Correlation of measurements from diffusion weighted MR imaging and FDG PET/CT in GIST patients: ADC versus SUV

Purpose

We investigated the correlation relationship between ADCs measured by MRI and SUVs measured by PET/CT of lesions on GIST (gastrointestinal stromal tumor) patients to verify if MR is able to replace or serve as an alternative to PET/CT in GIST staging and treatment monitoring.

Materials and methods

Between September 2010 and January 2011, five patients with histologically proven metastatic GIST in Queen Mary Hospital, Hong Kong were enrolled into our study. All patients underwent both MRI and PET/CT scans at prognosis. Pearson's correlations of twenty-nine lesions were conducted between 5 pairs of ADCs and SUVs values.

Results

Lesions in the liver, peritoneum or bowel loops were found by PET/CT and no extra-abdominal lesion was identified. All twenty-nine lesions are identifiable by MRI with sensitivity of 100%. Significant inverse correlation were found between ADC_mean and SUV_mean (P = 0.006), ADC_mean and SUV_max (P = 0.010), ADC_min and SUV_max (P = 0.014), ADC_min and SUV_mean (P = 0.026), rADC_min and rSUV_max (P = 0.047).

Conclusion

DWI is comparable to PET/CT in visually detecting the GIST lesions’ location. Significant inverse correlations were found between ADCs from DWIBS and SUVs from PET/CT on data of GIST patients. This finding demonstrates that DWI is potentially capable of offering similar information for diagnosis and treatment response evaluating in GIST's patients as PET/CT does. Furthermore, ADC_min, which is determined by single pixel, is not as reliable as ADC_mean, which is weighted average value of the whole lesion volume.     

Diffusion weighted MRI and 18F-FDG PET/CT in non-small cell lung cancer (NSCLC): Does the apparent diffusion coefficient (ADC) correlate with tracer uptake (SUV)?

Introduction

To investigate the potential correlation of the apparent diffusion coefficient assessed by diffusion-weighted MRI (DWI) and glucose metabolism determined by the standardized uptake value (SUV) at 18F-FDG PET/CT in non-small cell lung cancer (NSCLC).

Materials and methods

18F-FDG PET/CT and DWI (TR/TE, 2000/66 ms; b-values, 0 and 500 s/mm²) were performed in 41 consecutive patients with histologically verified NSCLC. Analysing the PET-CT data calculation of the mean (SUV_mean) and maximum (SUV_max) SUV was performed. By placing a region-of-interest (ROI) encovering the entire tumor mean (ADC_mean) and minimum ADC (ADC_min) were determined by two independent radiologists. Results of 18F-FDG PET-CT and DWI were compared on a per-patient basis. For statistical analysis Pearson's correlation coefficient, Bland–Altman and regression analysis were assessed.

Results

Data analysis revealed a significant inverse correlation of the ADC_min and SUV_max (r = −0.46; p = 0.032). Testing the correlation of the ADC_min and SUV_max for each histological subtype separately revealed that the inverse correlation was good for both adenocarcinomas (r = −0.47; p = 0.03) and squamouscell carcinomas (r = −0.71; p = 0.002), respectively. No significant correlation was found for the comparison of ADC_min and SUV_mean (r = −0.29; p = 0.27), ADC_mean vs. SUV_mean (r = −0.28; p = 0.31) or ADC_mean vs. SUV_max (r = −0.33; p = 0.23). The κ-value of 0.88 indicated a good agreement between both observers.

Conclusion

This preliminary study is the first to verify the relation between the SUV and the ADC in NSCLC. The significant inverse correlation of these two quantitative imaging approaches points out the association of metabolic activity and tumor cellularity. Therefore, DWI with ADC measurement might represent a new prognostic marker in NSCLC.     

No correlation between glucose metabolism and apparent diffusion coefficient in diffuse large B-cell lymphoma: a PET/CT and DW-MRI study

Purpose

Both positron emission tomography/computed tomography (PET/CT) and diffusion-weighted magnetic resonance imaging (DW-MRI) are oncologic feasible techniques for evaluating the malignancy of tumors. Standardized uptake value (SUV) is a marker of tumor glucose metabolism detected by PET/CT. Apparent diffusion coefficient (ADC) measured by DWI can provide information about tissue cellularity. The aim of the study was to evaluate the correlation between SUV and ADC in untreated diffuse large B-cell lymphoma (DLBCL).

Materials and methods

Fifteen pre-therapy patients with histologically proven DLBCL underwent PET/CT and DWI examinations within two days. Tumor glucose metabolism was evaluated by the maximum and mean SUV (SUV_max and SUV_mean) on the PET/CT images. The mean ADC value was measured directly on the parametric ADC maps.

Results

In total, 28 lymphoma lesions with best match PET/CT and DWI were identified and evaluated. The mean SUV_max and SUV_mean were 16.8 and 11.1, respectively; the mean ADC was 0.74 × 10⁻³ mm²/s. There was no correlation between the mean ADC and the SUV_max or SUV_mean.

Conclusion

SUV determined from PET/CT and ADC value measured from DWI are different indices for the diagnosis of tumor malignancy, they may provide complimentary functional information of tumor tissue.     

Functional imaging of head and neck squamous cell carcinoma with diffusion-weighted MRI and FDG PET/CT: quantitative analysis of ADC and SUV

Purpose

Head and neck squamous cell carcinoma (HNSCC) may cause a decreased apparent diffusion coefficient (ADC) on diffusion-weighted magnetic resonance imaging (DW MRI) and an increased standardized uptake value (SUV) on fluorodeoxyglucose (FDG) positron emission tomography (PET/CT). We analysed the reproducibility of ADC and SUV measurements in HNSCC and evaluated whether these biomarkers are correlated or independent.

Methods

This retrospective analysis of DW MRI and FDG PET/CT data series included 34 HNSCC in 33 consecutive patients. Two experienced readers measured tumour ADC and SUV values independently. Statistical comparison and correlation with histopathology was done. Intra- and inter-observer agreement for ADC and SUV measurements was assessed.

Results

Intraclass correlation coefficient (ICC) analysis showed almost perfect reproducibility (>0.90) for ADC_mean, ADC_min, SUV_max and SUV_mean values for intra-observer and inter-observer agreement. Mean ADC_mean and ADC_min in HNSCC were 1.05?±?0.34 × 10^?3?mm²/s and 0.65?±?0.29 × 10^?3?mm²/s, respectively. Mean SUV_mean and mean SUV_max were 7.61?±?3.87 and 12.8?±?5.0, respectively. Although statistically not significant, a trend towards higher SUV and lower ADC was observed with increasing tumour dedifferentiation. Pearson’s correlation analysis showed no significant correlation between ADC and SUV measurements (r ?0.103, ?0.051; p 0.552, 0.777).

Conclusion

Our data suggest that ADC and SUV values are reproducible and independent biomarkers in HNSCC.     

Prognostic value of FDG-PET and DWI in breast cancer

Objective

To investigate the prognostic value of preoperative FDG-PET/CT and diffusion weighted imaging (DWI) in patients with breast cancer.

Methods

A total of 73 patients with newly diagnosed invasive breast cancer who had undergone preoperative whole-body FDG-PET/CT and 3-Tesla breast MRI including DWI followed by surgery were identified. Effects of primary tumor PET parameters [maximum standardized uptake value (SUV_max), mean SUV (SUV_mean), metabolic tumor volume (MTV), and total lesion glycolysis (TLG)] and DWI parameters [mean apparent diffusion coefficient (ADC_mean) and minimum ADC (ADC_min)] including clinicopathologic factors on disease-free survival (DFS) were retrospectively evaluated using the log-rank and Cox methods.

Results

After a median overall follow-up of 32.3 months in all patients, 6 (8.2%) of the 73 patients had recurrence. Receiver operating characteristic curve analysis and log-rank tests showed that patients with a high primary tumor SUV_max (≥?3.60), MTV (≥?3.15), and TLG (≥?16.0) had a significantly lower DFS rate than those with a low SUV_max (<?3.60), MTV (<?3.15), and TLG (<?16.0), respectively (p?=?0.0054, p?=?0.0054, and p?<?0.0001, respectively). SUV_mean, ADC_mean, and ADC_min were not significantly associated with recurrence. Univariate analysis showed that SUV_max (p?=?0.0054), MTV (p?=?0.0054), TLG (p?<?0.0001), tumor size (p?=?0.0083), estrogen receptor negativity (p?=?0.046), progesterone receptor negativity (p?=?0.0023), human epidermal growth factor receptor 2 positivity (p?=?0.043), and the presence of axillary lymph node metastasis (p?=?0.0037) were also significantly associated with recurrence. However, in multivariate analysis, none of them were an independent factor.

Conclusions

The preoperative SUV_max, MTV, and TLG of primary breast cancer are prognostic factors for recurrence, whereas ADC values are not.

     

Monitoring the neoadjuvant therapy response in gynecological cancer patients using FDG PET

Purpose We retrospectively evaluated the ability of FDG PET to predict the response of primary tumor to chemotherapy or chemoradiotherapy in patients with gynecological cancer. Methods FDG PET examinations were performed before and after completion of chemotherapy or chemoradiotherapy in 21 patients with advanced gynecological cancer (uterine cancer, n = 13; ovarian cancer, n = 8). PET imaging was performed at 1 h after injection. Semi-quantitative analysis was performed using the standardized uptake value (SUV) at the primary tumor for both before and after therapy (SUV_before and SUV_after, respectively). Percent change value was calculated according to the following equation: . Based on histopathological analysis of the specimens obtained at surgery, patients were classified as responders or non-responders. Results Ten patients were found to be responders and 11 to be non-responders. SUV_after in responders was significantly lower than that in non-responders (p < 0.005). Taking an arbitrary SUV_after of 3.8 as the cutoff for differentiating between responders and non-responders, FDG PET showed a sensitivity of 90%, a specificity of 63.6%, and an accuracy of 76.2%. The percent change value in the responders was significantly higher than that in the non-responders (p < 0.0005). Taking an arbitrary percent change of 65 as the cutoff for differentiating between responders and non-responders, FDG PET showed a sensitivity of 90%, a specificity of 81.8%, and an accuracy of 85.7%. Conclusion These findings suggest that FDG PET-derived parameters including SUV and especially percent change value may have the potential to predict response to chemotherapy or chemoradiotherapy in patients with advanced gynecological cancer.     

<Superscript>11</Superscript>C-methionine (MET) and <Superscript>18</Superscript>F-fluorothymidine (FLT) PET in patients with newly diagnosed glioma

Purpose  The purpose of this prospective study was to clarify the individual and combined role of l-methyl-¹¹C-methionine-positron emission tomography (MET-PET) and 3′-deoxy-3′-[¹⁸F]fluorothymidine (FLT)-PET in tumor detection, noninvasive grading, and assessment of the cellular proliferation rate in newly diagnosed histologically verified gliomas of different grades. Materials and methods  Forty-one patients with newly diagnosed gliomas were investigated with MET-PET before surgery. Eighteen patients were also examined with FLT-PET. MET and FLT uptakes were assessed by standardized uptake value of the tumor showing the maximum uptake (SUV_max), and the ratio to uptake in the normal brain parenchyma (T/N ratio). All tumors were graded by the WHO grading system using surgical specimens, and the proliferation activity of the tumors were determined by measuring the Ki-67 index obtained by immunohistochemical staining. Results  On semiquantitative analysis, MET exhibited a slightly higher sensitivity (87.8%) in tumor detection than FLT (83.3%), and both tracers were 100% sensitive for malignant gliomas. Low-grade gliomas that were false negative on MET-PET also were false negative on FLT-PET. Although the difference of MET SUV_max and T/N ratio between grades II and IV gliomas was statistically significant (P < 0.001), there was a significant overlap of MET uptake in the tumors. The difference of MET SUV_max and T/N ratio between grades II and III gliomas was not statistically significant. Low-grade gliomas with oligodendroglial components had relatively high MET uptake. The difference of FLT SUV_max and T/N ratio between grades III and IV gliomas was statistically significant (P < 0.01). Again, the difference of FLT SUV_max and T/N ratio between grades II and III gliomas was not statistically significant. Grade III gliomas with non-contrast enhancement on MR images had very low FLT uptake. In 18 patients who underwent PET examination with both tracers, a significant but relatively weak correlation was observed between the individual SUV_max of MET and FLT (r = 0.54, P < 0.05) and T/N ratio of MET and FLT (r = 0.56, P < 0.05). Total FLT uptake in the tumor had a higher correlation (r = 0.89, P < 0.001) with Ki-67 proliferation index than MET uptake (r = 0.49, P < 0.01). Conclusions  PET studies using MET and FLT are useful for tumor detection in newly diagnosed gliomas. However, there is no complimentary information in tumor detection with simultaneous measurements of MET- and FLT-PET in low grade gliomas. FLT-PET seems to be superior than MET-PET in noninvasive tumor grading and assessment of proliferation activity in gliomas of different grades.     

Tumor hypoxia and microscopic diffusion capacity in brain tumors: A comparison of 62Cu-Diacetyl-Bis (N4-Methylthiosemicarbazone) PET/CT and diffusion-weighted MR imaging

Objectives

The aim of this study was to clarify the relationship between tumor hypoxia and microscopic diffusion capacity in primary brain tumors using ⁶²Cu-Diacetyl-Bis (N4-Methylthiosemicarbazone) (⁶²Cu-ATSM) PET/CT and diffusion-weighted MR imaging (DWI).

Methods

This study was approved by the institutional human research committee and was HIPAA compliant, and informed consent was obtained from all patients. ⁶²Cu-ATSM PET/CT and DWI were performed in a total of 40 primary brain tumors of 34 patients with low grade glioma (LGG, n?=?13), glioblastoma (GBM, n?=?20), and primary central nervous system lymphoma (PCNSL, n?=?7). ⁶²Cu-ATSM PET/CT parameters and apparent diffusion coefficient (ADC) obtained by DWI were compared.

Results

High intensity signals by ⁶²Cu-ATSM PET/CT and DWI in patients with GBM and PCNSL, and low intensity signals in LGG patients were observed. An inverse correlation was found between maximum SUV (SUV_max) and minimum ADC (ADC_min) (r?=??0.583, p?<?0.0001), and between tumor/brain ratio (T/B_ratio) and ADC_min for all tumors (r?=??0.532, p?<?0.0001). Both SUV_max and T/B_ratio in GBM were higher than LGG (p?<?0.0001 and p?<?0.0001), and those in PCNSL were also higher than GBM (p?=?0.033 and p?=?0.044). The ADC_min was lower in GBM (p?=?0.011) and PCNSL (p?=?0.01) than in LGG, while no significant difference was found between GBM and PCNSL (p?=?0.90).

Conclusion

Tumor hypoxia assessed by ⁶²Cu-ATSM PET/CT correlated with microscopic diffusion capacity obtained by DWI in brain tumors. Both ⁶²Cu-ATSM PET/CT and DWI were considered feasible imaging methods for grading glioma. However, ⁶²Cu-ATSM PET/CT provided additional diagnostic information to differentiate between GBM and PCNSL.     

Detection of gastric cancer using <Superscript>18</Superscript>F-FLT PET: comparison with <Superscript>18</Superscript>F-FDG PET

Purpose  We prospectively investigated the feasibility of 3′-deoxy-3′-¹⁸F-fluorothymidine (FLT) positron emission tomography (PET) for the detection of gastric cancer, in comparison with 2-deoxy-2-¹⁸F-fluoro-d-glucose (FDG) PET, and determined the degree of correlation between the two radiotracers and proliferative activity as indicated by Ki-67 index. Methods  A total of 21 patients with newly diagnosed advanced gastric cancer were examined with FLT PET and FDG PET. Tumour lesions were identified as areas of focally increased uptake, exceeding that of surrounding normal tissue. For semiquantitative analysis, the maximal standardized uptake value (SUV) was calculated. Results  For detection of advanced gastric cancer, the sensitivities of FLT PET and FDG PET were 95.2% and 95.0%, respectively. The mean (±SD) SUV for FLT (7.0 ± 3.3) was significantly lower than that for FDG (9.4 ± 6.3 p < 0.05). The mean FLT SUV and FDG SUV in nonintestinal tumours were higher than in intestinal tumours, although the difference was not statistically significant. The mean (±SD) FLT SUV in poorly differentiated tumours (8.5 ± 3.5) was significantly higher than that in well and moderately differentiated tumours (5.3 ± 2.1; p < 0.04). The mean FDG SUV in poorly differentiated tumours was higher than in well and moderately differentiated tumours, although the difference was not statistically significant. There was no significant correlation between Ki-67 index and either FLT SUV or FDG SUV. Conclusion  FLT PET showed as high a sensitivity as FDG PET for the detection of gastric cancer, although uptake of FLT in gastric cancer was significantly lower than that of FDG.     

[<Superscript>18</Superscript>F]FDG-PET predicts complete pathological response of breast cancer to neoadjuvant chemotherapy

Purpose To evaluate, in breast cancer patients treated by neoadjuvant chemotherapy, the predictive value of reduction in FDG uptake with regard to complete pathological response (pCR). Methods Forty-seven women with non-metastatic, non-inflammatory, large or locally advanced breast cancer were included. Tumour uptake of FDG was evaluated before and after the first course of neoadjuvant chemotherapy. Four indices were used: maximal and average SUV without or with correction by body surface area and glycaemia (SUV_max, SUV_avg, SUV_max-BSA-G and SUV_avg-BSA-G, respectively). The predictive value of reduction in FDG uptake with respect to pCR was studied by logistic regression analysis. Relationships between baseline [¹⁸F]FDG uptake and prognostic parameters were assessed. Results The relative decrease in FDG uptake (ΔSUV) after the first course of neoadjuvant chemotherapy was significantly greater in the pCR group than in the non-pCR group (p < 0.000066). The four FDG uptake indices were all strongly correlated with each other. A decrease in SUV_max-BSA-G of 85.4% ± 21.9% was found in pCR patients, versus 22.6% ± 36.6% in non-pCR patients. ΔSUV_max-BSA-G <−60% predicted the pCR with an accuracy of 87% and ΔSUVs were found to be only factors predictive of the pCR at multivariate analysis. An elevated baseline SUV was associated with high mitotic activity (p < 0.0016), tumour grading (p < 0.004), high nuclear pleomorphism score (p < 0.03) and negative hormonal receptor status (p < 0.005). Conclusion In breast cancer patients, after only one course of neoadjuvant chemotherapy the reduction in FDG uptake is an early and powerful predictor of pCR.     

Risk assessment in liposarcoma patients based on FDG PET imaging

Purpose Tumor grade and subtype are considered standard parameters for risk assessment in patients with liposarcoma. The aim of this study was to assess the clinical value of [¹⁸F]fluorodeoxyglucose (FDG) PET-derived maximum standardized uptake value (SUV_max) for prediction of outcome in liposarcoma patients.Methods ¹⁸F-FDG PET was performed in 54 patients with liposarcoma prior to therapy. SUV_max was calculated for each tumor and results were correlated with tumor grade, subtype, and relapse-free survival.Results SUV_max ranged from 0.4 to 15.9 (mean 3.6) and was significantly lower in grade I than in grade II and grade III tumors. SUV_max was 2.3±1.7, 3.5±1.5, 4.8±2.5, and 5.6±5.8 in well-differentiated, myxoid/round cell, dedifferentiated, and pleomorphic subtypes, respectively. Borderline differences (p=0.059) were found between tumor SUV_max in patients with and without relapse. Using a SUV of 3.6 as cut-off, the accuracy in predicting a relapse was 75%. Tumor grade yielded a lower accuracy for predicting relapse (50%), as did tumor subtype (35%). In Kaplan-Meier survival analysis, patients with a SUV_max >3.6 had a significantly shorter disease-free survival of 21 months compared with 44 months in patients with a SUV_max ≤3.6. Tumor grading and tumor subtype did not yield significant differences.Conclusion Pretherapy tumor SUV obtained by FDG PET imaging was a more useful parameter for risk assessment in liposarcoma than tumor grade or subtype. A SUV_max of more than 3.6 resulted in a significantly reduced disease-free survival and identified patients at high risk for developing early local recurrences or metastatic disease.     

Does chemotherapy influence the quantification of SUV when contrast-enhanced CT is used in PET/CT in lymphoma?

Purpose In patients with lymphoma, we investigated the impact of contrast-enhanced CT on PET attenuation correction in lesions and normal tissues, particularly when PET/CT was performed after chemotherapy. Methods Fifty patients (51±18 years) with Hodgkin’s disease (n=17) or non-Hodgkin lymphomas (n=33) were studied before and after chemotherapy. PET/CT scans were performed 60 min after injection of FDG. Iopamiron 300 (iopamidol, 1.5 cc/kg) was injected immediately afterwards, followed 50 s later by a second craniocaudal CT (CT+). PET images were successively reconstructed using the unenhanced CT (PET−) and the CT+ (PET+) for attenuation correction, using iterative reconstruction (4 iterations, 8 subsets, 5 mm post-filtering). HU_mean, SUV_max and SUV_mean were measured before and after chemotherapy in ten non-tumoural ROIs [aorta, femur, kidney, lung, iliopsoas muscle, occipital cortex, T12 vertebra, liver, spleen and inferior vena cava (IVC)] and in tumoural lymphadenopathies or malignant tissues (n=397 and 51 VOIs respectively before and after chemotherapy) using a 3D-thresholding method (identical threshold for PET− and PET+). ROIs were defined on the PET− and automatically applied on the unenhanced CT (CT−), the CT+ and the PET+. Results In the non-tumoural tissues, HU_mean increased significantly in the CT+ compared with the CT− in the vessels and the highly vascularised organs, and slight increases were observed in the occipital cortex (+11%), the iliopsoas muscle (+6%) and the femur (+3%). SUV_max increased significantly in the PET+ compared with the PET− in the aorta (+14%), the liver (+10%), the spleen (+10%) and the IVC (+12%). SUV_mean increased significantly in the PET+ compared with the PET− in the aorta (+15%), the kidney (+13%), the liver (+11%), the spleen (10%) and the IVC (+12%). In the lesions, HU_mean was not significantly different before and after chemotherapy, whatever the normal region considered. SUV_max increased significantly after treatment in the T12 vertebra (+12%). SUV_mean increased significantly after treatment in the T12 vertebra (+13%) and in the liver (+12%). HU_mean increased significantly in the CT+ compared with the CT− in the lesions (+55%) before chemotherapy. SUV_max and SUV_mean increased significantly in the PET+ compared with the PET− in the lesions (+4%) only before chemotherapy. No significant difference was seen in measurements (HU_mean, SUV_max and SUV_mean) after chemotherapy. Conclusion Our study demonstrates that use of enhanced CT for attenuation correction has a negligible effect on quantification at staging and after chemotherapy. A “single-shot” enhanced PET/CT may thus be performed in the evaluation of patients with lymphoma at staging, during treatment and at follow-up.     

Quantitative evaluation of bone metastases from prostate cancer with simultaneous [18F] choline PET/MRI: combined SUV and ADC analysis

Objective

To quantitatively analyze bone metastases from prostate cancer and correlate the apparent diffusion coefficients (ADCs) and standardized uptake values (SUVs).

Methods

Fifty-five patients with biopsy-proven prostate cancer or suspected recurrent prostate cancer were examined with simultaneous [¹⁸F] choline Positron emission tomography (PET)/MRI at 3 T. In 11 patients, thirty-two PET-positive bone lesions could be identified that were located in the field-of-view of the Diffusion weighted imaging-sequence. Region-of-interest and volume-of-interest analyses were performed to measure the mean and minimal ADCs and to assess maximum and mean SUVs of every bone lesion. Correlations between maximum and mean SUVs and mean and minimal ADCs were calculated.

Results

The SUV_max of all lesions was 5.5 ± 3.1 (mean ± SD). The SUV_mean was 1.8 ± 0.9. The mean ADC (ADC_mean) of all lesions was 0.67 ± 0.13 × 10^?3 mm²/s. The minimal ADC (ADC_min) of all lesions was 0.56 ± 0.14 × 10^?3 mm²/s. There was a moderate but significant inverse correlation of SUV_max vs. ADC_mean with a correlation coefficient of ?0.4 (p = 0.02). There was also a significant inverse correlation of SUV_max vs. ADC_min with r = ?0.41 (p = 0.02).

Conclusion

Our initial results demonstrate a moderate but significant inverse correlation between increased choline metabolism and ADC values of bone metastases from prostate cancer. Further research on a multimodality approach using simultaneous PET/MRI in bone metastasis of prostate cancer seems to be justified.     

Correlation of minimum apparent diffusion coefficient with maximum standardized uptake on fluorodeoxyglucose PET-CT in patients with rectal adenocarcinoma

PURPOSE

The aim of this study was to retrospectively assess the correlation between minimum apparent diffusion coefficient (ADC_min) values obtained from diffusion-weighted magnetic resonance imaging (MRI) and maximum standardized uptake values (SUV_max) obtained from positron emission tomography-computed tomography (PET-CT) in rectal cancer.

MATERIALS AND METHODS

Forty-one patients with pathologically confirmed rectal adenocarcinoma were included in this study. For preoperative staging, PET-CT and pelvic MRI with diffusion-weighted imaging were performed within one week (mean time interval, 3±1 day). For ADC measurements, the region of interest (ROI) was manually drawn along the border of each hyperintense tumor on b=1000 s/mm² images. After repeating this procedure on each consecutive tumor-containing slice to cover the entire tumoral area, ROIs were copied to ADC maps. ADC_min was determined as the lowest ADC value among all ROIs in each tumor. For SUV_max measurements, whole-body images were assessed visually on transaxial, sagittal, and coronal images. ROIs were determined from the lesions observed on each slice, and SUV_max values were calculated automatically. The mean values of ADC_min and SUV_max were compared using Spearman’s test.

RESULTS

The mean ADC_min was 0.62±0.19×10⁻³ mm²/s (range, 0.368–1.227×10⁻³ mm²/s), the mean SUV_max was 20.07±9.3 (range, 4.3–49.5). A significant negative correlation was found between ADC_min and SUV_max (r=−0.347; P = 0.026).

CONCLUSION

There was a significant negative correlation between the ADC_min and SUV_max values in rectal adenocarcinomas.Diffusion-weighted imaging (DWI) is a widely used technique for disease evaluation in oncology (1, 2). In rectal cancer, the applications of DWI include tumor detection, tumor characterization, distinguishing tumor tissue from nontumor tissue, and monitoring and predicting treatment response (3–8). For local staging of rectal cancer, adding DWI to conventional magnetic resonance imaging (MRI) yields better identification of tumor borders and locoregional lymph nodes than conventional MRI alone (9, 10).The apparent diffusion coefficient (ADC) map obtained from DWI shows the freedom of water diffusion, and values calculated on the map are useful parameters in tissue characterization. By performing diffusion-weighted (DW) MRI with at least two diffusion weightings, or b values, the differential signal attenuation at different b values can be used to calculate the ADC (2). Regardless of the tumor type and location, the ADC values reflect tumor morphology, including the cellular density, integrity of cell membrane, and nuclear-to-cytoplasm ratio (11, 12).Positron emission tomography/computed tomography (PET-CT) has become a crucial method in cancer imaging, both for diagnosis and staging, as well as for offering prognostic information based on tumor response. In PET-CT, the standardized uptake value (SUV) is a measure of fluorodeoxyglucose (FDG) uptake, which has been shown to be helpful in establishing the metabolic activity level of a tumor (13–15).Both ADC and SUV have been used as important imaging parameters to supplement visual interpretation. To our knowledge, few studies have evaluated the relationship between ADC and SUV in cancer patients (16–18). The aim of the present study was to retrospectively assess the correlation between the minimum ADC (ADC_min) on DWI and maximum SUV (SUV_max) values from FDG PET-CT in rectal cancer.     

Target volume definition for <Superscript>18</Superscript>F-FDG PET-positive lymph nodes in radiotherapy of patients with non-small cell lung cancer

Purpose FDG PET is increasingly used in radiotherapy planning. Recently, we demonstrated substantial differences in target volumes when applying different methods of FDG-based contouring in primary lung tumours (Nestle et al., J Nucl Med 2005;46:1342–8). This paper focusses on FDG-positive mediastinal lymph nodes (LN_PET). Methods In our institution, 51 NSCLC patients who were candidates for radiotherapy prospectively underwent staging FDG PET followed by a thoracic PET scan in the treatment position and a planning CT. Eleven of them had 32 distinguishable non-confluent mediastinal or hilar nodal FDG accumulations (LN_PET). For these, sets of gross tumour volumes (GTVs) were generated at both acquisition times by four different PET-based contouring methods (visual: GTV_vis; 40% SUV_max: GTV₄₀; SUV=2.5: GTV_2.5; target/background (T/B) algorithm: GTV_bg). Results All differences concerning GTV sizes were within the range of the resolution of the PET system. The detectability and technical delineability of the GTVs were significantly better in the late scans (e.g. p = 0.02 for diagnostic application of SUV_max = 2.5; p = 0.0001 for technical delineability by GTV_2.5; p = 0.003 by GTV₄₀), favouring the GTV_bg method owing to satisfactory overall applicability and independence of GTVs from acquisition time. Compared with CT, the majority of PET-based GTVs were larger, probably owing to resolution effects, with a possible influence of lesion movements. Conclusion For nodal GTVs, different methods of contouring did not lead to clinically relevant differences in volumes. However, there were significant differences in technical delineability, especially after early acquisition. Overall, our data favour a late acquisition of FDG PET scans for radiotherapy planning, and the use of a T/B algorithm for GTV contouring.     

Dual-time point PET/CT with F-18 FDG for the differentiation of malignant and benign bone lesions

Purpose  The purpose of the present study was to evaluate whether 2-fluoro[fluorine-18]-2-deoxy-d-glucose (F-18 FDG) positron emission tomography (PET) could differentiate malignant and benign bone lesions and whether obtaining delayed F-18 FDG PET images could improve the accuracy of the technique. Methods  In a prospective study, 67 patients with bone lesions detected by computed tomography (CT) or magnetic resonance imaging were included. Whole body PET/CT imaging was performed at 1 h (early) after the F-18 FDG injection and delayed imaging at 2 h post injection was performed only in the abnormal region. Semiquantitative analysis was performed using maximum standardized uptake value (SUV_max), obtained from early and delayed images (SUV_maxE and SUV_maxD, respectively). The retention index (RI) was calculated according to the equation: RI = (SUV_maxD − SUV_maxE) × 100/SUV_maxE. Histopathology of surgical specimens and follow-up data were used as reference criteria. The SUV_maxE and RI were compared between benign and malignant lesions. Results  The final diagnoses revealed 53 malignant bone lesions in 37 patients and 45 benign lesions in 30 patients. There were statistically significant differences in the SUV_maxE between the malignant and benign lesions (P = 0.03). The mean SUV_maxE was 6.8 ± 4.7 for malignant lesions and 4.5 ± 3.3 for benign lesions. However, a considerable overlap in the SUV_maxE was observed between some benign and malignant tumors. With a cutoff value of 2.5 for the SUV_maxE, the sensitivity, specificity, and accuracy were 96.0%, 44.0%, and 72.4%, respectively. The positive predictive value (PPV) and negative predictive value (NPV) were 67.1% and 90.9%, respectively. There were significant differences in the RI between the malignant and benign lesions (P = 0.004). But there was overlap between the two groups. The mean RI was 7 ± 11 for the benign lesions and 18 ± 11 for the malignant lesions. When an RI of 10 was used as the cutoff point, the sensitivity, specificity, and accuracy were 90.6%, 76.0%, and 83.7.0%, respectively. The PPV and NPV were 81.4% and 87.1%, respectively. Conclusions  The results of this study indicate that dual-time point F-18 FDG PET may provide more help in the differentiation of malignant tumors from benign ones.     

Correlation of <Superscript>18</Superscript>F-FLT and <Superscript>18</Superscript>F-FDG uptake on PET with Ki-67 immunohistochemistry in non-small cell lung cancer

Purpose The nucleoside analogue 3′-deoxy-3′-¹⁸F-fluorothymidine (FLT) has recently been introduced for imaging cell proliferation with positron emission tomography (PET). We prospectively evaluated whether FLT uptake reflects proliferative activity as indicated by the Ki-67 index in non-small cell lung cancer (NSCLC), in comparison with 2-deoxy-2-¹⁸F-fluoro-D-glucose (FDG). Methods A total of 18 patients with newly diagnosed NSCLC were examined with both FLT PET and FDG PET. PET imaging was performed at 60 min after each radiotracer injection. Tumour lesions were identified as areas of focally increased uptake, exceeding background uptake in the lungs. For semi-quantitative analysis, the maximum standardised uptake value (SUV) was calculated. Proliferative activity as indicated by the Ki-67 index was estimated in tissue specimens. Immunohistochemical findings were correlated with SUVs. Results The sensitivity of FLT and FDG PET for the detection of lung cancer was 72% and 89%, respectively. Four of the five false-negative FLT PET findings occurred in bronchiolo-alveolar carcinoma. The mean FLT SUV was significantly lower than the mean FDG SUV. A significant correlation was observed between FLT SUV and Ki-67 index (r = 0.77; p < 0.0002) and for FDG SUV (r = 0.81; p < 0.0001). Conclusion The results of this preliminary study suggest that, compared with FDG, FLT may be less sensitive for primary staging in patients with NSCLC. Although FLT uptake correlated significantly with proliferative activity in NSCLC, the correlation was not better than that for FDG uptake.     

Combined pre-treatment MRI and 18F-FDG PET/CT parameters as prognostic biomarkers in patients with cervical cancer

Objective

To determine the associations of quantitative parameters derived from multiphase contrast-enhanced magnetic resonance imaging (CE-MRI), diffusion-weighted (DW) MRI and 18F-fluorodeoxyglucose (18F-FDG) positron-emission tomography/computed tomography (PET/CT) with clinico-histopathological prognostic factors, disease-free survival (DFS) and overall survival (OS) in patients with cervical cancer.

Methods and materials

Our institutional review board approved this retrospective study of 49 patients (median age, 45 years) with histopathologically proven IB-IVB International Federation of Gynecology and Obstetrics (FIGO) cervical cancer who underwent pre-treatment pelvic MRI and whole-body 18F-FDG PET/CT between February 2009 and May 2012. Maximum diameter (_maxTD), percentage enhancement (PE) and mean apparent diffusion coefficient (ADC_mean) of the primary tumor were measured on MRI. Maximum standardized uptake value (SUV_max), metabolic tumor volume (MTV), total lesion glycolysis (TLG) were measured on 18F-FDG PET/CT. Correlations between imaging metrics and clinico-histopathological parameters including revised 2009 FIGO stage, tumor histology, grade and lymph node (LN) metastasis at diagnosis were evaluated using the Wilcoxon rank sum test. Cox modeling was used to determine associations with DFS and OS.

Results

Median follow-up was 17 months. 41 patients (83.6%) were alive. 8 patients (16.3%) died of disease. Progression/recurrence occurred in 17 patients (34.6%). Significant differences were observed in ADC_mean, SUV_max, MTV and TLG according to FIGO stage (p < 0.001–0.025). There were significant correlations between ADC_mean, MTV, TLG and LN metastasis (p = 0.017–0.032). SUV_max was not associated with LN metastasis. FIGO stage (p = 0.017/0.033), LN metastases (p = 0.001/0.020), ADC_mean (p = 0.007/0.020) and MTV (p = 0.014/0.026) were adverse predictors of both DFS/OS. _maxTD (p = 0.005) and TLG (p = 0.024) were adverse predictors of DFS. PE and SUV_max did not correlate with DFS or OS (p = 0.18–0.72).

Conclusions

Quantitative parameters derived from pre-treatment DW-MRI (ADC_mean) and from 18F-FDG PET/CT (MTV and TLG) were associated with high-risk features and may serve as prognostic biomarkers of survival in patients with cervical cancer.     

18F-FDG PET for the evaluation of thymic epithelial tumors: Correlation with the World Health Organization classification in addition to dual-time-point imaging

Purpose  Our aim was to determine dual-phase ¹⁸F-FDG PET imaging features for various subtypes of thymic epithelial tumors based on the World Health Organization classification. Methods  Forty-six patients with histologically verified thymic epithelial tumors [23 with low-risk tumors (4 with type A, 16 with AB, and 3 with B1) and 23 with high-risk tumors (7 with B2, 5 with B3, and 11 with thymic carcinoma] were enrolled in this study. All patients were injected with ¹⁸F-FDG.; after 1 h, they underwent scanning; after 3 h, 23 patients underwent an additional scanning. The maximum standard uptake value (SUV_max) and the retention index (RI%) of the lesions were determined. Results  The early and delayed SUV_max values in the patients with high-risk tumors [early SUV_max (mean: 6.0) and delayed SUV_max (mean: 7.4)] were both significantly larger than those in patients with low-risk tumors [early SUV_max (mean: 3.2) and delayed SUV_max (mean: 3.4)] (P < 0.05). Early SUV_max values of greater than 7.1 differentiated thymic carcinomas from other types of tumors. For the histological differentiation between high-risk tumors and low-risk tumors, an early SUV_max value of 4.5 was used as the cutoff. The sensitivity, specificity, and accuracy were 78.3, 91.3, and 84.8%, respectively. Conclusion  High SUV values (early SUV > 4.5) suggest the presence of high-risk tumors. A very high SUV value (early SUV > 7.1) is useful for the differentiation of thymic carcinomas from other types of tumors. The delayed SUV values were higher than the early SUV values in all types of tumors.     

Combination of diffusion-weighted imaging and arterial spin labeling at 3.0 T for the clinical staging of nasopharyngeal carcinoma

PurposeTo probe the utility of diffusion-weighted imaging (DWI) and 3D arterial spin labeling (ASL) in assessing the clinical stage of nasopharyngeal carcinoma (NPC).Materials and methodsThis prospective study included sixty-five newly diagnosed NPC patients who underwent DWI and 3D ASL scans on a 3.0-T magnetic resonance imaging (MRI) system. The apparent diffusion coefficient (ADC) and the tumor blood flow (TBF) of NPC were measured. Tumors were classified as low or high T, N and American Joint Committee on Cancer (AJCC) stages. Student's t-test was used to evaluate the differences between tumors with low and high clinical stages. Pearson correlation analyses were performed to determine the correlation between MRI parameters and clinical stages. Receiver operating characteristic (ROC) curves were then used to evaluate diagnostic capability.ResultsHigh T stage (T3/4) NPC showed significantly lower ADC_min (P = 0.000) and higher TBF_max (P = 0.003) and TBF_mean (P = 0.008) values than low T stage (T1/2) NPC. High N stage (N2/3) NPC showed significantly lower ADC_min values (P = 0.023) than low N stage (N0/1) NPC. High AJCC stage (III/IV) NPC showed significantly lower ADC_min (P = 0.000) and higher TBF_max (P = 0.005) and TBF_mean (P = 0.011) values than low AJCC stage (I/II) NPC. ADC_min values showed moderate negative correlations with T stage (r = −0.512, P = 0.000), N stage (r = −0.281, P = 0.023), and AJCC stage (r = −0.494, P = 0.000). TBF_max values showed moderate positive correlations with T stage (r = 0.369, P = 0.003) and AJCC stage (r = 0.346, P = 0.005). Compared with ADC_min and TBF_max alone, the combination of ADC_min and TBF_max improved the accuracy from 72.3% and 75.4% to 78.5%, respectively, for T staging, as well as from 72.3% and 69.2% to 83.1% for AJCC staging.ConclusionsADC_min and TBF_max values in patients with NPC could help evaluate clinical stages. ADC_min and TBF_max values combined could clearly improve the accuracy in the assessment of AJCC stage.