Inadequacy of manual measurements compared to automated CT volumetry in assessment of treatment response of pulmonary metastases using RECIST criteria

The purpose of this study was to compare relative values of manual unidimensional measurements (MD) and automated volumetry (AV) for longitudinal treatment response assessment in patients with pulmonary metastases. Fifty consecutive patients with pulmonary metastases and repeat chest multidetector-row CT (median interval=2 months) were independently assessed by two radiologists for treatment response using Response Evaluation Criteria In Solid Tumours (RECIST). Statistics included relative measurement errors (RME), intra-/interobserver correlations, limits of agreement (95% LoA), and kappa. A total of 202 metastases (median volume=182.22 mm³; range=3.16–5,195.13 mm³) were evaluated. RMEs were significantly higher for MD than for AV (intraobserver RME=2.34–3.73% and 0.15–0.22% for MD and AV respectively; P<0.05. Interobserver RME=3.53–3.76% and 0.22–0.29% for MD and AV respectively; P<0.05). Overall correlation was significantly better for AV than for MD (P<0.05). Intraobserver 95% LoAs were −1.85 to 1.75 mm for MD and −11.28 to 9.84 mm³ for AV. The interobserver 95% LoA were −1.46 to 1.92 mm for MD and −11.17 to 9.33 mm³ for AV. There was total intra-/interobserver agreement on response using AV (κ=1). MD intra- and interobserver agreements were 0.73–0.84 and 0.77–0.80 respectively. Of the 200 MD response ratings, 28 (14/50 patients) were discordant. Agreement using MD dropped significantly from total remission to progressive disease (P<0.05). We therefore conclude that AV allows for better reproducibility of response evaluation in pulmonary metastases and should be preferred to MD in these patients.     

Observer variation in FDG PET-CT for staging of non-small-cell lung carcinoma

Purpose  Error and variation in reporting remains one of the weakest features of clinical imaging despite enormous technological advances in nuclear medicine and radiology. The aim of this study was to evaluate agreement amongst experienced readers in staging non-small-cell lung cancer (NSCLC) with PET-CT. Methods  A series of ¹⁸F-FDG PET-CT scans from 100 consecutive patients were reviewed independently by three experienced readers, with two readers reviewing each scan series a second time. Individual mediastinal lymph node stations were assessed as benign/inflammatory, equivocal or malignant, and AJCC N and M stage were also assigned. Kappa (κ) was used to compare ratings from two categories and weighted kappa (κ_w) for three or more categories, and kappa values were interpreted according to the Landis-Koch benchmarks. Results  Both intra- and interobserver agreement for N and M staging were high. For M staging there was almost perfect intra- and interobserver agreement (κ = 0.90–0.93). For N staging, agreement was either almost perfect or substantial (intraobserver κ_w = 0.79, 0.91; interobserver κ_w = 0.75–0.81). Importantly, there was almost perfect agreement for N0/1 vs N2/3 disease (κ = 0.80–0.97). Agreement for inferior and superior mediastinal nodes (stations 1, 2, 3, 7, 8, 9) was either almost perfect or substantial (κ_w = 0.71–0.88), but lower for hilar nodes (10; κ_w = 0.56–0.71). Interreporter variability was greatest for aortopulmonary nodes (5, 6; κ_w = 0.48–0.55). Conclusion  Amongst experienced reporters in a single centre, there was a very high level of agreement for both mediastinal nodal stage and detection of distant metastases with PET-CT. This supports the use of PET-CT as a robust imaging modality for staging NSCLC.     

Computer-assisted detection of pulmonary embolism: performance evaluation in consensus with experienced and inexperienced chest radiologists

The value of a computer-aided detection tool (CAD) as second reader in combination with experienced and inexperienced radiologists for the diagnosis of acute pulmonary embolism (PE) was assessed prospectively. Computed tomographic angiography (CTA) scans (64 × 0.6 mm collimation; 61.4 mm/rot table feed) of 56 patients (31 women, 34–89 years, mean = 66 years) with suspected PE were analysed by two experienced (R1, R2) and two inexperienced (R3, R4) radiologists for the presence and distribution of emboli using a five-point confidence rating, and by CAD. Informed consent was obtained from all patients. Results were compared with an independent reference standard. Inter-observer agreement was calculated by kappa, confidence assessed by ROC analysis. A total of 1,116 emboli [within mediastinal (n = 72), lobar (n = 133), segmental (n = 465) and subsegmental arteries (n = 455)] were included. CAD detected 343 emboli (sensitivity = 30.74%, correct-positive rate = 6.13/patient; false-positive rate = 4.1/patient). Inter-observer agreement was good (R1, R2: κ = 0.84, 95% CI = 0.81–0.87; R3, R4: κ = 0.79, 95% CI = 0.76–0.81). Extended inter-observer agreement was higher in mediastinal and lobar than in segmental and subsegmental arteries (κ = 0.84–0.86 and κ = 0.51–0.58 for mediastinal/lobar and segmental/subsegmental arteries, respectively P < 0.05). Agreement between experienced and inexperienced readers was improved by CAD (κ = 0.60–0.62 and κ = 0.69–0.72 before and after CAD consensus, respectively P < 0.05). The experienced outperformed the inexperienced readers (Az = 0.95, 0.93, 0.89 and 0.86 for R1–4, respectively, P < 0.05). CAD significantly improved overall performances of readers 3 and 4 (Az = 0.86 for R3, R4 and Az = 0.89 for R3, R4 with CAD, P < 0.05), by enhancing sensitivities in segmental/subsegmental arteries. CAD improved experienced readers’ sensitivities in segmental/subsegmental arteries (sens. = 0.93 and 0.90 for R1, R2 before and 0.97 and 0.94 for R1, R2 after CAD consensus, P < 0.05), without significant improvement of their overall performances (P > 0.05). Particularly inexperienced readers benefit from consensus with CAD data, greatly improving detection of segmental and subsegmental emboli. This system is advocated as a second reader.     

Detection of bone metastases in patients with prostate cancer by <Superscript>18</Superscript>F fluorocholine and <Superscript>18</Superscript>F fluoride PET–CT: a comparative study

Purpose  The aim of this prospective study was to compare the potential value of ¹⁸F fluorocholine (FCH) and ¹⁸F fluoride positron emission tomography (PET)–CT scanning for the detection of bony metastases from prostate cancer. Methods  Thirty-eight men (mean age, 69 ± 8 years) with biopsy-proven prostate cancer underwent both imaging modalities within a maximum interval of 2 weeks. Seventeen patients were evaluated preoperatively, and 21 patients were referred for post-operative evaluation of suspected recurrence or progression based on clinical algorithms. The number, sites and morphological patterns of bone lesions on ¹⁸F FCH and ¹⁸F fluoride PET–CT were correlated: Concordant lesions between the two modalities with corresponding changes on CT were considered to be positive for malignancy; discordant lesions were verified by follow-up examinations. The mean follow-up interval was 9.1 months. Results  Overall, 321 lesions were evaluated in this study. In a lesion-based analysis, a relatively close agreement was found between these two imaging modalities for detection of malignant bone lesions (kappa = 0.57), as well as in a patient-based analysis (kappa = 0.76). Sixteen malignant sclerotic lesions with a high density were negative in both ¹⁸F FCH and ¹⁸F fluoride PET–CT [mean Hounsfield unit (HU), 1,148 ± 364]. There was also a significant correlation between tracer intensity by SUV and density of sclerotic lesions by HU both in ¹⁸F FCH PET–CT (r = −0.28, p < 0.006) and ¹⁸F fluoride PET–CT (r = −0.20, p < 0.05). The sensitivity, specificity and accuracy of PET–CT in the detection of bone metastases in prostate cancer was 81%, 93% and 86% for ¹⁸F fluoride, and 74% (p = 0.12), 99% (p = 0.01) and 85% for FCH, respectively. ¹⁸F FCH PET–CT led to a change in the management in two out of 38 patients due to the early detection of bone marrow metastases. ¹⁸F fluoride PET–CT identified more lesions in some patients when compared with ¹⁸F FCH PET–CT but did not change patient management. Conclusion  FCH PET–CT may be superior for the early detection (i.e. bone marrow involvement) of metastatic bone disease. In patients with FCH-negative suspicious sclerotic lesions, a second bone-seeking agent (e.g. ¹⁸F fluoride) is recommended. ¹⁸F fluoride PET–CT demonstrated a higher sensitivity than ¹⁸F FCH PET–CT, but the difference was not statistically significant. Furthermore, ¹⁸F fluoride PET could be also negative in highly dense sclerotic lesions, which presumably reflects the effect of treatment. It will be important to clarify in future studies whether these lesions are clinically relevant when compared with metabolically active bone metastases.     

Transpulmonary chemoembolization (TPCE) as a treatment for unresectable lung metastases

To evaluate tumor response after treating unresectable lung metastases with transpulmonary chemoembolization (TPCE) in palliative intention. From 2001 to 2005, 52 patients (mean: 59.8 years; 32 males/20 females) suffering from 106 unresectable lung metastases (mean:6 metastases/patient; range,1–21) were treated with 2–10 TPCE-sessions (mean: 3.3 sessions/patient). Metastases originated from primaries, including colorectal carcinoma (n = 20), breast cancer (n = 6), renal cellular carcinoma (n = 5), thyroid cancer (n = 4), cholangiocellular carcinoma (n = 2), leiomyosarcoma (n = 2), and others (n = 13). Tumor-feeding pulmonary arteries were selectively probed after puncturing the femoral vein, and administering 10 ml lipiodol, mitomycin C, and microspheres (Spherex) each via balloon catheter over pulmonary approach. During therapy, follow-up was accomplished at 4-week intervals using unenhanced and contrast-enhanced CT. After sequential therapy, follow-up was performed every 3 months for a period of 6 months up to 2.25 years. All patients tolerated the treatments well without major side effects or complications. In 24% (n = 13) moderate to high lipiodol uptake was found, while 75% (n = 39) of the tumors showed a low uptake. According to the RECIST criteria, “partial response” was achieved in 16 cases, “stable disease” in 11 cases, and “progressive disease” in 25 cases [mean survival: 17 months/median: 21.1 months (Kaplan-Meyer)]. According to these findings, TPCE is a well-tolerated procedure for palliative treatment of unresectable lung metastases.     

MR Reproducibility in the Assessment of Uterine Fibroids for Patients Scheduled for Uterine Artery Embolization

Magnetic resonance imaging (MRI) is increasingly applied in the evaluation of uterine fibroids. However, little is known about the reproducibility of MRI in the assessment of uterine fibroids. This study evaluates the inter- and intraobserver variation in the assessment of the uterine fibroids and concomitant adenomyosis in women scheduled for uterine artery embolization (UAE). Forty patients (mean age: 44.5 years) with symptomatic uterine fibroids who were scheduled for UAE underwent T₁- and T₂-weighted MRI. To study inter- and intraobserver agreement 40 MR images were evaluated independently by two observers and reevaluated by both observers 4 months later. Inter- and intraobserver agreement was calculated using Cohen’s κ statistic and intraclass correlation coefficient for categorical and continuous variables, respectively. Inter-observer agreement for uterine volumes (κ = 0.99, p < 0.0001), dominant fibroid volumes (κ = 0.98, p ≤ 0.0001), and number of fibroids (κ = 0.88; CI, 0.77–0.93; p < 0.0001) was excellent. For the T₁- and T₂-weighted signal intensity of the dominant fibroid there was good agreement between the observers (87%; 95% CI, 71.9%–95.6%) and the intraobserver agreement was good for observer A (95%; 95% CI, 83.1%–99.4%) and moderate for observer B (κ = 0.47). The interobserver agreement with respect to the presence of adenomyosis was good (κ = 0.73, p < 0.0001), while both intraobserver agreements were fair to moderate (observer A, κ = 0.55, p = 0.0003; and observer B, κ = 0.66, p < 0.0001). In conclusion, MRI criteria used for the selection of suitable UAE patients show good inter- and intraobserver reproducibility.     

Radiofrequency ablation of lung metastases: factors influencing success

This paper analyses the factors associated with successful radiofrequency ablation (RFA) of lung metastases. The study group comprised 37 patients [19 female, mean age 61 (34–83)] with 72 metastases who had follow-up CT scans available for analysis and for those with no recurrence >6 months follow-up. Internally cooled electrodes were used in 64 and expandable electrodes in 8. The tumour size and location, electrode type, number of ablations, duration of ablation, year of treatment and tumour contact with vessels larger than 3 mm were recorded. The mean tumour diameter was 1.8 cm (0.4–6.6 cm). Mean follow-up in those without recurrence was 13.1 months (6–48). Recurrence was common in larger tumours, occurring in 7/7 (100%) tumours >3.5 cm compared with 18/65 (28%) ≤ 3.5 cm (P < 0.01). Recurrence occurred in 14/24 (58%) tumours in direct contact with large vessels compared with 11/48 (23%) of the remainder (P = 0.04). On multivariate analysis, size was the dominant feature (P = 0.013); vessel contact and peripheral location did not reach significance (P = 0.056 and 0.054 respectively). Peripheral tumours less than 3.5 cm with no large vessel contact are the optimal tumours for RFA.     

Magnetisation transfer imaging adds information to conventional MRIs to differentiate inflammatory from fibrotic components of small intestinal strictures in Crohn’s disease

Identifying inflammation- or fibrosis-predominant strictures in Crohn’s disease (CD) is crucial for treatment strategies. We evaluated the additive value of magnetisation transfer (MT) to conventional MRI for differentiating CD strictures using surgical histopathology as a reference standard. Twenty-eight consecutive CD patients who underwent MRI preoperatively were recruited. MRI parameters included T2-weighted imaging (T2WI) hyperintensity, bowel wall thickness, enhancement pattern changes over time, enhancement pattern and gain ratio in dynamic contrast-enhanced phases, and MT ratio. Correlation analysis was performed using Spearman’s rank test. Receiver operating characteristic curve analysis and Cohen’s κ were used. A model with combined MRI variables characterising intestinal strictures was proposed and validated in 14 additional CD patients. Significant correlations with histological inflammation scores were shown for wall thickness (r = 0.361, p = 0.001) and T2WI hyperintensity (r = 0.396, p < 0.001), whereas histological fibrosis scores were significantly correlated with MT ratio (r = 0.681, p < 0.001) and wall thickness (r = 0.461, p < 0.001). T2WI hyperintensity could differentiate mild from moderate-to-severe inflammation with a sensitivity of 0.871 and a specificity of 0.800. MT ratio could discriminate mild from moderate-to-severe fibrosis with a sensitivity and a specificity of 0.913 and 0.923, respectively. Combining MT ratio and T2WI hyperintensity, the MRI classification moderately agreed with the pathological stricture classification (p < 0.01, κ = 0.549). In the validation set, the diagnostic accuracy of T2WI hyperintensity and MT ratio were 86% and 89%, with good agreement between MRI and histopathological classification (p < 0.01, κ = 0.665). MT ratio combined with conventional MRI improves the differentiation of fibrotic from inflammatory components of small-bowel strictures in CD patients. • MT ratio from magnetisation transfer imaging combined with T2WI from conventional MRI can simultaneously characterise bowel fibrosis and inflammation in adult Crohn’s disease.     

Diagnostic value of PET/CT for the staging and restaging of pediatric tumors

Objective  The objective of this retrospective study was to compare the diagnostic value of 2-[¹⁸F]fluoro-2-deoxy-d-glucose positron emission tomography (¹⁸F-FDG PET)/CT versus ¹⁸F-FDG PET and CT alone for staging and restaging of pediatric solid tumors. Methods  Forty-three children and adolescents (19 females and 24 males; mean age, 15.2 years; age range, 6–20 years) with osteosarcoma (n = 1), squamous cell carcinoma (n = 1), synovial sarcoma (n = 2), germ cell tumor (n = 2), neuroblastoma (n = 2), desmoid tumor (n = 2), melanoma (n = 3), rhabdomyosarcoma (n = 5), Hodgkin’s lymphoma (n = 7), non-Hodgkin-lymphoma (n = 9), and Ewing’s sarcoma (n = 9) who had undergone ¹⁸F-FDG PET/CT imaging for primary staging or follow-up of metastases were included in this study. The presence, location, and size of primary tumors was determined separately for PET/CT, PET, and CT by two experienced reviewers. The diagnosis of the primary tumor was confirmed by histopathology. The presence or absence of metastases was confirmed by histopathology (n = 62) or clinical and imaging follow-up (n = 238). Results  The sensitivities for the detection of solid primary tumors using integrated ¹⁸F-FDG PET/CT (95%), ¹⁸F-FDG PET alone (73%), and CT alone (93%) were not significantly different (p > 0.05). Seventeen patients showed a total of 153 distant metastases. Integrated PET/CT had a significantly higher sensitivity for the detection of these metastases (91%) than PET alone (37%; p < 0.05), but not CT alone (83%; p > 0.05). When lesions with a diameter of less than 0.5 cm were excluded, PET/CT (89%) showed a significantly higher specificity compared to PET (45%; p < 0.05) and CT (55%; p < 0.05). In a sub-analysis of pulmonary metastases, the values for sensitivity and specificity were 90%, 14%, 82% and 63%, 78%, 65%, respectively, for integrated PET/CT, stand-alone PET, and stand-alone CT. For the detection of regional lymph node metastases, ¹⁸F-FDG PET/CT, ¹⁸F-FDG PET alone, and CT alone were diagnostically correct in 83%, 61%, and 42%. A sub-analysis focusing on the ability of PET/CT, PET, and CT to detect osseous metastases showed no statistically significant difference between the three imaging modalities (p > 0.05). Conclusion  Our study showed a significantly increased sensitivity of PET/CT over that of PET for the detection of distant metastases but not over that of CT alone. However, the specificity of PET/CT for the characterization of pulmonary metastases with a diameter > 0.5 cm and lymph node metastases with a diameter of <1 cm was significantly increased over that of CT alone.     

Delineation and segmentation of cerebral tumors by mapping blood-brain barrier disruption with dynamic contrast-enhanced CT and tracer kinetics modeling–a feasibility study

Dynamic contrast-enhanced (DCE) imaging is a promising approach for in vivo assessment of tissue microcirculation. Twenty patients with clinical and routine computed tomography (CT) evidence of intracerebral neoplasm were examined with DCE-CT imaging. Using a distributed-parameter model for tracer kinetics modeling of DCE-CT data, voxel-level maps of cerebral blood flow (F), intravascular blood volume (v _i) and intravascular mean transit time (t ₁) were generated. Permeability-surface area product (PS), extravascular extracellular blood volume (v _e) and extraction ratio (E) maps were also calculated to reveal pathologic locations of tracer extravasation, which are indicative of disruptions in the blood-brain barrier (BBB). All maps were visually assessed for quality of tumor delineation and measurement of tumor extent by two radiologists. Kappa (κ) coefficients and their 95% confidence intervals (CI) were calculated to determine the interobserver agreement for each DCE-CT map. There was a substantial agreement for the tumor delineation quality in the F, v _e and t ₁ maps. The agreement for the quality of the tumor delineation was excellent for the v _i, PS and E maps. Concerning the measurement of tumor extent, excellent and nearly excellent agreement was achieved only for E and PS maps, respectively. According to these results, we performed a segmentation of the cerebral tumors on the base of the E maps. The interobserver agreement for the tumor extent quantification based on manual segmentation of tumor in the E maps vs. the computer-assisted segmentation was excellent (κ = 0.96, CI: 0.93–0.99). The interobserver agreement for the tumor extent quantification based on computer segmentation in the mean images and the E maps was substantial (κ = 0.52, CI: 0.42–0.59). This study illustrates the diagnostic usefulness of parametric maps associated with BBB disruption on a physiology-based approach and highlights the feasibility for automatic segmentation of cerebral tumors.     

Changes underlying the dynamic contrast-enhanced MRI response to treatment in rheumatoid arthritis

Objective Dynamic contrast-enhanced MRI of patients with rheumatoid arthritis has shown a decrease in the early enhancement rate (EER) of synovitis after treatment. The purpose of this work was to investigate the underlying changes. Methods 3D dynamic contrast-enhanced images were acquired from 13 patients before and 1–2 weeks after anti-TNFα treatment. The EER of the inflamed synovium was measured. The T₁ relaxation time of the synovitis was calculated from images at different flip angles. The time course of the arrival of gadolinium at the radial artery was determined. The gadolinium enhancement of the inflamed synovium was modeled to calculate the fractional plasma volume (v_p), the fractional extravascular, extracellular fluid volume (v_e), and the volume transfer constant (K^trans). Pre- and post-treatment values were compared and the dependence of the EER on each parameter was assessed. Results There was a decrease in the EER measured over 26 s after treatment (29%, p = 0.002). Reductions in T₁ (12%, p = 0.001), K^trans (31%, p = 0.002), and v_p (43%, p = 0.01) contributed to this; however, the EER was relatively insensitive to changes in v_e. Conclusions The decrease in EER after anti-TNFα treatment is largely caused by reductions in the volume transfer constant K^trans, the fractional plasma volume v_p, and the T₁ relaxation time. Only the contributions from K^trans and v_p directly reflect synovial vascularity.     

Sonography of the painful shoulder: role of the operator’s experience

Objective  The aim of our study was to determine the role of the operator’s experience in the sonographic evaluation of the painful shoulder and to validate assumptions about its technical performance in routine practice. Materials and methods  Two radiologists, respectively standard and expert sonographic operators, independently and prospectively scanned 65 patients with clinical suspicion of rotator cuff lesion. Magnetic resonance arthrography was the reference standard. Results  The sensitivity of the expert ultrasound operator was 95.3% for full-thickness rotator cuff tears (41/43), 70.6% for partial-thickness tears (12/17), 64.3% for intratendinous tears (9/14), 100% for abnormality of the long head of biceps tendon (seven of seven), 88.9% for supraspinatus tendinosis (16/18), 96.4% for subacromial bursa abnormalities (53/55), and 91.7% for acromioclavicular joint osteoarthritis (33/36). The two sonographic operators were in very good agreement about full-thickness rotator cuff tears (κ = 0.90), supraspinatus tendinosis (κ = 0.80), abnormalities of the long head of biceps tendon (κ = 0.84), subacromial bursa abnormalities (κ = 0.89), and acromioclavicular osteoarthritis (κ = 0.81). The agreement was only moderate for partial-thickness tears (κ = 0.63) and intratendinous tears (κ = 0.57). Conclusions  Our results show that in moderately experienced hands as in experts’ hands, sonography has a low level of interobserver variability for full-thickness rotator cuff tears. Considering partial-thickness and intratendinous rotator cuff tears, our data suggest that interobserver variability is higher.     

A comparison of tumour perfusion assessed by deconvolution-based analysis of dynamic contrast-enhanced CT and MR imaging in patients with squamous cell carcinoma of the upper aerodigestive tract

Our aim was to compare the perfusion [blood flow (BF)] values obtained by first-pass dynamic contrast-enhanced (DCE) T2-weighted magnetic resonance (MR) and computed tomography (CT) imaging of squamous cell carcinoma (SCC) in the upper aerodigestive tract in the same patient population. Seventeen patients with histologically proven primary SCC of the upper aerodigestive tract were prospectively evaluated. The perfusion CT studies were obtained using a 16-row multi-slice CT scanner running a commercial software package with a deconvolution-based technique; while the perfusion MR studies (1.5 T) were analysed with in-house-written MR perfusion software based also on a deconvolution technique. The mean perfusion values of SCC assessed by perfusion CT and MR imaging were 68.93 ± 31.61 and 81.56 ± 49.25 ml/min/100 g, respectively. The Bland-Altman graph showed a proportional error in the perfusion values measured by DCE-CT and -MR imaging; however, the degree of agreement was acceptable (95% limits of agreement: −66.1 to 40.8). Regression analysis of the perfusion values demonstrated significant correlation between the modalities: BF_MR = 1.34 × BF_CT – 10.93 (P < 0.0005, r ² = 0.74). The parametric maps generated by both modalities provided insights into the tumour perfusion, while analysis of the obtained perfusion values demonstrated that both modalities may be used interchangeably in SCC in the upper aerodigestive tract.     

Comparison of sensitivity and reading time for the use of computer-aided detection (CAD) of pulmonary nodules at MDCT as concurrent or second reader

The purpose of this study was to compare sensitivity for detection of pulmonary nodules in MDCT scans and reading time of radiologists when using CAD as the second reader (SR) respectively concurrent reader (CR). Four radiologists analyzed 50 chest MDCT scans chosen from clinical routine two times and marked all detected pulmonary nodules: first with CAD as CR (display of CAD results immediately in the reading session) and later (median 14 weeks) with CAD as SR (display of CAD markers after completion of first reading without CAD). A Siemens LungCAD prototype was used. Sensitivities for detection of nodules and reading times were recorded. Sensitivity of reading with CAD as SR was significantly higher than reading without CAD (p < 0.001) and CAD as CR (p < 0.001). For nodule size of 1.75 mm or above no significant sensitivity difference between CAD as CR and reading without CAD was observed; e.g., for nodules above 4 mm sensitivity was 68% without CAD, 68% with CAD as CR (p = 0.45) and 75% with CAD as SR (p < 0.001). Reading time was significantly shorter for CR (274 s) compared to reading without CAD (294 s; p = 0.04) and SR (337 s; p < 0.001). In our study CAD could either speed up reading of chest CT cases for pulmonary nodules without relevant loss of sensitivity when used as CR, or it increased sensitivity at the cost of longer reading times when used as SR.     

Initial clinical results for breath-hold CT-based processing of respiratory-gated PET acquisitions

Purpose  Respiratory motion causes uptake in positron emission tomography (PET) images of chest structures to spread out and misregister with the CT images. This misregistration can alter the attenuation correction and thus the quantisation of PET images. In this paper, we present the first clinical results for a respiratory-gated PET (RG-PET) processing method based on a single breath-hold CT (BH-CT) acquisition, which seeks to improve diagnostic accuracy via better PET-to-CT co-registration. We refer to this method as “CT-based” RG-PET processing. Methods  Thirteen lesions were studied. Patients underwent a standard clinical PET protocol and then the CT-based protocol, which consists of a 10-min List Mode RG-PET acquisition, followed by a shallow end-expiration BH-CT. The respective performances of the CT-based and clinical PET methods were evaluated by comparing the distances between the lesions’ centroids on PET and CT images. SUV_MAX and volume variations were also investigated. Results  The CT-based method showed significantly lower (p = 0.027) centroid distances (mean change relative to the clinical method = −49%; range = −100% to 0%). This led to higher SUV_MAX (mean change = +33%; range = −4% to 69%). Lesion volumes were significantly lower (p = 0.022) in CT-based PET volumes (mean change = −39%: range = −74% to −1%) compared with clinical ones. Conclusions  A CT-based RG-PET processing method can be implemented in clinical practice with a small increase in radiation exposure. It improves PET-CT co-registration of lung lesions and should lead to more accurate attenuation correction and thus SUV measurement.     

Prevalence and correlates of pulmonary emphysema in smokers and former smokers. A densitometric study of participants in the ITALUNG trial

We assessed with computed tomography (CT) densitometry the prevalence of emphysema in 266 (175 men and 91 women; mean age 64 ± 4 years) smokers and former smokers enrolled in the ITALUNG trial of lung cancer screening with low-dose thin-slice CT. Whole-lung volume and the relative area at −950 Hounsfield units (RA₉₅₀) and mean lung attenuation (MLA) in 1 of every 10 slices (mean, 24 slices per subject) were measured. Lung volume, MLA and RA950 significantly correlated each other and with age. Average RA950 >6.8% qualifying for emphysema was present in 71 (26.6%) of 266 subjects, with a higher prevalence in men than in women (30.3% vs 19.8%; p = 0.003). Only in smokers was a weak (r = 0.18; p = 0.05) correlation between RA950 and packs/year observed. In multiple regression analysis, the variability of RA950 (R2 = 0.24) or MLA (R2 = 0.34) was significantly, but weakly explained by age, lung volume and packs/year. Other factors besides smoking may also have a significant role in the etiopathogenesis of pulmonary emphysema. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Simultaneous evaluation of myocardial blood flow,cardiac function and lung water content using [<Superscript>15</Superscript>O]H<Subscript>2</Subscript>O and positron emission tomography

Purpose This study sought to evaluate an imaging approach using [¹⁵O]H₂O and positron emission tomography (PET) for simultaneous assessment of myocardial perfusion, cardiac function and lung water content as a potential indicator of pulmonary oedema. Methods Twenty-six subjects divided into two groups (group I, 13 patients with idiopathic dilated cardiomyopathy; group II, 13 healthy volunteers) underwent dynamic PET scanning after intravenous infusion of ≈995 MBq [¹⁵O]H₂O. In both groups, echocardiograms were performed after the PET studies. From the dynamic [¹⁵O]H₂O data, lung water content (LWC) at equilibrium, myocardial blood flow (MBF), cardiac output (CO), stroke volume (SV) and stroke volume indexes (SVI) using the indicator dilution principle were determined. Results LWC was 18% (p = 0.038) higher in patients than in controls. Global MBF did not differ significantly between the groups, but regional MBF values were significantly lower (p < 0.05) in the anterior and septal walls in the patient group. The results of the Passing-Bablok regression indicated the absence of a systematic difference between the two techniques. Bland-Altman analysis performed for each group (patients vs healthy controls) showed a non-significant bias (p > 0.1) of −0.02 ± 0.82 vs −0.05 ± 0.54 l/min (CO), −1.44 ± 14.31 vs 1.70 ± 10.56 ml/beat (SV) and 0.47 ± 6.21 vs 0.30 ± 5.02 ml/beat/m² (SVI). The 95% limits of agreement were −1.62 to 1.59 vs −1.11 to 1.01 l/min (CO), −26.61 to 29.49 vs −22.39 to 18.99 ml/beat (SV) and −11.69 to 12.88 vs −9.53 to 10.14 ml/beat/m² (SVI). Right ventricular CO was increased by 33% (p = 0.014) in the patient group as compared with normal controls. Conclusion Our results demonstrate that additional analysis of cardiac function and lung water content are feasible from the dynamic cardiac [¹⁵O]H₂O PET studies acquired for myocardial perfusion. The parameters appear to work as expected. Further studies are warranted to elucidate the clinical value of these new parameters. This study was financially supported by grants from Turku University Hospital (EVO) and Finnish Foundation for Cardiovascular Research.     

The additional value of CT images interpretation in the differential diagnosis of benign vs. malignant primary bone lesions with 18F-FDG-PET/CT

Objective  To evaluate the value of a dedicated interpretation of the CT images in the differential diagnosis of benign vs. malignant primary bone lesions with 18fluorodeoxyglucose-positron emission tomography/computed tomography (18F-FDG-PET/CT). Materials and methods  In 50 consecutive patients (21 women, 29 men, mean age 36.9, age range 11–72) with suspected primary bone neoplasm conventional radiographs and 18F-FDG-PET/CT were performed. Differentiation of benign and malignant lesions was separately performed on conventional radiographs, PET alone (PET), and PET/CT with specific evaluation of the CT part. Histology served as the standard of reference in 46 cases, clinical, and imaging follow-up in four cases. Results  According to the standard of reference, conventional 17 lesions were benign and 33 malignant. Sensitivity, specificity, and accuracy in assessment of malignancy was 85%, 65% and 78% for conventional radiographs, 85%, 35% and 68% for PET alone and 91%, 77% and 86% for combined PET/CT. Median SUV_max was 3.5 for benign lesions (range 1.6–8.0) and 5.7 (range 0.8–41.7) for malignant lesions. In eight patients with bone lesions with high FDG-uptake (SUV_max ≥ 2.5) dedicated CT interpretation led to the correct diagnosis of a benign lesion (three fibrous dysplasias, two osteomyelitis, one aneurysmatic bone cyst, one fibrous cortical defect, 1 phosphaturic mesenchymal tumor). In four patients with lesions with low FDG-uptake (SUV_max < 2.5) dedicated CT interpretation led to the correct diagnosis of a malignant lesion (three chondrosarcomas and one leiomyosarcoma). Combined PET/CT was significantly more accurate in the differentiation of benign and malignant lesions than PET alone (p = .039). There was no significant difference between PET/CT and conventional radiographs (p = .625). Conclusion  Dedicated interpretation of the CT part significantly improved the performance of FDG-PET/CT in differentiation of benign and malignant primary bone lesions compared to PET alone. PET/CT more commonly differentiated benign from malignant primary bone lesions compared with conventional radiographs, but this difference was not significant.     

18F-choline PET/CT imaging of RECIST measurable lesions in hormone refractory prostate cancer

Purpose  Apply measurability criteria based on the response evaluation criteria in solid tumors (RECIST) to lesions found on ¹⁸F-choline positron emission tomography (PET)/computerized tomography (CT) in patients with hormone refractory prostate cancer. Methods  Whole-body PET followed by CT or in-line PET/CT using 3.3–4 MBq/kg of ¹⁸F-choline was performed prospectively on 30 patients with prostate cancer, castrate testosterone levels, and rising post-treatment prostate specific antigen (PSA) levels. Lesions demonstrating increased ¹⁸F-choline uptake were classified as measurable or non-measureable based on RECIST. Results  Three patients were known previously to have RECIST measurable lesions, 10 patients had metastatic findings on radionuclide bone scan, and 17 patients had elevated serum PSA level as the only evidence of disease. Lesions demonstrating increased ¹⁸F-choline uptake were found in 28 (93%) patients. Thirty-eight PET/CT lesions from 14 patients were measurable by RECIST. Lymph node maximum standardized uptake value (SUV_max) correlated with lymph node diameter (Pearson r = 0.44, p < 0. 001). RECIST measurable lymph node SUV_max was significantly higher than that of non-measurable nodes (8.1 vs. 3.7, p < 0.0001). Detection of skeletal, prostatic, or RECIST-compatible lesions was more likely with a PSA level greater than 4.0 ng/ml (Fisher exact p = 0.0005). Conclusion  Lesions detected with ¹⁸F-choline PET/CT are frequently measurable by RECIST at baseline. Therefore, it may be feasible to include comparisons to RECIST in evaluations of ¹⁸F-choline as a therapeutic response marker for hormone refractory prostate cancer. The findings and conclusions expressed in this study do not necessarily represent the views of The Queen’s Medical Center.     

Oxygen-sensitive <Superscript>3</Superscript>He-MRI in bronchiolitis obliterans after lung transplantation

Oxygen-sensitive ³He-MRI was studied for the detection of differences in intrapulmonary oxygen partial pressure (pO₂) between patients with normal lung transplants and those with bronchiolitis obliterans syndrome (BOS). Using software developed in-house, oxygen-sensitive ³He-MRI datasets from patients with normal lung grafts (n = 8) and with BOS (n = 6) were evaluated quantitatively. Datasets were acqiured on a 1.5-T system using a spoiled gradient echo pulse sequence. Underlying diseases were pulmonary emphysema (n = 10 datasets) and fibrosis (n = 4). BOS status was verified by pulmonary function tests. Additionally, ³He-MRI was assessed blindedly for ventilation defects. Median intrapulmonary pO₂ in patients with normal lung grafts was 146 mbar compared with 108 mbar in patients with BOS. Homogeneity of pO2 distribution was greater in normal grafts (standard deviation pO2 34 versus 43 mbar). Median oxygen decrease rate during breath hold was higher in unaffected patients (−1.75 mbar/s versus −0.38 mbar/s). Normal grafts showed fewer ventilation defects (5% versus 28%, medians). Oxygen-sensitive ³He-MRI appears capable of demonstrating differences of intrapulmonary pO2 between normal lung grafts and grafts affected by BOS. Oxygen-sensitive ³He-MRI may add helpful regional information to other diagnostic techniques for the assessment and follow-up of lung transplant recipients.