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Radiol Imaging Cancer. 2024 Jul; 6(4): e230186.
Published online 2024 Jun 7. doi:10.1148/rycan.230186
PMCID: PMC11287224
PMID: 38847615
Katie N. Hunt, MD,
Amy Lynn Conners, MD, Lacey Gray, BS, CNMT, Carrie B. Hruska, PhD, and Michael K. O’Connor, PhD
Author information Article notes Copyright and License information PMC Disclaimer
See commentary "Innovative Advances in Molecular Breast Imaging Biopsy" in volume 6, e240135.
Abstract
Purpose
To develop a molecular breast imaging (MBI)–guided biopsy systemusing dual-detector MBI and to perform initial testing inparticipants.
Materials and Methods
The Stereo Navigator MBI Accessory biopsy system comprises a lowerdetector, upper fenestrated compression paddle, and upper detector. Theupper detector retracts, allowing craniocaudal, oblique, or medial orlateral biopsy approaches. The compression paddle allows insertion of aneedle guide and needle. Lesion depth is calculated by triangulation oflesion location on the upper detector at 0° and 15° andrelative lesion activity on upper and lower detectors. In a prospectivestudy (July 2022–June 2023), participants with Breast ImagingReporting and Data System category 2, 3, 4, or 5 breast lesionsunderwent MBI-guided biopsy. After injection of 740 MBq technetium 99msestamibi, craniocaudal and mediolateral oblique MBI (2-minuteacquisition per view) confirmed lesion visualization. A region ofinterest over the lesion permitted depth calculation in the systemsoftware. Upper detector retraction allowed biopsy device placement.Specimen images were obtained on the retracted upper detector,confirming sampling of the target.
Results
Of 21 participants enrolled (mean age, 50.6 years ± 10.1 [SD]; 21[100%] women), 17 underwent MBI-guided biopsy with concordant pathology.No lesion was observed at the time of biopsy in four participants.Average lesion size was 17 mm (range, 6–38 mm). Average proceduretime, including preprocedure imaging, was 55 minutes ± 13 (range,38–90 minutes). Pathology results included invasive ductalcarcinoma (n = 1), fibroadenoma (n =4), pseudoangiomatous stromal hyperplasia (n = 6), andfibrocystic changes (n = 6).
Conclusion
MBI-guided biopsy using a dual-head system with retractable upperdetector head was feasible, well tolerated, and efficient.
Keywords: Breast Biopsy, Molecular Breast Imaging,Image-guided Biopsy, Molecular Breast Imaging–guided Biopsy,Breast Cancer
Clinical trial registration no. NCT06058650
© RSNA, 2024
See also commentary by Fowler in this issue.
Keywords: Breast Biopsy, Molecular Breast Imaging, Image-guided Biopsy, Molecular Breast Imaging–guided Biopsy, Breast Cancer
Summary
Molecular breast imaging–guided biopsy using a dual-head system withretractable upper detector head was feasible and efficient.
Key Points
■ A novel method of molecular breast imaging (MBI)–guidedbiopsy using a retractable upper detector and two methods of lesiondepth calculation was feasible and well-tolerated in individuals withbreast lesions.
■ Diagnostic and concordant pathology was observed in all 17 studyparticipants who underwent MBI-guided biopsy, with no major proceduralcomplications.
■ MBI-guided biopsy would streamline the evaluation of patientswith a suspicious MBI-detected lesion.
Introduction
Molecular breast imaging (MBI) is a nuclear medicine technique that uses aradiotracer, typically technetium 99m (99mTc) sestamibi, to image areasof increased mitochondrial activity and blood flow within the breast (1). MBI has been used in a variety of clinicalsettings, including supplemental screening in individuals with dense breast tissue,assessment of response to neoadjuvant chemotherapy, problem solving, local cancerstaging, or when breast MRI is indicated but the patient has a contraindication tobreast MRI (2,3). When used as a supplement to screening mammography in individualswith dense breast tissue, studies have demonstrated an incremental cancer detectionrate of 7.7–8.8 cancers per 1000 women screened (4,5). MBI is lessexpensive than breast MRI, and patients with claustrophobia or anothercontraindication to MRI can safely undergo MBI. Additionally, 99mTcsestamibi has a long history of safe use and a low rate of adverse reactions (6). When reactions occur, they are typicallymild, such as a brief metallic taste.
The current standard evaluation of MBI-detected lesions involves diagnosticmammography and/or targeted US imaging. Many MBI-detected lesions are successfullyidentified with conventional imaging and biopsied by stereotactic, tomosynthesis, orUS guidance. However, in approximately 15% of patients, conventional diagnosticimaging does not identify a correlate for the MBI finding (7). If the MBI finding is assessed as suspicious or highlysuggestive of malignancy, patients are recommended to undergo breast MRI. If breastMRI confirms a suspicious finding, MRI-guided biopsy is necessary for pathologicdiagnosis. Breast MRI and MRI-guided biopsy are expensive, and some patients face adifficult choice about whether to pursue an expensive breast MRI and potentialbiopsy versus declining the recommendation for more advanced imaging and tissuediagnosis. The availability of MBI-guided biopsy at substantially less cost than MRIwould streamline the patient experience for workup and diagnosis of MBI-detectedfindings, decrease the costs of implementing MBI into a practice, and improve healthequity by reducing barriers to optimal care for patients with a suspicious findingat MBI.
An earlier generation of nuclear medicine breast imaging, the single-detectorbreast-specific gamma imaging (BSGI) system with a sodium iodide detector, hadbiopsy capability approved by the U.S. Food and Drug Administration (FDA) in 2009(GammaLoc; Dilon Technologies). The BSGI-guided biopsy unit used a slant-holecollimator and principles of stereotaxis to acquire images of 99mTcsestamibi–avid lesions at different angles and calculate lesion depth. Abiopsy system was also developed for use with a dual-detector MBI system with acadmium zinc telluride detector and was approved by the FDA in 2016 (Discovery NM750b; GE HealthCare). This system also used a stereotactic pair at +30° and-30° to determine the depth of a target (8). A disadvantage of both these systems was the long procedure time(44–112 minutes) with a single-detector system (9) and approximately 90 minutes with a dual-detector system(8). Due to changes in vendors, the biopsyaccessories for these systems are not currently available for purchase.
Herein, we present the feasibility of a novel and efficient method of MBI-guidedbiopsy using a dual-detector system to guide vacuum-assisted core needle biopsy oflesions visualized at MBI.
Materials and Methods
Participant Selection
This prospective study, conducted from July 2022 to June 2023, was approved bythe Mayo Clinic Institutional Review Board and complies with the HealthInsurance Portability and Accountability Act (https://www.clinicaltrials.gov; NCT06058650). Allparticipants provided informed written consent before study participation. Womenage 25 years or older with at least one finding visible on any breast imagingmodality (mammography, US, breast MRI, MBI, or contrast-enhanced mammography)were eligible for participation. Figure 1shows a flowchart of participant inclusion and exclusion. Individuals withpreviously biopsied benign lesions as well as American College of RadiologyBreast Imaging Reporting and Data System (BI-RADS) assessment category 2, 3, 4,or 5 lesions could participate (10). Thepurpose of the study was to evaluate the feasibility of the MBI biopsy system,so previously biopsied benign lesions were included to allow correlation betweenthe pathology results from the MBI-guided biopsy and prior pathology.Individuals were excluded from participation if they were pregnant, werelactating or discontinued lactation less than 2 months before the study, wereyounger than 25 years, had a breast implant ipsilateral to the area of interest,had a history of breast biopsy less than 3 months before study enrollment, had ahistory of surgery on the study breast within the previous 12 months, or werescheduled for a sentinel lymph node procedure using 99mTc within 24hours of the MBI-guided biopsy.
Figure 1:
Flowchart of molecular breast imaging (MBI) biopsy participant inclusionand exclusion. BI-RADS = Breast Imaging Reporting and Data System, FDG =fluorodeoxyglucose, MBI = molecular breast imaging.
MBI Biopsy Device Description
The Stereo Navigator MBI Accessory biopsy unit is an upgrade to the LumaGem (CMRNaviscan) dual-head MBI system. The LumaGem was approved by the FDA in 2011 andis a high-resolution dedicated breast gamma camera with dual-head cadmium zinctelluride detectors. Pixel size is 1.6 mm and spatial resolution is 2–5mm. The system uses a widened energy window (110–154 keV) for improvedsensitivity (11,12). The Stereo Navigator MBI Accessory has not beenapproved by the FDA.
The upper detector of the MBI biopsy accessory retracts to allow access to thebreast for a biopsy procedure (Fig 2). Acompression paddle with a needle access window is in place between the upperdetector and breast, maintaining compression when the upper detector isretracted. An alphanumeric grid plate can be attached to the biopsy compressionpaddle to hold a needle guide. The compression paddle is constructed ofbiocompatible materials that are cleaned before each use, similar to needlelocalization paddles for mammography or compression grids for MRI-guided biopsy.The compression paddle is removable, allowing routine MBI on the unit when notbeing used for biopsy.
Figure 2:
(A) Picture shows the dual-detector molecular breast imagingbiopsy unit with the upper detector positioned at 0° (circle).Molecular breast imaging examination is performed with the upperdetector in this position. (B) The upper detector is fullyretracted to allow access to the breast for the biopsy procedure (openarrow). The clear compression paddle remains in place (closed arrow). Analphanumeric grid is placed onto the compression paddle for the biopsyprocedure.
MBI Biopsy Procedure
Within 24 hours before a participant’s MBI-guided biopsy procedure, an MBItechnologist performed a set of quality assurance procedures on the LumaGemsystem in preparation for imaging and biopsy.
After informed consent, a urine pregnancy test was performed to confirm nopregnancy. Participants received an intravenous injection of 740 MBq99mTc sestamibi (20 mCi). The dose for screening and diagnosticMBI at our institution is 300 MBq (8 mCi), but a higher dose was administered todecrease imaging and localization times during the biopsy procedure. Thecombination of the higher administered dose of 99mTc sestamibi andthe application of a denoising algorithm (13) allowed for a reduction in the image acquisition from 10 minutesto 2 minutes. Imaging began within 5 minutes of the 99mTc sestamibiinjection. Bilateral images with a 2-minute acquisition in the craniocaudal andmediolateral oblique orientations were obtained. Two breast imagingfellowship-trained study radiologists (A.L.C. and K.N.H., with 13 and 15 yearsof MBI interpretation experience, respectively) reviewed the MB images withcorrelation to other breast imaging and selected the target lesion(s) andapproach. The MBI gantry could be rotated to allow biopsy access from asuperior, oblique, or medial or lateral approach.
If no MBI abnormalities that warranted biopsy were identified at the time ofprebiopsy imaging, the individual’s participation in the MBI-guidedbiopsy procedure ended. If the finding resolved, no further MBI follow-up wasrecommended, consistent with previously published management of findings onshort-term follow-up MBI (7). If the areaof interest was obscured by background parenchymal uptake, a follow-up MBI wasrecommended in 6 months. If the lesion of interest was visualized, theMBI-guided biopsy procedure proceeded. The participant’s skin wascleansed with chlorhexidine, then the participant was positioned in lightcompression to stabilize the breast in the MBI camera. A 2- to 2.5-minute imagein the projection in which the biopsy was planned to be approached in the0° position was obtained. Lesion location in the x andy positions within the biopsy grid was confirmed through anoverlay of the biopsy grid pattern on the image acquisition screen (Fig 3). If the position was not optimal,the participant was repositioned, and a repeat 2- to 2.5-minute image wasacquired. The radiologist drew a region of interest, including the lesion and asmall amount of surrounding background, and the software program calculated thelesion center of mass and estimated lesion depth, based on the intensity ofradiotracer activity detected by the two opposing detector heads.
Figure 3:
Images in a 57-year-old woman with suspicious radiotracer uptake atscreening molecular breast imaging (MBI). (A) Prebiopsy MBimage in the mediolateral oblique projection confirms a focal area ofmoderate intensity radiotracer uptake in the upper left breast middledepth (circle). (B) Lateromedial image from a MBI biopsyprocedure shows the region of interest including the area of suspiciousradiotracer uptake and surrounding background (open arrow). The biopsysoftware superimposes the alphanumeric grid and needle guide on theimage (closed arrow). The hole in the needle guide at the site of thebiopsy target is red (red circle).
Next, the upper detector was retracted to a 10°–15° angledposition. An additional 2-minute image was acquired from the upper and lowerdetectors to allow the software to calculate lesion depth by triangulation. Thedisplay showed the biopsy grid location and estimated depth based on the averageof the triangulation and opposing detector head methods; alternatively, theradiologist could select one of the depth calculation methods rather than usingthe average. The upper detector was then moved to the fully retracted positionto allow access to the breast for the biopsy.
A sterile alphanumeric biopsy grid was placed into position on the compressionpaddle. The skin was anesthetized with 1% lidocaine (neutralized 10:1 with 8.4%sodium bicarbonate). The deeper breast tissue was anesthetized using 5–10mL of 1% lidocaine containing 1:100 000 epinephrine along the projectedstylet tract. A small skin incision was made, and the needle guide holder wasplaced into the appropriate location on the alphanumeric biopsy grid. The needleguide, stylet, sheath, and needle were the same system used for MRI-guidedbiopsies (Suros ATEC vacuum-assisted breast biopsy system; Hologic). The styletwas advanced through the needle guide into the breast to the depth calculated bythe software. The stylet was removed and a 9-gauge vacuum-assisted core biopsyneedle was placed through the sheath to acquire samples (Fig 4).
Figure 4:
Picture of molecular breast imaging–guided biopsy from a lateralapproach. A needle guide is positioned within the alphanumeric grid. A9-gauge vacuum-assisted biopsy device is placed through a sheath toobtain samples.
The image acquisition continuously updated the display of the lesion, lesioncenter of mass, overlay of needle guide hole in use, and the total lesionactivity over time, which allowed confirmation of removal of lesion through adecrease in apparent lesion activity. The system was set to alert theradiologist if the center of mass shifted by more than 5 mm during the biopsyprocedure.
Specimen imaging was performed by placing tissue samples in a petri dish andobtaining an image on the retracted upper detector head to document radiotraceruptake within the specimen (Fig 5).Additional samples could be obtained if radiotracer uptake was not present inthe sample. A biopsy clip was placed through the sheath and manual pressure heldfor 10 minutes. A two-view postprocedure mammogram was performed to documentclip placement. Radiology-pathology concordance was assessed by the radiologistwho performed the biopsy.
Figure 5:
Pictures of molecular breast imaging–guided biopsy specimenimaging. (A) Specimens are placed in a petri dish forspecimen imaging. (B) The petri dish (white arrow) isplaced on the retracted upper detector (black arrow), and an image isacquired to assess for radiotracer uptake within the specimen.(C) The petri dish is placed on the detector, and anadhesive dressing (Tegaderm) is used to adhere the petri dish to thedetector. (D) A specimen image from molecular breastimaging–guided biopsy demonstrates radiotracer uptake within thespecimen. Pathology showed fibrocystic changes.
Outcomes
Characteristics of study participants, including age, sex, and BI-RADS categoryof the biopsied lesion, were recorded. The number (percentage) of pathologicdiagnoses from MBI biopsy, concordance of pathology with the imaging findings,biopsy approach, primary method used for depth calculation during the MBI-guidedbiopsy, reasons for procedure cancellation, and procedural complications werealso documented. The following outcomes from the MBI-guided biopsy procedurewere reported as means ± SDs: lesion size, compressed breast thickness,compression force, and procedure time. Statistical significance was not assessedbecause only descriptive outcomes were reported.
Results
Participant Characteristics
Participant characteristics are described in Table 1. Twenty-one participants (mean age, 50.6 years ± 10.1[SD]; 21 [100%] women) were enrolled in the study, and 17 successfully completedMBI-guided biopsy (Fig 1). No adverseeffects from the 99mTc injection were observed in any participant. Infour participants, the lesion was not seen at MBI or had decreased in size andintensity, so no biopsy was performed. No lesions were outside the field ofview. Pathology results for participants who underwent biopsy included invasiveductal carcinoma (n = 1), fibroadenoma (n =4), pseudoangiomatous stromal hyperplasia (n = 6), andfibrocystic changes (n = 6). Of the 17 lesions that werebiopsied, four were assessed as BI-RADS 2 (benign) at preprocedure imaging. Twoof these lesions were previously biopsied with benign pathology showingfibroadenomas; MBI-guided biopsy confirmed the same pathology. Two BI-RADS 2lesions were mammographically stable circ*mscribed masses. MBI-guided biopsyalso showed fibroadenomas in these cases. One biopsied lesion was assessed asBI-RADS 3 (probably benign) at MBI, and 12 lesions were assessed as BI-RADS 4(suspicious for malignancy). All pathology results were diagnostic andconcordant with the imaging. One participant developed a hematoma, whichrequired more than 10 minutes of manual compression but no additional therapy orsurgical intervention. One participant experienced a vasovagal reaction, but thebiopsy was successfully completed after conservative management withTrendelenburg positioning and cold compresses. There were no majorcomplications, defined by the American College of Radiology as a complicationresulting in admission to the hospital for therapy (for outpatient procedures),an unplanned increase in the level of care, prolonged hospitalization, permanentadverse sequelae, or death.
Table 1:
Participant Characteristics
Open in a separate window
MBI-guided Biopsy Procedure Characteristics
The average lesion size, as measured on the MBI report, was 17 mm (range,6–38 mm). Average breast thickness was 59 mm ± 13. The approachfor the biopsy was lateral in 13 participants and craniocaudal in four. Lesiondepth was 22 mm ± 8, and the average compression force was 42 N ±26. Of the two methods for estimation of lesion depth, the method bytriangulation was preferred in all cases. The number of core biopsy samplesobtained with the 9-gauge vacuum-assisted device was six (n =2), eight (n = 4), 10 (n = 8), and 12(n = 3).
The time for each step of the MBI biopsy procedure is shown in Table 2. In five participants, the breastwas repositioned after the initial set of prebiopsy images. Four of the fiveparticipants who were repositioned occurred within the first six participantswho underwent biopsy. Only one participant was repositioned in the subsequent 12participants. The total procedure time was 55 minutes ± 13 (range,38–90 minutes) for all participants. When excluding the five participantswho were repositioned and the one who experienced a vasovagal reaction, thetotal procedure time was 48 minutes ± 8 (range, 38–65 minutes).When excluding prebiopsy imaging, procedure time decreased to 36 minutes± 7 (range, 27–53 minutes).
Table 2:
Time Required for MBI-guided Biopsy
Open in a separate window
Reasons for Canceled MBI-guided Biopsies
In our study, four of 21 participants enrolled did not undergo biopsy due tononvisualization or interval decrease in radiotracer uptake within the lesion.One participant had a finding at PET/CT that was not present on mammography, US,or breast MRI. The finding was also not observed at preprocedural MBI. In twoparticipants with suspicious uptake at MBI, the finding was not reproduced atthe time of the biopsy, so the procedure was canceled. Because the lesionsresolved, these participants were recommended to return to annual screeningmammography. One participant had a negative screening mammogram 1 year after theMBI. The second participant was followed clinically for 1.5 years with no breastcancer diagnosis. Another participant had a probable benign finding at MBI witha more suspicious sonographic correlate. The MBI finding was not well observedat the time of MBI biopsy, so the participant underwent US-guided biopsy;pathology showed pseudoangiomatous stromal hyperplasia, which was concordantwith the imaging findings. An additional participant with a suspicious findingat MBI had marked physiologic background uptake when presenting for biopsy,which obscured the lesion. Follow-up imaging 6 months later showed that thelesion was still present, and MBI biopsy was successfully performed at thattime.
Discussion
To our knowledge, this study represents the first report of a novel MBI-guided coreneedle biopsy technique, which uses a retractable upper detector and two methods oflesion depth measurement. Our results showed that MBI-guided biopsy using thistechnique is feasible and well tolerated by participants with no majorcomplications. The total procedure time for all participants was 55 minutes ±13, which included bilateral preprocedure imaging; this decreased to 36 minutes± 7 when excluding bilateral preprocedure imaging. The addition of MBI-guidedbiopsy may decrease the need for breast MRI to evaluate MBI-detected lesions notobserved at mammography or US and provide streamlined management of suspiciousMBI-detected lesions.
There are multiple advantages to MBI biopsy. Patient positioning is analogous toupright stereotactic biopsies, and the biopsy grid and device are similar toMRI-guided breast biopsy systems, so the procedure is familiar to radiologists whoare accustomed to other breast biopsy techniques. Positioning is comfortable forpatients without potential for claustrophobia, as in breast MRI. Specimen imagingcan be performed during the MBI biopsy procedure, documenting retrieval of thetarget with the ability to take additional samples if focal radiotracer uptake isnot present within the specimen. There are no contraindications to MBI biopsy fromimplanted devices, decreased renal function, or body habitus, improving access tocare for patients who cannot undergo MRI-guided breast biopsy. An intravenousinjection of 99mTc sestamibi is administered, which allows visualizationof the target throughout the procedure without washout of lesions, as can beobserved with breast MRI or contrast-enhanced mammography. Because 99mTcsestamibi remains in the breast tissue for several hours after injection, the biopsyprocedure could potentially be performed as an add-on procedure on the same day as ascreening or diagnostic MBI after an additional dose of 12 mCi 99mTcsestamibi.
99mTc sestamibi has an outstanding safety profile, with adverse eventsoccurring at a rate of one to six events per 100 000 administrations(<0.006%). When reactions occur, they are typically mild in severity, such asflushing, rash, injection site inflammation, or a brief metallic taste (1). This low rate of reactions comparesfavorably to intravenous gadolinium-based agents used for MRI-guided biopsy oriodinated contrast agents used for contrast-enhanced mammography (14). Intravenous gadolinium deposition in thebrain is of uncertain clinical significance, and gadolinium-based contrast agentsalso carry a small risk of reactions (15,16). Iodinated contrast mediahas a risk of mild, moderate, or severe anaphylactoid reactions, with a pooled rateof contrast material reactions for contrast-enhanced mammography reported at 0.82%(15,17).
Prior BSGI and MBI biopsy systems have reported lengthy procedure times, ranging from44 to 112 minutes with a single-head BSGI unit and 90 minutes with a dual-detectorMBI system, which does not include the time to obtain a full set of bilateral MBIimages before the procedure (8,9,18).Although our institution has not previously performed MBI-guided biopsy, and thiswas the first cohort of participants to undergo the procedure with a new biopsysystem, average procedure times were 55 minutes for all participants and 48 minuteswhen excluding those who had a vasovagal reaction or who were repositioned. There isopportunity for further decrease in the procedure time by eliminating the bilateralpreprocedure imaging, which was performed as a part of this research protocol,decreasing the time to 36 minutes ± 7 in our series of participants. Asexpertise develops with the procedure, additional efficiencies would be expectedover time. With procedure times well under an hour, MBI-guided biopsy could beintegrated into the workflow of a breast imaging department.
Cost is an additional important benefit of MBI-guided biopsy. In most health systems,breast MRI and MRI-guided biopsy are the most expensive breast imaging modality,with an average cost of $1000–$3500. Comparatively, the average cost of MBIis approximately $500 nationally (8). In termsof technique and equipment, MBI-guided biopsy is most analogous tostereotactic-guided biopsy, which is about half the cost of MRI-guided biopsy (8). Given the lower cost of MBI-guided biopsy,improved comfort for patients, safety profile of 99mTc sestamibi, andability to perform specimen imaging, there are multiple benefits to MBI-guidedbiopsy.
There are also challenges with the MBI-guided biopsy system described in this study.Like breast MRI or stereotactic-guided biopsies, lesions that are posterior,subareolar, or superficial can be technically challenging or outside the field ofview. When obtaining the 15° view, a posterior lesion may shift outside thefield of view. This shift can be mitigated by performing the depth calculation at alower angle (as low as 10°) or using the opposing view depth calculation. Aprior MBI biopsy system included a “verification rod” of gadolinium153 to document the tip of the rod within the target before proceeding with sampling(8). A verification rod was not includedin the biopsy procedure for this study. This step adds to the overall proceduretime, and further studies will be needed to determine if there is value or need forthis verification step. We believe that the ability to image the biopsy sampleswhile the biopsy needle is still in position in the breast allows for a moredefinitive verification that the appropriate tissue has been sampled. Similar tostereotactic- or tomosynthesis-guided breast biopsy, breasts with a thin compressedthickness may also be technically challenging. However, both standard and petiteneedles can be used with the system.
To facilitate shorter imaging times and visualization of the biopsy target, as in thestudy by Adrada et al (8), we administered ahigher radiotracer dose for MBI-guided biopsy than is routinely used for routineclinical imaging. In addition, we used a noise reduction algorithm that allowed fora further (×2) reduction in the time required for imaging. The 20-mCi doseused in this study equates to a 5-mSv effective dose, which is within the range ofworldwide background radiation levels (2–10 mSv). Models predicting adverseradiation effects in doses less than 100 mSv are highly controversial, with majorscientific physics societies previously stating that the health effects at lowdoses, such as those used in MBI and mammography, are too small to be observed orare nonexistent (19,20). The risks of radiation at the low doses used for MBI arehypothetical and should be taken in the context that the technique represents arelatively inexpensive breast imaging technique (7) with a fast learning curve for radiologists (21) and excellent safety profile that can detectmammographically occult malignancies (4,5), now with a safe and efficient biopsytechnique.
There were several limitations to this study. The Stereo Navigator MBI-biopsyguidance software is currently not FDA approved. The purpose of this study was toevaluate the feasibility of MBI-guided biopsy with a novel system, so only onecancer was diagnosed in this cohort. Furthermore, the study sample included knownbenign lesions and lesions assessed as probably benign, so the pathology is notrepresentative of the distribution expected in a population of patients withsuspicious lesions. Additionally, the rate of canceled biopsies of 19% (four of 21)is higher than the previously reported rate of 11% with BSGI-guided biopsies (18). This rate is attributable to the studyentry criteria, which allowed individuals with probable benign findings or a lesionidentified with any other breast imaging modality without prior MBI to be enrolled.Individuals with lesions assessed as suspicious or highly suggestive of malignancyin a typical biopsy population would be expected to have a lower rate ofcancellation. Future studies should evaluate the rate of MBI biopsy cancellation.MBI is currently less widely available in clinical practice than other breastimaging modalities, but the addition of an efficient biopsy mechanism may encouragepractices to adopt the technique.
In summary, an MBI-guided biopsy system using dual-head MBI was feasible and welltolerated by study participants. All biopsies performed in our study showeddiagnostic and concordant pathology. The ability to biopsy lesions not observed atconventional mammography and US with MBI guidance has the potential to increase theintegration of MBI into clinical practices and improve the care of patients whoundergo MBI. Larger future studies should be performed to validate theseresults.
Acknowledgment
The authors acknowledge the assistance of Sonia Watson, PhD, in preparation of themanuscript.
Supported by funding from the Mayo Foundation.
Data sharing: Data generated or analyzed during the study areavailable from the corresponding author by request.
Disclosures of conflicts of interest: K.N.H. Intellectual property is licensed CMR Naviscan(contractual rights to receive royalties). A.L.C. No relevantrelationships. L.G. No relevant relationships.C.B.H. Support from Mayo Clinic Foundation and NIH R01CA239200;per agreement between Mayo Clinic and CMR Naviscan, author receivesroyalties for licensed technologies; receipt of MBI system withinvestigational biopsy guidance accessory and software. M.K.O.Mayo Clinic and author receive royalties from CMR Naviscan for patentsrelated to the development of the underlying technology used in MBI; patentsrelated to MBI and some of these are licensed to CMR Naviscan by Mayo Clinic(none of the patents are related to the methodology used for MBI-guidedbiopsy); MBI unit used for this biopsy study belongs to CMR Naviscan but hasbeen provided to Mayo for the duration of this study.
Abbreviations:
- BI-RADS
- Breast Imaging Reporting and Data System
- BSGI
- breast-specific gamma imaging
- FDA
- U.S. Food and Drug Administration
- MBI
- molecular breast imaging
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