Small (≤3 cm) hepatocellular carcinoma in cirrhosis: the role of double contrast agents in MR imaging vs. multidetector-row CT

Purpose

We prospectively compared gadoliniumenhanced magnetic resonance imaging (dynamic MRI), superparamagnetic iron oxide (SPIO) (ferucarbotran) MRI and multidetector-row computed tomography (MDCT) and the combination of dynamic MRI plus MDCT vs. dynamic MRI plus SPIO-MRI (double-contrast MRI: DC-MRI) forthe detection of small (≤3 cm) hepatocellular carcinomas (HCCs).

Materials and Methods

Sixty-three patients with liver cirrhosis and suspicious nodules detected during ultrasound (US) surveillance underwent DC-MRI in the same imaging session and MDCT within 15 days. The final diagnosis was established at pathology on the explanted liver (n=10), resection (n=6) and biopsy (n=38) specimens or at 2-years’ follow-up (n=9).

Results

One hundred and twenty-three nodules were detected: 87 were confirmed HCCs in 54 patients. The accuracy of SPIO-MRI and dynamic MRI were similar, both being superior to MDCT. Dynamic MRI demonstrated the highest sensitivity (83.9%; p<0.001). especially for lesions <1 cm (90.6%) - coupled with a lower specificity (36.1%) than SPIO-MRI, particularly in subcentimeter lesions (28.6%). SPIO-MRI demonstrated the highest sensitivity for nodules >1 cm and the highest specificity (83.3%) superior to dynamic MRI (p<0.0001). In the per-lesion analysis, SPIO-MRI demonstrated a positive predictive value higher than dynamic MRI (p=0.0059) and than both the combinations dynamic MRI/MDCT and DC-MRI (p=0.0021 and p=0.0087, respectively). DC-MRI showed the highest sensitivity (97.7%) and accuracy (78.9%), detecting hypovascular and atypical HCCs >1 cm. Furthermore its per-patient negative predictive value was the highest (100%), and significantly higher than all the other methods.

Conclusions

DC-MRI is the most sensitive and accurate method and can be confidently used as a single-step procedure for the detection of small HCCs, with the exception of lesions <1 cm.     

Detection of relevant colonic neoplasms with PET/CT: promising accuracy with minimal CT dose and a standardised PET cut-off

Objective:

To determine the performance of FDG-PET/CT in the detection of relevant colorectal neoplasms (adenomas ≥10 mm, with high-grade dysplasia, cancer) in relation to CT dose and contrast administration and to find a PET cut-off.

Methods:

84 patients, who underwent PET/CT and colonoscopy (n?=?79)/sigmoidoscopy (n?=?5) for ${\left( {{\hbox{79}} \times {\hbox{6}} + {\hbox{5}} \times {\hbox{2}}} \right)} = {\hbox{484}}$ colonic segments, were included in a retrospective study. The accuracy of low-dose PET/CT in detecting mass-positive segments was evaluated by ROC analysis by two blinded independent reviewers relative to contrast-enhanced PET/CT. On a per-lesion basis characteristic PET values were tested as cut-offs.

Results:

Low-dose PET/CT and contrast-enhanced PET/CT provide similar accuracies (area under the curve for the average ROC ratings 0.925 vs. 0.929, respectively). PET demonstrated all carcinomas (n?=?23) and 83% (30/36) of relevant adenomas. In all carcinomas and adenomas with high-grade dysplasia (n?=?10) the SUV_max was ≥5. This cut-off resulted in a better per-segment sensitivity and negative predictive value (NPV) than the average PET/CT reviews (sensitivity: 89% vs. 82%; NPV: 99% vs. 98%). All other tested cut-offs were inferior to the SUV_max.

Conclusion:

FDG-PET/CT provides promising accuracy for colorectal mass detection. Low dose and lack of iodine contrast in the CT component do not impact the accuracy. The PET cut-off SUV_max?≥?5 improves the accuracy.     

Impact of Ga-68 DOTATOC PET/CT on the diagnosis and treatment of patients with multiple endocrine neoplasia

Purpose

To evaluate the impact of Ga-68 DOTATOC PET/CT on diagnosis and therapeutic management of patients with multiple endocrine neoplasia (MEN).

Materials and methods

We did 28 Ga-68 DOTATOC PET/CT in 21 MEN patients (10 female, 11 men; mean age 41.3?years). 109 lesions detected were classified into MEN-associated lesions [i.e., neuroendocrine tumors (NET)] and non-MEN-associated lesions for PET, CT, and PET/CT. The impact of Ga-68 DOTATOC PET/CT on diagnosis and therapeutic management of patients with MEN were assessed by the records of the interdisciplinary NET tumor board including histopathological findings, clinical and radiological follow-up.

Results

Ga-68 DOTATOC PET/CT had an impact on diagnosis and therapeutic management in 10/21 (47.6?%) MEN patients. For detecting NET lesions in MEN patients Ga-68 DOTATOC PET/CT reached a sensitivity/specificity of 91.7?%/93.5?%. There was a significant difference for the detection rate between Ga-68 DOTATOC PET/CT and CT alone (p?<?0.001) both using contrast-agent (p?=?0.002) or not (p?<?0.001) and also a significant difference between contrast-enhanced (CE-) CT and non-CE-CT alone (p?=?0.006).

Conclusions

GA-68 DOTATOC PET/CT allows a high detection rate of NET lesions in the context of MEN-1 syndrome as well as influence therapeutic management in nearly up to half of the patients. GA-68 DOTATOC PET/CT should include a CE-CT to improve MEN-associated NET lesion detection.     

Additional value of integrated PET/CT over PET alone in the initial staging and follow up of head and neck malignancy

Objective

Clinical application of FDG-PET in head and neck cancer includes identification of metastases, unknown primary head and neck malignancy, or second primary carcinoma, and also recurrent tumor after treatment. In this study, the additional value of PET/CT fusion images over PET images alone was evaluated in patients with initial staging and follow up of head and neck malignancy.

Methods

Forty patients with suspected primary head and neck malignancy and 129 patients with suspected relapse after treatment of head and neck malignancy were included. FDG-PET/CT study was performed after the intravenous administration of FDG (5 MBq/kg). Target of evaluation was set at primary tumor, cervical lymph node, and whole body. PET images and PET with CT fusion images were compared. Sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) were calculated. Results of PET and PET/CT were compared with postoperative histopathological examination, and case by case comparison of PET and PET/CT results for each region was performed. The additional value of CT images over PET only images was assessed. Statistical differences in sensitivity and specificity were evaluated.

Results

In the comparative evaluation of 507 targets by PET alone and PET/CT, 401 targets showed agreement of the results. Of the 106 discordant targets, 103 showed a positive result on PET alone and negative result on PET/CT. These results showed a significant difference (p < 0.01). Sensitivity of PET/CT was slightly higher than that of PET without statistical significance, while specificity of PET/CT was significantly higher than that of PET alone (Initial staging: 90.5% vs. 62.2%, p < 0.01; Follow up: 97.2% vs. 74.4%, p < 0.01). In Fisher’s direct probability test, a significant difference was noted in the sensitivity (Initial staging: 91.3% vs. 87.0%, p < 0.01; Follow up: 93.9% vs. 91.4%, p < 0.01).

Conclusions

Combined PET/CT showed improved diagnostic performance than PET alone by decreasing the number of false positive findings in patients with initial staging and follow up of head and neck malignancy.     

Whole-body [18F]FDG PET/MRI vs. PET/CT in the assessment of bone lesions in oncological patients: initial results

Objectives

To compare [¹⁸?F]FDG PET/MRI with PET/CT for the assessment of bone lesions in oncologic patients.

Methods

This prospective study included 67 patients with solid tumours scheduled for PET/CT with [¹⁸?F]FDG who also underwent a whole-body PET/MRI scan. The datasets (PET/CT, PET/MRI) were rated by two readers regarding lesion conspicuity (four-point scale) and diagnostic confidence (five-point scale). Median scores were compared using the Wilcoxon test.

Results

Bone metastases were present in ten patients (15 %), and benign bone lesions in 15 patients (22 %). Bone metastases were predominantly localized in the pelvis (18 lesions, 38 %) and the spine (14 lesions, 29 %). Benign bone lesions were exclusively osteosclerotic and smaller than the metastases (mean size 6 mm vs. 23 mm). While PET/CT allowed identification of 45 of 48 bone metastases (94 %), PET/MRI allowed identification of all bone metastases (100 %). Conspicuity of metastases was high for both modalities with significantly better results using PET/MRI (p?<?0.05). Diagnostic confidence in lesion detection was high for both modalities without a significant difference. In benign lesions, conspicuity and diagnostic confidence were significantly higher with PET/CT (p?<?0.05).

Conclusions

[¹⁸?F]FDG PET/MRI shows high potential for the assessment of bone metastases by offering superior lesion conspicuity when compared to PET/CT. In hypersclerotic, benign bone lesions PET/CT still sets the reference.

Key Points

? PET/MRI and PET/CT are of equal value for the identification of disease-positive patients ? PET/MRI offers higher lesion conspicuity as well as diagnostic confidence ? PET/MRI is an attractive new alternative for the assessment of bone metastases     

Functional imaging in phaeochromocytoma and neuroblastoma with 68Ga-DOTA-Tyr 3-octreotide positron emission tomography and 123I-metaiodobenzylguanidine

Purpose

⁶⁸Ga-DOTA-Tyr³-octreotide positron emission tomography (⁶⁸Ga-DOTA-TOC PET) has proven to be superior to ¹¹¹In-DTPA-D-Phe¹-octreotide (¹¹¹In-octreotide) planar scintigraphy and SPECT imaging in neuroendocrine tumours (NETs). Because of these promising results, we compared the accuracy of ¹²³I-metaiodobenzylguanidine (¹²³I-MIBG) imaging with PET in the diagnosis and staging of metastatic phaeochromocytoma and neuroblastoma, referring to radiological imaging as reference standard.

Methods

Three male and eight female patients (age range 3 to 68?years) with biochemically and histologically proven disease were included in this study. Three male and three female patients were suffering from phaeochromocytoma, and five female patients from neuroblastoma. Comparative evaluation included morphological imaging with CT or MRI, functional imaging with ⁶⁸Ga-DOTA-TOC?PET and ¹²³I-MIBG imaging. Imaging results were analysed on a per-patient and on a per-lesion basis.

Results

On a per-patient basis, both ⁶⁸Ga-DOTA-TOC and ¹²³I-MIBG showed a sensitivity of 100%, when compared with anatomical imaging. In phaeochromocytoma patients, on a per-lesion basis, the sensitivity of ⁶⁸Ga-DOTA-TOC was 91.7% and that of ¹²³I-MIBG was 63.3%. In neuroblastoma patients, on a per-lesion basis, the sensitivity of ⁶⁸Ga-DOTA-TOC was 97.2% and that of ¹²³I-MIBG was 90.7%. Overall, in this patient cohort, ⁶⁸Ga-DOTA-TOC PET identified 257 lesions, anatomical imaging identified 216 lesions, and ¹²³I-MIBG identified only 184 lesions. In this patient group, the overall sensitivity of ⁶⁸Ga-DOTA-TOC PET on a lesion basis was 94.4% (McNemar p<0.0001) and that of ¹²³I-MIBG was 76.9% (McNemar p<0.0001).

Conclusion

Our analysis in this relatively small patient cohort indicates that ⁶⁸Ga-DOTA-TOC PET may be superior to ¹²³I-MIBG gamma-scintigraphy and even to the reference CT/MRI technique in providing particularly valuable information for pretherapeutic staging of phaeochromocytoma and neuroblastoma.     

CT- versus coregistered FDG-PET/CT-based radiation therapy plans for conformal radiotherapy in colorectal liver metastases: a dosimetric comparison

Purpose

Our aim was to compare computed tomography (CT) and coregistered [¹⁸F]-fluorodeoxyglucose positron emission tomography CT-(FDG-PET/CT) based delineation of gross tumor volume (GTV) in unresectable colorectal liver metastasis (CRLM).

Materials and methods

Fifty-four patients with unresectable CRLM were enrolled but 16 were excluded due to detection of additional hepatic metastases in ten on PET/CT scans, precluding radiotherapy because of transcendent critical organ doses beyond tolerable limits; and of extrahepatic metastases in six. For 38 eligible patients, both CT and PET/CT images were acquired, and two 3D conformal plans were made using the CT and FDG-PET/CT fusion data sets. Radiotherapy plans (RTP) and doses to critical organs were analyzed.

Results

Comparisons between two RTPs revealed need for change in GTV in 31 of 38 analyzable patients (81.6?%). In 25 (65.8?%) patients, GTV was significantly increased, with a median of 33.2?% (p?<?0.001), whereas median 12.8?% decrease in six (15.8?%) (p?<?0.001). There were no clinically meaningful differences in critical organ doses.

Conclusion

Coregistered FDG-PET/CT may improve delineation of GTV and theoretically reduce the likelihood of geographic misses in unresectable CRLM. Additionally, integration of FDG-PET/CT in the initial assessments of CRLM may spare almost one third of patients from potentially futile radical interventions.     

Combined use of 18F-FDG PET/CT and MRI for response monitoring of breast cancer during neoadjuvant chemotherapy

Purpose

To explore the potential complementary value of PET/CT and dynamic contrast-enhanced MRI in predicting pathological response to neoadjuvant chemotherapy (NAC) of breast cancer and the dependency on breast cancer subtype.

Methods

We performed ¹⁸F-FDG PET/CT and MRI examinations before and during NAC. The imaging features evaluated on both examinations included baseline and changes in ¹⁸F-FDG maximum standardized uptake value (SUVmax) on PET/CT, and tumour morphology and contrast uptake kinetics on MRI. The outcome measure was a (near) pathological complete response ((near-)pCR) after surgery. Receiver operating characteristic curves with area under the curve (AUC) were used to evaluate the relationships between patient, tumour and imaging characteristics and tumour responses.

Results

Of 93 patients, 43 achieved a (near-)pCR. The responses varied among the different breast cancer subtypes. On univariate analysis the following variables were significantly associated with (near-)pCR: age (p?=?0.033), breast cancer subtype (p?<?0.001), relative change in SUVmax on PET/CT (p?<?0.001) and relative change in largest tumour diameter on MRI (p?<?0.001). The AUC for the relative reduction in SUVmax on PET/CT was 0.78 (95 % CI 0.68–0.88), and for the relative reduction in tumour diameter at late enhancement on MRI was 0.79 (95 % CI 0.70–0.89). The AUC increased to 0.90 (95 % CI 0.83–0.96) in the final multivariate model with PET/CT, MRI and breast cancer subtype combined (p?=?0.012).

Conclusion

PET/CT and MRI showed comparable value for monitoring response during NAC. Combined use of PET/CT and MRI had complementary potential. Research with more patients is required to further elucidate the dependency on breast cancer subtype.     

Detection of underlying malignancy in patients with paraneoplastic neurological syndromes: comparison of 18F-FDG PET/CT and contrast-enhanced CT

Purpose

To determine the value of combined ¹⁸F-FDG PET/CT with diagnostic contrast-enhanced CT (CECT) in detecting primary malignancies and metastases in patients with paraneoplastic neurological syndromes (PNS) and to compare this with CECT alone.

Methods

PET/CT scans from 66 patients with PNS were retrospectively evaluated. Two blinded readers initially reviewed the CECT portion of each PET/CT scan. In a second session 3 months later, the readers analysed the combined PET/CT scans. Findings on each study were assessed using a four-point-scale (1 normal/benign; 2 inconclusive, further diagnostic work-up may be necessary; 3 malignant; 4 inflammatory). Sensitivity and specificity for malignant findings were calculated for PET/CT and CECT. Interreader agreement was determined by calculating Cohen’s kappa. Pooled data from clinical follow-up (including histopathology and follow-up imaging, median follow-up 20.0 months) served as the reference gold standard.

Results

Both readers classified 12 findings in ten patients (15 %) as malignant on the PET/CT scans (two patients had two primary tumours). One such imaging finding (suspected thymic cancer) was false-positive (i.e. benign histology). The most common tumours were bronchial carcinoma (n?=?3), lymph node metastases of gynaecological tumours (n?=?3) and tonsillar carcinoma (n?=?2). Three of 12 findings (25 %) were not detected by CECT alone (cervical carcinoma, lymph node metastasis and tonsillar carcinoma). In a per-patient analysis, sensitivity and specificity for malignant findings were 100 % and 90 % for PET/CT and 78 % and 88 % for CECT. In 24 % (reader 1) and 21 % (reader 2) of the patients, the PET/CT findings were inconclusive. Of these findings, 57 % (reader 1) and 56 % (reader 2) were only diagnosed with PET (e.g. focal FDG uptake of the thyroid, gastrointestinal tract and ovaries). On follow-up, none of these findings corresponded to malignancy. Overall agreement between the two readers was excellent with a Cohen’s kappa of 0.95?±?0.04 (p?<?0.001) for PET/CT and 0.97?±?0.03 (p?<?0.001) for CECT alone.

Conclusion

In this cohort of patients with PNS, PET/CT exhibited improved detection of underlying malignancy versus CECT alone. While hybrid imaging produces a greater number of inconclusive findings, sensitivity is increased for the detection of head and neck and gynaecological malignancies as well as metastatic lymph node involvement.     

A retrospective comparison between 68Ga-DOTA-TOC PET/CT and 18F-DOPA PET/CT in patients with extra-adrenal paraganglioma

Purpose

¹⁸F-Fluoro-l-dihydroxyphenylalanine (¹⁸F-DOPA) PET offers high sensitivity and specificity in the imaging of nonmetastatic extra-adrenal paragangliomas (PGL) but lower sensitivity in metastatic or multifocal disease. These tumours are of neuroendocrine origin and can be detected by ⁶⁸Ga-DOTA-Tyr³-octreotide (⁶⁸Ga-DOTA-TOC) PET. Therefore, we compared ⁶⁸Ga-DOTA-TOC and ¹⁸F-DOPA as radiolabels for PET/CT imaging for the diagnosis and staging of extra-adrenal PGL. Combined cross-sectional imaging was the reference standard.

Methods

A total of 5 men and 15 women (age range 22 to 73 years) with anatomical and/or histologically proven extra-adrenal PGL were included in this study. Of these patients, 5 had metastatic or multifocal lesions and 15 had single sites of disease. Comparative evaluation included morphological imaging with CT and functional imaging with ⁶⁸Ga-DOTA-TOC PET and ¹⁸F-DOPA PET. The imaging results were analysed on a per-patient and a per-lesion basis. The maximum standardized uptake value (SUV_max) of each functional imaging modality in concordant tumour lesions was measured.

Results

Compared with anatomical imaging, ⁶⁸Ga-DOTA-TOC PET and ¹⁸F-DOPA PET each had a per-patient and per-lesion detection rate of 100 % in nonmetastatic extra-adrenal PGL. However, in metastatic or multifocal disease, the per-lesion detection rate of ⁶⁸Ga-DOTA-TOC was 100 % and that of ¹⁸F-DOPA PET was 56.0 %. Overall, ⁶⁸Ga-DOTA-TOC PET identified 45 lesions; anatomical imaging identified 43 lesions, and ¹⁸F-DOPA PET identified 32 lesions. The overall per-lesion detection rate of ⁶⁸Ga-DOTA-TOC PET was 100 % (McNemar, P?<?0.5), and that of ¹⁸F-DOPA PET was 71.1 % (McNemar, P?<?0.001). The SUV_max (mean ± SD) of all 32 concordant lesions was 67.9?±?61.5 for ⁶⁸Ga-DOTA-TOC PET and 11.8?±?7.9 for ¹⁸F-DOPA PET (Mann-Whitney U test, P?<?0.0001).

Conclusion

⁶⁸Ga-DOTA-TOC PET may be superior to ¹⁸F-DOPA PET and diagnostic CT in providing valuable information for pretherapeutic staging of extra-adrenal PGL, particularly in surgically inoperable tumours and metastatic or multifocal disease.     

Assessment of pulmonary melanoma metastases with 18F-FDG PET/CT: which PET-negative patients require additional tests for definitive staging?

Objectives

To determine, in patients with melanoma, the dependence of PET sensitivity on pulmonary metastasis size, and to determine patients who require further evaluation for definite staging.

Methods

Of 183 melanoma patients who underwent ¹⁸F-fluorodeoxyglucose PET/computed tomography (CT) for staging or follow-up between January 2008 and June 2011, 38 patients (18 women and 20 men; mean age 62.0?±?14.7?years) with one or more pulmonary metastases visible on CT were included in the retrospective study. Each pulmonary metastasis was rated as positive or negative on PET, and lesion size (maximum transverse diameter) was assessed on CT. PET sensitivity was calculated according to the lesions’ size, in 2-mm steps.

Results

A total of 181 pulmonary metastases were analysed. PET sensitivity was 7.9?% for lesions of 4–5?mm; 33.3?% for lesions of 6–7?mm; 56.8?% for lesions of 8–9?mm; 63.6?% for lesions of 10–11?mm; 100?% for lesions of 12–14?mm; and 100?% for lesions of at least 15?mm. The differences in sensitivity between the size groups were significant (P?<?0.001)

Conclusions

With current state-of-the-art PET/CT technology, additional tests are necessary for definitive staging of melanoma patients who have one or more PET-negative lung nodules less than 12?mm in diameter on expiratory CT.

Key Points

? PET cannot rule out malignancy in pulmonary nodules less than 12?mm on expiratory CT. ? Melanoma patients with PET-negative pulmonary nodules less than 12?mm require additional tests. ? Knowledge of these factors can help interpretation of PET and PET/CT findings.     

Detection and quantification of focal uptake in head and neck tumours: 18F-FDG PET/MR versus PET/CT

Purpose

Our objectives were to assess the quality of PET images and coregistered anatomic images obtained with PET/MR, to evaluate the detection of focal uptake and SUV, and to compare these findings with those of PET/CT in patients with head and neck tumours.

Methods

The study group comprised 32 consecutive patients with malignant head and neck tumours who underwent whole-body ¹⁸F-FDG PET/MR and PET/CT. PET images were reconstructed using the attenuation correction sequence for PET/MR and CT for PET/CT. Two experienced observers evaluated the anonymized data. They evaluated image and fusion quality, lesion conspicuity, anatomic location, number and size of categorized (benign versus assumed malignant) lesions with focal uptake. Region of interest (ROI) analysis was performed to determine SUVs of lesions and organs for both modalities. Statistical analysis considered data clustering due to multiple lesions per patient.

Results

PET/MR coregistration and image fusion was feasible in all patients. The analysis included 66 malignant lesions (tumours, metastatic lymph nodes and distant metastases), 136 benign lesions and 470 organ ROIs. There was no statistically significant difference between PET/MR and PET/CT regarding rating scores for image quality, fusion quality, lesion conspicuity or anatomic location, number of detected lesions and number of patients with and without malignant lesions. A high correlation was observed for SUV_mean and SUV_max measured on PET/MR and PET/CT for malignant lesions, benign lesions and organs (ρ?=?0.787 to 0.877, p?<?0.001). SUV_mean and SUV_max measured on PET/MR were significantly lower than on PET/CT for malignant tumours, metastatic neck nodes, benign lesions, bone marrow, and liver (p?<?0.05). The main factor affecting the difference between SUVs in malignant lesions was tumour size (p?<?0.01).

Conclusion

In patients with head and neck tumours, PET/MR showed equivalent performance to PET/CT in terms of qualitative results. Comparison of SUVs revealed an excellent correlation for measurements on both modalities, but underestimation of SUVs measured on PET/MR as compared to PET/CT.     

Imaging quality of F-18-FDG PET/CT in the inpatient versus outpatient setting

Objective

The purpose of this study is to investigate potential differences in the image quality of inpatient versus outpatient F-18-FDG PET/CT to provide evidence for appropriate policies and procedures to be promulgated on inpatient referrals.

Methods

100 consecutive inpatient and 100 outpatient F-18-FDG PET/CT scans were compared from the same time period and PET/CT scanner. Each study was evaluated for a subjective overall rating (optimal vs. suboptimal), and also by objective measurements (SUVmean) in four background structures (brain, blood pool, liver, and muscle).

Results

96 outpatient scans were rated optimal and 4 suboptimal whereas corresponding numbers for inpatient scans were 77 and 23 (p < 0.001). Of the objective indices, cerebellar SUV was significantly different in inpatient versus outpatient (5.3 vs. 6.9; p < 0.001) as well as suboptimal versus optimal rated groups (4.8 vs. 6.3; p < 0.001). While mean blood glucose was higher for inpatients (108.01 vs. 101.49 mg/dl; p = 0.017), it was not significantly different between optimal and suboptimal exams. Linear regression analysis between blood glucose levels and cerebellar uptake revealed an inverse relationship (R = ?0.38, p < 0.001).

Conclusions

There was a significantly higher number of inpatient PET/CT scans rated as suboptimal in comparison to outpatient scans. Decreased cerebellar uptake was present in suboptimal rated studies and in inpatient studies. Altered biodistribution is thus a potential etiology of reduced scan quality among inpatients. These findings, if duplicated among other readers and centers, may form the basis of quality control recommendations for inpatient PET/CT ordering patterns.     

Extent of disease in recurrent prostate cancer determined by [<Superscript>68</Superscript>Ga]PSMA-HBED-CC PET/CT in relation to PSA levels,PSA doubling time and Gleason score

Purpose

To examine the relationship between the extent of disease determined by [⁶⁸Ga]PSMA-HBED-CC-PET/CT and the important clinical measures prostate-specific antigen (PSA), PSA doubling time (PSAdt) and Gleason score.

Methods

We retrospectively studied the first 155 patients with recurrent prostate cancer (PCA) referred to our university hospital for [⁶⁸Ga]PSMA-HBED-CC PET/CT.

Results

PET/CT was positive in 44 %, 79 % and 89 % of patients with PSA levels of ≤1, 1 – 2 and ≥2 ng/ml, respectively. Patients with high PSA levels showed higher rates of local prostate tumours (p?<?0.001), and extrapelvic lymph node (p?=?0.037) and bone metastases (p?=?0.013). A shorter PSAdt was significantly associated with pelvic lymph node (p?=?0.026), extrapelvic lymph node (p?=?0.001), bone (p?<?0.001) and visceral (p?=?0.041) metastases. A high Gleason score was associated with more frequent pelvic lymph node metastases (p?=?0.039). In multivariate analysis, both PSA and PSAdt were independent determinants of scan positivity and of extrapelvic lymph node metastases. PSAdt was the only independent marker of bone metastases (p?=?0.001). Of 20 patients with a PSAdt <6 months and a PSA ≥2 ng/ml, 19 (95 %) had a positive scan and 12 (60 %) had M1a disease. Of 14 patients with PSA <1 ng/ml and PSAdt >6 months, only 5 (36 %) had a positive scan and 1 (7 %) had M1a disease.

Conclusion

[⁶⁸Ga]PSMA-HBED-CC PET/CT will identify PCA lesions even in patients with very low PSA levels. Higher PSA levels and shorter PSAdt are independently associated with scan positivity and extrapelvic metastases, and can be used for patient selection for [⁶⁸Ga]PSMA-HBED-CC PET/CT.

     

Compared to <Superscript>123</Superscript>I-MIBG SPECT/CT, <Superscript>18</Superscript>F-DOPA PET/CT provides accurate tumor extent in patients with extra-adrenal paraganglioma

Aim

The aim of this study was to compare the accuracy of ¹²³I-MIBG SPECT/CT with that of ¹⁸F-DOPA PET/CT for staging extra-adrenal paragangliomas (PGLs) using both functional and anatomical images (i.e., combined cross-sectional imaging) as the reference standards.

Methods

Three men and seven women (age range 26–73 years) with anatomical and/or histologically proven disease were included in this study. Three patients had either metastatic head-and-neck paragangliomas (HNPGLs) or multifocal PGL, and seven patients had nonmetastatic disease. Comparative evaluation included morphological imaging with CT, functional imaging with ¹⁸F-DOPA PET, and ¹²³I-MIBG imaging including SPECT/CT. Imaging results were analyzed on a per-patient and per-lesion basis.

Results

On a per-patient basis, ¹⁸F-DOPA PET’s detection rate for both nonmetastatic and metastatic/multifocal disease was 100%, whereas that of planar ¹²³I-MIBG imaging alone was 10.0% and that of ¹²³I-MIBG SPECT/CT was 20.0%. Overall, on a per-lesion basis, ¹⁸F-DOPA PET showed a sensitivity of 69.2% (McNemar p?<?0.001) compared with anatomical imaging. Sensitivity of planar ¹²³I-MIBG scintigraphy was 5.6%, and that of SPECT/CT was 11.1% (McNemar p?<?0.0001). Overall, ¹⁸F-DOPA PET identified 18 lesions, and anatomical imaging identified 26 lesions; planar ¹²³IMIBG imaging identified only 1 lesion, and SPECT/CT, 2 lesions.

Conclusion

¹⁸F-DOPA PET is more sensitive than is ¹²³I-MIBG imaging, including SPECT/CT, for staging HNPGL. Combined functional and anatomical imaging (PET/CT) is indicated to exclude metastatic disease in extra-adrenal PGL.

     

Comparison of 131I whole-body imaging, 131I SPECT/CT, and 18F-FDG PET/CT in the detection of metastatic thyroid cancer

Purpose

The aim of this study was to compare ¹³¹I whole-body scintigraphy (WBS), WBS with ¹³¹I single photon emission computed tomography/computed tomography (SPECT/CT), and ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT in the detection of distant metastases of differentiated thyroid cancer (DTC).

Methods

A total of 140 patients with 258 foci of suspected distant metastases were evaluated. ¹³¹I WBS, ¹³¹I SPECT/CT, and ¹⁸F-FDG PET/CT images were interpreted separately. The final diagnosis was obtained from histopathologic study, serum thyroglobulin level, other imaging modalities, and/or clinical follow-up.

Results

Of the 140 patients with 258 foci, 46 patients with 166 foci were diagnosed as positive for distant metastasis. The sensitivity, specificity, and diagnostic accuracy of each imaging modality were 65, 55, and 59%, respectively, for ¹³¹I WBS; 65, 95, and 85% for ¹³¹I SPECT/CT, respectively; and 61, 98, and 86%, respectively, for ¹⁸F-FDG PET/CT in patient-based analyses. Lesion-based analyses demonstrated that both SPECT/CT and PET/CT were superior to WBS (p<0.001) in all patient groups. SPECT/CT was superior to WBS and PET/CT (p<0.001) in patients who received a single challenge of radioiodine therapy, whereas PET/CT was superior to WBS (p=0.005) and SPECT/CT (p=0.013) in patients who received multiple challenges.

Conclusion

Both SPECT/CT and PET/CT demonstrated high diagnostic performance in detecting metastatic thyroid cancer. SPECT/CT was highly accurate in patients who underwent a single challenge of radioiodine therapy. In contrast, ¹⁸F-FDG PET/CT presented the highest diagnostic performance in patients who underwent multiple challenges of radioiodine therapy.     

Breast cancer detection using high-resolution breast PET compared to whole-body PET or PET/CT

Purpose

To compare the performance characteristics of positron emission mammography (PEM) with those of whole-body PET (WBPET) and PET/CT in women with newly diagnosed breast cancer.

Methods

A total of 178 women consented to PEM for presurgical planning in an IRB-approved protocol and also underwent either WBPET (n?=?69) or PET/CT (n?=?109) imaging, as per usual care at three centers. Tumor detection sensitivity, positive predictive values, and ¹⁸F-fluorodeoxyglucose (FDG) uptake were compared between the modalities. The effects of tumor size, type, and grade on detection were examined. The chi-squared or Fisher’s exact tests were used to compare distributions between groups, and McNemar’s test was used to compare distributions for paired data within subject groups, i.e. PEM versus WBPET or PEM versus PET/CT.

Results

The mean age of the women was 59?±?12 years (median 60 years, range 26–89 years), with a mean invasive index tumor size of 1.6?±?0.8 cm (median 1.5 cm, range 0.5–4.0 cm). PEM detected more index tumors (61/66, 92 %) than WBPET (37/66, 56 %; p?<?0.001) or PET/CT (95/109, 87 % vs. 104/109, 95 % for PEM; p?<?0.029). Sensitivity for the detection of additional ipsilateral malignancies was also greater with PEM (7/15, 47 %) than with WBPET (1/15, 6.7 %; p?=?0.014) or PET/CT (3/23, 13 % vs. 13/23, 57 % for PEM; p?=?0.003). Index tumor detection decreased with decreasing invasive tumor size for both WBPET (p?=?0.002) and PET/CT (p?<?0.001); PEM was not significantly affected (p?=?0.20). FDG uptake, quantified in terms of maximum PEM uptake value, was lowest in ductal carcinoma in situ (median 1.5, range 0.7–3.0) and invasive lobular carcinoma (median 1.5, range 0.7–3.4), and highest in grade III invasive ductal carcinoma (median 3.1, range 1.4–12.9).

Conclusion

PEM was more sensitive than either WBPET or PET/CT in showing index and additional ipsilateral breast tumors and remained highly sensitive for tumors smaller than 1 cm.     

Evaluation of the PET component of simultaneous [18F]choline PET/MRI in prostate cancer: comparison with [18F]choline PET/CT

Purpose

The aim of this study was to evaluate the positron emission tomography (PET) component of [¹⁸F]choline PET/MRI and compare it with the PET component of [¹⁸F]choline PET/CT in patients with histologically proven prostate cancer and suspected recurrent prostate cancer.

Methods

Thirty-six patients were examined with simultaneous [¹⁸F]choline PET/MRI following combined [¹⁸F]choline PET/CT. Fifty-eight PET-positive lesions in PET/CT and PET/MRI were evaluated by measuring the maximum and mean standardized uptake values (SUV_max and SUV_mean) using volume of interest (VOI) analysis. A scoring system was applied to determine the quality of the PET images of both PET/CT and PET/MRI. Agreement between PET/CT and PET/MRI regarding SUV_max and SUV_mean was tested using Pearson’s product-moment correlation and Bland-Altman analysis.

Results

All PET-positive lesions that were visible on PET/CT were also detectable on PET/MRI. The quality of the PET images was comparable in both groups. Median SUV_max and SUV_mean of all lesions were significantly lower in PET/MRI than in PET/CT (5.2 vs 6.1, p?<?0.05 and 2.0 vs 2.6, p?<?0.001, respectively). Pearson’s product-moment correlation indicated highly significant correlations between SUV_max of PET/CT and PET/MRI (R?=?0.86, p?<?0.001) as well as between SUV_mean of PET/CT and PET/MRI (R?=?0.81, p?<?0.001). Bland-Altman analysis revealed lower and upper limits of agreement of ?2.77 to 3.64 between SUV_max of PET/CT vs PET/MRI and ?1.12 to +2.23 between SUV_mean of PET/CT vs PET/MRI.

Conclusion

PET image quality of PET/MRI was comparable to that of PET/CT. A highly significant correlation between SUV_max and SUV_mean was found. Both SUV_max and SUV_mean were significantly lower in [¹⁸F]choline PET/MRI than in [¹⁸F]choline PET/CT. Differences of SUV_max and SUV_mean might be caused by different techniques of attenuation correction. Furthermore, differences in biodistribution and biokinetics of [¹⁸F]choline between the subsequent examinations and in the respective organ systems have to be taken into account.     

Early response of patients undergoing concurrent chemoradiotherapy for cervical cancer: a comparison of PET/CT and MRI

Objective

To investigate the efficacy of positron emission tomography/computed tomography (PET/CT) and magnetic resonance imaging (MRI) for early response evaluation of cervical cancer patients undergoing concurrent chemoradiotherapy (CCRT).

Methods

Fifty-two patients were prospectively enrolled in the study. The pathologic findings were squamous cell carcinoma in 47 patients and adenocarcinoma in 5 patients. All patients underwent PET/CT and MRI scans before, during and within 1 month after completion of CCRT. The percent change in tumor volume during and after CCRT based on PET/CT and MRI images was compared.

Results

There were significant differences (p < 0.001) between the initial tumor volume and tumor volume during and after CCRT as measured by both PET/CT and MRI. During CCRT, the percent volume reduction based on PET/CT images was significantly greater than the percent volume reduction calculated from MRI images (p = 0.024). However, after the completion of CCRT, no significant differences were found in volume reduction as calculated based on PET/CT versus MRI images (p = 0.289). The percent volume reduction of adenocarcinomas was significantly smaller than that of squamous cell carcinomas based on both PET/CT (p = 0.041) and MRI images (p < 0.001).

Conclusions

Significant decreases in tumor volume were observed during and after CCRT in patients with cervical cancer. Tumor volume reduction on PET/CT images was greater than that on MRI images during CCRT. We suggest that early PET/CT as well as MRI scans could be taken during CCRT to evaluate tumor response and allow personalized treatment of cervical cancer.     

Dual-time-point [18F]-FDG PET/CT in the diagnostic evaluation of suspicious breast lesions

Purpose

The authors sought to evaluate whether the reacquisition of images 3 h after administration of radiotracer improves the sensitivity of fluorine-18 fluorodeoxyglucose positron emission tomography computed tomography ([¹⁸F]-FDG PET/CT) in patients with suspicious breast lesions.

Materials and methods

Forty-eight patients with 59 breast lesions underwent an [¹⁸F]-FDG PET/CT study in the prone position with a dual-time-point acquisition performed in the early phase 1 h after FDG administration (PET-1) and in the delayed phase 3 h after FDG administration (PET-2). Both examinations were evaluated qualitatively and semiquantitatively with calculation of the mean percentage variation of the standard uptake values (Δ% SUV_max) between PET-1 and PET-2. All lesions with an SUV_max ≥2.5 at PET-1 or a reduction in SUV between PET-1 and PET-2 were considered benign. The definitive histopathological diagnosis was available for all patients included in the study.

Results

The dual-time-point acquisition of [¹⁸F]-FDG PET/CT displayed an accuracy of 85% for lesions with an SUV_max ≥2.5 and/or positive Δ% SUV_max, with sensitivity and specificity values of 81% and 100% compared with 69%, 63% (both p<0.001) and 100% (p=n.s.), respectively, for the single-time-point acquisition. Malignant lesions showed an increase in FDG uptake between PET-1 and PET-2, with a Δ% SUV_max of 10±7 (p<0.04). In contrast, benign lesions showed a decrease in SUV between PET-1 and PET-2, with aΔ% SUV_max of ?21±7 (p<0.001).

Conclusions

The delayed repeat acquisition of PET images improves the accuracy of [¹⁸F]-FDG PET/CT in patients with suspicious breast lesions with respect to the single-time-point acquisition. In addition, malignant breast lesions displayed an increase in FDG uptake over time, whereas benign lesions showed a reduction. These variations in FDG uptake between PET-1 and PET-2 are a reliable parameter that can be used for differentiating between benign and malignant breast lesions.