Follow-up of women with breast cancer: comparison between MRI and FDG PET

Diagnostic Performance of PET/MRI in Breast Cancer: A Systematic Review and Bayesian Bivariate Meta-analysis

INTRODUCTION

By performing a systematic review and meta-analysis, the diagnostic value of ¹⁸F-FDG PET/MRI in breast lesions, lymph nodes, and distant metastases was assessed, and the merits and demerits of PET/MRI in the application of breast cancer were comprehensively reviewed.

METHODS

Breast cancer-related studies using ¹⁸F-FDG PET/MRI as a diagnostic tool published before September 12, 2022 were included. The pooled sensitivity, specificity, log diagnostic odds ratio (LDOR), and area under the curve (AUC) were calculated using Bayesian bivariate meta-analysis in a lesion-based and patient-based manner.

RESULTS

We ultimately included 24 studies (including 1723 patients). Whether on a lesion-based or patient-based analysis, PET/MRI showed superior overall pooled sensitivity (0.95 [95% CI: 0.92-0.98] & 0.93 [95% CI: 0.88-0.98]), specificity (0.94 [95% CI: 0.90-0.97] & 0.94 [95% CI: 0.92-0.97]), LDOR (5.79 [95% CI: 4.95-6.86] & 5.64 [95% CI: 4.58-7.03]) and AUC (0.98 [95% CI: 0.94-0.99] & 0.98[95% CI: 0.92-0.99]) for diagnostic applications in breast cancer. In the specific subgroup analysis, PET/MRI had high pooled sensitivity and specificity for the diagnosis of breast lesions and distant metastatic lesions and was especially excellent for bone lesions. PET/MRI performed poorly for diagnosing axillary lymph nodes but was better than for lymph nodes at other sites (pooled sensitivity, specificity, LDOR, AUC: 0.86 vs. 0.58, 0.90 vs. 0.82, 4.09 vs. 1.98, 0.89 vs. 0.84).

CONCLUSION

¹⁸F-FDG PET/MRI performed excellently in diagnosing breast lesions and distant metastases. It can be applied to the initial diagnosis of suspicious breast lesions, accurate staging of breast cancer patients, and accurate restaging of patients with suspected recurrence.

Internal mammary lymph node siliconoma in absence of prosthesis rupture: a case series that raises concern for potential risk of overdiagnosis

Background

Silicon migration after rupture is an adverse event of breast implant, whose risk increases with the aging of prosthesis. The exact prevalence of this complication remains unclear and reported data are inconsistent. In addition, microscopic diffusion of silicone gel through intact implant, known as gel bleeding, might verify thus complicating diagnosis. Although high cohesive gel has reduced the occurrence of gel bleeding, this phenomenon is still possible and its occurrence rate remains underestimated. If silicon droplets migrate in locoregional lymph node, a swelling that mimics recurrence can arise. Therefore, a risk of overdiagnosis is possible when clinicians rely only on imaging techniques. The aim of this study is to evaluate the actual prevalence of metastasis in internal mammary lymph node (IMLN) in presence of PET positive uptake and no prosthesis rupture.

Methods

We retrospectively evaluated our patient's records and selected those with intact breast implants and suspected relapse in IMLN that underwent biopsy, either surgical or imaging guided. All patients performed PET/CT scan showing pathological uptake in IMLNs. A breast magnetic resonance (MRI) or ultrasound (US) imaging confirmed a suspicious adenopathy and excluded prosthesis rupture. From 2015 to 2019 a total of nine patients underwent biopsy of the IMLN and only six of them met inclusion criteria.

Results

Four biopsies were CT-guided, two were surgical. Three patients (50%) were diagnosed with breast cancer relapse while two (33.3%) were found with siliconoma and one (16.7%) was inflammatory.

Conclusions

Siliconoma can occur even without evidence of capsule rupture, challenging the clinicians and leading to a risk of relapse over diagnosis. Echographic, MRI and nuclear medicine imaging criteria may be not sufficient in differential diagnosis. To overcome the issue, we suggest introducing into the clinical practice the biopsy of suspicious enlarged IMLN with minimally invasive technique.

Anatomical accuracy of abdominal lesion localization

Software-based image registration can improve the diagnostic value of imaging procedures and is an alternative to hybrid scanners. The aim of this study was to evaluate the anatomical accuracy of automatic rigid image registration of independently acquired datasets of positron emission tomography with 18F-deoxyglucose and abdominal magnetic resonance imaging. Patients, methods: Analyses were performed on 28 abdominal lesions from 20 patients. The PET data were obtained using a stand-alone PET camera in 14 cases and a hybrid PET/CT scanner in 9 cases. The abdominal T1- and T2-weighted MRI scans were acquired on 1.5 T MRI scanners. The mean time interval between MRI and PET was 7.3 days (0–28 days). Automatic rigid registration was carried out using a self-developed registration tool integrated into commercial available software (InSpace for Siemens Syngo). Distances between the centres of gravity of 28 manually delineated neoplastic lesions represented in PET and MRI were measured in X-, Y-, and Z-direction. The intra- (intraclass correlation 0.94) and inter- (intraclass correlation 0.86) observer repeatability were high. Results: The average distance in all MRI sequences was 5.2 ± 7.6 mm in X-direction, 4.0 ± 3.7 mm in Y-direction and 6.1 ± 5.1 mm in Z-direction. There was a significantly higher misalignment in Z-direction (p < 0.05). The misalignment was not significantly different for the registration of T1- and T2- weighted sequences (p = 0.7). Conclusion: The misalignment between FDG-PET and abdominal MRI registered using an automated rigid registration tool was comparable to data reported for software-based fusion between PET and CT. Although this imprecision may not affect diagnostic accuracy, it is not sufficient to allow for pixel-wise integration of MRI and PET information.

Incremental Value of Cocktail 18F-FDG and 18F-NaF PET/CT Over 18F-FDG PET/CT Alone for Characterization of Skeletal Metastases in Breast Cancer

PURPOSE

The aim of this study was to evaluate the incremental value of cocktail F-FDG/F-NaF PET/CT over F-FDG PET/CT alone for detection of skeletal metastases in breast cancer patients.

METHODS

Seventy patients with locally advanced/recurrent breast cancer were prospectively included. All patients underwent whole-body F-FDG PET/CT and cocktail F-FDG/F-NaF PET/CT within a span of 1 week. Both studies were evaluated to detect presence of skeletal/marrow metastases on PET/CT images by 2 nuclear medicine physicians. Clinical and radiological correlation/follow-up was used as criterion standard.

RESULTS

Of 70 patients, 50 (71.0%) had locally advanced breast cancer, and 20 had recurrent breast cancer. On patient-wise analysis, both cocktail PET/CT and F-FDG PET/CT identified skeletal/marrow lesions in 23 (32.8%) of 70 patients. In 8 patients (11.4%), only cocktail PET/CT identified skeletal/marrow lesions, whereas F-FDG PET/CT was negative. In the rest of the 39 patients (55.8%), no skeletal/marrow lesion was identified on both scans. Good correlation was noted between cocktail PET/CT and F-FDG PET/CT results (r = 0.785, P < 0.0001). Cocktail PET/CT detected lesions in significantly more number of patients than F-FDG PET/CT alone (P = 0.007). On lesion-wise analysis, cocktail PET/CT detected more number of lesions in 20 patients as compared with F-FDG-PET/CT alone. Both scans detected same number of lesions in the rest of 11 patients with positive findings. A total of 32 additional lesions were identified on cocktail PET/CT imaging as compared with F PET/CT alone (P < 0.0001).

CONCLUSIONS

Cocktail F-FDG and F-NaF PET/CT is superior to F-FDG PET/CT alone for the detection of skeletal/marrow metastases in breast cancer. It can be a better alternative to F-FDG PET/CT alone in facilities where both tracers are available.

MRI fused with prone FDG PET/CT improves the primary tumour staging of patients with breast cancer

OBJECTIVE

Our aim was to evaluate the diagnostic accuracy of magnetic resonance imaging (MRI) fused with prone 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) in primary tumour staging of patients with breast cancer.

METHODS

This retrospective study evaluated 45 women with 49 pathologically proven breast carcinomas. MRI and prone PET-CT scans with time-of-flight and point-spread-function reconstruction were performed with the same dedicated breast coil. The studies were assessed by a radiologist and a nuclear medicine physician, and evaluation of fused images was made by consensus. The final diagnosis was based on pathology (90 lesions) or follow-up ≥ 24 months (17 lesions).

RESULTS

The study assessed 72 malignant and 35 benign lesions with a median size of 1.8 cm (range 0.3-8.4 cm): 31 focal, nine multifocal and nine multicentric cases. In lesion-by-lesion analysis, sensitivity, specificity, positive and negative predictive values were 97%, 80%, 91% and 93% for MRI, 96%, 71%, 87%, and 89% for prone PET, and 97%. 94%, 97% and 94% for MRI fused with PET. Areas under the curve (AUC) were 0.953, 0.850, and 0.983, respectively (p < 0.01).

CONCLUSIONS

MRI fused with FDG-PET is more accurate than FDG-PET in primary tumour staging of breast cancer patients and increases the specificity of MRI.

KEY POINTS

• FDG PET-CT may improve the specificity of MRI in breast cancer staging. • MRI fused with prone 2-[fluorine-18]-fluoro-2-deoxy-D-glucose PET-CT has better overall diagnostic performance than MRI. • The clinical role of fused PET-MRI has not yet been established.

Respiratory motion correction in 4D-PET by simultaneous motion estimation and image reconstruction (SMEIR)

In conventional 4D positron emission tomography (4D-PET), images from different frames are reconstructed individually and aligned by registration methods. Two issues that arise with this approach are as follows: (1) the reconstruction algorithms do not make full use of projection statistics; and (2) the registration between noisy images can result in poor alignment. In this study, we investigated the use of simultaneous motion estimation and image reconstruction (SMEIR) methods for motion estimation/correction in 4D-PET. A modified ordered-subset expectation maximization algorithm coupled with total variation minimization (OSEM-TV) was used to obtain a primary motion-compensated PET (pmc-PET) from all projection data, using Demons derived deformation vector fields (DVFs) as initial motion vectors. A motion model update was performed to obtain an optimal set of DVFs in the pmc-PET and other phases, by matching the forward projection of the deformed pmc-PET with measured projections from other phases. The OSEM-TV image reconstruction was repeated using updated DVFs, and new DVFs were estimated based on updated images. A 4D-XCAT phantom with typical FDG biodistribution was generated to evaluate the performance of the SMEIR algorithm in lung and liver tumors with different contrasts and different diameters (10-40 mm). The image quality of the 4D-PET was greatly improved by the SMEIR algorithm. When all projections were used to reconstruct 3D-PET without motion compensation, motion blurring artifacts were present, leading up to 150% tumor size overestimation and significant quantitative errors, including 50% underestimation of tumor contrast and 59% underestimation of tumor uptake. Errors were reduced to less than 10% in most images by using the SMEIR algorithm, showing its potential in motion estimation/correction in 4D-PET.

Diagnostic accuracy of (18)F-FDG PET/CT compared with that of contrast-enhanced MRI of the breast at 3 T

PURPOSE

To compare the diagnostic accuracy of prone (18)F-FDG PET/CT with that of contrast-enhanced MRI (CE-MRI) at 3 T in suspicious breast lesions. To evaluate the influence of tumour size on diagnostic accuracy and the use of maximum standardized uptake value (SUVMAX) thresholds to differentiate malignant from benign breast lesions.

METHODS

A total of 172 consecutive patients with an imaging abnormality were included in this IRB-approved prospective study. All patients underwent (18)F-FDG PET/CT and CE-MRI of the breast at 3 T in the prone position. Two reader teams independently evaluated the likelihood of malignancy as determined by (18)F-FDG PET/CT and CE-MRI independently. (18)F-FDG PET/CT data were qualitatively evaluated by visual interpretation. Quantitative assessment was performed by calculation of SUVMAX. Sensitivity, specificity, diagnostic accuracy, area under the curve and interreader agreement were calculated for all lesions and for lesions <10 mm. Histopathology was used as the standard of reference.

RESULTS

There were 132 malignant and 40 benign lesions; 23 lesions (13.4%) were <10 mm. Both (18)F-FDG PET/CT and CE-MRI achieved an overall diagnostic accuracy of 93%. There were no significant differences in sensitivity (p = 0.125), specificity (p = 0.344) or diagnostic accuracy (p = 1). For lesions <10 mm, diagnostic accuracy deteriorated to 91% with both (18)F-FDG PET/CT and CE-MRI. Although no significant difference was found for lesions <10 mm, CE-MRI at 3 T seemed to be more sensitive but less specific than (18)F-FDG PET/CT. Interreader agreement was excellent (κ = 0.85 and κ = 0.92). SUVMAX threshold was not helpful in differentiating benign from malignant lesions.

CONCLUSION

(18)F-FDG PET/CT and CE-MRI at 3 T showed equal diagnostic accuracies in breast cancer diagnosis. For lesions <10 mm, diagnostic accuracy deteriorated, but was equal for (18)F-FDG PET/CT and CE-MRI at 3 T. For lesions <10 mm, CE-MRI at 3 T seemed to be more sensitive but less specific than (18)F-FDG PET/CT. Quantitative assessment using an SUVMAX threshold for differentiating benign from malignant lesions was not helpful in breast cancer diagnosis.

Special Relevance of FDG-PET as an Upfront Diagnostic Modality at Initial Diagnosis and in Suspected Recurrence in Patients of Breast Carcinoma Hailing From Lower Socioeconomic Status Owing to Relative Late Presentation: A Pilot Study in a Medical College Hospital Setting in India

FDG-PET has found relatively limited use in routine management of breast carcinoma due to its limited utility in assessing the primary and axillary lymph node status. The aim of the study was to assess its role in a medical school and municipal hospital setting of Mumbai, where majority belongs to the lower socioeconomic status and presents relatively late and hence whole body FDG-PET could find important place for assessing whole body disease status that would justify being used upfront in this group of patients. Thus, the premise of this study was that FDG-PET will have special relevance in this particular setting for evaluation of patients of breast carcinoma with respect to initial staging, detection of locoregional recurrence and metastasis and assessing response to systemic treatment. A total of 52 patients proven to have breast carcinoma, who had undergone (18)F FDG-PET for disease staging at initial diagnosis and in in recurrent disease staging with a few cases as a baseline study for early treatment monitoring purposes over a study period of 3 years, were included in this analysis. 33.3 % of patients with pretreatment baseline FDG-PET were upstaged with diagnosis of additional lesions in the adrenal gland, liver, internal mammary, cervical lymph nodes and the mediastinum. On a lesion specific analysis, the percentage of increased lesion detection (including both lymph node with distant metastasis) by FDG-PET was 42.7 %. FDG-PET was found to be 100 % sensitive and specific for confirming recurrent breast cancer. Four out of 18 patients on chemotherapy underwent second FDG-PET after first cycle of chemotherapy, showed responsiveness to chemotherapy by decreased maximum standardized uptake value (SUVmax). FDG-PET showed 9 liver lesions in 6 patients, only 3 of them was reported in USG. In one patient USG abdomen was inconclusive between hemangioma and metastasis, FDG-PET ruled out liver metastasis in this patient. In the examined patient population belonging to lower socioeconomic status, where usual presentation is relatively late, upfront whole body survey with FDG-PET or PET/CT is of considerable value in view of higher probability of existence of metastatic disease, thus can be an important one-stop shop tool in assessing whole body disease status in a single examination. It also proved efficacious in diagnosing loco regional and distant recurrence, metabolic characterization of lump and early response to treatment in the examined few cases following one cycle of chemotherapy in locally advanced breast cancer.

Associations between cancer-related information seeking and receiving PET imaging for routine cancer surveillance--an analysis of longitudinal survey data

BACKGROUND

Routine cancer surveillance with positron emission tomography (PET) is not recommended for most patients who have completed curative treatment for cancer. Yet, recent trends suggest that PET is increasingly used for follow-up among patients with cancer. This study investigates whether information-seeking behaviors predicted self-reported utilization of PET for routine surveillance in patients with colorectal, breast, and prostate cancer.

METHODS

We conducted annual surveys for 3 years in a cohort of Pennsylvania cancer survivors diagnosed with colorectal, breast, or prostate cancer in 2005. The outcome was self-reported PET receipt for routine surveillance among 944 patients diagnosed with nonmetastatic disease (stages 0-III). Predictors included cancer-related information seeking from nonmedical sources and providers. Weighted multiple logistic regression analyses were performed.

RESULTS

In this population, 11% of patients reported receiving at least one PET scan for routine follow-up in a 12-month period several years after diagnosis. Seeking cancer-related information from nonmedical sources was associated with higher odds of subsequent reported PET use [OR, 3.7; 95% confidence interval (CI), 1.1-12.1; P = 0.032], after adjusting for potential confounders. Patient engagement with physicians about cancer-related information was not a significant predictor.

CONCLUSIONS

Overall reported PET utilization for routine surveillance of colorectal, breast, and prostate cancer is low. However, we found a significant association with information seeking from nonmedical sources but not from providers.

IMPACT

Exposure to cancer-related information through mass media and lay interpersonal sources may be driving inappropriate utilization of high-cost advanced imaging procedures. These findings have important implications for cancer survivors, healthcare providers, and health policy.

PET/CT in Oncology: Current Status and Perspectives

The discovery of the Warburg effect in the early twentieth century followed by the development of the fluorinated glucose analogue 18F-fluorodeoxyglucose (18F-FDG) and the invention of positron emission tomographs laid the foundation of clinical PET/CT. This review discusses the challenges and obstacles in clinical adoption of this technique. We then discuss advances in instrumentation, including the critically important introduction of PET/CT and current PET/CT protocols. Moreover, we provide evidence for the clinical utility of PET/CT for patient management and its potential impact on patient outcome, and address its cost and cost-effectiveness. Although this review largely focuses on 18F-FDG imaging, we also discuss a variety of additional molecular imaging approaches that can be used for cancer phenotyping with PET. Throughout this review we emphasize the critical contributions of CT to the strength of PET/CT.

Is a comparative clinical trial for breast cancer tumor markers to monitor disease recurrence warranted? A value of information analysis

BACKGROUND

Breast cancer tumor markers are used by some clinicians to screen for disease recurrence risk. Since there is limited evidence of benefit, additional research may be warranted.

AIM

To assess the potential value of a randomized clinical trial of breast tumor marker testing in routine follow-up of high-risk, stage II-III breast cancer survivors.

MATERIALS & METHODS

We developed a decision-analytic model of tumor marker testing plus standard surveillance every 3-6 months for 5 years. The expected value of sample information was calculated using probabilistic simulations and was a function of: the probability of selecting the optimal monitoring strategy with current versus future information; the impact of choosing the nonoptimal strategy; and the size of the population affected.

RESULTS

The value of information for a randomized clinical trial involving 9000 women was US$214 million compared with a cost of US$30-60 million to conduct such a trial. The probability of making an alternate, nonoptimal decision and choosing testing versus no testing was 32% with current versus future information from the trial. The impact of a nonoptimal decision was US$2150 and size of population impacted over 10 years was 308,000. The value of improved information on overall survival was US$105 million, quality of life US$37 million and test performance US$71 million.

CONCLUSION

Conducting a randomized clinical trial of breast cancer tumor markers appears to offer a good societal return on investment. Retrospective analyses to assess test performance and evaluation of patient quality of life using tumor markers may also offer valuable areas of research. However, alternative investments may offer even better returns in investments and, as such, the trial concept deserves further study as part of an overall research-portfolio evaluation.

Potential Clinical Applications of PET/Magnetic Resonance Imaging

Hybrid PET/magnetic resonance (MR) imaging, which combines the excellent anatomic information and functional MR imaging parameters with the metabolic and molecular information obtained with PET, may be superior to PET/computed tomography or MR imaging alone for a wide range of disease conditions. This review highlights potential clinical applications in neurologic, cardiovascular, and musculoskeletal disease conditions, with special attention to applications in oncologic imaging.

Impact of presurgical breast magnetic resonance imaging (MRI) on surgical planning - a retrospective analysis from a private radiology group

Presurgical bilateral breast MRI is being increasingly utilized in newly diagnosed breast cancer patients to identify the presence of other potentially malignant lesions and thereby guide surgical planning. The authors have performed a retrospective analysis of presurgical MRIs in 445 breast cancer patients, consecutively seen in a community practice setting, to determine what risk factors may be associated with bilateral synchronous breast cancer. Clinical, imaging, surgical, and pathological data were collected on these newly diagnosed patients, who underwent presurgical breast MRIs from November 1, 2008 through October 31, 2009. The MRIs detected 84 incremental (additional) malignancies in 66 (14.8%) patients, including 22 patients in the contralateral breast (4.9%) and 48 patients who had ipsilateral incremental malignancies (10.8%). The presurgical breast MRIs had a sensitivity of 99% and a specificity of 86%. Based on the imaging study and the subsequent biopsy(s), 105 patients (23.6%) had changes in their surgical planning. For those with incremental breast malignancies, the synchronous bilateral breast cancer patients were older (67.5 ± 13.5 years, p = 0.01). Patients with ipsilateral incremental malignancies were younger (55.6 ± 10.4 years of age, p = 0.03). A strong family history and ductal carcinoma in situ (DCIS) as the index lesion also appeared to be associated with increased bilateral malignancy detection. The authors conclude that although presurgical MRI remains controversial, our data support its role in surgical planning for newly diagnosed breast cancer patients.

The current status of positron emission mammography in breast cancer diagnosis

Mammography is currently the standard breast cancer screening procedure, even though it is constrained by low specificity in the detection of malignancy and low sensitivity in women with dense breast tissue. Modern imaging modalities, such as magnetic resonance imaging (MRI), have been developed in an effort to replace or complement mammography, because the early detection of breast cancer is critical for efficient treatment and long-term survival of patients. Nuclear medicine imaging technology has been introduced in the field of oncology with the development of positron emission tomography (PET), positron emission tomography/computed tomography (PET/CT) and, ultimately, positron emission mammography (PEM). PET offers the advantage of precise diagnosis, by measuring metabolism with the use of a radiotracer and identifying changes at the cellular level. PET/CT imaging allows for a more accurate assessment by merging the anatomic localization to the functional image. However, both techniques have not yet been established as diagnostic tools in early breast cancer detection, primarily because of low sensitivity, especially for sub-centimeter and low-grade tumors. PEM, a breast-specific device with increased spatial resolution, has been developed in order to overcome these limitations. It has demonstrated higher detectability than PET/CT and comparable or better sensitivity than MRI. The ability to target the lesions visible in PEM with PEM-guided breast biopsy systems adds to its usability in the early diagnosis of breast cancer. The results from recent studies summarized in this review indicate that PEM may prove to be a useful first-line diagnostic tool, although further evaluation and improvement are required.

Clinical utility of F-18 FDG PET/CT in recurrent breast carcinoma

PURPOSE

Although initial studies have shown the utility of fluorine-18 fluorodeoxyglucose (F-18 FDG) PET in the detection and restaging of recurrent breast carcinoma, scarce literature exists on F-18 FDG PET/computed tomography (CT). This retrospective study was carried out to evaluate the role of F-18-FDG PET/CT in recurrent breast carcinoma and its impact on management.

MATERIALS AND METHODS

Retrospective analysis of data of 111 patients who underwent F-18 FDG PET/CT and were suspected of having recurrent breast carcinoma was carried out. PET/CT imaging was carried out for distant metastases in histologically proven locoregional recurrence in 23 patients, clinically suspicious locoregional recurrence in nine patients, increasing tumour markers in two patients, suspicion of distant metastatic disease in 61 patients or as a part of surveillance in 16 patients. The final diagnosis of recurrence and stage of disease was made after histopathological analysis, correlative imaging and clinical or imaging follow-up of at least 6 months.

RESULTS

The final diagnosis of recurrent breast carcinoma was made in 76 patients and no evidence of recurrence was found in the remaining 35 patients. Locoregional disease requiring local radiotherapy or surgery was diagnosed in 14 patients and distant metastatic disease was diagnosed in 62 patients. FDG PET/CT was true positive in 75 patients, false positive in six patients, true negative in 35 patients and false negative in one patient, with a sensitivity, specificity, positive predictive value and a negative predictive value of 98.7, 85.3, 92.5 and 97.2%, respectively. FDG PET/CT also accurately restaged 22/23 patients with proven locoregional recurrence with an accuracy of 95.45%. Of 53 patients suspected of having distant metastatic disease on other imaging modalities, true distant metastatic disease was diagnosed in 36 patients and FDG PET/CT identified true metastatic disease in 35/36 patients, accurately ruling out metastases in the remaining 17 patients, and was false negative in one patient. In addition to confirming distant metastatic disease, it revealed more metastatic sites in 22 patients. Overall, F-18 FDG PET/CT had a major impact on management in 41% of the 103 patients being analysed for a major change in treatment.

CONCLUSION

F-18 FDG PET/CT is a very sensitive and specific imaging tool in detecting and restaging recurrent breast carcinoma. It can be a very useful imaging tool for restaging locoregional recurrences, and as a one-stop shop imaging technique to confirm suspicious metastatic disease on conventional imaging and to define the total burden of disease.

Evaluation of novel genetic algorithm generated schemes for positron emission tomography (PET)/magnetic resonance imaging (MRI) image fusion

The use and benefits of a multimodality approach in the context of breast cancer imaging are discussed. Fusion techniques that allow multiple images to be viewed simultaneously are discussed. Many of these fusion techniques rely on the use of color tables. A genetic algorithm that generates color tables that have desired properties such as satisfying the order principle, the rows, and columns principle, have perceivable uniformity and have maximum contrast is introduced. The generated 2D color tables can be used for displaying fused datasets. The advantage the proposed method has over other techniques is the ability to consider a much larger set of possible color tables, ensuring that the best one is found. We asked radiologists to perform a set of tasks reading fused PET/MRI breast images obtained using eight different fusion techniques. This preliminary study clearly demonstrates the need and benefit of a joint display by estimating the inaccuracies incurred when using a side-by-side display. The study suggests that the color tables generated by the genetic algorithm are good choices for fusing MR and PET images. It is interesting to note that popular techniques such as the Fire/Gray and techniques based on the HSV color space, which are prevalent in the literature and clinical practice, appear to give poorer performance.

Molecular Imaging in Breast Cancer - Potential Future Aspects

SUMMARY: Molecular imaging aims to visualize and quantify biological, physiological, and pathological processes at cellular and molecular levels. Recently, molecular imaging has been introduced into breast cancer imaging. In this review, we will present a survey of the molecular imaging techniques that are either clinically available or are being introduced into clinical imaging. We will discuss nuclear imaging and multiparametric magnetic resonance imaging as well as the combined application of molecular imaging in the assessment of breast lesions. In addition, we will briefly discuss other evolving molecular imaging techniques, such as phosphorus magnetic resonance spectroscopic imaging and sodium imaging.

Association between serial dynamic contrast-enhanced MRI and dynamic 18F-FDG PET measures in patients undergoing neoadjuvant chemotherapy for locally advanced breast cancer

PURPOSE

To investigate the relationship between changes in vascularity and metabolic activity measured by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and dynamic (18)F-FDG-positron emission tomography (PET) in breast tumors undergoing neoadjuvant chemotherapy.

MATERIALS AND METHODS

PET and MRI examinations were performed in 14 patients with locally advanced breast cancer (LABC) before and after chemotherapy. Dynamic (18)F-FDG PET measures included (18)F-FDG transport rate constant from blood to tissue (K(1)) and metabolism flux constant (Ki). DCE-MRI measures included initial peak enhancement (PE), signal enhancement ratio (SER), and tumor volume. Spearman rank-order correlations were assessed between changes in PET and MRI parameters, and measures were compared between patients with and without pathologic complete response (pCR) by Mann-Whitney U-test.

RESULTS

Changes in glucose delivery (PET K(1)) were closely correlated with changes in tumor vascularity as reflected by DCE-MRI SER (r = 0.83, P < 0.001). Metabolic changes in PET Ki showed moderate correlations with vascularity changes as reflected by SER (r = 0.71) and PE (r = 0.76), and correlated closely with MRI tumor volume (r = 0.79, P < 0.001). Decreases in K(1), Ki, SER, and PE were greater for patients with pCR compared to those with residual disease (P < 0.05).

CONCLUSION

Dynamic (18)F-FDG PET and DCE-MRI tumor measures of tumor metabolism, vascularity, and volume were well correlated for assessing LABC response to neoadjuvant chemotherapy and significantly discriminated pathologic complete responders. Further work is necessary to assess the value of combined PET and MRI for evaluating tumor pharmacodynamics in response to novel therapy.

Molecular imaging in oncology: the acceptance of PET/CT and the emergence of MR/PET imaging

In the last decade, PET-only systems have been phased out and replaced with PET-CT systems. This merger of a functional and anatomical imaging modality turned out to be extremely useful in clinical practice. Currently, PET-CT is a major diagnostic tool in oncology. At the dawn of the merger of MRI and PET, another breakthrough in clinical imaging is expected. The combination of these imaging modalities is challenging, but has particular features such as imaging biological processes at the same time in specific body locations.

Opportunities for PET to deliver clinical benefit in cancer: breast cancer as a paradigm

The glucose analogue fluorodeoxyglucose (FDG) has demonstrated enhanced uptake in the majority of tumours as a result of increased uptake and fixation by phosphorylation. It is the most widely used radiotracer in positron emission tomography (PET), being used in >90% of scans, and is useful for diagnosis, staging and detection of residual/recurrent cancer. However, there are limits to the utility of FDG, particularly in certain tumour types. The development of new radiotracers to study molecular processes such as proliferation, apoptosis, angiogenesis and hypoxia will complement FDG by providing additional information on the cell biology of tumours. The aim of this paper is to consider how the availability of new tracers, or new applications for existing PET/CT technologies, could deliver clinical benefit in cancer, using breast cancer as a paradigm.

Role of fusion of prone FDG-PET and magnetic resonance imaging of the breasts in the evaluation of breast cancer

The purpose of this study is to report further about the statistically significant results from a prospective study, which suggests that fusion of prone F-18 Fluoro-deoxy-glucose (FDG) positron emission tomography (PET) and magnetic resonance (MR) breast scans increases the positive predictive value (PPV) and specificity for patients in whom the MR outcome alone would be nonspecific. Thirty-six women (mean age, 43 years; range, 24-65 years) with 90 lesions detected on MR consented to undergo a FDG-PET scan. Two blinded readers evaluated the MR and the computer tomography (CT) attenuation-corrected prone FDG-PET scans side-by-side, then after the volumes were superimposed (fused). A semiautomatic, landmark-based program was used to perform nonrigid fusion. Pathology and radiologic follow-up were used as the reference standard. The sensitivity, specificity, PPV, negative predictive value (NPV), and accuracy (with 95% confidence intervals) for MR alone, FDG-PET alone, and fused MR and FDG-PET were calculated. The median lesion size measured from the MR was 2.5 cm (range, 0.5-10 cm). Histologically, 56 lesions were malignant, and 15 were benign. Nineteen lesions were benign after 20-47 months of clinical and radiologic surveillance. The sensitivity of MR alone was 95%, FDG-PET alone was 57%, and fusion was 83%. The increase in PPV from 77% in MR alone to 98% when fused and the increase in specificity from 53% to 97% were statistically significant (p < 0.05). The false-negative rate on FDG-PET alone was 26.7%, and after fusion this number was reduced to 9%. FDG-PET and MR fusions were helpful in selecting which lesion to biopsy, especially in women with multiple suspicious MR breast lesions.

Design study of a high-resolution breast-dedicated PET system built from cadmium zinc telluride detectors

We studied the performance of a dual-panel positron emission tomography (PET) camera dedicated to breast cancer imaging using Monte Carlo simulation. The proposed system consists of two 4 cm thick 12 x 15 cm(2) area cadmium zinc telluride (CZT) panels with adjustable separation, which can be put in close proximity to the breast and/or axillary nodes. Unique characteristics distinguishing the proposed system from previous efforts in breast-dedicated PET instrumentation are the deployment of CZT detectors with superior spatial and energy resolution, using a cross-strip electrode readout scheme to enable 3D positioning of individual photon interaction coordinates in the CZT, which includes directly measured photon depth-of-interaction (DOI), and arranging the detector slabs edge-on with respect to incoming 511 keV photons for high photon sensitivity. The simulation results show that the proposed CZT dual-panel PET system is able to achieve superior performance in terms of photon sensitivity, noise equivalent count rate, spatial resolution and lesion visualization. The proposed system is expected to achieve approximately 32% photon sensitivity for a point source at the center and a 4 cm panel separation. For a simplified breast phantom adjacent to heart and torso compartments, the peak noise equivalent count (NEC) rate is predicted to be approximately 94.2 kcts s(-1) (breast volume: 720 cm(3) and activity concentration: 3.7 kBq cm(-3)) for a approximately 10% energy window around 511 keV and approximately 8 ns coincidence time window. The system achieves 1 mm intrinsic spatial resolution anywhere between the two panels with a 4 cm panel separation if the detectors have DOI resolution less than 2 mm. For a 3 mm DOI resolution, the system exhibits excellent sphere resolution uniformity (sigma(rms)/mean) < or = 10%) across a 4 cm width FOV. Simulation results indicate that the system exhibits superior hot sphere visualization and is expected to visualize 2 mm diameter spheres with a 5:1 activity concentration ratio within roughly 7 min imaging time. Furthermore, we observe that the degree of spatial resolution degradation along the direction orthogonal to the two panels that is typical of a limited angle tomography configuration is mitigated by having high-resolution DOI capabilities that enable more accurate positioning of oblique response lines.

FDG-PET and other imaging modalities for the evaluation of breast cancer recurrence and metastases: a meta-analysis

Background and purpose

Breast carcinoma is the most common cancer in female patients with a propensity for recurrence and metastases. The accuracy of ultrasound (US), computed tomography (CT), magnetic resonance imaging (MRI), scintimammography (SMM) and positron emission tomography (PET) in diagnosing the recurrent and/or breast cancer has never been systematically assessed, and present systematic review was aimed at this issue.

Methods

MEDLINE and EMBASE were searched for articles dealt with detection of recurrent and/or metastatic breast cancer by US, CT, MRI, SMM or PET whether interpreted with or without the use of CT. Histopathologic analysis and/or close clinical and imaging follow-up for at least 6 months were used as golden reference. We extracted data to calculate sensitivity, specificity, summary receiver operating characteristic curves and area under the curve and to test for heterogeneity.

Result

In 42 included studies, US and MRI had highest pooled specificity (0.962 and 0.929, respectively); MRI and PET had highest pooled sensitivity (0.9500 and 0.9530, respectively). The AUC of US, CT, MRI, SMM and PET was 0.9251, 0.8596, 0.9718, 0.9386 and 0.9604, respectively. Results of pairwise comparison between each modality demonstrated that AUC of MRI and PET was higher than that of US or CT, p < 0.05. No statistical significance was found between MRI and PET. There was heterogeneity among studies and evidence of publication bias.

Conclusion

In conclusion, MRI seemed to be a more useful supplement to current surveillance techniques to assess patients with suspected recurrent and/or metastatic breast cancer. If MRI shows an indeterminate or benign lesion or MRI was not applicable, FDG-PET could be performed in addition.

PET, PET/CT, and PET/MR Imaging Assessment of Breast Cancer

This review focuses mainly on clinical applications of PET/CT in patients with breast cancer. It discusses the role of 2-[18F]-fluoro-2-deoxy-D-glucose (FDG) PET/CT (and FDG PET) in the diagnosis and initial staging of breast cancer, in monitoring the response of disease to chemotherapy, and in identifying metastatic and recurrent disease. In addition, it discusses the role of MR imaging and potential future hybrid modalities such as PET/MR imaging.

Incorporation of preprocedural PET into CT-guided radiofrequency ablation of hepatic metastases: a nonrigid image registration validation study

This study evaluates the accuracy of augmenting initial intraprocedural computed tomography (CT) during radiofrequency ablation (RFA) of hepatic metastases with preprocedural positron emission tomography (PET) through a hardware-accelerated implementation of an automatic nonrigid PET-CT registration algorithm. The feasibility of augmenting intraprocedural CT with preprocedural PET to improve localization of CT-invisible but PET-positive tumors with images from actual RFA was explored. Preprocedural PET and intraprocedural CT images from 18 cases of hepatic RFA were included. All PET images in the study originated from a hybrid PET/CT scanner, and PET-CT registration was performed in two ways: (1) direct registration of preprocedural PET with intraprocedural CT and (2) indirect registration of preprocedural CT (i.e., the CT of hybrid PET/CT scan) with intraprocedural CT. A hardware-accelerated registration took approximately 2 min. Calculated registration errors were 7.0 and 8.4 mm for the direct and indirect methods, respectively. Overall, the direct registration was found to be statistically not distinct from that performed by a group of clinical experts. The accuracy, execution speed, and compactness of our implementation of nonrigid image registration suggest that existing PET can be overlaid on intraprocedural CT, promising a novel, technically feasible, and clinically viable approach for PET augmentation of CT guidance of RFA.

Metabolic and vascular features of dynamic contrast-enhanced breast magnetic resonance imaging and (15)O-water positron emission tomography blood flow in breast cancer

RATIONALE AND OBJECTIVES

We sought to (1) describe associations between measures of tumor perfusion by dynamic contrast-enhanced breast magnetic resonance imaging (DCE-MRI), blood flow by (15)O-water positron emission tomography (PET) and metabolism by (18)F-fluorodeoxyglucose ((18)F)-FDG PET and (2) improve our understanding of tumor enhancement on MRI through independent measures of tumor metabolism and blood flow.

MATERIALS AND METHODS

We performed a retrospective analysis of the existing PET and MRI databases from the Departments of Nuclear Medicine and Radiology. We identified patients with locally advanced breast cancer who underwent (15)O-water/(18)F-FDG PET within 1 month of clinical DCE-MRI between February 2004 and August 2006. The (15)O-water PET blood flow and (18)F-FDG metabolic rate and tissue transport constant (K(1)) in the primary malignancy were calculated. DCE-MRI peak percent enhancement and peak signal enhancement ratio (SER) were measured for each tumor. Correlations and regression analysis of these variables were performed.

RESULTS

Fifteen patients with complete PET and DCE-MRI data were included in the analysis cohort. Peak SER correlated significantly with blood flow (r = 0.73, P = .002) and K(1) (r = 0.76, P = .001). However, peak SER did not correlate significantly with FDG metabolic rate (r = 0.44, P = .101). There were no significant correlations between peak percent enhancement and any of the PET parameters.

CONCLUSIONS

Our findings suggest that tumor perfusion, represented by (15)O-water PET blood flow, is an important factor in the MRI enhancement of locally advanced breast cancer. A lack of correlation of FDG metabolic rate with blood flow and DCE-MRI kinetics suggests that (18)F-FDG PET provides complementary metabolic information independent of vascular factors.

Positron Emission Tomography (PET) and breast cancer in clinical practice

The landscape of oncologic practice has changed deeply during the past few years and there is now a need, through a multidisciplinary approach, for imaging to provide accurate evaluation of morphology and function and to guide treatment (Image Guided Therapy). Increasing emphasis has been put on Position Emission Tomography (PET) role in various cancers among clinicians [Juweid ME, Cheson BD. Positron-emission tomography and assessment of cancer therapy. N Engl J Med 2006;354:496-507; Koh DM, Cook GJR, Husband JE. New horizons in oncologic imaging. N Engl J Med 2003;348:25; Tafra L, positron emission tomography (PET) and mammography (PEM) for breast cancer: importance to surgeons. Ann Surg Oncol 2006;14(1):3-13] and patients despite a general context of healthcare expenditure limitation. Positron Emission Tomography has currently a limited role in breast cancer, but also general radiologists and specialists should be aware of these indications, especially when staging aggressive cancers and looking for recurrence. Currently, the hybrid systems associating PET and Computed Tomography (CT) and in the same device [Rohren EM, Turkington TG, Coleman RE. Clinical applications of PET in oncology. Radiology 2004;231:305-32; Blodgett TM, Meltzer CM, Townsend DW. PET/CT: form and function. Radiology 2007;242:360-85; von Schulthess GK, Steinert HC, Hany TF. Integrated PET/CT: current applications and futures directions. Radiology 2006;238(2):405-22], or PET-CT, are more commonly used and the two techniques are adding their potentialities. Other techniques, MRI in particular, may also compete with PET in some instance and as far as ionizing radiations dose limitation is considered, some breast cancers becoming some form of a chronic disease. Breast cancer is a very complex, non-uniform, disease and molecular imaging at large may contribute to a better knowledge and to new drugs development. Ongoing research, Positron Emission Mammography (PEM) and new tracers, are likely to bring improvements in patient care [Kelloff GJ, Hoffman JM, Johnson B, et al. Progress and promise of FDG-PET Imaging for cancer patient management and oncologic drug development. Clin Cancer Res 2005;1(April (8)): 2005].

Evaluation of the combined effects of target size, respiratory motion and background activity on 3D and 4D PET/CT images

Gated (4D) PET/CT has the potential to greatly improve the accuracy of radiotherapy at treatment sites where internal organ motion is significant. However, the best methodology for applying 4D-PET/CT to target definition is not currently well established. With the goal of better understanding how to best apply 4D information to radiotherapy, initial studies were performed to investigate the effect of target size, respiratory motion and target-to-background activity concentration ratio (TBR) on 3D (ungated) and 4D PET images. Using a PET/CT scanner with 4D or gating capability, a full 3D-PET scan corrected with a 3D attenuation map from 3D-CT scan and a respiratory gated (4D) PET scan corrected with corresponding attenuation maps from 4D-CT were performed by imaging spherical targets (0.5-26.5 mL) filled with (18)F-FDG in a dynamic thorax phantom and NEMA IEC body phantom at different TBRs (infinite, 8 and 4). To simulate respiratory motion, the phantoms were driven sinusoidally in the superior-inferior direction with amplitudes of 0, 1 and 2 cm and a period of 4.5 s. Recovery coefficients were determined on PET images. In addition, gating methods using different numbers of gating bins (1-20 bins) were evaluated with image noise and temporal resolution. For evaluation, volume recovery coefficient, signal-to-noise ratio and contrast-to-noise ratio were calculated as a function of the number of gating bins. Moreover, the optimum thresholds which give accurate moving target volumes were obtained for 3D and 4D images. The partial volume effect and signal loss in the 3D-PET images due to the limited PET resolution and the respiratory motion, respectively were measured. The results show that signal loss depends on both the amplitude and pattern of respiratory motion. However, the 4D-PET successfully recovers most of the loss induced by the respiratory motion. The 5-bin gating method gives the best temporal resolution with acceptable image noise. The results based on the 4D scan protocols can be used to improve the accuracy of determining the gross tumor volume for tumors in the lung and abdomen.

PET/MRI hybrid imaging: devices and initial results

The combination of functional and morphological imaging technologies such as positron emission tomography (PET) and X-ray computed tomography (CT) has shown its value in the clinical and preclinical field. However, CT provides only very limited soft-tissue contrast and exposes the examined patient or laboratory animal to a high X-ray radiation dose. In comparison to CT, magnetic resonance tomography (MRI) provides excellent soft-tissue contrast and allows for nuclear magnetic resonance spectroscopy (NMRS) or functional MRI (fMRI). Thus, the combination of PET and MRI has been pursued for several years. First approaches have succeeded using conventional photo multiplier tube (PMT) technology together with light fibers to transfer scintillation light away from the high magnetic field. Latest PET/MRI developments use solid-state light detectors that can be operated even at high magnetic fields. Initial pilot studies with prototype animal PET/MRI systems have shown promising results by combining high resolution morphology with multifunctional information isochronously.

Is there a role for positron emission tomography in breast cancer staging?

Positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose (FDG) is a radiotracer imaging method that is used in the care of patients with cancer. We conducted a nonsystematic review of the literature regarding the applicability of this technique in patients with breast cancer, encompassing the impact of FDG-PET on surgical management, including axillary node staging and sentinel lymph node biopsy; the use of FDG-PET in the evaluation of the primary tumor; the role of FDG-PET in the evaluation of distant metastases both at diagnosis and in the investigation of suspected recurrence; and the ability of FDG-PET to predict treatment response. FDG-PET is not sufficiently sensitive to replace histologic surgical staging of the axilla. Although FDG avidity of the primary tumor has been shown to be an unfavorable indicator, there is insufficient information to recommend its routine use for this indication. FDG-PET is more sensitive than conventional imaging in the detection of metastatic or recurrent disease, but the impact of increased sensitivity on patient care and outcome has not been demonstrated. The data regarding prediction of treatment response are insufficient to reach any conclusion. There are a number of prospective, adequately powered clinical trials currently in progress that should provide more definitive answers regarding the role, if any, of this technique in the management of patients with breast cancer.

Targeting liver lesions for radiofrequency ablation: an experimental feasibility study using a CT-US fusion imaging system

PURPOSE

To investigate the feasibility and validity of real-time guidance using a fusion imaging system that combines ultrasound (US) and computed tomography (CT) in the targeting and subsequent radiofrequency (RF) ablation of a liver target inconspicuous on US.

METHODS AND MATERIALS

The study was designed as an experimental ex vivo study in calf livers with radiopaque internal targets, inconspicuous at US, simulating a focal liver lesion. The study included 2 phases. The initial phase was to examine the feasibility of matching preprocedural volumetric CT data of the calf livers with real-time US using a commercially available multimodality fusion imaging system (Virtual Navigator System, Esaote SpA, Genoa, Italy), and to assess the accuracy of targeting using a 22 gauge cytologic needle. The second phase of the study was to validate such a technique using a 15 gauge RF multitined expandable needle (RITA Medical Systems, Mountain View, CA) and to examine the accuracy of the needle placement relative to the target. The tip of the trocar of the RF needle had to be placed 1 cm from the target and then the hooks had to be deployed to 3 cm. Unenhanced CT of the liver and multiplanar reconstructions were performed to calculate accuracy of positioning, ie, the lateral distance between the needle and the target, the distance between the tip of the trocar of the RF electrode and the target, and the lateral distance between the central tine of the RF electrode and the target.

RESULTS

All calf livers underwent successful CT-US registration with a mean registration error of 3.0 +/- 0.1 mm and 2.9 +/- 0.1 mm in the initial and second phase of the study, respectively. In the initial phase an overall number of 24 insertions were performed after the US-CT guidance. The mean needle to target distance was 1.9 +/- 0.7 mm (range, 0.8-3.0 mm). In the second phase an overall number of 12 ablations were performed. The mean target-trocar distance was 10.3 +/- 2.6 mm. The mean target-central tine lateral distance was 3.9 +/- 0.7 mm (range, 2.9-5.1 mm). After the dissection of the specimen the target was found unchanged in the center of the ablation zone in all cases.

CONCLUSION

Real-time registration and fusion of preprocedure CT volume images with intraprocedure US is feasible and accurate. The study was however conducted in an ideal experimental setting, without patient movements and breathing, and further studies are warranted to validate the system under clinical conditions.