Novel imaging techniques in refractory pituitary adenomas.

Accurate localization of the site(s) of active disease is key to informing decision-making in the management of refractory pituitary adenomas when autonomous hormone secretion and/or continued tumor growth challenge conventional therapeutic approaches. In this context, the use of non-standard MR sequences, alternative post-acquisition image processing, or molecular (functional) imaging may provide valuable additional information to inform patient management.

Modern imaging in Cushing's disease.

Management of Cushing's disease is informed by dedicated imaging of the sella and parasellar regions. Although magnetic resonance imaging (MRI) remains the investigation of choice, a significant proportion (30-50%) of corticotroph tumours are so small as to render MRI indeterminate or negative when using standard clinical sequences. In this context, alternative MR protocols [e.g. 3D gradient (recalled) echo, with acquisition of volumetric data] may allow detection of tumors that have not been previously visualized. The use of hybrid molecular imaging (e.g. 11C-methionine positron emission tomography coregistered with volumetric MRI) has also been proposed as an additional modality for localizing microadenomas.

11C-methionine PET aids localization of microprolactinomas in patients with intolerance or resistance to dopamine agonist therapy.

PURPOSE: To assess the potential for 11C-methionine PET (Met-PET) coregistered with volumetric magnetic resonance imaging (Met-PET/MRCR) to inform clinical decision making in patients with poorly visualized or occult microprolactinomas and dopamine agonist intolerance or resistance. PATIENTS AND METHODS: Thirteen patients with pituitary microprolactinomas, and who were intolerant (n = 11) or resistant (n = 2) to dopamine agonist therapy, were referred to our specialist pituitary centre for Met-PET/MRCR between 2016 and 2020. All patients had persistent hyperprolactinemia and were being considered for surgical intervention, but standard clinical MRI had shown either no visible adenoma or equivocal appearances. RESULTS: In all 13 patients Met-PET/MRCR demonstrated a single focus of avid tracer uptake. This was localized either to the right or left side of the sella in 12 subjects. In one patient, who had previously undergone surgery for a left-sided adenoma, recurrent tumor was unexpectedly identified in the left cavernous sinus. Five patients underwent endoscopic transsphenoidal selective adenomectomy, with subsequent complete remission of hyperprolactinaemia and normalization of other pituitary function; three patients are awaiting surgery. In the patient with inoperable cavernous sinus disease PET-guided stereotactic radiosurgery (SRS) was performed with subsequent near-normalization of serum prolactin. Two patients elected for a further trial of medical therapy, while two declined surgery or radiotherapy and chose to remain off medical treatment. CONCLUSIONS: In patients with dopamine agonist intolerance or resistance, and indeterminate pituitary MRI, molecular (functional) imaging with Met-PET/MRCR can allow precise localization of a microprolactinoma to facilitate selective surgical adenomectomy or SRS.

Combined MR direct thrombus imaging and non-contrast magnetic resonance venography reveal the evolution of deep vein thrombosis: a feasibility study.

OBJECTIVES: Lower limb deep venous thrombosis (DVT) is a common condition with high morbidity and mortality. The aim of the study was to investigate the temporal evolution of the acute thrombus by magnetic resonance imaging (MRI) and its relationship to venous recanalization in patients with recurrent DVTs. METHODS: Thirteen patients with newly diagnosed lower limb DVTs underwent MRI with non-contrast MR venography (NC-MRV) and MR direct thrombus imaging (MR-DTI), an inversion-recovery water-selective fast gradient-echo acquisition. Imaging was performed within 7 days of the acute thrombotic event, then at 3 and 6 months. RESULTS: By 3 months from the thrombotic event a third of the thrombi had resolved and by 6 months about half of the cases had resolved on the basis of vein recanalisation using NC-MRV. On the initial MR-DTI acute thrombus was clearly depicted by hyperintense signal, while the remaining thrombi were predominantly low signal at 3 and 6 months. Some residual thrombi contained small and fragmented persisting hyperintense areas at 3 months, clearing almost completely by 6 months. CONCLUSIONS: Our study suggests that synergistic venous assessment with combined NC-MRV and MR-DTI is able to distinguish acute venous thrombosis from the established (old) or evolving DVT detected by ultrasound. KEY POINTS: • MRI can distinguish between acute and evolving or chronic lower limb DVT • Two advanced MRI techniques can follow the evolution of lower limb DVT • MRI could be used to avoid an incorrect diagnosis of recurrent DVT • MRI could help avoid the risks and complications of lifelong anticoagulation therapy.

An optoacoustic imaging feature set to characterise blood vessels surrounding benign and malignant breast lesions.

Combining optoacoustic (OA) imaging with ultrasound (US) enables visualisation of functional blood vasculature in breast lesions by OA to be overlaid with the morphological information of US. Here, we develop a simple OA feature set to differentiate benign and malignant breast lesions. 94 female patients with benign, indeterminate or suspicious lesions were recruited and underwent OA-US. An OA-US imaging feature set was developed using images from the first 38 patients, which contained 14 malignant and 8 benign solid lesions. Two independent radiologists blindly scored the OA-US images of a further 56 patients, which included 31 malignant and 13 benign solid lesions, with a sensitivity of 96.8% and specificity of 84.6%. Our findings indicate that OA-US can reveal vascular patterns of breast lesions that indicate malignancy using a simple feature set based on single wavelength OA data, which is therefore amenable to application in low resource settings for breast cancer management.

Neurologically asymptomatic cerebral oligometastatic prostate carcinoma metastasis identified on [Ga]Ga-THP-PSMA PET/CT.

BACKGROUND: Brain metastases from prostate cancer are rare and usually only occur in the context of widespread systemic disease. This is the first case report of a solitary brain oligometastasis, in a neurologically intact prostate cancer patient with no other systemic disease, detected using [68Ga]Ga-THP-PSMA PET/CT and only the second one using a PSMA-based radiopharmaceutical. CASE PRESENTATION: We report the case of a prostate cancer patient presenting 5 years after robot-assisted laparoscopic prostatectomy with biochemical recurrence, no neurological symptoms, and in the absence of metastatic lesions in the body on conventional imaging. A solitary cerebral metastasis was detected using [68Ga]Ga-THP-PSMA PET/CT, surgically resected, leading to a drop in serum PSA and a good recovery. CONCLUSION: In this case, [68Ga]Ga-THP-PSMA PET/CT resulted in a major change in clinical management and avoided additional morbidity associated with delayed diagnosis and treatment. This report demonstrates the importance of considering the presence of metastatic disease outside the conventional locations of prostate cancer spread, as well as the importance of ensuring comprehensive [68Ga]Ga-PSMA PET/CT coverage from vertex to upper thighs.

Correction to: Neurologically asymptomatic cerebral oligometastatic prostate carcinoma metastasis identified on [Ga]Ga-THP-PSMA PET/CT.

An amendment to this paper has been published and can be accessed via the original article.

The importance of AIF ROI selection in DCE-MRI renography: reproducibility and variability of renal perfusion and filtration.

PURPOSE: The aim of this study was to investigate (a) the effect the choice of the region of interest (ROI) defining the aortic input function (AIF) has on the estimation of renal perfusion and filtration in dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) renography, and (b) the reproducibility of these parameters. Using renal DCE-MRI and a three-compartment model analysis, this work evaluated the effect two different AIFs, derived from variable sized ROIs in the aorta, has on calculating DCE-MRI renal perfusion and filtration values in a group of healthy adult volunteers who underwent two consecutive renal DCE-MRI studies. METHODS: Fifteen healthy volunteers underwent two DCE-MRI studies under similar physiological conditions. Oblique-coronal DCE-MRI data volumes were acquired on a 1.5 T Siemens Avanto scanner with a 3D-FLASH pulse-sequence (TE/TR=0.53/1.63 ms, flip angle=17 degrees , acquisition matrix=128 x 104 voxels, strong fat saturation, PAT factor=2 (GRAPPA) and 400 mm x 325 mm FOV). Each dynamic dataset consisted of 18 slices of 7.5mm thickness (no gap) and an in-plane resolution of 3.1 mm x 3.1mm, acquired every 2.5s for not less than 5 minutes. During the MR scan a dose of 0.05 m mol (0.1 mL)kg(-1) body weight of dimeglumine gadopentetate (Magnevist) was injected intravenously (2 mLs(-1) injection rate), followed by a 15 mL saline flush at the same rate, using a MR-compatible automated injector (Spectris). Two AIFs were defined for each volunteer by drawing two ROIs in the aorta for each study. Renal perfusion and glomerular filtration rate (GFR) values were then calculated for each of the AIFs using a modified Tofts Renal Model (TRM). Both renal perfusion and GFR were expressed in mL min(-1)100 mL(-1) of tissue. RESULTS AND CONCLUSION: Inter-individual reproducibility tests for renal perfusion and glomerular filtration rate showed that the size of AIF ROIs significantly affects calculated values of perfusion and GFR (p-values <0.02). No significant differences were observed when comparing perfusion and GFR values in the same volunteer between scans performed on different days (p-values >0.22). From our study we conclude that while DCE-MRI derived indices of renal function are reproducible in the same individual when imaged on different days, the size of the aortic ROI and hence the AIF has a significant influence on calculated renal perfusion and GFR values. Currently there is no accepted standard for drawing the aortic ROI and no standardized approach for the AIF definition in renal DCE-MRI studies.

Partial volume effects in dynamic contrast magnetic resonance renal studies.

This is the first study of partial volume effect in quantifying renal function on dynamic contrast enhanced magnetic resonance imaging. Dynamic image data were acquired for a cohort of 10 healthy volunteers. Following respiratory motion correction, each voxel location was assigned a mixing vector representing the 'overspilling' contributions of each tissue due to the convolution action of the imaging system's point spread function. This was used to recover the true intensities associated with each constituent tissue. Thus, non-renal contributions from liver, spleen and other surrounding tissues could be eliminated from the observed time-intensity curves derived from a typical renal cortical region of interest. This analysis produced a change in the early slope of the renal curve, which subsequently resulted in an enhanced glomerular filtration rate estimate. This effect was consistently observed in a Rutland-Patlak analysis of the time-intensity data: the volunteer cohort produced a partial volume effect corrected mean enhancement of 36% in relative glomerular filtration rate with a mean improvement of 7% in r(2) fitting of the Rutland-Patlak model compared to the same analysis undertaken without partial volume effect correction. This analysis strongly supports the notion that dynamic contrast enhanced magnetic resonance imaging of kidneys is substantially affected by the partial volume effect, and that this is a significant obfuscating factor in subsequent glomerular filtration rate estimation.

Reproducibility of the aortic input function (AIF) derived from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) of the kidneys in a volunteer study.

PURPOSE: The aim of this study was to investigate the maximum height, area under the curve (AUC) and full width at half maximum (FWHM) of the aortic input function (AIF) in renal dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) studies. We evaluated the significance of choice of size for regions of interest (ROI) in the aorta, reproducibility and inter-observer agreement of AIF measurements in healthy volunteers for renal DCE-MRI studies. METHODS: Fifteen healthy volunteers (nine males, six females), mean age 28.8 years (range 23-36 years), underwent two DCE-MRI kidney studies under similar conditions. Oblique-coronal DCE-MRI data volumes were acquired on a 1.5 T Siemens Avanto scanner with a 3D-FLASH pulse-sequence (TE/TR=0.53/1.63 ms, flip angle=17 degrees, acquisition matrix=128 x 104 voxels, strong fat saturation, PAT factor=2 (GRAPPA) and 400 mm x 325 mm FOV). Each dynamic dataset consisted of 18 slices of 7.5 mm thickness (no gap) and an in-plane resolution of 3.1 mm x 3.1 mm, acquired every 2.5 s for >5 min. During the MR scan a dose of 0.05 mmol (0.1 mL) kg(-1) body weight of dimeglumine gadopentetate (Magnevist) was injected intravenously (2 mL s(-1) injection rate), followed by a 15 mL saline flush at the same rate, using a MR-compatible automated injector (Spectris). For each DCE-MRI study two observers each drew two ROIs in the abdominal aorta. Both ROIs were 3 voxels in width and had the same inferior limit (just above the emergence of the renal arteries from the aorta) but had different heights (4 voxels for one ROI and 10 voxels for the other). The dimensions, position and time of drawing the ROIs in the dynamic study were standardised between observers prior to data analysis. Mean signal intensities measured in the ROIs were plotted over time, representing the AIF. For each study, AIF 1 was derived from ROI 1 and AIF 2 was derived from ROI 2. RESULTS AND CONCLUSION: Paired t-tests for inter-observer comparison on the pooled 30 DCE-MRI studies, showed good correlations (correlation coefficients >0.85) with no significant differences (p-values >0.82) when comparing the peak value, AUC and FWHM of the AIFs. Thus the results were operator independent. The size of the aortic ROIs significantly affected all measured parameters of the AIF (p-values <0.039). However, correlation coefficients when comparing AIF 1 and AIF 2 were high for all evaluated AIF parameters (correlation coefficients >0.88), indicating a similar shape and temporal dynamic of the passage of the contrast agent through the aorta. When comparing the intra-individual DCE-MRI studies for each volunteer all AIF parameters had p-values >0.22 and correlation coefficients <0.82, with the exception of the FWHM, which had a correlation coefficient of 0.96 showing a significant variation in AIF parameters in the same volunteer on different days.