Tumor lesion detection: when is integrated positron emission tomography/computed tomography more accurate than side-by-side interpretation of positron emission tomography and computed tomography?

OBJECTIVES: To determine if there is added value to oncology studies performed with a dedicated in-line positron emission tomography (PET)/computed tomography (CT) scanner as compared with PET read side by side with diagnostic CT (DCT). METHODS: Forty-one consecutive oncology patients referred for PET/CT who had contemporary DCT scans for review were enrolled. Body regions assessed on a DCT scan were assessed on PET/CT and by side-by-side reading of PET and DCT (SBS PET/DCT). Lesions identified on DCT, the CT portion of PET/CT, SBS PET/DCT, and the reading of fused PET/CT images were scored as benign or malignant. The PET portion of the PET/CT study was read by 2 teams: the first read the SBS PET/DCT scan and the other read the complete fused PET/CT scan. For discordant lesions, the final diagnosis was determined by pathologic findings (n = 6) or imaging follow-up (n = 21). RESULTS: Twenty-seven (16.1%) of the 168 lesions were discordant when comparing analysis of fused PET/CT and SBS PET/DCT. Sixteen (9.5%) were fundamentally discordant, and 11(6.6%) were discordant in degree of confidence. For all discordant lesions only, the sensitivity, specificity, negative predictive value, positive predictive value, and accuracy for PET/CT were 100%, 33%, 100%, 94%, and 78%, respectively, and for SBS PET/DCT, they were 38%, 50%, 19%, 73%, and 30%, respectively (P < 0.001 for sensitivity, P = not specific for specificity). The 2 main causes for misclassification on SBS PET/DCT were incorrect localization (n = 12) and changes occurring in the time gap between DCT and PET/CT (n = 4). CONCLUSIONS: In-line PET/CT offers better lesion localization in comparison to the visual fusion of PET and CT, especially for small lymph nodes, lesions adjacent to mobile organs, or lesions adjacent to the chest or abdominal wall.     

Benign or malignant?: differentiating breast lesions with computed tomography attenuation values on dynamic computed tomography mammography

OBJECTIVE: To evaluate enhancement effects of breast lesions with dynamic computed tomography (CT) and to determine characteristics to aid in differential diagnosis of benign and malignant lesions. METHODS: One hundred seventy-six women underwent preoperative dynamic CT, in which they were scanned with rapid injection of contrast media (3 mL/s) after 30 seconds and 2 minutes (early and delayed phases, respectively). The CT values and enhancement patterns of malignant lesions (n = 154) were compared with those of benign lesions (n = 22), and the cut point of CT values with the best validity was analyzed. RESULTS: The CT values of malignant lesions were higher than those of benign lesions in both phases (P < 0.0001). The cut point was determined to be 60 Hounsfield units (HU) in the early phase (44% validity, 90% sensitivity). Washout and plateau patterns were more commonly seen in the malignant group (73% specificity). CONCLUSIONS: The analysis of enhancement effects on CT may lead to more appropriate differentiation of benign and malignant lesions.     

FDG positron emission tomography/computed tomography studies of Wilms’ tumor

Purpose  

The purpose of this analysis was to evaluate the utility of FDG PET/CT scanning in patients with Wilms’ tumors.     

Drowning—post-mortem imaging findings by computed tomography

The aim of this study was to identify the classic autopsy signs of drowning in post-mortem multislice computed tomography (MSCT). Therefore, the post-mortem pre-autopsy MSCT- findings of ten drowning cases were correlated with autopsy and statistically compared with the post-mortem MSCT of 20 non-drowning cases. Fluid in the airways was present in all drowning cases. Central aspiration in either the trachea or the main bronchi was usually observed. Consecutive bronchospasm caused emphysema aquosum. Sixty percent of drowning cases showed a mosaic pattern of the lung parenchyma due to regions of hypo- and hyperperfused lung areas of aspiration. The resorption of fresh water in the lung resulted in hypodensity of the blood representing haemodilution and possible heart failure. Swallowed water distended the stomach and duodenum; and inflow of water filled the paranasal sinuses (100%). All the typical findings of drowning, except Paltau’s spots, were detected using post-mortem MSCT, and a good correlation of MSCT and autopsy was found. The advantage of MSCT was the direct detection of bronchospasm, haemodilution and water in the paranasal sinus, which is rather complicated or impossible at the classical autopsy.     

Sacral abnormalities—computed tomography versus conventional radiography

Seventeen examples of different pathologic conditions, including malignant and benign tumors, and inflammatory, traumatic, and congenital lesions involving the sacrum, are presented. The value of computed tomography is compared with that of conventional methods with respect to diagnostic evaluation and clinical management of these patients. Computed tomography proved to be more accurate in delineating the extent of bony lesions, diagnosing adjacent soft tissue involvement, evaluating the progress of a lesion, and defining the approach for biopsy of a sacral lesion or determining the feasibility of surgery.     

Evaluation of Wegener’s granulomatosis using 18F-fluorodeoxyglucose positron emission tomography/computed tomography

Objective

Wegener’s granulomatosis (WG) is a relatively rare disease characterized by granulomatous necrotizing vasculitis that primarily involves small- and medium-sized vessels. Systemic findings observed on ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) have not been well reported. The purpose of this study was to evaluate the FDG PET/CT imaging in the diagnosis and follow-up of patients with WG.

Materials and methods

Thirteen FDG PET/CT images obtained for 8 patients (2 men and 6 women) with WG were retrospectively analyzed. Of these, 6 were performed for diagnosis, 2 for restaging and follow-up, and 5 for assessment of treatment efficacy. Maximum standardized uptake values (max SUVs) and visual analyses were used to interpret the FDG PET/CT images. In addition, nonenhanced CT findings obtained during FDG PET/CT were described.

Results

WG lesions of the upper respiratory tract and lung were more clearly detected by FDG PET/CT fusion imaging than by nonenhanced CT alone, and all of the active lesions showed decreased FDG uptake after treatment. In addition, FDG PET/CT can provide complementary information to indicate biopsy site based on FDG uptakes.

Conclusions

FDG PET/CT is a feasible modality for evaluating lesion activities, therapeutic monitoring, and follow-up of WG. Furthermore, biopsy sites of WG lesions may be determined by FDG PET/CT.     

Low-dose computed tomography via spatially adaptive Monte–Carlo reconstruction

Low-dose computed tomography (CT) reduces radiation exposure but decreases signal-to-noise ratio (SNR) and diagnostic capabilities. Noise compensation can improve SNR so low-dose CT can provide valuable information for diagnosis without risking patient radiation exposure. In this study, a novel noise-compensated CT reconstruction method that uses spatially adaptive Monte–Carlo sampling to produce noise-compensated reconstructions is investigated. By adapting to local noise statistics, a non-parametric estimation of the noise-free image is computed that successfully handles non-stationary noise found in low-dose CT images. Using phantom and real low-dose CT images, effective noise suppression is shown to be accomplished while maintaining structures and details.     

Postmortem computed tomography findings in the thorax – Experimental evaluation

ObjectiveExperimental fatal models were prepared to investigate the time-related course of lung changes using postmortem CT (PMCT). This study was approved by our institutional animal ethics committee.Materials and methodsTwenty-four NZW rabbits (female 24, 2.30–4.30 (mean 3.10) kg) were divided into 4 fatal groups; drowning, hypothermia, bag suffocation, and Potassium Chloride intravenous (control) group. All individuals were examined by CT (Aquilion CX, Toshiba, Japan) on postmortem time course until detection of putrefaction air. The percent of aerated lung volume (%ALV = 100 * (ALV/total lung volume)) was measured and the pleural space fluid was investigated by axial imaging. A paired t-test and Bonferroni/Dunn study were employed for statistical evaluation.ResultsIn intra-group analysis, the %ALV showed statistically different periods compared with each pre-image: 4–48 h in control, 1–24 h in drowning, 5–6 h in hypothermia, and 1–4 h in bag suffocation. In inter-group comparison (compared with control group), the %ALV increased in suffocation and decreased in drowning within 12 h. The %ALV remained significantly high in hypothermia until 24 h. The earliest detection times of pleural space fluid collection were different in each group: control (20 h), drowning (18 h), suffocation (36 h), and hypothermia (95 h).ConclusionThe lung hypostasis and the appearance of pleural space fluid collection presented differently in individual causes of death and depending on the postmortem time.     

Does computed tomography permeability predict hemorrhagic transformation after ischemic stroke?

AIM: To use perfusion-derived permeability-surface area product maps to predict hemorrhagic transformation following thrombolytic treatment for acute ischemic stroke. METHODS: We retrospectively analyzed our prospectively kept acute stroke database over five consecutive months for patients with symptoms of acute ischemic stroke (AIS) who had computed tomography (CT) perfusion (CTP) done at arrival. Patients included in the analyses also had to have a follow-up CT. The permeability-surface area product maps (PS) was calculated for the side of the ischemia and/or infarction and for the contralateral unaffected side at the same level. The cerebral blood flow map was used to delineate the ischemic territory. Next, a region of interest was drawn at the centre of this territory on the PS parametric map. Finally, a mirror region of interest was created on the contralateral side at the same level. The relative permeability-surface area product maps (rPS) provided an internal control and was calculated as the ratio of the PS on the side of the AIS to the PS on the contralateral side. A student t-test was performed after log conversion of rPS between patients with and without hemorrhagic transformation. Log conversion was used to convert the data into normal distribution to use t-test. For the group of patients who experienced intracranial bleed, a student t-test was performed between those with only petechial hemorrhage and those with more severe parenchymal hematoma with subarachnoid haemorrhage. RESULTS: Of 84 patients with AIS and CTP at admission, only 42 patients had a follow-up CT. The rPS derived using the normal side as the internal control was significantly higher (P = 0.003) for the 15 cases of hemorrhagic transformation (1.71 + 1.64) compared to 27 cases that did not have any (1.07 + 1.30). Patients with values above the overall mean rPS of 1.3 had an increased likelihood of subsequent hemorrhagic transformation. The sensitivity of using this score to predict hemorrhagic transformation was 71.4, the specificity was 78.6, with a positive predictive value of 62.5 and negative predictive value of 84.6. The accuracy was 76.2. The odds ratio of an event occurring with such an rPS was 9.2. Of the 15 cases of hemorrhagic transformation, there was no difference (P = 0.35) in the rPS between the eight cases of petechial and the seven cases of more severe hemorrhagic events. CONCLUSION: Pretreatment PS can predict the occurrence of hemorrhagic transformation on follow-up of AIS patients with relatively high sensitivity, specificity, positive and negative predictive value.     

Leucocyte scintigraphy or computed tomography for the febrile post-operative patient?

Objective: The optimal initial investigation for the post-operative patient with suspected occult intra-abdominal sepsis is controversial, although the diagnostic accuracy of a variety of techniques is known. Our objective is to determine which investigation has the greatest positive effect on patient management. Methods and patients: We reviewed 67 consecutive post-operative patients investigated for suspected occult sepsis retrospectively and analysed the sequence of investigations required to achieve the diagnosis depending on the choice of initial investigation, and the interval between initiating investigations and performing definitive percutaneous drainage. Results: Forty patients had scintigraphy as the initial investigation and 21 of these went on to require CT. None of the 27 patients who had CT as the initial investigation required any other imaging (X² = 20.6, P < 0.0001) and appropriate percutaneous drainage was ofered immediately. Conversely, the average interval to drainage in those who had scintigraphy first was 3.1 days. Fourteen out of 20 patients (70%) who had scintigraphy as the initial investigation following recent surgery, and 7 of 20 (35%) following old surgery, needed subsequent CT. None of the 20 and 7 patients in the recent and old surgery groups respecitvely who had CT initially required further imaging. Conclusion: Our results suggest recommending CT as the initial investigation in the early post-operative period as this will reduce the total number of investigations required to achieve the diagnosis and the time to definitive drainage. In the late post-operative period, scintigraphy will resolve the majority of problems.     

Optimisation of multislice computed tomography protocols in angio–CT examinations

PURPOSE: The aim of this paper is to explain a general procedure for the optimisation of multislice computed tomography (MSCT) protocols. MATERIALS AND METHODS: Four angio-CT protocols with a GE LightSpeed Plus 4-slice CT scanner were considered. Effective doses were computed for a sample of patients. First the dose was optimised for arterial-phase scans on a standard patient and adapted to the weight of individual patients with a scaling factor. RESULTS: The mean effective dose for an angio-CT examination ranged from 18.8 mSv to 28.8 mSv, depending on the protocol adopted. Following the optimisation procedure, we drew up a table indicating tube current values for each patient weight. Calculation of the effective dose before and after the optimisation procedure revealed a dose reduction of about 40%. CONCLUSIONS: Angio-CT examinations deliver high doses, but these doses can be reduced without affecting image quality.     

Can postmortem computed tomography detect antemortem hypoxic–ischemic encephalopathy?

The purpose of this study was to evaluate the usefulness of brain postmortem computed tomography (PMCT) findings for the detection of global hypoxia or hypoperfusion leading to hypoxic–ischemic encephalopathy (HIE) prior to death. Cadavers of individuals who died from non-traumatic causes were subjected to PMCT and pathological autopsy. Cases with an episode of cardiopulmonary arrest, hypoxia, or hypoperfusion that required intensive respiratory management at least 24 h before death and exhibited findings of HIE in conventional autopsy (HIE group, n = 6) were compared with those without such episodes prior to death (control group; overall, n = 37; age-matched, n = 8) with regard to four parameters: (1) width of the central sulcus (CS), (2) attenuation difference at the basal ganglia (BG) level, (3) attenuation difference between cerebral gray matter (GM) and cerebral white matter (WM), and (4) attenuation difference between cerebellar GM and cerebral GM. The results revealed significant differences in the width of the CS (P < 0.001), attenuation difference at the BG level (P < 0.001), and attenuation difference between cerebral GM and cerebral WM (P = 0.009) between the HIE group and the overall control group. When the age-matched control group and the HIE group were compared, there was a significant difference in the width of the CS (P = 0.026) and attenuation difference at the BG level (P < 0.001). Our results suggest that effacement of the sulcus of the cerebral hemisphere and the loss of contrast at the BG level on brain PMCT indicate the existence of HIE prior to death.     

Is contrast material needed after treatment of malignant lymphoma in positron emission tomography/computed tomography?

Purpose  

Positron emission tomography (PET)/computed tomography (CT) with ¹⁸F-fluorodeoxyglucose is widely used for post-therapeutic surveillance of malignant lymphoma. Debate still exists as to whether intravenous contrast media during the CT stage of a PET/CT scan should be used. The purpose of this study was to investigate the clinical value of contrast agent in PET/CT in patients with lymphoma following treatment.     

Accuracy in contouring of small and low contrast lesions: Comparison between diagnostic quality computed tomography scanner and computed tomography simulation scanner—A phantom study

To evaluate the accuracy in detection of small and low-contrast regions using a high-definition diagnostic computed tomography (CT) scanner compared with a radiotherapy CT simulation scanner. A custom-made phantom with cylindrical holes of diameters ranging from 2–9 mm was filled with 9 different concentrations of contrast solution. The phantom was scanned using a 16-slice multidetector CT simulation scanner (LightSpeed RT16, General Electric Healthcare, Milwaukee, WI) and a 64-slice high-definition diagnostic CT scanner (Discovery CT750 HD, General Electric Healthcare). The low-contrast regions of interest (ROIs) were delineated automatically upon their full width at half maximum of the CT number profile in Hounsfield units on a treatment planning workstation. Two conformal indexes, CI_in, and CI_out, were calculated to represent the percentage errors of underestimation and overestimation in the automated contours compared with their actual sizes. Summarizing the conformal indexes of different sizes and contrast concentration, the means of CI_in and CI_out for the CT simulation scanner were 33.7% and 60.9%, respectively, and 10.5% and 41.5% were found for the diagnostic CT scanner. The mean differences between the 2 scanners' CI_in and CI_out were shown to be significant with p < 0.001. A descending trend of the index values was observed as the ROI size increases for both scanners, which indicates an improved accuracy when the ROI size increases, whereas no observable trend was found in the contouring accuracy with respect to the contrast levels in this study. Images acquired by the diagnostic CT scanner allow higher accuracy on size estimation compared with the CT simulation scanner in this study. We recommend using a diagnostic CT scanner to scan patients with small lesions (<1 cm in diameter) for radiotherapy treatment planning, especially for those pending for stereotactic radiosurgery in which accurate delineation of small-sized, low-contrast regions is important for dose calculation.     

Size-specific dose estimates: Localizer or transverse abdominal computed tomography images?

AIM: To investigate effect of body dimensions obtained from localizer radiograph and transverse abdominal computed tomography (CT) images on Size Specific Dose Estimate.METHODS: This study was approved by Institutional Review Board and was compliant with Health Insurance Portability and Accountability Act. Fifty patients with abdominal CT examinations (58 ± 13 years, Male:Female 28:22) were included in this study. Anterior-posterior (AP) and lateral (Lat) diameters were measured at 5 cm intervals from the CT exam localizer radiograph (simple X-ray image acquired for planning the CT exam before starting the scan) and transverse CT images. Average of measured AP and Lat diameters, as well as maximum, minimum and mid location AP and Lat were measured on both image sets. In addition, off centering of patients from the gantry iso-center was calculated from the localizers. Conversion factors from American Association of Physicists in Medicine (AAPM) report 204 were obtained for AP, Lat, AP + Lat, and effective diameter (√ AP * Lat) to determine size specific dose estimate (SSDE) from the CT dose index volume (CTDI_vol) recorded from the dose reports. Data were analyzed using SPSS v19.RESULTS: Total number of 5376 measurements was done. In some patients entire body circumference was not covered on either projection radiograph or transverse CT images; hence accurate measurement of AP and Lat diameters was not possible in 11% (278/2488) of locations. Forty one patients were off-centered with mean of 1.9 ± 1.8 cm (range: 0.4-7 cm). Conversion factors for attained diameters were not listed on AAPM look-up tables in 3% (80/2488) of measurements. SSDE values were significantly different compared to CTDI_vol, ranging from 32% lower to 74% greater than CTDI_vol.CONCLUSION: There is underestimation and overestimation of dose comparing SSDE values to CTDI_vol. Localizer radiographs are associated with overestimation of patient size and therefore underestimation of SSDE.     

Respiratory gated multidetector computed tomography: Applicable for diagnostic abdominal imaging?

Purpose

To evaluate the ability and accuracy of a respiratory gated technique used with contrast enhanced MDCT of the upper abdomen with focus on diagnostic image quality and depiction of organs and major vessels.

Materials and methods

Forty-five adult patients who were referred to our institution for follow-up dynamic contrast enhanced abdominal CT imaging were included in this study. Respiratory gated CT scans were performed with the use of a dedicated hardware. A multiphasic CT scan was performed for each patient. Respiratory gated images were obtained between early arterial and portal venous phases during free breathing. Images of respiratory gated (RG) and breathhold (BH) phases were compared qualitatively and quantitatively by two radiologists. Definitive statistical methods were used for evaluating the scoring data, while Mann Whitney U test was used for comparison. Statistical significance was accepted for p values <0.05.

Results

Statistical significant difference was found for comparison of scores regarding luminal opacification and contoural integrity of intrahepatic vascular structures with scores of RG scans rated poor to moderate (e.g. 2.86 ± 1.07 for luminal opacification of intrahepatic portal veins as well as border detectability) in comparison to scores of BH scans rated good to excellent (e.g. 1.37 ± 1.31 for luminal opacification, 1.35 ± 1.28 for border detectability of intrahepatic portal veins, p < 0.001). Furthermore, statistical significant differences were found for general image noise levels (p < 0.001).

Conclusions

Further technical advances of RG technique could enable routine use of this technique for selected patient groups.