Body CT and oncologic imaging

Deep Learning Radiomics Model of Contrast-Enhanced CT for Differentiating the Primary Source of Liver Metastases

RATIONALE AND OBJECTIVES

To develop and validate a deep learning radiomics (DLR) model based on contrast-enhanced computed tomography (CT) to identify the primary source of liver metastases.

MATERIALS AND METHODS

In total, 657 liver metastatic lesions, including breast cancer (BC), lung cancer (LC), colorectal cancer (CRC), gastric cancer (GC), and pancreatic cancer (PC), from 428 patients were collected at three clinical centers from January 2018 to October 2023 series. The lesions were randomly assigned to the training and validation sets in a 7:3 ratio. An additional 112 lesions from 61 patients at another clinical center served as an external test set. A DLR model based on contrast-enhanced CT of the liver was developed to distinguish the five pathological types of liver metastases. Stepwise classification was performed to improve the classification efficiency of the model. Lesions were first classified as digestive tract cancer (DTC) and non-digestive tract cancer (non-DTC). DTCs were divided into CRC, GC, and PC and non-DTCs were divided into LC and BC. To verify the feasibility of the DLR model, we trained classical machine learning (ML) models as comparison models. Model performance was evaluated using accuracy (ACC) and area under the receiver operating characteristic curve (AUC).

RESULTS

The classification model constructed by the DLR algorithm showed excellent performance in the classification task compared to ML models. Among the five categories task, highest ACC and average AUC were achieved at 0.563 and 0.796 in the validation set, respectively. In the DTC and non-DTC and the LC and BC classification tasks, AUC was achieved at 0.907 and 0.809 and ACC was achieved at 0.843 and 0.772, respectively. In the CRC, GC, and PC classification task, ACC and average AUC were the highest, at 0.714 and 0.811, respectively.

CONCLUSION

The DLR model is an effective method for identifying the primary source of liver metastases.

Value of Clinical Information on Radiology Reports in Oncological Imaging

Radiological reporting errors have a direct negative impact on patient treatment. The purpose of this study was to investigate the contribution of clinical information (CI) in radiological reporting of oncological imaging and the dependence on the radiologists’ experience level (EL). Sixty-four patients with several types of carcinomas and twenty patients without tumors were enrolled. Computed tomography datasets acquired in primary or follow-up staging were independently analyzed by three radiologists (R) with different EL (R1: 15 years; R2: 10 years, R3: 1 year). Reading was initially performed without and 3 months later with CI. Overall, diagnostic accuracy and sensitivity for primary tumor detection increased significantly when receiving CI from 77% to 87%; p = 0.01 and 73% to 83%; p = 0.01, respectively. All radiologists benefitted from CI; R1: 85% vs. 92%, p = 0.15; R2: 77% vs. 83%, p = 0.33; R3: 70% vs. 86%, p = 0.02. Overall, diagnostic accuracy and sensitivity for detecting lymphogenous metastases increased from 80% to 85% (p = 0.13) and 42% to 56% (p = 0.13), for detection of hematogenous metastases from 85% to 86% (p = 0.61) and 46% to 60% (p = 0.15). Specificity remained stable (>90%). Thus, CI in oncological imaging seems to be essential for correct radiological reporting, especially for residents, and should be available for the radiologist whenever possible.

Chemokine receptor 4 targeted protein MRI contrast agent for early detection of liver metastases

Liver metastases often progress from primary cancers including uveal melanoma (UM), breast, and colon cancer. Molecular biomarker imaging is a new non-invasive approach for detecting early stage tumors. Here, we report the elevated expression of chemokine receptor 4 (CXCR4) in liver metastases in UM patients and metastatic UM mouse models, and development of a CXCR4-targeted MRI contrast agent, ProCA32.CXCR4, for sensitive MRI detection of UM liver metastases. ProCA32.CXCR4 exhibits high relaxivities (r ₁ = 30.9 mM^-1 s^-1, r ₂ = 43.2 mM^-1 s^-1, 1.5 T; r ₁ = 23.5 mM^-1 s^-1, r ₂ = 98.6 mM^-1 s^-1, 7.0 T), strong CXCR4 binding (K _d = 1.10 ± 0.18 μM), CXCR4 molecular imaging capability in metastatic and intrahepatic xenotransplantation UM mouse models. ProCA32.CXCR4 enables detecting UM liver metastases as small as 0.1 mm³. Further development of the CXCR4-targeted imaging agent should have strong translation potential for early detection, surveillance, and treatment stratification of liver metastases patients.

Orthopedic metallic hardware in routine abdomino-pelvic CT scans: occurrence and clinical significance

PURPOSE

To study the occurrence of orthopedic metallic hardware in routine abdomen/pelvic computed tomography (CT) scans and their impact on image quality (IQ) and diagnostic evaluation.

MATERIAL AND METHODS

In this retrospective single institution study, we analyzed 3500 consecutive abdomen/pelvis CT scans for occurrence of orthopedic metallic hardware. In the cohort of patients with metallic hardware detected on CT scans, subjective and objective IQ analysis was performed to estimate diagnostic acceptability (DA, 4-point scale), subjective noise (SN, 3-point scale), presence of artifacts (PA, 4-point scale) and objective noise. The clinical significance of metallic hardware was determined by evaluating the impact of artifacts on radiological diagnosis according to the clinical indication and disease type.

RESULTS

Orthopedic metallic hardware was encountered in 4.97% of abdomino-pelvic CT scans (n = 174/3500), and artifacts related to the hardware in the region of clinical interest were identified in 82% (n = 144/174) of scans. The overall mean DA was 2.66 (n = 174), and it was severely limited (score < 2) in 32% of cases particularly affecting patients with bilateral hip implants (92.6%, n = 25/27). The artifacts due to hardware significantly limited diagnostic evaluation in 58.6% of cases (PA score ≥ 3), and the image noise was unacceptable in 71% of cases (SN score > 2) in the region of clinical interest.

CONCLUSION

Orthopedic metallic hardware is encountered in nearly 5% of abdomino-pelvic CT scans and causes significant image degradation limiting diagnostic evaluation in the region of clinical interest.

CT Image-based Decision Support System for Categorization of Liver Metastases Into Primary Cancer Sites: Initial Results

RATIONALE AND OBJECTIVES

This study aimed to provide decision support for the human expert, to categorize liver metastases into their primary cancer sites. Currently, once a liver metastasis is detected, the process of finding the primary site is challenging, time-consuming, and requires multiple examinations. The proposed system can support the human expert in localizing the search for the cancer source by prioritizing the examinations to probable cancer sites.

MATERIALS AND METHODS

The suggested method is a learning-based approach, using computed tomography (CT) data as the input source. Each metastasis is circumscribed by a radiologist in portal phase and in non-contrast CT images. Visual features are computed from these images, combined into feature vectors, and classified using support vector machine classification. A variety of different features were explored and tested. A leave-one-out cross-validation technique was conducted for classification evaluation. The methods were developed on a set of 50 lesion cases taken from 29 patients.

RESULTS

Experiments were conducted on a separate set of 142 lesion cases taken from 71 patients with four different primary sites. Multiclass categorization results (four classes) achieved low accuracy results. However, the proposed system was found to provide promising results of 83% and 99% for top-2 and top-3 classification tasks, respectively. Moreover, when compared to the experts' ability to distinguish the different metastases, the system shows improved results.

CONCLUSIONS

Automated systems, such as the one proposed, show promising new results and demonstrate new capabilities that, in the future, will be able to provide decision and treatment support for radiologists and oncologists, toward more efficient detection and treatment of cancer.

Automatic liver tumor segmentation on computed tomography for patient treatment planning and monitoring

Segmentation of liver tumors from Computed Tomography (CT) and tumor burden analysis play an important role in the choice of therapeutic strategies for liver diseases and treatment monitoring. In this paper, a new segmentation method for liver tumors from contrast-enhanced CT imaging is proposed. As manual segmentation of tumors for liver treatment planning is both labor intensive and time-consuming, a highly accurate automatic tumor segmentation is desired. The proposed framework is fully automatic requiring no user interaction. The proposed segmentation evaluated on real-world clinical data from patients is based on a hybrid method integrating cuckoo optimization and fuzzy c-means algorithm with random walkers algorithm. The accuracy of the proposed method was validated using a clinical liver dataset containing one of the highest numbers of tumors utilized for liver tumor segmentation containing 127 tumors in total with further validation of the results by a consultant radiologist. The proposed method was able to achieve one of the highest accuracies reported in the literature for liver tumor segmentation compared to other segmentation methods with a mean overlap error of 22.78 % and dice similarity coefficient of 0.75 in 3Dircadb dataset and a mean overlap error of 15.61 % and dice similarity coefficient of 0.81 in MIDAS dataset. The proposed method was able to outperform most other tumor segmentation methods reported in the literature while representing an overlap error improvement of 6 % compared to one of the best performing automatic methods in the literature. The proposed framework was able to provide consistently accurate results considering the number of tumors and the variations in tumor contrast enhancements and tumor appearances while the tumor burden was estimated with a mean error of 0.84 % in 3Dircadb dataset.

Feasibility of Using Volumetric Contrast-Enhanced Ultrasound with a 3-D Transducer to Evaluate Therapeutic Response after Targeted Therapy in Rabbit Hepatic VX2 Carcinoma

The aim of this study was to assess the feasibility of using dynamic contrast-enhanced ultrasound (DCE-US) with a 3-D transducer to evaluate therapeutic responses to targeted therapy. Rabbits with hepatic VX2 carcinomas, divided into a treatment group (n = 22, 30 mg/kg/d sorafenib) and a control group (n = 13), were evaluated with DCE-US using 2-D and 3-D transducers and computed tomography (CT) perfusion imaging at baseline and 1 d after the first treatment. Perfusion parameters were collected, and correlations between parameters were analyzed. In the treatment group, both volumetric and 2-D DCE-US perfusion parameters, including peak intensity (33.2 ± 19.9 vs. 16.6 ± 10.7, 63.7 ± 20.0 vs. 30.1 ± 19.8), slope (15.3 ± 12.4 vs. 5.7 ± 4.5, 37.3 ± 20.4 vs. 15.7 ± 13.0) and area under the curve (AUC; 1004.1 ± 560.3 vs. 611.4 ± 421.1, 1332.2 ± 708.3 vs. 670.4 ± 388.3), had significantly decreased 1 d after the first treatment (p = 0.00). In the control group, 2-D DCE-US revealed that peak intensity, time to peak and slope had significantly changed (p < 0.05); however, volumetric DCE-US revealed that peak intensity, time-intensity AUC, AUC during wash-in and AUC during wash-out had significantly changed (p = 0.00). CT perfusion imaging parameters, including blood flow, blood volume and permeability of the capillary vessel surface, had significantly decreased in the treatment group (p = 0.00); however, in the control group, peak intensity and blood volume had significantly increased (p = 0.00). It is feasible to use DCE-US with a 3-D transducer to predict early therapeutic response after targeted therapy because perfusion parameters, including peak intensity, slope and AUC, significantly decreased, which is similar to the trend observed for 2-D DCE-US and CT perfusion imaging parameters.

Automated method for detection and segmentation of liver metastatic lesions in follow-up CT examinations

This paper presents a fully automated method for detection and segmentation of liver metastases in serial computed tomography (CT) examinations. Our method uses a given two-dimensional baseline segmentation mask for identifying the lesion location in the follow-up CT and locating surrounding tissues, using nonrigid image registration and template matching, in order to reduce the search area for segmentation. Adaptive region growing and mean-shift clustering are used to obtain the lesion segmentation. Our database contains 127 cases from the CT abdomen unit at Sheba Medical Center. Development of the methodology was conducted using 22 of the cases, and testing was conducted on the remaining 105 cases. Results show that 94 of the 105 lesions were detected, for an overall matching rate of 90% making the correct RECIST 1.1 assessment in 88% of the cases. The average Dice index was [Formula: see text], the average sensitivity was [Formula: see text], and the positive predictive value was [Formula: see text]. In 92% of the rated cases, the results were classified by the radiologists as acceptable or better. The segmentation performance, matching rate, and RECIST assessment results hence appear promising.

Rapid detection of bone metastasis at thoracoabdominal CT: accuracy and efficiency of a new visualization algorithm

PURPOSE

To retrospectively assess the use of a combination of cancellous bone reconstructions (CBR) and multiplanar reconstructions (MPRs) for the detection of bone metastases at thoracoabdominal computed tomography (CT) compared with the use of MPRs alone.

MATERIALS AND METHODS

The study was approved by the local institutional review board. Included were 156 consecutive patients with confirmed cancer who underwent a whole-body positron emission tomography (PET)/CT examination for clinical purposes (93 male and 63 female patients; mean age ± standard deviation, 59.8 years ± 14.9; range, 11-85 years). Only the CT images were processed with the CBR algorithm, which segments the bones and removes the cortical layer from the images. The PET images served as part of the reference standard. Images from 15 patients were used as a training set. Four radiologists independently evaluated images of half of the remaining 141 patients by using CBRs and MPRs together, and the other half by using MPRs only. Radiologists were blinded to patient names, and patient order was randomized. Results for detection rates and reporting time were recorded and compared with a standard of reference for each patient that was created by one senior radiologist and one nuclear medicine specialist by using all available CT and PET data, CBRs, and follow-up examinations. General estimation equations were used for statistical analysis.

RESULTS

There were 349 lesions found in 103 patients, with 203 classified as malignant. Each patient was assessed by two readers per method, leading to a total of 698 lesions. The detection rate for all bone lesions was 35% (247 of 698) for MPRs and 74% (520 of 698) when CBRs and MPRs were used together, which was significantly higher (P < .001). The average reading time decreased from 85 to 43 seconds (P < .001) when both reconstructions were used.

CONCLUSION

Advanced visualization of cancellous bone significantly increased the detection of bone metastases and reduced the time for interpretation.

A radiologist's guide to treatment response criteria in oncologic imaging: anatomic imaging biomarkers

OBJECTIVE

The purpose of this article is to describe the imaging biomarkers of treatment response and provide an overview of anatomic imaging biomarkers.

CONCLUSION

Imaging biomarkers of treatment response have evolved into the primary endpoint of response in most phase 2 studies. Anatomic imaging biomarkers are applied to depict change in tumor size in response to treatment and are currently the most commonly applied method of treatment response evaluation.

Tumor burden analysis on computed tomography by automated liver and tumor segmentation

The paper presents the automated computation of hepatic tumor burden from abdominal computed tomography (CT) images of diseased populations with images with inconsistent enhancement. The automated segmentation of livers is addressed first. A novel 3-D affine invariant shape parameterization is employed to compare local shape across organs. By generating a regular sampling of the organ's surface, this parameterization can be effectively used to compare features of a set of closed 3-D surfaces point-to-point, while avoiding common problems with the parameterization of concave surfaces. From an initial segmentation of the livers, the areas of atypical local shape are determined using training sets. A geodesic active contour corrects locally the segmentations of the livers in abnormal images. Graph cuts segment the hepatic tumors using shape and enhancement constraints. Liver segmentation errors are reduced significantly and all tumors are detected. Finally, support vector machines and feature selection are employed to reduce the number of false tumor detections. The tumor detection true position fraction of 100% is achieved at 2.3 false positives/case and the tumor burden is estimated with 0.9% error. Results from the test data demonstrate the method's robustness to analyze livers from difficult clinical cases to allow the temporal monitoring of patients with hepatic cancer.

Blind spots at oncological CT: lessons learned from PET/CT

Improved accuracy in oncological computed tomography (CT) could lead to a decrease in morbidity and improved survival for oncology patients. Visualization of metabolic activity using the glucose analogue [¹⁸F]fluorodeoxyglucose (FDG) in combination with the high anatomic resolution of CT in an integrated positron emission tomography (PET)/CT examination has the highest sensitivity and specificity for the detection of primary and metastatic lesions. However, PET/CT costs are high and patient access is limited; thus CT remains the primary imaging modality in oncology patients. We have noted that subtle lesions are more easily detected on CT by radiologists with PET/CT experience. We aimed to provide a brief review of the literature with comparisons of multi-detector computed tomography (MDCT) and PET/CT in primary and metastatic disease with an emphasis on findings that may be overlooked on MDCT in cancer of the breast, lung, colon, and ovaries, and in melanoma, as well as thrombosis in oncology patients. We further reviewed our experience for illustrative comparisons of PET/CT and MDCT studies. Experience in interpreting conventional CT scans alongside PET/CT can help the reader develop an appreciation for the subtle appearance of some lesions on CT that might otherwise be missed. This could improve detection rates, reduce errors, and improve patient management.

F18-fluorodeoxyglucose-positron emission tomography and computed tomography is not accurate in preoperative staging of gastric cancer

PURPOSE

To investigate the clinical benefits of F18-fluorodeoxyglucose-positron emission tomography and computed tomography ((18)F-FDG-PET/CT) over multi-detector row CT (MDCT) in preoperative staging of gastric cancer.

METHODS

FDG-PET/CT and MDCT were performed on 78 patients with gastric cancer pathologically diagnosed by endoscopy. The accuracy of radiologic staging retrospectively was compared to pathologic result after curative resection.

RESULTS

Primary tumors were detected in 51 (65.4%) patients with (18)F-FDG-PET/CT, and 47 (60.3%) patients with MDCT. Regarding detection of lymph node metastasis, the sensitivity of FDG-PET/CT was 51.5% with an accuracy of 71.8%, whereas those of MDCT were 69.7% and 69.2%, respectively. The sensitivity of (18)F-FDG-PET/CT for a primary tumor with signet ring cell carcinoma was lower than that of (18)F-FDG-PET/CT for a primary tumor with non-signet ring cell carcinoma (35.3% vs. 73.8%, P < 0.01).

CONCLUSION

Due to its low sensitivity, (18)F-FDG-PET/CT alone shows no definite clinical benefit for prediction of lymph node metastasis in preoperative staging of gastric cancer.

Tumor response evaluation in oncology: current update

Quantification of tumor burden and assessment of changes in tumor size after chemotherapy are commonly performed to evaluate treatment response in oncology trials. Validation and adoption of different criteria have been attempted in the past to achieve uniformity in scanning techniques and measurement metrics so that comparison of different oncological trials is feasible. Response assessment of solid tumors is usually consisted of either bidimensional (World Health Organization criteria) or unidimensional (Response Evaluation Criteria in Solid Tumors [RECIST] guidelines) measurement of tumors before and after chemotherapy. RECIST 1.1 criteria have been recently published. In this article, we try to provide a comprehensive review of the tumor response evaluation guidelines that were recently updated in attempts to overcome limitations of the previous criteria as well as incorporate recent advances in imaging techniques.

Morphological analysis of pancreatic adenocarcinoma on multidetector row computed tomography: implications for treatment response evaluation

OBJECTIVES

Response Evaluation Criteria in Solid Tumors (RECIST) guidelines assume spherical shape of tumors. Morphology of pancreatic adenocarcinoma (PAC) on multidetector row computed tomography was investigated to evaluate the applicability of RECIST guidelines.

METHODS

Study population comprised 16 patients with histologically confirmed localized PAC enrolled in a phase II clinical trial of chemoradiation. Pancreatic adenocarcinomas were segmented on baseline and follow-up multidetector row computed tomography with commercially available software. Tumor volumes (mL), RECIST diameter (mm), volume equivalent sphere diameter (VESD, mm), maximum 3-dimensional diameter (M3DD, mm), and elongation value were obtained. RECIST diameter, VESD and M3DD of the tumors at baseline and follow-up were compared to determine differences. Elongation values were analyzed. The significance level was set at P less than 0.05.

RESULTS

Mean volume, RECIST diameter, VESD, M3DD, and elongation for baseline versus follow-up studies were 23.12 mL versus 19.43 mL (P > 0.05), 41.86 mm versus 39.35 mm (P > 0.05), 33.14 mm versus 32.1 mm (P > 0.05), 51.76 mm versus 51.73 mm (P > 0.05), and 0.67 versus 0.76 (P > 0.05), respectively. There was a significant difference at baseline and follow-up between RECIST diameter, VESD, and M3DD (P < 0.05, in all instances).

CONCLUSIONS

Our results suggest that PACs are not spherical in shape. Evaluation of PAC treatment response based on RECIST guidelines may not be accurate.

Comparison of two-dimensional and three-dimensional iterative watershed segmentation methods in hepatic tumor volumetrics

In this work the authors compare the accuracy of two-dimensional (2D) and three-dimensional (3D) implementations of a computer-aided image segmentation method to that of physician observers (using manual outlining) for volume measurements of liver tumors visualized with diagnostic contrast-enhanced and PET/CT-based non-contrast-enhanced (PET-CT) CT scans. The method assessed is a hybridization of the watershed method using observer-set markers with a gradient vector flow approach. This method is known as the iterative watershed segmentation (IWS) method. Initial assessments are performed using software phantoms that model a range of tumor shapes, noise levels, and noise qualities. IWS is then applied to CT image sets of patients with identified hepatic tumors and compared to the physicians' manual outlines on the same tumors. The repeatability of the physicians' measurements is also assessed. IWS utilizes multiple levels of segmentation performed with the use of "fuzzy regions" that could be considered part of a selected tumor. In phantom studies, the outermost volume outline for level 1 (called level 1_1 consisting of inner region plus fuzzy region) was generally the most accurate. For in vivo studies, the level 1_1 and the second outermost outline for level 2 (called level 2_2 consisting of inner region plus two fuzzy regions) typically had the smallest percent error values when compared to physician observer volume estimates. Our data indicate that allowing the operator to choose the "best result" level iteration outline from all generated outlines would likely give the more accurate volume for a given tumor rather than automatically choosing a particular level iteration outline. The preliminary in vivo results indicate that 2D-IWS is likely to be more accurate than 3D-IWS in relation to the observer volume estimates.

Missed lesions at abdominal oncologic CT: lessons learned from quality assurance

The evaluation of oncology patients represents a substantial volume of the workload in many radiology departments. Interpreting the results of oncologic examinations is often challenging and time-consuming because many abnormalities are identified in the same examination and must be compared with the findings in previous studies. However, errors in the interpretation of oncologic computed tomographic (CT) scans can have significant effects on patient care. These effects may range from withdrawal from a clinical trial or cessation of therapy to repeat CT examination because of a technically inadequate study, CT-guided biopsy of newly identified lesions, or initiation of therapy for previously unrecognized lesions. A root cause analysis of reported errors in the interpretation of abdominal and pelvic CT scans led to the identification of potential pitfalls that may be encountered when interpreting oncologic CT scans and factors that contribute to these errors. Awareness of the spectrum of factors that contribute to misinterpretation of CT scans in oncology patients may improve the performance of the individual radiologist and ultimately translate into improved patient care.

Imaging of the airways with multidetector row computed tomography

The wide availability of multidetector row computed tomography (MDCT) continues to change the way we manage patients. Once the domain of the specialist paediatric centre, imaging of the paediatric thorax now routinely occurs in many general hospitals. The paediatric respiratory and radiology teams should therefore be familiar with this technique. This review examines the indications for MDCT, the different types of scan, the use of low-dose protocols for paediatric imaging and appropriate reconstruction techniques. Patient preparation, with particular respect to sedation and optimal contrast bolus delivery, is also addressed.

[Comparison of unidimensional and bidimensional measurement to assess therapeutic response in the treatment of solid tumors]

PURPOSE

In this prospective study we applied both the bidimensional WHO method and the unidimensional RECIST method in treatment follow-up of solid tumors.

MATERIAL AND METHODS

Computed tomography was performed in 80 patients before and after one chemotherapy cycle: 20 patients each with lung cancer, lymphoma, and metastases of the lung and the liver. In 207 tumor lesions unidimensional and bidimensional measurements were performed: 36 lesions of lung cancer, 51 lesions of lymphoma, and 60 lesions of metastases of the lung and the liver, respectively. We assigned the results to the corresponding response categories.

RESULTS

For tumor assessment, the kappa statistic produced a high agreement of 0.94 between the two methods for assessment of therapeutic response.

CONCLUSION

The unidimensional RECIST measurement is easier to perform in order to assess tumor size during treatment follow-up in oncologic radiology.

18F-fluorodeoxyglucose positron emission tomography in uterine carcinosarcoma

PURPOSE

Uterine carcinosarcomas clinically confined to the uterus usually harbor occult metastases. We conducted a pilot study to evaluate the value of (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in uterine carcinosarcoma.

METHODS

Patients with histologically confirmed uterine carcinosarcoma were enrolled. Abdominal and pelvic magnetic resonance imaging (MRI)/whole-body computed tomography (CT) scan, and whole-body (18)F-FDG PET or PET/CT were undertaken for primary staging, evaluating response, and restaging/post-therapy surveillance. The clinical impact of (18)F-FDG PET was determined on a scan basis.

RESULTS

A total of 19 patients were recruited and 31 (18)F-FDG PET scans (including 8 scans performed on a PET/CT scanner) were performed. Positive impacts of scans were found in 36.8% (7/19) for primary staging, 66.7% (2/3) for monitoring response, and 11.1% (1/9) for restaging/post-therapy surveillance. PET excluded falsely inoperable disease defined by MRI in two patients. Aggressive treatment applying to three patients with PET-defined resectable stage IVB disease seemed futile. Two patients died of disease shortly after salvage therapy restaged by PET. With PET monitoring, one stage IVB patient treated by targeted therapy only was alive with good performance. Using PET did not lead to improvement of overall survival of this series compared with the historical control (n = 35) (P = 0.779).

CONCLUSIONS

The preliminary results suggest that (18)F-FDG PET is beneficial in excluding falsely inoperable disease for curative therapy and in making a decision on palliation for better quality of life instead of aggressive treatment under the guidance of PET. PET seems to have limited value in post-therapy surveillance or restaging after failure.

Nasopharyngeal Cancers: Which Method Should be Used to Measure these Irregularly Shaped Tumors on Cross-Sectional Imaging?

PURPOSE

To determine whether the standard techniques of measuring tumor size and change in size after treatment could be applied to the measurement of nasopharyngeal cancers, which are often irregular in shape.

METHODS AND MATERIALS

The standard measurements of bidimensional (BDM) (World Health Organization criteria) and unidimensional (UDM) (Response Evaluation Criteria in Solid Tumors [RECIST] criteria), together with the maximum depth of the tumor perpendicular to the pharyngeal wall (DM), were acquired from axial magnetic resonance images of primary nasopharyngeal carcinoma in 44 patients at diagnosis and in 29 of these patients after treatment. Tumor volume measurements (VM), acquired from the summation of areas from the axial magnetic resonance images, were used as the reference standard.

RESULTS

There was a significant association between VM and BDM with respect to tumor size at diagnosis (p = 0.002), absolute change in tumor size after treatment (p < 0.001), and percentage change in tumor size after treatment (p = 0.044), but not between VM and UDM. There was also a significant association between VM and DM with respect to percentage change in tumor size after treatment (p = <0.0001) but not absolute change (p = 0.222).

CONCLUSION

When using simple measurements to assess irregularly shaped nasopharyngeal cancers, the BDM should be used to measure size at diagnosis and the BDM and percentage change in size with treatment. Unidimensional measurement does not reflect size or change in size, and therefore the RECIST criteria may not be applicable to all tumor shapes. The use of DM requires further evaluation.

FDG-PET/CT in restaging of patients with recurrent breast cancer: possible impact on staging and therapy

We aimed to compare the value of combined positron emission tomography (PET)/CT, PET+CT (viewed side by side), CT alone and PET alone concerning the rTNM stage and influence on therapy in patients with recurrent breast cancer. 44 patients with suspicion of recurrent breast cancer underwent whole-body [18F]-2-fluoro-2-deoxy-d-glucose (FDG)-PET/CT. Images of combined PET/CT, PET+CT, PET alone and CT alone were evaluated by four blinded reader teams. Diagnostic accuracies and influence on therapy were compared. Histology and a mean clinical follow up of 456 days served as the standard of reference. Differences between the staging procedures were tested for statistical significance by McNemar's test. Overall TNM tumour stage was correctly determined in 40/44 patients with PET/CT, in 38/44 with PET+CT, in 36/44 with PET alone and in 36/44 patients with CT alone. No statistically significant difference was detected between all tested imaging modalities. PET/CT changed the therapy in two patients compared with PET+CT, in four patients compared with PET alone and in five patients compared with CT alone. Combined PET/CT appeared to be more accurate in assessing the rTNM and showed a moderate impact on therapy over PET and CT. Minor improvements were noted when compared with PET+CT. Experienced readers might therefore be able to provide accurate staging results for further therapy from separately acquired studies.

Clinical impact of integrated PET/CT on the management of suspected cervical cancer recurrence

OBJECTIVES

To assess the value and clinical impact of integrated PET/CT using (18)F-FDG in the diagnosis and management of women with suspected cervical cancer recurrence.

METHODS

Fifty-two patients with cervical cancer with suspected recurrence because of clinical, cytological, biochemical and radiological findings were retrospectively evaluated. A final diagnosis of recurrence was confirmed by histologic tissue biopsy or by further clinical or radiological evidence. The clinical impact of information provided by PET/CT on patient management was assessed on the basis of clinical follow-up data concerning further diagnostic or therapeutic approach.

RESULTS

Twenty-eight of 32 positive PET/CT scans (87.5%) were proven to have recurrent disease. Seventeen of 20 negative PET/CT scans (85.0%) had no evidence of disease. The sensitivity, specificity, and accuracy of PET/CT for detecting recurrence were 90.3%, 81.0%, and 86.5% respectively. PET/CT changed the management of 12 patients (23.1%) by changing treatment plan (5 patients), by initiating unplanned treatment strategy (4 patients), or by obviating the need for planned diagnostic procedures (3 patients). Median duration after performing PET/CT and last follow-up was 12 (range: 6-27) months, and the 2-year disease-free survival rate of patients with negative PET/CT scan for recurrence was significantly better than that of patients with positive PET/CT (85.0% vs. 10.9%, P=0002).

CONCLUSIONS

In patients with a suspected recurrence of cervical cancer, integrated PET/CT using (18)F-FDG provides good anatomic and functional localization of suspicious lesions, and the better diagnostic interpretation has an impact not only on clinical management and treatment planning of patients, but also on disease-free survival.

Tomografía por emisión de positrones/tomografía computarizada: artefactos y pitfalls en pacientes con cáncer

Diagnostic accuracy and correct initial staging (or restaging) are fundamental in the management of oncological patients and can directly influence therapeutic decisions. The combination of positron-emission tomography (PET) and computed tomography (CT) in a single scanner (PET/TC) represents an important achievement in the fields of oncology, nuclear medicine, and radiology. These scanners allow morphologic images (obtained by CT) to be fused and correlated with metabolic images (obtained by PET) to a high degree of accuracy. In addition to an understanding of the physiopathology of cancer and the behavior of the different types of neoplasms, the correct interpretation of PET/CT images requires in-depth knowledge of the physiological distribution of the F-18 fluorodeoxyglucose molecule (FDG, currently the most widely used marker in oncology), of the frequent physiological variations in its distribution, and of the possible causes of non-malignant pathological FDG uptake. Furthermore, the use of CT data to correct attenuation and reconstruct PET images in PET/CT scanners can generate some characteristic artifacts specific to this new diagnostic tool, and these can lead to misinterpretation with potential therapeutic implications. This article reviews and illustrates some of the most common artifacts and pitfalls that can appear in PET/CT studies. The detection and correct interpretation of these findings are essential for the appropriate management of oncologic patients.

Whole-body PET/CT: spectrum of physiological variants, artifacts and interpretative pitfalls in cancer patients

Accurate diagnosis and staging in oncology is essential in the evaluation of cancer for optimal patient outcome. Conventional imaging techniques, such as computed tomography (CT), rely basically on morphological changes for tumour detection. Clinical experience, however, shows that morphological criteria may be misleading and may not always allow differentiation between benign and malignant lesions. Positron emission tomography (PET) with [F]fluorodeoxyglucose (FDG) is rapidly gaining a critical role in the clinical evaluation of patients with cancer. However, PET lacks anatomical landmarks for topographic orientation, and identification of abnormal glucose metabolic activity in regions close to organs with variable physiological FDG uptake can be difficult. To overcome these difficulties, a combined PET/CT scanner that acquires both functional (PET) and CT images has been recently developed. Proper interpretation of PET (and PET/CT) images requires a thorough understanding of the normal physiological distribution of FDG in the body, along with a knowledge of frequently encountered physiological variations in FDG distribution, and recognition of non-malignant causes of FDG uptake that can be confused with a malignant neoplasm. In addition, because of the utilization of the CT transmission information for the correction of the attenuation of the PET emission data (and for the reconstruction of the PET images), some artifacts may be generated. As a consequence, CT based attenuation correction of PET images may result in erroneous PET/CT interpretations. The aim of this extensively illustrated paper is to demonstrate several potential pitfalls encountered during the interpretation of PET/CT images so that radiologists can avoid false positive diagnoses and recognize inherently non-specific findings on PET/CT images obtained for oncological diagnosis.

Liver and Spleen Volumetry with Quantitative MR Imaging and Dual-Space Clustering Segmentation

The purpose of this HIPAA-compliant, institutional review board-approved study was to assess the liver and spleen volumes calculated by using a semiautomated dual-space clustering segmentation technique, as compared with the volumes calculated by using the manual contour-tracing method. The quantitative magnetic resonance (MR) imaging data used as input were computed from images acquired by using a mixed fast spin-echo pulse sequence that was implemented with respiratory triggering. Linear regression analysis was used to assess agreement regarding the volumes calculated by using both segmentation techniques. There was strong agreement regarding the regression parameters for the liver (r = 0.98, P < .001) and the spleen (r = 0.99, P < .001) and the mean percentage volume differences for the liver (1.2%) and the spleen (0.9%). The mean segmentation time per patient was significantly shorter with use of the dual-space clustering method (P < .001).

New Agents in the Management of Advanced Mesothelioma

Malignant pleural mesothelioma (MPM) is a seemingly uncommon tumor whose incidence has in fact increased steadily and progressively over the last 30 years. Indeed, an actual "epidemic" is expected in Europe over the next 20 years. Despite unquestionable improvement in the diagnostic methods at our disposal and the availability of new treatment strategies, the prognosis of MPM patients remains dramatically poor (12 to 18 months' median survival from diagnosis), although exceptional cases of long-survivors are reported in all literature series. The current review will cover the dramatic improvements in the treatment of this rare disease that have been recently achieved, as well as the promise that new, molecular-targeted therapies, such as bortezomid, mTOR ( m ammalian t arget o f r apamycin) inhibitors, and Met inhibitors, seem to offer for the next few years. With pemetrexed we now have a drug that is able to impact patient survival. Together with the newer drugs, rapidly emerging from the laboratory to be applied in the clinic, we have the hope of making further advances in the struggle against this disease.

Tumor response assessment is more robust with sequential CT scanning than external caliper measurements

RATIONALE AND OBJECTIVES

Measurements of tumor size are important in assessing response to cancer therapies. To date, preclinical studies of drug development have relied on direct caliper-based measurements of tumor size. We investigated the feasibility of using a human positron emission tomographic (PET)/computed tomographic (CT) scanner to assess tumor size before and after chemotherapy and compared this approach with caliper measurements.

MATERIALS AND METHODS

Fourteen rats with rat mammary tumor underwent high-resolution CT using a PET/CT scanner before and after chemotherapy, and tumor volumes were measured independently by two observers using calipers and CT images.

RESULTS

Tumor response could be detected after 1 day of treatment by means of CT imaging, but was not significant until 2 days or later by means of caliper measures because of their greater variability. Independent measurements of tumor size correlated well with one another by means of CT, but correlated less by means of calipers.

CONCLUSION

Tumor size measurements by means of CT from PET/CT were more reliable than caliper measurements because of their smaller variance, allowing earlier assessment of response. It is suggested that CT imaging-based methods of assessing tumor response replace traditional caliper-based measurements, much as CT has become a standard for assessing tumor response in humans.

Gastrointestinal stromal tumor: new nodule-within-a-mass pattern of recurrence after partial response to imatinib mesylate

PURPOSE

To investigate a new pattern of tumor recurrence observed at imaging in patients with metastatic gastrointestinal stromal tumor (GIST) after initial partial response to imatinib mesylate.

MATERIALS AND METHODS

Ninety-two patients with metastatic GIST who underwent treatment in a clinical trial with oral imatinib mesylate were followed up for 29 months. An institutional review board-approved protocol was used. The study complied with the Health Insurance Portability and Accountability Act, and written informed consent was obtained from all patients. Images of the chest, abdomen, and pelvis, acquired with computed tomography (CT), positron emission tomography (PET), and, in some cases, magnetic resonance imaging, were evaluated for treatment response and disease recurrence. Thirty-nine patients (29 men, 10 women; age range, 18-84 years; mean, 49.2 years) had recurrent disease after an initial variable period of response (range, 2-24 months; median, 14.4 months). Initial response was determined with findings of decreased uptake of fluorine 18 fluorodeoxyglucose at PET, shrinkage of tumor, and decreased attenuation at CT. Images were evaluated for disease recurrence by two experienced radiologists who were blinded to each other's interpretation but not to clinical details. Final reading was performed by consensus.

RESULTS

A nodule within a mass was seen in 21 of 39 patients (in intrahepatic tumor [n = 8], extrahepatic tumor [n = 10], or both intra- and extrahepatic tumors [n = 3]) and was the first sign of disease progression in 17 of 21 patients. Other patterns of recurrence included new site of disease (n = 7), regrowth of preexistent lesion (n = 20), and mixed (more than one) pattern (n = 9). Disease progression was verified at needle biopsy (n = 16), follow-up imaging (n = 14), and/or surgical resection (n = 9).

CONCLUSION

A nodule within a mass is an important sign of recurrent GIST, but measurements of overall tumor size may not enable detection of such nodules.

Quantitative assessment of tumor vasculature and response to therapy in kaposi's sarcoma using functional noninvasive imaging

Two noninvasive methods, thermography and laser Doppler imaging (LDI), were assessed for their ability to quantitatively assess parameters of vascularity in lesions of HIV-associated Kaposi's sarcoma (KS). Thermography and LDI images of a representative KS lesion were recorded in 16 patients and compared to normal skin either adjacent to the lesion or on the contralateral side. Eleven of the 16 patients had greater than 0.5 degrees C increased temperature and 12 of the 16 patients had increased flux (measured by LDI) as compared to normal skin. There was a strong correlation between these two parameters (R = 0.81, p < 0.001). In ten patients, measurements were obtained prior to therapy and after receiving a regimen of liposomal doxorubicin and interleukin-12. After 18 weeks of therapy, temperature and blood flow of the lesions were significantly reduced from the baseline (p = 0.004 and 0.002 respectively). These techniques hold promise to assess physiologic parameters in KS lesions and their changes with therapy.

The diagnostic accuracy of 18F-Fluorodeoxyglucose PET/CT in patients with gynecological malignancies

OBJECTIVE

To evaluate the diagnostic accuracy of integrated positron emission tomography/computerized tomography (PET/CT) in patients with gynecological cancer.

METHODS

Fifty-three consecutive patients with gynecologic malignancies were included. The patients were referred to our tertiary center to undergo a PET/CT scan. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of PET/CT were compared with the conventional imaging assessments [CT, magnetic resonance imaging (MRI) and ultrasonography (US)].

RESULTS

All tested values were higher for PET/CT than those for the conventional modalities: sensitivity 0.97 vs. 0.40, specificity 0.94 vs. 0.65, PPV 0.97 vs. 0.70, and NPV 0.94 vs. 0.34, respectively.

CONCLUSION

PET/CT is a reliable modality for assessing the extent of disease in patients with gynecologic malignancy.

Estimation of the tissue composition of the tumour mass in neuroblastoma using segmented CT images

Neuroblastoma is the most common extra-cranial, solid, malignant tumour in children. Advances in radiology have made possible the detection and staging of the disease. Nevertheless, there is no method available at present that can go beyond detection and qualitative analysis, towards quantitative assessment of the tissue composition of the primary tumour mass in neuroblastoma. Such quantitative analysis could provide important information and serve as a decision-support tool to the radiologist and the oncologist, result in better treatment and follow-up and even lead to the avoidance of delayed surgery. The problem investigated was the improvement of the analysis of the primary tumour mass, in patients with neuroblastoma, using X-ray computed tomography (CT) images. A methodology was proposed for the estimation of the tissue content of the mass: it comprised a Gaussian mixture model for estimation, from segmented CT images, of the tissue composition of the primary tumour. To demonstrate the potential of the method, the results are presented of its application to ten CT examinations of four patients. The method provides quantitative information, and it was observed that the tumour in one of the patients reduced from 523 cm3 to 81 cm3 in volume, with an increase in calcification from about 20% to about 88% of the tumour volume, in response to chemotherapy over a period of five months. Results indicate that the proposed technique may be of considerable value in assessing the response to therapy of patients with neuroblastoma.

Imaging of neuroendocrine tumors: accuracy of helical CT versus SRS

BACKGROUND

We retrospectively compared the accuracy of somatostatin receptor scintigraphy (SRS) with that of helical computed tomography (CT) in the detection and localization of primary and metastatic neuroendocrine tumors.

METHODS

A medical record search identified 27 patients with known or clinically suspected neuroendocrine tumors who underwent helical CT and SRS within 3 months of one another at our institution. CT images were evaluated retrospectively by two blinded radiologists who used consensus reading. Images were evaluated for the presence or absence of primary tumor and hepatic and extrahepatic metastases. CT results were compared with the SRS report as interpreted by the nuclear medicine physicians. The results of the surgical, clinical follow-up, and pathologic findings were considered as the gold standard. Sensitivity, specificity, and accuracy were calculated for both imaging techniques. In addition, McNemar analysis was performed to determine statistically significant differences between CT and SRS.

RESULTS

Helical CT was more sensitive than SRS in the detection of extrahepatic metastases, and the difference between the two imaging modalities was statistically significant (p = 0.0312) as determined by the McNemar chi-square test. However, the difference between CT and SRS in detecting primary neuroendocrine tumors, hepatic metastasis, and combined hepatic and extrahepatic metastasis was not statistically significant (p = 0.625, 1.000, and 1.000, respectively).

CONCLUSION

Helical CT and SRS have similar sensitivity, specificity, and accuracy in detecting primary neuroendocrine tumor and hepatic metastasis. However, helical CT appears to be more sensitive in detecting extrahepatic metastasis from primary neuroendocrine tumors.

Liver cancer imaging: role of CT, MRI, US and PET

Liver imaging in patients with a history of known or suspected malignancy is important because the liver is a common site of metastatic spread, especially tumours from the colon, lung, pancreas and stomach, and in patients with chronic liver disease who are at risk for developing hepatocellular carcinoma. Since benign liver lesions are common, liver-imaging strategies should incorporate liver lesion detection and characterisation. Survey examination in patients with a known extra-hepatic malignancy to exclude the presence of hepatic and extra-hepatic involvement is normally undertaken with a contrast-enhanced computed tomography examination. When patients with hepatic metastases are being considered for metastasesectomy, they undergo a staging examination with contrast-enhanced magnetic resonance imaging (MRI) using tissue-specific contrast agents. Patients with chronic liver disease who are at risk for hepatocellular carcinoma undergo periodic liver screening for focal liver detection, usually with ultrasonography (US) with MRI being used when US is equivocal. Finally, contrast-enhanced MRI with extra-cellular gadolinium chelates is preferred for characterisation of indeterminate hepatic masses with liver biopsy used when tissue diagnosis is needed.

Intraoperative Radiation Therapy in Liver Tissue in a Pig Model: Monitoring with Dual-Modality PET/CT

PURPOSE

To assess, in a pig model, the value of dual-modality positron emission tomography (PET)/computed tomography (CT) for monitoring radiation therapy.

MATERIALS AND METHODS

Central bile duct resection followed by creation of a biliodigestive anastomosis was performed in nine pigs. Six of these pigs were also treated with intraoperative radiation therapy (IORT) (20 Gy) in the area of the anastomosis. Two, 4, and 8 weeks postoperatively, contrast material-enhanced fluorine 18 fluorodeoxyglucose (FDG) PET/CT of the liver was performed in all of the animals. The radioactive tracer concentration in the region of the anastomosis was quantified, and the values were compared intraindividually with the values at the liver periphery. Histologic evaluation of the liver was performed 8 weeks postoperatively. The PET/CT images were assessed for changes in liver volume and bile duct diameter over time.

RESULTS

In all nine pigs, the region of the anastomosis could be clearly defined on the fused PET/CT images. PET/CT revealed a decreased concentration of FDG in the irradiated field 2 and 4 weeks after IORT. At 8 weeks, however, the distribution of the tracer in the irradiated pigs did not differ from that in the nonirradiated pigs. Homogeneous tracer uptake in all liver regions was observed in the nonirradiated animals. The CT images showed an increase in liver volume in all pigs and bile duct dilatation that increased over time in the irradiated pigs.

CONCLUSION

The morphologic and functional changes due to IORT in liver tissue can be accurately monitored with dual-modality PET/CT. By enabling the integration of functional and morphologic data, PET/CT may have an important role in monitoring radiation treatment.

Future generation CT imaging

X-ray CT technology has been available for more than 30 years, yet continued technological advances have kept CT imaging at the forefront of medical imaging innovation. Consequently, the number of clinical CT applications has increased steadily. Other imaging modalities might be superior to CT imaging for some specific applications, but no other single modality is more often used in chest imaging today. Future technological developments in the area of high-resolution detectors, high-capacity x-ray tubes, advanced reconstruction algorithms, and improved visualization techniques will continue to expand the imaging capability. Future CT imaging technology will combine improved imaging capability with advanced and specific computer-assisted tools, which will expand the usefulness of CT imaging in many areas.

Volumetric tumor measurement using three-dimensional ultrasound: in vitro phantom study on measurement accuracy under various scanning conditions

Factors influencing volumetric tumor measurement using 3-D ultrasound (US) were investigated. A 3-D US unit equipped with 4- to 8-MHz curved-array and 5- to 10-MHz linear-array mechanical volume transducers, and a US phantom made of 20 ham pieces (8.6 approximately 10.5 mL) embedded in agar gel that simulated hyperechoic tumors, were used. Volumetric tumor measurement was significantly affected by the position of US focus and tumor depth. When focus was at 2 cm and 8 cm below the transducer, 5-cm-deep tumors were measured 5.6% +/- 2.8% (mean +/- SD) and 8.3% +/- 2.2% bigger, respectively, than when focus was at 5 cm below the transducer, the same position as tumors (p < 0.01). Tumors were measured 11.8% +/- 2.9% bigger when they were 8-cm deep below the transducer than when they were 5-cm deep below the transducer (p < 0.001). Setting focus at the same position as tumors and keeping tumor depth consistent during serial 3-D US examinations may be necessary for reliable volumetric assessment of tumors.

Clinical biomarkers in drug discovery and development

Biomarkers enable the characterization of patient populations and quantitation of the extent to which new drugs reach intended targets, alter proposed pathophysiological mechanisms and achieve clinical outcomes. In genomics, the biomarker challenge is to identify unique molecular signatures in complex biological mixtures that can be unambiguously correlated to biological events in order to validate novel drug targets and predict drug response. Biomarkers can stratify patient populations or quantify drug benefit in primary prevention or disease-modification studies in poorly served areas such as neurodegeneration and cancer. Clinically useful biomarkers are required to inform regulatory and therapeutic decision making regarding candidate drugs and their indications in order to help bring new medicines to the right patients faster than they are today.