imaging (MRI) allows precise evaluation of the extent and complications (6). RPF presents as hypointense (often isointense to striated muscle) plaques in native T1-weighted magnetic resonance (MR) images with significant gadolinium contrast enhancement of active and untreated retroperitoneal fibrosis (7–9).Ultrasonography (US) is primarily used in patients with RPF for a rapid and practical diagnosis of consecutive hydronephrosis (6). RPF presents as a smooth-bordered mass with either an echo-poor or echo-free signal (10, 11). Two studies in the 1980s indicated that US revealed only a poor overall sensitivity in the detection of RPF (12, 13). Feinstein et al. (14) reported that only 25% of affected patients with computed tomography (CT)-mediated diagnosis of RPF showed corresponding ultrasonographic abnormalities. Since that time the quality of US scanners has improved dramatically, and modern techniques, such as tissue harmonic imaging (THI) and extended field-of-view US, have significant advantages for routine clinical diagnosis (15–17). Today, US has established itself as an effective and cost-efficient imaging method for the screening and follow-up of infrarenal aortic aneurysms (18, 19). US, however, is not used routinely for RPF follow-up, nor has a systematic evaluation of modern ultrasonographic methods been available to date.The aim of the present study was to evaluate the potential role of modern ultrasonographic techniques for the visualization of fibrous tissue in patients with prediagnosed RPF.     

Imaging of facial nerve schwannomas: diagnostic pearls and potential pitfalls

Schwannomas are uncommon in the facial nerve and account for less than 1% of tumors of temporal bone. They can involve one or more than one segment of the facial nerve. The clinical presentations and the imaging appearances of facial nerve schwannomas are influenced by the topographical anatomy of the facial nerve and vary according to the segment(s) they involve. This pictorial essay illustrates the imaging features of facial nerve schwannomas according to their various anatomical locations and also reviews the pertinent differential diagnoses and potential diagnostic pitfalls.Facial nerve schwannomas (FNSs) are rare slow-growing tumors, accounting for less than 1% of all temporal bone tumors. They are typically solitary, unilateral, and sporadic in nature. FNSs may be bilateral as part of neurofibromatosis-2 spectrum (1, 2). Rarely, multiple schwannomas may involve peripheral branches of the facial nerve (FN) (3). The age of presentation varies from 5 to 84 years. No gender or side predilection is seen (4, 5).Histologically, FNSs are neuroectodermal in origin. They are encapsulated, benign tumors arising from the Schwann cells. They may show intratumoral cystic change and hemorrhage (3, 4, 5). Malignant schwannoma of the FN is extremely rare (6). FNSs commonly present with peripheral facial neuropathy and/or various otologic symptoms including sensorineural and conducting hearing loss (2–5). Facial paralysis is often seen at a later stage or may not be seen at all. The reasons for this are thought to be neuronal tolerance induced by the extremely slow growth of the tumor, abundant tumor vascularity, and commonly associated dehiscence of adjacent bone (7). Occasionally, FNSs may present as an intraparotid mass or as an intracranial lesion (2–5).The clinical presentations and the imaging appearances of FNSs are influenced by the topographical imaging anatomy of the FN and vary according to the segment(s) they involve (8). Here, we briefly describe the anatomy of the FN, followed by general imaging features of FNSs on computed tomography (CT) and magnetic resonance imaging (MRI), and appropriate imaging protocols. Tumor involving each segment is reviewed in relation to its characteristic clinical presentations emphasizing diagnostic pearls and potential pitfalls. The imaging examples of FNSs illustrated in this pictorial review are all histopathologically proven cases.     

Predictive factors for invasive cancer in surgical specimens following an initial diagnosis of ductal carcinoma in situ after stereotactic vacuum-assisted breast biopsy in microcalcification-only lesions

PURPOSE

The aim of this study was to determine the incidence of invasive breast carcinoma in patients with preoperative diagnosis of ductal carcinoma in situ (DCIS) by stereotactic vacuum-assisted biopsy (SVAB) performed for microcalcification-only lesions, and to identify the predictive factors of invasion.

METHODS

From 2000 to 2010, the records of 353 DCIS patients presenting with microcalcification-only lesions who underwent SVAB were retrospectively reviewed. The mammographic size of microcalcification cluster, presence of microinvasion within the cores, the total number of calcium specks, and the number of calcium specks within the retrieved core biopsy specimen were recorded. Patients were grouped as those with or without invasion in the final pathologic report, and variables were compared between the two groups.

RESULTS

The median age was 58 years (range, 34–88 years). At histopathologic examination of the surgical specimen, 63 of 353 patients (17.8%) were found to have an invasive component, although SVAB cores had only shown DCIS preoperatively. The rate of underestimation was significantly higher in patients with microcalcification covering an area of 40 mm or more, in the presence of microinvasion at biopsy, and in cases where less than 40% of the calcium specks were removed from the lesion.

CONCLUSION

Invasion might be underestimated in DCIS cases diagnosed with SVAB performed for microcalcification-only lesions, especially when the mammographic size of calcification is equal to or more than 40 mm or if microinvasion is found within the biopsy specimen and less than 40% of the calcifications are removed. At least 40% of microcalcification specks should be removed from the lesion to decrease the rate of underestimation with SVAB.Because of the widespread use of breast screening mammography, the number of women diagnosed with ductal carcinoma in situ (DCIS) has increased dramatically in recent years. DCIS is a noninvasive form of breast cancer, accounting for up to 30% of breast cancers in screening populations and approximately 5% of breast carcinomas in symptomatic patients (1–3). DCIS has a variety of mammographic presentations, but the most common mammographic feature is microcalcification (4). Indeed 80%–90% of DCIS lesions present with microcalcifications only, without any accompanying mass lesions (4). Other findings such as masses, nodular abnormalities, dilated retroareolar ducts, architectural distortions, and developing densities have also been reported (5).Ultrasound-guided biopsy is often the method of choice for sonographically visible breast lesions as it provides easy access for biopsy. However, in cases when the abnormality seen on mammography is not visible on ultrasonography, stereotactic biopsy is the recommended sampling method. For microcalcification-only lesions with no accompanying mass, ultrasonography often fails to identify the site of the lesion; hence, stereotactic biopsy is used more frequently.In most breast units, stereotactic 14-gauge automated core biopsy has been replaced by stereotactic vacuum-assisted biopsy (SVAB) using 8- to 11-gauge needles (6). Large core SVAB allows larger samples to be obtained in a shorter period of time compared with samples obtained using automated core biopsy devices (7). Moreover, this technique has the advantage of a single insertion in the area of interest compared with automated core biopsy devices, which require repeated insertions. Several published articles have shown that SVAB decreased the rate of cancer underestimation and the rate of failure to retrieve breast microcalcifications (8).The management of noninvasive and invasive breast cancers is different and therefore, an accurate preoperative diagnosis is crucial for adequate surgical planning. Underestimation of DCIS lesions occurs when an invasive component is found after surgery, which had been missed at the initial preoperative sampling. The underestimation rate of stereotactic 14-gauge automated core biopsy in DCIS was reported as 16%–35% (9–11), while that of SVAB was 5%–29% (6, 9, 11–13).The purpose of this study was to determine the rate, causes, and predictive factors of underestimation of invasive carcinoma in patients diagnosed with DCIS following SVAB of microcalcification-only lesions.     

Efficacy of CT in diagnosis of transudates and exudates in patients with pleural effusion

PURPOSE

We aimed to evaluate the efficacy of multidetector computed tomography (CT) imaging in diagnosis of pleural exudates and transudates using attenuation values.

MATERIALS AND METHODS

This retrospective study included 106 patients who were diagnosed with pleural effusion between January 2010 and June 2012. After the patients underwent chest CT, thoracentesis was performed in the first week. The attenuation values of the pleural effusions were measured in all patients.

RESULTS

According to Light’s criteria, 30 of 106 patients with pleural effusions had transudates, and the remaining patients had exudates. The Hounsfield unit (HU) value of the exudates (median, 12.5; range, 4–33) was significantly higher than that of the transudates (median, 5; range, 2–15) (P = 0.001). Additionally, when evaluated by disease subgroups, congestive heart failure and empyema were predictable in terms of median HU values of the pleural effusions with high and moderate sensitivity and specificity values (84.6% and 81.2%, respectively; 76.9% and 66.7%, respectively). Compared with other patients, the empyema patients had significantly more loculation and pleural thickening.

CONCLUSION

CT attenuation values may be useful in differentiating exu-dates from transudates. Although there is an overlap in most effusions, exudate can be considered when the CT attenuation values are >15 HU. Because of overlapping HU values, close correlation with clinical findings is essential. Additional signs, such as fluid loculation and pleural thickness, should be considered and may provide further information for the differentiation.Pleural effusion is a common clinical problem; indeed, it can arise from many diseases (1, 2). The first step in assessing a pleural effusion is to decide whether the pleural fluid is a transudate or an exudate (3). Transudate is caused by imbalances in hydrostatic and oncotic forces. It results from diseases such as heart failure, kidney failure, and cirrhosis. However, an exudate occurs when local factors influencing the accumulation of pleural fluid are altered. Exudates can be caused by clinical conditions such as pneumonia, malignancy, and thromboembolism (4).Although clinical and radiological findings may provide significant evidence about the cause(s) of pleural effusion(s), it may still be necessary to evaluate some cases with diagnostic thoracentesis (4, 5). Clinically, exudative effusion can be successfully separated from transudative effusion using Light’s criteria. The nature of the pleural effusion is based on diagnostic thoracentesis (1, 2). However, computed tomography (CT) can be used to evaluate the nature of pleural effusions to avoid the complications of thoracentesis (6, 7). Features such as pleural nodules, pleural thickening, loculation, extrapleural fat tissue thickness, and effusion density can be evaluated by CT to discriminate between exudates and transudates (8). Only two reported studies have examined CT attenuation values in patients with pleural effusions (9, 10); these showed different attenuation values for evaluation of pleural effusions.The aim of the present study was to evaluate the efficacy of multidetector CT (MDCT) images in diagnosing pleural exudates and transudates using attenuation values.     

Tempofilter II implantation in patients with lower extremity fractures and proximal deep vein thrombosis

PURPOSE

We aimed to examine the efficacy and safety of Tempofilter II (B. Braun, Melsungen, Germany) implantation to prevent pulmonary embolism in patients with lower-extremity fractures and proximal deep vein thrombosis (DVT).

MATERIALS AND METHODS

The records of patients with lower limb fractures and proximal DVT who were implanted with Tempofilter II devices from May 2004 to August 2009 were reviewed. Data collected included success rate, occurrence of pulmonary embolism, retrieval rate, and complications.

RESULTS

A total of 176 eligible patients, including 129 males (73.3%) and 47 females (26.7%) with a median age of 42.0 years (interquartile range [IQR], 34.0–52.0 years) were included in the study. Filters were successfully implanted in 174 patients (98.9%). One patient experienced a pulmonary embolism after implantation and died. Filters were removed without complications in all other patients. Median filter implantation time was 27 days (IQR, 25.0–29.0 days). Visible organized thrombi were present on the surface of 144 (82.8%) of filters after removal, and the diameter of most thrombi (n=124) ranged from 0.5 to 1.0 cm. Filters migrated <2 cm in 104 patients (59.8%) and ≥2 cm in five patients (2.9%). In these five cases, three filters migrated into the right atrium and two migrated to the orifice of the renal veins.

CONCLUSION

Tempofilter II is safe and may be useful in cases of lower extremity fracture with proximal DVT for the prevention of pulmonary embolism. The filter is easily placed and retrieved, and associated with minimal complications.Acute pulmonary embolism (PE) is one of the most common causes of death in hospitalized patients (1, 2). The mortality rate of PEs is especially high in trauma patients, as these tend to develop latent PEs. Although the mortality associated with PEs has been greatly reduced by the application of inferior vena cava filters (VCFs) (3, 4), permanent VCF implantation is associated with long-term complications such as recurrent deep vein thrombosis (DVT), filter dislocation, migration, and rupture (5–8). Thus, for patients with a long life expectancy and transient risk for venous thromboembolism, nonpermanent VCF placement is preferred (6). Currently, two types of nonpermanent filters are available: temporary and retrievable filters. Retrievable filters can be used to prevent PE in trauma patients during the high-risk period while avoiding the complications associated with long-term placement (9, 10). If a thrombus is trapped by the filter, the filter can be maintained at the original position and removed after thrombus resolution (5). However, because the recommended usage time of this type of filter is relatively short (usually 12 days), the extraction rate is low and many are left in place permanently (11).The Tempofilter II (B. Braun, Melsungen, Germany) is a second-generation temporary caval filter with an indwelling time of up to six weeks (12). The filter is placed and retrieved by means of a tethered cable fixed to a subcutaneous anchoring device. There is only one prior large-scale study, including placement of 104 Tempofilter II filters in 103 patients with PE, DVT, or both (12). They reported only one case of PE after filter placement, no mechanical complications related to the filter, and successful retrieval in all but one case regardless of thrombus entrapment (12).The purpose of this study was to examine the efficacy and safety of the Tempofilter II in Chinese patients with lower extremity fractures and proximal DVT.     

Use of shear wave elastography to differentiate benign and malignant breast lesions

PURPOSE

We aimed to determine the correlations between the elasticity values of solid breast masses and histopathological findings to define cutoff elasticity values differentiating malignant from benign lesions.

MATERIALS and METHODS

A total of 115 solid breast lesions of 109 consecutive patients were evaluated prospectively using shear wave elastography (SWE). Two orthogonal elastographic images of each lesion were obtained. Minimum, mean, and maximum elasticity values were calculated in regions of interest placed over the stiffest areas on the two images; we also calculated mass/fat elasticity ratios. Correlation of elastographic measurements with histopathological results were studied.

RESULTS

Eighty-three benign and thirty-two malignant lesions were histopathologically diagnosed. The minimum, mean, and maximum elasticity values, and the mass/fat elasticity ratios of malignant lesions, were significantly higher than those of benign lesions. The cutoff value was 45.7 kPa for mean elasticity (sensitivity, 96%; specificity, 95%), 54.3 kPa for maximum elasticity (sensitivity, 95%; specificity, 94%), 37.1 kPa for minimum elasticity (sensitivity, 96%; specificity, 95%), and 4.6 for the mass/fat elasticity ratio (sensitivity, 97%; specificity, 95%).

CONCLUSION

SWE yields additional valuable quantitative data to ultrasonographic examination on solid breast lesions. SWE may serve as a complementary tool for diagnosis of breast lesions. Long-term clinical studies are required to accurately select lesions requiring biopsy.Breast cancer is associated with high morbidity; ∼1.38 million new cases and 458 000 deaths occur annually worldwide (1). Breast cancer is by far the most common cancer in females of both developed and developing countries, and remains a major public health problem.Annual mammographic screening is valuable for early detection of breast cancer, reducing mortality and morbidity, particularly of patients with tumors in fatty breast tissue (2). Increase in breast tissue density over time is a serious problem; this reduces the diagnostic accuracy of breast cancer, especially in younger females (3). Thus, as the proportion of glandular breast tissue rises, other imaging methods are required (4).Gray-scale ultrasonography is a valuable adjunct to mammography and other breast imaging methods, affording highly sensitive assessment of breast masses and differentiating benign solid breast lesions from those that are malignant (5–7). However, ultrasonography is strongly subjective and poorly specific (8–10).Breast biopsy remains the gold standard for definitive diagnosis of suspicious breast lesions. Although the total number of females referred for interventional diagnostic procedures represents a small percentage of any screened population, the healthcare resources consumed by such females are disproportionately high (11). Further, the pathological result is benign in up to 75% of all cases (11–13). Therefore, a reliable, noninvasive, costeffective method helping to differentiate benign from malignant breast lesions, thus reducing the number of unnecessary interventional diagnostic procedures, would be valuable.Sonoelastography uses ultrasound to assess tissue stiffness (elasticity), which can be described using Young’s modulus: E=σ/ε, where σ is the applied stress and ε the resultant tissue deformation. Two principal sonoelastographic approaches are available; these are static (strain) and transient (vibration; shear wave) elastography. In static elastography, a transducer is used to compress tissue and the resulting strain is presented as a color map of tissue elasticity superimposed on the real-time gray-scale sonogram.Static elastography is associated with significant interobserver variability, and uses elastographic scoring (ES) or strain ratio (SR) measurement as a diagnostic parameter. Both ES and SR are subjective semi-quantitative measures (14, 15). Shear wave elastography (SWE) is a novel technique applicable to soft tissue. In SWE, transverse shear waves spreading laterally from the tissue are tracked, and the speed of propagation calculated. SWE yields real-time quantitative data and is highly reproducible compared to static elastography (16, 17). Reproducibility of the latter technique is considered to be a major problem and may compromise patient outcomes. Thus, further work on the utility of SWE is needed.In the present study we sought to correlate the SWE values of a series of solid breast masses with histopathological findings, and to determine cutoff elasticity values allowing benign and malignant tumors to be distinguished.     

Adrenal venous sampling for stratifying patients for surgery of adrenal nodules detected using dynamic contrast enhanced CT

PURPOSE

We aimed to assess the value of adrenal venous sampling (AVS) for diagnosing primary aldosteronism (PA) subtypes in patients with a unilateral nodule detected on adrenal computed tomography (CT) and scheduled for adrenalectomy.

MATERIALS AND METHODS

This retrospective study included 80 consecutive patients with PA undergoing CT and AVS. Different lateralization indices were assessed, and a cutoff established using receiver operating characteristic curve analysis. The value of CT alone versus CT with AVS for differentiating PA subtypes was compared. The adrenalectomy outcome was assessed, and predictors of cure were determined using univariate analysis.

RESULTS

AVS was successful in 68 patients. A cortisol-corrected aldosterone affected-to-unaffected ratio cutoff of 2.0 and affected-to-inferior vena cava ratio cutoff of 1.4 were the best lateralization indices, with accuracies of 82.5% and 80.4%, respectively. CT and AVS diagnosed 38 patients with aldosterone-producing adenomas, five patients with unilateral adrenal hyperplasia, and 25 patients with bilateral adrenal hyperplasia. Of the 52 patients with a nodule detected on CT, subsequent AVS diagnosed bilateral adrenal hyperplasia in 14 patients (27%). Compared to the results of combining CT with AVS, the accuracy of CT alone for diagnosing aldosterone-producing adenomas was 71.1% (P < 0.001). The cure rate for hypertension after adrenalectomy was 39.2%, with improvement in 53.5% of patients. On univariate analysis, predictors of persistent hypertension were male gender and preoperative systolic blood pressure.

CONCLUSION

To avoid inappropriate surgery, AVS is necessary for diagnosing unilateral nodules with aldosterone hypersecretion detected by CT.Primary aldosteronism (PA) is the most common form of secondary hypertension, with a prevalence of 5%–11% (1–3). PA is due primarily to the hypersecretion of aldosterone by an aldosterone-producing adenoma (APA) or unilateral (primary) adrenal hyperplasia (UAH), which constitute 30%–40% of cases; the remainder are presumed to be secondary to idiopathic bilateral adrenal hyperplasia (BAH) (1, 4, 5). APA and UAH are two forms of unilateral aldosterone hypersecretion, and both are curable with adrenalectomy. BAH induces bilateral aldosterone hypersecretion, and anti-aldosterone drugs are used in its medical management (5–7).The plasma aldosterone-to-renin ratio is used to screen for PA in patients at high risk for PA (8). Recent guidelines recommend using computed tomography (CT) of the adrenal gland to categorize the subtype after confirming PA. However, CT cannot reliably visualize a microadenoma or distinguish between an incidentaloma or BAH and APA. It has been suggested that adrenal venous sampling (AVS) be performed to determine the subtype of PA and to differentiate between unilateral and bilateral production of aldosterone preoperatively (9). AVS to measure the adrenal vein aldosterone and cortisol is the gold standard for lateralizing aldosterone secretion (10). Lateralization is defined using several ratios. In patients with APA or UAH, a unilateral adrenalectomy results in a complete cure or improved hypertension and potassium normalization in approximately 30% of patients, with reported rates up to 86% (11–15).This study assessed several lateralization ratios to establish the most predictive of unilateral disease. We also compared the CT results with those of bilateral AVS for differentiating the PA subtype, with the assumption that AVS is necessary before surgery, even in patients with nodules <10 mm detected with CT. Finally, we assessed the outcomes of adrenalectomy in our patients to identify preoperative predictors of a good outcome.     

Effect of the time to intervention on the outcome of thrombosed dialysis access grafts managed percutaneously

PURPOSE

We aimed to investigate the effect of the time interval from the clinical presentation of a thrombosed dialysis access graft to intervention on procedure success.

MATERIALS AND METHODS

Records from two academic institutions for patients who underwent percutaneous thrombectomy of occluded surgical hemodialysis graft access sites in interventional radiology from 2006 to 2011 were reviewed retrospectively. The following data were recorded: gender, age, time and date of the initial request for a thrombectomy and the procedure, age of the surgical access, angiographic outcome, and clinical outcome (successful or unsuccessful postinterventional dialysis). Univariate and multivariate logistic regression were used to evaluate whether the time to intervention significantly affected the study endpoint.

RESULTS

In total, 268 percutaneous thrombectomies were performed in 139 patients. Of these 224 (83.5%) were categorized as successful and 44 (16.4%) as unsuccessful. The time to intervention was 19.9±30.1 vs. 22±35 hours for successful and unsuccessful procedures, respectively. The difference between the two was not significant, and there were also no significant differences in covariate distributions between successful and unsuccessful outcomes.

CONCLUSION

During the first 72 hours following clinical presentation of a thrombosed dialysis access graft, time to intervention may be considered independent of procedure outcome.Patent vascular access is critical for patients with kidney failure who rely on regularly scheduled hemodialysis. Detailed evidence-supported guidelines have been developed regarding vascular access placement (1–4), and much has been written about the surveillance, maintenance, biology, cost, and interventional techniques for these accesses (5–15). Similarly, predictors of success following radiological intervention of these access sites have been evaluated, including pressure, the degree of stenosis, and procedure type (16, 17). Patient age, access site, underlying comorbidities, the serum albumin level, and systemic systolic pressure over time have been evaluated as potential predictors of graft patency following intervention (16, 18). Nevertheless, the optimal timing of intervention for thrombosed dialysis access remains unknown. This study investigated the relationship between the time elapsed from clinical thrombosis presentation and intervention on the procedural success as defined by anatomic (angiographic) and clinical (subsequent dialysis) outcome variables (19).     

Clinical applications of the C-arm cone-beam CT-based 3D needle guidance system in performing percutaneous transthoracic needle biopsy of pulmonary lesions

PURPOSE

This study explored the value of flat detector C-arm CT-guidance system in performing percutaneous transthoracic needle biopsy (PTNB) for lung lesions in clinical practice.

METHODS

A total of 110 patients with solid lung lesions were enrolled to undergo PTNB procedures. The mean diameter of lesions was 4.63 cm (range, 0.6–15cm). The needle path was carefully planned and calculated on the C-arm CT system, which acquired three-dimensional CT-like cross-sectional images. The PTNB procedures were performed under needle guidance with fluoroscopic feedbacks.

RESULTS

Histopathologic tissue was successfully obtained from 108 patients with a puncture success rate of 98.2% (108/110). The diagnostic accuracy rate was found to be 96.3% (104/108). There was only one case of pneumothorax (0.9%) requiring therapy. The rates of mild pneumothorax and hemoptysis were low (12.0% and 6.5%, respectively). In addition, procedural time could be limited with this technique, which helped to reduce X-ray exposure.

CONCLUSION

Our study shows that C-arm CT-based needle guidance enables reliable and efficient needle positioning and progression by providing real-time intraoperative guidance.Lung cancer is the commonest cause of a pulmonary mass, which can be identified through chest X-ray or computed tomography (CT) examinations (1, 2). Accurate identification of histopathological cell type is crucial to determine the right treatment method and reduce the morbidity and mortality rates. Image-guided percutaneous transthoracic needle biopsy (PTNB) is a widely accepted technique for characterization of pulmonary mass that is not reachable by broncoscopy. CT has been considered as the technique of choice for guiding PTNB procedures as it enables detailed visualization of the lesion and surrounding tissue structures. This technique offers good in-plane resolution. However, the view is limited to the plane that the needle is inserted, causing double-oblique approach with an angulated needle trajectory which is difficult to perform, time consuming (25–27 minutes), and heavily relies on the experience of the clinicians (3). The introduction of CT fluoroscopy (CTF) enables real-time visualization of the needle advancement. Thus, the challenges correlated with displacement and disappearance of small lesions from scan planes due to respiratory movement in conventional CT-guided PTNB can be overcome, leading to a reduced procedural time (12–24 minutes) (4). Nevertheless, CTF may result in higher radiation dose to clinicians (5–9). Besides, according to previous studies, lesion size is a determining factor in diagnostic accuracy of CT- or CTF-guided PTNB, which yields 75%–90% diagnostic accuracy, with correlated rates of 15%–20% for pneumothorax and 2%–3% for pneumothorax requiring drainage (10–14). In addition, due to the limited size of the gantry, CT- or CTF-guided PTNB procedures in obese patients can be technically challenging or impossible.Nowadays, flat detector-equipped angiographic C-arm cone-beam CT (CBCT) systems can be used to acquire CT-like cross-sectional images directly within the interventional radiology suite (15–17). The CBCT systems offer real-time visualization of PTNB procedure and more flexibility in the orientation of the detector system around the patient compared to traditional CT systems. Thus, CBCT could provide image guidance for PTNB procedures, combining the advantages of CT and fluoroscopic guidance, as it is proved to be valuable for evaluating pulmonary lesions even smaller than 2 cm. This technique has been shown to yield 90%– 98% diagnostic accuracy, 94%–97% sensitivity, and 75%–100% specificity. The incidence of complications was 20%–39%, the associated procedural time ranged 11.9–18.1 minutes and exposure dose ranged 170–275 mGy (3, 18–24). Along with the development of CBCT, a novel technique has recently emerged for PTNB guidance. It combines advanced virtual needle path planning based on user interactions using three-dimensional (3D) CBCT images with real-time fluoroscopic guidance (21, 25). This technique offers high spatial resolution of less than 1 mm, as well as contrast resolution of 10 HU, which is adequate for lung imaging, as lung inherently has a high contrast (soft tissue against air). In addition, CBCT allows good access to the patient without any patient transfer or movement, increasing the effectiveness and efficacy of clinical workflow.The purpose of this study is to explore the value of using a CBCT-based 3D needle guidance system in performing PTNB for pulmonary lesions in the interventional radiology suite.     

Optimal reconstruction interval in dual source CT coronary angiography: a single-center experience in 285 patients

PURPOSE

We aimed to evaluate the visibility of coronary arteries and bypass-grafts in patients who underwent dual source computed tomography (DSCT) angiography without heart rate (HR) control and to determine optimal intervals for image reconstruction.

MATERIALS AND METHODS

A total of 285 consecutive cases who underwent coronary (n=255) and bypass-graft (n=30) DSCT angiography at our institution were identified retrospectively. Patients with atrial fibrillation were excluded. Ten datasets in 10% increments were reconstructed in all patients. On each dataset, the visibility of coronary arteries was evaluated using the 15-segment American Heart Association classification by two radiologists in consensus.

RESULTS

Mean HR was 76±16.3 bpm, (range, 46–127 bpm). All coronary segments could be visualized in 277 patients (97.19%). On a segment-basis, 4265 of 4275 (99.77%) coronary artery segments were visible. All segments of 56 bypass-grafts in 30 patients were visible (100%). Total mean segment visibility scores of all coronary arteries were highest at 70%, 40%, and 30% intervals for all HRs. The optimal reconstruction intervals to visualize the segments of all three coronary arteries in descending order were 70%, 60%, 80%, and 30% intervals in patients with a mean HR <70 bpm; 40%, 70%, and 30% intervals in patients with a mean HR 70–100 bpm; and 40%, 50%, and 30% in patients with a mean HR >100 bpm.

CONCLUSION

Without beta-blocker administration, DSCT coronary angiography offers excellent visibility of vascular segments using both end-systolic and mid-late diastolic reconstructions at HRs up to 100 bpm, and only end-systolic reconstructions at HRs over 100 bpm.Improvements in computed tomography (CT) scanning technology throughout the last decade have resulted in widespread acceptance of contrast-enhanced multidetector CT (MDCT) coronary angiography as a reliable modality for noninvasive evaluation of the coronary arteries (1). Having a high negative predictive value, MDCT coronary angiography is considered particularly beneficial in patients with low to intermediate pretest probability for coronary artery disease (CAD) by reliably excluding coronary artery stenosis and therefore, preventing unnecessary invasive angiography (2, 3).Small dimensions and continuous rapid motions of coronary arteries make their visualization by CT challenging. Thus, excellent spatial and temporal resolution is required for adequate imaging of coronary arteries. Initial reports using a 4-detector row MDCT were promising in selected patients with low heart rates (HRs) (4–6); however, image quality was not sufficient for assessment in up to 29% of the coronary segments. With the introduction of 16- and 64-row MDCT, major improvements of image quality were achieved, with adequate visualization of up to 97% of coronary segments (7–9). Since, image quality deteriorates with increasing HRs even with 64-slice MDCT scanners (10, 11), it has been common in clinical practice to use HR-modulating beta-blockers to achieve better diagnostic quality. In 2005, dual source CT (DSCT) system equipped with two sets of X-ray tubes and corresponding detectors mounted onto the gantry with an angular offset of 90° was introduced (12). Using half-scan reconstruction algorithms, this system provides high temporal resolution (83 milliseconds [ms]) that corresponds to a quarter gantry rotation time. Preliminary studies without use of beta-blocker premedication have shown that DSCT coronary angiography provides good image quality of coronary arteries even at a relatively high HR (13, 14). Subsequent studies with relatively small patient populations confirmed these findings with diagnostic image quality in 97.8% of coronary artery segments (15, 16).Achievement of good image quality with DSCT coronary angiography is highly dependent upon selecting the optimal reconstruction interval for evaluation. Previous publications indicate a relationship between optimal reconstruction window and HR with mid- to end-diastolic reconstructions providing better image quality at low HRs, whereas at faster HRs, end-systolic reconstructions will often provide the dataset with the least motion artifact (17–19). However, some of these prior studies were based on relatively small patient samples, and in some, the entire R-R interval was not evaluated. Detection of optimal reconstruction interval is also important for the purpose of radiation dose reduction. Since DSCT scanners are equipped with electrocardiogram (ECG)-based tube current modulation, the width and timing of the ECG pulsing window, during which the full tube current is given, can be manually selected by the operator with the tube current outside the pulsing window decreased to 20% or 4% of the nominal tube current and thus, significantly reducing the radiation dose up to 40% (20).We aimed to evaluate the visibility of coronary arteries and bypass-grafts in patients who underwent DSCT angiography without HR control and to determine optimal intervals for image reconstruction.