Computed tomography perfusion using first pass methods for lung nodule characterization.

OBJECTIVE: To evaluate computed tomography (CT) perfusion using first pass methods for lung nodule characterization. METHODS: Fifty-seven patients with 51 malignant and 6 benign nodules underwent first-pass, dynamic contrast-enhanced-CT (50 mL, 3-5 mL/s.). Kinetic analysis tools were CT Perfusion 3 (GEMS, Milwaukee, WI), a distributed parameter model approach, yielding blood volume (BV; mL/100 g), blood flow (BF; mL/min/100 g), mean transit time (1/s), and permeability surface area (mL/min/100 g), and an in-house Patlak-style analysis yielding fractional BV (mL/100 g) and an estimate of extraction (Kps, mL/100 g/min). RESULTS: CT Perfusion 3 parameters in malignant and benign nodules were: mean transit time 10.1 +/- 0.9 1/s versus 11.1 +/- 3.1 1/s (ns), permeability surface 23.3 +/- 9.1 mL/min/100 g versus 19.6 +/- 10.3 mL/min/100 g (ns), BF 111.3 +/- 8.7 mL/min/100 g versus 39.1+/- 5.7 mL/min/100 g (P < 0.001), BV 9.3+/- 0.7 mL/100 g versus 4.1 +/- 1.1 mL/100 g (P < 0.002); Patlak parameters were: Kps 13.3 +/- 1.2 mL/100 g/min versus 3.9 +/- 0.8 mL/100 g/min (P < 0.001), BV 8.4 +/- 0.8 mL/100 g versus 3.6 +/- 1.3 mL/100 g (P < 0.01). The two kinetic methods show good agreement for BV estimation (Bland-Altman plot). The limits of agreement (bias +/-2 standard deviation of bias) were 1.2 +/- 5.3 mL/100 g. CONCLUSION: CT Perfusion using first pass modeling appears feasible for lung nodule characterization. Given the short acquisition duration used, weaknesses of the modeling methods are exposed. Nonetheless, microvascular characterization in terms of BF, BV, or Kps appears useful in distinguishing malignant from benign nodules.

Assessment of the tumor microenvironment in cervix cancer using dynamic contrast enhanced CT, interstitial fluid pressure and oxygen measurements.

PURPOSE: Interstitial fluid pressure (IFP) and oxygen (pO(2)) measurements are prognostic factors in cervical cancer. The purpose of this study was to determine the relationship between IFP and oxygenation and parameters derived from dynamic contrast-enhanced computed tomography (DCE-CT). METHODS AND MATERIALS: Dynamic contrast-enhanced computed tomography was performed in 32 patients with cervical cancer before radiation therapy. Images were acquired during intravenous contrast injection at 1 per s for 120 s and 1 per 15 s for 60 s. DCE-CT was analyzed using CT Perfusion 3 software (GE Medical Systems) to derive tumor blood flow (BF), permeability surface area product, blood volume, and mean transit time. Further analysis was performed to obtain relative peak enhancement, residual enhancement at 3 min after contrast injection (RE), time to peak and initial slope. Nodal status and tumor size were assessed with MRI. From in vivo IFP (n = 31) and pO(2) (n = 31) tumor measurements median pO(2) (mO(2)), percentage measurements less than 5 mm Hg (HP5) and mean IFP values were calculated. RESULTS: There was a positive correlation between BF and mO(2) (r = 0.47, p = 0.007) and between RE and HP5 (r = 0.39, p = 0.03). There was no correlation between IFP and DCE-CT parameters. CONCLUSION: There is a moderately positive, correlation between tumor oxygenation and BF as well as RE and HP5. Further study is required to determine if DCE-CT parameters are useful predictors of tumor behavior in cervical cancer.

Lung cancer screening using low-dose computed tomography in at-risk individuals: the Toronto experience.

OBJECTIVE: The Department of Medical Imaging at the University Health Network in Toronto is performing a lung cancer screening study, utilizing low-dose computed tomography (LDCT) as the modality. Baseline and annual repeat results are reported on the first 3352 participants, enrolled between June 2003 and May 2007. METHODS: Enrollment was limited to those aged 50 years or older, with a smoking history of at least 10 pack-years, no previous cancer and general good health. A helical low-dose CT (LDCT) of the chest was performed using 120kVp, 40-60mA, images were reconstructed with 1-1.25mm overlapping slices. The primary objectives were the detection of parenchymal nodules and diagnosis of early stage lung cancer. Baseline LDCTs were termed positive if at least one indeterminate non-calcified nodule 5mm or larger in size, or non-solid nodule 8mm or larger in size was identified. Follow up periods for individuals with a positive baseline LDCT were determined by nodule characteristics. RESULTS: The median age at baseline was 60 years (range 50-83), with a median of 30 pack-years of cigarette smoking (range 10-189). Baseline CT evaluations were positive in 600 (18%) participants. To date, 2686 (80%) of the participants have returned for at least one annual repeat screening LDCT. Biopsies have been recommended for 82 participants since the study began, and 64 have been diagnosed with screen-detected cancer (62 lung, two plasmacytoma of the rib). A total of 65 lung cancers have been diagnosed (62 screen-detected, 3 interim), 57 are NSCLC (82% with known stage are stage I or II) and the rate of surgical resection was 80%. Sensitivity and specificity of the protocol in successfully diagnosing early stage lung cancers were 87.7% and 99.3%, respectively. CONCLUSIONS: Data indicate that LDCT can identify small lung cancers in an at-risk population. The diagnostic algorithm results in few false-positive invasive procedures. Most cancers are detected at an early stage, where the cancer is resectable with a greater potential for cure. Long-term follow up of lung cancer cases will be carried out to determine survival.

Correlations between dynamic contrast-enhanced magnetic resonance imaging-derived measures of tumor microvasculature and interstitial fluid pressure in patients with cervical cancer.

PURPOSE: To correlate permeability (rk(trans)), extracellular volume fraction (rv(e)), relative to muscle and initial area under the enhancement curve (IAUC(60m)) determined by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) with in vivo measurements of interstitial fluid pressure (IFP) in patients with cervical cancer. MATERIALS AND METHODS: DCE-MRI and IFP measurements were performed of cervical tumors of 32 patients prior to therapy. Median tumor rk(trans) and rv(e) were derived from a bidirectional two-compartment model using an input function derived from muscle. Median IAUC(60m) was defined as the integral of tumor enhancement in the first 60 seconds divided by the similar muscle enhancement integral. These parameters were correlated with the mean tumor IFP. RESULTS: There was a significant negative correlation between IAUC(60m) and IFP (r = -0.42, P = 0.016) and between rk(trans) and IFP (r = -0.47, P = 0.008). The was no significant correlation between IFP and rv(e). CONCLUSION: There is a moderate negative correlation between IAUC(60m), rk(trans), and IFP in cervical cancer. This suggests that these parameters may be of value in assessment of tumor behavior.

Lung cancer screening with low-dose computed tomography: Canadian experience.

INTRODUCTION: In 2003, the Department of Medical Imaging at the University Health Network in Toronto, Ontario, became the first Canadian site of the Intemational Early Lung Cancer Action Program (I-ELCAP). We report the results from the first 1000 baseline studies. METHODS: Between June 2003 and December 2005, we enrolled 1000 high-risk smokers (that is, smokers with a history of at least 10 pack years, or the equivalent of one pack daily for 10 years), aged 55 years or older. A low-dose helical computed tomography (CT) (40 to 60 mA, 120 kV) was performed with 1.0 mm to 1.25 mm collimation. Nodules found at baseline were followed according to the I-ELCAP protocol: (1) no noncalcified nodules (NCNs) or NCNs < or =4 mm or nonsolid nodules < 8 mm, annual repeat; (2) NCNs > or =5 mm or nonsolid nodules > or =8 mm, 3-month follow-up; or (3) nonsolid nodules > or =15 mm, antibiotics and 1-month follow-up. RESULTS: The first 1000 study participants were aged 63 years, standard deviation (SD) 6 years, with a smoking history of 38 pack years, SD 22 pack years; 662 (66%) were former smokers, and 338 (34%) were current smokers; 453 (45%) were men, and 547 (55%) were women. Of the participants, 256 (26%) had a positive baseline low-dose computed tomography (LDCT) scan; 227 (23%) were followed after 3 months and 16 (1.6%) after 1 month; 7 (0.7%) received a contrast-enhanced CT and 6 (0.6%) an immediate CT-guided biopsy. Twenty-six invasive procedures were performed: 22 CT-guided biopsies, 1 ultrasound-guided lymph node metastasis biopsy, 1 bronchoscopic biopsy, and 2 surgeries. The malignancy rate of the invasive procedures was 85%. Overall, the malignancy prevalence is 2.2%. Of the malignancies, 20 are lung carcinomas: 19 non-small-cell lung carcinomas (NSCLCs) (14 adenocarcinoma or bronchioalveolar carcinoma [BAC], 4 squamous carcinoma, and 1 large-cell carcinoma) and 1 small-cell carcinoma; 15 (78%) of the NSCLCs are Stage I. Fourteen patients underwent surgery (1 pneumonectomy, 9 lobectomies, and 4 segmentectomies). CONCLUSION: Our results confirm that LDCT identifies small, early-stage, resectable lung cancer in a high-risk population.