Eligibility for 177Lu-PSMA Therapy Depends on the Choice of Companion Diagnostic Tracer: A Comparison of 68Ga-PSMA-11 and 99mTc-MIP-1404 in Metastatic Castration-Resistant Prostate Cancer

¹⁷⁷Lu-prostate-specific membrane antigen-617 (¹⁷⁷Lu-PSMA-617) is an effective therapy for metastatic castration-resistant prostate cancer (mCRPC), with evidence of improved survival over standard care. The VISION trial inclusion criteria required a metastatic lesion-to-liver ratio of greater than 1 on ⁶⁸Ga-PSMA-11 PET scans. We aimed to determine whether an equivalent ratio is suitable for a SPECT tracer, ^99mTc-MIP-1404, and to compare lesion and lesion-to-normal-organ ratios between the 2 radiotracers. Methods: Two cohorts of patients with mCRPC matched for age, prostate-specific antigen level, and total Gleason score, with either ^99mTc-MIP-1404 SPECT/CT (n = 25) or ⁶⁸Ga-PSMA-11 PET/CT (n = 25) scans, were included for analysis. Up to 3 lesions in each site (prostate/prostate bed, lymph nodes, bone and soft-tissue metastases) as well as normal liver, parotid gland, spleen, and mediastinal blood-pool SUV_max were measured. Results: ^99mTc-MIP-1404 SPECT lesion SUV_max was not significantly different from ⁶⁸Ga-PSMA-11 PET (median, 18.2 vs. 17.3; P = 0.93). However, ^99mTc-MIP-1404 liver SUV_max was higher (median, 8.5 vs. 5.8; P = 0.002) and lesion-to-liver ratios were lower (median, 2.7 vs. 3.5; P = 0.009). There was no significant difference in parotid gland or splenic SUV_max or lesion-to-parotid gland ratios between the 2 tracers although there was a small difference in lesion-to-spleen ratios (P = 0.034). Conclusion: There are differences in biodistribution and, in particular, liver activity, between ⁶⁸Ga-PSMA-11 and ^99mTc-MIP-1404. Therefore, if ^99mTc-MIP-1404 is used to assess eligibility for ¹⁷⁷Lu-PSMA-617 therapy, a lower adjusted lesion-to-liver ratio should be used.

Radionuclide calibrator intercomparison study of clinical PET centres in England to a single traceable 68Ge syringe source

OBJECTIVES

The aim of this study was to characterize national variation in radionuclide calibrator activity response to a single National Institute of Standards and Technology (NIST) traceable reference Ge source used as a surrogate for F at clinical PET centres in England using National Physical Laboratory approved techniques.

METHODS

Readings from 20 instruments at 13 centres using local F and Ge factor settings were recorded with the source located in vial and syringe positions. Ten repeat measurements were conducted to investigate repeatability using % coefficient of variability (COV). Comparison ratios to investigate accuracy were made between calibrator responses and decay-corrected NISTref reference activity for syringe and vial position measurements.

RESULTS

The maximum %COV was 0.79%, while 90, 95 and 80% of calibrators conformed to 5% accuracy for F syringe, Ge syringe and Ge vial position readings, respectively. We revealed a trend towards reduced bias in measurements using Veenstra devices for F and using Capintec devices for Ge factor settings.

CONCLUSIONS

This study demonstrated good repeatability in local device measurements. In total, 70% of English calibrators tested and 88% of all measurements performed achieved 5% accuracy. While statistically significant bias was exhibited between different vendor equipment dependent upon radioisotope selected, our study recommends regular traceability checks for optimum instrument performance conducted within National Metrology Institutes guidelines.

Prognostic value of 18FDG PET/CT volumetric parameters in the survival prediction of patients with pancreatic cancer

PURPOSE

To investigate the value of 18 FDG PET/CT volumetric parameters in the prediction of overall survival (OS) in patients with pancreatic cancer and also, assess their independence relative to well-established clinico-pathological variables.

METHODS

We conducted a retrospective analysis of patients with a confirmed diagnosis of pancreatic cancer who underwent 18 FDG PET/CT. The tumour maximum standardised uptake value (SUVmax) in addition to SUVmean, metabolic tumour volume (MTV) and total lesion glycolysis (TLG) were calculated. The prognostic value of 18 FDG PET/CT and clinico-pathological parameters for OS were assessed using univariate and multivariable analyses.

RESULTS

A sum of 89 patients were analysed in this study. Median survival for patients categorised as having high TLG (≥55) and low TLG (<55) was 18 vs 5 months (p < 0.001). Similarly, the respective high vs low SUVmean, MTV and SUVmax were 18 vs 6 months (p = 0.001), 16 vs 6 months (p = 0.002) and 18 vs 6 months (p = 0.001). Univariate analysis showed SUVmax, SUVmean, MTV, TLG, tumour size, tumour differentiation and presence of distant metastasis as prognostic factors for OS. On multivariable analysis, TLG (HR 2.0, 95% CI 1.26-3.18, p = 0.004) and the presence of distant metastasis (HR 3.37, 95% CI 1.97-5.77, p < 0.001) emerged as independent prognostic factors. Subgroup analysis identified TLG as the only significant PET metric after adjusting for the presence of distant metastasis.

CONCLUSIONS

18 FDG PET/CT is a useful tool in the preoperative evaluation of patients with pancreatic cancer. Tumour TLG offer an independent prognostic value in both potentially operable and metastatic disease settings.

Positron emission tomography PET/CT harmonisation study of different clinical PET/CT scanners using commercially available software

Objectives:

Harmonisation is the process whereby standardised uptake values from different scanners can be made comparable. This PET/CT pilot study aimed to evaluate the effectiveness of harmonisation of a modern scanner with image reconstruction incorporating resolution recovery (RR) with another vendor older scanner operated in two-dimensional (2D) mode, and for both against a European standard (EARL). The vendor-proprietary software EQ•PET was used, which achieves harmonisation with a Gaussian smoothing. A substudy investigated effect of RR on harmonisation.

Methods:

Phantom studies on each scanner were performed to optimise the smoothing parameters required to achieve successful harmonisation. 80 patients were retrospectively selected; half were imaged on each scanner. As proof of principle, a cohort of 10 patients was selected from the modern scanner subjects to study the effects of RR on harmonisation.

Results:

Before harmonisation, the modern scanner without RR adhered to EARL specification. Using the phantom data, filters were derived for optimal harmonisation between scanners and with and without RR as applicable, to the EARL standard. The 80-patient cohort did not reveal any statistically significant differences. In the 10-patient cohort SUVmax for RR > no RR irrespective of harmonisation but differences lacked statistical significance (one-way ANOVA F(3.36) = 0.37, p = 0.78). Bland-Altman analysis showed that harmonisation reduced the SUVmax ratio between RR and no RR to 1.07 (95% CI 0.96–1.18) with no outliers.

Conclusions:

EQ•PET successfully enabled harmonisation between modern and older scanners and against the EARL standard. Harmonisation reduces SUVmax and dependence on the use of RR in the modern scanner.

Advances in knowledge:

EQ•PET is feasible to harmonise different PET/CT scanners and reduces the effect of RR on SUVmax.

Treatment of classical Hodgkin lymphoma in young adults aged 18-30 years with a modified paediatric Hodgkin lymphoma protocol. Results of a multicentre phase II clinical trial (CRUK/08/012)

This phase II trial was designed to determine the safety and efficacy of a modified paediatric risk-stratified protocol in young adults (18-30 years) with classical Hodgkin Lymphoma. The primary end-point was neurotoxicity rate. The incidence of grade 3 neurotoxicity was 11% (80% CI, 5-19%); a true rate of neuropathy of >15% cannot be excluded. Neuropathy and associated deterioration in quality of life was largely reversible. The overall response rate was 100% with 40% complete remission (CR) rate. Twelve months disease-free survival (DFS) was 91%. We demonstrate that a risk-stratified paediatric combined modality treatment approach can be delivered to young adults without significant irreversible neuropathy.

Effect of PET Image Reconstruction Techniques on Unexpected Aorta Uptake

Objectives:

To determine if unexpected aorta uptake seen in some patients is influenced by popular modern reconstruction algorithms using semi-quantitative and qualitative analysis.

Methods:

Twenty-five consecutive patients without suspected vascular disease were selected for 18F-FDG positron emission tomography/ computed tomography (PET/CT) scanning and images of the aorta were created using iterative reconstruction (IT), IT + time of flight (TOF), IT + TOF + point spread function correction (referred collectively as UHD) with and without metal artefact reduction (MAR) algorithms. An experienced radiologist created aorta and blood pool (BP) regions of interests then copied these to all reconstructions for accurate positioning before recording target aorta standardized-uptake-values (SUV_max) and background BP SUV_mean. Furthermore, target-to-background ratio (TBR_max) was defined by aorta SUV_max-to-BP SUV_mean ratio for more analysis.

Results:

For aorta SUV_max with IT, IT + TOF, UHD, UHD + MAR reconstructions the mean ± standard deviation recorded were 2.15±0.43, 2.25±0.51, 2.25±0.45 and 2.09±0.4, respectively. Values for BP SUV_mean were 1.61±0.31, 1.58±0.28, 1.58±0.28 and 1.47±0.25, respectively. Likewise, for TBR_max these were 1.35±0.19, 1.43±0.21, 1.43±0.19, 1.43±0.18, respectively. ANOVA analysis revealed no significant differences for aorta SUV_max (F(0.86) p=0.46), BP SUV_mean (F(1.22) p=0.31) or TBR_max (F(0.99) p=0.4). However, the qualitative visual analysis revealed significant differences between IT + TOF with UHD (p=0.02) or UHD + MAR (p=0.02).

Conclusion:

Reconstruction algorithm effect on aorta SUV_max or BP SUV_mean or TBR_max was not statistically significant. However, qualitative visual analysis showed significant differences between IT + TOF as compared with UHD or UHD + MAR reconstructions. Harmonization of techniques with a larger patient cohort is recommended in future clinical trials.

PET-PANC: multicentre prospective diagnostic accuracy and health economic analysis study of the impact of combined modality 18fluorine-2-fluoro-2-deoxy-d-glucose positron emission tomography with computed tomography scanning in the diagnosis and management of pancreatic cancer

BACKGROUND

Pancreatic cancer diagnosis and staging can be difficult in 10-20% of patients. Positron emission tomography (PET)/computed tomography (CT) adds precise anatomical localisation to functional data. The use of PET/CT may add further value to the diagnosis and staging of pancreatic cancer.

OBJECTIVE

To determine the incremental diagnostic accuracy and impact of PET/CT in addition to standard diagnostic work-up in patients with suspected pancreatic cancer.

DESIGN

A multicentre prospective diagnostic accuracy and clinical value study of PET/CT in suspected pancreatic malignancy.

PARTICIPANTS

Patients with suspected pancreatic malignancy.

INTERVENTIONS

All patients to undergo PET/CT following standard diagnostic work-up.

MAIN OUTCOME MEASURES

The primary outcome was the incremental diagnostic value of PET/CT in addition to standard diagnostic work-up with multidetector computed tomography (MDCT). Secondary outcomes were (1) changes in patients' diagnosis, staging and management as a result of PET/CT; (2) changes in the costs and effectiveness of patient management as a result of PET/CT; (3) the incremental diagnostic value of PET/CT in chronic pancreatitis; (4) the identification of groups of patients who would benefit most from PET/CT; and (5) the incremental diagnostic value of PET/CT in other pancreatic tumours.

RESULTS

Between 2011 and 2013, 589 patients with suspected pancreatic cancer underwent MDCT and PET/CT, with 550 patients having complete data and in-range PET/CT. Sensitivity and specificity for the diagnosis of pancreatic cancer were 88.5% and 70.6%, respectively, for MDCT and 92.7% and 75.8%, respectively, for PET/CT. The maximum standardised uptake value (SUVmax.) for a pancreatic cancer diagnosis was 7.5. PET/CT demonstrated a significant improvement in relative sensitivity (p = 0.01) and specificity (p = 0.023) compared with MDCT. Incremental likelihood ratios demonstrated that PET/CT significantly improved diagnostic accuracy in all scenarios (p < 0.0002). PET/CT correctly changed the staging of pancreatic cancer in 56 patients (p = 0.001). PET/CT influenced management in 250 (45%) patients. PET/CT stopped resection in 58 (20%) patients who were due to have surgery. The benefit of PET/CT was limited in patients with chronic pancreatitis or other pancreatic tumours. PET/CT was associated with a gain in quality-adjusted life-years of 0.0157 (95% confidence interval -0.0101 to 0.0430). In the base-case model PET/CT was seen to dominate MDCT alone and is thus highly likely to be cost-effective for the UK NHS. PET/CT was seen to be most cost-effective for the subgroup of patients with suspected pancreatic cancer who were thought to be resectable.

CONCLUSION

PET/CT provided a significant incremental diagnostic benefit in the diagnosis of pancreatic cancer and significantly influenced the staging and management of patients. PET/CT had limited utility in chronic pancreatitis and other pancreatic tumours. PET/CT is likely to be cost-effective at current reimbursement rates for PET/CT to the UK NHS. This was not a randomised controlled trial and therefore we do not have any information from patients who would have undergone MDCT only for comparison. In addition, there were issues in estimating costs for PET/CT. Future work should evaluate the role of PET/CT in intraductal papillary mucinous neoplasm and prognosis and response to therapy in patients with pancreatic cancer.

STUDY REGISTRATION

Current Controlled Trials ISRCTN73852054 and UKCRN 8166.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

PET-NECK: a multicentre randomised Phase III non-inferiority trial comparing a positron emission tomography-computerised tomography-guided watch-and-wait policy with planned neck dissection in the management of locally advanced (N2/N3) nodal metastases in patients with squamous cell head and neck cancer

BACKGROUND

Planned neck dissection (ND) after radical chemoradiotherapy (CRT) for locally advanced nodal metastases in patients with head and neck squamous cell carcinoma (HNSCC) remains controversial. Thirty per cent of ND specimens show histological evidence of tumour. Consequently, a significant proportion of clinicians still practise planned ND. Fludeoxyglucose positron emission tomography (PET)-computerised tomography (CT) scanning demonstrated high negative predictive values for persistent nodal disease, providing a possible alternative paradigm to ND. Evidence is sparse and drawn mainly from retrospective single-institution studies, illustrating the need for a prospective randomised controlled trial.

OBJECTIVES

To determine the efficacy and cost-effectiveness of PET-CT-guided surveillance, compared with planned ND, in a multicentre, prospective, randomised setting.

DESIGN

A pragmatic randomised non-inferiority trial comparing PET-CT-guided watch-and-wait policy with the current planned ND policy in HNSCC patients with locally advanced nodal metastases and treated with radical CRT. Patients were randomised in a 1 : 1 ratio. Primary outcomes were overall survival (OS) and cost-effectiveness [incremental cost per incremental quality-adjusted life-year (QALY)]. Cost-effectiveness was assessed over the trial period using individual patient data, and over a lifetime horizon using a decision-analytic model. Secondary outcomes were recurrence in the neck, complication rates and quality of life. The recruitment of 560 patients was planned to detect non-inferior OS in the intervention arm with a 90% power and a type I error of 5%, with non-inferiority defined as having a hazard ratio (HR) of no higher than 1.50. An intention-to-treat analysis was performed by Cox's proportional hazards model.

SETTINGS

Thirty-seven head and neck cancer-treating centres (43 NHS hospitals) throughout the UK.

PARTICIPANTS

Patients with locally advanced nodal metastases of oropharynx, hypopharynx, larynx, oral or occult HNSCC receiving CRT and fit for ND were recruited.

INTERVENTION

Patients randomised to planned ND before or after CRT (control), or CRT followed by fludeoxyglucose PET-CT 10-12 weeks post CRT with ND only if PET-CT showed incomplete or equivocal response of nodal disease (intervention). Balanced by centre, planned ND timing, CRT schedule, disease site and the tumour, node, metastasis stage.

RESULTS

In total, 564 patients were recruited (ND arm, n = 282; and surveillance arm, n = 282; 17% N2a, 61% N2b, 18% N2c and 3% N3). Eighty-four per cent had oropharyngeal cancer. Seventy-five per cent of tested cases were p16 positive. The median time to follow-up was 36 months. The HR for OS was 0.92 [95% confidence interval (CI) 0.65 to 1.32], indicating non-inferiority. The upper limit of the non-inferiority HR margin of 1.50, which was informed by patient advisors to the project, lies at the 99.6 percentile of this estimate (p = 0.004). There were no differences in this result by p16 status. There were 54 NDs performed in the surveillance arm, with 22 surgical complications, and 221 NDs in the ND arm, with 85 complications. Quality-of-life scores were slightly better in the surveillance arm. Compared with planned ND, PET-CT surveillance produced an incremental net health benefit of 0.16 QALYs (95% CI 0.03 to 0.28 QALYs) over the trial period and 0.21 QALYs (95% CI -0.41 to 0.85 QALYs) over the modelled lifetime horizon.

LIMITATIONS

Pragmatic randomised controlled trial with a 36-month median follow-up.

CONCLUSIONS

PET-CT-guided active surveillance showed similar survival outcomes to ND but resulted in considerably fewer NDs, fewer complications and lower costs, supporting its use in routine practice.

FUTURE WORK

PET-CT surveillance is cost-effective in the short term, and long-term cost-effectiveness could be addressed in future work.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN13735240.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 21, No. 17. See the NIHR Journals Library website for further project information.

Pre-clinical Positron Emission Tomography Reconstruction Algorithm Effect on Cu-64 ATSM Lesion Hypoxia

Objective:

Application of distinct positron emission tomography (PET) scan reconstruction algorithms can lead to statistically significant differences in measuring lesion functional properties. We looked at the influence of two-dimensional filtered back projection (2D FBP), two-dimensional ordered subset expectation maximization (2D OSEM), three-dimensional ordered subset expectation maximization (3D OSEM) without 3D maximum a posteriori and with (3D OSEM MAP) on lesion hypoxia tracer uptake using a pre-clinical PET scanner.

Methods:

Reconstructed images of a rodent tumor model bearing P22 carcinosarcoma injected with hypoxia tracer Copper-64-Diacetyl-bis (N4-methylthiosemicarbazone) (i.e. Cu-64 ATSM) were analyzed at 10 minute intervals till 60 minute post injection. Lesion maximum standardized uptake values (SUV_max) and SUV_max/background SUV_mean (T/B) were recorded and investigated after application of multiple algorithm and reconstruction parameters to assess their influence on Cu-64 ATSM measurements and associated trends over time.

Results:

SUV_maxSUV_max or T/B between 2D FBP, exhibited convergence for OSEM reconstructions while ANOVA results showed a significant difference in SUV_max or T/B between 2D FBP, 2D OSEM, 3D OSEM and 3D OSEM MAP reconstructions across all time frames. SUV_max and T/B were greatest in magnitude for 2D OSEM followed by 3D OSEM MAP, 3D OSEM and then 2D FBP at all time frames respectively. Similarly SUV_max and T/B standard deviations (SD) were lowest for 2D OSEM in comparison with other algorithms.

Conclusion:

Significantly higher magnitude lesion SUV_max and T/B combined with lower SD were observed using 2D OSEM reconstruction in comparison with 2D FBP, 3D OSEM and 3D OSEM MAP algorithms at all time frames. Results are SUV_max or T/B between 2D FBP, consistent with other published studies however more specimens are required for full validation.

Impact of the point spread function on maximum standardized uptake value measurements in patients with pulmonary cancer

Maximum standardized uptake value (SUVmax) from fluorodeoxyglucose (FDG) positron emission tomography (PET) scans is a semi quantitative measure that is increasingly used in the clinical practice for diagnostic and therapeutic response assessment purposes. Technological advances such as the implementation of the point spread function (PSF) in the reconstruction algorithm have led to higher signal to noise ratio and increased spatial resolution. The impact on SUVmax measurements has not been studied in clinical setting. We studied the impact of PSF on SUVmax in 30 consecutive lung cancer patients. SUVmax values were measured on PET-computed tomography (CT) scans reconstructed iteratively with and without PSF (respectively high-definition [HD] and non-HD). HD SUVmax values were significantly higher than non-HD SUVmax. There was excellent correlation between HD and non-HD values. Details of reconstruction and PSF implementation in particular have important consequences on SUV values. Nuclear Medicine physicians and radiologists should be aware of the reconstruction parameters of PET-CT scans when they report or rely on SUV measurements.

FLT PET-CT in evaluation of treatment response

PURPOSE

Review published studies to investigate the value of clinical 3-deoxy-3-(18)F-fluorothymidine (FLT) positron emission tomography (PET) in predicting response to treatment.

MATERIALS AND METHODS

Interrogate databases to identify suitable publications between 2007 and 2013 with a minimum of five patients. Articles within the inclusion criteria were reviewed with major findings reported leading to a descriptive analysis of FLT PET in therapy response.

RESULTS

Lesions investigated included glioma, head and neck, esophageal, lung, breast, gastric, renal, rectal, sarcomas, germ cell, lymphomas, leukemia, and melanoma resulting in a total of 34 studies analyzed. A variety of therapies were applied and dissimilar PET protocols were widespread making direct comparison between studies challenging. Though baseline, early and late therapy scans were popular particularly in chemotherapy regimes. Most studies investigated showed significantly reduced FLT uptake during or after therapy compared with pretreatment scans.

CONCLUSION

Current evidence suggests FLT PET has a positive role to play in predicting therapy response especially in brain, lung, and breast cancers where good correlation with Ki-67 is observed. However, careful attention must be placed in undertaking larger clinical trials where harmonization of scanning and analysis protocols are strictly adhered to fully assess the true potential of FLT PET in predicting response to treatment.

Abstract P4-01-07: Evaluation of FLT PET-CT as an imaging biomarker of proliferation in primary breast cancer

Background

[18F]flurothymidine (FLT) is proposed as an positron emission tomography (PET) imaging biomarker of proliferation for breast cancer. The aim of this prospective study was to assess the feasibility of FLT PET-CT as a technique for predicting response to neoadjuvant chemotherapy (NAC) in operable breast cancer and to compare baseline FLT to Ki-67.

Methods

20 patients with primary breast cancer were recruited into this study and 19 received NAC with FEC (n = 6) or FEC-T (n = 13). A baseline FLT PET-CT scan was performed and repeated before the second cycle of chemotherapy. Expression of Ki-67 in the diagnostic biopsy was quantified after being stained by Dako Ki67 MIB-1 antibody and% positive cells scored. From the FLT PET-CT scans standardized uptake value maximum (SUVmax) were calculated.

Results

All 20 patients completed the baseline scan and 17 completed the second scan. Baseline Ki-67 results were available for 19 patients. Median age was 52 years (range 32 to 67), 12 patients were ER/ PR +ve, 6 Her-2 +ve and 6 triple negative.

Mean baseline SUVmax was 7.3 (range 2.92 to 13.87) and 4.62 (range 1.79 to 14.15) post 1 cycle of NAC (range 7 to 14 days), representing a drop of 2.68 (36.3%). Mean baseline Ki-67 was 32.23 (range 2.3 to 68.4). Pearsons correlation showed a significant correlation between pre-chemotherapy Ki-67 and SUVmax of 0.604 (p = 0.006).

7 out of 17 (41%) patients achieved near pCR or pCR (pathological responders) after NAC and all of these had a reduction in SUVmax with a mean percentage value of –36.5% (range -0.5% to -62.5%). 10 out of 17 (59%) patients were non-responders and 8 of these had a reduction in SUVmax with a mean percentage value of -36.2% (range 11.3% to -70.7).

Conclusions

Baseline SUVmax measurements of FLT PET-CT were significantly related to Ki-67 suggesting that it is a proliferation biomarker. However, in this series neither the baseline value or the change in SUVmax after one cycle of NAC were able to predict response as most patients had a sizeable SUVmax reduction.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-01-07.

Age and dose-limited PET-CT scan regime in lymphoma: between the devil and the deep blue sea?

In this study the authors speculate about hypothetical effective-dose (E) reduction through limiting post-chemotherapy PET-CT scanning to lymphoma sites previously identified on pre-treatment CT. E reductions/scan time savings are compared between post-treatment standard and theoretically limited PET-CT scans. The influence of patient age with E savings and associated clinical implication for 100 subjects are discussed. The greatest E theoretical savings of 52 and 32% for the CT contribution and combined PET-CT, respectively, were seen in patients <18 y old using limited scans in this study, with a potential mean time saving of 16 min per patient across the entire cohort. However, the limited PET-CT regime here missed a 1% rate of unexpected cancer that standard PET-CT recorded. The authors recommend performing larger scale multi-centre studies comparing PET-CT pre- and post-chemotherapy to establish full clinical efficacy of this method.

Investigation of dose minimisation protocol for 18F-FDG PET-CT in the management of lymphoma postchemotherapy followup

INTRODUCTION

(18)F-FDG-PET-CT plays an important role in the management of lymphoma postchemotherapy followup. Some centres perform prechemotherapy baseline CT and postchemotherapy PETCT. With a concern of radiation burden, especially in young patients, this study aimed to assess if PETCT radiation dose could be reduced.

METHODS

Retrospective analysis of 100 lymphoma patients was performed to record sites of disease on prechemotherapy CT and postchemotherapy PETCT. The potential reduction in radiation and time achieved with PETCT limited to sites of known disease identified on prechemotherapy CT was calculated.

RESULTS

No FDG-uptake was seen in 72 cases. FDG uptake at known disease sites was seen in 24. Of the remaining 4, one had clinically significant pathology, a rectal adenocarcinoma. PETCT did not reveal any unexpected sites of lymphoma. Limiting PETCT to sites of known disease would have saved a mean radiation dose of 4 mSv (27.3%), with a mean time of 16 minutes.

CONCLUSION

Our study suggests that young patients may benefit from reduced radiation by limiting PETCT to sites of known disease with low risk of missing significant pathology. However, in older patients, with increased incidence of asymptomatic synchronous malignancies, whole-body PETCT is advisable unless prechemotherapy PETCT has been performed.

Reproducibility of 2D and 3D fractal analysis techniques for the assessment of spatial heterogeneity of regional blood flow in rectal cancer

PURPOSE

To characterize the two-dimensional (2D) and three-dimensional (3D) fractal properties of rectal cancer regional blood flow assessed by using volumetric helical perfusion computed tomography (CT) and to determine its reproducibility.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained. Ten prospective patients (eight men, two women; mean age, 72.3 years) with rectal adenocarcinoma underwent two repeated volumetric helical perfusion CT studies (four-dimensional adaptive spiral mode, 11.4-cm z-axis coverage) without intervening treatment within 24 hours, with regional blood flow derived by using deconvolution analysis. Two-dimensional and 3D fractal analyses of the rectal tumor were performed, after segmentation from surrounding structures by using thresholding, to derive fractal dimension and fractal abundance. Reproducibility was quantitatively assessed by using Bland-Altman statistics. Two-dimensional and 3D lacunarity plots were also generated, allowing qualitative assessment of reproducibility. Statistical significance was at 5%.

RESULTS

Mean blood flow was 63.50 mL/min/100 mL ± 8.95 (standard deviation). Good agreement was noted between the repeated studies for fractal dimension; mean difference was -0.024 (95% limits of agreement: -0.212, 0.372) for 2D fractal analysis and -0.024 (95% limits of agreement: -0.307, 0.355) for 3D fractal analysis. Mean difference for fractal abundance was -0.355 (95% limits of agreement: -0.869, 1.579) for 2D fractal analysis and -0.043 (95% limits of agreement: -1.154, 1.239) for 3D fractal analysis. The 95% limits of agreement were narrower for 3D than 2D analysis. Lacunarity plots also visually confirmed close agreement between repeat studies.

CONCLUSION

Regional blood flow in rectal cancer exhibits fractal properties. Good reproducibility was achieved between repeated studies with 2D and 3D fractal analysis.

Assessment of the spatial pattern of colorectal tumour perfusion estimated at perfusion CT using two-dimensional fractal analysis

The aim was to evaluate the feasibility of fractal analysis for assessing the spatial pattern of colorectal tumour perfusion at dynamic contrast-enhanced CT (perfusion CT). Twenty patients with colorectal adenocarcinoma underwent a 65-s perfusion CT study from which a perfusion parametric map was generated using validated commercial software. The tumour was identified by an experienced radiologist, segmented via thresholding and fractal analysis applied using in-house software: fractal dimension, abundance and lacunarity were assessed for the entire outlined tumour and for selected representative areas within the tumour of low and high perfusion. Comparison was made with ten patients with normal colons, processed in a similar manner, using two-way mixed analysis of variance with statistical significance at the 5% level. Fractal values were higher in cancer than normal colon (p < or = 0.001): mean (SD) 1.71 (0.07) versus 1.61 (0.07) for fractal dimension and 7.82 (0.62) and 6.89 (0.47) for fractal abundance. Fractal values were lower in 'high' than 'low' perfusion areas. Lacunarity curves were shifted to the right for cancer compared with normal colon. In conclusion, colorectal cancer mapped by perfusion CT demonstrates fractal properties. Fractal analysis is feasible, potentially providing a quantitative measure of the spatial pattern of tumour perfusion.

Evaluation of normal FDG uptake in palatine tonsil and its potential value for detecting occult head and neck cancers: A PET CT study

OBJECTIVE

The aims of the study were to (1) evaluate the range of physiological FDG uptake in normal pharyngeal palatine tonsil, and (2) investigate the possibility of establishing a cut-off threshold to distinguish between normal pharyngeal palatine tonsil FDG uptake from occult pharyngeal palatine tonsil primary cancer.

METHODS

FDG PET CT of 43 consecutive patients with a low risk of head and neck cancer were reviewed by two observers. Axial PET CT was used to identify foci of FDG uptake related to the pharyngeal palatine tonsil. The highest standardized uptake value, SUVmax, of the left and right pharyngeal palatine tonsil was calculated. Similar analysis was performed on 10 consecutive patents with histologically proven occult pharyngeal palatine tonsil primary cancer.

RESULTS

The mean SUVmax of the 43 right pharyngeal palatine tonsils was 4.82 (range, 1.16-12.74) and 4.68 (range, 0.88-13.65) for the 43 left pharyngeal palatine tonsils with no statistical difference observed (P=0.4). Normal pharyngeal palatine tonsil uptake was generally symmetrical and there was a positive correlation between SUVmax from the left and right sides which was statistically significant (r=0.9, P<0.0001). In the same patient the difference in SUVmax between left and right pharyngeal palatine tonsil ranged from 0.01 to 2.66 and patients with occult pharyngeal palatine tonsil primary cancer it ranged from 0.85 to 11.08. ROC analysis showed that an 'SUVmax difference' cut-off of 0.83 would achieve a sensitivity of 100% and specificity of 81% for detecting occult pharyngeal palatine tonsil primary cancers.

CONCLUSIONS

There is considerable variation of pharyngeal palatine tonsil FDG uptake in patients with no pharyngeal palatine tonsil primary cancer. However, in the same patient there is generally only a small difference in uptake between left and right sides. The absolute difference in SUVmax between left and right pharyngeal palatine tonsil is a potentially useful parameter for distinguishing between normal FDG uptake in pharyngeal palatine tonsil from occult pharyngeal palatine tonsil primary cancer.

Potential novel application of dual time point SUV measurements as a predictor of survival in head and neck cancer

OBJECTIVES

To examine the potential of pre-treatment dual time point [18F]fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) as a tool for improving the assessment of head and neck cancer. Two main areas were investigated: (a) optimum time to start FDG scanning post-injection and (b) potential of SUV obtained from dual time point scanning as a prognostic indicator of survival.

METHODS

Twelve patients with advanced head and neck cancer were prospectively studied. Each patient was scanned using a Siemen's Ecat Exact-47 PET scanner at 1 h and 2 h post-injection. Maximum tumour uptake (SUVt) and ratio of maximum tumour/normal tissue uptake (SUVt/n) were recorded. The optimal time to initiate scanning was investigated by comparing SUVt and SUVt/n with the decision made by two experienced observers as to which scan they preferred to report from, given the choice of the 1 h and 2 h scan in each patient.

RESULTS

A significant difference between 1 h and 2 h SUVt (P<0.004, paired t-test) and between 1 h and 2 h SUVt/n (P<0.0003, paired t-test) was observed. All 2 h SUVt and SUVt/n were greater in magnitude than their respective 1 h SUVt and SUVt/n counterparts. The two observers reported an identical number of lesions from the 1 h and 2 h scans but preferred the 2 h data.

CONCLUSIONS

Tumour stage and the percentage difference in 1 h and 2 h SUVt showed potential as prognostic indicators of long-term survival.

Scoliosis in an Orangutan

STUDY DESIGN

The first case of scoliosis in an Orangutan spine is reported.

OBJECTIVES

To study the nature of scoliosis in the spinal specimen, and to determine the etiologic significance to human idiopathic scoliosis.

SUMMARY OF BACKGROUND DATA

Idiopathic scoliosis has not been observed in primates other than man. Previous studies highlighted the importance of erect posture in the development of idiopathic scoliosis in man.

METHODS

A spinal model of an orangutan spine was studied in great detail to determine its nature. The methods used included plain radiographs, computed tomography scans, a three-dimensional plastic model using rapid prototyping, and dissection of the frozen specimen.

RESULTS

Features similar to human idiopathic scoliosis were noted including a right-side curve, vertebral rotation to convexity, displacement of the spinal cord to the concavity, and an equal number of ribs on either side. No evidence of congenital anomaly was found. Atypical findings included male gender, a short curve, and kyphosis at the apex.

CONCLUSIONS

Although scoliosis found in the orangutan has features similar to idiopathic scoliosis, there also are some dissimilar features, making this diagnosis unlikely. The features observed in this spine suggest that erect posture is important in the morphology of human idiopathic scoliosis.

Combined MR imaging and numerical simulation of flow in realistic arterial bypass graft models

We report methods for (a) transforming a three-dimensional geometry acquired by magnetic resonance angiography (MRA) in vivo, or by imaging a model cast, into a computational surface representation, (b) use of this to construct a three dimensional numerical grid for computational fluid dynamic (CFD) studies, and (c) use of the surface representation to produce a stereo-lithographic replica of the real detailed geometry, at a scale convenient for detailed magnetic resonance imaging (MRI) flow studies. This is applied to assess the local flow field in realistic geometry arterial bypass grafts. Results from a parallel numerical simulation and MRI measurement of flow in an aorto-coronary bypass graft with various inlet flow conditions demonstrate the strong influence of the graft inlet waveform on the perianastomotic flow field. A sinusoidal and a multi harmonic coronary flow waveform both with a mean Reynolds number (Re) of 100 and a Womersley parameter of 2.7 were applied at the graft inlet. A weak axial flow separation region just distal to the toe was found in sinusoidal flow near end deceleration (Re = 25). At the same location and approximately the same point in the cycle (Re = 30) but in coronary flow, the axial flow separation was stronger and more spatially pronounced. No axial flow separation occurred in steady flow for Re = 100. Numerical predictions indicate a region in the vicinity of the suture line (where there is a local narrowing of the graft) with a wall shear magnitude in excess of five times that associated with fully developed flow at the graft inlet.

Preliminary study of potential for rapid prototype and surface scanned radiotherapy facemask production technique

Preliminary investigations into the potential of an elegant technique to create a rudimentary facemask for patient immobilization during radiotherapy treatment are presented. This method combines modern technology to cause the patientfar less discomfort compared with current plaster of Paris (POP) face mould procedures. Near instantaneous patient face scanning is accomplished with charge-coupled devices for imaging in an optical surface scanning system. The surface generated data is input to a rapid prototype (RP) system that creates a life-size model of the patient's face topology. As proof of principle a basic prototype facemask was successfully constructed using this technique and some qualitative comparison measurements for position and surface dose were made. These initial results confirm the validity of this technique and justify the need for further quantitative studies to fully investigate the potential of RP facemasks over POP based methods for mask production.