ALBIRA: a small animal PET∕SPECT∕CT imaging system

PURPOSE

The authors have developed a trimodal PET∕SPECT∕CT scanner for small animal imaging. The gamma ray subsystems are based on monolithic crystals coupled to multianode photomultiplier tubes (MA-PMTs), while computed tomography (CT) comprises a commercially available microfocus x-ray tube and a CsI scintillator 2D pixelated flat panel x-ray detector. In this study the authors will report on the design and performance evaluation of the multimodal system.

METHODS

X-ray transmission measurements are performed based on cone-beam geometry. Individual projections were acquired by rotating the x-ray tube and the 2D flat panel detector, thus making possible a transaxial field of view (FOV) of roughly 80 mm in diameter and an axial FOV of 65 mm for the CT system. The single photon emission computed tomography (SPECT) component has a dual head detector geometry mounted on a rotating gantry. The distance between the SPECT module detectors can be varied in order to optimize specific user requirements, including variable FOV. The positron emission tomography (PET) system is made up of eight compact modules forming an octagon with an axial FOV of 40 mm and a transaxial FOV of 80 mm in diameter. The main CT image quality parameters (spatial resolution and uniformity) have been determined. In the case of the SPECT, the tomographic spatial resolution and system sensitivity have been evaluated with a (99m)Tc solution using single-pinhole and multi-pinhole collimators. PET and SPECT images were reconstructed using three-dimensional (3D) maximum likelihood and ordered subset expectation maximization (MLEM and OSEM) algorithms developed by the authors, whereas the CT images were obtained using a 3D based FBP algorithm.

RESULTS

CT spatial resolution was 85 μm while a uniformity of 2.7% was obtained for a water filled phantom at 45 kV. The SPECT spatial resolution was better than 0.8 mm measured with a Derenzo-like phantom for a FOV of 20 mm using a 1-mm pinhole aperture collimator. The full width at half-maximum PET radial spatial resolution at the center of the field of view was 1.55 mm. The SPECT system sensitivity for a FOV of 20 mm and 15% energy window was 700 cps∕MBq (7.8 × 10(-2)%) using a multi-pinhole equipped with five apertures 1 mm in diameter, whereas the PET absolute sensitivity was 2% for a 350-650 keV energy window and a 5 ns timing window. Several animal images are also presented.

CONCLUSIONS

The new small animal PET∕SPECT∕CT proposed here exhibits high performance, producing high-quality images suitable for studies with small animals. Monolithic design for PET and SPECT scintillator crystals reduces cost and complexity without significant performance degradation.

Comparison of acquisition of resistant microorganisms and infections in critically-ill patients with and without malignancies

BACKGROUND

Patients with malignancies are often considered at risk of acquiring infections by resistant or potentially resistant microorganisms (RPRMs). However, data supporting this contention is scarce. We have compared critically ill patients with haematological malignancies (HM), solid tumours (ST) and without cancer (NC) in terms of acquisition of RPRMs, infections and mortality.

METHODS

Observational, prospective cohort study of patients admitted to a medical intensive care unit (ICU). Swabbing of nares, pharynx and rectum, and culture of respiratory secretions were obtained within 48 h of admission and thrice weekly thereafter. Clinical samples were obtained as deemed necessary by the attending physician. Clinical variables, severity scores on admission and exposures during ICU stay were also collected. Multivariable logistic regression analysis was used to evaluate ICU mortality.

RESULTS

Out of 969 included patients 127 (13.1%) had HM and 93 (9.6%) had ST. Patients with malignancies were more frequently exposed to central venous catheterization, methylprednisolone, and any antipseudomonal antibiotic whereas they were less commonly exposed to invasive mechanical ventilation. Patients with HM were more often admitted with an infection. There were no differences among groups in terms of RPRMs acquisition during ICU stay or prevalence of ICU-acquired infections due to any microorganism, including RPRMs. Having a HM was an independent predictor of mortality regardless of APACHE II score.

CONCLUSION

Critically ill cancer patients did not show a higher rate of RPRMs acquisition nor ICU-acquired infections. Mortality was higher in the HM group and it was not accurately predicted on admission by APACHE II score.

Epidemiology and prognostic determinants of bacteraemic catheter-acquired urinary tract infection in a single institution from 1991 to 2010

OBJECTIVES

To determine the epidemiology of bacteraemic Catheter-Acquired Urinary Tract Infection (CA-UTI) and to identify independent predictors of mortality.

METHODS

This study was part of a bloodstream infection surveillance study that prospectively collected data on consecutive patients with bacteraemia in our institution from 1991 to 2010. Factors associated with 30-day mortality were determined.

RESULTS

CA-UTI was the confirmed source of 1007 bacteraemias. The most common microorganisms isolated were Escherichiacoli (42%), Klebsiella spp (15%), Enterococcus faecalis (12%) and Pseudomonas aeruginosa (12%). Along the 2006-2010 periods, antibiotic-resistant E. coli and Klebsiella spp isolates accounted for 49% of the bacteraemia due to CA-UTI. Shock and mortality accounted for 125 and 92 cases, respectively (12% and 9%). Factors associated with mortality were: inappropriate empirical treatment (OR: 1.86, 95% CI: 1.48-2.44), ultimately or rapidly fatal prognosis of underlying disease (OR: 2.56, 95% CI: 1.48-4.44) and shock on presentation (OR: 12.62, 95% CI: 7.61-20.95). Inappropriate empirical treatment was most frequent in cases of bacteraemia produced by antibiotic-resistant E. coli or Klebsiella spp, Enterococcus spp. and P. aeruginosa. Factors associated with the isolation of a microorganism of this type were previous antibiotic therapy and healthcare-associated bacteraemia (OR: 1.50, 95% CI: 1.16-2.14 and OR: 3.03, 95% CI: 2.22-4.01, respectively).

CONCLUSIONS

In cases of previous antibiotic therapy or healthcare-associated bacteraemic CA-UTI may indicate the need to initiate empirical therapy activity against antibiotic-resistant Enterobacteriaceae, E. faecalis and P. aeruginosa.

Expectation maximization (EM) algorithms using polar symmetries for computed tomography (CT) image reconstruction

We suggest a symmetric-polar pixellation scheme which makes possible a reduction of the computational cost for expectation maximization (EM) iterative algorithms. The proposed symmetric-polar pixellation allows us to deal with 3D images as a whole problem without dividing the 3D problem into 2D slices approach. Performance evaluation of each approach in terms of stability and image quality is presented. Exhaustive comparisons between all approaches were conducted in a 2D based image reconstruction model. From these 2D approaches, that showing the best performances were finally implemented and evaluated in a 3D based image reconstruction model. Comparison to 3D images reconstructed with FBP is also presented. Although the algorithm is presented in the context of computed tomography (CT) image reconstruction, it can be applied to any other tomographic technique as well, due to the fact that the only requirement is a scanning geometry involving measurements of an object under different projection angles. Real data have been acquired with a small animal (CT) scanner to verify the proposed mathematical description of the CT system.

Meningeal Involvement in Wegener Granulomatosis: Case Report and Review of the Literature

Wegener Granulomatosis (WG) is a multisystem autoimmune disorder characterized by necrotizing granulomatous vasculitis that most commonly involves the upper respiratory tract, lungs, and kidneys. The involvement of the central nervous system (CNS) is infrequent and can cause stroke, cranial nerve abnormalities, cerebrovascular events, seizures, and meningeal involvement. Meningeal involvement is rare and may occur due to local vasculitis, directly spread from adjacent disease in the skull base, paranasal or orbital region. We describe the case of a 20-year-old Caucasian man who was diagnosed with sinonasal WG with frontal focal meningeal involvement. A literature review on diagnosis and treatment of meningeal involvement in course of WG was carried out. The importance of an early diagnosis and treatment of localized WG has been emphasized, in order to avoid the progression to a severe form of disease, especially in younger patients and in paucisymptomatic cases.

Long-term outcome of acute prosthetic joint infections due to gram-negative bacilli treated with retention of prosthesis

OBJECTIVE

To update the clinical information of the 47 patients with a prosthetic joint infection due to Gram-negative bacilli included in a previous study and to reassess the predictors of failure after a longer follow-up.

METHODS

Using the electronic files of our hospital, all the information regarding readmissions to the hospital, new surgical procedures and the reason for the new surgery (infection, aseptic loosening), and the last visit in the hospital were registered. The medical chart of the 35 patients that were considered in remission in the previous publication was reviewed.

RESULTS

In 30 patients no clinical evidence of failure was detected and no additional surgery on the previously infected prosthesis was necessary and they were considered in long-term remission. In 5 cases a late complication was identified. One case had a reinfection due to coagulase-negative staphylococci after 22 months from the open debridement and required a 2-stage revision surgery. The other 4 cases developed an aseptic loosening and it was necessary to perform a 1-stage exchange. Receiving a fluoroquinolone when all the Gram-negatives involved in the infection were susceptible to fluoroquinolones was the only factor associated with remission in the univariate analysis (p=0.002).

CONCLUSION

After a long-term follow-up, our results support the importance of using fluoroquinolones in acute PJI due to Gram-negative bacilli.

Epidemiology and prognostic determinants of bacteraemic biliary tract infection

OBJECTIVES

To determine the epidemiology of bacteraemia due to biliary tract infection (BTI) and to identify independent predictors of mortality.

METHODS

This study was part of a bloodstream infection surveillance study that prospectively collected data on consecutive patients with bacteraemia in our institution from 1991 to 2010. BTI was the confirmed source of 1373 patients with bacteraemia, and the independent prognostic factors of 30 day mortality were determined.

RESULTS

The mean age of patients with biliary sepsis was 71 years (± 14 years). The most frequent comorbidities were biliary lithiasis and solid-organ cancer [484 cases (35%) and 362 cases (26%), respectively]. The BTI was healthcare-associated in 33% of patients. Shock and mortality accounted for 209 and 126 cases, respectively (15% and 9%). The most frequent microorganisms isolated were Escherichia coli (749, 55%), Klebsiella spp. (240, 17%), Enterococcus spp. (171, 12%), Pseudomonas aeruginosa (86, 6%) and Enterobacter spp. (63, 5%). There were 47 (3%) cefotaxime-resistant (CTX-R) E. coli or Klebsiella spp. Inappropriate empirical antibiotic treatment was an independent factor associated with mortality (OR 1.4, 95% CI 1.1-1.7). Inappropriate empirical treatment was more frequent in P. aeruginosa and CTX-R Enterobacteriaceae bacteraemia. These microorganisms were significantly more common in patients with previous antibiotic therapy, solid-organ cancer or transplantation and in healthcare-associated bacteraemia.

CONCLUSIONS

In patients with bacteraemic BTI, inappropriate empirical therapy was more frequent in P. aeruginosa and CTX-R Enterobacteriaceae infection and was associated with a higher mortality rate. In patients with bacteraemia due to BTI and solid-organ cancer or transplantation, healthcare-associated infection or previous antibiotic treatment, initial therapy with piperacillin/tazobactam or a carbapenem would be advisable.

Giant cell arteritis and polymyalgia rheumatica after influenza vaccination: report of 10 cases and review of the literature

Giant cell arteritis (GCA) and polymyalgia rheumatica (PMR) are inflammatory rheumatic diseases common in people over the age of 50 years. Herein, we report 10 cases of previously healthy subjects who developed GCA/PMR within 3 months of influenza vaccination (Inf-V). A Medline search uncovered additional 11 isolated cases of GCA/PMR occurring after Inf-V. We discuss the role of individual susceptibility, the potential function of immune adjuvants as triggers of autoimmunity post-vaccination, and the correlation of our observation with the ‘ASIA’ syndrome, i.e. autoimmune/inflammatory syndrome induced by adjuvants and including post-vaccination phenomena.

Usefulness of monitoring linezolid trough serum concentration in prolonged treatments

Linezolid has proven valuable in musculoskeletal infections, however, failure and resistance have been described and toxicity is worrisome when more than 28 days are necessary. We describe the first 5 cases in whom linezolid trough serum concentrations were weekly measured and its relationship with clinical outcome and toxicity.

Comparison of a low-pressure and a high-pressure pulsatile lavage during débridement for orthopaedic implant infection

INTRODUCTION

The aim of our study was to compare the effectiveness of high-pressure pulsatile lavage and low-pressure lavage in patients with an orthopaedic implant infection treated with open débridement followed by antibiotic treatment.

PATIENTS AND METHODS

Patients with an orthopaedic implant infection requiring open débridement from January 2008 to August 2009 were randomized prospectively to a low-pressure or a high-pressure pulsatile lavage arm. Relevant information about demographics, co-morbidity, type of implant, microbiology data, surgical treatment, and outcome were recorded. Comparison of proportions was made using χ(2) test or Fisher exact test when necessary. The Kaplan-Meier survival method was used to estimate the cumulative probability of treatment failure from open débridement to the last visit.

RESULTS

Seventy-nine patients were included. There were no differences between the main characteristics between both groups (p > 0.05). Mean (SD) age of the whole cohort was 70.2 (11.9) years. There were 46 infections on knee prosthesis, 17 on hip prosthesis, 7 on hip hemiarthroplasties and 9 on osteosynthesis devices. There were 69 acute post-surgical infections, 8 acute haematogenous infections and 2 chronic infections. The most common microorganisms isolated were coagulase-negative Staphylococci in 34 cases, Staphylococcus aureus in 26 and Escherichia coli in 19 cases. There were 30 polymicrobial infections. A total of 42 and 37 patients were randomized to a high-pressure pulsatile or a low-pressure lavage, respectively. There was no difference in the success rate between both arms (80.9 vs. 86.5%, p = 0.56).

CONCLUSION

The use of a high-pressure pulsatile lavage during open débridement of implant infections had a similar success rate as a low-pressure lavage.

Feasibility and effectiveness of laparoscopic incisional hernia repair after liver transplantation

BACKGROUND

Incisional hernia is a frequent problem after liver transplantation. It is related to immunosuppression, use of steroids, obesity, as well as the type of incision. Laparoscopic repair shows a lower rate of complications in terms of infection and recurrence, as well as reduced postoperative pain and faster recovery.

METHODS

We reviewed our experience with laparoscopic incisional hernia repair (LIHR) in patients after liver transplantation, using the BARD Composix mesh which is composed of two layers of polypropylene and polytetrafluoroethylene (PTFE) and fixed with metal ProTack.

RESULTS

Between March 2002 and April 2010, we performed 20 LIHR in 17 male and three female subjects of overall mean age of 58.3 years, and body mass Index of 31.05 kg/m(2). The mean size of the defects was 215.25 cm(2). All patients had undergone bilateral subcostal incisions with a midline extension, and seven had additional operations after the transplantation for various reasons. There were no differences in immunosuppression. Three patients had needed steroid boluses for acute graft rejection episodes. There was no conversion of therapy. The size of mesh was 18 × 23 cm in seven cases and 20 × 25 in 12 cases. The mean postoperative hospital stay was 2.1 days. Oral feeding was initiated a few hours after surgery, and routine immunosuppression was not discontinued. There were no major early complications. During follow-up, we identified one patient with a mesh infection (5%) and one with a recurrence (5%).

CONCLUSION

LIHR is safe and feasible even for major hernias after liver transplantation with few complications.

Outcome and predictors of treatment failure in early post-surgical prosthetic joint infections due to Staphylococcus aureus treated with debridement

Experience with debridement and prosthesis retention in early prosthetic joint infections (PJI) due to Staphylococcus aureus is scarce. The present study aimed to evaluate the outcome and predictors of failure. Patients prospectively registered with an early PJI due to S. aureus and 2 years of follow-up were reviewed. Demographics, co-morbidity, type of implant, clinical manifestations, surgical treatment, antimicrobial therapy and outcome were recorded. Remission was defined when the patient had no symptoms of infection, the prosthesis was retained and C-reactive protein (CRP) was ≤ 1 mg/dL. Univariate and multivariate analysis were performed. Fifty-three patients with a mean ± SD age of 70 ± 10.8 years were reviewed. Thirty-five infections were on knee prosthesis and 18 were on hip prosthesis. The mean ± SD duration of intravenous and oral antibiotics was 10.6 ± 6.7 and 88 ± 45.9 days, respectively. After 2 years of follow-up, 40 (75.5%) patients were in remission. Variables independently associated with failure were the need for a second debridement (OR 20.4, 95% CI 2.3-166.6, p 0.006) and a CRP > 22 mg/dL (OR 9.8, 95% CI 1.5-62.5, p 0.01). The onset of the infection within the 25 days after joint arthroplasty was at the limit of significance (OR 8.3, 95% CI 0.8-85.6, p 0.07). Debridement followed by a short period of antibiotics is a reasonable treatment option in early PJI due to S. aureus. Predictors of failure were the need for a second debridement to control the infection a CRP > 22 mg/dL and the infection onset within the first 25 days after joint arthroplasty.