Whole-body MRI for the detection of bone marrow involvement in lymphoma: prospective study in 116 patients and comparison with FDG-PET

Objective

To assess and compare the value of whole-body MRI with FDG-PET for detecting bone marrow involvement in lymphoma.

Methods

A total of 116 patients with newly diagnosed lymphoma prospectively underwent whole-body MRI and blind bone marrow biopsy (BMB) of the posterior iliac crest. Of 116 patients, 80 also underwent FDG-PET. Patient-based sensitivities of whole-body MRI for detecting bone marrow involvement were calculated using BMB as reference standard and compared with FDG-PET in aggressive and indolent lymphomas separately.

Results

Sensitivity of whole-body MRI in all lymphomas was 45.5 % [95 % confidence interval (CI): 29.8–62.0 %]. Sensitivity of whole-body MRI in aggressive lymphoma [88.9 % (95 % CI: 54.3–100 %)] was significantly higher (P?=?0.0029) than that in indolent lymphoma [23.5 % (95 % CI: 9.1–47.8 %)]. Sensitivity of FDG-PET in aggressive lymphoma [83.3 % (95 % CI: 41.8–98.9 %)] was also significantly higher (P?=?0.026) than that in indolent lymphoma [12.5 % (95 % CI: 0–49.2 %)]. There were no significant differences in sensitivity between whole-body MRI and FDG-PET (P?=?1.00)

Conclusion

Sensitivity of whole-body MRI for detecting lymphomatous bone marrow involvement is too low to (partially) replace BMB. Sensitivity of whole-body MRI is significantly higher in aggressive lymphoma than in indolent lymphoma and is equal to FDG-PET in both entities.

Key Points

? Bone marrow involvement in lymphoma has prognostic and therapeutic implications. ? Blind bone marrow biopsy (BMB) is standard for bone marrow assessment. ? Neither whole-body MRI nor FDG-PET can yet replace BMB. ? Both techniques have higher sensitivity in aggressive than in indolent lymphoma. ? Both imaging techniques are complementary to BMB.     

Positron-emission tomography CT to identify local recurrence in stage I lung cancer patients 1 year after stereotactic body radiation therapy

Purpose

To evaluate the diagnostic value of positron-emission tomography/computed tomography (PET/CT) in stage I lung cancer patients treated with stereotactic body radiation therapy (SBRT), who have suspicious or unclear local recurrence findings in CT 1 year after treatment.

Patients and methods

A group of 29 patients with unclear or suspicious CT findings 1 year after SBRT were examined with PET/CT. The ability of standard uptake values (SUV_max, SUV_mean and posttherapeutic reduction in SUV) to detect local failure and identify patients at a high risk of disease-specific death was evaluated using logrank statistics. Histology and clinical follow-up were the gold standards for local recurrence.

Results

SUV_mean greater than 3.44 (p?=?0.001); SUV_max greater than 5.48 (p?=?0.009) or a relative reduction in SUV_mean or SUV_max of less than 43 (p?=?0.030) or 52?% (p?=?0.025), respectively, was indicative of local recurrence. These parameters also correlated with an increased risk of disease-specific death: SUV_mean greater than 2.81 (p?=?0.023); SUV_max greater than 3.45 (p?=?0.007) or a relative reduction in SUV_mean or SUV_max of less than 32 (p?=?0.015) or 52?% (p?=?0.013), respectively, was indicative of an increased risk of disease-specific death.

Conclusion

PET/CT performed 1 year after SBRT can reliably identify local recurrence and therefore help to clarify unclear CT findings. As posttherapeutic glucose metabolism also correlates with disease-specific survival, PET/CT may help to stratify lung cancer patients for additional treatment 1 year after SBRT.     

FDG PET/CT for the detection of bone marrow involvement in diffuse large B-cell lymphoma: systematic review and meta-analysis

Purpose

To systematically review and meta-analyse published data on the diagnostic performance of ¹⁸F-FDG PET/CT in detecting bone marrow involvement in patients with newly diagnosed diffuse large B-cell lymphoma (DLBCL).

Methods

PubMed/MEDLINE and Embase were systematically searched for relevant studies. The methodological quality of each study was assessed. Sensitivities and specificities of FDG PET/CT in individual studies were calculated and meta-analysed with a random effects model. A summary receiver operating characteristic curve (sROC) was constructed with the Moses-Shapiro-Littenberg method. Weighted summary proportions of discrepancies between the FDG PET/CT and (blind) bone marrow biopsy (BMB) results among all patients were calculated.

Results

Seven studies, with a total of 654 patients with newly diagnosed DLBCL, were included. Overall, the quality of the included studies was moderate. The sensitivity and specificity of FDG PET/CT for detecting bone marrow involvement ranged from 70.8 % to 95.8 % and from 99.0 % to 100 %, with pooled estimates of 88.7 % (95 % confidence interval, CI, 82.5 – 93.3 %) and 99.8 % (95 % CI 98.8 – 100 %), respectively. The area under the sROC curve was 0.9983. The weighted summary proportion of FDG PET/CT-negative patients with positive BMB findings among all patients was 3.1 % (95 % CI 1.8 – 5.0 %) and the weighted summary proportion of FDG PET/CT-positive patients with negative BMB findings among all patients was 12.5 % (95 % CI 8.4 – 17.3 %).

Conclusion

FDG PET/CT is accurate and complementary to BMB for detecting bone marrow involvement in patients with newly diagnosed DLBCL. A negative FDG PET/CT scan cannot rule out the presence of bone marrow involvement, but positive FDG PET/CT findings obviate the need for BMB for the detection of bone marrow involvement in these patients.     

Amplitude-based optimal respiratory gating in positron emission tomography in patients with primary lung cancer

Objectives

Respiratory motion during PET imaging introduces quantitative and diagnostic inaccuracies, which may result in non-optimal patient management. This study investigated the effects of respiratory gating on image quantification using an amplitude-based optimal respiratory gating (ORG) algorithm.

Methods

Whole body FDG-PET/CT was performed in 66 lung cancer patients. The respiratory signal was obtained using a pressure sensor integrated in an elastic belt placed around the patient’s thorax. ORG images were reconstructed with 50 %, 35 %, and 20 % of acquired PET data (duty cycle). Lesions were grouped into anatomical locations. Differences in lesion volume between ORG and non-gated images, and mean FDG-uptake (SUV_mean) were calculated.

Results

Lesions in the middle and lower lobes demonstrated a significant SUV_mean increase for all duty cycles and volume decrease for duty cycles of 35 % and 20 %. Significant increase in SUV_mean and decrease in volume for lesions in the upper lobes were observed for a 20 % duty cycle. The SUV_mean increase for central lesions was significant for all duty cycles, whereas a significant volume decrease was observed for a duty cycle of 20 %.

Conclusions

This study implies that ORG could influence clinical PET imaging with respect to response monitoring and radiotherapy planning.

Key Points

? Quantifying lesion volume and uptake in PET is important for patient management ? Respiratory motion artefacts introduce inaccuracies in quantification of PET images ? Amplitude-based optimal respiratory gating maintains image quality through selection of duty cycle ? The effect of respiratory gating on lesion quantification depends on anatomical location     

Characterizing bone marrow involvement in Hodgkin’s lymphoma by FDG-PET/CT

Purpose

Fluoro-deoxyglucose positron emmission tomography combined with computed tomography (FDG-PET/CT) is superior to iliac bone marrow biopsy (iBMB) for detection of bone marrow involvement (BMI) in staging of Hodgkin’s lymphoma (HL). The present study aims to characterize the patterns and distribution of BMI in HL as determined by FDG-PET/CT.

Methods

Reports of FDG-PET/CT studies performed for staging of HL were reviewed. BMI was defined as positive iBMB and/or foci of pathological FDG uptake in the skeleton that behaved in concordance with other sites of lymphoma in studies following chemotherapy. Number of FDG uptake foci, their specific location in the skeleton and the presence of corresponding lesions in the CT component of the study, and stage according to the Ann Arbor staging system, were recorded.

Results

The study included 473 patients. iBMB was performed in 336 patients. Nine patients had positive iBMB (9/336, 3 %). Seventy-three patients (73/473, 15 %) had FDG-PET/CT-defined BMI. The BM was the only extranodal site of HL in 52/473 patients (11 %). Forty-five patients had three or more foci of pathological skeletal FDG uptake (45/73, 62 %). Sixty-four patients (64/73, 88 %) had at least one uptake focus in the pelvis or vertebrae. In 60 patients (60/73, 82 %), the number of skeletal FDG uptake foci without corresponding CT lesions was equal to or higher than the number of foci with morphological abnormalities.

Conclusion

FDG-PET/CT demonstrated BMI in 15 % of patients with newly diagnosed HL. Diagnosis of BMI in HL by FDG-PET/CT was more sensitive than iBMB with potential upstage in 11 % of patients. The most common pattern of FDG-PET/CT BMI was multifocal (at least three foci) skeletal FDG uptake, with at least one focus in the pelvis or vertebrae and no corresponding CT lesions.     

Whole body MRI with qualitative and quantitative analysis of DWI for assessment of bone marrow involvement in lymphoma

Aim

Our study aimed to investigate the role of qualitative and quantitative whole body MRI with DWI for assessment of bone marrow involvement (BMI) in newly diagnosed lymphoma using FDG PET–CT and bone marrow biopsy (BMB) as reference standard.

Materials and methods

We retrospectively evaluated 56 patients with newly diagnosed lymphoma (21 Hodgkin’s lymphoma and 35 non-Hodgkin’s lymphoma) who underwent random unilateral BMB, FDG PET–CT and Wb-MRI-DWI for initial staging. In a patient-based analysis, results of Wb-MRI-DWI were compared with FDG PET–CT and BMB. For quantitative analysis, mean ADC values of posterior iliac crest were correlated with BMI and bone marrow cellularity.

Results

WB-MR-DWI obtained excellent concordance with FDG PET–CT both in HL (k = 1.000; 95% CI 1.000–1.000) and in DLBCL (k = 1.000; 95% CI 1.000–1.000). In other NHL, WB-MRI-DWI obtained a good correlation with BMB (k = 0.611; 95% CI 0.295–0.927) while FDG PET–CT had poor concordance (k = 0.067; 95% CI 0.372–0.505). WB-MR-DWI has no false negative errors but 4 false positive results consisting in focal lesions consensually reported by FDG PET–CT and resolved after therapy. No significant correlation between ADC mean value and BMI was found (p = 0.0586).

Conclusion

Our data suggest that Wb-MRI-DWI is a valid technique for BMI assessment in lymphoma patients, thanks to its excellent concordance with FDG PET–CT and good concordance with BMB (superior than FDG PET–CT). If further investigations will confirm our results on larger patient groups, it could become a useful tool in the clinical workup.

     

Preoperative lymph node staging in patients with primary prostate cancer: comparison and correlation of quantitative imaging parameters in diffusion-weighted imaging and 11C-choline PET/CT

Purpose

To compare the diagnostic performance of DWI and 11C-choline PET/CT in the assessment of preoperative lymph node status in patients with primary prostate cancer.

Material and methods

Thirty-three patients underwent DWI and 11C-choline PET/CT prior to prostatectomy and extended pelvic lymph node dissection. Mean standardised uptake value (SUV_mean) and mean apparent diffusion coefficient (ADC) of 76 identified lymph nodes (LN) were measured and correlated with histopathology. ADC values and SUVs were compared using linear regression analysis.

Results

A significant difference between benign and malignant LN was observed for ADC values (1.17 vs. 0.96?×?10^-3 mm²/s; P?<?0.001) and SUV_mean (1.61 vs. 3.20; P?<?0.001). ROC analysis revealed an optimal ADC threshold of 1.01?×?10^-3 mm²/s for differentiating benign from malignant LN with corresponding sensitivity/specificity of 69.70 %/78.57 % and an area under the curve (AUC) of 0.785. The optimal threshold for SUV_mean was 2.5 with corresponding sensitivity/specificity of 69.72 %/90.48 % and with an AUC of 0.832. ADC values and SUV_mean showed a moderate significant inverse correlation (r?=?-0.63).

Conclusion

Both modalities reveal similar moderate diagnostic performance for preoperative lymph node staging of prostate cancer, not justifying their application in routine clinical practice at this time. The only moderate inverse correlation between ADC values and SUV_mean suggests that both imaging parameters might provide complementary information on tumour biology.

Key Points

? Conventional imaging shows low performance for lymph node staging in prostate cancer. ? DWI and 11C-choline PET/CT both provide additional functional information ? Both functional modalities reveal only moderate diagnostic performance.     

Predictive value of pre-therapy 18F-FDG PET/CT for the outcome of 18F-FDG PET-guided radiotherapy in patients with head and neck cancer

Purpose

The aim of this study was to evaluate the predictive role of pre-therapy fluorodeoxyglucose (FDG) uptake parameters of primary tumour in head and neck cancer (HNC) patients undergoing intensity-modulated radiotherapy (IMRT) with simultaneous integrated boost (SIB) on FDG-positive volume—positron emission tomography (PET) gross tumour volume (PET-GTV).

Methods

This retrospective study included 19 patients (15 men and 4 women, mean age 59.2 years, range 23–81 years) diagnosed with HNC between 2005 and 2011. Of 19 patients, 15 (79 %) had stage III–IV. All patients underwent FDG PET/CT before treatment. Metabolic indexes of primary tumour, including metabolic tumour volume (MTV), maximum and mean standardized uptake value (SUV_max, SUV_mean) and total lesion glycolysis (TLG) were considered. Partial volume effect correction (PVC) was performed for SUV_mean and TLG estimation. Correlations between PET/CT parameters and 2-year disease-free survival (DFS), local recurrence-free survival (LRFS) and distant metastasis-free survival (DMFS) were assessed. Median patient follow-up was 19.2 months (range 4–24 months).

Results

MTV, TLG and PVC-TLG predicting patients’ outcome with respect to all the considered local and distant disease control endpoints (LRFS, DMFS and DFS) were 32.4 cc, 469.8 g and 547.3 g, respectively. SUV_mean and PVC-SUV_mean cut-off values predictive of LRFS and DFS were 10.8 and 13.3, respectively. PVC was able to compensate errors up to 25 % in the primary HNC tumour uptake. Moreover, PVC enhanced the statistical significance of the results.

Conclusion

FDG PET/CT uptake parameters are predictors of patients’ outcome and can potentially identify patients with higher risk of treatment failure that could benefit from more aggressive approaches. Application of PVC is recommended for accurate measurement of PET parameters.     

11C-Acetate as a new biomarker for PET/CT in patients with multiple myeloma: initial staging and postinduction response assessment

Purpose

We investigated the potential value of ¹¹C-acetate (ACT) PET/CT in characterizing multiple myeloma (MM) compared with ¹⁸F-FDG PET/CT. Bone marrow histological and whole-body (WB) MRI findings served as the reference standards.

Methods

In this prospective study, 15 untreated MM patients (10 men and 5 women, age range 48?69 years) underwent dual-tracer ¹¹C-ACT and ¹⁸F-FDG PET/CT and WB MRI for pretreatment staging, and 13 of them had repeated examinations after induction therapy. Diffuse and focal bone marrow uptake was assessed by visual and quantitative analyses, including measurement of the maximum standardized uptake value (SUV_max). Between-group differences and correlations were assessed with the Mann-Whitney U test and the Pearson test.

Results

At staging, all 15 patients had diffuse myeloma involvement upon bone marrow examination with 30–90 % of plasma cell infiltrates. Diffuse infiltration was detected in all of them (100 %) using ¹¹C-ACT with a positive correlation between bone marrow uptake values and percentages of plasma cell infiltrates (r = +0.63, p?=?0.01). In contrast, a diagnosis of diffuse infiltration could be established using ¹⁸F-FDG in only six patients (40 %). Focal lesions were shown in 13 patients on both ¹¹C-ACT PET/CT and WB MRI, and in 10 patients on ¹⁸F-FDG PET/CT. Focal lesions demonstrated ¹¹C-ACT uptake with a mean SUV_max of 11.4 ± 3.3 (range 4.6?19.6, n?=?59), which was significantly higher than the ¹⁸F-FDG uptake (mean SUV_max 6.6 ± 3.1, range 2.3?13.7, n?=?29; p?<?0.0001). After treatment, the diffuse bone marrow ¹¹C-ACT uptake showed a mean SUV_max reduction of 66 % in patients with at least a very good partial response versus 34 % in those with at most a partial response only (p?=?0.01).

Conclusion

PET/CT using ¹¹C-ACT as a biomarker showed a higher detection rate for both diffuse and focal myeloma lesions at diagnosis than using ¹⁸F-FDG, and may be valuable for response assessment.     

The value of 18F-FDG PET/CT in the management of malignant peripheral nerve sheath tumors

Purpose

Our objective was to determine how positron emission tomography (PET)/CT had been used in the clinical treatment of malignant peripheral nerve sheath tumor (MPNST) patients at The University of Texas MD Anderson Cancer Center.

Methods

We reviewed a database of MPNST patients referred to MD Anderson Cancer Center during 1995–2011. We enrolled 47 patients who underwent PET/CT imaging. Disease stage was based on conventional imaging and PET/CT findings using National Comprehensive Cancer Network (NCCN) guidelines. Treatment strategies based on PET/CT and conventional imaging were determined by chart review. The maximum and mean standardized uptake values (SUV_max, SUV_mean), metabolic tumor volume (MTV), total lesion glycolysis (TLG), change in SUV_max, change in MTV, and change in TLG were calculated from the PET/CT studies before and after treatment. Response prediction was based on imaging studies performed before and after therapy and categorized as positive or negative for residual tumor. Clinical outcome was determined from chart review.

Results

PET/CT was performed for staging in 16 patients, for restaging in 29 patients, and for surveillance in 2 patients. Of the patients, 88 % were correctly staged with PET/CT, whereas 75 % were correctly staged with conventional imaging. The sensitivity to detect local recurrence and distant metastasis at restaging was 100 and 100 % for PET/CT compared to 86 and 83 % for conventional imaging, respectively. PET/CT findings resulted in treatment changes in 31 % (5/16) and 14 % (4/29) of patients at staging and restaging, respectively. Recurrence, MTV, and TLG were prognostic factors for survival, whereas SUV_max and SUV_mean were not predictive. For 21 patients who had imaging studies performed both before and after treatment, PET/CT was better at predicting outcome (overall survival, progression-free survival) than conventional imaging. A decreasing SUV_max ≥ 30 % and decrease in TLG and MTV were significant predictors for overall and progression-free survival.

Conclusion

PET/CT is valuable in MPNST management because of its high accuracy in staging and high sensitivity and accuracy in restaging as well as improvements in treatment planning. MTV from baseline staging studies is predictive of survival. Additionally, change in SUV_max, TLG, and MTV accurately predicted outcomes after treatment.     

Diagnostic accuracy of 68Ga-DOTANOC PET/CT imaging in pheochromocytoma

Purpose

The purpose of the present study was to evaluate the diagnostic accuracy of ⁶⁸Ga-DOTANOC positron emission tomography (PET)/CT in patients with suspicion of pheochromocytoma.

Methods

Data of 62 patients [age 34.3?±?16.1 years, 14 with multiple endocrine neoplasia type 2 (MEN2)] with clinical/biochemical suspicion of pheochromocytoma and suspicious adrenal lesion on contrast CT (n?=?70), who had undergone ⁶⁸Ga-DOTANOC PET/CT, were retrospectively analyzed. PET/CT images were analyzed visually as well as semiquantitatively, with measurement of maximum standardized uptake value (SUV_max), SUV_mean, SUV_max/SUV_liver, and SUV_mean/SUV_liver. Results of PET/CT were compared with ¹³¹I-metaiodobenzylguanidine (MIBG) imaging, which was available in 40 patients (45 lesions). Histopathology and/or imaging/clinical/biochemical follow-up (minimum 6 months) was used as reference standard.

Results

The sensitivity, specificity, and accuracy of ⁶⁸Ga-DOTANOC PET/CT was 90.4, 85, and 88.7 %, respectively, on patient-based analysis and 92, 85, and 90 %, respectively, on lesion-based analysis. ⁶⁸Ga-DOTANOC PET/CT showed 100 % accuracy in patients with MEN2 syndrome and malignant pheochromocytoma. On direct comparison, lesion-based accuracy of ⁶⁸Ga-DOTANOC PET/CT for pheochromocytoma was significantly higher than ¹³¹I-MIBG imaging (91.1 vs 66.6 %, p?=?0.035). SUV_max was higher for pheochromocytomas than other adrenal lesions (p?=?0.005), MEN2-associated vs sporadic pheochromocytoma (p?=?0.012), but no difference was seen between benign vs malignant pheochromocytoma (p?=?0.269).

Conclusion

⁶⁸Ga-DOTANOC PET/CT shows high diagnostic accuracy in patients with suspicion of pheochromocytoma and is superior to ¹³¹I-MIBG imaging for this purpose. Best results of ⁶⁸Ga-DOTANOC PET/CT are seen in patients with MEN2-associated and malignant pheochromocytoma.     

Differentiation of tumor recurrence from radiation-induced pulmonary fibrosis after stereotactic ablative radiotherapy for lung cancer: characterization of 18F-FDG PET/CT findings

Objective

Stereotactic ablative radiotherapy (SABR), also known as stereotactic body radiotherapy (SBRT), is now a standard treatment option for patients with stage I non-small cell lung cancer or oligometastatic lung tumor who are medically inoperable or medically operable but refuse surgery. When mass-like consolidation is observed on follow-up CT after SABR, it is sometimes difficult to differentiate tumor recurrence from SABR-induced pulmonary fibrosis. In this study, we evaluated the role of ¹⁸F-fluorodeoxyglucose positron emission tomography combined with computed tomography (FDG-PET/CT) in differentiating tumor recurrence from radiation fibrosis after SABR.

Methods

Between June 2006 and June 2009, 130 patients received SABR for stage I non-small cell lung cancer or metastatic lung cancer at our institution. Fifty-nine patients of them were imaged with FDG-PET/CT after SABR. There were a total of 137 FDG-PET/CT scans for retrospective analysis. The FDG uptake in the pulmonary region was assessed qualitatively using a 3-point scale (0, none or faint; 1, mild; or 2, moderate to intense), and the shape (mass-like or non mass-like) was evaluated. For semi-quantitative analysis, the maximum standardized uptake value (SUV_max) was calculated.

Results

Sixteen of 59 patients had local failure. In recurrent tumor, the combination of intensity grade 2 and mass-like shape was most common (21/23; 91 %). By contrast, in cases of radiation fibrosis, the combination of intensity grade 0 or 1 and non mass-like shape was most common (48/59; 81 %). The SUV_max of tumor recurrence after 12 months was significantly higher than that of radiation fibrosis (8.0 ± 3.2 vs. 2.1 ± 0.9, p < 0.001), and all tumor recurrence showed the SUV_max > 4.5 at diagnosis of local failure. At ≥12 months after SABR, these two variables, the combination of intensity 2 and mass-like FDG uptake or SUV_max > 4.5 acquired a significant high predictive value of local recurrence, finding sensitivity 100 % and specificity 100 % for both of them.

Conclusions

The combination of FDG uptake patterns and SUV_max was useful for distinguishing tumor recurrence from radiation fibrosis after SABR.     

Bone metastases from breast cancer: associations between morphologic CT patterns and glycolytic activity on PET and bone scintigraphy as well as explorative search for influential factors

Background

This study aimed to compare the detection of bone metastases from breast cancer on F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) and bone scintigraphy (BS). An explorative search for factors influencing the sensitivity or uptake of BS and FDG-PET was also performed.

Methods

Eighty-eight patients with bone metastases from breast cancer were eligible for this study. Histological confirmation of bone metastases was obtained in 31 patients. The bone metastases were visually classified into four types based on their computed tomography (CT) appearance: osteoblastic, osteolytic, mixed, and negative. The sensitivity of BS and FDG-PET were obtained regarding CT type, adjuvant therapy, and the primary tumor characteristics. The FDG maximum standardized uptake value (SUV_max) was analyzed.

Results

The sensitivities of the three modalities (CT, BS, and FDG-PET) were 77, 89, and 94%, respectively. The sensitivity of FDG-PET for the osteoblastic type (69%) was significantly lower than that for the other types (P < 0.001), and the sensitivity of BS for the negative type (70%) was significantly lower than that for the others. Regarding tumor characteristics, the sensitivity of FDG-PET significantly differed between nuclear grade (NG)1 and NG2–3 (P = 0.032). The SUV_max of the osteoblastic type was significantly lower than that of the other types (P = 0.009). The SUV_max of NG1 was also significantly lower than that of NG2–3 (P = 0.011). No significant difference in FDG uptake (SUV_max) was detected between different histological types.

Conclusion

Although FDG-PET is superior to BS for the detection of bone metastases from breast cancer, this technique has limitations in depicting osteoblastic bone metastases and NG1.

     

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.     

Preoperative PET/CT FDG standardized uptake value of pelvic lymph nodes as a significant prognostic factor in patients with uterine cervical cancer

Purpose

Using integrated PET/CT, we evaluated the prognostic relevance in uterine cervical cancer of preoperative pelvic lymph node (LN) [¹⁸F]FDG uptake.

Methods

Patients with FIGO stage IB to IIA uterine cervical cancer were imaged with FDG PET/CT before radical surgery. We used Cox proportional hazards regression to examine the relationship between recurrence and the FDG maximum standardized uptake value (SUV_max) in the pelvic LN (SUV_LN) on PET/CT.

Results

Clinical data, treatment modalities, and results in 130 eligible patients were reviewed. The median postsurgical follow-up was 34 months (range 6 to 109 months). Receiver operating characteristic analysis identified SUV_LN 2.36 as the most significant cut-off value for predicting recurrence. SUV_LN was correlated with SUV_tumour (P?=?0.002), primary tumour size (P?=?0.004), and parametrial invasion (P?=?0.013). Univariate analyses showed significant associations between recurrence and SUV_LN (P?=?0.001), SUV_tumour (P?=?0.007), pelvic LN metastasis (P?=?0.002), parametrial invasion (P?<?0.001), primary tumour size (P?=?0.007), suspected LN metastasis on MRI (P?=?0.024), and FIGO stage (P?=?0.026). Multivariate analysis identified SUV_LN (P?=?0.013, hazard ratio, HR, 4.447, 95 % confidence interval, CI, 1.379 – 14.343) and parametrial invasion (P?=?0.013, HR 6.728, 95 % CI 1.497 – 30.235) as independent risk factors for recurrence. Patients with SUV_LN ≥2.36 and SUV_LN <2.36 differed significantly in terms of recurrence (HR 15.20, P?<?0.001).

Conclusion

Preoperative pelvic LN FDG uptake showed a strong significant association with uterine cervical cancer recurrence.     

Delayed 18F-fluorodeoxyglucose PET/CT imaging improves quantitation of atherosclerotic plaque inflammation: Results from the CAMONA study

Background

This study aimed to determine if delayed ¹⁸F-fluorodeoxyglucose (¹⁸FDG) PET/CT imaging improves quantitation of atherosclerotic plaque inflammation. Blood-pool activity can disturb the arterial ¹⁸FDG signal. With time, blood-pool activity declines. Therefore, delayed imaging can potentially improve quantitation of vascular inflammation.

Methods and Results

40 subjects were prospectively assessed by dual-time-point PET/CT imaging at approximately 90 and 180 minutes after ¹⁸FDG administration. For both time-points, global uptake of ¹⁸FDG was determined in the carotid arteries and thoracic aorta by calculating the blood-pool corrected maximum standardized uptake value (cSUV_MAX). A target-to-background ratio (TBR) was calculated to determine the contrast resolution at 90 and 180 minutes. Furthermore, we assessed whether the acquisition time-point affected the relation between cSUV_MAX and the estimated 10-year risk for fatal cardiovascular disease (SCORE %). A significant increase in carotid cSUV_MAX (23%, P < .0001), carotid TBR (20%, P < .0001), aortic cSUV_MAX (14%, P < .0001), and aortic TBR (20%, P < .0001) was observed with time. At 90 minutes, cSUV_MAX did not relate to SCORE %, whereas at 180 minutes significant positive relations were observed between SCORE % and carotid (τ = 0.25, P = .045) and aortic (τ = 0.33, P = .008) cSUV_MAX.

Conclusions

Delayed ¹⁸FDG PET/CT imaging at 180 minutes improves quantitation of atherosclerotic plaque inflammation over imaging at 90 minutes. Therefore, the optimal acquisition time-point to assess atherosclerotic plaque inflammation lies beyond the advocated time-point of 90 minutes after ¹⁸FDG administration.     

Delayed sodium 18F-fluoride PET/CT imaging does not improve quantification of vascular calcification metabolism: Results from the CAMONA study

Background

This study aimed to determine if delayed sodium ¹⁸F-fluoride (Na¹⁸F) PET/CT imaging improves quantification of vascular calcification metabolism. Blood-pool activity can disturb the arterial Na¹⁸F signal. With time, blood-pool activity declines. Therefore, delayed imaging can potentially improve quantification of vascular calcification metabolism.

Methods and Results

Twenty healthy volunteers and 18 patients with chest pain were prospectively assessed by triple time-point PET/CT imaging at approximately 45, 90, and 180 minutes after Na¹⁸F administration. For each time point, global uptake of Na¹⁸F was determined in the coronary arteries and thoracic aorta by calculating the blood-pool-corrected maximum standardized uptake value (cSUV_MAX). A target-to-background ratio (TBR) was calculated to determine the contrast resolution at 45, 90, and 180 minutes. Furthermore, we assessed whether the acquisition time-point affected the relation between cSUV_MAX and the estimated 10-year risk for fatal cardiovascular disease (SCORE %). Coronary cSUV_MAX (P = .533) and aortic cSUV_MAX (P = .654) remained similar with time, whereas the coronary TBR (P < .0001) and aortic TBR (P < .0001) significantly increased with time. Even though the contrast resolution improved with time, positive correlations between SCORE % and coronary cSUV_MAX (P < .020) and aortic cSUV_MAX (P < .005) were observed at all investigated time points.

Conclusions

Delayed Na¹⁸F PET/CT imaging does not improve quantification of vascular calcification metabolism. Although contrast resolution improves with time, arterial Na¹⁸F avidity is invariant to the time between Na¹⁸F administration and PET/CT acquisition. Therefore, the optimal PET/CT acquisition time-point to quantify vascular calcification metabolism is achieved as early as 45 minutes after Na¹⁸F administration.     

Interim FDG PET/CT as a prognostic factor in diffuse large B-cell lymphoma

Purpose

Interim ¹⁸F-FDG PET performed early during the course of therapy in diffuse large B-cell lymphoma (DLBCL) is a good predictor of outcome. However, interpretation criteria for interim PET for the evaluation of tumour response are still not clearly defined. The study aim was to assess whether interim PET can predict overall survival (OS) and progression-free survival (PFS) in DLBCL patients following three different sets of parameters, two qualitative (visual) methods and one semiquantitative.

Methods

A total of 50 newly diagnosed DLBCL patients were prospectively enrolled in this study. All patients had a PET/CT scan at diagnosis and an interim PET/CT scan after the second or third cycle of chemotherapy. Three methods of evaluation for the interim PET/CT were used: a qualitative three-point scoring (3-PS) method, a qualitative 5-PS method and a semiquantitative method (ΔSUV_max). The degree of correlation between therapy response seen on FDG PET and PFS and OS was determined.

Results

The analysis of the visual 3-PS method showed no statistically significant difference in PFS and OS. The estimated 5-year PFS and OS were 79 % and 92 %, respectively, in patients with an interim PET scan showing uptake not greater than in the liver versus 50 % in patients with uptake greater than in the liver, and this difference was statistically significant. The optimal cut-off value of ΔSUV_max that could predict the PFS and OS difference in patients with DLBCL was 76 % (95 % CI 62.7–89.2 %) and 75 % (95 % CI, 54.6–95.4 %), respectively.

Conclusion

Our results support the use of liver uptake as an indicator in the qualitative evaluation of interim PET, or a ΔSUV_max greater than 75 % in semiquantitative analysis. Interim PET may predict PFS and OS and could be considered in the prognostic evaluation of DLBCL.     

Comparison of PSMA-HBED and PSMA-I&amp;T as diagnostic agents in prostate carcinoma

Purpose

Gallium(68)-labelled prostate-specific membrane antigen (PSMA) radiopharmaceuticals can be used to detect prostate cancer (PCa) cells due the their over expression of PSMA. The ⁶⁸Ga HBED-PSMA (PSMA-HBED) ligand has been most widely used and can be considered the current gold standard agent. Further PSMA ligands based on the DOTAGA and DOTA conjugates have more recently been developed. These agents (PSMA-I&T and PSMA-617) have potential theranostic capabilities as they can be conjugated with therapeutic radioisotopes. In this study, we examine whether PSMA-I&T has comparative efficacy, such that it could replace PSMA-HBED as a diagnostic agent in prostate carcinoma.

Methods

19 patients with PCa referred for ⁶⁸Ga-PSMA imaging were imaged with PSMA-HBED and PSMA-I&T PET-CT imaging within a 2-week period. The two pharmaceuticals were synthesised using click chemistry. Imaging was performed using the same standardised methodology on a Siemens Biograph mCT. All sites of PSMA binding thought to represent PCa (probable or definite) were included in a lesion analysis that examined lesion concordance and lesional binding efficiency (SUV_peak) between the two radiopharmaceuticals. For each patient, SUV_mean of the LV cavity blood pool, bone, muscle and liver were determined as image background measures.

Results

Across all patients, PSMA uptake was observed in 47 lesions (10 bone lesions, 19 nodal lesions, 18 high-grade intraprostatic binding). Lesions were concordant between the agents in all except for two small (<4 mm) nodal lesions which were not visualised with PSMA-I&T. SUV_peak assessment showed significantly greater overall lesion binding with HBED (paired t test, p = 0.0001). LV blood pool and bone marrow SUV_mean were significantly higher for I&T than HBED (paired t test, blood pool p < 1 × 10–5, bone marrow p < 0.005).

Conclusion

Intra-patient comparative imaging demonstrates higher lesional PSMA-HBED binding than PSMA-I&T and that the HBED agent is likely to have better lesion contrast. While there was concordance in 96% of lesions, 2 small nodal lesions were appreciated with PSMA-HBED imaging while considered normal with PSMA-I&T. These findings suggest that HBED-PSMA has a slightly higher diagnostic accuracy in comparison to PSMA-I&T.