The effect of beam purity and scanner complexity on proton CT accuracy.

PURPOSE: To determine the dependence of the accuracy in reconstruction of relative stopping power (RSP) with proton computerized tomography (pCT) scans on the purity of the proton beam and the technological complexity of the pCT scanner using standard phantoms and a digital representation of a pediatric patient. METHODS: The Monte Carlo method was applied to simulate the pCT scanner, using both a pure proton beam (uniform 200 MeV mono-energetic, parallel beam) and the Northwestern Medicine Chicago Proton Center (NMCPC) clinical beam in uniform scanning mode. The accuracy of the simulation was validated with measurements performed at NMCPC including reconstructed RSP images obtained with a preclinical prototype pCT scanner. The pCT scanner energy detector was then simulated in three configurations of increasing complexity: an ideal totally absorbing detector, a single stage detector and a multi-stage detector. A set of 15 cm diameter water cylinders containing either water alone or inserts of different material, size, and position were simulated at 90 projection angles (4° steps) for the pure and clinical proton beams and the three pCT configurations. A pCT image of the head of a detailed digital pediatric phantom was also reconstructed from the simulated pCT scan with the prototype detector. RESULTS: The RSP error increased for all configurations for insert sizes under 7.5 mm in radius, with a sharp increase below 5 mm in radius, attributed to a limit in spatial resolution. The highest accuracy achievable using the current pCT calibration step phantom and reconstruction algorithm, calculated for the ideal case of a pure beam with totally absorbing energy detector, was 1.3% error in RSP for inserts of 5 mm radius or more, 0.7 mm in range for the 2.5 mm radius inserts, or better. When the highest complexity of the scanner geometry was introduced, some artifacts arose in the reconstructed images, particularly in the center of the phantom. Replacing the step phantom used for calibration with a wedge phantom led to RSP accuracy close to the ideal case, with no significant dependence of RSP error on insert location or material. The accuracy with the multi-stage detector and NMCPC beam for the cylindrical phantoms was 2.2% in RSP error for inserts of 5 mm radius or more, 0.7 mm in range for the 2.5 mm radius inserts, or better. The pCT scan of the pediatric phantom resulted in mean RSP values within 1.3% of the reference RSP, with a range error under 1 mm, except in exceptional situations of parallel incidence on a boundary between low and high density. CONCLUSIONS: The pCT imaging technique proved to be a precise and accurate imaging tool, rivaling the current x-rays based techniques, with the advantage of being directly sensitive to proton stopping power rather than photon interaction coefficients. Measured and simulated pCT images were obtained from a wobbled proton beam for the first time. Since the in-silico results are expected to accurately represent the prototype pCT, upcoming measurements using the wedge phantom for calibration are expected to show similar accuracy in the reconstructed RSP.

Operation of the Preclinical Head Scanner for Proton CT.

We report on the operation and performance tests of a preclinical head scanner developed for proton computed tomography (pCT). After extensive preclinical testing, pCT is intended to be employed in support of proton therapy treatment planning and pre-treatment verification in patients undergoing particle-beam therapy. In order to assess the performance of the scanner, we have performed CT scans with 200 MeV protons from both the synchrotron of the Loma Linda University Medical Center (LLUMC) and the cyclotron of the Northwestern Medicine Chicago Proton Center (NMCPC). The very high sustained rate of data acquisition, exceeding one million protons per second, allowed a full 360° scan to be completed in less than 7 minutes. The reconstruction of various phantoms verified accurate reconstruction of the proton relative stopping power (RSP) and the spatial resolution in a variety of materials. The dose for an image with better than 1% uncertainty in the RSP is found to be close to 1 mGy.

Community-acquired Klebsiella pneumoniae liver abscess: an emerging infection in Ireland and Europe.

INTRODUCTION: Klebsiella pneumoniae has emerged as a predominant cause of community-acquired mono-microbial pyogenic liver abscess. This was first described in Taiwan and has been widely reported in Asia. This infectious entity has been described in Europe, with single case reports predominating. METHODS: We present three cases in one year from our institution in Ireland and review the European literature to date. RESULTS/CONCLUSION: Klebsiella pneumoniae invasive liver abscess syndrome is now emerging in Europe and notably is not restricted to individuals of Asian descent.

Double trouble--duplication of the gallbladder requiring repeat laparoscopic cholecystectomy.

Duplication of the gallbladder is a surprisingly common phenomenon. Clinically, these patients present with straightforward gallbladder pathologies. It is a challenging preoperative diagnosis on ultrasound, and most cases are diagnosed intra-operatively. We present a case of gallbladder duplication, where the patient presented with biliary colic, had a straightforward laparoscopic cholecystectomy, and then represented with biliary colic four years later.

A review of the imaging and intervention of liver transplant complications.

Liver transplantation has become a successful surgical solution to a variety of medical and oncological parenchymal liver diseases. As a result, these patients are being encountered more frequently within diagnostic imaging departments which may be remote from the transplant centre. Radiologists must therefore be proficient in identifying normal post-transplant anatomy which involves the anastomosis of four structures between the donor and recipient, namely the hepatic artery, the main portal vein, the retro-hepatic inferior vena cava and the extra-hepatic bile ducts. A number of potential complications can arise involving any or all of these structures, which can be potentially devastating and lead to graft failure. Radiologists must familiarise themselves with the normal post-operative appearances of liver transplantation and become competent in diagnosing post-transplant complications. Where possible, complications should be treated using interventional radiological techniques, thus avoiding the need for repeat surgical intervention or retransplantation.

Removal of T-fasteners 2 days after gastrostomy is feasible.

T-fastener gastropexy is widely performed as part of gastrostomy insertion. The current literature recommends removal of T-fasteners at 2 weeks. We present a series of patients in whom T-fasteners were removed at 2 days with no major complications. We removed T-fasteners in 109 patients (male-to-female ratio 59:50, age range 18 to 88 years, mean age 62 years) at 2 days after gastrostomy insertion. Indications for gastrostomy included amytrophic lateral sclerosis, cerebrovascular accidents, head and neck carcinoma, multiple sclerosis, and others, including brain tumours and chronic inflammatory demyelinating polyneuropathy. No peritubal leaks or other major complications were seen in the study population. In the study group, 15 minor complications were recorded (14%), including localised infection and pain, both of which resolved on removal of T-fasteners. We conclude that it is feasible and safe to remove T-fasteners at 2 days.

Ultrasound-guided removal of Implanon devices.

Our study has shown that ultrasound-guided localisation and removal of Implanon rods is safe, practical and highly successful. Over a 4-year period, 119 patients had successful, uncomplicated removal of their subdermal devices.The technique is particularly useful for removal of the device when it is not palpable or when an attempt at removal of a palpable device has not been successful.

Imaging of adenomyomatosis of the gall bladder.

Adenomyomatosis is a relatively common abnormality of the gall bladder, with a reported incidence of between 2.8 and 5%. Although mainly confined to the adult study group, a number of cases have been reported in the paediatric study group. It is characterized pathologically by excessive proliferation of the surface epithelium and hypertrophy of the muscularis propria of the gall bladder wall, with invagination of the mucosa into the thickened muscularis forming the so-called 'Rokitansky-Aschoff' sinuses. The condition is usually asymptomatic and is often diagnosed as an incidental finding on abdominal imaging. The radiological diagnosis is largely dependent on the visualization of the characteristic Rokitansky-Aschoff sinuses. As the condition is usually asymptomatic, the importance of making a correct diagnosis is to prevent misinterpretation of other gall bladder conditions such as gall bladder cancer, leading to incorrect treatment. In the past, oral cholecystography was the main imaging method used to make this diagnosis. In most institutions, oral cholecystography is no longer carried out, and the diagnosis is now more commonly seen on cross-sectional imaging. In this review article, we describe the manifestations of adenomyomatosis on the various imaging methods, with an emphasis on more modern techniques such as magnetic resonance cholangiopancreatography. A brief section on oral cholecystography to aid readers familiar with this technique in understanding the comparable imaging features on more modern imaging techniques is included.

Efficacy and safety of the angioseal vascular closure device post antegrade puncture.

In this study, the efficacy and safety of the Angioseal vascular closure device post antegrade puncture of the common femoral artery (CFA) for lower limb vascular interventional procedures are evaluated. A retrospective analysis of the medical records of 60 consecutive patients who were referred for interventional procedures in the superficial femoral artery (SFA) or popliteal artery (popl. art.) was performed. Antegrade puncture was successfully performed in 58 of 60 patients (96.6%). Indications included right SFA angioplasty (n = 35), left SFA angioplasty (n = 17), right popl. art. angioplasty (n = 5), and left popl. art. angioplasty (n = 1). Hemostasis was achieved by, on an intention-to-treat basis, the Angioseal vascular closure device in 46 patients and manual compression in 12 patients. Manual compression was used instead of Angioseal because of severe calcified arterial wall plaques (n = 7), failed deployment of the Angioseal (n = 4), and left SFA dissection (n = 1). There were no major recorded complications in the Angioseal group despite the use of antiplatelet or anticoagulant medications. Twenty-three (50%) of the patients in the Angioseal group were discharged within 24 h. Thirty-seven of the 46 patients who received an Angioseal device had undergone a previous ipsilateral CFA puncture (time range, 2 days to 56 months; mean, 6.2 months). Nine of these patients had undergone ipsilateral Angioseal deployment in the previous 3 months. We conclude that the Angioseal vascular closure device is a safe and efficient means of achieving hemostasis post antegrade puncture.

Percutaneous antegrade ureteric stent removal using a rigid alligator forceps.

To evaluate the safety and efficacy of percutaneous antegrade ureteric stent removal using a rigid alligator forceps. Twenty patients were included in our study. Indications for ureteric stent insertion included stone disease (n = 7), malignancy (n = 8) and transplant anastomotic strictures (n = 5). Stent retrieval was carried out for proximal stent placement/migration in seven patients and encrustation in the remaining 13. Twenty-two stents were successfully retrieved in 20 patients. There was one technical failure (5%). There were no major complications. We had four minor complications, which included nephrostomy site pain (n = 2), periprocedural sepsis (n = 1) and a small urinoma (n = 1). All patients settled with conservative management. Percutaneous radiologically guided antegrade ureteric stent removal with an alligator forceps is safe and effective, particularly when initial surgical removal has failed.

Emergency embolization of multiple splenic artery pseudoaneurysms associated with portal hypertension complicating cystic fibrosis.

Cystic fibrosis (CF) is the most common potentially lethal genetic disease in the white population. Improvements in life expectancy have led to an increasing recognition of hepatobiliary complications from CF. Splenic artery aneurysms are a rare complication of portal hypertension with a high mortality due to their significant potential for rupture, resulting in life-threatening i.p. haemorrhage. The optimum treatment of ruptured splenic artery aneurysms is controversial. This case describes the successful emergency embolization of multiple splenic artery pseudoaneurysms associated with portal hypertension complicating cystic fibrosis.

Vesicoureteric reflux in the adult.

Vesicoureteric reflux (VUR) is a well-recognized entity in the paediatric population, but is not well described or understood in the adult population. This is partly explained by the fact that its incidence declines with advancing age. Its diagnosis is, however, still important, with VUR accounting for at least 10% of adult patients with end-stage renal disease. With early detection and careful management, the secondary complications of VUR such as renal failure can be prevented. Imaging plays a major role in the detection and evaluation of VUR in the adult patient. Conventional techniques such as micturating cystourethrograms have now been supplemented by cross-sectional imaging with CT and MRI. In this review article, we comprehensively review the up to date status of imaging the adult patient with VUR and discuss important subgroups of patients such as pregnant and transplant patients.

Does a full bladder aid upper tract visualization in magnetic resonance urography?

The aim of this study was to evaluate whether a full bladder improved the visualization of the upper renal tract during magnetic resonance urography (MRU). Twenty volunteers were recruited into the study. The MRU imaging was carried out on a 1.5-T MR system. Imaging was carried out in the coronal plane using a half-Fourier acquired single-shot turbo-spin-echo technique. All volunteers were examined in two separate MRU studies to visualize the urinary tract. The first study was carried out with a 'full' bladder followed by a study with an 'empty' bladder, leading to a total of 40 examinations. Two radiologists then reviewed maximum intensity projection images from both 'full' and 'empty' studies independently. Both left and right upper tracts were divided into five segments. A three-point grading system was used to evaluate visualization. Excellent visualization = 3, good visualization = 2 and poor visualization = 1. Maximum score per patient was 30. Results were tabulated and analysed using an Excel database. The average score for visualization for the 'full' bladder group was 22.1/30 (73.8%) and the average score for the empty bladder was 16.2/30 (54%). Overall improvement in visualization was 5.9/30 (19.8%). There was strong interobserver agreement, with a concordance value of 92.5%. The MRU carried out in healthy young adult volunteers with a full bladder allows improved visualization of the upper tracts.

Imaging and intervention of retroperitoneal fibrosis.

Retroperitoneal fibrosis is a rare condition characterized by the development of fibrous plaques in the retroperitoneal space. The fibrous plaques characteristically arise distal to the bifurcation of the abdominal aorta and progress to encase the iliac vessels distally and are defined by the associated encasement of one or both ureters. Imaging plays an important role in not only establishing the diagnosis, but also in monitoring disease progression. Historically, the radiological diagnosis was made predominantly by intravenous urography and retrograde pyelography. More recently, advances in cross-sectional imaging with ultrasound and contrast-enhanced CT have allowed for a more precise diagnosis as well as helping to accurately define the extent of the disease. At our institution, we have found ultra-fast MRI to also play a useful role in establishing the diagnosis. In particular, magnetic resonance urography using HASTE (half Fourier-acquired single shot turbo spin-echo) sequences allow a safe alternative to intravenous urography, particularly in patients with poor renal function. The purpose of this article is to describe the role of the various imaging methods available to the radiologist and to emphasize the important role that the interventional radiologist now plays, not only in obtaining tissue for diagnosis, but also in providing treatment of the disease by percutaneous nephrostomy drainage and subsequent stent placement in select cases.

CT-guided bone biopsy: Initial experience with a commercially available hand held Black and Decker drill.

PURPOSE: To describe the use of a simple commercially available Black and Decker hand based drill in performing CT-guided bone biopsies. MATERIALS AND METHODS: Three international institutions were enrolled in the study. In each centre, a fellowship trained musculoskeletal radiologist directed the assessment of a hand based commercial drill for performing CT-guided bone biopsies. A specially designed component was engineered which allowed the connection of a standard bone biopsy set to a commercial drill. The component was distributed to the three centres involved. Over a 3-year period, data from all three institutions was collected. Information regarding technical success, diagnostic data and complication rates were all collated to assess the technical feasibility of this technique. RESULTS: In total 68 patients underwent bone biopsy using a hand held commercial drill. Technical success was achieved in 65 patients. Diagnostic material was obtained in 53 patients. Non-diagnostic material was obtained in 12 patients. Five out of the 12 patients with non-diagnostic material had repeat biopsies with diagnostic material obtained in 2 of these. No major complications occurred in any patient. CONCLUSION: CT-guided bone biopsy using a hand held commercial drill has a technically high success rate with minimal complications.

Imaging of acute pyelonephritis in the adult.

The diagnosis of acute pyelonephritis in adults is predominantly made by a combination of typical clinical features of flank pain, high temperature and dysuria combined with urinalysis findings of bacteruria and pyuria. Imaging is generally reserved for patients who have atypical presenting features or in those who fail to respond to conventional therapy. In addition, early imaging may be useful in diabetics or immunocompromised patients. In such patients, imaging may not only aid in making the diagnosis of acute pyelonephritis, but more importantly, it may help identify complications such as abscess formation. In this pictorial review, we discuss the role of modern imaging in acute pyelonephritis and its complications. We discuss the growing role of cross-sectional imaging with computed tomography (CT) and novel magnetic resonance imaging (MRI) techniques that may be used to demonstrate both typical as well as unusual manifestations of acute pyelonephritis and its complications. In addition, conditions such as emphysematous and fungal pyelonephritis are discussed.

Gunther Tulip retrievable inferior vena caval filters: indications, efficacy, retrieval, and complications.

PURPOSE: We evaluated the Gunther Tulip (GT) retrievable inferior vena cava (IVC) filter with regard to indications, filtration efficacy, complications, retrieval window, and use of anticoagulation. METHOD: A retrospective study was performed of 147 patients (64 men, 83 women; mean age 58.8 years) who underwent retrievable GT filter insertion between 2001 and 2005. The indications for placement included a diagnosis of pulmonary embolism or deep venous thrombosis with a contraindication to anticoagulation (n = 68), pulmonary embolism or deep venous thrombosis while on anticoagulation (n = 49), prophylactic filter placement for high-risk surgical patients with a past history of pulmonary embolism or deep venous thrombosis (n = 20), and a high risk of pulmonary embolism or deep venous thrombosis (n = 10). Forty-nine of the 147 patients did not receive anticoagulation (33.7%) while 96 of 147 patients did, 82 of these receiving warfarin (56.5%), 11 receiving low-molecular weight heparins (7.58%), and 3 receiving antiplatelet agents alone (2.06%). RESULTS: Filter placement was successful in 147 patients (100%). Two patients had two filters inserted. Of the 147 patients, filter deployment was on a permanent basis in 102 and with an intention to retrieve in 45 patients. There were 36 (80%) successful retrievals and 9 (20%) failed retrievals. The mean time to retrieval was 33.6 days. The reasons for failed retrieval included filter struts tightly adherent to the IVC wall (5/9), extreme filter tilt (2/9), and extensive filter thrombus (2/9). Complications included pneumothorax (n = 4), failure of filter expansion (n = 1), and breakthrough pulmonary embolism (n = 1). No IVC thrombotic episodes were recorded. DISCUSSION: The Gunther Tulip retrievable filter can be used as a permanent or a retrievable filter. It is safe and efficacious. GT filters can be safely retrieved at a mean time interval of 33.6 days. The newly developed Celect filter may extend the retrieval interval.

Recurrent pyogenic cholangitis due to chronic infestation with Clonorchis sinensis (2006: 8b).

Recurrent pyogenic cholangitis is a common disease in Southeast Asia, where an association with the liver fluke Clonorchis sinensis is postulated. It is characterised by repeated attacks of cholangitis with multiple recurrences of bile duct stones and strictures. We present a case of recurrent pyogenic cholangitis due to chronic infestation with Clonorchis sinensis in a young Asian immigrant, describing its radiological appearances and also therapeutic strategies with a review of additional examples from the literature.