Radiologic-pathologic correlation of the CT halo sign in invasive pulmonary aspergillosis

CT Halo sign: A systematic review

PURPOSE

The CT Halo sign or Halo sign (HS) refers to ground-glass opacity surrounding a nodule or mass in the lung parenchyma. We conducted a systematic review to find the etiological associations of HS. We also evaluated the diagnostic performances of HS for invasive fungal infections (IFI) in immunosuppressed patients.

METHOD

The systematic review was conducted as per PRISMA guidelines. We searched the PubMed and EMBASE database till June 2018 without any restrictions. Only case reports, case series and original articles published in English language were included. A database created from the electronic searches was compiled and subsequent analysis was done. [PROSPERO registration: CRD42018094739] RESULTS: 168 studies were eligible, which included 51 case reports, 15 prospective studies, 102 retrospective studies. A total of 1977 patients (out of 6371) with HS were identified with age range between <1year-94years. The most common diagnosis in the immunosuppressed, mixed, immunocompetent and not specified groups were IFI (86.9 %, n = 1194), Cryptococcosis (51.6 %, n = 124), Cryptococcosis (40 %, n = 20) and lung neoplasms (81.8 %, n = 36) respectively. 14 studies (11 retrospective, 3 prospective) were included in quantitative analysis. The pooled sensitivity(sn), specificity(sp) and odd's ratio (OR) of HS for diagnosing IFI were 50.4 %, 91 % and 6.61 respectively. Also, HS could not reliably differentiate IPA from mucormycosis in the pooled analysis.

CONCLUSIONS

HS can be seen in a large number of diverse conditions both in immunosuppressed and immunocompetent population. In immunosuppressed patients HS is specific for IFI but cannot rule it out. Additionally, it cannot reliably distinguish between IPA and mucormycosis.

Utility of CT assessment in hematology patients with invasive aspergillosis: a post-hoc analysis of phase 3 data

BACKGROUND

Pulmonary computed tomography (CT) scans are commonly used as part of the clinical criteria in diagnostic workup of invasive fungal diseases like invasive aspergillosis, and may identify radiographic abnormalities, such as halo signs or air-crescent signs. We assessed the diagnostic utility of CT assessment in patients with hematologic malignancies or those who had undergone allogeneic hematopoietic stem cell transplantation in whom invasive aspergillosis was suspected.

METHODS

This post-hoc analysis assessed data from a prospective, multicenter, international trial of voriconazole (with and without anidulafungin) in patients with suspected invasive aspergillosis (IA; proven, probable, or possible, using 2008 European Organisation for Research and Treatment of Cancer/Invasive Fungal Infections Cooperative Group and the National Institute of Allergy and Infectious Diseases Mycoses Study Group criteria) [NCT00531479]. Eligible patients received at least one baseline lung CT scan.

RESULTS

Of 395 patients included in this post-hoc analysis, 240 patients (60.8%) had 'confirmed' proven (9/240, 3.8%) or probable (231/240, 96.3%) invasive aspergillosis (cIA) and 155 patients (39.2%) had 'non-confirmed' invasive aspergillosis (all nIA; all possible IA (de Pauw et al., Clin Infect Dis 46:1813-21, 2008)). Mean age was 52.3 and 50.5 years, 56.3 and 60.0% of patients were male, and most patients were white (71.7 and 71.0%) in the cIA and nIA populations, respectively. Median baseline galactomannan was 1.4 (cIA) and 0.2 (nIA), mean Karnofsky score was 65.3 (cIA) and 66.8 (nIA), and mean baseline platelet count was 48.0 (cIA) and 314.1 (nIA). Pulmonary nodules (46.8% of all patients), bilateral lung lesions (37.5%), unilateral lung lesions (28.4%), and consolidation (24.8%) were the most common radiographic abnormalities. Ground-glass attenuation (cIA: 24.2%; nIA: 11.6%; P < 0.01) and pulmonary nodules (cIA: 52.5%; nIA: 38.1%; P < 0.01) were associated with cIA. Other chest CT scan abnormalities (including halo signs and air-crescent signs) at baseline in patients with hematologic malignancy or hematopoietic stem cell transplantation, and suspected IA, were not associated with cIA.

CONCLUSIONS

These findings highlight the limitations in the sensitivity of chest CT scans for the diagnosis of IA, and reinforce the importance of incorporating other available clinical data to guide management decisions on individual patients, including whether empirical treatment is reasonable, pending full evaluation.

TRIAL REGISTRATION

NCT00531479 (First posted on ClinicalTrials.gov on September 18, 2007).

Diagnosing filamentous fungal infections in immunocompromised patients applying computed tomography-guided percutaneous lung biopsies: a 12-year experience

Background

Invasive fungal diseases (IFD) are an important cause of morbidity and mortality in immunocompromised patients, and early diagnosis and management are a challenge. We evaluated the clinical utility of computed tomography (CT)-guided percutaneous lung biopsies in diagnosing IFD.

Methods

Between 2003 and 2014, we analyzed 2671 CT-guided lung biopsies, from which 157 were IFD associated; we aimed to determine microbiological-based diagnostic accuracy of calcofluor white staining (CFWS), culture, Aspergillus antigen detection (GM), broad-range fungal PCR, and Aspergillus PCR per sample.

Results

127 (81%) specimens were microscopically positive for any fungal elements, 30 (19%) negative. Aspergillus and non-Aspergillus like hyphae were obtained in 85 (67%) and 42 (33%) specimens, respectively. CFWS positivity was defined as proof of infection. Sensitivity, specificity, and positive (PPV) and negative predictive (NPV) values for CT scan were 100, 44, 80, and 100%, for Aspergillus PCR 89, 58, 88, and 58%, for broad-range fungal PCR 90, 83, 95, and 90%, and for GM 94, 83, 95, and 90%. The most common CT features were patchy opacifications with central necrosis (78%) or cavern defects (50%), less common were air bronchograms (39%) or ground glass halos (39%), and all other features were rare. The overall pneumothorax rate subsequent to biopsy was 19%, but in only 2% of all cases the placement of a chest tube was indicated. One case of fatal air embolism occurred.

Conclusions

CT-guided lung biopsies have high diagnostic accuracy in terms of microscopic examination, and complication rates are low. Molecular-based and antigen tests applied on fungal hyphae-positive specimens showed comparable results.

Computed Tomography in Invasive Pulmonary Aspergillosis

Early recognition of invasive pulmonary aspergillosis and of other similar angiotrophic fungal pneumonias has been claimed in previous reports to be possible with computed tomography (CT) and may improve survival of immunocompromised hosts. Chest CT was performed, in the course of fungal pneumonia, in 11 leukemia patients with chemotherapy-induced neutropenia, either with (n=8) or without (n=5) contrast enhancement. Early (n=5, before the 7th day from the beginning of the clinical setting) chest CT always demonstrated one or more nodules or mass-like infiltrates surrounded by a halo of low attenuation. This halo was absent in middle (n=4, after 7 days) and later (n=4, after 15 days) CT examinations. The contrast-enhanced nodules or mass-like infiltrates showed a peripheral enhancement in 4/8 cases with a target feature (hyperdense peripheral ring and isodense central area). CT showed a non-specific enlargement of liver and spleen in 2 patients. Early chest CT should be used in the management of opportunistic pneumonias.

Multidetector Computed Tomography and MR Imaging Findings in Mycotic Infections

Fungal infections constitute a diverse spectrum of infections with variable clinical and imaging features. They are commonly opportunistic infections that affect immunocompromised individuals secondary to inherited or acquired disorders. Fungal infections may affect multiple organ systems and contribute to significant morbidity and mortality. Although the imaging features of some fungal infections are characteristic and permit their diagnosis, many mycotic infections manifest nonspecific findings. Definitive diagnosis often depends on histopathological analysis. Early diagnosis requires both clinical suspicion and supporting radiological evidence. Early treatment results in reduced morbidity and mortality. This article reviews the imaging findings in opportunistic and endemic fungal infections.

Reduced perfusion in pulmonary infiltrates of high-risk hematologic patients is a possible discriminator of pulmonary angioinvasive mycosis: a pilot volume perfusion computed tomography (VPCT) study

RATIONALE AND OBJECTIVES

The aim of this study was to assess perfusion parameters in atypical pneumonia of heavily immunocompromised hematologic patients suspected of having invasive mycosis using volume perfusion computed tomography and establish their diagnostic role.

MATERIALS AND METHODS

Volume perfusion computed tomographic data from 21 consecutive immunocompromised patients presenting with atypical parenchymal opacity of consolidation were analyzed with respect to the degree of perfusion of their pneumonias. All patients presented with clinical and laboratory signs of infection. Seventeen patients (10 men, seven women; mean age, 57 years; age range, 19-76 years) were found with proven (n = 9), probable (n = 2), or possible (n = 6) angioinvasive mycosis. One patient was diagnosed with bronchoinvasive aspergillosis. Four patients (all men; mean age, 71 years; age range, 67-79 years) were diagnosed with bacterial pneumonia. Volume perfusion computed tomography of the involved pulmonary areas was performed at 80 kV and 60 mAs, with 26 measurement points distributed over 65.9 seconds. Fifty milliliters of contrast material was injected at a rate of 5 mL/s, followed by a 50-mL saline chaser. Entire coverage of the pneumonic parenchymal consolidation was obtained in all patients, with the generation of parametric maps of blood flow (BF) using the maximal slope model and blood volume (BV) using Patlak analysis. The results of perfusion measurements were then analyzed and evaluated for all patients.

RESULTS

Patients with proven, probable, or possible angioinvasive pulmonary fungal infection revealed very low levels of perfusion of their parenchymal consolidations, with BFs ranging from 0.01 to 23.86 mL/100 mL tissue/min and BVs ranging from 0.88 to 10.67 mL/100 mL tissue, lower than those of the adjacent thoracic musculature and of bacterial pneumonias. Bacterial pneumonias showed all increased perfusion parameters, with BFs ranging from 30.49 to 41.65 mL/100 mL tissue/min and BVs ranging from 10.07 to 49.90 mL/100 mL tissue. The cutoff BF value for differentiation was 23.89 mL/100 mL tissue/min, and the cutoff BV value was 9.6 mL/100 mL tissue.

CONCLUSIONS

Patients with angioinvasive pulmonary mycosis showed lower perfusion parameters on volume perfusion computed tomography compared to those experiencing bacterial pneumonia.

The role of multidetector computed tomography in the early diagnosis of invasive pulmonary aspergillosis in patients with febrile neutropenia undergoing hematopoietic stem cell transplantation

OBJECTIVE

To evaluate vessel involvement and the role of multidetector computed tomography (MDCT) in the earlydiagnosis of invasive pulmonary aspergillosis (IPA) in patients with febrile neutropenia and antibiotic-resistant feverundergoing autologous bone morrow transplantation.

MATERIAL AND METHODS

In all, 74 pulmonary MDCT examinations in 37 consecutive hematopoietic stem celltransplantation patients with febrile neutropenia and clinically suspected IPA were retrospectively evaluated.

RESULTS

Diagnosis of IPA was based on Fungal Infections Cooperative Group, and National Institute of Allergy andInfectious Diseases Mycoses Study Consensus Group criteria. In all, 0, 14, and 11 patients were diagnosed as proven,probable, and possible IPA, respectively. Among the 25 patients accepted as probable and possible IPA, all had pulmonaryMDCT findings consistent with IPA. The remaining 12 patients were accepted as having fever of unknown origin (FUO)and had patent vessels based on MDCT findings.In the patients with probable and possible IPA, 72 focal pulmonary lesions were observed; in 41 of the 72 (57%) lesionsvascular occlusion was noted and the CT halo sign was observed in 25 of these 41 (61%) lesions. Resolution of feveroccurred following antifungal therapy in 19 (76%) of the 25 patients with probable and possible IPA. In all, 6 (25%)of the patients diagnosed as IPA died during follow-up. Transplant-related mortality 100 d post transplant in patientswith IPA and FUO was 24% and 0%, respectively.

CONCLUSION

In conclusion, MDCT has a potential role in the early diagnosis of IPA via detection of vessel occlusion.

An animal experiment about early pulmonary candidiasis in immunosuppressive rabbits: thin-section CT images dynamically observed and proved by histopathological results

BACKGROUND

Early detection and treatment of pulmonary fungal infection in immunocompromised patients has a profound impact on mortality. However, information available about the thin-section computed tomography (CT) findings of Candida pneumonia has largely been limited to isolated cases seen in reviews of various infections and to other acute lung diseases seen in immunocompromised patients.

PURPOSE

To dynamically observe and evaluate CT findings in immunosuppressed animals with histopathologically confirmed pulmonary candidiasis at the acute stage.

MATERIAL AND METHODS

Twenty-four New Zealand rabbits were randomly divided into an experimental group (n = 21) and a control group (n = 3). Pulmonary candidiasis was established by C. albicans inoculation via a transtracheal route in immunosuppressed rabbits in the experimental group, and an equivalent amount of normal saline was injected via the same way in the control group. Chest CT scan was performed before and on alternative days after inoculation/injection. Microbiological and pathological results were obtained by autopsy.

RESULTS

In the experiment group, pulmonary candidiasis was successfully established in 13 rabbits as confirmed by microbiology and pathology. Areas of air-space consolidation were present in 10 (10/13) rabbits, with lobular distribution in six and lobar or segmental distribution in four, pathologically presenting as bronchopneumonia or hemorrhagic lung infarcts. Areas of ground-glass opacity (GGO) were identified in five (5/13) rabbits, three of which were associated with other abnormalities, presenting as bronchopneumonia or interstitial pneumonitis. Multiple nodules were seen in three (3/13) rabbits. They were clustered around bronchovascular bundles in two rabbits, and subpleural in the remaining one, pathologically presenting as hemorrhagic granulomas. Other less common CT findings included thickening of bronchovascular bundles (n = 3), linear opacity (n = 1), and pneumothorax (n = 1). No abnormality was detected by CT scan and pathological examination in the three rabbits of the control group.

CONCLUSION

Peripheral multiple areas of lobular consolidation and/or GGO representing bronchopneumonia were the most common thin-section CT findings of pulmonary candidiasis at the early stage.

Intensive-care unit lung infections: The role of imaging with special emphasis on multi-detector row computed tomography

Nosocomial pneumonia is the most frequent hospital-acquired infection. In mechanically ventilated patients admitted to an intensive-care unit as many as 7-41% may develop pneumonia. The role of imaging is to identify the presence, location and extent of pulmonary infection and the presence of complications. However, the poor resolution of bedside plain film frequently limits the value of radiography as an accurate diagnostic tool. To date, multi-detector row computed tomography with its excellent contrast resolution is the most sensitive modality for evaluating lung parenchyma infections.

The value of computed tomography-guided percutaneous lung biopsy for diagnosis of invasive fungal infection in immunocompromised patients

We assessed Calcofluor white staining, Aspergillus polymerase chain reaction, and a galactomannan enzyme immunoassay for diagnosis of fungal infection with use of computed tomography-guided percutaneous lung biopsy specimens obtained from 61 patients. The sensitivity and specificity of computerized tomography, Aspergillus polymerase chain reaction, and galactomannan enzyme immunoassay were 100% and 50%, 100% and 86%, and 88% and 94%, respectively.

Fungal pneumonia due to molds in patients with hematological malignancies

Invasive fungal infections are an important cause of morbidity and mortality in patients with hematological malignancies. In particular, patients with neutropenia and those who have undergone allogeneic hematopoietic stem cell transplantation are at highest risk, with fungal pneumonia being the main clinical manifestation in these patients. The most common pathogens associated with fungal pneumonia are Aspergillus spp. and Zygomycetes. However, other pathogens have also been observed in fungal pneumonia, including Cryptococcus spp., Pneumocystis jirovecii, and Candida spp. This comprehensive review will focus on the important practical aspects relevant to the epidemiology, clinical diagnosis, and therapeutic management of pneumonia due to filamentous fungi in patients affected by hematological malignancies.

Long-term CT follow-up in 40 non-HIV immunocompromised patients with invasive pulmonary aspergillosis: kinetics of CT morphology and correlation with clinical findings and outcome

OBJECTIVE

The aim of this study was to assess CT signs of invasive pulmonary aspergillosis (IPA) and their long-term kinetics in correlation with clinical findings and outcome.

MATERIALS AND METHODS

Three hundred ten serial CT scans (mean, 7.7) in 40 consecutive patients were reviewed retrospectively over a median follow-up of 112 days (range, 5-841 days). Along with underlying disease, hematopoietic stem cell transplantation, neutropenia, graft-versus-host disease or antifungal treatment, signs of IPA, and number or size of lesions were evaluated regarding outcome and radiologic dynamics.

RESULTS

On the day of IPA diagnosis, median lesion number and size were 3 or 3.1 cm(2), respectively. Irrespective of antifungal therapy, 90% of patients showed an increase in lesion size and number until day 9 (median and mean). Lesion size subsequently showed a median plateau phase of 3.5 days (mean, 7), during which median lesion numbers dropped by 17%. Consequently, 42.5% of patients showed a complete radiologic remission within a median 80 days. Of all parameters, formation of cavitation most strongly predicted time until radiologic remission, which was 2.5 times as long in patients with cavitary lesions. Likewise, cavitations were strong precursors of beneficial outcome (odds ratio, 8.4; confidence interval [CI], 1.07-176).

CONCLUSION

The kinetics of radiologic signs of IPA adheres to a distinctive pattern with initial rise in number and size, followed by a plateau phase of size and gradual reduction. Both time until complete radiologic remission and outcome are independent of initial or maximum lesion size and number yet strongly influenced by cavitation.

Pulmonary Complications of Transplantation: Radiographic Considerations

The aim of this article is to clarify radiographic definitions associated with common parenchymal patterns encountered in the transplant population and to discuss the most common pathologic causes responsible for each pattern. The article also touches on radiographic findings signifying complications of other intrathoracic structures, including the airways, pleural space, and mediastinum.

Invasive pulmonary aspergillosis: frequency and meaning of the “hypodense sign” on unenhanced CT

The purpose of this study was to establish the diagnostic value of central hypointensity ("hypodense sign") in lung consolidations or nodules, in severely immunocompromised or neutropenic patients, suspected of having invasive pulmonary aspergillosis (IPA), and to assess its recognition on unenhanced CT scans. Serial CT scans of the lung were retrospectively reviewed in 43 consecutive immunosuppressed patients with IPA, and assessed for the presence of the hypodense sign using standard mediastinal and lung windowing settings, as well as a special, narrower window setting (width 110-140 HU; level 15-40 HU). The temporal relationship between the occurrence of the first CT-finding suspicious of IPA and the appearance of the hypodense sign, as well as between this and the occurrence of the crescent sign, cavitation or reduction in lesion size, was evaluated. Additionally, CT-scans from 89 immunocompromised patients with viral (n=45) or bacterial (n=44) pneumonia, investigated in the same time period at our institution were reviewed, with respect to the presence of the "hypodense" sign. Unenhanced CT scans revealed the hypodense sign in 11 neutropenic patients and 2 severely immunocompromised patients, out of a total of 43 patients with IPA evaluated in this study (30.2%). The mean time between the appearance of the first CT-findings of IPA (large nodule or consolidation +/- positive halo sign) and the hypodense sign was 7.8 days, while the time interval between the hypodense sign and the occurrence of crescent sign, cavitation, or decrease of the lesion's size was 8.3 days. The hypodense sign did not occur in any of the patients with viral or bacterial pneumonia, in the control series. We consider the hypodense sign to be a supplementary tool in the diagnosis of IPA. Its sensitivity was low in our series, but the high specificity makes it valuable in predicting IPA, anticipating the occurrence of cavitation or crescent sign, which are considered specific, but late findings of IPA. The hypodense sign is recognizable also on unenhanced CT, when a narrower lung window setting is used.

Pulmonary Candidiasis after Hematopoietic Stem Cell Transplantation: Thin-Section CT Findings

PURPOSE

To retrospectively evaluate thin-section computed tomographic (CT) findings in hematopoietic stem cell transplant (ie, bone marrow transplant) patients with histopathologically proved pulmonary candidiasis.

MATERIALS AND METHODS

Ethical approval was obtained from the institutional review board of each of the three institutions; informed consent was not required. The study included 17 hematopoietic stem cell transplant recipients with proved pulmonary candidiasis. Histopathologic specimens were acquired at transbronchial biopsy (n = 8), open lung biopsy (n = 6), and autopsy (n = 3). The patients included seven men and 10 women (age range, 20-62 years; mean age, 37 years). The thin-section CT scans were retrospectively reviewed by two thoracic radiologists for the presence, appearance, and distribution of parenchymal abnormalities.

RESULTS

Multiple nodules were present in 15 (88%) patients, including centrilobular nodules and tree-in-bud pattern in seven (41%) patients. Nodules were bilateral in 12 patients and unilateral in three. An associated halo of ground-glass opacity was identified in five (33%) patients. Nodules were the only CT finding in five patients (29%). Areas of air-space consolidation were identified in 11 (65%) patients. Areas of ground-glass opacity were seen in six (35%) of 17 patients and were always associated with other abnormalities. Other less common CT findings included pleural effusion (n = 3), thickening of the bronchial walls (n = 2), and cavitation (n = 1).

CONCLUSION

The most common thin-section CT findings of pulmonary candidiasis in hematopoietic stem cell transplant patients are multiple bilateral nodular opacities often associated with areas of consolidation.

Chest Computed Tomography of Late Invasive Aspergillosis after Allogeneic Hematopoietic Stem Cell Transplantation

Computed tomography (CT) is a powerful diagnostic tool for invasive aspergillosis (IA) after allogeneic stem cell transplantation (allo-SCT); however, little information is available concerning CT findings of late IA after allo-SCT. To characterize CT findings of late IA, we retrospectively examined medical records and high-resolution CT findings of 27 allo-SCT recipients with late IA. Either acute or chronic GVHD was diagnosed in 24 patients. All 27 patients were given corticosteroids at IA diagnosis. High-resolution CT findings included halo (n=12), centrilobular nodules (n=12), ill-defined consolidation (n=13), ground-glass attenuation (n=8), pleural effusion (n=7), pleural-based consolidation (n=4), and cavitation (n=4). CT findings showing centrilobular nodules and either halo or cavitation were classified into bronchopneumonia type and angioinvasive type, respectively. Angioinvasive-type, bronchopneumonia-type, and combination-type IA were diagnosed in 11, 8, and 4 patients, respectively. CT findings were nonspecific in the other 4 patients. One bronchopneumonia-type case and 2 angioinvasive-type IA cases were subsequently diagnosed as combination type. Although there were no significant differences in patient characteristics between the 2 types of IA, bronchopneumonia-type IA had a poorer prognosis than angioinvasive IA ( P=.022). Halo is a useful diagnostic marker in late IA as well as early IA, and late IA frequently manifests as bronchopneumonia.

Direct detection of angioinvasive pulmonary aspergillosis in immunosuppressed patients: preliminary results with high-resolution 16-MDCT angiography

OBJECTIVE

The aim of this study was to optimize detection of angioinvasive pulmonary aspergillosis by showing direct vessel involvement at a peripheral level with high-resolution MDCT angiography in patients with antibiotic-resistant fever of unknown origin under immunosuppression. Twelve CT angiographic examinations were prospectively performed in 10 patients with an optimized CT angiography protocol with 16-MDCT after IV administration of contrast agent using care bolus (Siemens Medical Solutions). Axial images and maximum intensity projections were evaluated for vascular occlusion by an experienced radiologist blinded to the clinical histories. Results were correlated with histology and clinical follow-up data including follow-up CT. Fourteen focal pulmonary lesions were detected by CT in eight patients. Eight of 14 lesions were confirmed by histology. In the remaining six lesions, diagnosis was made by clinical and CT follow-up. In nine of nine lesions in which angioinvasive infection was excluded, CT angiography showed patent vessels. In four of five lesions with histologically proven fungal angioinvasion, vascular occlusion was detected on CT angiography.

CONCLUSION

High-resolution MDCT angiography has been shown to be a feasible technique to depict directly vessel occlusion in the setting of suspected fungal infections, especially for early diagnosis of angioinvasive pulmonary aspergillosis in immunosuppressed patients.

The CT halo: a new sign in active pulmonary sarcoidosis

A case of pulmonary sarcoidosis is presented characterized by multiple coalescent nodules and peripheral ground glass halos, which were fully reversible under repeat systemic glucocorticoid treatment. The differential diagnostic aspects of the pulmonary CT halo sign and its potential for indicating active reversible disease in patients with sarcoidosis is discussed.

Imagerie moderne des pneumonies infectieuses aiguës

Les pneumonies infectieuses aiguës constituent un problème de santé publique important, car elles sont une cause majeure de morbidité et de mortalité chez l’adulte. Si les données cliniques et radiographiques permettent le plus souvent de faire le diagnostic de pneumonie infectieuse, le diagnostic étiologique est plus difficile. En effet, de nombreux agents pathogènes peuvent être responsables de pneumonie et la réaction du parenchyme pulmonaire est peu variée, d’où la faible spécificité des lésions radiologiques observées en dehors de quelques cas particuliers. C’est pourquoi la compréhension des mécanismes physiopathologiques permet d’expliquer certains aspects radiologiques. De même, la connaissance des bases anatomocliniques et radiologiques autorise la reconnaissance de trois aspects radiographiques principaux. Quant à l’appréciation des contextes épidémiologique et immunitaire, ils peuvent permettre également d’approcher le germe en cause.

[High-resolution computed tomography (HRCT) of the pediatric lung]

High-resolution computed tomography (HRCT) of the lung is a very valuable method in the evaluation of children with acute and chronic lung disease due to the high spatial resolution and precise display of anatomy and pathology without superposition. The following publication will describe an optimized HRCT technique in order to reduce dose, explain various HRCT pattern and explain typical pediatric lung diseases.

Aspergillus in the lung: diverse and coincident forms

Pulmonary disease caused by the fungus Aspergillus has traditionally been regarded as belonging to one of the following, apparently distinct, entities: saprophytic aspergilloma; allergic bronchopulmonary aspergillosis (ABPA); and invasive aspergillosis (IPA); which may be further categorised as angioinvasive, acute or chronic airway invasive) [1]. It is not always obvious that there is overlap between these entities, and that in any given patient more than one Aspergillus-related pathological process can co-exist [2]. The aim of this article is to review the clinical and imaging features of the main categories of Aspergillus-related pulmonary disease and, in particular, to highlight the overlap between them.

The value of the chest computed tomography halo sign in the diagnosis of invasive pulmonary aspergillosis. An autopsy-based retrospective study of 48 patients

To evaluate the diagnostic value of a halo on computed tomography (CT) in the diagnosis of invasive pulmonary aspergillosis (IPA), we retrospectively reviewed chest CT scans and autopsy reports for patients who had been admitted to our hospitals for the treatment of hematological malignancy. Pulmonary complications were suspected in all patients and chest CT scans were taken within a month of death. We examined the association between autopsy and CT findings in 48 patients who were diagnosed as IPA (n = 17), candidosis (n = 4), zygomycosis (n = 2), infiltration of hematological malignancy (n = 12), bacterial pneumonia (n = 6), cytomegalovirus pneumonia (n = 2), pulmonary hemorrhage (n = 2), or pulmonary congestion (n = 1). Patients with IPA showed a variety of CT findings, including halo (n = 13), nodules (n = 14), granular shadows (n = 3), masses (n = 6), consolidations (n = 9), wedge-shaped consolidations (n = 1), and cavitation (n = 2). In contrast, 0, 11 and two of the 31 patients without IPA showed halo, nodules and masses, respectively. These signs were more frequently observed in IPA patients than in non-IPA patients. The CT halo, especially, seemed to be specific for IPA in hospitalized neutropenic patients with hematological malignancies who developed antibiotic-resistant fever. For CT findings other than these three signs, there were no significant differences between IPA- and non-IPA patients.

The radiologic spectrum of pulmonary Aspergillus infections

Aspergillus infections may be categorized by specific radiographic patterns, the patient's immunologic status, and the presence or absence of preexisting structural lung disease. General patterns include invasive aspergillosis (both vascular and airway invasive varieties and acute tracheobronchitis), semiinvasive aspergillosis (including allergic bronchopulmonary aspergillosis and hypersensitivity pneumonitis), mycetoma, allergic aspergillosis, and obstructing bronchial aspergillosis. Knowledge of these various radiographic patterns as well as the immune derangements that accompany these infections may allow proper diagnosis.

Role of early diagnosis and aggressive surgery in the management of invasive pulmonary aspergillosis in neutropenic patients

Invasive pulmonary aspergillosis (IPA) occurs mostly in immunocompromised hosts and especially in neutropenic patients. Improved prognosis for IPA requires early diagnosis. We report our experience in the management of IPA in patients with hematological malignancies. In prolonged neutropenia (> 10 days), thoracic CT scanning seems to be the best choice for the diagnosis of IPA (with CT halo or air-crescent signs). Its systematic use allows a dramatic reduction in the time to achieve the diagnosis, if there is evidence of a halo sign. The systematic screening for the detection of Aspergillus antigenemia with an ELISA test is helpful for early diagnosis. The detection of Aspergillus antigen (with the less sensitive latex agglutination test) on bronchoalveolar lavage (BAL) fluid may also be as useful. The treatment of IPA relies on amphotericin B (or its lipid formulations) or on azole antifungal agents. Pulmonary surgical resection should be considered either as an emergency procedure (despite persistent neutropenia) to avoid massive hemoptysis, or as an elective or diagnostic procedure. This global strategy for the management of IPA is associated with a 75-80% success rate in hematological patients. Nevertheless, the control of underlying malignancy remains a major prognostic factor.

Antifungal efficacy of caspofungin (MK-0991) in experimental pulmonary aspergillosis in persistently neutropenic rabbits: pharmacokinetics, drug disposition, and relationship to galactomannan antigenemia

The antifungal efficacy, pharmacokinetics, and safety of caspofungin (CAS) were investigated in the treatment and prophylaxis of invasive pulmonary aspergillosis due to Aspergillus fumigatus in persistently neutropenic rabbits. Antifungal therapy consisted of 1, 3, or 6 mg of CAS/kg of body weight/day (CAS1, CAS3, and CAS6, respectively) or 1 mg of deoxycholate amphotericin B (AMB)/kg/day intravenously for 12 days starting 24 h after endotracheal inoculation. Prophylaxis (CAS1) was initiated 4 days before endotracheal inoculation. Rabbits treated with CAS had significant improvement in survival and reduction in organism-mediated pulmonary injury (OMPI) measured by pulmonary infarct score and total lung weight (P < 0.01). However, animals treated with CAS demonstrated a paradoxical trend toward increased residual fungal burden (log CFU per gram) and increased serum galactomannan antigen index (GMI) despite improved survival. Rabbits receiving prophylactic CAS1 also showed significant improvement in survival and reduction in OMPI (P < 0.01), but there was no effect on residual fungal burden. In vitro tetrazolium salt hyphal damage assays and histologic studies demonstrated that CAS had concentration- and dose-dependent effects on hyphal structural integrity. In parallel with a decline in GMI, AMB significantly reduced the pulmonary tissue burden of A. fumigatus (P < or = 0.01). The CAS1, CAS3, and CAS6 dose regimens demonstrated dose-proportional exposure and maintained drug levels in plasma above the MIC for the entire 24-h dosing interval at doses that were > or =3 mg/kg/day. As serial galactomannan antigen levels may be used for therapeutic monitoring, one should be aware that profoundly neutropenic patients receiving echinocandins for aspergillosis might have persistent galactomannan antigenemia despite clinical improvement. CAS improved survival, reduced pulmonary injury, and caused dose-dependent hyphal damage but with no reduction in residual fungal burden or galactomannan antigenemia in persistently neutropenic rabbits with invasive pulmonary aspergillosis.

Radiology of pneumonia

Infection of the lower respiratory tract, acquired by way of the airways and confined to the lung parenchyma and airways, typically presents radiologically as one of three patterns: (1) focal nonsegmental or lobar pneumonia, (2) multifocal bronchopneumonia or lobular pneumonia, and (3) focal or diffuse "interstitial" pneumonia. These patterns can be useful in identifying the etiological organism in the appropriate clinical setting. To serve the purpose of this article, these patterns are used as the primary method of classification of pulmonary infections caused by different organisms. Mycobacterial and fungal pulmonary infections are reviewed separately because of their wide range of radiographic appearance that depend on the stage of the disease at presentation. This article discusses the clinical and radiographic features of the most common causes of pneumonia, primarily in the adult population of the United States.

Use of first line bronchoalveolar lavage in the immunosuppressed oncology patient

Immunosuppressed oncology patients who develop pulmonary infiltrates during treatment have a mortality rate of the order of 55-90%. Early diagnosis and treatment is associated with increased survival. At present, diagnosis relies on invasive sampling of the respiratory tract using fibre-optic bronchoscopy. We have looked at a 30-month period, from June 1997 to December 1999, where 25 bronchoscopies were performed on patients from the Lymphoma and BMT units at The Royal Marsden Hospital for the further investigation of pulmonary infiltrates. Nine bronchoscopies (36%) yielded a positive result and seven (28%) led to a change in management. Analysis of the data showed that neither a positive result nor a change in management had any impact on overall survival. After reviewing the background literature on the investigation of pulmonary infiltrates in this group and discussion of the respective merits and limitations, we propose a management flowchart, with high-resolution computed tomography (HRCT) as the test arm in a future randomised trial of these patients.

Antifungal activity and pharmacokinetics of posaconazole (SCH 56592) in treatment and prevention of experimental invasive pulmonary aspergillosis: correlation with galactomannan antigenemia

The antifungal efficacy, safety, and pharmacokinetics of posaconazole (SCH 56592) (POC) were investigated in treatment and prophylaxis of primary pulmonary aspergillosis due to Aspergillus fumigatus in persistently neutropenic rabbits. Antifungal therapy consisted of POC at 2, 6, and 20 mg/kg of body weight per os; itraconazole (ITC) at 2, 6, and 20 mg/kg per os; or amphotericin B (AMB) at 1 mg/kg intravenously. Rabbits treated with POC showed a significant improvement in survival and significant reductions in pulmonary infarct scores, total lung weights, numbers of pulmonary CFU per gram, numbers of computerized-tomography-monitored pulmonary lesions, and levels of galactomannan antigenemia. AMB and POC had comparable therapeutic efficacies by all parameters. By comparison, animals treated with ITC had no significant changes in outcome variables in comparison to those of untreated controls (UC). Rabbits receiving prophylactic POC at all dosages showed a significant reduction in infarct scores, total lung weights, and organism clearance from lung tissue in comparison to results for UC (P < 0.01). There was dosage-dependent microbiological clearance of A. fumigatus from lung tissue in response to POC. Serum creatinine levels were greater (P < 0.01) in AMB-treated animals than in UC and POC- or ITC-treated rabbits. There was no elevation of serum hepatic transaminase levels in POC- or ITC-treated rabbits. The pharmacokinetics of POC and ITC in plasma demonstrated dose dependency after multiple dosing. The 2-, 6-, and 20-mg/kg dosages of POC maintained plasma drug levels above the MICs for the entire 24-h dosing interval. In summary, POC at > or =6 mg/kg/day per os generated sustained concentrations in plasma of > or =1 microg/ml that were as effective in the treatment and prevention of invasive pulmonary aspergillosis as AMB at 1 mg/kg/day and more effective than cyclodextrin ITC at > or =6 mg/kg/day per os in persistently neutropenic rabbits.

Increasing volume and changing characteristics of invasive pulmonary aspergillosis on sequential thoracic computed tomography scans in patients with neutropenia

PURPOSE

In patients with neutropenia, thoracic computed tomography (CT) halo and air-crescent signs are recognized as major indicators of invasive pulmonary aspergillosis (IPA). Nevertheless, the exact timing of CT images is not well known.

PATIENTS AND METHODS

Seventy-one thoracic CT scans were analyzed in 25 patients with neutropenia with surgically proven IPA.

RESULTS

On the first day of IPA diagnosis with early CT scan (d0), a typical CT halo sign was observed in 24 of 25 patients. At that time, the median number of thoracic lesions was two (range, one to six), and pulmonary involvement was bilateral in 12 cases. The halo sign was present in 68%, 22%, and 19% of cases on d3, d7, and d14, respectively. Similarly, the air-crescent sign was seen in 8%, 28%, and 63% of cases on the same days. Otherwise, a nonspecific air-space consolidation aspect was seen in 31%, 50%, and 18% of cases on the same days. The analysis of calculated aspergillary volumes on CT showed that, despite antifungal treatment, the median volume of lesions increased four-fold from d0 to d7, whereas it remained stable from d7 to d14. Overall, 21 patients (84%) were cured by the medical-surgical approach.

CONCLUSION

In patients with neutropenia, CT halo sign is a highly effective modality for IPA diagnosis. The duration of the halo sign is short, and it demonstrates the value of early CT. The increase of the aspergillosis size on CT in the first days after IPA diagnosis is not correlated with a pejorative immediate outcome when using a combined medical-surgical approach.

Resection of invasive pulmonary aspergillosis in immunocompromised patients

BACKGROUND

Immunocompromised patients are prone to develop invasive pulmonary aspergillosis (IPA). Relapse and high mortality rates are seen in those patients who receive subsequent immunotoxic therapy. Standard antifungal regimens often fail to completely eradicate IPA, which then warrants an aggressive surgical approach.

METHODS

We performed a retrospective chart review of 13 immunocompromised patients who were considered to have IPA and who underwent surgery between 1988 and 1998.

RESULTS

Twelve patients had a hematological malignancy and one patient had breast cancer. The diagnosis of IPA was based on a chest computed tomographic scan in all patients. A preoperative diagnosis of aspergillosis was made in three patients, and mucormycosis in one patient, by bronchoalveolar lavage. Before surgery, seven patients received chemotherapy, one patient underwent bone marrow transplantation, and five patients received a combination of chemotherapy and bone marrow transplantation. Symptoms included cough (54%), fever (54%), hemoptysis (30%), and shortness of breath (8%). Three patients (23%) were asymptomatic. The mean preoperative absolute neutrophil count was 4881 cells/microl. Seventeen thoracic operations were performed, i.e., 12 wedge resections, 4 lobectomies, and 1 pneumonectomy. One patient also underwent nephrectomy for invasive aspergillosis and one patient underwent craniotomy to resect an aspergillus brain mass. Surgical pathology revealed IPA in 13 (76%), invasive mucormycosis in 2 (15%), aspergilloma in 1, and diffuse alveolar hemorrhage in 1. Postoperative complications included the following: operative bleeding requiring transfusion, three patients; prolonged air leak, two patients; death because of hepatic/renal failure, one patient; and death because of overwhelming multisystem aspergillosis, one patient. Seven (54%) patients underwent further immunotoxic treatment with no aspergillosis recurrence. After a mean follow-up of 12 months, five (38%) patients are alive and seven (54%) have died without evidence of aspergillosis and/or mucormycosis.

CONCLUSIONS

Surgical resection, in combination with antifungal agents, is a safe and effective form of therapy for invasive mycoses. It prevents recurrence and allows for subsequent cytotoxic therapies.

Radiology of pneumonia

Chest radiography is the imaging technique of choice in evaluating patients with suspected pneumonia because of its low radiation dose, low cost, and wide accessibility. In daily practice, radiographs are used to confirm the clinical diagnosis of pneumonia, characterize the extent and severity of disease, search for complications such as empyema, monitor the response to therapy, and examine for possible alternative or additional diagnoses. Although CT scan has no defined role in the routine assessment of patients with either community-acquired or nosocomial pneumonias, its advantages of superior contrast resolution and cross-sectional display can often be helpful in the analysis of complex cases, particularly when radiographic evidence of associated central obstruction, cavitation, lymphadenopathy, or empyema is equivocal. In the immunocompromised patient population, high-resolution CT has been shown to be more sensitive than plain film radiography in the early detection of pulmonary infections.

Aspergillus fumigatus and aspergillosis

Aspergillus fumigatus is one of the most ubiquitous of the airborne saprophytic fungi. Humans and animals constantly inhale numerous conidia of this fungus. The conidia are normally eliminated in the immunocompetent host by innate immune mechanisms, and aspergilloma and allergic bronchopulmonary aspergillosis, uncommon clinical syndromes, are the only infections observed in such hosts. Thus, A. fumigatus was considered for years to be a weak pathogen. With increases in the number of immunosuppressed patients, however, there has been a dramatic increase in severe and usually fatal invasive aspergillosis, now the most common mold infection worldwide. In this review, the focus is on the biology of A. fumigatus and the diseases it causes. Included are discussions of (i) genomic and molecular characterization of the organism, (ii) clinical and laboratory methods available for the diagnosis of aspergillosis in immunocompetent and immunocompromised hosts, (iii) identification of host and fungal factors that play a role in the establishment of the fungus in vivo, and (iv) problems associated with antifungal therapy.

Invasive aspergillosis in the immunocompromised host: utility of computed tomography and bronchoalveolar lavage

OBJECTIVE

Bronchoalveolar lavage is performed almost routinely in immunocompromised patients with suspected pneumonia, but it has a low yield in the diagnosis of pulmonary aspergillosis. The aim of this study was to determine whether computed tomography (CT) is helpful in determining the likelihood of a positive bronchoalveolar lavage by allowing distinction of patients with angioinvasive aspergillosis from those with Aspergillus bronchopneumonia.

METHODS AND RESULTS

A retrospective study was performed including consecutive immunocompromised patients with suspected pneumonia who underwent CT scanning of the chest and bronchoalveolar lavage and who had definite diagnosis of pulmonary aspergillosis. The CT scans were reviewed by two chest radiologists and classified as showing features consistent with angioinvasive or airway invasive aspergillosis. Twenty-one patients met the inclusion criteria. Bronchoalveolar lavage was positive for fungi in two of 11 patients with CT findings consistent with angioinvasive aspergillosis and eight of 10 patients with CT scans consistent with Aspergillus bronchopneumonia (P < 0.01, chi-squared test). CT findings of angioinvasive aspergillosis included nodules measuring 1-3.5 cm in diameter in six, segmental consolidation in three, and both nodules and segmental consolidation in two patients. CT findings of Aspergillus bronchopneumonia including peribronchial consolidation in five, small centrilobular micronodules in one, and both in four patients.

CONCLUSIONS

Chest CT is helpful in determining the likelihood of successful diagnosis of pulmonary aspergillosis by bronchoalveolar lavage.

Aspergillus infections of the lung: radiological signs

The variety of diseases and courses that may be povoqued by fungi in the lungs is consistent with an equal multitude of radiologically-morphologically visible alterations. Only a few of these radiological signs are characteristic with regard to differential diagnosis of the infection. As long as the pathogen has not been identified, a wide range of differential diagnoses must be considered which can only be restricted by careful overall view with all clinical findings. Nevertheless, detailed analysis of the often indistinct x-ray patterns is imperative in order to contribute to evaluating the course and therapy of aspergilloses.

Preoperative and postoperative imaging in the surgical management of pulmonary emphysema

For patients with emphysema, imaging studies have been useful for diagnostic purposes and for preoperative patient selection for surgical intervention, such as bullectomy, lung transplantation, and LVRS. Chest radiography is useful in evaluating hyperinflation. Inspiratory and expiratory films are used to estimate diaphragmatic excursion and air-trapping. CT scan is used to evaluate the anatomy and distribution of emphysema throughout the lungs, providing information clinically unobtainable by other means. Both imaging techniques are useful for detecting other disease processes. Radionuclide lung scanning also provides an estimate of target areas, volume occupying but nonfunctioning lung. Cohort studies utilizing these imaging techniques have demonstrated associations between preoperative characteristics and postoperative outcome. The imaging studies, especially the chest radiograph, have also played an important role in postoperative management. Many other imaging options are available, such as HRCT scan, quantitative CT scan, and single photon emission CT scan. Other techniques, such as MR imaging, may play a future role as well.

Guidelines for the investigation of invasive fungal infections in haematological malignancy and solid organ transplantation. British Society for Medical Mycology

Invasive fungal infections are increasing in incidence and now affect as many as 50% of neutropenic/bone marrow transplant patients and 5 to 20% of solid organ transplant recipients. Unfortunately, many of the diagnostic tests available have a low sensitivity. The guidelines presented here have been produced by a working party of the British Society for Medical Mycology in an attempt to optimise the use of these tests. The yield of fungi from blood cultures can be increased by ensuring that at least 20 ml of blood are taken for aerobic culture, by using more than one method of blood culture, and by employing terminal subculture if continuous monitoring systems are used with a five-day incubation protocol. Skin lesions in febrile neutropenic patients should be biopsied and cultured for fungi. The detection of galactomannan in blood or urine is of value in diagnosing invasive aspergillosis only if tests are performed at least twice weekly in high-risk patients. Antigen detection tests for invasive candidiasis are less valuable. Computed tomography scanning is particularly valuable in diagnosing invasive pulmonary fungal infection when the chest radiograph is negative or shows only minimal changes. Bronchoalveolar lavage is most useful in patients with diffuse changes on computed tomography scan. The major advances in the diagnosis of invasive fungal infection in patients with haematological malignancy or solid organ transplantation have been in the use of imaging techniques, rather than in the development of new mycological methods in the routine laboratory.

MR of Toxoplasma encephalitis: signal characteristics on T2-weighted images and pathologic correlation

PURPOSE

Our goal was to determine if there are any T2-weighted MR signal characteristics of Toxoplasma encephalitis that might be useful in diagnosis and/or in gauging the effectiveness of medical therapy.

METHOD

We retrospectively analyzed the MR, CT, thallium-201 SPECT brain scans, and medical records of 27 patients with medically proven (26) and biopsy proven (1) Toxoplasma encephalitis, supplemented by autopsy findings in 4 additional patients, 2 of whom had postmortem MR correlation. The neuropathologic literature was also reviewed.

RESULTS

Among the 27 patients, we discovered three distinct imaging patterns. Ten (37%) patients had predominantly T2-weighted hyperintense lesions and had been on medical therapy an average of 3 days (excluding one outlier). Ten (37%) patients had T2-weighted isointense lesions and had received medical therapy an average of 61 days. Seven (26%) patients had lesions with mixed signal on T2-weighted images and had been on treatment an average of 6 days. Analysis of autopsy material from the four additional patients revealed the presence of organizing abscesses in three and necrotizing encephalitis in one, while the patient who had a brain biopsy demonstrated both types of pathologic lesions. In both cases having postmortem MRI, organizing abscesses appeared isointense to hypointense on T2-weighted images.

CONCLUSION

There is a definite variation in the appearance of lesions of Toxoplasma encephalitis on T2-weighted images that precludes a definitive diagnosis based on signal characteristics alone. Pathologically, our data suggest that T2-weighted hyperintensity correlates with necrotizing encephalitis and T2-weighted isointensity with organizing abscesses. Furthermore, in patients on medical therapy the T2-weighted MR appearance may be a transition from hyperintensity to isointensity as a function of a positive response to antibiotic treatment, indicating that the signal change might be used to gauge the effectiveness of medical therapy.

Hospital-acquired candida and aspergillus pneumonia--diagnostic approaches and clinical findings

Bronchoscopy with bronchoalveolar lavage (BAL), collection of bronchial secretions (BS) and/or high resolution computed tomography (CT) of the lungs was performed in 70 patients with candida and/or aspergillus pneumonia. The sensitivity of bronchoscopy in detecting histologically proven fungal disease was 59%. Characteristic CT signs were found in 11 of 14 patients with candida pneumonia and 16 of 19 patients with aspergillosis. The more frequent use of bronchoscopy and CT scans between 1990 and 1992 compared with 1986-1989 for the differential diagnosis of new pulmonary infiltrates in immunocompromised patients resulted in earlier antifungal treatment (14 vs. nine days; P < 0 center dot 025). In the second treatment period survival was improved from 36 to 50% (not significant). Bronchoscopy and high resolution CT scans are mutually complementary diagnostic tools and should be performed as early as possible in the course of pneumonia in patients at high risk of fungal diseases.