Akitoshi Inoue

A phantom study for ground-glass nodule detectability using chest digital tomosynthesis with iterative reconstruction algorithm by ten observers: association with radiation dose and nodular characteristics

OBJECTIVE To compare detectability of simulated ground-glass nodules (GGNs) on chest digital tomosynthesis (CDT) among 12 images obtained at 6 radiation doses using 2 reconstruction algorithms and to analyze its association with nodular size and density. METHODS 74 simulated GGNs [5, 8 and 10 mm in diameter/-630 and -800 Hounsfield units (HU) in density] were placed in a chest phantom in 14 nodular distribution patterns. 12 sets of coronal images were obtained using CDT at 6 radiation doses: 120 kV-10 mA/20 mA/80 mA/160 mA, 100 kV-80 mA and 80 kV-320 mA with and without iterative reconstruction (IR). 10 radiologists recorded GGN presence and locations by continuously distributed rating. GGN detectability was compared by receiver operating characteristic analysis among 12 images and detection sensitivities (DS) were compared among 12 images in subgroups classified by nodular diameters and densities. RESULTS GGN detectability at 120 kV-160 mA with IR was similar to that at 120 kV-80 mA with IR (0.614 mSv), as area under receiver operating characteristic curve was 0.798 ± 0.024 and 0.788 ± 0.025, respectively, and higher than six images acquired at 120 kV (p < 0.05). For nodules of -630 HU/8 mm, DS at 120 kV-10 mA without IR was 73.5 ± 6.0% and was similar to that by the other 11 data acquisition methods (p = 0.157). For nodules of -800 HU/10 mm, DS both at 120 kV-80 mA and 120 kV-160 mA without IR was improved by IR (56.3 ± 11.9%) (p < 0.05). CONCLUSION CDT demonstrated sufficient detectability for larger more-attenuated GGNs (>8 mm) even in the lowest radiation dose (0.17 mSv) and improved detectability for less-attenuated GGNs with the diameter of 10 mm at submillisievert with IR. Advances in knowledge: IR improved detectability for larger less-attenuated simulated GGNs on CDT.

Acute Mesenteric Ischemia: Multidetector CT Findings and Endovascular Management

Acute mesenteric ischemia is a rare life-threatening condition that accounts for approximately one in 1000 hospital admissions. The mortality rate is 50%-69% owing to the absence of specific symptoms and laboratory data, which makes early detection of this condition difficult. If the use of contrast material is possible, biphasic contrast material-enhanced multidetector computed tomography (CT) is the first-line imaging test for early diagnosis of the disease and for differentiation from other causes of acute abdomen. Multidetector CT can depict mesenteric ischemia, its underlying causes, and its severity. Mesenteric ischemia is classified as either acute or chronic. The causes of AMI include arterial embolism, arterial thrombosis, venous thrombosis, and nonocclusive mesenteric ischemia, among which arterial causes are far more common than venous causes. Recently, endovascular procedures such as thrombolysis, thrombectomy, thrombus fragmentation, and stent placement have been successfully and safely performed when the ischemia is reversible. Online DICOM image stacks are available for this article. ©RSNA, 2018.

Acceleration of small bowel motility after oral administration of dai-kenchu-to (TJ-100) assessed by cine magnetic resonance imaging

Dai-kenchu-to (TJ-100) is an herbal medicine used to shorten the duration of intestinal transit by accelerating intestinal movement. However, intestinal movement in itself has not been evaluated in healthy volunteers using radiography, fluoroscopy, and radioisotopes because of exposure to ionizing radiation. The purpose of this study was to evaluate the effect of TJ-100 on intestinal motility using cinematic magnetic resonance imaging (cine MRI) with a steady-state free precession sequence. Ten healthy male volunteers received 5 g of either TJ-100 or lactose without disclosure of the identity of the substance. Each volunteer underwent two MRI examinations after taking the substances (TJ-100 and lactose) on separate days. They drank 1200 mL of tap water and underwent cine MRI after 10 min. A steady-state free precession sequence was used for imaging, which was performed thrice at 0, 10, 20, 30, 40, and 50 min. The bowel contraction frequency and distention score were assessed. Wilcoxon signed-rank test was used, and differences were considered significant at a P-value <0.05. The bowel contraction frequency tended to be greater in the TJ-100 group and was significantly different in the ileum at 20 (TJ-100, 8.95 ± 2.88; lactose, 4.80 ± 2.92; P < 0.05) and 50 min (TJ-100, 9.45 ± 4.49; lactose, 4.45 ± 2.65; P < 0.05) between the groups. No significant differences were observed in the bowel distention scores. Cine MRI demonstrated that TJ-100 activated intestinal motility without dependence on ileum distention.

Sub-solid nodule detectability in seven observers of seventy-nine clinical cases: comparison between ultra-low-dose chest digital tomosynthesis with iterative reconstruction and chest radiography by receiver-operating characteristics analysis

PURPOSE To compare sub-solid nodules detectability (SSND) between ultra-low-dose chest digital tomosynthesis (ULD-CDT) with/without iterative reconstruction (IR) and chest radiography (CR) by using low-dose computed tomography (LDCT) as the standard of reference (SOR). MATERIALS AND METHODS Institutional Review Board approved this study and written informed consent was obtained. In a single visit, 79 subjects underwent ULD-CDT at 120 kV and 10 mA, CR and LDCT (effective dose: 0.171, 0.117 and 3.52 mSv, respectively). Sixty-three coronal images were reconstructed using CDT with/without IR. SOR as to SSN presence was determined based on LDCT images. Seven radiologists recorded SSN presence and locations by continuously-distributed rating. Receiver-operating characteristic (ROC) analysis was used to compare SSND of ULD-CDT with/without IR and CR, in total and subgroups classified by nodular longest diameter (LD) (> or < 9 mm) and mean CT attenuation value (CTAV) (> or < -600 Hounsfield of Unit (HU)). Detection sensitivity (DS) was compared among 4 groups classified by combination of the identical thresholds: nodular LD (9 mm) and mean CTAV (-600 HU) in each of ULD-CDT with/without IR and CR with Friedman and Wilcoxon signed rank test. RESULTS SSND for total 105 SSNs as well as larger SSNs with nodular LD of 9 mm or more at ULD-CDT with IR was higher than either that at ULD-CDT without IR or CR, as the areas under the ROC curve were 0.66 ± 0.02, 0.59 ± 0.01 and 0.52 ± 0.01, respectively (p < 0.05). DS at ULD-CDT with IR was 69.5 ± 10.8% in groups with larger (LD > 9 mm) and more-attenuated (>-600 HU) SSNs, and higher than in the other 3 groups (p < 0.05). CONCLUSION ULD-CDT with IR demonstrated better SSND than that without IR or CR, with increased DS for larger and more-attenuated SSNs compared with the remaining ones.

Adrenal obliteration by balloon-occluded retrograde venous ethanol injection in a swine model

Abstract Purpose: To evaluate the effects of adrenal obliteration by balloon-occluded retrograde venous ethanol injection. Material and methods: We inserted a micro-balloon catheter into the left adrenal vein of six pigs and retrogradely injected absolute ethanol (0.06 ml/kg) under balloon occlusion. Two pigs were sacrificed on day 3, 7, and 14 after the procedure, respectively. We evaluated adrenal cortical and medullary hormones of the left renal vein, venograms, magnetic resonance imaging scans obtained before and after the procedure, autopsy and microscopic findings, and the weight of the bilateral adrenal glands. Results: The hormone levels were extremely high on day 3 after the procedure. Post-procedure, partially-enhanced parenchyma and shaggy veins were observed. On the post-mortem examination, the left adrenal glands showed hemorrhage and adhesion on the third and seventh day and fatty proliferation 14 days after the procedure. Microscopic examination revealed hemorrhagic necrosis on day 3, inflammatory cell infiltration on day 7, and partial fibrosis 14 days after the procedure. The weight of the left adrenal gland on day 14 was lower than that of the right gland. Conclusions: This procedure elicited partial adrenal infarction with a high catecholamine concentration in the left renal vein.

Utility of MR imaging in the evaluation of colon cancer: emphasis on distinguishing tumor tissue from fibrosis and role of contrast media

T staging after neoadjuvant chemotherapy is less accurate than before it. According to a recent research regarding restaging locally advanced rectal cancer after preoperative chemoradiation using T2-weighted image (T2WI) and diffusion-weighted imaging (DWI), T stage was correctly predicted in 47–68% of the patients [3]. We agree with them that the administration of scopolamine butylbromide and periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) DWI could reduce motion artifact due to colonic peristalsis. However, we consider that DWI has difficulty in distinguishing tumor invasion from peritumoral desmoplastic reaction because the colon, especially the ascending, transverse, and descending colon, frequently contains gas, which prevents highly detailed DWI by susceptibility artifact. Therefore, we think that bowel preparation (e.g., the administration of warm tap water via rectal tube) improves the quality of DWI. T2WI is the most important sequence that evaluates T staging of rectal as well as colon cancer [2]. Yamada et al. reported that T2WI using 7.0-T MRI enabled clear differentiation of tumor tissue from fibrosis ex vivo MRI for gastric cancer [4]. The signal intensity on T2WI of fibrosis is lower than that of tumor tissue. High-resolution T2WI has the ability to distinguish colorectal cancer from fibrosis, but it needs further research. We stated that with respect to the T staging of colon cancers, the administration of contrast medium is not necessary [2]. However, we evaluated contrast-enhanced T1WI (CE-T1WI) on the phase to peak enhancement of the colon wall and did not assess delayed enhancement or perfusion MR imaging. Perfusion MRI can be used to determine increased microvascular status that reflects arteriovenous shunts or increased angiogenesis, which suggest a more aggressive tumor. Chemoradiotherapy for rectal cancer We appreciate the interest of Sivrioglu et al. in our article [1]. The peritumoral fibrosis is known as a desmoplastic reaction. It is a state of increasing fibroblasts and myofibroblasts in the interstitium with tumor invasion. The linear architecture of the fat indicated a desmoplastic reaction and T3 tumor in our study, but it was observed in one patient with T2 tumor [2]. This fibrosis results in overdiagnosis in T staging. Earlier research stated a speculation that perirectal fat represented a T2 tumor, whereas another one suggested an early T3 tumor. It is important and difficult to distinguish tumor invasion from fibrosis for accurate T staging, especially in discriminating a T2 (limited within the colon wall) from a T3 tumor (beyond the colon wall). Recent studies suggest that preoperative neoadjuvant chemotherapy for colon cancer is feasible and effective. As Sivrioglu et al. mentioned, we also think that MRI has a potential benefit of evaluating correct tumor invasion before neoadjuvant chemotherapy. Furthermore, it is expected that MRI plays a role in restaging locally advanced colon cancer after preoperative chemotherapy. However, chemotherapy induces changes such as inflammation and fibrosis, which makes it difficult to evaluate accurate tumor invasion and distinguish the tumor showing these changes. Therefore,

StatSensor‑i point‑of‑care creatinine analyzer may identify patients at high‑risk of contrast‑induced nephropathy

The current study assessed the accuracy of the StatSensor-i (STA) point-of-care creatinine analyzer prior to and following adjustment (offset correction) by linear regression scatter plots produced by the reference samples from patients and volunteers for detecting high risk of contrast-induced nephropathy in patients with an estimated glomerular filtration rate <45 ml/min/1.73 m2. Blood samples were obtained from 233 consecutive outpatients scheduled for contrast-enhanced CT studies. Of the 233 patients, 123 patient samples were evaluated prior to adjustment and the other 110 following adjustment. Serum creatinine levels and estimated glomerular filtration rate were measured using the analyzer and compared with the values returned by laboratory tests. Analysis was with the paired t-test, the Pearson correlation coefficient and Bland-Altman plotting. The sensitivity, specificity, positive and negative predictive values (PPV, NPV), and accuracy for detecting patients with an estimated glomerular filtration rate <45 ml/min/1.73 m2 were subsequently calculated. Mean serum creatinine levels measured with the analyzer were significantly higher than those returned by laboratory tests before (P<0.0001) and after adjustment (P<0.01). Following adjustment, the difference in serum creatinine values obtained with the STA analyzer and by laboratory methods did not exceed 0.3 mg/dl. Prior to adjustment, 9.7% of the samples were overdiagnosed as having an estimated glomerular filtration rate of <45 ml/min/1.73 m2; following adjustment, the overdiagnosis rate was 2.7%. The sensitivity, specificity, PPV, NPV and accuracy were 100, 89, 50, 100 and 90.2% before and 100, 96.3, 33.3, 100 and 96.4% after adjustment, respectively. With the adjusted point-of-care creatinine analyzer, estimated glomerular filtration rate may be reliably evaluated in the radiology suite.