Low-dose and conventional-dose high resolution CT of pulmonary changes in breast cancer patients treated by tangential field radiotherapy

Validation of a model for predicting smear-positive active pulmonary tuberculosis in patients with initial acid-fast bacilli smear-negative sputum

OBJECTIVES

The objective of this study was to develop a predictive model for final smear-positive (SP) active pulmonary tuberculosis (aPTB) in patients with initial negative acid fast bacilli (AFB) sputum smears (iSN-SP-aPTB) based on high-resolution computed tomography (HRCT).

METHOD AND MATERIALS

Eighty (126, 21) patients of iSN-SP-aPTB and 402 (459, 876) patients of non-initial positive acid fast bacilli (non-iSP) pulmonary disease without iSN-SP-aPTB were included in a derivation (validation, prospective) cohort. HRCT characteristics were analysed, and multivariable regression and receiver operating characteristic (ROC) curve analysis was performed to develop a score predictive of iSN-SP-aPTB.

RESULTS

The derivation cohort showed clusters of nodules/mass of the right upper lobe or left upper lobe were independent predictors of iSN-SP-aPTB, while bronchiectasis in the right middle lobe or left lingual lobe were negatively associated with iSN-SP-aPTB. A predictive score for iSN-SP-aPTB based on these findings was tested in the validation and prospective cohorts. With an ideal cut-off score = 1, the sensitivity, specificity, positive predictive value, and negative predictive value of the prediction model were 87.5% (90%, 90.5%), 99% (97.1%, 98.4%), 94.6% (81.3%, 57.5%), and 97.6% (97%, 99.8%) in the derivation (validation, prospective) cohorts, respectively.

CONCLUSIONS

The model may help identify iSN-SP-aPTB among patients with non-iSP pulmonary diseases.

KEY POINTS

• Smear-positive active pulmonary tuberculosis that is initial smear-negative (iSN-SP-aPTB) is infectious. • High-resolution computed tomography can identify iSN-SP-aPTB among non-iSP pulmonary diseases. • Clusters nodules/mass in right/left upper lobe are positively associated with iSN-SP-aPTB. • Bronchiectasis in right middle/left lingual lobe is negatively associated with iSN-SP-aPTB. • The model may have high post-test probability in identifying iSN-SP-aPTB.

Image-guided radiation therapy using computed tomography in radiotherapy

The sharp dose gradients in intensity-modulated radiation therapy increase the treatment sensitivity to various inter- and intra-fractional uncertainties, in which a slight anatomical change may greatly alter the actual dose delivered. Image-guided radiotherapy refers to the use of advanced imaging techniques to precisely track and correct these patient-specific variations in routine treatment. It can also monitor organ changes during a radiotherapy course. Currently, image-guided radiotherapy using computed tomography has gained much popularity in radiotherapy verification as it provides volumetric images with soft-tissue contrast for on-line tracking of tumour. This article reviews four types of computed tomography-based image guidance systems and their working principles. The system characteristics and clinical applications of the helical, megavoltage, computed tomography, and kilovoltage, cone-beam, computed tomography systems are discussed, given that they are currently the most commonly used systems for radiotherapy verification. This article also focuses on the recent techniques of soft-tissue contrast enhancement, digital tomosynthesis, four-dimensional fluoroscopic image guidance, and kilovoltage/megavoltage, in-line cone-beam imaging. These evolving systems are expected to take over the conventional two-dimensional verification system in the near future and provide the basis for implementing adaptive radiotherapy.

Low dose multi-detector CT of the chest (iLEAD Study): visual ranking of different simulated mAs levels

PURPOSE

Detailed evaluation of the lung parenchyma might be impaired by use of low dose CT as image noise increases and subsequently image quality decreases. The aim of our study was to determine the accuracy of visual perception of differences in image quality and noise at low dose chest CT.

MATERIALS AND METHODS

Forty-four patients suffering from emphysema underwent CT (Aquilion-16, 120kV, 150mAs, 1mm-collimation). Original raw data were used for simulation of 10 different mAs settings from 10mAs to 100mAs in 10mAs increments. Three representative hard copy images (carina, 4cm above, 5cm below) were printed for evaluation of lung parenchyma (high-resolution kernel, lung window) and mediastinum (soft-kernel, soft tissue window). Ranking of expected low mAs level was performed for lung and soft tissue separately based on visual perception by three-blinded chest radiologist independently. Results were compared to the real simulated mAs.

RESULTS

The accuracy for correct ranking of the original 150mAs scan was 89% for lung and 86% for soft tissue while it was 99% for the simulated 10mAs for both windows. In comparison to the lowest mAs a significant error increase was found for the lung at 60-100mAs (with error increase of 30-47%) for reader-I; 60-100mAs for (33-64%) for reader-II and 70-100mAs (38-57%) for reader-III. For the soft tissue: 60-150mAs (with error increase of 28-63%) for reader-I; 50-100mAs (35-56%) for reader-II and 50-90mAs (35-40%) for reader-III.

CONCLUSION

Simulated dose levels below 60mAs (=42mAs(eff)) were clearly differentiated from higher dose levels by all readers. Therefore, imaging doses could be lowered down to 60mAs without a diagnostically relevant increase in noise impairing image quality.

Radiological pulmonary findings after breast cancer irradiation: A prospective study

The aim of this study was to evaluate radiation-induced pulmonary abnormalities of breast cancer patients. Altogether 202 consecutive patients receiving postoperative radiotherapy entered the study. Plain chest radiographs taken at entry and 3, 6 and 12 months after radiotherapy were evaluated according to modified Arriagada classification. In addition, pulmonary symptoms were recorded. Supplementary high-resolution computed tomography (HRCT) was employed in a subgroup of patients (n?=?15). Plain radiographs were interpreted by a radiologist, and uncertain findings were re-evaluated by a radiologist together with a radiation oncologist. Grade 2 pneumonitis was the most common abnormality. The proportion of patients yielding a grade 2 finding was 22.5%, 28.1%, and 16.0% at three, six, and twelve months, respectively. There were 2 normal findings in HRCTscans, and 8 in plain radiographs of the same patients. Radiological lung abnormalities are common after radiotherapy, but they are usually reversible, and their significance for the patient's well-being is minor. No correlation between symptoms and lung or pleural reactions was seen.

Whole-body low-dose multidetector row-CT in the diagnosis of multiple myeloma: an alternative to conventional radiography

OBJECTIVE

The goal of this study was to establish the feasibility of a low-dose whole-body multidetector row-CT (MDCT) protocol in the diagnosis of multiple myeloma (MM), as an alternative to conventional X-ray imaging, which is currently still state-of-the-art in these patients, with emphasis on the comparison of image resolution on axial and multiplanar reformatted (MPR) scans and reduction of radiation dose.

MATERIAL AND METHODS

100 patients with known MM, or monoclonal gammopathy of unknown significance (MGUS) underwent unenhanced whole-body MDCT on a 16-slice scanner in a randomised fashion, using a 16 x 1.5 mm collimation and four different energy parameters (40, 50, 60 and 70 mAs). Three different reconstruction algorithms were used in every patient (B40f, B50f and B60f kernel). CT scans were reviewed independently by two radiologists, with regard to correct classification into one of the three known MM stages, and recognition of fracture risk. Thereafter, axial and MPR images were evaluated in consensus by both readers, with respect to image resolution. Diagnosis of osteolytic lesions was performed on the basis of axial and multiplanar reformatted images, whereas the assessment of spinal misalignment and fracture was done only on MPR images. The distribution of image resolution categories (very good, good, sufficient, insufficient for diagnosis) was evaluated depending on following parameters: current time product, patient's weight, bone density and reconstruction algorithm. The effective radiation dose was determined with the aid of an anthropomorphic Alderson Rando-Phantom, using a tube current time product of 40 mAs, and then extrapolating it on all current time products applied in this study on a commercially available software program WinDose (Institute of Medical Physics, Erlangen, Germany).

RESULTS

In all 100 patients, image resolution was diagnostic, regardless of scanning parameters, enabling correct classification of multiple myeloma patients. Image quality of MPR images was either equal or inferior to correspondent axial images in the delineation of smaller lytic lesions, because of the use of non-isotropic voxel size. However, they proved accurate in diagnosing fracture and spine misalignment. A strong dependency of image resolution on bone density was observed, with reduced quality in patients with either diffuse skeleton infiltration or concurrent osteoporosis. Spatial resolution was also dependent on the reconstruction algorithm and energy level (mAs) used, as well as on patient's weight, but their influence was low within the given ranges. A middle-frequency reconstruction algorithm (B50f kernel) proved beneficial for all energy protocols. The interobserver agreement was excellent (kappa = 0.95) for classification of MM-patients. Effective radiation dose of MDCT calculated at a tube current time product of 40 mAs was 1.7-fold higher than the mean radiation dose of conventional X-ray (4.1 mSv versus 2.4 mSv).

DISCUSSION

Our study shows that whole-body low-dose MDCT investigational protocols are appropriate for the diagnosis of lytic bone changes and for assessment of fracture risk in multiple myeloma patients, representing a serious alternative to current standards.

Low-dose MDCT and virtual bronchoscopy in pediatric patients with foreign body aspiration

OBJECTIVE

The purpose of this study was to investigate the potential use of low-tube-current MDCT virtual bronchoscopy for the evaluation of children with suspected foreign body aspiration.

SUBJECTS AND METHODS

Low-tube-current MDCT was performed in 23 patients (10 girls, 13 boys) with a mean age of 3.3 years (9 months-13 years) with suspicion of foreign body aspiration. Chest radiographs were obtained before CT was performed. MDCT was performed using 25- to 50-mA tube currents. MDCT virtual bronchoscopy images were obtained. Neither sedation nor IV contrast medium was used during CT scanning. All patients underwent endoscopic evaluation within 24 hr after MDCT was performed. MDCT virtual bronchoscopy findings were retrospectively compared with the results of rigid bronchoscopy.

RESULTS

The mean tube current was 35 mA (range, 25-50 mA). Imaging quality was excellent in nine studies (39%), good in 12 studies (52%), and poor in two studies (9%). Motion artifacts were present on several slices in five examinations. In 15 patients, all foreign bodies detected by conventional bronchoscopy were also revealed on MDCT virtual bronchoscopy. The foreign body was in the right main bronchus in six patients, in the bronchus intermedius in one patient, and in the left main bronchus in eight patients. No discordance was found between the two techniques. MDCT revealed hyperaeration of the ipsilateral lung in five patients, atelectasis in five patients, infiltration in three patients, and infiltration and bronchiectasis in two patients; it showed infiltration in four patients and atelectasis in one of eight patients without a foreign body detected. There were no abnormal findings in three patients.

CONCLUSION

Evaluation of foreign body aspiration of the airway in children can be accomplished by using a low-tube-current MDCT protocol. It may be useful both in showing the exact location of a foreign body before bronchoscopy and in ruling out a foreign body in patients with a low level of suspicion and normal or nonspecific findings on chest radiography.

Diagnostic Imaging of Diffuse Infiltrative Disease of the Lung

Plain chest radiography remains the first diagnostic approach to diffuse infiltrative lung disease but has limited diagnostic sensitivity and specificity. Many diseases remain occult or are not correctly assessed using chest X-ray, appearing as a nonspecific 'reticulonodular pattern'. High-resolution CT (HRCT) is actually the recommended imaging technique in the diagnosis, assessment, and follow-up of these diseases, allowing also the evaluation of the effectiveness of the medical therapy and the selection of the type and the location of the biopsy when required. Appropriate techniques must be used to acquire high-quality HRCT scans, with the thin collimation and high spatial reconstruction algorithm being the most important factors. A nodular pattern, linear and reticular opacities, cystic lesions, ground-glass opacities and consolidations are the most common HRCT patterns of diffuse infiltrative lung disease. This article reviews the role of chest radiography and HRCT in the diagnosis and assessment of these diseases, the technical aspects of HRCT, its clinical indications and the radiological pattern of the most common types of chronic diffuse infiltrative lung disease.

Low-dose spiral CT: application to surface-rendered three-dimensional imaging of central airways

PURPOSE

The purpose of this work was to assess the utility of low-dose spiral CT for three-dimensional imaging of the central airways.

METHOD

Spiral CT was performed in 15 patients using two tube currents (50 and 240 mA), producing 30 CT data sets. Surface-rendered virtual bronchoscopy (VB) and shaded surface display (SSD) images were assessed by three radiologists for image quality. The radiologists were also asked to compare 15 matched pairs each of 50 and 240 mA VB and SSD images, blindly select the 240 mA image, and record differences in diagnostic quality between the matched images.

RESULTS

No significant difference in image quality was noted with 50 or 240 mA. Only 51.1% of 240 mA SSD and 51.1% of 240 mA VB images were correctly identified. Differences in diagnostic quality, noted in 84.4% of SSD and 33% of VB image pairs, were not ascribed to image noise.

CONCLUSION

Image quality of surface-rendered three-dimensional images of the central airways is preserved using a lower tube current.

Pulmonary sequelae of treatment for breast cancer: a prospective study

PURPOSE

To prospectively study the effects of loco-regional radiotherapy in women with breast cancer.

METHODS AND MATERIALS

Thirty consecutive patients with breast resection underwent clinical, lung function, radiographic, and thoracic high-resolution computed tomography evaluation before and at 1, 3, 6, and 12 months after adjuvant radiotherapy. Chemotherapy was also administered to 15 patients.

RESULTS

Nineteen patients reported mild respiratory symptoms at 1 month, which resolved completely at 6 months after radiotherapy. Opacities were present on 80% of chest radiographs and in all patients on high-resolution computed tomography by 3 months. These opacities became compact and persisted on high-resolution computed tomography at 12 months. Lung function indices, including FEV1, FVC, TLC, and DLCO, progressively declined after radiotherapy, and was irreversible at 12 months (p < 0.05). Patients who received chemotherapy did not have significantly different lung function indices compared with their counterparts at all time points (p > 0.05).

CONCLUSIONS

Our results have shown that adjuvant loco-regional radiotherapy, a common practice in breast cancer treatment, is associated with irreversible reduction in lung function parameters. These changes are accompanied by radiological evidence of persistent lung injury. Further studies should be performed to evaluate the incidence and long-term pulmonary sequelae of current treatment for breast cancer.

Serial HRCT lung changes after 3-field radiation treatment of breast cancer

AIMS

To document serial high resolution computed tomography (HRCT) features of lung injury after 3-field radiotherapy for breast cancer.

MATERIALS AND METHODS

Thirty women who received opposing tangential chest wall and supraclavicular field (SCF) irradiation after breast surgery were recruited. Thoracic HRCT was performed before and at 1, 3, 6 and 12 months after radiotherapy (RT). Lung injury at 3 months was quantified by applying a scoring system to each HRCT section. Findings were correlated with spirometric lung function tests.

RESULTS

There was HRCT evidence of lung injury in 27 (90%) women at 1 month and in all 30 patients at 3 months. Spirometric lung function declined post-RT (P < 0.05), correlating with an increased SCF acute lung injury score at 3 months [r = -0.54 and -0.46, P = 0.01 and 0.03 for forced expiratory volume in 1st (FEV(1)) and forced vital capacity (FVC), respectively]. Lung injury on HRCT progressed from ground glass opacification at 1 month to nodular consolidation (3 months), increasing linear densities (6 months), and finally to residual subpleural linear and dense opacities (12 months).

CONCLUSION

There is a high incidence of lung injury associated with 3-field radiotherapy for breast cancer, with concurrent SCF irradiation increasing the risk of lung damage and functional impairment. A characteristic sequence of HRCT changes is seen in most patients receiving this type of radiotherapy.Ooi, G. C. (2000). Clinical Radiology55, 817-824.