Koichi Kawanaka

Diffusion-weighted magnetic resonance imaging for diagnosing malignant pulmonary nodules/masses: Comparison with positron emission tomography

Introduction: Recent developments of diffusion-weighted magnetic resonance imaging (DWI) make it possible to image malignant tumors to provide tissue contrast based on difference in the diffusion of water molecules among tissues, which can be measured by apparent diffusion coefficient (ADC) value. The aim of this study is to examine the usefulness of DWI for benign/malignant discrimination of pulmonary nodules/masses compared with 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET). Methods: PET and DWI were carried out prospectively in 104 patients with 140 pulmonary nodules/masses before surgery. FDG uptake of each lesion was quantitatively measured by a contrast ratio of standard uptake value (SUV-CR) between the lesions and contralateral lung. Diffusion of water molecule in each lesion was quantitatively measured by a minimum ADC (ADC-min). The diagnostic results were compared between the two modalities. Results: The receiver operating characteristics curve showed cutoff values of the ADC-min and the SUV-CR for benign/malignant discrimination to be 1.1 × 10−3 mm2/s and 0.37, respectively. DWI and PET showed sensitivities of 0.70 and 0.72 and specificities of 0.97 and 0.79, respectively. Although there was no significant difference in sensitivity between the two methods, DWI showed a significantly higher specificity than PET because of fewer false-positives for active inflammatory lesions (p = 0.03). The ADC-min and SUV-CR values showed a significant reverse correlation (r = −0.504, p < 0.001). Conclusions: DWI may be able to be used in place of FDG-PET to distinguish malignant from benign pulmonary nodules/masses with fewer false-positive results compared with FDG-PET.

Diffusion-weighted magnetic resonance imaging can be used in place of positron emission tomography for N staging of non–small cell lung cancer with fewer false-positive results

OBJECTIVE One of the deficiencies of positron emission tomography for N staging in lung cancer is a false-positive result caused by concurrent lymphadenitis. Recently, diffusion-weighted magnetic resonance imaging has been reported to be able to image tumors of body organs. The aim of this study is to examine the usefulness of diffusion-weighted magnetic resonance imaging for N staging of non-small cell lung cancer compared with positron emission tomography-computed tomography. METHODS Both positron emission tomography-computed tomography and diffusion-weighted magnetic resonance imaging were prospectively used in 88 patients before surgical intervention for non-small cell lung cancer to examine 734 lymph node stations. The diagnostic results of positron emission tomography-computed tomography and diffusion-weighted magnetic resonance imaging were compared. The diameters of the metastatic foci within lymph nodes were measured on hematoxylin and eosin-stained sections to compare the detectable size of metastatic foci between positron emission tomography-computed tomography and diffusion-weighted magnetic resonance imaging. RESULTS The accuracy of N staging in the 88 patients was 0.89 with diffusion-weighted magnetic resonance imaging, which was significantly higher than the value of 0.78 obtained with positron emission tomography-computed tomography (P = .012), because of less overstaging in the former. Among the 734 lymph node stations examined pathologically, 36 had metastases, and the other 698 did not. Although there was no significant difference in the diagnosis of the 36 metastatic lymph node stations between the 2 methods, diffusion-weighted magnetic resonance imaging was more accurate for diagnosing the 698 nonmetastatic stations than positron emission tomography-computed tomography because of fewer false-positive results (P = .002). The detectable size of metastatic foci within lymph nodes was 4 mm in both positron emission tomography-computed tomography and diffusion-weighted magnetic resonance imaging. CONCLUSIONS Diffusion-weighted magnetic resonance imaging can be used in place of positron emission tomography-computed tomography for N staging of non-small cell lung cancer with fewer false-positive results compared with positron emission tomography-computed tomography.

Computer-Aided Volumetry of Pulmonary Nodules Exhibiting Ground-Glass Opacity at MDCT

OBJECTIVE The purpose of this study was to investigate the accuracy and reproducibility of results acquired with computer-aided volumetry software during MDCT of pulmonary nodules exhibiting ground-glass opacity. MATERIALS AND METHODS To evaluate the accuracy of computer-aided volumetry software, we performed thin-section helical CT of a chest phantom that included simulated 3-, 5-, 8-, 10-, and 12-mm-diameter ground-glass opacity nodules with attenuation of -800, -630, and -450 HU. Three radiologists measured the volume of the nodules and calculated the relative volume measurement error, which was defined as follows: (measured nodule volume minus assumed nodule volume / assumed nodule volume) x 100. Two radiologists performed two independent measurements of 59 nodules in humans. Intraobserver and interobserver agreement was evaluated with Bland-Altman methods. RESULTS The relative volume measurement error for simulated ground-glass opacity nodules measuring 3 mm ranged from 51.1% to 85.2% and for nodules measuring 5 mm or more in diameter ranged from -4.1% to 7.1%. In the clinical study, for intraobserver agreement, the 95% limits of agreement were -14.9% and -13.7% and -16.6% to 15.7% for observers A and B. For interobserver agreement, these values were -16.3% to 23.7% for nodules 8 mm in diameter or larger. CONCLUSION With computer-aided volumetry of ground-glass opacity nodules, the relative volume measurement error was small for nodules 5 mm in diameter or larger. Intraobserver and interobserver agreement was relatively high for nodules 8 mm in diameter or larger.

Initial experience with X-ray CT based attenuation correction in myocardial perfusion SPECT imaging using a combined SPECT/CT system

Objective: Attenuation artifacts adversely affect the diagnostic accuracy of myocardial perfusion imaging. We assessed the clinical usefulness of X-ray CT based attenuation correction (AC) in patients undergoing myocardial perfusion imaging by comparing their myocardial AC- and non-corrected (NC) SPECT images with the coronary angiography (CAG).Methods: We retrospectively reviewed the myocardial SPECT images of 30 patients (18 men, 12 women; mean age 68 years). Thirteen of 30 patients with coronary artery disease (CAD) and 17 without CAD were confirmed by CAG. They underwent sequential CT and myocardial SPECT imaging with thallium-201 (111 MBq) under an exercise or pharmacological stress protocol using our combined SPECT/ CT system. Two readers reviewed the myocardial SPECT images for the presence of CAD on a 4-point scale where 1 = normal, 2 = probably normal, 3 = probably abnormal, and 4 = abnormal. Two reading sessions were held. First, non-corrected (NC)-SPECT and second, AC-SPECT images using X-ray CT images were interpreted. Interobserver variability was assessed with kappa statistics. Diagnostic performance (accuracy) of coronary arterial stenosis was compared between AC- and NC-images.Results: Interobserver agreement for visual assessment was substantial or almost perfect. For AC-images, the observer consensus for analysis was 0.84 for the LAD-, 0.87 for the LCX-, and 0.71 for the RCA-territory. For NC-images, it was 0.91, 0.71, and 0.78. AC resulted in statistically significant improvements in overall diagnostic accuracy (sensitivity/ specificity/accuracy = 76%/93%/89%, 67%/86%/81%, respectively, for AC- and NC-images).Conclusions: Because of an increase in the specificity, diagnostic accuracy was significantly increased on AC-images. These preliminary data suggest that X-ray CT based AC in myocardial SPECT imaging has the potential to develop into a reliable clinical technique.

Volume-Doubling Time of Pulmonary Nodules with Ground Glass Opacity at Multidetector CT: Assessment with Computer-Aided Three-Dimensional Volumetry

RATIONALE AND OBJECTIVES To investigate the volume-doubling time (VDT) of histologically proved pulmonary nodules showing ground glass opacity (GGO) at multidetector CT (MDCT) using computer-aided three-dimensional volumetry. MATERIALS AND METHODS We retrospectively evaluated 47 GGO nodules (mixed n = 28, pure n = 19) that had been examined by thin-section helical CT more than once. They were histologically confirmed as atypical adenomatous hyperplasia (AAH, n = 13), bronchioloalveolar carcinoma (BAC, n = 22), and adenocarcinoma (AC, n = 12). Using computer-aided three-dimensional volumetry software, two radiologists independently performed volumetry of GGO nodules and calculated the VDT using data acquired from the initial and final CT study. We compared VDT among the three pathologies and also compared the VDT of mixed and pure GGO nodules. RESULTS The mean VDT of all GGO nodules was 486.4 ± 368.6 days (range 89.0-1583.0 days). The mean VDT for AAH, BAC, and AC was 859.2 ± 428.9, 421.2 ± 228.4, and 202.1 ± 84.3 days, respectively; there were statistically significant differences for all comparative combinations of AAH, BAC, and AC (Steel-Dwass test, P < .01). The mean VDT for pure and mixed GGO nodules was 628.5 ± 404.2 and 276.9 ± 155.9 days, respectively; it was significantly shorter for mixed than pure GGO nodules (Mann-Whitney U-test, P < .01). CONCLUSION The evaluation of VDT using computer-aided volumetry may be helpful in assessing the histological entities of GGO nodules.

Detection of nodules showing ground-glass opacity in the lungs at low-dose multidetector computed tomography: phantom and clinical study.

To investigate the effect of the radiation dose (tube current second product) and the attenuation value of nodules with ground-glass opacity (GGO) on their detectability at multidetector computed tomography (MDCT). Methods: We scanned a chest CT phantom that included simulated GGO nodules with an MDCT scanner. The attenuation value of the simulated lung parenchyma was −900 Hounsfield units (HU); it was −800 and −650 HU for the simulated GGO nodules. We used a tube current second product of 180 mA as the standard and 21, 45, 60, and 90 mAs as the low-dose and performed receiver operating characteristic analysis to compare the performance of 5 radiologists in detecting GGO nodules at each milliampere. To assess the detectability of GGO nodules on human lung images, the observers were presented with 38 GGO nodules from 15 patients. The 5 radiologists independently reviewed chest CT images at 21 and 45 mAs. Results: In the phantom study, the Az value for GGO nodules with a CT number of −800 HU was significantly lower at 21 than 180 effective mA (0.86 vs. 0.96; P < 0.01). There was no statistically significant difference in the Az value of GGO nodules with a CT number of −650 HU, irrespective of milliamperes used (P = 0.165). In the clinical study, 39.5% and 25.8% of GGO were missed at 21 and 45 mAs, respectively. Conclusions: At MDCT, GGO nodules with a CT number of −650 HU or less were difficult to detect at the lower milliampere settings (21 and 45 mAs).

Percutaneous radiofrequency ablation for pulmonary metastases from hepatocellular carcinoma: Results of a multicenter study in Japan

PURPOSE To retrospectively evaluate technical success, effectiveness, complications, patient survival, and prognostic factors with percutaneous radiofrequency (RF) ablation for pulmonary metastases resulting from hepatocellular carcinoma (HCC). MATERIALS AND METHODS Thirty-two patients from six institutions were included, with a total of 83 pulmonary metastases treated in 65 sessions. RF ablation was always performed percutaneously with computed tomography (CT) guidance. Primary endpoints were technical success and technique effectiveness. Technique effectiveness was evaluated based on sequential follow-up CT images. Secondary study endpoints were complications, patient survival, and determination of prognostic factors. Complications were classified as major or minor. Prognostic factors were determined by analyzing multiple variables with the log-rank test. RESULTS Technical success rate was 100%. Primary technique effectiveness rates were 92% each at 1, 2, and 3 years. Major and minor complications occurred after 16 (25%) and 23 (35%) of the 65 sessions, respectively. The median follow-up period was 20.5 months. Overall survival rates were 87% at 1 year and 57% each at 2 and 3 years (median and mean survival times, 37.7 mo and 43.2 mo, respectively). Significantly better survival rates were obtained in cases of (i) no viable intrahepatic recurrence (P < .001), (ii) Child-Pugh class A disease (P < .001), (iii) absence of liver cirrhosis (P < .001), (iv) absence of hepatitis C virus infection (P = .006), and (v) α-fetoprotein level of 10 ng/mL or lower (P = .007) at the time of RF ablation. CONCLUSIONS RF ablation appears effective, with an acceptable safety profile, in selected patients with pulmonary metastases resulting from HCC.

Marking of small pulmonary nodules before thoracoscopic resection: injection of lipiodol under CT-fluoroscopic guidance.

RATIONALE AND OBJECTIVES The aim of the present study was to examine the usefulness and record the complications of preoperative lipiodol marking using computed tomographic (CT) fluoroscopy for the intraoperative localization of 107 pulmonary nodules. METHODS Lipiodol marking was performed under CT fluoroscopic guidance in 65 patients with 107 nodules. Of these, 65 (60.7%) were nodules with ground-glass opacity, and 42 were solid nodules on CT images. All nodules were marked with 0.3 to 0.5 mL lipiodol under CT fluoroscopic guidance 1 or 3 days before or on the day of surgery. At surgery, marked nodules were grasped with ring-shaped forceps under a C-arm fluoroscope and resected. Postoperatively, all 55 patients with malignant tumors (n = 78) were followed by computed tomography at 3-month intervals to detect needle tract or pleural recurrence. RESULTS All 107 nodules were marked with lipiodol; under the C-arm fluoroscope, they appeared as radiopaque spots. On postprocedural computed tomography, pneumothorax occurred in 20 patients (31%); its incidence was higher in patients with lung emphysema surrounding the nodules (P = .09), three of whom required tube drainage. Computed tomography detected pulmonary hemorrhage in 10 patients (15%); it was more frequent in patients with deep than shallow nodules (>or=6 cm from the pleural surface and <6 cm from the pleural surface, respectively; P = .04). No patients presented with recurrence in needle tracts or on the pleural surface during a median postoperative follow-up of 14 months. CONCLUSION Lipiodol marking under CT fluoroscopic guidance is a useful and safe procedure for the intraoperative localization of ground-glass opaque and/or small, deep, solid nodules.

Struma ovarii coexisting with mucinous cystadenoma detected by radioactive iodine.

The authors describe a case of struma ovarii coexisting with mucinous cystadenoma. Ultrasonography and magnetic resonance imaging showed a multilocular cystic mass with a solid component. The ovarian tumor demonstrated uptake of I-123 sodium iodide, allowing a preoperative diagnosis of struma ovarii. In women with an unexplained increase in thyroid function and low I-123 uptake in the cervical thyroid gland, scintigraphy of the pelvis should be considered.

Sequential combination treatment (arterial embolization and percutaneous radiofrequency ablation) of inoperable renal cell carcinoma: single-center pilot study:

Background Potential drawbacks of percutaneous radiofrequency ablation (RFA) for renal cell carcinoma (RCC) include local recurrence after RFA due to a limited ablation area, massive hemorrhage induced by kidney puncture, and difficulty in visualizing the tumor at CT-guided puncture. Purpose To evaluate retrospectively the technical success, effectiveness, and complications elicited in patients with unresectable RCC following single-session sequential combination treatment consisting of renal arterial embolization followed by RFA. Material and Methods Ten patients (12 RCCs) who were not candidates for surgery were included in this pilot study. All tumors ranged from 18–66 mm in size (mean 31 ± 3.9 mm), and were percutaneously ablated several hours after embolization of the tumor vessels with iodized oil and gelatin sponges. We evaluated the technical success, effectiveness, effect on renal function, and complications of this treatment. Effectiveness was judged on CT and/or MR images obtained every three months after RFA. The effect on renal function was assessed based on the creatinine level and glomerular filtration rate (GFR) before, one week, and three months after the procedure. Results Renal arterial embolization followed by percutaneous RFA was technically successful in all patients. On contrast CT and/or MR images obtained one week and three months after RFA we observed necrosis in the embolized segment of all RCCs. There were no major complications during and after the procedure. All patients reported tolerable pain and a burning sensation during RFA. After the procedure, five patients (50%) experienced back pain, one each manifested fluid collection, subcapsular hematomas, hematuria, or nausea. There were no instances of recurrence during a mean follow-up period of 47 ± 3.8 months. We noted no significant difference in serum creatinine and GFR before and after treatment. Conclusion Our pilot study suggests that sequential combination treatment by renal arterial embolization followed by percutaneous RFA is feasible in patients with inoperable RCC. The treatment complications were acceptable and excellent effects were obtained.